Patent Description:
An engine-type industrial vehicle disclosed in International Publication No. <CIT> includes a sensor that detects an object, a controller, and an engine. The engine-type industrial vehicle travels by the driving force of the engine. The controller performs control so that the engine-type industrial vehicle stops, when the sensor detects that an object exists within a setting range. The setting range is the longest distance that the engine-type industrial vehicle travels until the engine-type industrial vehicle stops. <CIT> relates to a method for monitoring of a movement of a vehicle comprising determining an expected movement path and determining a risk of collision. <CIT> relates to a method for increasing safety in an environment of a commercial vehicle comprising an imaging sensor system. <CIT> relates to systems and methods to detect and warn proximate entities of interest.

In the engine-type industrial vehicle disclosed in International Publication No. <CIT>, when an object exists within the setting range, the controller performs control so that the engine-type industrial vehicle stops. It is desired that the engine-type industrial vehicle avoids contact with the object in a more suitable manner.

The present invention, which has been made in light of the above-mentioned problem, is directed to providing a.

In accordance with an aspect of the present invention, there is provided an engine-type industrial vehicle according to claim <NUM>.

Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.

The disclosure, together with objects and advantages thereof, may best be understood by reference to the following description of the embodiments together with the accompanying drawings in which:.

One embodiment of an engine-type industrial vehicle will be described below.

As illustrated in <FIG>, a forklift <NUM> serving as the engine-type industrial vehicle includes a vehicle body <NUM>, two driving wheels <NUM> and <NUM>, two steered wheels <NUM>, and a load handling apparatus <NUM>.

The vehicle body <NUM> includes a head guard <NUM> provided above a driver's seat. In the description below, terms of "front", "back/rear", "left", and "right" indicate the front, back/rear, left, and right of the forklift <NUM>.

The driving wheels <NUM> and <NUM> are disposed in a lower front portion of the vehicle body <NUM>. The two driving wheels <NUM> and <NUM> are spaced apart from each other in the vehicle width direction.

The two steered wheels <NUM> are disposed in a lower rear portion of the vehicle body <NUM>. The two steered wheels <NUM> are spaced apart from each other in the vehicle width direction.

The load handling apparatus <NUM> includes a mast <NUM>, a pair of forks <NUM>, and lift cylinders <NUM>. The mast <NUM> is provided on a front portion of the vehicle body <NUM>. The forks <NUM> are liftable and lowerable together with the mast <NUM>. A load is loaded on the forks <NUM>. The lift cylinders <NUM> are hydraulic cylinders. The mast <NUM> is lifted and lowered by the extension and contraction of the lift cylinders <NUM>. The forks <NUM> are lifted and lowered with the lifting and lowering of the mast <NUM>. In this embodiment, the traveling motion and the load handling motion of the forklift <NUM> are performed in response to operations by an operator.

As illustrated in <FIG>, the forklift <NUM> includes a main controller <NUM>, an accelerator pedal <NUM>, an accelerator sensor <NUM>, a direction lever <NUM>, a direction sensor <NUM>, a wheel angle sensor <NUM>, a lifting height sensor <NUM>, a weight sensor <NUM>, a traveling system <NUM>, a load handling system <NUM>, an object detector <NUM>, and a bus <NUM>.

The main controller <NUM> includes a processor <NUM> and a storage unit <NUM>. As the processor <NUM>, for example, a central processing unit (CPU), a graphics processing unit (GPU), or a digital signal processor (DSP) is used. The storage unit <NUM> includes a random access memory (RAM) and a read only memory (ROM). The storage unit <NUM> stores a program used to operate the forklift <NUM>. Specifically, the storage unit <NUM> stores program codes or commands so as to cause the processor <NUM> to execute processing. The storage unit <NUM>, i.e., a computer readable medium, includes any available media accessible by a general-purpose or dedicated computer. The main controller <NUM> may include hardware circuits, such as an application specific integrated circuit (ASIC) and a field programmable gate array (FPGA). The main controller <NUM>, which is a processing circuit, may include one or more processors that operate in accordance with a computer program, one or more hardware circuits, such as the ASIC and the FPGA, or a combination thereof.

The accelerator sensor <NUM> detects the operation amount of the accelerator pedal <NUM>. In other words, the operation amount of the accelerator pedal <NUM> is an accelerator opening degree (i.e., a position of the accelerator). The accelerator sensor <NUM> outputs an electrical signal according to the accelerator opening degree to the main controller <NUM>. The main controller <NUM> recognizes the accelerator opening degree by the electrical signal from the accelerator sensor <NUM>.

The direction sensor <NUM> detects the operation direction of the direction lever <NUM>. The direction lever <NUM> is operated by the operator to give an instruction on the traveling direction of the vehicle body <NUM>. In other words, the traveling direction of the vehicle body <NUM> is the traveling direction of the forklift <NUM>. The direction sensor <NUM> detects whether the operation direction of the direction lever <NUM> has instructed the forklift <NUM> to move forward or move backward, with reference to neutral as the standard. The direction sensor <NUM> outputs an electrical signal according to the operation direction of the direction lever <NUM> to the main controller <NUM>. The main controller <NUM> recognizes the operation direction of the direction lever <NUM> by the electrical signal from the direction sensor <NUM>. Accordingly, the main controller <NUM> grasps whether the operator has instructed the forklift <NUM> to move forward, move backward, or neither.

The wheel angle sensor <NUM> detects the steering angles of the steered wheels <NUM>. The wheel angle sensor <NUM> outputs an electrical signal according to the steering angles to the main controller <NUM>. The main controller <NUM> recognizes the steering angles by the electrical signal from the wheel angle sensor <NUM>.

The lifting height sensor <NUM> detects the lifting height of the load handling apparatus <NUM>. The lifting height of the load handling apparatus <NUM> is the height from a road surface to the forks <NUM>. The lifting height sensor <NUM> is a reel sensor, for example. The lifting height sensor <NUM> outputs an electrical signal according to the lifting height to the main controller <NUM>. The main controller <NUM> recognizes the lifting height of the load handling apparatus <NUM> by the electrical signal from the lifting height sensor <NUM>.

The weight sensor <NUM> detects the weight of the load loaded on the load handling apparatus <NUM>. The weight sensor <NUM> is a pressure sensor that detects the oil pressure of the lift cylinders <NUM>, for example. The weight sensor <NUM> outputs an electrical signal according to the weight of the load to the main controller <NUM>. The main controller <NUM> recognizes the weight of the load by the electrical signal from the weight sensor <NUM>.

The traveling system <NUM> is a mechanism configured to move the vehicle body <NUM>. The traveling system <NUM> includes an engine <NUM>, an output shaft <NUM>, a rotational speed sensor <NUM>, a power transmission <NUM>, a differential apparatus <NUM>, an axle <NUM>, a vehicle speed sensor <NUM>, and a travel controller <NUM>.

The engine <NUM> is a driving source of the traveling motion and the load handling motion of the forklift <NUM>. The engine <NUM> of this embodiment is a gasoline-fueled engine. The engine <NUM> includes a throttle actuator <NUM>. The throttle actuator <NUM> adjusts the throttle opening degree. The adjustment of the throttle opening degree by the throttle actuator <NUM> adjusts the amount of air supplied to the engine <NUM>. As a result, the rotational speed of the engine <NUM> is controlled.

The output shaft <NUM> is coupled to the engine <NUM>. The output shaft <NUM> is rotated by the driving of the engine <NUM>.

The rotational speed sensor <NUM> is provided on the output shaft <NUM>. The rotational speed sensor <NUM> detects the rotational speed of the engine <NUM>. The rotational speed of the engine <NUM> is the rotational speed of the output shaft <NUM>. The rotational speed sensor <NUM> outputs an electrical signal according to the rotational speed of the output shaft <NUM> to the travel controller <NUM>.

The power transmission <NUM> transmits the driving force of the engine <NUM> to the driving wheels <NUM> and <NUM>. The power transmission <NUM> includes a torque converter <NUM>, a transmission <NUM>, and solenoid valves <NUM>.

The torque converter <NUM> is coupled to the output shaft <NUM>. The driving force of the engine <NUM> is transmitted to the torque converter <NUM> via the output shaft <NUM>. The torque converter <NUM> includes a pump and a turbine coupled to the output shaft <NUM>. In the torque converter <NUM>, the turbine is rotated by hydraulic oil discharged from the pump.

The transmission <NUM> includes an input shaft <NUM>, a forward clutch <NUM>, a forward gear train <NUM>, a reverse clutch <NUM>, a reverse gear train <NUM>, and an output shaft <NUM>.

The input shaft <NUM> is coupled to the torque converter <NUM>. The driving force is transmitted to the transmission <NUM> from the torque converter <NUM> via the input shaft <NUM>.

The forward clutch <NUM> is provided on the input shaft <NUM>. The forward gear train <NUM> is provided between the forward clutch <NUM> and the output shaft <NUM>. The forward clutch <NUM> is switched between a connected state and a cut-off state. The connected state is a state in which the input shaft <NUM> and the forward gear train <NUM> are connected to each other. The cut-off state is a state in which the input shaft <NUM> and the forward gear train <NUM> are cut off from each other. When the input shaft <NUM> and the forward gear train <NUM> are connected to each other by the forward clutch <NUM>, the driving force is transmitted to the forward gear train <NUM> from the input shaft <NUM>. The driving force transmitted to the forward gear train <NUM> is transmitted to the output shaft <NUM>. In other words, the driving force of the engine <NUM> is transmitted to the output shaft <NUM> when the forward clutch <NUM> is connected to the forward gear train <NUM>. When the forward clutch <NUM> and the forward gear train <NUM> are cut off from each other, the driving force is not transmitted to the forward gear train <NUM> from the input shaft <NUM>.

The reverse clutch <NUM> is provided on the input shaft <NUM>. The reverse gear train <NUM> is provided between the reverse clutch <NUM> and the output shaft <NUM>. The reverse clutch <NUM> is switched between a connected state and a cut-off state. The connected state is a state in which the input shaft <NUM> and the reverse gear train <NUM> are connected to each other. The cut-off state is a state in which the input shaft <NUM> and the reverse gear train <NUM> are cut off from each other. When the input shaft <NUM> and the reverse gear train <NUM> are connected to each other by the reverse clutch <NUM>, the driving force is transmitted to the reverse gear train <NUM> from the input shaft <NUM>. The driving force transmitted to the reverse gear train <NUM> is transmitted to the output shaft <NUM>. In other words, the driving force of the engine <NUM> is transmitted to the output shaft <NUM> when the reverse clutch <NUM> is connected to the reverse gear train <NUM>. When the reverse clutch <NUM> and the reverse gear train <NUM> are cut off from each other, the driving force is not transmitted to the reverse gear train <NUM> from the input shaft <NUM>.

As the forward clutch <NUM> and the reverse clutch <NUM>, a hydraulic clutch is used. Examples of the hydraulic clutch include a multiplate wet clutch.

The driving force is transmitted to the output shaft <NUM> when the forward clutch <NUM> or the reverse clutch <NUM> is in the connected state. The output shaft <NUM> is rotated by the driving force transmitted from the forward clutch <NUM> or the reverse clutch <NUM>.

One solenoid valve <NUM> is provided for each of the forward clutch <NUM> and the reverse clutch <NUM>. The solenoid valves <NUM> control the supply and discharge of the hydraulic oil to and from the forward clutch <NUM> and the reverse clutch <NUM>. Each solenoid valve <NUM> performs the supply and discharge of the hydraulic oil in accordance with the power distribution to a solenoid. The clutches <NUM> and <NUM> are switched between the connected state and the cut-off state by the supply and discharge of the hydraulic oil controlled by the solenoid valve <NUM>.

The forward clutch <NUM> and the forward gear train <NUM> are connected to each other according to the instruction of the direction lever <NUM> for forward movement. The reverse clutch <NUM> and the reverse gear train <NUM> are connected to each other according to the instruction of the direction lever <NUM> for backward movement. Both of the forward clutch <NUM> and the reverse clutch <NUM> are placed in the cut-off state according to the instruction of the direction lever <NUM> for placing the forklift <NUM> in the neutral state.

The differential apparatus <NUM> is coupled to the output shaft <NUM>. The axle <NUM> is coupled to the differential apparatus <NUM>. The driving wheels <NUM> and <NUM> are coupled to the axle <NUM>. When the output shaft <NUM> rotates, the axle <NUM> rotates. The driving wheels <NUM> and <NUM> are rotated by the rotation of the axle <NUM>, so that the forklift <NUM> travels. When the forward clutch <NUM> and the forward gear train <NUM> are connected to each other, the forklift <NUM> moves forward. When the reverse clutch <NUM> and the reverse gear train <NUM> are connected to each other, the forklift <NUM> moves backward.

The vehicle speed sensor <NUM> is a sensor for detecting the vehicle speed of the vehicle body <NUM>. The vehicle speed of the vehicle body <NUM> means the vehicle speed of the forklift <NUM>. The vehicle speed sensor <NUM> is provided on the output shaft <NUM> or the axle <NUM>, for example. The vehicle speed sensor <NUM> outputs a pulse signal according to the vehicle speed of the vehicle body <NUM> to the travel controller <NUM>.

The travel controller <NUM> is an engine control unit that controls the engine <NUM>. The hardware configuration of the travel controller <NUM> is similar to that of the main controller <NUM>, for example. The travel controller <NUM> adjusts the throttle opening degree by controlling the throttle actuator <NUM>. The adjustment of the throttle opening degree adjusts the driving force of the engine <NUM>. The travel controller <NUM> controls the solenoid valves <NUM> that respectively switch the states of the clutches <NUM> and <NUM> between the connected state and the cut-off state. As a result, the clutches <NUM> and <NUM> are switched between the connected state and the cut-off state.

The load handling system <NUM> is a mechanism configured to operate the load handling apparatus <NUM>. The load handling system <NUM> includes an oil tank <NUM> in which hydraulic oil is stored, a hydraulic pump <NUM>, and a hydraulic mechanism <NUM>.

The hydraulic pump <NUM> is driven by the engine <NUM>. The hydraulic pump <NUM> pumps up the hydraulic oil from the oil tank <NUM>. The hydraulic oil pumped up is supplied to the hydraulic mechanism <NUM>.

The hydraulic mechanism <NUM> includes a control valve. The control valve controls the supply and discharge of the hydraulic oil to and from hydraulic equipment. Examples of the hydraulic equipment include the lift cylinders <NUM> and a tilt cylinder that tilts the load handling apparatus <NUM>. The load handling apparatus <NUM> is operated by the supply or discharge of the hydraulic oil. The hydraulic equipment simply need to be hydraulic equipment included in the forklift <NUM>, and may be hydraulic equipment included in the vehicle body <NUM>. Examples of the hydraulic equipment included in the vehicle body <NUM> include the clutches <NUM> and <NUM>.

The object detector <NUM> includes a stereo camera <NUM> for picking up images, an obstacle detection device <NUM> that detects an object from an image picked up by the stereo camera <NUM>, and a warning device <NUM>. As illustrated in <FIG>, the stereo camera <NUM> is disposed on the head guard <NUM>. The stereo camera <NUM> is disposed so as to have a bird's-eye view of the road surface on which the forklift <NUM> travels from an upper side of the forklift <NUM>. The stereo camera <NUM> of this embodiment picks up an image of a view behind the forklift <NUM>. Therefore, the object detected by the obstacle detection device <NUM> is an object located behind the forklift <NUM>. The warning device <NUM> and the obstacle detection device <NUM> may be unitized with the stereo camera <NUM> and may be disposed, with the stereo camera <NUM>, on the head guard <NUM>. The warning device <NUM> and the obstacle detection device <NUM> may be disposed in positions different from the position of the head guard <NUM>.

As illustrated in <FIG>, the stereo camera <NUM> includes two cameras <NUM> and <NUM>. The cameras <NUM> and <NUM> are cameras using a CCD image sensor or a CMOS image sensor, for example. Each of the cameras <NUM> and <NUM> is disposed such that optical axes thereof are parallel to each other. The two cameras <NUM> and <NUM> are spaced apart from each other, and hence the same object shows up in a shifted manner in images picked up by the two cameras <NUM> and <NUM>. Specifically, when images of the same object are picked up by two cameras <NUM> and <NUM>, the images show misalignment of pixels for the object depending on the distance between the two cameras <NUM> and <NUM>. The stereo camera <NUM> of this embodiment is a wide-angle stereo camera of which horizontal angle of view is <NUM> degrees or more, but may be a non-wide-angle stereo camera.

The obstacle detection device <NUM> includes a processor <NUM> and a storage unit <NUM>. As the processor <NUM>, for example, a CPU, a GPU, or a DSP is used. The storage unit <NUM> includes a RAM and a ROM. The storage unit <NUM> stores various programs for detecting an object from the images picked up by the stereo camera <NUM>. Specifically, the storage unit <NUM> stores program codes or commands to cause the processor <NUM> to execute processing. The storage unit <NUM>, i.e., a computer readable medium, includes any available media accessible by a general-purpose or dedicated computer. The obstacle detection device <NUM> may include a hardware circuit, such as an ASIC or an FPGA. The obstacle detection device <NUM>, which is a processing circuit, may include one or more processors that operate in accordance with a computer program, one or more hardware circuits, such as an ASIC and an FPGA, or a combination thereof.

The obstacle detection device <NUM> repeatedly performs processing below in a designated control cycle to detect an object existing around the forklift <NUM>. The obstacle detection device <NUM> derives the position of the detected object. The position of the object is a position relative to the forklift <NUM>.

As illustrated in <FIG>, in Step S100, the obstacle detection device <NUM> acquires an image from each of the cameras <NUM> and <NUM> of the stereo camera <NUM>.

Next, in Step S110, the obstacle detection device <NUM> acquires a parallax image by performing stereo processing. The parallax image is obtained by linking a parallax [px] to the pixels. The parallax image does not necessarily require display, and indicates data in which the parallax is linked to each pixel in the parallax image. The parallax is acquired by comparing the image picked up by the camera <NUM> of the stereo camera <NUM> and the image picked up by the camera <NUM> of the stereo camera <NUM>, and deriving a difference in the number of pixels between the images for the same feature points shown in the images. The obstacle detection device <NUM> sets one of the images picked up by the two cameras <NUM> and <NUM> to be a reference image and the other thereof to be a comparison image, and extracts the most similar pixel of the comparison image for each pixel of the reference image. The obstacle detection device <NUM> calculates the difference in the number of pixels between the pixels of the reference image and the pixels of the comparison image as the parallax. As a result, the parallax image in which the parallax is linked to each pixel of the reference image is acquired. The feature point is a part of an object that is recognized as a boundary, such as an edge of the object. The feature point is detected from brightness information and the like.

Next, in Step S120, the obstacle detection device <NUM> derives coordinates of the feature points in a world coordinate system, which is a coordinate system on an actual space. In the world coordinate system, the X-axis extends in one of horizontal directions of a horizontal plane and along the vehicle width direction of the forklift <NUM>, the Y-axis extends in one of the horizontal directions is orthogonal to the X-axis, and the Z-axis extends in a vertical direction, in a state in which the forklift <NUM> is positioned on the horizontal plane. The obstacle detection device <NUM> derives coordinates of the feature points in a camera coordinate system from a base line length of the stereo camera <NUM>, a focal length of the stereo camera <NUM>, and the parallax image acquired in Step S110, and then converts the coordinates derived to coordinates in the world coordinate system. As illustrated in <FIG>, the X-axis, the Y-axis, and the Z-axis are indicated by arrows X, Y, and Z.

As illustrated in <FIG>, in Step S130, the obstacle detection device <NUM> extracts the object by clustering the feature points. The feature points express a part of the object. From the feature points, the obstacle detection device <NUM> find a cluster of feature points assumed to express a part of the same object, and extracts the cluster as the object. More specifically, the obstacle detection device <NUM> clusters feature points positioned within a predetermined range based on the coordinates of the feature points in the world coordinate system derived in Step S120. The obstacle detection device <NUM> recognizes the clustered feature points as one object. The clustering of the feature points in Step S130 may be performed by various approaches.

Next, in Step S140, the obstacle detection device <NUM> derives the coordinates of the object in the world coordinate system. The coordinates of the object are derived from the coordinates of the feature points of the cluster. The coordinates of the object in the world coordinate system express a position of the object relative to the forklift <NUM>. Specifically, out of the coordinates of the object in the world coordinate system, the X-coordinate of the object expresses the distance from the origin to the object in the left-right direction, and the Y-coordinate of the object expresses the distance from the origin to the object in the front-rear direction. For example, the X-coordinate and the Y-coordinate of the coordinate origin corresponds to the position of the stereo camera <NUM> and the Z-coordinate of the coordinate origin is based on the road surface. The X-coordinate and the Y-coordinate of the object allow derivation of the Euclidean distance from the position of the stereo camera <NUM> to the object. The Z-coordinate of the object in the world coordinate system expresses the height from the road surface to the object.

Next, in Step S150, the obstacle detection device <NUM> determines whether the object is a person or an obstacle other than a person. The determination of whether the object is a person is performed by various methods. In this embodiment, the obstacle detection device <NUM> performs person detection processing using an image picked up by one of the two cameras <NUM> and <NUM> of the stereo camera <NUM>. The obstacle detection device <NUM> converts the coordinates of the object in the world coordinate system acquired in Step S140 to camera coordinates, and further converts the camera coordinates to the coordinates in the image picked up by the camera <NUM> or the camera <NUM>. In this embodiment, the obstacle detection device <NUM> converts the coordinates of the object in the world coordinate system to the coordinates in the reference image. The obstacle detection device <NUM> performs the person detection processing using the coordinates of an object in the reference image. The person detection processing performs feature extraction and use a person determiner that has learned through machine learning in advance, for example. Means of the feature extraction include a means to extract a feature amount of a local area in an image, such as a Histogram of Oriented Gradients (HOG) feature amount or a Haar-Like feature amount. As the person determiner, a person determiner that has learned through supervised machine learning is used, for example. Examples of the supervised learning model include a support vector machine, a neural network, naive Bayes, deep learning, and a decision tree. Training data used in the machine learning includes image-specific components, such as appearance elements and shape elements of a person extracted from an image. Examples of the shape elements include the size and the contour of a person. Examples of the appearance elements include light source information, texture information, and camera information. The light source information includes information relating to reflectance and shade. The texture information includes color information. The camera information includes information relating to image quality, resolution, and angle of view.

The warning device <NUM> is configured to give a warning to the operator of the forklift <NUM>. Examples of the warning device <NUM> include a buzzer that gives a warning by sound, a lamp that gives a warning by light, or a combination thereof.

As illustrated in <FIG>, the main controller <NUM>, the travel controller <NUM>, and the object detector <NUM> are configured to acquire information from each other by the bus <NUM>. The main controller <NUM>, the travel controller <NUM>, and the object detector <NUM> acquire information from each other by performing communication in accordance with a communication protocol for a vehicle, such as a controller area network (CAN) or local interconnect network (LIN).

The main controller <NUM> derives the vehicle speed of the vehicle body <NUM> by using the detection result of the vehicle speed sensor <NUM>, the gear ratio, the outer diameters of the driving wheels <NUM> and <NUM>, the steering angles detected by the wheel angle sensor <NUM>, and the like. The detection result of the vehicle speed sensor <NUM> is acquired from the travel controller <NUM>. The gear ratio and the outer diameters of the driving wheels <NUM> and <NUM> simply need to be stored in the storage unit <NUM> in advance. The main controller <NUM> also derives the traveling direction of the vehicle body <NUM> together with the vehicle speed of the vehicle body <NUM>. The traveling direction of the vehicle body <NUM> is either the forward movement direction or the backward movement direction. In this embodiment, the vehicle speed means an absolute value of the vehicle speed.

The main controller <NUM> activates the warning device <NUM> by transmitting a warning command via the bus <NUM>. Specifically, the object detector <NUM> includes an activator that activates the warning device <NUM>, and the activator activates the warning device <NUM> upon receiving the warning command.

Next, the control of the vehicle speed performed in the forklift <NUM> will be described.

In the forklift <NUM>, the main controller <NUM> performs automatic deceleration control depending on the position and type of the object detected by the object detector <NUM>. There are two types of the object: a person and an obstacle other than a person. In the description below, the obstacle means an object other than a person.

As illustrated in <FIG>, an automatic deceleration area AA2 used in the automatic deceleration control is set within a detectable area in which the object detector <NUM> can detect an object. In other words, the detectable area in which the object detector <NUM> can detect an object is an area in which the stereo camera <NUM> can pick up images. In this embodiment, the automatic deceleration area AA2 is the same region as the detectable area in which the object detector <NUM> can detect an object. The automatic deceleration area AA2 is a region that spreads rearward of the forklift <NUM> from the position of the stereo camera <NUM> and along the vehicle width direction of the forklift <NUM>. The automatic deceleration area AA2 is an area defined by the X-coordinate and the Y-coordinate in the world coordinate system.

The main controller <NUM> derives a predicted trajectory T of the vehicle body <NUM>. The predicted trajectory T is a trajectory that is predicted to be followed by the vehicle body <NUM>. In this embodiment, the main controller <NUM> derives the predicted trajectory T that is predicted to be followed by the vehicle body <NUM> when the traveling direction of the vehicle body <NUM> is the backward movement direction, for example, when the operation direction of the direction lever <NUM> by the operator has instructed the forklift <NUM> to move backward. The predicted trajectory T of the vehicle body <NUM> means the predicted trajectory T of the forklift <NUM>.

The predicted trajectory T is derived from the steering angles of the steered wheels <NUM> and dimension information of the forklift <NUM>. The dimension information of the forklift <NUM> includes the dimension [mm] from the central axis line of the driving wheels <NUM> and <NUM> to a rear end of the vehicle body <NUM>, the wheelbase [mm], and the vehicle width [mm]. The dimension information of the forklift <NUM> is known information, and hence is stored in the storage unit <NUM> of the main controller <NUM> and the like in advance. The predicted trajectory T is a region between a trajectory LT followed by a left end LE of the vehicle body <NUM> and a trajectory RT followed by a right end RE of the vehicle body <NUM>. The main controller <NUM> derives the X-coordinate and the Y-coordinate of the predicted trajectory T that extends rearward of the forklift <NUM> in the world coordinate system.

As illustrated in <FIG>, when the forklift <NUM> moves in a straight line, the predicted trajectory T becomes a trajectory that linearly extends from the forklift <NUM> in the backward movement direction. As illustrated in <FIG>, when the forklift <NUM> is turning, the predicted trajectory T becomes a trajectory that curves from the forklift <NUM> in the backward movement direction. The predicted trajectory T extends to the right side when the forklift <NUM> is turning to the right side, and the predicted trajectory T extends to the left side when the forklift <NUM> is turning to the left side. In other words, the main controller <NUM> derives the predicted trajectory T that extends in the turning direction of the forklift <NUM> when the forklift <NUM> is turning.

The forklift <NUM> illustrated in <FIG> has a higher vehicle speed than the forklift <NUM> in the state illustrated in <FIG>. Similarly, the forklift <NUM> illustrated in <FIG> has a higher vehicle speed than the forklift <NUM> illustrated in <FIG>. As illustrated in <FIG>, the main controller <NUM> extends the predicted trajectory T in the traveling direction of the forklift <NUM> as the vehicle speed of the vehicle body <NUM> increases. In this embodiment, a trajectory derivation threshold value YT is changed depending on the vehicle speed. The trajectory derivation threshold value YT is a threshold value set for the Y-coordinate in the world coordinate system, and the Y-coordinate is further separated from the forklift <NUM> as the vehicle speed increases. The main controller <NUM> derives the predicted trajectory T from the forklift <NUM> to the trajectory derivation threshold value YT. The expression of "extending the predicted trajectory T in the traveling direction as the vehicle speed of the vehicle body <NUM> increases" is not limited to an aspect in which the vehicle speed of the vehicle body <NUM> and the distance of the predicted trajectory T in the traveling direction are proportional to each other, and a correlation in which the distance of the predicted trajectory T in the traveling direction increases as the vehicle speed of the vehicle body <NUM> increases is simply needed.

The predicted trajectory T is derived within the automatic deceleration area AA2. In this embodiment, the main controller <NUM> functions as a predicted trajectory calculator.

The automatic deceleration control will be described below. The X-coordinate and the Y-coordinate in the description below are the X-coordinate and the Y-coordinate in the world coordinate system.

The automatic deceleration control includes travel stop control and vehicle speed limitation control. The travel stop control is stop control of the forklift <NUM>. The vehicle speed limitation control is travelling authorization control of the forklift <NUM> at the vehicle-speed equal to or less than the upper-limit value.

As illustrated in <FIG>, in the travel stop control, the main controller <NUM> is placed in one of a normal control state S10, a pre-travel-limitation state S11, a travel limitation state S12, and a travel limitation pre-removal state S13. As a result, control according to each state is performed.

As shown in <FIG>, the normal control state S10 is a state in which a vehicle speed limitation is not performed. In the normal control state S10, an acceleration rate limitation is not performed either. When the main controller <NUM> is in the normal control state S10, the main controller <NUM> computes a target rotational speed of the engine <NUM> from an accelerator opening degree detected by the accelerator sensor <NUM>. The target rotational speed increases as the accelerator opening degree increases. The main controller <NUM> determines whether to move the forklift <NUM> forward or backward based on the operation direction of the direction lever <NUM>. The main controller <NUM> generates a rotational speed command including information indicating the target rotational speed and information indicating the operation direction of the direction lever <NUM>. The main controller <NUM> transmits the rotational speed command to the travel controller <NUM>. The travel controller <NUM> controls the engine <NUM> so that the engine <NUM> follows the target rotational speed. Specifically, the travel controller <NUM> adjusts the throttle opening degree by controlling the throttle actuator <NUM>. As a result, the forklift <NUM> travels at a vehicle speed according to the operation amount of the accelerator pedal <NUM> by the operator. As described above, the main controller <NUM> controls the rotational speed of the engine <NUM> by transmitting the rotational speed command to the travel controller <NUM>. Controlling the rotational speed of the engine <NUM> adjusts the driving force to be transmitted to the driving wheels <NUM> and <NUM>. In other words, the main controller <NUM> adjusts the driving force to be transmitted to the driving wheels <NUM> and <NUM>.

The state in which the vehicle speed limitation is not performed includes an aspect in which the vehicle-speed upper-limit value is not set, and further includes an aspect in which a vehicle-speed upper-limit value is set to a value that substantially does not function, e.g., a value higher than a maximum speed that may be reached by the forklift <NUM>. Similarly, the state in which the acceleration rate limitation is not performed includes an aspect in which the acceleration-rate upper-limit value is not set, and further includes an aspect in which an acceleration-rate upper-limit value is set to a value that substantially does not function, e.g., a value higher than a maximum acceleration rate that may be reached by the forklift <NUM>.

As illustrated in <FIG>, when a pre-travel-limitation condition is satisfied while the main controller <NUM> is in the normal control state S10, the main controller <NUM> transitions to the pre-travel-limitation state S11. The satisfaction of the pre-travel-limitation condition means the satisfaction of both of Conditions A1 and A2 below.

Condition A1. A person exists in a warning area.

Condition A2. The forklift <NUM> is traveling in the backward movement direction.

The warning area is an area that is provided within the automatic deceleration area AA2 and different from an area in which the vehicle speed limitation is performed. The warning area is an area where a warning is given by the warning device <NUM> before a person enters the predicted trajectory T. The warning area of Condition A1 may be the whole of the automatic deceleration area AA2 excluding the inside of the predicted trajectory T, or may be a designated range that spreads outward of the predicted trajectory T.

Whether the forklift <NUM> is traveling in the backward movement direction is determined from the vehicle speed and the traveling direction of the forklift <NUM> computed by the main controller <NUM>. When the traveling direction of the forklift <NUM> is the backward movement direction and the vehicle speed is higher than a stop determination threshold value [km/h], the main controller <NUM> determines that the forklift <NUM> is traveling in the backward movement direction. The stop determination threshold value is set to a value at which it is considered that the forklift <NUM> is stopped. As the stop determination threshold value, a value arbitrarily selected from <NUM> [km/h] to <NUM> [km/h] is set, for example.

The pre-travel-limitation state S11 is a state in which a warning is given by the warning device <NUM>. In the pre-travel-limitation state S11, the vehicle speed limitation and the acceleration rate limitation are not performed. The warning is not given in the pre-travel-limitation state S11 at the time of a switchback of the forklift <NUM>. The switchback is a motion of switching between the forward movement and the backward movement by operation of the direction lever <NUM>. The main controller <NUM> turns on a switchback flag when the detection result of the direction sensor <NUM> and the traveling direction of the forklift <NUM> do not match each other. The main controller <NUM> does not cause the warning device <NUM> to give a warning when the main controller <NUM> transitions to the pre-travel-limitation state S11 in a state in which the switchback flag is turned on. The switchback flag is removed when the main controller <NUM> transitions from the pre-travel-limitation state S11 to another state, for example.

When a pre-travel-limitation removal condition is satisfied while the main controller <NUM> is in the pre-travel-limitation state S11, the main controller <NUM> transitions to the normal control state S10. The satisfaction of the pre-travel-limitation removal condition means the satisfaction of at least one of Conditions B1 or B2 below.

Condition B1. A person does not exist on the predicted trajectory T and in the warning area.

Condition B2. Traveling in the backward movement direction is stopped and backward movement operation is not performed.

The expression of "traveling in the backward movement direction is stopped" means that the vehicle speed of the forklift <NUM> becomes equal to or less than the stop determination threshold value from a state in which the vehicle speed is higher than the stop determination threshold value. That is, the traveling forklift <NUM> is stopped. A state in which the backward movement operation is not performed is formed when at least one of a state in which the accelerator pedal <NUM> is not operated or a state in which the detection result of the direction sensor <NUM> is not the backward movement is satisfied. The state in which the detection result of the direction sensor <NUM> is not the backward movement is a state in which the detection result of the direction sensor <NUM> is neutral or the forward movement.

When a travel limitation condition is satisfied while the main controller <NUM> is in the pre-travel-limitation state S11, the main controller <NUM> transitions to the travel limitation state S12. The satisfaction of the travel limitation condition means the satisfaction of both of Conditions C1 and C2 below.

Condition C1. A person exists on the predicted trajectory T.

Condition C2. The forklift <NUM> is traveling in the backward movement direction.

Whether Condition C1 is satisfied is determined from the X-coordinate and the Y-coordinate of a person. The predicted trajectory T is defined by the X-coordinate and the Y-coordinate, and hence it is determined whether a person exists on the predicted trajectory T from the X-coordinate and the Y-coordinate of the person. Condition C2 is the same condition as Condition A2.

As shown in <FIG>, the travel limitation state S12 is a state in which the traveling forklift <NUM> is decelerated and stopped by setting the vehicle-speed upper-limit value to <NUM>. The vehicle speed limitation is imposed on the vehicle body <NUM> by setting the vehicle-speed upper-limit value. The vehicle speed limitation of the vehicle body <NUM> means the vehicle speed limitation of the forklift <NUM>. The main controller <NUM> performs control so that the driving force to the driving wheels <NUM> and <NUM> is cut off. The cut-off of the driving force to the driving wheels <NUM> and <NUM> is one aspect of adjustment of the driving force transmitted to the driving wheels <NUM> and <NUM>. The main controller <NUM> cuts off the driving force to the driving wheels <NUM> and <NUM> by transmitting a cut-off command to the travel controller <NUM>. When the travel controller <NUM> receives the cut-off command, the travel controller <NUM> controls the power transmission <NUM> so that the driving force of the engine <NUM> is not transmitted to the driving wheels <NUM> and <NUM>. For example, the travel controller <NUM> controls the transmission <NUM> such that the clutches <NUM> and <NUM> are not respectively connected with the gear trains <NUM> and <NUM>, and places the clutches <NUM> and <NUM> in a cut-off state. As a result, the forklift <NUM> is decelerated due to running resistance. When the forklift <NUM> is traveling on a flat road, the forklift <NUM> stops. The running resistance includes air resistance, rolling resistance, and gradient resistance. In the travel limitation state S12, the warning device <NUM> gives a warning.

As illustrated in <FIG>, when a travel limitation removal condition is satisfied while the main controller <NUM> is in the travel limitation state S12, the main controller <NUM> transitions to the normal control state S10. The satisfaction of the travel limitation removal condition means the satisfaction of Condition D1 below.

Condition D1. The traveling in the backward movement direction is stopped and the backward movement operation is not performed.

Condition D1 is the same condition as Condition B2.

When a travel limitation pre-removal condition is satisfied while the main controller <NUM> is in the travel limitation state S12, the main controller <NUM> transitions to the travel limitation pre-removal state S13. The satisfaction of the travel limitation pre-removal condition means the satisfaction of both of Conditions E1 and E2 below.

Condition E1. A person does not exist on the predicted trajectory T.

Condition E2. The forklift <NUM> is traveling in the backward movement direction.

In other words, Condition E1 is satisfied when Condition C1 is not satisfied. Condition E2 is the same condition as Condition A2.

As shown in <FIG>, the travel limitation pre-removal state S13 is a state in which an acceleration rate limitation is performed while the vehicle speed limitation is removed. The main controller <NUM> sets the acceleration-rate upper-limit value to AS1 [m/s<NUM>], and performs control so that the acceleration rate of the forklift <NUM> does not exceed AS1. The value AS1 is a value larger than <NUM> and lower than the maximum acceleration rate that may be reached by the forklift <NUM>. The main controller <NUM> permits the acceleration of the forklift <NUM> at AS1 or less. In order to perform an acceleration rate limitation, the main controller <NUM> performs control so that the acceleration rate of the forklift <NUM> does not exceed the acceleration-rate upper-limit value. For example, the main controller <NUM> limits the increase of the rotational speed of the engine <NUM> to perform acceleration rate limitation. Specifically, the main controller <NUM> transmits a command to the travel controller <NUM> so that the travel controller <NUM> limits the increase of the rotational speed of the engine <NUM>. The travel controller <NUM> limits the increase of the rotational speed of the engine <NUM> per unit time so as to perform control so that the acceleration rate of the forklift <NUM> does not exceed AS1. In the travel limitation pre-removal state S13, the warning device <NUM> does not give a warning.

As illustrated in <FIG>, when a travel limitation actual-removal condition is satisfied while the main controller <NUM> is in the travel limitation pre-removal state S13, the main controller <NUM> transitions to the normal control state S10. The satisfaction of the travel limitation actual-removal condition means the satisfaction of at least one of Conditions F1 or F2 below.

Condition F1. The vehicle speed of the forklift <NUM> reaches a value obtained by subtracting a first predetermined value from a target vehicle speed.

Condition F2. The backward movement operation is not performed.

In other words, Condition F1 is that a velocity deviation between the target vehicle speed and the vehicle speed of the forklift <NUM> becomes less than the first predetermined value. In the travel limitation pre-removal state S13, the speed followability of the forklift <NUM> decreases since an acceleration rate limitation is performed, so that it becomes difficult for the vehicle speed of the forklift <NUM> to reach the target vehicle speed. The first predetermined value is set in order to determine that the vehicle speed of the forklift <NUM> has reached the target vehicle speed intended by the operator in a state in which an acceleration rate limitation is performed. As the first predetermined value, a value arbitrarily selected from <NUM> [km/h] to <NUM> [km/h] is set, for example.

When the travel limitation condition is satisfied while the main controller <NUM> is in the travel limitation pre-removal state S13, the main controller <NUM> transitions to the travel limitation state S12. Similarly, when the travel limitation condition is satisfied while the main controller <NUM> is in the normal control state S10, the main controller <NUM> transitions to the travel limitation state S12.

As described above, the main controller <NUM> extends the predicted trajectory T in the traveling direction as the vehicle speed of the vehicle body <NUM> increases. If the main controller <NUM> transitions to the travel limitation state S12 and the predicted trajectory T is shortened in the traveling direction as the vehicle speed of the vehicle body <NUM> decreases, the person is likely be placed on the outside of the predicted trajectory T. As a result, the main controller <NUM> alternately transitions to the travel limitation state S12 and the travel limitation pre-removal state S13 even though the forklift <NUM> and the person are becoming closer to each other. In order to prevent this situation, the main controller <NUM> maintains the distance of the predicted trajectory T in the traveling direction, i.e., the trajectory derivation threshold value YT regardless of the vehicle speed of the vehicle body <NUM> when a person is detected on the predicted trajectory T. The maintenance of the trajectory derivation threshold value YT is removed, for example, when a person no longer exists on the predicted trajectory T.

Next, the vehicle speed limitation control will be described. As the vehicle speed limitation control, different controls are performed depending on a case where the object is a person or a case where the object is an obstacle. The state transition diagrams are the same for the case where the object is a person and the case where the object is an obstacle, and hence the vehicle speed limitation control for both of the cases will be described with reference to <FIG>. First, the vehicle speed limitation control for the case where the object is a person will be described.

As illustrated in <FIG>, in the vehicle speed limitation control, the main controller <NUM> is placed in one of a limitation removal state S21, a pre-limitation-start state S22, a limitation start state S23, and a limitation pre-removal state S24. As a result, control is performed according to each state.

As shown in <FIG>, the limitation removal state S21 is a state in which the vehicle speed limitation is not performed. In the limitation removal state S21, the acceleration rate limitation is not performed either.

As illustrated in <FIG>, when a pre-limitation-start condition is satisfied while the main controller <NUM> is in the limitation removal state S21, the main controller <NUM> transitions to the pre-limitation-start state S22. The satisfaction of the pre-limitation-start condition means the satisfaction of both of Conditions G1 and G2 below.

Condition G1. A person exists in an advance warning area within the automatic deceleration area AA2.

Condition G2. The forklift <NUM> is traveling in the backward movement direction.

The advance warning area is an area far away from the forklift <NUM> as compared to a vehicle speed limitation area in which the vehicle speed limitation is performed. The vehicle speed limitation area is an area within the automatic deceleration area AA2 and outside the predicted trajectory T and where the vehicle speed limitation is performed. The vehicle speed limitation may not be performed at a place within the automatic deceleration area AA2 and far away from the forklift <NUM>. That is, the automatic deceleration area AA2 includes both of the vehicle speed limitation area in which the vehicle speed limitation is performed and an area which is far away from the forklift <NUM> as compared to the vehicle speed limitation area and in which the vehicle speed limitation is not performed. The vehicle speed limitation area is a region that spreads rightward, leftward, and rearward of the predicted trajectory T. The vehicle speed limitation area is determined based on the vehicle speed of the forklift <NUM> and the predicted trajectory T. The advance warning area is derived from the vehicle speed of the forklift <NUM> and the vehicle-speed upper-limit value set according to the position of a person. The advance warning area is set so that the amount of time from when a person enters the advance warning area to when the person enters the vehicle speed limitation area is within a predetermined amount of time. Examples of the predetermined amount of time include <NUM> second to <NUM> seconds.

The pre-limitation-start state S22 is a state in which the warning device <NUM> gives a warning. In other words, the pre-limitation-start state S22 is a state where the warning device <NUM> warns the operator about a possibility of a vehicle speed limitation before the vehicle speed limitation is actually performed. In the pre-limitation-start state S22, the vehicle speed limitation and the acceleration rate limitation are not performed. As with the case for the pre-travel-limitation state S11, a warning is not given at the time of the switchback of the forklift <NUM> in the pre-limitation-start state S22.

When a pre-limitation-start removal condition is satisfied while the main controller <NUM> is in the pre-limitation-start state S22, the main controller <NUM> transitions to the limitation removal state S21. The satisfaction of the pre-limitation-start removal condition means the satisfaction of at least one of Conditions H1 or H2 below.

Condition H1. A person does not exist in the vehicle speed limitation area and the advance warning area.

Condition H2. The traveling in the backward movement direction is stopped and the backward movement operation is not performed.

When a first limitation start condition is satisfied while the main controller <NUM> is in the pre-limitation-start state S22, the main controller <NUM> transitions to the limitation start state S23. The satisfaction of the first limitation start condition means the satisfaction of both of Conditions I1 and I2 below.

Condition I1. A person exists in the vehicle speed limitation area within the automatic deceleration area AA2.

Condition I2. The forklift <NUM> is traveling in the backward movement direction.

As shown in <FIG>, the limitation start state S23 is a state in which the vehicle speed limitation is imposed on the forklift <NUM> because a person exists in the vehicle speed limitation area within the automatic deceleration area AA2. The vehicle-speed upper-limit value falls as the distance from the forklift <NUM> to the person decreases. In the storage unit <NUM> of the main controller <NUM> or a storage medium, such as an external storage apparatus, a map in which the vehicle-speed upper-limit value is linked to the distance from the forklift <NUM> to the person is stored. The main controller <NUM> sets a map value that is a vehicle-speed upper-limit value in accordance with the map to the vehicle-speed upper-limit value. The vehicle-speed upper-limit value is not limited to an aspect in which the vehicle-speed upper-limit value falls in proportion to the decrease in the distance from the forklift <NUM> to the person, and a correlation in which the vehicle-speed upper-limit value falls when the distance from the forklift <NUM> to the person is simply needed. When there are multiple people in the vehicle speed limitation area within the automatic deceleration area AA2, the vehicle-speed upper-limit value is determined according to the position of one of the people closest to the forklift <NUM>.

The vehicle-speed upper-limit value set in the limitation start state S23 is a value larger than <NUM>. When the vehicle-speed upper-limit value is set in the limitation start state S23, the main controller <NUM> performs control so that a force acts in the direction in which the movement of the vehicle body <NUM> is prevented, so as to prevent the vehicle speed of the vehicle body <NUM> from exceeding the vehicle-speed upper-limit value. The main controller <NUM> sets a limitation value to the target rotational speed of the engine <NUM> to perform control so that the vehicle speed of the vehicle body <NUM> does not exceed the vehicle-speed upper-limit value. The lowest value of the limitation value corresponds to an idling rotational speed. The main controller <NUM> transmits a rotational speed command including a target rotational speed corresponding to the accelerator opening degree to the travel controller <NUM> when the target rotational speed corresponding to the accelerator opening degree is equal to or less than the limitation value. When the target rotational speed corresponding to the accelerator opening degree is more than the limitation value, the main controller <NUM> transmits, to the travel controller <NUM>, a rotational speed command for setting the limitation value to the target rotational speed. The travel controller <NUM> performs control of the throttle actuator <NUM> so that the rotational speed of the engine <NUM> reaches the limitation value. As a result, the forklift <NUM> is decelerated by engine braking. The engine braking causes a force to act on the forklift <NUM> in the direction in which the movement of the vehicle body <NUM> is prevented. The forklift <NUM> is decelerated until the rotational speed of the engine <NUM> reaches a vehicle speed corresponding to the limitation value. In the limitation start state S23, the warning device <NUM> gives a warning.

As illustrated in <FIG>, when a limitation-start removal condition is satisfied while the main controller <NUM> is in the limitation start state S23, the main controller <NUM> transitions to the limitation removal state S21. The satisfaction of the limitation-start removal condition means the satisfaction of Condition J1 below. When the first limitation start condition is satisfied while the main controller <NUM> is in the limitation removal state S21, the main controller <NUM> transitions to the limitation start state S23.

Condition J1. The traveling in the backward movement direction is stopped and the backward movement operation is not performed.

When a limitation pre-removal condition is satisfied while the main controller <NUM> is in the limitation start state S23, the main controller <NUM> transitions to the limitation pre-removal state S24. The satisfaction of the limitation pre-removal condition means the satisfaction of Condition K1 below.

Condition K1. A person does not exist in the vehicle speed limitation area within the automatic deceleration area AA2.

As shown in <FIG>, the limitation pre-removal state S24 is a state in which the acceleration rate limitation is performed by setting the acceleration-rate upper-limit value to AS2 [m/s<NUM>] while the vehicle speed limitation is removed. The value AS2 is a value that is larger than <NUM> and lower than the maximum acceleration rate reached by the forklift <NUM>. The main controller <NUM> permits the acceleration of the forklift <NUM> at AS2 or less. The value AS2 may be the same value as AS1 or a different value from AS1.

As illustrated in <FIG>, when a second limitation start condition is satisfied while the main controller <NUM> is in the limitation pre-removal state S24, the main controller <NUM> transitions to the limitation start state S23. The satisfaction of the second limitation start condition means the satisfaction of Condition L1 below.

Condition L1. A person exists in the vehicle speed limitation area within the automatic deceleration area AA2.

When a limitation actual-removal condition is satisfied while the main controller <NUM> is in the limitation pre-removal state S24, the main controller <NUM> transitions to the limitation removal state S21. The satisfaction of the limitation actual-removal condition means the satisfaction of at least one of Conditions M1 or M2 below.

Condition M1. The vehicle speed of the forklift <NUM> reaches a value obtained by subtracting a second predetermined value from the target vehicle speed.

Condition M2. The backward movement operation is not performed.

In other words, in Condition M1, a velocity deviation between the target vehicle speed and the vehicle speed of the forklift <NUM> becomes less than the second predetermined value. In the limitation pre-removal state S24, the speed followability of the forklift <NUM> decreases since the acceleration rate limitation is performed, so that it becomes difficult for the vehicle speed of the forklift <NUM> to reach the target vehicle speed. The second predetermined value is set in order to determine that the vehicle speed of the forklift <NUM> has reached the target vehicle speed intended by the operator in a state in which an acceleration rate limitation is performed. As the second predetermined value, a value arbitrarily selected from <NUM> [km/h] to <NUM> [km/h] is set, for example. The second predetermined value may be the same value as the first predetermined value or a different value from the first predetermined value.

As with the case of the travel stop control, the main controller <NUM> may maintain the trajectory derivation threshold value YT when a person existing in the vehicle speed limitation area is detected.

Next, the vehicle speed limitation control will be described for the case where the object is an obstacle. The following description will focus on differences between the case where the object is a person and the case where the object is an obstacle, and will not elaborate similarity between both cases.

The satisfaction of the pre-limitation-start condition for the case where the object is an obstacle means the satisfaction of both of Conditions N1 and N2 below.

Condition N1. An obstacle exists in the advance warning area within the automatic deceleration area AA2.

Condition N2. The forklift <NUM> is traveling in the backward movement direction.

The advance warning area is an area far away from the forklift <NUM> as compared to the vehicle speed limitation area. The advance warning area is derived from the vehicle speed of the forklift <NUM> and a vehicle-speed upper-limit value set according to the position of the obstacle, and is set so that the amount of time from when the obstacle enters the advance warning area to when the obstacle enters the vehicle speed limitation area is within a predetermined amount of time. Examples of the predetermined amount of time include <NUM> second to <NUM> seconds. When the object is an obstacle, the advance warning area is at least one of an area within the predicted trajectory T and far away from the forklift <NUM> as compared to the vehicle speed limitation area or an area outside the predicted trajectory T and an extension of the predicted trajectory T.

The vehicle speed limitation area when the object is an obstacle is an area that is within the automatic deceleration area AA2 and also within the predicted trajectory T. The case where the object is an obstacle is different from the case where the object is a person in that the vehicle speed limitation area is set within the predicted trajectory T. In other words, when an obstacle exists on the predicted trajectory T, the main controller <NUM> performs control so that a force acts in the direction in which the movement of the vehicle body <NUM> is prevented, so as to prevent the vehicle speed of the vehicle body <NUM> from exceeding the vehicle-speed upper-limit value. As with the case where the object is a person, the main controller <NUM> prevents the vehicle speed of the vehicle body <NUM> from exceeding the vehicle-speed upper-limit value by engine braking.

The pre-limitation-start removal condition, the first limitation start condition, the limitation-start removal condition, the limitation pre-removal condition, the second limitation start condition, and the limitation actual-removal condition are also applied in a case where the object is an obstacle, instead of a person.

The vehicle-speed upper-limit value imposed on the forklift <NUM> when the object is an obstacle falls as the distance from the forklift <NUM> to the obstacle decreases. In the storage unit <NUM> of the main controller <NUM> or a storage medium, such as an external storage apparatus, a map in which the vehicle-speed upper-limit value is linked to the distance from the forklift <NUM> to the obstacle is stored. The main controller <NUM> sets the vehicle-speed upper-limit value from the map. The vehicle-speed upper-limit value imposed on the forklift <NUM> when the object is an obstacle is a value larger than <NUM>. The vehicle-speed upper-limit value is not limited to an aspect in which the vehicle-speed upper-limit value falls in proportion to the decrease in the distance from the forklift <NUM> to the obstacle, and a correlation in which the vehicle-speed upper-limit value falls when the distance from the forklift <NUM> to the obstacle decreases is simply needed.

As described above, the main controller <NUM> sets the vehicle-speed upper-limit value according to the state. In this embodiment, the main controller <NUM> functions as a vehicle-speed upper-limit setter.

Functions of this embodiment will be described.

When a person enters the warning area while the forklift <NUM> is traveling, the main controller <NUM> transitions to the pre-travel-limitation state S11. The main controller <NUM> causes the warning device <NUM> to give a warning to the operator so that the operator recognizes a possibility that a person may enter the predicted trajectory T. When the operator turns the forklift <NUM> in a direction in which the operator moves away from the person or stops the forklift <NUM> so as not to perform the backward movement, the main controller <NUM> transitions to the normal control state S10. When the person enters the predicted trajectory T in a state in which the main controller <NUM> is placed in the pre-travel-limitation state S11, the main controller <NUM> transitions to the travel limitation state S12. The main controller <NUM> sets the vehicle-speed upper-limit value to <NUM>, so that the forklift <NUM> stops. At this time, the main controller <NUM> cuts off the transmission of the driving force of the engine <NUM> to the driving wheels <NUM> and <NUM>. As a result, the forklift <NUM> is decelerated by the running resistance and the forklift <NUM> then stops.

The forklift <NUM> is stopped when the main controller <NUM> transitions to the travel limitation state S12. When the backward movement operation is not performed by the operator in this situation, the main controller <NUM> transitions to the normal control state S10. When the travel limitation condition is satisfied while the main controller <NUM> is in the normal control state S10, the main controller <NUM> transitions to the travel limitation state S12 without being placed in the pre-travel-limitation state S11. A situation in which the travel limitation condition is satisfied without the satisfaction of the pre-travel-limitation condition may be, for example, a situation where the speed of the forklift <NUM> is relatively high or a situation in which an object enters the predicted trajectory T from a blind spot of a detection of the object detector <NUM>.

When a person no longer exists on the predicted trajectory T before the forklift <NUM> is stopped while the main controller <NUM> is in the travel limitation state S12, the main controller <NUM> transitions to the travel limitation pre-removal state S13. When a person enters the predicted trajectory T again after the main controller <NUM> transitions to the travel limitation pre-removal state S13, the main controller <NUM> transitions to the travel limitation state S12. In the travel limitation pre-removal state S13, the acceleration rate limitation is performed. In the travel limitation state S12, the vehicle speed limitation is performed, and hence the velocity deviation may increase. Therefore, the forklift <NUM> is gradually accelerated by placement of the main controller <NUM> in the travel limitation pre-removal state S13 before the main controller <NUM> transitions from the travel limitation state S12 to the normal control state S10.

When the forklift <NUM> is accelerated and the velocity deviation decreases while the travel limitation pre-removal state S13 is maintained, the main controller <NUM> transitions to the normal control state S10. Since the acceleration rate limitation is performed in the travel limitation pre-removal state S13, the acceleration of the forklift <NUM> is not efficiently performed. When the acceleration is desired to be efficiently performed, an accelerator is released so as to remove the travel limitation pre-removal state S13, which leads to workability improvement.

As described above, when a person enters the predicted trajectory T in a state in which the forklift <NUM> is moving backward, the travel stop control functions to stop the forklift <NUM>. In this situation, the person is positioned behind the forklift <NUM> while the forklift <NUM> is moving backward. Accordingly, the vehicle-speed upper-limit value is set when the traveling direction of the forklift <NUM> is a direction toward the person.

When an obstacle enters the advance warning area while the forklift <NUM> is traveling, the main controller <NUM> transitions to the pre-limitation-start state S22. The main controller <NUM> causes the warning device <NUM> to give a warning to the operator so that the operator recognizes a nearby obstacle. When the operator turns the forklift <NUM> in a direction in which the operator moves away from the obstacle or stops the forklift <NUM> so as not to perform the backward movement, the main controller <NUM> transitions to the limitation removal state S21. When the obstacle enters the vehicle speed limitation area in a state in which the main controller <NUM> is placed in the pre-limitation-start state S22, the main controller <NUM> transitions to the limitation start state S23. The main controller <NUM> sets the vehicle-speed upper-limit value to a value in accordance with the map. At this time, the forklift <NUM> is decelerated by engine braking.

In the limitation start state S23, although the vehicle-speed upper-limit value is set, the traveling of the forklift <NUM> is permitted at the vehicle-speed upper-limit value or less. This allows the operator to drive the forklift <NUM> while avoiding the obstacle. When the limitation-start removal condition is satisfied while the main controller <NUM> is in the limitation start state S23, the main controller <NUM> transitions to the limitation removal state S21 to remove the vehicle speed limitation.

When the operator maintains traveling of the forklift <NUM> in the limitation start state S23 and an obstacle no longer exists in the vehicle speed limitation area, the main controller <NUM> transitions to the limitation pre-removal state S24. As a result, the vehicle speed limitation is removed. The acceleration rate limitation is performed in the limitation pre-removal state S24. In the limitation start state S23, the vehicle speed limitation is imposed, and hence the velocity deviation may increase. Therefore, the forklift <NUM> is gradually accelerated by placement of the main controller <NUM> in the limitation pre-removal state S24 before the main controller <NUM> transitions from the limitation start state S23 to the limitation removal state S21.

When the forklift <NUM> is accelerated and the velocity deviation decreases while the limitation pre-removal state S24 is maintained, the main controller <NUM> transitions to the limitation removal state S21. Since the acceleration rate limitation is performed in the limitation pre-removal state S24, the acceleration of the forklift <NUM> is not efficiently performed. When the acceleration is desired to be efficiently performed, the accelerator is released so as to remove the limitation pre-removal state S24, which leads to workability improvement. When the operator changes the traveling direction of the forklift <NUM> to the forward movement direction while the main controller <NUM> is in the limitation pre-removal state S24, the main controller <NUM> transitions to the limitation removal state S21. When the obstacle enters the vehicle speed limitation area again before the main controller <NUM> transitions from the limitation pre-removal state S24 to the limitation removal state S21, the main controller <NUM> transitions to the limitation start state S23.

As described above, when the obstacle enters the vehicle speed limitation area set within the predicted trajectory T in a state in which the forklift <NUM> is moving backward, the vehicle speed limitation control for the obstacle functions to perform the vehicle speed limitation. Meanwhile, when the obstacle exists outside the predicted trajectory T, the vehicle speed limitation is not performed. In this situation, the obstacle is positioned behind the forklift <NUM> while the forklift <NUM> is moving backward. Accordingly, the vehicle-speed upper-limit value is set when the traveling direction of the forklift <NUM> is a direction toward the obstacle.

In this embodiment, the state transitions are performed in parallel among controls such as the travel stop control, the vehicle speed limitation control for a person, and the vehicle speed limitation control for an obstacle. Therefore, there is a possibility that vehicle-speed upper-limit value and the warning aspect may be different among the state transitions. In this case, control corresponding to any one of the states simply needs to be performed upon priority levels set in advance. For example, the main controller <NUM> performs control corresponding a state in which the vehicle-speed upper-limit value becomes the lowest.

Effects of this embodiment will be described.

The main controller <NUM> controls the engine <NUM> so that the vehicle speed of the vehicle body <NUM> does not exceed the vehicle-speed upper-limit value. When the vehicle speed of the vehicle body <NUM> is higher than the vehicle-speed upper-limit value, the main controller <NUM> performs the control so that the force acts in the direction in which the movement of the vehicle body <NUM> is prevented and the control so that the driving force to the driving wheels <NUM> and <NUM> is cut off. Since engine braking provides deceleration at a relatively low deceleration rate, the forklift <NUM> is gradually decelerated. When the driving force to the driving wheels <NUM> and <NUM> is cut off, the forklift <NUM> is decelerated by the running resistance. Since the running resistance provides the deceleration at a relatively low deceleration rate, the forklift <NUM> is gradually decelerated. This allows the vehicle speed limitation to be imposed on the forklift <NUM> while suppressing the occurrence of a load collapse.

(<NUM>) The main controller <NUM> performs both of the control so that the force acts in the direction in which the movement of the vehicle body <NUM> is prevented and the control so that the driving force to the driving wheels <NUM> and <NUM> is cut off. In the embodiment, the driving force to the driving wheels <NUM> and <NUM> is cut off in the travel limitation state S12. In the limitation start state S23, engine braking causes a force to act in the direction in which the movement of the vehicle body <NUM> is prevented. The driving force to the driving wheels <NUM> and <NUM> is cut off in the travel limitation state S12 so as to stop the forklift <NUM>. In the limitation start state S23, engine braking decelerates the forklift <NUM> because the forklift <NUM> does not need to be stopped. That is, the forklift <NUM> is decelerated according to the situation.

(<NUM>) The main controller <NUM> extends the predicted trajectory T in the traveling direction as the vehicle speed of the vehicle body <NUM> increases. The amount of time it takes for the vehicle body <NUM> to reach the object is decreases as the vehicle speed of the vehicle body <NUM> increases. This achieves an appropriate vehicle speed limitation which corresponds to the vehicle speed of the vehicle body <NUM>.

The embodiment may be modified as below. The embodiment and modifications below may be combined with each other within a range in which a technical contradiction does not arise.

The brake actuator <NUM> is an actuator that controls hydraulic oil supplied to the brake wheel cylinders <NUM>. The brake actuator <NUM> controls the supply of the hydraulic oil by a solenoid valve, for example.

The brake wheel cylinders <NUM> are respectively provided in the driving wheels <NUM> and <NUM>. Alternatively, the brake wheel cylinders <NUM> may be respectively provided in the steered wheels <NUM>. Each of the brake wheel cylinders <NUM> presses brake pads against a brake disc by using the hydraulic oil supplied from the brake actuator <NUM> so as to generate a friction braking force.

The hardware configuration of the brake controller <NUM> is similar to that of the travel controller <NUM>, for example. The brake controller <NUM> controls the brake actuator <NUM> in accordance with a command from the main controller <NUM>. In other words, the main controller <NUM> controls the brake mechanism <NUM> by transmitting a command to the brake controller <NUM>.

The main controller <NUM> performs deceleration by the brake mechanism <NUM> in addition to deceleration by the running resistance, thereby preventing the vehicle speed of the vehicle body <NUM> from exceeding the vehicle-speed upper-limit value. For example, when the forklift <NUM> is decelerated in the travel limitation state S12, the main controller <NUM> cuts off the driving force to the driving wheels <NUM> and <NUM> by transmitting a cut-off command to the travel controller <NUM>. The main controller <NUM> also transmits a braking command to the brake controller <NUM>. Upon receiving the braking command, the brake controller <NUM> controls the brake actuator <NUM> so that hydraulic oil is supplied to the brake wheel cylinders <NUM>. The brake controller <NUM> performs control so that the deceleration rate of the forklift <NUM> becomes equal to or less than a deceleration rate limitation value [m/s<NUM>] determined in advance. The deceleration rate limitation value is a value larger than <NUM> and lower than the maximum deceleration rate of the forklift <NUM>. As a result, the load collapse at the time of deceleration is suppressed. The forklift <NUM> is decelerated at a deceleration rate equal to or less than the deceleration rate limitation value and the forklift <NUM> then stops.

The main controller <NUM> performs deceleration by the brake mechanism <NUM> in addition to deceleration by engine braking, thereby preventing the vehicle speed of the vehicle body <NUM> from exceeding the vehicle-speed upper-limit value. For example, in the vehicle speed limitation control for an obstacle, when the forklift <NUM> is decelerated in the limitation start state S23, the main controller <NUM> causes engine braking to act by transmitting a rotational speed command to the travel controller <NUM>. The main controller <NUM> also transmits a braking command to the brake controller <NUM>. The brake controller <NUM> performs control so that the deceleration rate of the forklift <NUM> becomes equal to or less than the deceleration rate limitation value [m/s<NUM>] determined in advance.

Providing the brake mechanism <NUM> allows the deceleration rate of the forklift <NUM> to be adjusted. Providing the brake mechanism <NUM> further allows the forklift <NUM> to stop during the forklift <NUM> is moving on a ramp.

When the forklift <NUM> includes the brake mechanism <NUM>, the deceleration rate at the time of deceleration of the forklift <NUM> may be a value that decreases as the weight of the load increases. In this case, the forklift <NUM> is decelerated more gradually as the weight of the load increases. Similarly, when the forklift <NUM> includes the brake mechanism <NUM>, the deceleration rate at the time of deceleration of the forklift <NUM> may be a value that decreases as the lifting height of the load handling apparatus <NUM> increases. In this case, the forklift <NUM> is decelerated more gradually as the lifting height of the load handling apparatus <NUM> increases. When the forklift <NUM> includes the brake mechanism <NUM>, the deceleration rate at the time of deceleration of the forklift <NUM> may be a value that decreases as the lifting height of the load handling apparatus <NUM> increases and also decreases as the weight of the load increases.

The main controller <NUM> may combine the deceleration by engine braking and the abovementioned deceleration by the brake mechanism <NUM> with each other. That is, the deceleration by engine braking and the deceleration by the brake mechanism <NUM> may be performed in both of the travel limitation state S12 and the limitation start state S23 for an obstacle. In this case, the main controller <NUM> does not perform control to cut off the driving force to the driving wheels <NUM> and <NUM>.

The main controller <NUM> may combine the deceleration by the running resistance and the abovementioned deceleration by the brake mechanism <NUM> with each other. That is, the deceleration by the running resistance and the deceleration by the brake mechanism <NUM> may be performed in both of the travel limitation state S12 and the limitation start state S23 for an obstacle. In this case, the main controller <NUM> does not perform control of setting a limitation value to the target rotational speed of the engine <NUM>.

The object detector <NUM> may detect the position of an object existing in either the backward movement direction or the forward movement direction, which is one of the directions of movement of the vehicle body <NUM>. In this case, the object existing in either the backward movement direction or the forward movement direction, which is one of the directions of movement of the vehicle body <NUM>, may be detected by a single object detector <NUM>, or may be detected by two object detectors <NUM> respectively for the forward movement direction and for the backward movement direction. When the forklift <NUM> is moving forward, the vehicle speed limitation is imposed according to the position of an object existing in the forward movement direction. When the forklift <NUM> is moving backward, the vehicle speed limitation is imposed according to the position of an object existing in the backward movement direction. That is, the main controller <NUM> sets a vehicle-speed upper-limit value when the traveling direction of the vehicle body <NUM> is a direction toward the object detected by the object detector <NUM>.

The object detector <NUM> may include a sensor that measures the coordinates of an object on an X-Y plane that is a coordinate plane expressing a horizontal plane instead of the stereo camera <NUM>. That is, a sensor that measures two-dimensional coordinates of an object may be used as the sensor. As this kind of sensor, for example, two-dimensional LIDAR that performs laser illumination from various angles in the horizontal direction may be used.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Claim 1:
An engine-type industrial vehicle (<NUM>), comprising:
a vehicle body (<NUM>);
an engine (<NUM>);
a power transmission (<NUM>) configured to transmit a driving force of the engine (<NUM>) to a driving wheel (<NUM>, <NUM>);
a main controller (<NUM>) configured to adjust the driving force to be transmitted to the driving wheel (<NUM>, <NUM>);
an object detector (<NUM>) configured to detect a position of an object that exists in a traveling direction of the vehicle body (<NUM>);
a predicted trajectory calculator (<NUM>) configured to derive a predicted trajectory (T) that is a trajectory predicted to be followed by the vehicle body (<NUM>); and
a vehicle-speed upper-limit setter (<NUM>) configured to impose a vehicle speed limitation on the vehicle body (<NUM>) by setting a vehicle-speed upper-limit value when the object detected by the object detector (<NUM>) is positioned on the predicted trajectory (T) and the traveling direction of the vehicle body (<NUM>) is a direction toward the object, characterized in that
the main controller (<NUM>) is configured to prevent a vehicle speed of the vehicle body (<NUM>) from exceeding the vehicle-speed upper-limit value by performing at least one of a control so that the vehicle is decelerated by engine braking or a control so that the driving force to the driving wheel (<NUM>, <NUM>) is cut off.