Abstract:
A automatic traveling vehicle that may travel at high speed along a predetermined course without colliding or interfering with detected objects within the course. The vehicle radiates a directional medium and analyzes any reflections to determined the presence of objects along the course. The vehicle combines predetermined, stored information with currently detected information to ensure the farthest possible distance for object detection and increased reliability for preventing collision and interference with detected objects.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an automatic traveling vehicle, and in particular, to an automatic traveling vehicle with an object detector that can travel at high speed without colliding or interfering with a detected object. 
     BACKGROUND OF THE INVENTION 
     There exists an automatic traveling vehicle comprising a directional medium receiver and transmitter means to radiate a directional medium (for example, light, a millimeter wave, or an ultrasonic wave) and receive a reflected wave from an object in a direction consistent with vehicle travel; an actuator for changing the direction of radiation of the directional medium, which is mounted on the directional medium receiver and transmitter means; and an object detector for analyzing an object detection status after receiving a reflected wave from an object transmitted by the directional medium receiver and transmitter means. 
     The directional medium receiver and transmitter means comprises a light transmitting unit and a light receiving unit if the directional medium is light, for example, or comprises a transmitting and receiving antenna if the directional medium is a millimeter wave or an ultrasonic wave. The actuator for changing the direction of radiation of the directional medium is a scanner which allows the directional medium to be directed at an angle within a predetermined angular range by, for example, pivoting the directional medium receiver and transmitter means. The object detector receives reception and transmission information (in other words, a frequency, a reception and transmission strength, and the like) regarding the directional medium produced and received by the directional medium receiver and transmitter means. The object detector further analyzes an object detection status (in other words, whether or not any object is detected, a distance to an object, a relative speed to an object, and the like). The analysis results are entered into a separate control unit having a stored control program. In accordance with the control program, the control unit controls the speed of the vehicle by operating an alarm or by operating a vehicle speed control actuator (for example, an accelerator or a brake). This prevents the vehicle from colliding with the detected object and from interfering with it. 
     Japanese Unexamined Patent Publication (A) No. 5-203746 discloses an actuator for changing the direction of radiation of the directional medium based on a steering operation, where a directional medium receiver and transmitter means is rotated so as to match a directional medium with a steering angle. This actuator has the following problems. 
     (1) In a curved course Cc, as shown in FIG. 7, a directional medium A is emitted along a curvature of the curved course Cc in accordance with a steering angle. A detection area to be treated by an object detector is area AC 1 , formed by overlapping regions of a directional medium A and the indicated area XC of course C followed by vehicle  1 , which does not include areas further along course Cc. 
     (2) In an irregularly curved course Cs, as shown in FIG. 8, a directional medium A is emitted along a curvature of a first curve Cc. Due to steering angle limitations, a detection area AC 1  does not include areas further along course Cs. 
     (3) In a straight course Ct, as shown in FIG. 9, supposing a misaligned vehicle  1  is subject to a steering operation to return the vehicle  1  to the center of course Ct, the steering angle causes a radiated directional medium A to be directed toward the edge of course Ct. Thus, a detection area AC 1  does not include areas further along course Ct. 
     In this type of an automatic traveling vehicle, a vehicle control and other operations are performed on the basis of the effective detection area AC 2 , and the effective detection area AC 2  is often a short distance; therefore, control of the vehicle  1  is forced to be performed at a low speed. Accordingly, for an unmanned dump truck that must travel, for example, in a mine, improved productivity cannot be expected. 
     For any of the above cases, an effective detection area AC 2  may extend further than the detection area AC 1  if the directional medium A is pivoted by an actuator for changing the direction of radiation of the directional medium. The region defined by reference character X (see FIGS.  7 - 9 ), or the critical detection region X, designates the maximum pivoting range of the directional medium A using an actuator for changing the direction of radiation of the directional medium. 
     SUMMARY OF THE INVENTION 
     In view of these problems in the prior art, it is an object of the present invention to provide an automatic traveling vehicle with an object detector which can travel at high speed in a predetermined course without colliding or interfering with an object detected by an object detector. 
     According to a first aspect the present invention, there is provided an automatic traveling vehicle with an object detector having a directional medium receiver and transmitter means for radiating a directional medium (for example, light, a millimeter wave, or an ultrasonic wave) in a traveling direction of the automatic traveling vehicle and receiving a reflected wave from an object; an actuator for changing the direction of radiation of the directional medium, and an object detector for analyzing an object detection status after receiving a reflected wave from an object transmitted by the directional medium receiver and transmitter means. The automatic traveling vehicle further includes a predetermined course storage means for storing a predetermined course in a coordinate system; a critical detection area storage means for storing a critical detection area in a coordinate system, the critical detection area being created by direction of the directional medium through a maximum angular range using the actuator for changing the direction of radiation of the directional medium; a current position determining means for determining the current portion of the automatic traveling vehicle in the predetermined course based on course information from the predetermined course storage means; and a calculator means. 
     The calculator means receives course information from the predetermined course storage means, critical detection area information from the critical detection area storage means, and the current position information of the automatic traveling vehicle from the current position determining means. Using this information, the calculator means determines the farthest portion from the current position of the automatic traveling vehicle in a region defined by the overlapped areas of the critical detection area and the predetermined course. The calculator then outputs a signal to the actuator for changing the direction of radiation of the directional medium so that a radiated direction of the directional medium corresponds to the farthest portion. 
     According to the above configuration, the automatic traveling vehicle is capable of evaluating the greatest effective detection area. Thus, the automatic traveling vehicle can travel at high speed without colliding or interfering with a detected object. 
     According to a second aspect of the present invention based on the first aspect thereof, an automatic traveling vehicle includes each of the features set forth above. The automatic traveling vehicle further includes a vehicle speed control actuator to control the speed of the automatic traveling vehicle; an actual vehicle speed detector means to detect an actual vehicle speed; and a predetermined vehicle speed storage means to store predetermined vehicle speed information for each position along the predetermined course. 
     The calculator means receives actual vehicle speed information from the actual vehicle speed detector means and predetermined vehicle speed information from the predetermined vehicle speed storage means. The calculator outputs an operation signal to the vehicle speed control actuator so that the actual vehicle speed matches the predetermined vehicle speed information, calculates a distance from the current position of the automatic traveling vehicle to the calculated farthest portion, calculates a vehicle speed at which the vehicle can stop in this distance, and renews the predetermined vehicle speed information in the predetermined vehicle speed storage means to a vehicle speed equal to or lower than this vehicle speed. 
     According to this configuration, a predetermined vehicle speed is automatically renewed to a vehicle speed at which a vehicle can stop in a detected distance. Thus, the automatic traveling vehicle can be controlled more reliably from colliding or interfering with a detected object. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings in which like reference numerals and letters indicate corresponding elements throughout the several views, if applicable: 
     FIG. 1 is a control block diagram for an automatic traveling vehicle with an object detector according to an embodiment of the present invention; 
     FIG. 2 is an explanatory diagram of an example of an object detecting operation according to the embodiment; 
     FIG. 3 is an operational flowchart of an object detection according to the embodiment; 
     FIG. 4 is an operational explanatory diagram for an object detection in a curved course according to the embodiment; 
     FIG. 5 is an operational explanatory diagram in an irregularly curved course according to the embodiment; 
     FIG. 6 is an operational explanatory diagram in a straight course according to the embodiment; 
     FIG. 7 is an operational explanatory diagram for conventional object detection for a curved course; 
     FIG. 8 is an operational explanatory diagram for conventional object detection for an irregularly curved course; and 
     FIG. 9 is an operational explanatory diagram for conventional object detection for a straight course. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An automatic traveling vehicle with an object detector (hereinafter, a “vehicle”) according to an embodiment of the present invention will be described below in reference to FIGS. 1 to  6 . A vehicle of this embodiment is an unmanned dump truck which travels in a predetermined course in a mine or a construction site or the like. 
     As shown in FIG. 1, the vehicle  1  comprises a directional medium receiver and transmitter means  2 , an actuator for changing the direction of radiation of the directional medium  3 , an object detector  4 , a predetermined course storage means  5 , a critical detection area storage means  6 , a current position determining means  7 , a vehicle speed control actuator  8 , an actual vehicle speed detector means  9 , a predetermined vehicle speed storage means  10 , and a calculator means  11 . 
     The directional medium receiver and transmitter means  2  is a transmitting and receiving antenna for receiving and transmitting millimeter waves (i.e., directional medium A). However, the directional medium receiver and transmitter means  2  may be of such form so as to radiate, for example, light, ultrasonic waves, or the like. 
     The actuator for changing the direction of radiation of the directional medium  3  is a pulse motor having a servo-control mechanism, which is operatively mounted to the directional medium receiver and transmitter means  2 . The actuator  3  allows the directional medium receiver and transmitter means  2  to be freely scanned within an angular range in a horizontal direction or fixed at a desired angle within the angular range, thus allowing the radiated direction of the directional medium A to be controlled in like manner. The actuator  3  is controlled by the calculator means  11  (as described below), and in particular, operation signal θ (a target value) for servo control is entered into a servo control mechanism of the actuator  3  from calculator means  11 . Operationally, an actual radiation angle (or radiation range) for the directional medium A is equal to a target radiation angle specified by the operation signal θ (or so that it is scanned within the target radiation range). 
     The object detector  4  receives reception and transmission information (in other words, a frequency, a reception and transmission strength, and the like) regarding the directional medium A produced and received by the directional medium receiver and transmitter means  2 . The object detector  4  further analyzes an object detection status (in other words, whether or not any object is detected, a distance L to an object, a relative speed to an object, and the like). The detected information is sent to the calculator means  11 . 
     As to a millimeter wave system, a signal wave (normally a triangular wave) put on a millimeter wave is radiated from a transmitting antenna in a traveling direction of the vehicle  1 , and a reflected wave from an object is received by a receiving antenna. Phases of these transmitted and received waves and wave reception strengths are treated in a pulse system, a two-frequency CW system, and an FM-CW system. In addition, a frequency analysis (for example, a filter bank or a fast Fourier transform [FFT]) is performed to calculate respective distances for a plurality of objects detected simultaneously, together with relative speeds. 
     The predetermined course storage means  5  is a memory which stores an entire shape of a predetermined course C, including a direction, a distance, and a gradient for a desired interval, in a coordinate system. The information stored in the predetermined course storage means  5  is supplied to the calculator means  11  and the current position determining means  7 . 
     The critical detection area storage means  6  is also a memory, in which a critical detection area X is stored in a coordinate system. The critical detection area X is a value specific to the actuator for changing the direction of radiation of the directional medium  3  and is independent of the predetermined course C. The information stored in the critical detection area storage means is supplied to the calculator means  11 . 
     From information received from the predetermined course storage means  5 , the current position determining means  7  determines a current position Po and a current traveling direction of the vehicle  1 . The current position determining means  7  may include a gyro, a position information transmitting or receiving system to indicate key places along actual course C, a global positioning system (GPS), or other various devices. 
     The vehicle speed control actuator  8  is an accelerator or a brake having a servo mechanism capable of freely changing the actual speed of the vehicle  1 . Calculator means  11  supplies an operation signal S to the servo mechanism of the vehicle speed control actuator  8 . As an operational example, as an actual vehicle speed (Va) becomes equal to a predetermined vehicle speed (Vs), the operation signal S is gradually decreased. 
     While a servo calculation of the actuator  3  is processed in the servo-control mechanism of the actuator  3  (as described above), a servo calculation for the vehicle speed control actuator  8  is performed in the calculator means  11 , as the actual vehicle speed detector means  9  and the calculator means  11  are connected with each other for servo control of the vehicle speed control actuator  8 . Naturally, if the actual vehicle speed detector means  9  were connected to a servo mechanism of the vehicle speed control actuator  8  in another configuration of a servo control mechanism, the calculator means  11  would enter the operation signal S into the servo control mechanism simply as a target value in the same manner as for the servo control mechanism of the actuator  3 . Regardless, either configuration may be used. 
     While an accelerator or a brake is operated by an operator in a manual vehicle, the speed of the vehicle  1  may be automatically controlled on the basis of an operating program in the calculator means  11 . 
     The actual vehicle speed detection means  9  is a vehicle speed indicator, which detects an actual vehicle speed (Va) of the vehicle  1 . The actual vehicle speed detection means  9  supplies detected speed information to the calculator means  11 . 
     The vehicle speed storage means  10  is also a memory, which stores information on a predetermined vehicle speed (Vs) for each position along the predetermined course C. In this embodiment, the vehicle speed storage means  10  also stores a vehicle speed control program for calculating an automatic vehicle speed control by means of the calculator means  11  using a predetermined vehicle speed (Vs). 
     The calculator means  11  is, for example, a microcomputer, which receives information from the components identified above. As a summary of information, the calculator means  11  receives analysis result (e.g., whether or not an object is detected, a distance L to an object, a relative speed to an object, and the like) from the object detector  4 , information on the predetermined course C from the predetermined course storage means  5 , a critical detection area X from the critical detection area storage means  6 , a current position Po or a traveling direction of the vehicle  1  from the current position determining means  7 , and an actual vehicle speed (Va) from the actual vehicle speed detector means  9 . The calculator means  11  also outputs information. Specifically, the calculator means  11  outputs an operation signal θ to the actuator for changing the direction of radiation of the directional medium  3  and an operation signal S to the vehicle speed control actuator  8 . Furthermore, it can freely read a predetermined vehicle speed (Vs) signal from the predetermined vehicle speed storage means  10  and write a signal therein. 
     The calculator means  11  has a memory  111  indicated by a frame outlined by a dashed line in FIG.  1 . Memory  111  stores braking start-time vehicle speed (Vb) information for every braking stop distance (Lb). The braking start-time vehicle speed (Vb) is equal to a certain actual vehicle speed (Va). The braking stop distance (Lb) is a braking distance needed to stop the vehicle  1  by hard braking plus a predetermined safety distance (for example, 10 m) when the vehicle  1  traveling at an actual vehicle speed (Va). Variables (Lb) and (Vb) are stored in the memory  111  in as a function (e.g., Vb=f(Lb)) or as a matrix (e.g., Lb→Vb). Memory  111  further stores a vehicle speed control program and an operating program. The calculator means  11  may freely read any information stored in memory  111 . 
     An example of an operating program with the calculator means  11  will be described below by reference to FIG.  3 . The operating program illustrated in FIG. 3 represents only a main portion. 
     In step al, the calculator means  11  stores a braking start-time vehicle speed (Vb) for every braking stop distance Lb and a vehicle speed control program in addition to this operating program in the memory  111 . 
     In step a 2 , the calculator means  11  receives signals such as a predetermined vehicle speed (Vs) from the predetermined vehicle speed storage means  10 , a critical detection area X from the critical detection area storage means  6 , and predetermined course C information from the predetermined course storage means  5 , as specific values, while the vehicle  1  is traveling. As detection values, the calculator means  11  receives actual vehicle speed (Va) values from the actual vehicle speed detector means  9  and a current position Po (or a traveling direction) of the vehicle  1  from the current position determining means  7 . As discussed above, calculator means  11  also receives an analysis result from the object detector  4  (not shown). 
     In step a 31 , the calculator means  11  outputs an operation signal S to the servo mechanism of the vehicle speed control actuator  8  in accordance with the vehicle speed control program, so that the actual vehicle speed (Va) is equal to the predetermined vehicle speed (Vs). By this operation, the vehicle  1  travels along the predetermined course C automatically at the predetermined vehicle speed (Vs). While the vehicle  1  is, for example, an unmanned dump truck, the vehicle speed control program contains a steering control program and the like and therefore it can travel automatically along the predetermined course. 
     Steps a 3  and a 4  are performed in parallel with step a 31 , while steps a 41  to a 43  are performed in parallel with step a 4 . 
     Step a 3  will be described in reference to FIG.  2 . The calculator means  11  first calculates an area XC (a hatched area covered by oblique lines with right-hand ends upward as shown) consisting of the overlapped areas of the critical detection area X (viewed from the current position Po of the vehicle  1 ) and the predetermined course C. The calculator means  11  then calculates the farthest portion Pmax from the current position Po of the vehicle  1  in the overlapped area XC. The overlapped area XC and the farthest portion Pmax are calculated geometrically since information on the predetermined course C and the critical detection area X is stored in a coordinate system. 
     Step a 4  will also be described in reference to FIG.  2 . The calculator means  11  outputs an operation signal θ (a target value) to the servo-control mechanism of the actuator for changing the direction of radiation of the directional medium  3  so that the radiated direction of the directional medium A matches a direction to the farthest portion Pmax. 
     In step a 41 , the calculator means  11  calculates a distance Lmax from the current position Po of the vehicle  1  to the farthest portion Pmax (after determining the farthest portion Pmax in the step a 3 ). Alternatively, there is a calculation method in which a plurality of distances L are compared with each other in the calculation of the farthest portion Pmax (step a 3 ) to determine a position which corresponds to the longest distance among them, the longest distance is then designated as the farthest portion Pmax. In this calculation method, a distance Lmax need not be obtained from the farthest portion Pmax, rather the longest distance obtained in the process for calculating the farthest portion Pmax may be treated as distance Lmax. 
     In step a 42 , the calculator means  11  reads out the braking start-time vehicle speed (Vb) for every braking stop distance (Lb) stored in the memory  111 , extracts a braking stop distance (Lb) equal to the distance Lmax, and then calculates/obtains the braking start-time vehicle speed (Vb) corresponding to the braking stop distance (Lb). In the memory  111 , if both of the variables (Lb) and (Vb) are stored in a function (Vb=f(Lb)), the braking start-time vehicle speed (Vb) is obtained by a calculation, while if the variables (Lb) and (Vb) are stored in a matrix (Lb→Vb), the braking start-time vehicle speed (Vb) is obtained from the matrix. 
     In step a 43 , the calculator means  11  sets the currently-used predetermined vehicle speed (Vs) of the automatic vehicle  1  to the braking start-time vehicle speed (Vb) calculated/obtained in step a 42  or a lower value. In other words, automatic teaching is performed during operation. Accordingly, the vehicle  1  is controlled to prevent collision or interference with detected objects more reliably. 
     According to this embodiment, the radiated direction of the directional medium A becomes equal to the farthest portion Pmax predetermined course C in the step a 4 . Therefore, it is possible to obtain actions and effects as shown in FIGS. 4 to  6 . 
     For comparison with conventional methods illustrated in FIG. 7, FIG. 4 shows a directional medium A radiated to the farthest portion Pmax 2  of overlapped area XC (i.e., an area defined by the overlapping critical detection area X and course C) for a curved course Cc. In comparison with FIG. 7, the detection AC 2  is larger than the detection area AC 1 . 
     Of note, the detection area AC 2  can be furthered to, for example, a detection area AC 3 . If there is any construction, a mountain, or a steep cliff inside the curved course Cc (i.e., the lower portion in the drawing), it may be previously stored in the predetermined course storage means  5  so as to create an operating program in which the farthest portion Pmax 2  is set to Pmax 1 . 
     For comparison with conventional techniques illustrated in FIG. 8, FIG. 5 shows a directional medium A radiated to the farthest portion Pmax of overlapped area XC for the irregularly curved course Cs. In comparing FIG. 8, the detection area AC 2  is larger than the detection area AC 1 . 
     For comparison with conventional methods illustrated in FIG. 9, FIG. 6 shows a directional medium A radiated to the farthest portion Pmax of the overlapped area XC for a straight course Ct. As before, supposing that the illustrated vehicle  1  is traveling toward the edge of the road (for example, to align the vehicle  1  with the center of course C) due to a steering operation, the detection area AC 3  to be processed by the object detector  4  is unaffected by the steering operation and remains directed to Pmax. The calculator means  11  can receive object detection information on the detection area AC 3  which is the greatest distance from the object detector  4  (and significantly greater than detection area AC 1  of FIG.  6 ), thus allowing the vehicle  1  to travel at high speed along course Ct. 
     Next, application examples of this embodiment are outlined below: 
     (1) While the calculator means  11  directs the directional medium A toward a direction of the farthest portion Pmax in the operating program of this embodiment, a range in the vicinity of the farthest portion Pmax of the overlapped area XC may be scanned if the directional medium A is thin enough. The operation signal θ 1  in this case is assumed to be: θ 1 =θ±Δθ, where 2·Δθ is a scanning width. 
     (2) While the actuator for changing the direction of radiation of the directional medium  3  is pivoted in a horizontal direction in the operating program in this embodiment, it may be pivoted vertically in correspondence with a course C having an upward slope or a downward slope. 
     (3) While the predetermined course storage means  5 , the critical detection area storage means  6 , and the set vehicle speed storage means  10  are discriminated from the memory  111  of the calculator means  11  in this embodiment, they may be integrated into the memory  111 .