# Patent

## Title
Electrically driven dump truck

## Abstract

A control device 200 which is formed of a vehicle control device 50, a controller 100, an inverter control device 30 and a steering control device 32 executes control to give a yaw moment to a vehicle 1 so that the vehicle 1 travels while tracing a first trolley wire 3R1/3L1 in a first traveling section before the vehicle 1 reaches a trolley wire linkage section C and the vehicle 1 travels while tracing a second trolley wire 3R2/3L2 in a second traveling section after the vehicle 1 passed through the trolley wire linkage section. In the trolley wire linkage section, a prescribed path is set from a representative point to a second target point and the control device 200 executes control to give a yaw moment to the vehicle 1 so that the vehicle 1 travels along the prescribed path and eventually tracing the second trolley wire 3R2/3L2.

## Background
TECHNICAL FIELD
The present invention relates to an electrically driven dump truck. In particular, to an electrically driven dump truck which travels by using electric power from trolley wires.
BACKGROUND ART
Some types of dump trucks that travel in mines are known as the series hybrid type. Such series hybrid type dump trucks generate electric power with a generator driven by the engine and supply the electric power to rear wheel motors for driving the rear wheels. By taking advantage of the electrical configuration of the series hybrid type, traveling technology based on the trolley system has been implemented. In the trolley-based traveling technology, trolley wires generally employed for electric trains are installed in prescribed climbing sections. In the climbing sections with trolley wires, a vehicle having power collectors (provided on the vehicle to be movable up and down) travels not by using the electric power supplied by the engine and the generator but by using electric power acquired from the trolley wires by elevating sliders of the power collectors to be in contact with the trolley wires (hereinafter referred to as “trolley traveling”). An example of the trolley-based traveling technology has been described in Patent Literature 1, for example. In this case, the drop in the traveling speed in the climbing sections (equipped with the trolley wires enabling the trolley traveling) can be avoided since the electric power supplied from the trolley wires is greater than the electric power generated with the engine power.
PRIOR ART LITERATURE
Patent Literature
Patent Literature 1: U.S. Pat. No. 4,483,148
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
In the trolley-based traveling technology like the one described in the Patent Literature 1, the driver of the vehicle (dump truck) judges whether or not the vehicle has entered a trolley traveling section. When the vehicle has entered a trolley traveling section and the driver viewing the positional relationship between the sliders and the trolley wires judges that the sliders are capable of contacting the trolley wires, the driver operates a switch (e.g., trolley traveling starting button), by which the trolley traveling is started. During the trolley traveling, the driver visually checks the vehicle's displacement with respect to the trolley wires and performs the steering operation so that central positions of the sliders do not deviate widely from the trolley wires in the lateral direction. The timing for ending the trolley traveling is also judged by the driver; the trolley traveling is ended in response to the driver's pressing a button, for example.
Incidentally, to endure a variety of environments, the trolley wires are made of alloy and a length in design (reference length) has been specified for the trolley wires. If the length of the trolley traveling section is the reference length or less, the trolley traveling section can be covered by use of only one trolley wire, and thus the driver is required only to perform the steering operation so as not to deviate from the one trolley wire. However, in cases where the trolley traveling section is longer than the reference length, two or more trolley wires have to be installed in the vehicle's traveling direction in the trolley traveling section. In this case, a linkage section for an already-existing trolley wire (first trolley wire) and a new trolley wire (second trolley wire) occurs. In the linkage section, the terminating end part of the first trolley wire and the beginning end part of the second trolley wire extend in parallel with each other.
In the operation based on the visual check by the driver in cases where such a linkage section is included in the trolley traveling section, the driver is required not only to perform the steering operation so as to simply prevent each slider's central position from widely deviating from the trolley wire in the lateral direction but also to perform the steering operation so that the trolley wire contacting the slider is shifted from the first trolley wire to the second trolley wire. Such steering operation puts a heavy operating load on the driver.
It is therefore the primary object of the present invention to provide an electrically driven dump truck capable of lightening the operating load on the driver during the trolley traveling and realizing stable trolley traveling even when there exists a trolley wire linkage section.
Means for Solving the Problem
To achieve the above object, an invention described in claim 1 provides an electrically driven dump truck which travels on a ground including a first traveling section in which at least one first trolley wire is installed, a second traveling section in which at least one second trolley wire is installed, and a trolley wire linkage section in which a terminating end part of the first trolley wire and a beginning end part of the second trolley wire extend in parallel, by use of electric power received from the first trolley wire and the second trolley wire by elevating a slider of a power collector provided on a vehicle to be movable up and down and making the slider successively contact the first trolley wire and the second trolley wire. The electrically driven dump truck comprises: a trolley wire detecting device which is provided on the vehicle and detects the first trolley wire and the second trolley wire from below when the dump truck is traveling; and a control device which executes first control to give a yaw moment to the vehicle based on relative position information on the electrically driven dump truck and the trolley wire detected by the trolley wire detecting device so that the vehicle travels while tracing the first trolley wire and the second trolley wire in the first traveling section and the second traveling section before and after the trolley wire linkage section. When the vehicle is traveling in the trolley wire linkage section, the control device executes second control to give a yaw moment to the vehicle so that the vehicle travels while tracing a prescribed path extending from the first trolley wire to the second trolley wire.
In the electrically driven dump truck configured as above, each trolley wire (first trolley wire, second trolley wire) is detected from below with the trolley wire detecting device, and thus there are less factors leading to detection errors compared to conventional techniques detecting lane markers, etc. by capturing images of the ground surface. As a result, the accuracy of the trolley wire detection is improved. Thanks to the improvement of the trolley wire detection accuracy, the control accuracy of the control to give a yaw moment to the vehicle so that the vehicle travels while tracing the first trolley wire and the second trolley wire is improved and the central position of the slider of the traveling vehicle hardly deviates widely from the trolley wire in the lateral direction. Consequently, the operating load on the driver during the trolley traveling can be lightened considerably. Further, along with the tracing of the trolley wire (first trolley wire), whether the vehicle is traveling in the trolley wire linkage section or not is detected. In the trolley wire linkage section, the control is executed not to continue the tracing control for tracing the first trolley wire but to make the vehicle travel while tracing a prescribed path extending from the first trolley wire to the second trolley wire. By this control, the vehicle is prevented from continuing tracing the first trolley wire and traveling toward a lane edge. After the trolley wire linkage section, yaw moment control for tracing the new trolley wire (second trolley wire) is carried out. Therefore, the trolley wire contacting the slider is shifted from the first trolley wire to the second trolley wire without the need of careful steering operation by the driver. Consequently, trolley wire tracing control in trolley traveling lanes longer than the reference length of one trolley wire becomes possible.
In an invention described in claim 2, in the electrically driven dump truck according to claim 1, the control device in the first control calculates at least one representative point of the vehicle and at least one first target point situated on the first/second trolley wire based on the relative position information on the electrically driven dump truck and the first/second trolley wire and executes control to give a yaw moment to the vehicle so that the representative point approaches the first target point. The control device in the second control calculates at least one representative point of the vehicle and at least one second target point situated on the second trolley wire based on the relative position information on the electrically driven dump truck and the first/second trolley wire, sets a fluctuating point that shifts from the representative point to the second target point, and executes control to give a yaw moment to the vehicle so that the representative point approaches the fluctuating point.
According to this control, in the trolley wire linkage section, the trolley wire to be traced is shifted from the first trolley wire to the second trolley wire stably based on the status of the vehicle. Further, in the first and second traveling sections, the vehicle is allowed to travel while tracing the trolley wire with high accuracy.
In an invention described in claim 3, the electrically driven dump truck according to claim 1 or 2 further comprises right and left electric motors for traveling. The control device executes both the control to give a yaw moment to the vehicle and traveling speed control by controlling the right and left electric motors.
With this configuration, efficient control, achieving both the deceleration and the generation of the yaw moment at the same time, can be carried out by the control of the electric motors.
In an invention described in claim 4, the electrically driven dump truck according to any one of claims 1-3 further comprises right and left electric motors for traveling and a steering device. The control device includes a vehicle control device, a controller, an inverter control device and a steering control device. The vehicle control device calculates a yaw moment correction value, for the control to give a yaw moment to the vehicle so that the vehicle travels while tracing the trolley wire, based on the information detected by the trolley wire detecting device. The controller controls at least the right and left electric motors or the steering device by using the inverter control device and/or the steering control device based on the yaw moment correction value.
By executing the yaw moment control by using the vehicle control device and the controller as separate components as described above, even when the controller is an already-existing controller, the control in accordance with the present invention can be carried out by just adding the vehicle control device to the controller. The parameters of the yaw moment control can be adjusted just by changing the functions of the vehicle control device. Consequently, high flexibility can be given to the control system.
In an invention described in claim 5, in the electrically driven dump truck according to any one of claims 1-4, the trolley wire detecting device includes: a camera which is provided on the vehicle and continuously captures images of the trolley wire when the dump truck is traveling; and an illuminating device which is provided on the vehicle and illuminates the trolley wire.
Even when a camera is employed for the trolley wire detecting device as above, illuminating the trolley wire with the illuminating device keeps high contrast between the sky and the trolley wire. Consequently, the yaw moment control can be executed with high accuracy not only in the daytime with fine weather but also in conditions in which such high contrast between the sky and the trolley wire is hardly achieved (evening, nighttime, rainy weather, etc.).
Effect of the Invention
According to the present invention, the control accuracy of the control to give a yaw moment to the vehicle so that the vehicle travels while tracing the trolley wire is improved and the central position of the slider of the traveling vehicle hardly deviates widely from the trolley wire in the lateral direction. Consequently, the operating load on the driver during the trolley traveling can be lightened considerably. Further, since the trolley wire contacting the slider is shifted from the first trolley wire to the second trolley wire without the need of careful steering operation by the driver, stable trolley wire tracing control becomes possible even in trolley traveling lanes longer than the reference length of one trolley wire.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side view showing the external appearance of an electrically driven dump truck in accordance with a first embodiment of the present invention.
FIG. 2 is a rear view showing the external appearance of the dump truck.
FIG. 3 is a schematic block diagram showing a drive system of the electrically driven dump truck in this embodiment.
FIG. 4 is a schematic diagram showing the configuration of power collectors for receiving electric power from trolley wires.
FIG. 5 is a schematic diagram showing a steering system which is made up of a steering control device and a steering device.
FIG. 6 is a block diagram showing a function of the steering control device for calculating a steerage torque command value.
FIG. 7 is a block diagram for explaining a function of a vehicle speed control unit of a controller.
FIG. 8 is a block diagram showing the details of a function of a yaw moment control unit of the controller.
FIG. 9 is a graph showing the effect of a method implementing a yaw moment correction value by a driving force difference on the total driving force of the motors when the vehicle is traveling with its 100% motor driving force.
FIG. 10 is a schematic diagram showing an example of a method for calculating motor torque command values.
FIG. 11 is a schematic diagram showing the configuration of a vehicle control device and the input-output relationship between the vehicle control device and the controller.
FIG. 12 is a schematic diagram showing a trolley wire linkage section.
FIG. 13 is a schematic diagram showing the positional relationship between the vehicle and an imaging area of a camera (detecting area of a trolley wire detecting device) viewed from the side of the vehicle.
FIG. 14 is a schematic diagram showing the positional relationship between the vehicle and the imaging area of the camera (the detecting area of the trolley wire detecting device) viewed from above (above the vehicle).
FIG. 15 is a schematic diagram showing an image captured by the camera.
FIG. 16 is a schematic diagram showing a process (edge extraction) performed on the captured image.
FIG. 17 is a schematic diagram showing a process (center line extraction) performed on the captured image.
FIG. 18 is a schematic diagram showing a camera image captured when the vehicle has shifted to the left with respect to the trolley wires.
FIG. 19 is a schematic diagram showing a camera image captured when the vehicle is traveling obliquely to the trolley wires.
FIG. 20 is a block diagram showing the details of a function of a vehicle state quantity control unit (flow of calculation for converting deviation between a present position and a target position into the yaw moment correction value).
FIG. 21 is a flow chart showing a process flow from upward shooting with the camera to control output in an example of the vehicle control device.
FIG. 22 is a schematic diagram showing a trolley wire detecting area and a coordinate system used in another example of the vehicle control device.
FIG. 23 is a schematic diagram showing a trolley wire detecting area and a coordinate system used in another example of the vehicle control device.
FIG. 24 is a block diagram showing the details of a function of another example of the vehicle state quantity control unit (flow of calculation for converting deviation between a present position and a target position into the yaw moment correction value).
FIG. 25 is a schematic diagram showing the movement of a trolley wire, a first target point, a second target point, a fluctuating point and a representative point in a section around a trolley wire linkage section.
FIG. 26 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 27 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 28 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 29 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 30 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 31 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 32 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section.
FIG. 33 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in a state in which the representative point does not coincide with the first target point.
FIG. 34 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 35 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 36 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 37 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 38 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 39 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 40 is a schematic diagram showing the movement of the trolley wire, the first target point, the second target point, the fluctuating point and the representative point in the section around the trolley wire linkage section in the state in which the representative point does not coincide with the first target point.
FIG. 41 is a flow chart showing a process flow from upward shooting with the camera to control output in another example of the vehicle control device.
FIG. 42 is a schematic diagram similar to FIG. 22, showing the trolley wire detecting area and the coordinate system in a case where a first threshold value is set.
FIG. 43 is a schematic diagram showing an example of a method for calculating the yaw moment correction value corresponding to the position of the target point.
FIG. 44 is a schematic diagram similar to FIGS. 22 and 42, showing the trolley wire detecting area and the coordinate system in a case where first and second threshold values are set.
FIG. 45 is a flow chart showing another example of a trolley wire tracing control step in the flow chart of FIG. 41.
FIG. 46 is a schematic diagram showing an example of a method for calculating a target vehicle speed correction value (for correcting the target vehicle speed to the decreasing side) depending on the position of the target point.
FIG. 47 is a schematic diagram showing an example of a method for calculating the target vehicle speed correction value (for correcting the target vehicle speed to the increasing side) depending on the position of the target point.
FIG. 48 is a schematic diagram similar to FIG. 10, showing a method for generating motor torque according to the target vehicle speed correction value.
FIG. 49 is a schematic diagram similar to FIG. 13, showing an example in which the shooting direction of the camera is shifted forward.



MODE FOR CARRYING OUT THE INVENTION
Referring now to the drawings, a description will be given in detail of preferred embodiments in accordance with the present invention.
<Configuration of Vehicle—Dump Truck>
FIG. 1 is a side view showing the external appearance of an electrically driven dump truck in accordance with an embodiment of the present invention.
In FIG. 1, the dump truck comprises a vehicle 1, a vessel 2 for carrying earth, sand, etc., right and left power collectors 4R and 4L for collecting electric power, and right and left rear wheels (tires) 5R and 5L driven by the electric power collected by the power collectors 4R and 4L. The right and left power collectors 4R and 4L are equipped with sliders 4Ra and 4La which are movable up and down to receive the electric power from two (right and left) trolley wires 3R and 3L. One of the trolley wires 3R and 3L is at a high voltage and the other is grounded. In the following explanation, first trolley wires 3R1 and 3L1 and second trolley wires 3R2 and 3L2 can be collectively described as “trolley wires 3R and 3L” as needed for the sake of convenience. The power collectors 4R and 4L are provided on a front part of the vehicle 1. The dump truck is equipped with a trolley wire detecting device 15 mounted on the front part of the vehicle 1. The trolley wire detecting device 15 continuously detects the trolley wires 3R and 3L in front of the dump truck when the dump truck is traveling. The trolley wire detecting device 15 is a device newly mounted on the dump truck according to the present invention. While the trolley wire detecting device 15 is mounted on the front part of the vehicle 1 in the illustrated example, the trolley wire detecting device 15 may also be arranged differently (e.g., on the roof of the vehicle 1).
FIG. 2 is a rear view showing the external appearance of the dump truck. Each rear wheel 5R, 5L is formed as a double-tire wheel to endure the load of earth, sand, etc. loaded on the vessel 2. The right and left double-tire wheels 5R and 5L are driven and braked by right and left electric motors 6R and 6L (e.g., induction motors).
FIG. 3 shows a drive system of the electrically driven dump truck of this embodiment.
In FIG. 3, the drive system of the electrically driven dump truck includes an accelerator pedal 11, a retarder pedal 12, a shift lever 13, a combined sensor 14, an engine 21, an AC generator 22, the other engine load 28, a rectifier circuit 23, a sensing resistor 24, a capacitor 25, a chopper circuit 26, a grid resistor 27, the power collectors 4R and 4L, the rear wheels 5R and 5L, the electric motors 6R and 6L, decelerators 7R and 7L, electromagnetic pickup sensors 16R and 16L, and a control device 200. The combined sensor 14 is used as a yaw rate detecting device for sensing the forward/backward acceleration, the lateral acceleration and the yaw rate. The decelerators 7R and 7L are connected to output shafts 6Ra and 6La of the electric motors 6R and 6L, respectively. Electromagnetic pickup sensors 16R and 16L measure the wheel speeds of the right and left rear wheels, respectively. Similarly to the rear wheels 5R and 5L, right and left front wheels 45R and 45L are equipped with electromagnetic pickup sensors 36R and 36L for measuring their wheel speeds. The right and left front wheel speeds are measured by the electromagnetic pickup sensors 36R and 36L, respectively. Incidentally, the rear wheels 5R and 5L are not suitable for the measurement of the vehicle speed in the strict sense (although there is no problem in most cases) since the rear wheels 5R and 5L are driving wheels and their tires are deformed due to the driving and the braking. Since the front wheels as driven wheels are less affected by the driving/braking, it can be said that vehicle speed calculation by use of the measurements by the electromagnetic pickup sensors 36R and 36L is more precise and gives a value closer to the actual vehicle speed. In cases of controlling the vehicle movement, however, it is sometimes more appropriate to discuss the ground speed of the barycenter of the vehicle 1 (vehicle speed) rather than discussing the front wheel speeds or the rear wheel speeds. Therefore, it is also possible to equip the dump truck with a sensor for directly measuring the ground speed (e.g., ground speed sensor 37) and use the sensor for the measurement of the vehicle speed. Such a sensor can generally be implemented by a millimeter wave radar sensor, an optical sensor, etc.
The control device 200 includes an inverter control device 30, an elevation control device 31, a steering control device 32, a vehicle control device 50 and a controller 100. The inverter control device 30 controls the electric motors 6R and 6L according to torque commands inputted thereto. The elevation control device 31 moves the sliders 4Ra and 4La of the power collectors 4R and 4L up and down according to button operations by the driver or inputs from the outside. The steering control device 32 converts the driver's steering operation into an electric signal and thereby controls the steering of the front wheels. The vehicle control device 50 is a characteristic part of the present invention.
The inverter control device 30 includes a torque command calculation unit 30a, a motor control calculation unit 30b and an inverter (switching element) 30c (publicly-known configuration) for each of the right and left electric motors 6R and 6L. The power collectors 4R and 4L are equipped with elevators which move the sliders 4Ra and 4La up and down according to elevation command signals from the elevation control device 31. The details of the power collectors 4R and 4L, the elevation control device 31, the steering system (including the steering control device 32) and the vehicle control device 50 will be described later.
<Basic Operation Including Traveling>
The depressing level P (the degree of depressing) of the accelerator pedal 11 and the depressing level Q of the retarder pedal 12 are inputted to the controller 100 as signals for controlling the magnitude of the driving force and the retarding force (braking force), respectively. For example, when the driver depresses the accelerator pedal 11 to move the dump truck forward or backward, the controller 100 outputs a command regarding a target revolution speed Nr to the engine 21. The command regarding the target revolution speed Nr is outputted based on a preset table of target revolution speeds Nr corresponding to various accelerator angles. The engine 21 is a diesel engine equipped with an electronic governor 21a. Upon receiving the command regarding the target revolution speed Nr, the electronic governor 21a controls the fuel injection quantity so that the engine 21 revolves at the target revolution speed Nr.
The AC generator 22 is connected to the engine 21 to generate AC power. The electric power generated by the AC power generation is rectified by the rectifier circuit 23 and stored in the capacitor 25 (DC voltage: V). A voltage value detected by the sensing resistor 24 (dividing the DC voltage V at a certain ratio) is fed back to the controller 100. The AC generator 22 is controlled by the controller 100 receiving the feedback so that the voltage value equals a prescribed constant voltage V0.
The electric power generated by the AC generator 22 is supplied to the right and left electric motors 6R and 6L via the inverter control device 30. The controller 100 controls the supply of the necessary electric power to the electric motors 6R and 6L by controlling the AC generator 22 so that the DC voltage V acquired by the rectification by the rectifier circuit 23 equals the prescribed constant voltage V0. In contrast, when the sliders 4Ra and 4La of the power collectors 4R and 4L are in contact with the trolley wires 3R and 3L, the DC voltage V0 is directly supplied from the trolley wires 3R and 3L to the inverter control device 30.
The controller 100 calculates torque command values T_MR_a and T_ML_a corresponding to the operation amounts of the accelerator pedal 11 and the retarder pedal 12 and then generates and outputs torque command values T_MR and T_ML for the right and left electric motors 6R and 6L based on the torque command values T_MR_a and T_ML_a, torque command values T_MR_V and T_ML_V for vehicle speed control, and motor torque correction values T_MR_Y and T_ML_Y for yaw moment control (explained later). The torque command values T_MR and T_ML for the right and left electric motors 6R and 6L and the revolution speeds ωR and ωL of the electric motors 6R and 6L detected by the electromagnetic pickups 16R and 16L are inputted to the inverter control device 30. The inverter control device 30 drives each of the electric motors 6R and 6L via the torque command calculation unit 30a, the motor control calculation unit 30b and the inverter (switching element) 30c. 
The right and left rear wheels (tires) 5R and 5L are connected to the electric motors 6R and 6L via the decelerators 7R and 7L, respectively. Each electromagnetic pickup 16R, 16L is generally implemented by a sensor which detects the peripheral speed of a cog of a gear inside the decelerator 7R, 7L. In the drive system for the right-hand side, for example, it is also possible to attach a gear for the detection to a drive shaft inside the electric motor 6R or to a drive shaft connecting the decelerator 7R to the wheel (tire) 5R and arrange the electromagnetic pickup 16R at the position of the gear.
When the driver of the traveling dump truck returns the accelerator pedal 11 and depresses the retarder pedal 12, the controller 100 executes control so that the AC generator 22 does not generate electric power. Further, the torque command values T_MR_a and T_ML_a from the controller 100 turn negative and thus the inverter control device 30 drives the electric motors 6R and 6L to give braking force to the traveling dump truck. In this case, the electric motors 6R and 6L function as generators so as to electrically charge the capacitor 25 by use of the rectification function of the inverter control device 30. The chopper circuit 26 operates to keep the DC voltage value V within a preset DC voltage value V1 while converting electric energy to thermal energy by feeding electric current to the grid resistor 27.
<Upward/downward Movement of Sliders of Power Collectors>
Next, the elevators for the sliders 4Ra and 4La of the power collectors 4R and 4L will be explained below. FIG. 4 shows the configuration of the power collectors 4R and 4L for receiving the electric power from the trolley wires 3R and 3L. Since the power collectors 4R and 4L are identical with each other in the configuration, the configuration of the power collector 4L will be explained as a representative. The power collector 4L has a hydraulic piston device 4a as the elevator. The housing of the hydraulic piston device 4a is fixed on the vehicle 1. The slider 4La is attached to an end of a rod 4c of a hydraulic piston 4b of the hydraulic piston device 4a. The contact/detachment of the slider 4La to/from the trolley wire 3L is controlled by vertically moving the hydraulic piston 4b with hydraulic fluid supplied from a hydraulic device 4e (including a hydraulic pump) via a hydraulic line 4d. The slider 4La and the rod 4c of the hydraulic piston 4b are electrically insulated from each other by an insulator 4f. The electric power of the trolley wire 3L is supplied to a power supply system of the inverter control device 30 (for driving the motors, see FIG. 3) via the slider 4La and an electric wire 4g. The elevation control device 31 is configured to send the elevation command signal 4h to the hydraulic device 4e according to the driver's operation on an elevation switch or a switching (flag) operation or a control command signal from the outside (e.g., the vehicle control device 50 of the present invention). While the elevator for the slider 4La is implemented by the hydraulic piston device 4a in this embodiment, the elevator may of course be implemented by the system called “pantograph” by use of parallel linkage, spring, motor, etc. as is generally employed for electric trains.
<Steering System>
Next, the steering system will be explained below by referring to FIG. 5.
The steering system is made up of the aforementioned steering control device 32 and a steering device 40. The steering device 40 includes a steering wheel 41, a reaction force motor 42 having a steering angle sensor, a steerage motor 43 having a steerage angle sensor, and a rack-and-pinion gear 44.
When the driver operates the steering wheel 41, the steering angle sensor of the reaction force motor 42 detects the operation amount of the steering wheel 41 and sends the detected operation amount to the steering control device 32. The steering control device 32 sends a torque signal to the steerage motor 43 having the steerage angle sensor so that the present steerage angle equals a steerage angle corresponding to the steering angle of the driver. Front wheels 45R and 45L are turned (steerage) by steerage torque which is generated by the steerage motor 43 and transmitted via the rack-and-pinion gear 44. Depending on the magnitude of this torque, reaction force torque is transmitted to the reaction force motor 42 having the steering angle sensor, by which reaction force is transmitted to the steering wheel 41. At the same time, the steering control device 32 sends the steering angle to the controller 100. The steering control device 32 has a function of receiving a steerage torque correction value from the controller 100 and operating the steerage motor 43 (having the steerage angle sensor) according to the received steerage torque correction value. Whether the steering control device 32 similarly sends the reaction force torque to the reaction force motor 42 having the steering angle sensor or not can be changed properly based on the mode (explained later) at that time and a command from the controller 100. For example, if the steering control device 32 receiving the steerage torque correction value from the controller 100 operates the steerage motor 43 having the steerage angle sensor according to the correction value without sending the reaction force command value to the reaction force motor 42 having the steering angle sensor, the driver loses the steering feeling at that moment even though the vehicle (dump truck) turns according to the steering angle. In contrast, if no command is sent to the steerage motor 43 having the steerage angle sensor even with the steering operation by the driver, the vehicle (dump truck) does not turn in spite of the turning of the steering wheel 41. This means is effective when the controller 100 judges that the steering wheel 41 should not be operated for some reason, for example. As means for informing the driver that the steering wheel 41 should not be operated at the moment, the steering control device 32 may generate torque in a direction opposite to the direction of the driver's steering operation. The torque makes the driver feel that the steering wheel 41 is heavy and recognize that the steering wheel 41 should not be operated in the direction.
While the steer-by-wire system in which the steering wheel 41 is not directly linked to the front wheels 45R and 45L has been explained in this embodiment, the steering system is not limited thereto. For example, an electric power steering system in which the reaction force motor 42 having the steering angle sensor and the steerage motor 43 having the steerage angle sensor are directly connected together as an integral component may also be employed. Further, the steerage motor 43 having the steerage angle sensor may also be implemented by a motor of the hydraulic servo type. Furthermore, the correction value sent from the controller 100 may also be a corrected angle instead of the torque. In this case, the steering control device 32 may be configured to perform torque feedback control so as to eliminate the deviation between the angle detected by the steerage angle sensor and the corrected angle.
FIG. 6 is a block diagram showing a function of the steering control device 32 for calculating a steerage torque command value. A conversion unit 32a of the steering control device 32 converts the driver's steering angle received from the reaction force motor 42 having the steering angle sensor into a driver steerage angle by multiplying the driver's steering angle by a gain factor. A calculation unit 32b subtracts the present steerage angle from the driver steerage angle. A conversion unit 32c converts the subtraction result into driver-requesting steerage torque by multiplying the subtraction result by a gain factor. Then, a calculation unit 32d calculates the steerage torque command value by adding the steerage torque correction value (received from the controller 100) to the driver-requesting steerage torque. The calculated steerage torque command value is outputted to the steerage motor 43 having the steerage angle sensor.
<Vehicle Speed Control>
Referring again to FIG. 3, the controller 100 includes a vehicle speed control unit 101. When a vehicle speed control mode has been selected (ON), the vehicle speed control unit 101 implements the control of the vehicle speed according to the vehicle speed control mode, by executing feedback control to the present vehicle speed with respect to a target vehicle speed that is set in the vehicle speed control mode. FIG. 7 is a block diagram for explaining the function of the vehicle speed control unit 101. As shown in FIG. 7, when the vehicle speed control mode is ON (1), that is, when a switch unit 101c is at its ON position, the vehicle speed control unit 101 receiving the target vehicle speed and the present vehicle speed calculates the difference between the two vehicle speeds with a calculation unit 101a, calculates the torque command values T_MR_V and T_ML_V (for changing the present vehicle speed to the target vehicle speed) with a conversion unit 101b by multiplying the difference by a gain factor, and outputs the calculated torque command values T_MR_V and T_ML_V. The vehicle speed control unit 101 receives revolution speeds ωR and ωL of the electric motors 6R and 6L detected by the electromagnetic pickups 16R and 16L and calculates the vehicle speed from the revolution speeds. The calculation of the vehicle speed may also be performed by using the measurements by the electromagnetic pickups 36R and 36L or the measurement by the ground speed sensor 37 as mentioned above. Thus, a vehicle speed detecting device may be formed by the vehicle speed control unit 101, the electromagnetic pickup sensors 16R and 16L for the rear wheels, the electromagnetic pickup sensors 36R and 36L for the front wheels, and the ground speed sensor 37. A command specifying whether or not to shift to the vehicle speed control mode may be issued according to the driver's operation on a switch of the vehicle control device 50 or according to an input from the outside, for example. The cancellation of the vehicle speed control mode may be made according to the driver's depressing the retarder pedal 12 or according to an input from the outside. When the vehicle speed control mode is canceled, the command of the vehicle speed control mode is turned OFF (0) (i.e., the switch unit 101c is turned OFF) and a vehicle control torque command value 0 is outputted by a zero output unit 101d. The controller 100, having a preset table of engine revolution speed command values corresponding to various torque command values T_MR_V and T_ML_V, outputs an engine revolution speed command value to the engine 21 based on the table.
<Yaw Moment Control>
As shown in FIG. 3, the controller 100 further includes a yaw moment control unit 102 for controlling the turning direction of the vehicle. FIG. 8 is a block diagram showing the details of the function of the yaw moment control unit 102. As shown in FIG. 8, input signals to the yaw moment control unit 102 include, for example, a yaw moment control value which is generated by other yaw moment control (e.g., sideslip prevention control), a yaw moment correction value which is generated according to the present invention, the vehicle speed, the forward/backward acceleration, the lateral acceleration, the yaw rate, the steering angle, and a command of a yaw moment control mode. Output signals from the yaw moment control unit 102 are the steerage torque correction value and the torque correction values T_MR_Y and T_ML_Y for the motors. The yaw moment control value and the yaw moment correction value are added together by a calculation unit 102a to determine a yaw moment command value. The yaw moment command value is inputted to a steering torque control unit 102b, a motor torque control unit 102c and an optimum distribution control unit 102d. The steering torque control unit 102b calculates a steerage torque correction value based on the inputted yaw moment command value. The motor torque control unit 102c calculates motor torque correction values based on the inputted yaw moment command value. The optimum distribution control unit 102d calculates a yaw moment distribution ratio based on the yaw moment command value, the vehicle speed, the yaw rate, the steering angle, the forward/backward acceleration and the lateral acceleration inputted thereto and then calculates a steerage torque correction value and motor torque correction values corresponding to the yaw moment distribution ratio. The command of the yaw moment control mode is inputted to a switch unit 102e. When the yaw moment control mode is mode 1, the switch unit 102e outputs the steerage torque correction value calculated by the steering torque control unit 102b. When the yaw moment control mode is mode 2, the switch unit 102e outputs the motor torque correction value calculated by the motor torque control unit 102c. When the yaw moment control mode is mode 3, the switch unit 102e outputs the steerage torque correction value and the torque correction values for the right and left motors calculated by the optimum distribution control unit 102d. 
<Setting of Yaw Moment Control Mode>
In mines where the dump trucks are traveling, there is an increasing request for the reduction of the time necessary for transporting earth, sand, etc. This is because the reduction of the necessary time shortens the earth/sand transportation cycle of each dump truck and increases the number of times of transportation. The vehicle speed is the major factor directly contributing to the reduction of the necessary time. Therefore, it is desirable to avoid control that causes a decrease in the vehicle speed.
FIG. 9 is a graph showing the effect of a method implementing the yaw moment correction value by a driving force difference on the total driving force of the motors when the vehicle is traveling with its 100% motor driving force. For example, assuming that the vehicle is currently traveling at a constant speed with its 100% driving force as shown on the left side “a” of FIG. 9, the total driving force of the vehicle is in balance with the traveling resistance (air resistance, frictional resistance, slope angle, etc.). In the configuration of this embodiment, the “100% driving force” means the output limits of the rear wheel motors, that is, the maximum value of the driving force that the motors can output at that speed. Let us consider here the method of generating the yaw moment by giving driving/braking force to the vehicle. In this case, the generation of the yaw moment can only be achieved by decreasing the driving force of one of the right and left motors as shown on the right side “b” of FIG. 9 since the motors are already at their output limits as mentioned above. While a yaw moment corresponding to the decrease in the driving force is generated in the vehicle, the vehicle speed drops due to the decrease in the driving force. This goes against the aforementioned request for the time reduction. Therefore, the actuator that should generate the yaw moment in this case is desired to operate in a way not causing a considerable speed drop. Thus, setting the yaw moment control mode to the mode 1 as shown in FIG. 8 is appropriate in this case. In contrast, when the driving force of the vehicle is below 100%, the yaw moment control mode is switched to the motor torque control (yaw moment control mode 2) or the optimum distribution control (yaw moment control mode 3) depending on the magnitude of the driving force and other vehicle state quantities.
<Combining of Motor Torque Generated by Each Unit>
A method for the calculation of the motor torque command values by the controller 100 will be explained referring to FIG. 10. FIG. 10 is a schematic diagram showing an example of the method for calculating the motor torque command values. First, a processing unit 100a selects the aforementioned torque command values T_MR_a and T_ML_a corresponding to the driver's operation on the accelerator/retarder pedals or the torque command values T_MR_V and T_ML_V generated by the vehicle speed control. For example, the processing unit 100a selects the driver's torque command when it exists. Otherwise, the processing unit 100a selects the torque command for the vehicle speed control. Thereafter, a calculation unit 100b calculates motor torque command values T_MR and T_ML by adding the motor torque correction values T_MR_Y and T_ML_Y corresponding to the yaw moment command value generated by the yaw moment control unit 102 respectively to the torque command values selected by the processing unit 100a. This motor torque combining method is just an example; various other methods (e.g. publicly-known methods) may be used.
<Overall Configuration of Characteristic Part>
Next, the overall configuration of the characteristic part of the electrically driven dump truck in accordance with this embodiment will be explained below referring to FIG. 11.
As mentioned above, the drive system of the electrically driven dump truck of this embodiment includes the trolley wire detecting device 15 for detecting the trolley wires 3R and 3L and the vehicle control device 50.
The trolley wire detecting device 15 can be implemented typically by a sensor such as a laser radar, a millimeter wave radar or a camera. In an X-Y plane formed by an X-axis representing the traveling direction of the vehicle (direction of the vehicle axis) and a Y-axis representing the lateral direction (perpendicular to the vehicle axis) of the vehicle, any one of the above sensors serves in the present invention as means for detecting the relative positional relationship between the vehicle and the trolley wires. In the case of the laser radar, scanning (searching for the trolley wires) in the X-axis direction of the vehicle is effective for precisely detecting the trolley wires. In the case of the millimeter wave radar, ill effect of the weather (fog, rain, etc.) is lighter in comparison with other types of sensors. These radar sensors are capable of detection not only in the XY directions but also in the Z direction (height direction of the vehicle and the trolley wires). Therefore, the radar sensors can be suitable in cases where the system of the present invention is used together with a system needing the detection in the height direction.
In the case of the camera, images of the trolley wires are shot from below, and thus the trolley wires can be detected precisely in the daytime with fine weather thanks to high contrast between the sky and the trolley wires. It is also possible to equip the vehicle 1 with an illuminating device 51 for illuminating the trolley wires 3R and 3L. In this case, the illumination of the trolley wires 3R and 3L with the illuminating device 51 keeps high contrast between the sky and the trolley wires, by which the trolley wires can be detected precisely even when such high contrast is hardly achieved (evening, nighttime, rainy weather, etc.).
The system may also be constructed by combining two or more sensors.
FIG. 11 is a schematic diagram showing the configuration of the vehicle control device 50 and the input-output relationship between the vehicle control device 50 and the controller 100. As shown in FIG. 11, the vehicle control device 50 includes a trolley wire detection information processing unit 50a, a vehicle state quantity calculation unit 50b, and a vehicle state quantity control unit 50c. The trolley wire detection information processing unit 50a acquires information on the relative positional relationship between the vehicle and the trolley wires (relative position information) by processing information detected by the trolley wire detecting device 15. The vehicle state quantity calculation unit 50b calculates state quantities of the vehicle based on the information acquired by the trolley wire detection information processing unit 50a. The vehicle state quantity control unit 50c controls the vehicle state quantities based on the result of the calculation by the vehicle state quantity calculation unit 50b. The trolley wires 3R and 3L are supported by supports 53 via insulators 52. The vehicle control device 50 outputs a target speed correction value, the yaw moment correction value, the yaw moment control mode, the elevation control device elevation command, control/detection state information, etc.
In this embodiment, the explanation of the detection of the trolley wires will be given of a case where a camera is used as the trolley wire detecting device 15 and the relative positional relationship between the vehicle and the trolley wires in the X-Y plane is detected by performing image processing. Thus, the trolley wire detecting device 15 is implemented by a camera and the trolley wire detection information processing unit 50a is implemented by an image information processing unit which processes the image information captured by the camera 15.
<Camera 15 and Image Information Processing Unit 50a>
The camera 15 captures images of the trolley wires 3R and 3L. In this case where the two trolley wires 3R and 3L are shot by one camera, the camera 15 is desired to be placed at the center of the right and left trolley wires 3R and 3L. It is also possible to shoot each of the right and left trolley wires 3R and 3L respectively with one camera. The image information captured by the camera 15 is sent to the image information processing unit 50a of the vehicle control device 50. The image information represents pixel arrangement in the area shot by the camera 15. The image information processing unit 50a converts the image information into necessary information.
When a strong light source exists in the shooting direction of the camera 15, a whitening and blurring effect called “halation” can occur to the image inputted to the image information processing unit 50a and this can disable the recognition of the target of detection. As a countermeasure against this problem, it is possible to use two cameras: one for shooting the trolley wires 3R and 3L in front of the vehicle and another for shooting the trolley wires 3R and 3L in back of the vehicle. When the image information processing unit 50a judges that the halation has occurred in an image captured by one camera, a correction can be made by use of the other camera. The halation can be detected according to publicly known methods. The two-camera configuration is effective not only when the halation occurs but also when the visual field of one camera is blocked. When the image information processing unit 50a judges that the visual field of one camera is blocked by dirt, mud, etc., a correction can be made similarly by using the other camera. It is also possible to enclose the camera 15 with a housing, make the camera 15 shoot the trolley wires 3R and 3L through glass of the housing, and wash the glass with a wiper, washer fluid, etc. when the image information processing unit 50a judges that the visibility through the glass has been deteriorated by dirt, mud, etc.
When the image information processing unit 50a judges that the amount of ambient light is insufficient for the detection of the trolley wires 3R and 3L (twilight, darkness, etc.), the image information processing unit 50a may output a blink command to the illuminating device 51 to make the illuminating device 51 illuminate the trolley wires 3R and 3L and maintain high contrast between the sky and the trolley wires.
In this embodiment, a case where the dump truck (vehicle) is traveling in a trolley traveling section like the one shown in FIG. 12 and the camera 15 captures images in the direction directly above the vehicle as shown in FIG. 13 (not in the oblique direction as shown in FIG. 11) will be considered for the simplicity of the explanation. FIG. 12 is a schematic diagram showing an area around a trolley wire linkage section in this embodiment viewed from above. In FIG. 12, the vehicle 1 is traveling from the bottom toward the top of the schematic diagram. The area in front of the vehicle 1 and surrounded by dotted lines represents the imaging area of the camera 15. The solid lines on both sides of the vehicle 1 represent lane edges 54. Among the trolley wires 3R and 3L, the first trolley wires 3R1 and 3L1 form a first traveling section where only the first trolley wires 3R1 and 3L1 are installed, thereafter extend in parallel with new second trolley wires 3R2 and 3L2 for a certain interval in the trolley wire linkage section C, and is finally connected to trolley wire terminating end parts 3R1t and 3L1t. Meanwhile, the second trolley wires 3R2 and 3L2 extend from trolley wire beginning end parts 3R2b and 3L2b in parallel with the first trolley wires 3R1 and 3L1 for a certain interval and thereafter form a second traveling section where only the second trolley wires 3R2 and 3L2 are installed. In this case, the imaging area a, b, c, d of the camera 15 (detecting area of the trolley wire detecting device) is set in front of the vehicle as shown in FIG. 14. FIG. 15 is a schematic diagram showing an image captured by the camera 15 in this case. Since the camera 15 has shot the image of the trolley wires 3R and 3L from below in FIG. 15, the anteroposterior relationship among the points a, b, c and d (positional relationship between the line a-d and the line b-c) and the traveling direction of the vehicle are opposite to those in FIG. 14 in which the trolley wires 3R and 3L are viewed from above.
As shown in FIG. 15, in the image information acquired by the camera 15, the trolley wires 3R and 3L appear in parallel with the traveling direction (in the vertical direction in the image). On this image information, a process for extracting edge parts (edging process) is performed as shown in FIG. 16. By the edging process, the right trolley wire 3R is split into edges RR and RL, while the left trolley wire 3L is split into edges LR and LL. Subsequently, as shown in FIG. 17, a center line of the edges is determined for each of the right and left trolley wires 3R and 3L (a center line RM for the right trolley wire 3R and a center line LM for the left trolley wire 3L). Then, a coordinate system in regard to the pixel number is set with its origin situated at the top center Oc of the image (with its X-axis extending in the direction parallel to the line ab and its Y-axis extending in the direction parallel to the line da). Subsequently, the intersection point P (0, M_Lad_Ref) of the center line LM and the line ad, the intersection point Q (0, M_Rad_Ref) of the center line RM and the line ad, the intersection point R (m, M_Lbc_Ref) of the center line LM and the line bc, and the intersection point S (m, M_Rbc_Ref) of the center line RM and the line bc are set with respect to the origin Oc. These points P, Q, R and S, existing on the trolley wires 3R and 3L, are defined as target points. Incidentally, the number “m” represents the number of pixels in the vertical direction and the number “n” represents the number of pixels in the horizontal direction.
If each trolley wire 3R, 3L is situated at the center of each slider 4Ra, 4La when the vehicle is traveling straight at the center of the two trolley wires 3R and 3L and in parallel with the trolley wires 3R and 3L, this serves as robustness against deviations (displacement) caused by lateral (right/left) misalignment and vibration (jolting) of the vehicle. Therefore, the vehicle is desired to keep on traveling in such a state.
FIG. 18 shows a state in which the vehicle has shifted to the left. By setting representative points of the vehicle 1 at intersection points of lines parallel to the X-axis (i.e., in the traveling direction of the vehicle 1) and passing through the center of the slider 4Ra or 4La and the lines ad and be of the imaging area, the points P′, Q′, R′ and S′ shown in FIG. 18 are acquired as the representative points. These representative points are points used for control for controlling the position of the vehicle with respect to the trolley wires 3R and 3L. Therefore, the representative points P′, Q′, R′ and S′ can also be referred to as control points. Coordinates of these representative points are defined as M_Lad_Cont, M_Rad_Cont, M_Lbc_Cont and M_Rbc_Cont, respectively.
FIG. 19 shows a case where the vehicle is traveling obliquely to the trolley wires 3R and 3L. Also in this case, the representative points of the vehicle are defined as the points P′, Q′, R′ and S′.
Further, whether new trolley wires (the second trolley wires 3R2 and 3L2) other than the currently detected trolley wires (the first trolley wires 3R1 and 3L1) are detected in the imaging area a, b, c, d or not is judged.
The image information processing unit 50a sends the coordinate information on the target points and the representative points and information representing whether the second trolley wires 3R2 and 3L2 have been detected or not to the vehicle state quantity calculation unit 50b. 
<Vehicle State Quantity Calculation Unit 50b>
The vehicle state quantity calculation unit 50b in this embodiment calculates deviations between the representative points P′, Q′, R′ and S′ and the target points P, Q, R and S. The deviations e_Lad, e_Rad, e_Lbc and e_Rbc between the representative points and the target points are calculated as follows:

e_Lad=M_Lad_Ref−M_Lad_Cont  (1)

e_Rad=M_Rad_Ref−M_Rad_Cont  (2)

e_Lbc=M_Lbc_Ref−M_Lbc_Cont  (3)

e_Rbc=M_Rbc_Ref−M_Rbc_Cont  (4)

These deviations take on positive/negative values when the vehicle has shifted leftward/rightward with respect to the trolley wires.
The displacement (deviation) is defined similarly also when the vehicle is traveling obliquely to the trolley wires 3R and 3L as shown in FIG. 19. In this case, the inclination eθ_L of the vehicle with respect to the left trolley wire 3L and the inclination eθ_R of the vehicle with respect to the right trolley wire 3R can be calculated as follows:

eθ—L=(e_Lbc−e_Lad)/m  (5)

eθ—R=(e_Rbc−e_Rad)/m  (6)

When the camera is successfully detecting the right and left trolley wires 3R and 3L as in this embodiment, the expressions (2), (4) and (6) are redundant to the expressions (1), (3) and (5). Therefore, it is desirable to perform the calculation by using information on a successful side (on which the displacement and the inclination can be calculated successfully) when the calculation of the displacement and the inclination is impossible on one side for some reason.
Further, based on the information from the image information processing unit 50a regarding the detection of the first trolley wires 3R1 and 3L1 and the second trolley wires 3R2 and 3L2, the vehicle state quantity calculation unit 50b figures out whether the vehicle 1 is traveling in the trolley wire linkage section C or not. Incidentally, the trolley wire linkage section C is the section where the terminating end parts 3R1t and 3L1t of the first trolley wires 3R1 and 3L1 and the beginning end parts 3R2b and 3L2b of the second trolley wires 3R2 and 3L2 extend in parallel.
When it is figured out that the vehicle 1 is traveling in the trolley wire linkage section C, the vehicle state quantity calculation unit 50b sets the target points (second target points) for the newly detected second trolley wires 3R2 and 3L2. Further, the vehicle state quantity calculation unit 50b sets prescribed paths from the representative points to the second target points. The prescribed paths may be set as straight lines, curved lines, etc. connecting the representative points to the second target points. It is preferable to set the prescribed paths so that the paths shift so as to reach the second target points within the trolley wire linkage section. The first target points, which have been set for the already-existing first trolley wires 3R1 and 3L1, may either be deleted or left as they are.
Furthermore, based on the information from the image information processing unit 50a, the vehicle state quantity calculation unit 50b sets a linkage mode flag to “1” when the second trolley wires 3R2 and 3L2 are detected, and to “0” when a representative point (explained later) coincides with the second target point.
<Vehicle State Quantity Control Unit 50c>
Next, the vehicle state quantity control unit 50c will be explained below. The vehicle state quantity control unit 50c in this embodiment calculates the yaw moment correction value for making at least one of the representative points coincide with the corresponding target point. First, a process for generating the yaw moment correction value by multiplying the displacement and the inclination represented by the expressions (1)-(6) by gain factors is shown in FIG. 20. FIG. 20 is a block diagram showing the details of the function of the vehicle state quantity control unit 50c. In this example, the point P or Q is used as the target point and the point P′ or Q′ is used as the representative point.
As shown in FIG. 20, a calculation unit 50c1 of the vehicle state quantity control unit 50c determines the deviation e_Lad (e_Rad) between the representative point P′ (Q′ ) and the target point P (Q) by calculating the difference between the coordinate value M_Lad_Cont (M_Rad_Cont) of the representative point P′ (Q′ ) and the coordinate value M_Lad_Ref (M_Rad_Ref) of the target point P (Q) inputted from the vehicle state quantity calculation unit 50b. A conversion unit 50c2 of the vehicle state quantity control unit 50c converts the deviation e_Lad (e_Rad) into a yaw moment value by multiplying the deviation by a gain factor. Meanwhile, a conversion unit 50c3 converts the inclination eθ_L (eθ_R) of the vehicle inputted from the vehicle state quantity calculation unit 50b into a yaw moment value by multiplying the inclination by a gain factor. A calculation unit 50c4 calculates the yaw moment correction value by adding the two yaw moment values together and outputs the calculated yaw moment correction value to the yaw moment control unit 102.
Incidentally, when the second target points have been set, the vehicle state quantity control unit 50c stops the calculation of the yaw moment correction value for making the representative point(s) coincide with the first target point(s) and carries out calculation of yaw moment correction value for making the representative point(s) coincide with the second target point(s).
The vehicle state quantity control unit 50c also determines the yaw moment control mode which has been explained referring to FIG. 8. The aforementioned yaw moment control unit 102 of the controller 100 calculates the motor torque command values and the steerage torque correction value based on the yaw moment correction value and the yaw moment control mode determined by the vehicle state quantity control unit 50c and then outputs the motor torque command values and the steerage torque correction value to the inverter control device 30 and the steering control device 32, respectively.
With the configuration and operation described above, the control device 200 (made up of the vehicle control device 50, the controller 100, the inverter control device 30 and the steering control device 32) executes control to give an appropriate yaw moment to the vehicle 1 so that the vehicle 1 travels while tracing the first trolley wires 3R1 and 3L1 in the first traveling section before the vehicle 1 reaches the trolley wire linkage section C, or while tracing the second trolley wires 3R2 and 3L2 in the second traveling section after the vehicle 1 passed through the trolley wire linkage section (first control). In the trolley wire linkage section, the control device 200 sets the prescribed path(s) from the representative point(s) to the second target point(s) and executes control to give an appropriate yaw moment to the vehicle 1 so that the vehicle 1 traces the prescribed path(s) and thereby eventually travels tracing the second trolley wires 3R2 and 3L2 (second control). Further, the control device carries out control to give an appropriate yaw moment to the vehicle 1 so that the inclination eθ_L (eθ_R) decreases.
Besides the simple gain control shown in FIG. 20, integral control, derivative control, etc. may also be employed.
<Details of Control Process by Vehicle Control Device 50>
The details of the above control process executed by the vehicle control device 50 will be explained below referring to a flow chart of FIG. 21. FIG. 21 is a flow chart showing the flow of the process from the upward shooting with the camera to the control output.
In the first step 200, the image information processing unit 50a captures an image upward from the vehicle 1 with the camera. In step 201, the image information processing unit 50a searches the captured image for the trolley wire 3R or 3L. In the search in the step 201, the whole area of the captured image is searched when the detection of the trolley wire 3R/3L is carried out for the first time. After the trolley wire 3R/3L has been detected once, searching the whole area is unnecessary; searching only a limited area in the vicinity of the coordinates of the already detected trolley wire 3R/3L is effective since it leads to reduction of the search time. In step 202, the image information processing unit 50a judges whether or not there exists an object corresponding to the trolley wire 3R/3L in the captured image. If no object corresponding to the trolley wire 3R/3L is found, the process is finished. If there exists an object corresponding to the trolley wire 3R/3L, the process advances to step 203A. In the step 203A, the image information processing unit 50a executes the edge extraction and the image processing for calculating the center line of the trolley wire 3R/3L.
The process is thereafter handed over to the vehicle state quantity calculation unit 50b. In step 203B, the vehicle state quantity calculation unit 50b sets the aforementioned target points (T and U) and calculates the coordinates of the target points T and U. Thereafter, the process using the coordinate information on the target points T and U shifts to a trolley wire linkage control and tracing control step 500 for tracing the trolley wire 3R/3L.
<Trolley Wire Linkage Control and Tracing Control>
At the start of the trolley wire linkage control and tracing control step 500, whether the linkage mode flag which is set by the vehicle state quantity calculation unit 50b is “0” (not in a linkage mode (explained later)) or not is judged (step 510). If Yes (the linkage mode flag is “0”, not in the linkage mode), the process advances to step 520. If No (the linkage mode flag is “1”, in the linkage mode), the process advances to step 550.
In the step 520, whether an object corresponding to a new trolley wire (the second trolley wire 3R2/3L2), other than the first trolley wire 3R1/3L1 (included in the collectively called “trolley wire 3R/3L”), is detected in the imaging area a, b, c, d or not is judged.
When a new trolley wire is detected in the step 520, this means that the vehicle 1 is traveling in the trolley wire linkage section C. In this case, if the vehicle 1 continues traveling while tracing the already-existing first trolley wire 3R1/3L1, the vehicle 1 is guided to the terminating end part 3R1t/3L1t of the first trolley wire 3R1/3L1 and runs off the lane edge 54. To avoid this problem, the process advances to step 530 and the linkage mode flag is set to “1”. Then, the process advances to step 540 and new target points (second target points) are generated on the second trolley wire 3R2/3L2. Thereafter, the process advances to the step 550.
When no new trolley wire 3R2/3L2 is detected in the step 520, the process advances to step 320 so as to continue the tracing control for tracing the first trolley wire 3R1/3L1.
In the next step 550, the representative point is shifted so that it coincides with the second target point. Various methods can be employed for the shifting of the representative point; the prescribed path may be formed properly in consideration of the kinematic characteristics of the vehicle, the loading status of the vehicle, the vehicle speed, etc. For example, the speed of the shifting of the representative point may be set around a speed at which the representative point can shift from the first trolley wire to the second trolley wire in a period in which the first and second trolley wires are in parallel with each other. The shifting of the representative point may be performed according to a linear function, a quadratic function, etc. It is also possible to rapidly shift the representative point from the first trolley wire to the second trolley wire. When viewed from an absolute coordinate system, linear shifting from the first trolley wire to the second trolley wire may be employed as shown in FIG. 12. In this case, the vehicle is necessitated to deviate from the current straight path (on which the vehicle has traveled) upon each linkage of trolley wires. However, thanks to the above control, the vehicle is allowed to continuously travel through the first traveling section (in which the vehicle travels while tracing the already-existing first trolley wire), the trolley wire linkage section, and the second traveling section (in which the vehicle travels while tracing the new second trolley wire) substantially straight (along the broken line in the linkage section). Shocks in the lateral direction at times of shifting are mild and that can be considered to be effective for increasing the traveling efficiency and preventing a load shift/collapse.
Step 560 will be explained next. In the step 560, whether the representative point already coincides with the second target point or not is judged. If the representative point coincides with the second target point, the process advances to step 570 to set the linkage mode flag to 0 and thereafter advances to the step 320, by which the shifting from the first trolley wire 3R1/3L1 to the second trolley wire 3R2/3L2 is completed. In contrast, if the representative point does not coincide with the second target point (NO), this means that the vehicle is in the middle of the shifting from the first trolley wire 3R1/3L1 to the second trolley wire 3R2/3L2, and thus the process directly advances to the step 320.
In the step 320, the vehicle state quantity control unit 50c calculates and outputs the yaw moment correction value. As long as the representative point exists in the vehicle's traveling direction and the vehicle travels in the direction, the extension line of the vehicle axis of the vehicle 1 eventually passes through the second target point, which allows the vehicle to trace the second trolley wire 3R2/3L2.
In the next step 330, the yaw moment control mode is selected and outputted. In normal traveling, the mode “1” is selected as the yaw moment control mode since there is no request for reducing the vehicle speed (driver's retarder operation or deceleration by other control).
<Effect>
According to this embodiment configured as above, the following effects are achieved: Since the trolley wires 3R and 3L are detected from below in this embodiment, there are less factors leading to detection errors compared to the conventional technique detecting lane markers, etc. by capturing images of the ground surface. As a result, the accuracy of the trolley wire detection is improved. Thanks to the improvement of the trolley wire detection accuracy, the control accuracy of the yaw moment control for making the vehicle travel while tracing the trolley wires 3R and 3L is improved and the central position of each slider 4Ra/4La of the traveling vehicle hardly deviates widely from the trolley wire 3R/3L in the lateral direction. Consequently, stable trolley traveling is made possible and the operating load on the driver in the trolley traveling section can be lightened considerably.
Further, before reaching the trolley wire linkage section C, the vehicle traces the already-existing trolley wire (first trolley wire 3R1/3L1) (first control) while also judging whether the vehicle 1 is traveling in the trolley wire linkage section C or not based on whether a new trolley wire (second trolley wire 3R2/3L2) other than the already-existing trolley wire is detected or not. When the vehicle is traveling in the trolley wire linkage section C, the yaw moment control for tracing the prescribed path extending to the second target point on the newly detected trolley wire (second trolley wire 3R2/3L2) is carried out (second control). After the vehicle has passed through the trolley wire linkage section C and entered the second traveling section, the yaw moment control for tracing the second trolley wire 3R2/3L2 (first control) is carried out. With the above control, the vehicle is prevented from continuing tracing the first trolley wire 3R1/3L1 and traveling toward the lane edge 54, and the trolley wire contacting the slider is automatically shifted from the first trolley wire 3R1/3L1 to the second trolley wire 3R2/3L2 without the need of careful steering operation by the driver. Consequently, stable trolley traveling becomes possible even in cases where the length of the trolley traveling section is greater than the reference length of one trolley wire.
In the case where a camera 15 is used as the trolley wire detecting device, illuminating the trolley wires 3R and 3L with the illuminating device 51 is effective for maintaining high contrast between the sky and the trolley wires 3R and 3L. By use of the illuminating device 51, the yaw moment control for making the vehicle travel while tracing the trolley wires 3R and 3L can be executed with high accuracy not only in the daytime with fine weather but also in conditions in which such high contrast between the sky and the trolley wires 3R and 3L is hardly achieved (evening, nighttime, rainy weather, etc.).
Furthermore, the control device 200 is capable of executing the yaw moment control by using the vehicle control device 50 and the controller 100 as separate components. With this configuration, even when the controller 100 is an already-existing controller, the yaw moment control in accordance with the present invention can be carried out by just adding the vehicle control device 50 to the controller. The parameters of the yaw moment control can be adjusted just by changing the functions of the vehicle control device 50. Consequently, high flexibility can be given to the control system.
<Another Embodiment of Vehicle Control Device 50>
Next, another embodiment of the vehicle control device 50 will be described below.
The main difference between this embodiment and the above embodiment is as follows: In the above embodiment, the control is executed simply for giving an appropriate yaw moment to the vehicle 1 to make the vehicle travel while tracing the first trolley wire 3R1/3L1 or the second trolley wire 3R2/3L2 when the vehicle is traveling in the first traveling section or the second traveling section, and for giving an appropriate yaw moment to the vehicle 1 to make the vehicle travel while tracing the prescribed path (extending to the second trolley wire 3R2/3L2) in the trolley wire linkage section C (hereinafter referred to as “trolley wire linkage control and tracing control” as needed). In this embodiment, elevation control of the slider 4Ra or 4La of the power collector 4R/4L (hereinafter referred to as “slider elevation control” as needed) is executed in addition to the trolley wire linkage control and tracing control. Further, in the traveling in the first traveling section and the second traveling section, a dead zone is set in regard to the deviation between the representative point and the target point. The yaw moment control for tracing the trolley wire is carried out only when the deviation has exceeded the dead zone.
<Image Information Processing Unit 50a>
The processing by the image information processing unit 50a is identical with that in the above embodiment. The image information processing unit 50a sends the coordinate information on the representative points P′, Q′, R′ and S′ and the information on whether the second trolley wires 3R2 and 3L2 have been detected or not to the vehicle state quantity calculation unit 50b. 
<Vehicle State Quantity Calculation Unit 50b and Vehicle State Quantity Control Unit 50c>
The vehicle state quantity calculation unit 50b is a component for calculating state quantities to be used for generating control values and command values such as the yaw moment correction value for the trolley wire linkage control and tracing control, the elevation control device elevation command for the elevation control of the slider 4Ra or 4La of the power collectors 4R and 4L, the yaw moment control mode, the target speed correction value, and the linkage mode flag. The vehicle state quantity control unit 50c is a component for generating and outputting the control values and the command values (the yaw moment correction values, the elevation control device elevation command, the yaw moment control mode, the target speed correction value, etc.) based on the result of the calculation by the vehicle state quantity calculation unit 50b. 
<Trolley Wire Detecting Area and Coordinate System>
First, a trolley wire detecting area and a coordinate system used by the vehicle state quantity calculation unit 50b will be explained below.
FIG. 22 is a schematic diagram showing the trolley wire detecting area and the coordinate system used in this embodiment.
Based on the image information on the imaging area a, b, c, d (see FIGS. 17-19) acquired by the image information processing unit 50a from the camera 15, the vehicle state quantity calculation unit 50b extracts and acquires an area like the area a1, b1, c1, d1 shown in FIG. 22 as the trolley wire detecting area. The side a1-d1 corresponds to a part of the side a-d of the imaging area a, b, c, d shown in FIGS. 17-19, while the side b1-c1 corresponds to a part of the side b-c of the imaging area a, b, c, d. The trolley wire detecting area a1, b1, c1, d1 indicates the positional relationship between the slider 4Ra or 4La and the trolley wire 3R1 or 3L1 or the trolley wire 3R2 or 3L2 when the trolley wire 3R1/3L1 or 3R2/3L2 is viewed from above. In the trolley wire detecting area a1, b1, c1, d1, a straight line passing through the center of the slider 4Ra/4La (regarding the lateral direction) and extending in the traveling direction of the vehicle passes through the center of the side a1-d1 and the center of the side b1-c1. As mentioned above, since the trolley wire 3R1/3L1 or 3R2/3L2 is shot from below in the image information on the imaging area a, b, c, d acquired by the camera 15, the anteroposterior relationship (vertical direction in FIG. 22) in the trolley wire detecting area a1, b1, c1, d1 (viewing the trolley wire 3R1/3L1 or 3R2/3L2 from above) is opposite to that in the imaging area a, b, c, d.
Further, the vehicle state quantity calculation unit 50b sets a coordinate system having the origin (Op) at the center of the slider 4Ra/4La, the X-axis extending in the traveling direction, and the Y-axis extending leftward with respect to the traveling direction. In the coordinate system, the vehicle state quantity calculation unit 50b sets a representative point at the intersection point Z of the X-axis and the side b1-c1, and sets two target points T and U at the intersection point T of the side b1-c1 and the trolley wire 3R1/3L1 or 3R2/3L2 and at the intersection point U of the side a1-d1 and the trolley wire 3R1/3L1 or 3R2/3L2. Since the camera 15 and the slider 4Ra/4La of the power collector 4R/4L are both attached to the vehicle and the positional relationship between the two components are already known, the coordinates of the intersection points Z, T and U can be determined with ease by means of coordinate transformation, by transforming coordinate values of the points P′, P and R in the coordinate system with the origin Oc shown in FIGS. 17-19 into coordinate values in the coordinate system with the origin Op shown in FIG. 22.
Further, based on the detection information on the second trolley wire 3R2/3L2 supplied from the image information processing unit 50a, the vehicle state quantity calculation unit 50b figures out whether the vehicle 1 is traveling in the trolley wire linkage section C or not. When the vehicle 1 is judged to be traveling in the trolley wire linkage section C, the second target points are set on the newly detected second trolley wire 3R2/3L2 and then the prescribed path is set from the representative point to the (corresponding) second target point. Furthermore, the vehicle state quantity calculation unit 50b sets the linkage mode flag to “1” when the second trolley wire 3R2/3L2 is detected, and to “0” when the representative point coincides with the second target point.
<Trolley Wire Linkage Control and Tracing Control>
The vehicle state quantity calculation unit 50b and the vehicle state quantity control unit 50c carry out the trolley wire linkage control and tracing control. In the trolley wire linkage control and tracing control in this embodiment, when the vehicle is judged to be traveling in the trolley wire linkage section C, a fluctuating point indicated with the reference character “F” in FIG. 23 is set and the yaw moment control is executed so that the representative point Z coincides with the fluctuating point F.
When the vehicle is traveling in the trolley wire linkage section C, the vehicle state quantity calculation unit 50b sets the fluctuating point F and executes control so that the fluctuating point F shifts from the representative point Z to the second target point T2 (second control). In contrast, in the first traveling section and the second traveling section before and after the trolley wire linkage section, the vehicle state quantity calculation unit 50b does not set the fluctuating point F and executes control to give an appropriate yaw moment to the vehicle 1 so that the representative point Z approaches the target point T (first target point T1) (first control). The details of the first control in this embodiment are substantially equivalent to those in the above embodiment, and thus repeated explanation thereof is omitted here.
The vehicle state quantity calculation unit 50b calculates the deviation between the representative point Z and the fluctuating point F. Since the Y-coordinate value (Y_c) of the fluctuating point F equals the deviation between the representative point Z and the fluctuating point F, the vehicle state quantity calculation unit 50b regards the Y-coordinate value Y_c of the fluctuating point F as the deviation between the representative point Z and the fluctuating point F. The deviation Y_c takes on a positive/negative value when the vehicle has shifted rightward/leftward with respect to the fluctuating point F.
The vehicle state quantity control unit 50c calculates the yaw moment correction value (for making the representative point Z coincide with the fluctuating point F) by using the deviation Y_c between the representative point Z and the fluctuating point F. In this case, the yaw moment correction value can be calculated as below.

yaw moment correction value=gain×Y—c  (7)

In other words, the representative point Z is moved according to the expression (7) so that it coincides with the fluctuating point F. FIG. 24 is a block diagram showing this process. A conversion unit 50c4 converts the deviation Y_c into the yaw moment correction value by multiplying the deviation Y_c by a gain factor. The yaw moment correction value is outputted to the yaw moment control unit 102 and a yaw moment is given to the vehicle. The vehicle state quantity control unit 50c continues outputting the yaw moment correction value as long as the representative point Z does not coincide with the fluctuating point F.
Since the fluctuating point F is set as above and the yaw moment is given to the vehicle 1 so that the representative point Z coincides with the fluctuating point F, the yaw moment control in the trolley wire linkage section is carried out so that the representative point Z coincides with the second target point T2. Consequently, the vehicle travels to gradually approach the second trolley wire, and eventually traces the second trolley wire.
While details of the setting of the fluctuating point F are not particularly restricted, it is desirable to take into consideration the kinematic characteristics of the vehicle, the loading status of the vehicle, the vehicle speed, etc. A gradual shift toward the second target point T2 is especially desirable in order to prevent sharp change of the representative point Z and the fluctuating point F.
FIGS. 25-32 show the shift of the representative point Z from the first target point T1 on the first trolley wire to the second target point T2 on the second trolley wire when the vehicle is traveling in a section around the trolley wire linkage section.
FIG. 25 shows a state in which the vehicle is tracing the first trolley wire 3R1/3L1. In this state, the first target point T1 on the first trolley wire 3R1/3L1 and the representative point Z are overlapping at the same point, that is, the representative point Z is coinciding with the first target point T1 in order to trace the first trolley wire 3R1/3L1. Since the representative point Z and the first target point T1 coincide with each other in FIG. 25, no yaw moment is given to the vehicle 1. Consequently, the vehicle travels straight forward (right under the first trolley wires 3R1 and 3L1).
As the vehicle continues traveling straight, the second trolley wire 3R2/3L2 starts being detected in the imaging area as shown in FIG. 26. However, the setting of the fluctuating point F and the second target point T2 on the second trolley wire 3R2/3L2 is not made yet since the second trolley wire 3R2/3L2 has not appeared enough at the stage of FIG. 26.
Thereafter, when the second trolley wire 3R2/3L2 has appeared clearly in the imaging area and the second trolley wire 3R2/3L2 starts changing into a straight line as shown in FIG. 27, the second trolley wire is judged to have been detected and the vehicle is judged to be traveling in the trolley wire linkage section. At this point, the fluctuating point F and the second target point T2 on the second trolley wire 3R2/3L2 are set and the setting is made so that the fluctuating point F shifts to coincide with the second target point T2.
When the fluctuating point F starts shifting to coincide with the second target point T2 as shown in FIG. 28, a deviation occurs between the fluctuating point F and the representative point Z. A yaw moment is given to the vehicle 1 so as to reduce the deviation. Accordingly, the representative point Z moves to gradually coincide with the fluctuating point F as shown in FIG. 29 and the vehicle undergoes the yaw moment control so as to trace the second trolley wire 3R2/3L2.
The shifting of the fluctuating point F ends when the fluctuating point F overlaps with the second target point T2 as shown in FIG. 30. Meanwhile, the deviation between the fluctuating point F and the representative point Z is still remaining, and thus the yaw moment control is continued so that the representative point Z coincides with the fluctuating point F. Via the state shown in FIG. 31, the three points (the second target point T2, the fluctuating point F and the representative point Z) coincide together as shown in FIG. 32. At this point, the procedure for the trolley wire linkage section C is completed.
Incidentally, in cases where the vehicle reaches the trolley wire linkage section C before the representative point Z and the first target point T1 coincide with each other in the first traveling section (a case where a traveling distance sufficient for letting the representative point coincide with the first target point could not be secured due to shortness of the first traveling section, an accidental case, etc.), the procedure for the trolley wire linkage section C proceeds as shown in FIGS. 33-40.
Specifically, the representative point Z in FIG. 33 is shifted rightward with respect to the first target point T1 on the first trolley wire 3R1/3L1. In this state in which the representative point Z and the first target point T1 do not coincide with each other, the yaw moment is being given to the vehicle 1.
Thereafter, the second trolley wire 3R2/3L2 starts being detected in the imaging area. However, the setting of the second target point T2 and the fluctuating point F is not made yet at the stage of FIG. 34.
Thereafter, when the second trolley wire 3R2/3L2 has appeared clearly in the imaging area and the second trolley wire 3R2/3L2 starts changing into a straight line as shown in FIG. 35, the second target point T2 is calculated on the second trolley wire 3R2/3L2, the fluctuating point F is set to shift from the representative point Z to the second target point T2, and the control for making the fluctuating point F shift to coincide with the second target point T2 is started.
The fluctuating point F starts shifting to coincide with the second target point T2 as shown in FIG. 36. The representative point Z moves to gradually coincide with the fluctuating point F as shown in FIGS. 37 and 38.
The shifting of the fluctuating point F ends when the fluctuating point F overlaps with the second target point T2 as shown in FIG. 39. Meanwhile, the deviation between the fluctuating point F and the representative point Z is still remaining, and thus the yaw moment control is continued so that the representative point Z coincides with the fluctuating point F. When the three points (the second target point T2, the fluctuating point F and the representative point Z) coincide together as shown in FIG. 40, the procedure for the trolley wire linkage section C is completed.
As above, even in the case where the vehicle has reached the trolley wire linkage section C before the representative point Z and the first target point T1 coincide with each other in the first traveling section, it is possible to control the vehicle 1 to make it trace the second trolley wire, by setting the fluctuating point F which shifts from the representative point Z to the second target point T2 on the second trolley wire 3R2/3L2 and executing the control to give the yaw moment to the vehicle so that the representative point Z approaches the fluctuating point F as in this embodiment. Therefore, in the trolley wire linkage section C, carrying out the control to make the fluctuating point F and the representative point Z coincide with each other is important rather than considering the position of the already-existing first trolley wire (first target point). In other words, it is important to set a new target point T other than the first target point (i.e., the second target point on the second trolley wire) on the second trolley wire 3R2/3L2 and execute the control to make the fluctuating point coincide with the new target point T. With this control, the trolley wire contacting each slider is automatically shifted from the first trolley wire to the second trolley wire, and stable trolley wire tracing control can be carried out even on a trolley traveling lane that is longer than the reference length of one trolley wire.
The other functions of the vehicle state quantity control unit 50c related to the trolley wire tracing control are equivalent to those in the above embodiment.
<Slider Elevation Control>
The vehicle state quantity calculation unit 50b calculates the inclination θ_t of the vehicle at a certain time t. The inclination θ_t of the vehicle with respect to the trolley wire 3R1/3L1 or 3R2/3L2 at a certain time t is represented by the following expression by using the coordinate values of the two target points T and U in a coordinate system like the one shown in FIG. 22:

θ—t=(Y—Cbc−Y—Cad)/(X—Cbc−X—Cad)  (8)

The vehicle state quantity calculation unit 50b also calculates the Y-coordinate (Y_p_t) of a point W which is defined as the intersection point of the slider 4Ra/4La and the trolley wire 3R1/3L1 or 3R2/3L2.
The Y-coordinate Y_p_t of the point W can be approximated as follows:

Y—p—t=Y_Cbc−θ—t×X_Cbc or

Y—p—t=Y_Cad−θ—t×X_Cad  (9)

Here, Y_P_t+1 as the value of Y_p_t one step later (after a time interval Δ) is expressed by using the vehicle speed V as follows:

Y—p—t+1=Y—p—t+V×tan θ—t  (10)

Assuming that the permissible range of the Y-coordinate Y_p_t of the point W on the slider 4Ra/4La, within which the slider 4Ra/4La is in contact with the trolley wire 3R1/3L1 or 3R2/3L2 and satisfactory electric power can be acquired continuously, is Y_min (Y-coordinate of a point D)<Y_p_t<Y_max (Y-coordinate of a point C) between points C and D, it can be said that there is no problem with elevating the slider 4Ra/4La in a range satisfying Y_min<Y_p_t+1<Y_max.
At the present time t, the vehicle state quantity calculation unit 50b judges whether or not the Y-coordinate Y_p_t of the point W will be outside the range between Y_min (Y-coordinate of the point D) and Y_max (Y-coordinate of the point C) in the next control step t+1, and outputs the result of the judgment to the vehicle state quantity control unit 50c. If the Y-coordinate Y_p_t of the point W will be outside the range between Y_min (Y-coordinate of the point D) and Y_max (Y-coordinate of the point C), the vehicle state quantity control unit 50c outputs a command signal for lowering the sliders 4Ra and 4La or prohibiting the elevation of the sliders 4Ra and 4La. In contrast, if the Y-coordinate Y_p_t will be within the range, the vehicle state quantity control unit 50c outputs a command signal for elevating the sliders 4Ra and 4La or permitting the elevation of the sliders 4Ra and 4La. The vehicle state quantity control unit 50c may also correct the reaction force of the reaction force motor 42 (see FIG. 5) of the steering device 40 depending on the Y-coordinate Y_p_t of the point W. For example, the correction may be made to decrease the reaction force in the range satisfying Y_min<Y_p_t+1<Y_max and to increase the reaction force in the ranges satisfying Y_p_t+1≦Y_min or Y_max≦Y_p_t+1.
As above, the vehicle control device 50 is executing both the trolley wire linkage control and tracing control and the slider elevation control. In the trolley wire linkage control and tracing control, when the vehicle is traveling in the first traveling section or the second traveling section, the vehicle state quantity control unit 50c outputs the yaw moment correction value calculated by multiplying the deviation Y_Cbc or the inclination θ_t by a gain factor so that the vehicle traces the first trolley wire 3R1/3L1 or the second trolley wire 3R2/3L2 (first control). Since the outputting of the yaw moment correction value continues until the deviation Y_Cbc or the inclination θ_t becomes 0, the Y-coordinate Y_p_t of the point W on the slider 4Ra/4La and the inclination θ_t of the vehicle eventually converge on 0 and the vehicle tends to travel while tracing the first trolley wire 3R1/3L1 or the second trolley wire 3R2/3L2.
In the trolley wire linkage section C, the control of calculating the second target point T2 on the second trolley wire 3R2/3L2, setting the fluctuating point F which shifts from the representative point Z to the second target point T2, and giving the yaw moment to the vehicle 1 so that the representative point Z approaches the fluctuating point F (second control) is carried out. Therefore, the yaw moment correction value for reducing the deviation Y_Cbc or the inclination θ_t to 0 is outputted and the vehicle eventually traces the second trolley wire 3R2/3L2 in a similar manner.
<Details of Control Process in Another Embodiment of Vehicle Control Device 50>
Details of a control process in another embodiment of the above-described vehicle control device 50 will be explained below referring to a flow chart of FIG. 41. FIG. 41 is a flow chart showing the flow of the process from the upward shooting with the camera to the control output. It is assumed as shown in FIG. 13 that the camera is set in front of the vehicle 1 to be on the extension line of the vehicle axis and the number of trolley wires shot with the camera is one as shown in FIG. 12. FIG. 42 is a schematic diagram similar to FIG. 22, wherein a dead zone of the trolley wire tracing control has been set. The target points T and U and the representative point Z have been set for the detecting area a1, b1, c1, d1 as explained above. Further, points A and B specifying the dead zone of the trolley wire tracing control have been set at positions a prescribed distance Y_l, Y_r (first threshold value) apart from the representative point Z.
The steps 200-203B in FIG. 42 are equivalent to those in the detailed control process flow shown in FIG. 21. After the step 203B, the process advances to a trolley wire linkage control and tracing control step 500′ for tracing the trolley wires 3R and 3L.
<Trolley Wire Linkage Control and Tracing Control>
At the start of the trolley wire linkage control and tracing control step 500′, whether the linkage mode flag which is set by the vehicle state quantity calculation unit 50b is “0” or not is judged (step 510). If Yes, the process advances to the step 520. If No, the process advances to step 550′.
In the step 520, whether an object corresponding to the second trolley wire 3R2/3L2, other than the first trolley wire 3R1/3L1 (included in the collectively called “trolley wire 3R/3L”), is detected in the imaging area a, b, c, d or not is judged. When the second trolley wire 3R2/3L2 is detected in the step 520, the process advances to the step 530 and the linkage mode flag is set to “1”. Then, the process advances to step 540′ and the second target point T2 is generated on the second trolley wire 3R2/3L2, while also generating the fluctuating point F which shifts from the representative point Z to the second target point T2. Thereafter, the process advances to the step 550′. When the second trolley wire 3R2/3L2 is not detected in the step 520, the process advances to step 310.
In the step 550′, the fluctuating point F is shifted so that it coincides with the second target point T2. The shifting of the fluctuating point F may be carried out similarly to the above embodiment.
In the next step 560′, whether the representative point Z coincides with the second target point T2 or not is judged. If the representative point Z coincides with the second target point T2, the process advances to step 570′, in which the linkage mode flag is set to 0 and the fluctuating point F is deleted. Thereafter, the process advances to the step 310. In contrast, if the representative point Z does not coincide with the second target point T2 (No), the process advances to the step 320 since the shifting from the first trolley wire 3R1/3L1 to the second trolley wire 3R2/3L2 is in progress.
In the step 310, the vehicle state quantity calculation unit 50b judges whether or not the target point T (T1) exists between the points A and B (Y_l≦Y_Cbc, Y_r≧Y_Cbc) which have been set at positions a prescribed distance apart (Y_l, Y_r) from the representative point Z shown in FIG. 42.
When the target point T does not exist between the points A and B in the step 310 or when the judgment in the step 560′ is “No”, the process advances to the step 320 and the vehicle state quantity control unit 50c calculates and outputs the yaw moment correction value.
The calculation of the yaw moment correction value in the case where the process has advanced from the step 560′ is performed as follows: In this case, the shifting of the fluctuating point F to make it coincide with the second target point T2 in the step 550′ causes a difference between the coordinates of the fluctuating point F and the representative point Z, and thus the calculation is performed according to the expression 7, for example, so as to eliminate the difference. As long as the representative point Z exists in the vehicle's traveling direction and the vehicle travels in the direction, the extension line of the axis of the vehicle 1 eventually passes through the second target point T2, which allows the vehicle to trace the second trolley wire 3R2/3L2.
FIG. 43 shows an example of a method for the calculation of the yaw moment correction value in the step 320 in the case where the target point T does not exist between the points A and B in the step 310. In FIG. 43, the gradient of the characteristic lines outside the points A and B corresponds to the gain of the conversion unit 50c2 shown in FIG. 24. As shown in FIG. 43, a yaw moment correction value corresponding to the Y-coordinate value Y_Cbc of the target point T (corresponding to the deviation between the representative point Z and the target point T) is calculated outside the points A and B. Specifically, in the range outside the point A (where Y_Cbc is positive), the yaw moment correction value is increased with the increase in Y_Cbc. In the range outside the point B (where Y_Cbc is negative), the yaw moment correction value is decreased with the decrease in Y_Cbc. According to this calculation, when the target point T does not exist between the points A and B (i.e., when the absolute value of the deviation Y_Cbc between the representative point Z and the target point T is greater than the absolute value of the Y-coordinate value Y_l of the point A or the Y-coordinate value Y_r of the point B as the first threshold value), control is executed to give an appropriate yaw moment to the vehicle 1 so as to make the representative point Z approach the target point T. Further, the control is executed so that the yaw moment given to the vehicle 1 increases with the increase in the absolute value of the deviation Y_Cbc. After the yaw moment correction value has reached a maximum correction value or a minimum correction value, the yaw moment correction value is set constant in order to prevent abrupt/extreme turning of the vehicle. Incidentally, it is also possible to output a constant yaw moment correction value in such cases where the target point T does not exist between the points A and B, instead of calculating and outputting the yaw moment correction value as a variable.
Here, the reason for setting the yaw moment correction value at 0 between the points A and B shown in FIG. 43 will be explained. By the control for making the representative point Z coincide with the target point T, the point W is positioned almost at the center of the slider 4Ra/4La as long as the vehicle 1 is traveling forward. In this case, however, the yaw moment correction value is calculated even when the point W has slightly shifted from the center of the slider 4Ra/4La and that increases the frequency of operation of the actuators implementing the yaw moment correction (the reaction force motor 42 and the steerage motor 43 of the steering device 40 (FIG. 5) and the rear wheel electric motors 6R and 6L (FIG. 3) in this embodiment). By setting the yaw moment correction value at 0 between the points A and B, the frequency of operation of the rear wheel electric motors 6R and 6L can be reduced and high control stability and riding comfort can be secured. The width of the range between the points A and B (in which the yaw moment correction is unnecessary) may be set depending on the width of the slider 4Ra/4La.
Further, by executing the control so as to increase the yaw moment given to the vehicle 1 with the increase in the absolute value of the deviation Y_Cbc, the vehicle 1 is given the yaw moment so that trolley wires 3R and 3L quickly return to the center of the sliders 4Ra and 4La when the slider 4Ra/4La of the traveling vehicle is about to widely deviate from the trolley wire 3R/3L in the lateral direction. Consequently, the dump truck can securely be prevented from deviating from the lane with the trolley wires 3R and 3L.
In the next step 330, the yaw moment control mode is selected and outputted. In normal traveling, the mode “1” is selected as the yaw moment control mode since there is no request for reducing the vehicle speed (driver's retarder operation or deceleration by other control).
<Another Example of Trolley Wire Tracing Control in Trolley Wire Linkage Control and Tracing Control>
Next, another example of the trolley wire tracing control in the trolley wire linkage control and tracing control will be explained below referring to FIGS. 44-48. FIG. 44 is a schematic diagram similar to FIGS. 22 and 42, wherein deviation monitoring points for the trolley wire tracing control have been set. FIG. 45 is a flow chart showing step 500′′ which is executed instead of the trolley wire linkage control and tracing control step 500′ in the flow chart of FIG. 41.
As shown in FIG. 44, a point A′ (second threshold value) at a position outside (with a larger Y-coordinate value than) the point A and with a Y-coordinate value Y_l′ and a point B′ (second threshold value) at a position outside (with a smaller negative Y-coordinate value than) the point B and with a Y-coordinate value Y_r′ have been set as the deviation monitoring points for the trolley wire tracing control.
In FIG. 45, the process from the start to the step 320 (calculation of the yaw moment correction value) via the steps 510-570 is identical with that in FIG. 33 which has been explained above. In step 321 after the step 320, whether the target point T is situated between the points A′ and B′ (Y_l′≦Y_Cbc, Y_r′≧Y_Cbc) or not is judged. If affirmative, a warning for urging the driver to correct the steering is issued by sound and/or display (step 322) since there is a possibility that the vehicle deviates from the trolley lane.
In the next step 323, the target vehicle speed is corrected depending on the position of the target point T. FIG. 46 is a schematic diagram showing an example of a method for calculating a target vehicle speed correction value in this case. As shown in FIG. 46, when the target point T does not exist between the points A′ and B′, the target vehicle speed correction value is calculated so as to reduce the target vehicle speed depending on the degree of deviation from the points A′ and B′. Specifically, in the range outside the point A′ (where Y_Cbc is positive), the correction value on the side of decreasing the target vehicle speed is increased with the increase in Y_Cbc. In the range outside the point B′ (where Y_Cbc is negative), the correction value on the side of decreasing the target vehicle speed is decreased with the decrease in Y_Cbc. According to this calculation, when the target point T does not exist between the points A′ and B′ (i.e., when the absolute value of the deviation Y_Cbc between the representative point Z and the target point T is greater than the absolute value of the Y-coordinate value Y_l′ of the point A′ or the absolute value of the Y-coordinate value Y_r′ of the point B′ as the second threshold value), control is executed to decrease the traveling speed with the increase in the absolute value of the deviation Y_Cbc. Decreasing the vehicle speed as above is effective for lightening the operating load on the driver and giving a feeling of security to the driver.
FIG. 47 is a schematic diagram showing another example of the method for calculating the target vehicle speed correction value. As shown in FIG. 47, when the target point T exists between the points A′ and B′, the correction may be made to increase the target vehicle speed as target point T approaches the representative point Z. Specifically, in the range inside the point A′ (where Y_Cbc is positive), the correction value on the side of increasing the target vehicle speed is increased with the decrease in Y_Cbc. In the range inside the point B′ (where Y_Cbc is negative), the correction value on the side of increasing the target vehicle speed is decreased with the increase in Y_Cbc. According to this calculation, when the target point T exists between the points A′ and B′ (i.e., when the absolute value of the deviation Y_Cbc between the representative point Z and the target point T is less than the absolute value of the Y-coordinate value Y_l′ of the point A′ or the Y-coordinate value Y_r′ of the point B′ as the second threshold value), control is executed to increase the traveling speed with the decrease in the absolute value of the deviation Y_Cbc. Increasing the vehicle speed as above is effective for increasing the working efficiency.
FIG. 48 is a schematic diagram similar to FIG. 10, showing a method for generating motor torque according to the target vehicle speed correction value. As shown in FIG. 48, the target vehicle speed correction value calculated as above is converted into a motor torque correction value by a conversion unit 100c by multiplying the target vehicle speed correction value by a gain factor. Subsequently, the motor torque command values T_MR and T_ML are calculated by a calculation unit 100d by adding the motor torque correction value (corresponding to the target vehicle speed correction value) calculated by the conversion unit 100c to the motor torque command values calculated by the calculation unit 100b (acquired by adding the motor torque correction values T_MR_Y and T_ML_Y corresponding to the yaw moment command value generated by the yaw moment control unit 102 (FIG. 8) to the torque command values selected by the processing unit 100a).
Next, the yaw moment control mode in the case where the target vehicle speed is corrected to a lower value according to the target vehicle speed correction value shown in FIG. 46 will be explained. As shown in FIG. 9, in cases where a yaw moment has to be generated when the right and left motors are outputting 100% motor torque, it is necessary to reduce the motor torque of one of the right and left motors. The reduction of the motor torque of one of the motors leads to a drop in the vehicle speed since the vehicle cannot maintain the present speed with the reduced motor torque. Thus, in cases where the target vehicle speed is corrected to a lower value, the yaw moment correction may be made not by the steerage torque correction but by the correction of the motor torque, by which both the control to give a yaw moment to the vehicle 1 by controlling the right and left electric motors 6R and 6L and the control of the traveling speed are carried out. Consequently, efficient control, achieving both the deceleration and the generation of the yaw moment at the same time, can be carried out.
<Other Examples>
In the explanation of the above embodiments, the fluctuating point is set only in the period in which the vehicle is traveling in the trolley wire linkage section C, and the control for making the representative point coincide with the fluctuating point is executed only in the period. However, specific modes of the trolley wire linkage control and tracing control for making the vehicle travel while tracing the first and second trolley wires are not restricted to such examples.
For example, the fluctuating point may be set constantly, even outside the trolley wire linkage section. In this case, in the first and second traveling sections, the setting is made assuming that the representative point Z is moving on the fluctuating point F, and the control is carried out to make the representative point Z coincide with the target point T. In the trolley wire linkage section, the control of calculating the second target point T2 situated on the second trolley wire, setting the fluctuating point F so that it shifts from the representative point Z to the second target point T2, and giving the yaw moment to the vehicle so that the representative point Z approaches the fluctuating point F is carried out as explained above.
Further, while the outputting of the yaw moment for making the vehicle trace the trolley wire 3L1, 3L2, 3R1, 3R2 is continued during the traveling in the first and second traveling sections in the above explanation, the control may also be executed so as to perform the calculation of the yaw moment correction value (for making the vehicle trace the trolley wires) and the yaw moment control only in one or more prescribed traveling sections (e.g., sections before and after the trolley wire linkage section) included in the first and second traveling sections.
Furthermore, while the camera used as the trolley wire detecting device is pointed directly upward in the above explanation, the camera may also be set to capture images in a forward and upward direction from the vehicle as shown in FIG. 49. Such camera setting facilitates the detection/recognition of the trolley wires as the target of the tracing since the parts of the trolley wires shot with the camera in the vehicle's traveling direction are long. On the other hand, noise caused by the scenery included in the imaging area increases as the imaging area is shifted forward. Therefore, the imaging area of the camera may be adjusted properly depending on the environment in which the present invention is employed.
DESCRIPTION OF REFERENCE CHARACTERS


    1 vehicle
    2 vessel
    3L, 3R trolley wire
    3L1, 3R1 first trolley wire
    3L1t, 3R1t first trolley wire terminating end part
    3L2, 3R2 second trolley wire
    3L2b, 3R2b second trolley wire beginning end part
    4L, 4R power collector
    4La, 4Ra slider
    4a hydraulic piston device
    4b hydraulic piston
    4c rod
    4d hydraulic line
    4e hydraulic device
    4f insulator
    4g electric wire
    4h elevation command signal
    5L, 5R rear wheel
    6L, 6R electric motor
    6La, 6Ra output shaft
    7L, 7R decelerator
    11 accelerator pedal
    12 retarder pedal
    13 shift lever
    14 combined sensor
    15 camera
    16L, 16R electromagnetic pickup sensor for rear wheel
    21 engine
    21a electronic governor
    22 AC generator
    23 rectifier circuit
    24 sensing resistor
    25 capacitor
    26 chopper circuit
    27 grid resistor
    28 other engine load
    30 inverter control device
    30a torque command calculation unit
    30b motor control calculation unit
    30c inverter (switching element)
    31 elevation control device
    32 steering control device
    32a conversion unit
    32b calculation unit
    32c conversion unit
    32d calculation unit
    36L, 36R electromagnetic pickup sensor for front wheel
    37 ground speed sensor
    40 steering device
    41 steering wheel
    42 reaction force motor having a steering angle sensor
    43 steerage motor having a steerage angle sensor
    44 rack-and-pinion gear
    45L, 45R front wheel
    50 vehicle control device
    50a image information processing unit
    50b vehicle state quantity calculation unit
    50c vehicle state quantity control unit
    50c1 calculation unit
    50c2 conversion unit
    50c3 conversion unit
    50c4 calculation unit
    51 illuminating device
    52 insulator
    53 support
    54 lane edge
    100 controller
    100a processing unit
    100b calculation unit
    101 vehicle speed control unit
    101a calculation unit
    101b conversion unit
    101c switch unit
    101d zero output unit
    102 yaw moment control unit
    102a calculation unit
    102b steering torque control unit
    102c motor torque control unit
    102d optimum distribution control unit
    102e switch unit
    200 control device
    C trolley wire linkage section
    P, Q, R, S target point
    P′, Q′, R′, S′ representative point
    T target point
    T1 first target point
    T2 second target point
    Z representative point (control point)
    F fluctuating point
    e_Lad deviation
    θ_L inclination
    Y_Cbc deviation
    θ_t inclination
    Y_l, Y_r Y-coordinate value of point A, B (first threshold value)
    Y_l′, Y_r′ Y-coordinate value of point A′, B′ (second threshold value)

## Claims

1. An electrically driven dump truck which travels on a ground including a first traveling section in which at least one first trolley wire (3R1, 3L1) is installed, a second traveling section in which at least one second trolley wire (3R2, 3L2) is installed, and a trolley wire linkage section (C) in which a terminating end part (3R1t, 3L1t) of the first trolley wire and a beginning end part (3R2b, 3L2b) of the second trolley wire extend in parallel, by use of electric power received from the first trolley wire and the second trolley wire by elevating a slider (4Ra, 4La) of a power collector (4R, 4L) provided on a vehicle (1) to be movable up and down and making the slider (4Ra, 4La) successively contact the first trolley wire and the second trolley wire, the electrically driven dump truck comprising:
a trolley wire detecting device (15) which is provided on the vehicle and detects the first trolley wire and the second trolley wire from below when the dump truck is traveling; and
a control device (200) which executes first control to calculate at least one representative point of the vehicle and at least one first target point situated on the first/second trolley wire based on the relative position information on the electrically driven dump truck and the first/second trolley wire and executes control to give a yaw moment to the vehicle in such a manner that the representative point approaches the first target point based on relative position information on the electrically driven dump truck and the first /second trolley wire detected by the trolley wire detecting device in such a manner that the vehicle travels while tracing the first trolley wire and the second trolley wire in the first traveling section and the second traveling section before and after the trolley wire linkage section,
wherein when the vehicle is traveling in the trolley wire linkage section, the control device executes second control to calculate at least one representative point of the vehicle and at least one second target point situated on the second trolley wire, to set a fluctuating point that shifts from the representative point to the second target point and to give a yaw moment to the vehicle in such a manner that the representative point approaches the fluctuating point in such a manner that the vehicle travels while tracing a prescribed path extending from the first trolley wire to the second trolley wire.

2. The electrically driven dump truck according to claim 1, further comprising right and left electric motors (6R, 6L) for traveling,
wherein the control device executes both the control to give a yaw moment to the vehicle and traveling speed control by controlling the right and left electric motors.

3. The electrically driven dump truck according to claim 1, further comprising right and left electric motors (6R, 6L) for traveling and a steering device (40), wherein:
the control device includes a vehicle control device (50), a controller (100), an inverter control device (30) and a steering control device (32), and
the vehicle control device calculates a yaw moment correction value, for the control to give a yaw moment to the vehicle in such a manner that the vehicle travels while tracing the trolley wire, based on the information detected by the trolley wire detecting device, and
the controller controls at least the right and left electric motors or the steering device by using the inverter control device and/or the steering control device based on the yaw moment correction value.

4. The electrically driven dump truck according to claim 1, wherein the trolley wire detecting device includes:
a camera (15) which is provided on the vehicle and continuously captures images of the trolley wire when the dump truck is traveling; and
an illuminating device (51) which is provided on the vehicle and illuminates the trolley wire.

5. The electrically driven dump truck according to claim 2, wherein the trolley wire detecting device includes:
a camera (15) which is provided on the vehicle and continuously captures images of the trolley wire when the dump truck is traveling; and
an illuminating device (51) which is provided on the vehicle and illuminates the trolley wire.

6. The electrically driven dump truck according to claim 3, wherein the trolley wire detecting device includes:
a camera (15) which is provided on the vehicle and continuously captures images of the trolley wire when the dump truck is traveling; and
an illuminating device (51) which is provided on the vehicle and illuminates the trolley wire.