Carrier vehicle

Abstract

To provide a carrier vehicle capable of detecting an abnormality at a reduced cost without complicating a circuit configuration.SOLUTION: A carrier vehicle 1 comprises: a servo driver 4 which supplies a driving voltage to a motor based on a target value for the motor included in a movement mechanism of a vehicle body; an encoder which detects an operation state of the motor and feeds the operation state back to the servo driver 4; and an abnormality detection unit that detects an abnormality in a path that feeds back a detection value of the encoder from the encoder to the servo driver 4 based on the target value and the detection values of the encoder.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an autonomously driven guided vehicle. [Background technology]

[0002] Patent Document 1 below discloses an automatic guided vehicle (AGV) that transports materials at manufacturing sites and the like. This automatic guided vehicle is provided with a monitoring area that detects the presence or absence of an entering object using a laser sensor mounted at the tip of the automatic guided vehicle. When an object enters this monitoring area, the automatic guided vehicle stops. This monitoring area is set variably according to the speed and acceleration of the automatic guided vehicle calculated based on signals from encoders attached to the wheel axles. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6393523 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in the automated guided vehicle of Patent Document 1, a circuit including a microcomputer that processes signals from an encoder attached to the axle of the wheels is duplicated for fail-safe purposes. The processing results of both duplicated microcomputers are compared, and if they do not match, an abnormality caused by an encoder failure is detected. However, duplicating a circuit including a microcomputer complicates the circuit configuration and causes costs to increase.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a transport vehicle that can detect abnormalities without complicating the circuit configuration and while keeping costs down. [Means for solving the problem]

[0006] A transport vehicle according to one embodiment of the present invention comprises a servo driver that supplies a drive voltage to a motor based on a target value for the motor included in a vehicle body's movement mechanism, an encoder that detects the operating status of the motor and feeds it back to the servo driver, and an abnormality detection unit that detects an abnormality in the path that feeds back the encoder's detection value to the servo driver based on the target value and the encoder's detection value.

[0007] According to this aspect, it is possible to easily detect an abnormality in the path for feeding back the encoder detection value by using the target value for the motor and the encoder detection value indicating the operating status of the motor, which are obtained by the circuit configuration included in the conventional servo system.

[0008] In the above aspect, the abnormality detection unit may detect that there is an abnormality in the path that feeds back the encoder detection value from the encoder to the servo driver when the target value is equal to or greater than a predetermined value and the encoder detection value does not change for a predetermined period of time.

[0009] According to this aspect, if a target value equal to or greater than a predetermined value is output to the motor but the detection value of the encoder does not change, it is possible to detect that there is an abnormality in the path for feeding back the detection value of the encoder.

[0010] In the above aspect, the abnormality detection unit may determine that the detection value of the encoder has not changed for a predetermined time when a state in which there is no difference between the current detection value of the encoder and the previous detection value of the encoder continues for a predetermined time or more.

[0011] According to this aspect, if a target value equal to or greater than a predetermined value is output to the motor, but the encoder detection value continues to show no difference from the previous time, it is possible to detect that there is an abnormality in the path for feeding back the encoder detection value.

[0012] In the above aspect, the abnormality detection unit may further include, as a condition for detecting that there is an abnormality in the path that feeds back the encoder detection value from the encoder to the servo driver, that a drive voltage is being supplied to the motor.

[0013] According to this aspect, if a target value equal to or greater than a predetermined value is output to the motor and a drive voltage is supplied to the motor, but the encoder detection value does not change, it is possible to detect that there is an abnormality in the path that feeds back the encoder detection value.

[0014] In the above aspect, there may be a plurality of pairs of motor and encoder, and the abnormality detection unit may detect, for each pair, that there is an abnormality in a path that feeds back the detection value of the encoder from the encoder to the servo driver.

[0015] According to this aspect, it is possible to detect, for each pair of a motor and an encoder, the presence of an abnormality in the path for feeding back the detected value of the encoder. Effect of the Invention

[0016] According to the present invention, it is possible to provide a transport vehicle that can detect abnormalities without complicating the circuit configuration and while keeping costs down. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a transport vehicle according to an embodiment, viewed from directly above; [Diagram 2] FIG. 1 is a schematic diagram showing a transport vehicle provided with a virtual bumper as viewed from directly above. [Diagram 3] FIG. 2 is a block diagram illustrating a physical configuration of a transportation vehicle. [Figure 4] FIG. 2 is a block diagram illustrating a functional configuration of a transportation vehicle. [Diagram 5] 10 is a flowchart for explaining an example of an operation of a transportation vehicle according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like or similar structures.

[0019] 1 is a schematic diagram of a transport vehicle 1 according to an embodiment, viewed from directly above. The transport vehicle 1 is an autonomously travelling device, and may be, for example, a transport platform vehicle that transports luggage or the like placed on the vehicle body, or a transport robot that transports luggage or the like. In this embodiment, a case where the transport vehicle 1 is a transport platform vehicle will be described as an example. The transport vehicle 1 can move in all directions 360 degrees automatically or manually.

[0020] The transport vehicle 1 is equipped with two sensors 2a and 2b. The sensors 2a and 2b are sensors that measure the distance to an object, and are, for example, a laser scanner, a Time Of Flight (TOF) sensor, a Light Detection and Ranging (LiDAR) sensor, etc. In this embodiment, a case will be described in which the sensors 2a and 2b are laser scanners that can scan a range of 270 degrees with laser light.

[0021] The scanning range Ra of the sensor 2a and the scanning range Rb of the sensor 2b partially overlap each other, and by combining the two scanning ranges, it is possible to scan the entire periphery of the transport vehicle 1. This makes it possible to detect objects that may be present around the transport vehicle 1 (in all directions).

[0022] The number of sensors mounted on the transport vehicle 1 is not limited to two, and may be one, or three or more. It is sufficient that the mounted sensor can detect objects present in all directions in which the transport vehicle 1 can move. Objects include, for example, passage walls, shelves and pipes arranged in the passage, other transport vehicles and people present in the passage, etc.

[0023] As shown in FIG. 2, the transport vehicle 1 is provided with a virtual bumper B around the vehicle body. The virtual bumper B is a virtual area formed within the scanning ranges Ra, Rb of the two sensors 2a, 2b, and is a protective area to prevent collision with objects. When an object is detected within the range of the virtual bumper B, the transport vehicle 1 stops. In other words, when an object detected by the sensors 2a, 2b is present within the range of the virtual bumper B, the transport vehicle 1 stops. By forming the virtual bumper B within the scanning ranges Ra, Rb of the sensors 2a, 2b, an object present within the range of the virtual bumper B can be detected using the measurement results of the sensors 2a, 2b.

[0024] It is preferable that the width W by which the virtual bumper B projects from the periphery of the vehicle body (hereinafter also referred to as the "virtual bumper width") be set to a length that ensures a distance that allows the vehicle body to stop without colliding with an object detected within the range of the virtual bumper B. This makes it possible to reliably stop the vehicle body without colliding with an object detected within the range of the virtual bumper B.

[0025] The physical configuration of the transport vehicle 1 will be described with reference to Fig. 3. As shown in the figure, the transport vehicle 1 includes, as its physical configuration, for example, two sensors 2a and 2b, a PLC (Programmable Logic Controller) 3, a servo driver 4, and four servo motors 5a, 5b, 5c, and 5d. The PLC 3, the servo driver 4, and the servo motors 5a, 5b, 5c, and 5d constitute a servo system.

[0026] Each of the sensors 2a and 2b is a distance measuring sensor that measures the distance to an object existing around the transport vehicle 1. The PLC 3 is a control device that controls each part of the transport vehicle 1. The number of PLCs 3 is not limited to one, and multiple PLCs may be provided depending on the roles of the motors. The servo driver 4 supplies a drive voltage to the motor so that the motor follows a target value such as a speed command for the motor output from a controller such as the PLC 3, and controls the position, speed, output torque, etc. of the motor.

[0027] Each of the servo motors 5a, 5b, 5c, and 5d includes a motor that drives a wheel and an encoder that detects the operating status of the motor. The wheel is a wheel that can move in all directions, and for example, an omniwheel can be used. The encoder feeds back the detected operating status of the motor to the servo driver 4. The servo driver 4 compares a target value output from the controller with a value fed back from the encoder, and controls the motor so that they match.

[0028] The functional configuration of the transport vehicle 1 will be described with reference to Fig. 4. As shown in the figure, the transport vehicle 1 includes, as its functional configuration, for example, a protection area setting unit 11, an abnormality detection unit 12, an object detection unit 13, and a stop control unit 14.

[0029] The protection area setting unit 11 provides a virtual bumper B around the vehicle body in accordance with, for example, an operational instruction from an operator. The virtual bumper B is a virtual area, and has a function of stopping the vehicle body when an object is detected within this area.

[0030] The abnormality detection unit 12 detects that there is an abnormality in the path (hereinafter also referred to as the "feedback path") that feeds back the encoder detection value to the servo driver 4 based on the speed command value for the motor output from the controller and the detection value output from the encoder.

[0031] Specifically, the abnormality detection unit 12 detects that an abnormality exists in the feedback path when the speed command value is equal to or greater than a predetermined value and the detected value of the encoder does not change for a predetermined time.

[0032] An example of a case where the detection value of the encoder does not change for a predetermined period of time is a case where the current detection value of the encoder and the previous detection value of the encoder are the same for a predetermined period of time or more. The state where there is no difference includes a case where the current detection value and the previous detection value are the same, as well as a case where the current detection value and the previous detection value are substantially the same (for example, within an error range where it can be determined that there is no change).

[0033] Furthermore, the condition for the abnormality detection unit 12 to detect the presence of an abnormality in the feedback path may further include that a drive voltage is being supplied to the motor.

[0034] Furthermore, when the abnormality detection unit 12 detects that there is an abnormality in the feedback path, it may notify an operator of the abnormality by, for example, sounding an alarm or turning on a warning light.

[0035] The command value output from the controller is not limited to a speed command value, but may be a target value for the motor including a position command value or the like.

[0036] The object detection unit 13 detects that an object is present within the virtual bumper B based on the distance to the object measured by the sensors 2a and 2b.

[0037] Specifically, when the distance to the object falls within the range of virtual bumper B, object detection unit 13 detects that the object is present within virtual bumper B. On the other hand, when the distance to the object exceeds the range of virtual bumper B, object detection unit 13 does not detect that the object is present within virtual bumper B.

[0038] When the object detection unit 13 detects an object within the virtual bumper B, the stop control unit 14 stops driving the motor to stop the vehicle body.

[0039] Next, an example of the operation of the transport vehicle 1 according to the embodiment will be described with reference to FIG.

[0040] First, the controller of the transportation vehicle 1 outputs a speed command value, which is a target value for the motor, to the servo driver 4 (step S101).

[0041] Next, the servo driver 4 of the transportation vehicle 1 supplies a drive voltage to the motor based on the speed command value output in the above step S101 (step S102).

[0042] Next, the encoder of the transportation vehicle 1 detects the operating state of the motor operated by the drive voltage supplied in the above step S102, and feeds back the detected value to the servo driver 4 (step S103).

[0043] Here, the servo driver 4 of the transportation vehicle 1 supplies a drive voltage to the motor based on the value fed back in the above step S103 and the speed command value output in the above step S101 (step S102).

[0044] Next, the abnormality detection unit 12 of the transportation vehicle 1 judges whether the speed command value output in the above step S101 is equal to or greater than a predetermined value (step S104). If this judgment is NO (step S104; NO), the process proceeds to step S101.

[0045] When it is determined in the above step S104 that the speed command value is equal to or greater than the predetermined value (step S104; YES), the abnormality detection unit 12 of the transport vehicle 1 determines whether the detection value of the encoder fed back in the above step S103 has not changed for a predetermined time or more (step S105).When this determination is NO (step S105; NO), the process proceeds to step S101.

[0046] When it is determined in step S105 that the detected value of the encoder has not changed for a predetermined time or longer (step S105; YES), the abnormality detection unit 12 of the transportation vehicle 1 detects that there is an abnormality in the feedback path (step S106). Then, this operation is terminated.

[0047] As described above, according to the guided vehicle 1 according to the embodiment, it is possible to detect an abnormality in the feedback path by using a target value for a motor and a detection value of an encoder that indicates the operating status of the motor.

[0048] For example, if a target value above a predetermined value is output to the motor, but the current detection value of the encoder remains unchanged from the previous detection value for a predetermined period of time or more, it is possible to detect an abnormality in the feedback path.

[0049] Here, the target value for the motor and the detected value of the encoder indicating the operating status of the motor can be obtained by the circuit configuration included in the conventional servo system as is. Therefore, according to the guided vehicle 1 according to the embodiment, it is possible to easily detect an abnormality in the feedback path by using the circuit configuration included in the conventional servo system as is.

[0050] Therefore, according to the transport vehicle 1 according to the embodiment, it is possible to detect abnormalities without complicating the circuit configuration and while keeping costs down.

[0051] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The elements of the embodiment, as well as their arrangement, shape, and size, are not limited to those shown in the examples, and can be changed as appropriate. Furthermore, the order of the above-described processing steps can be arbitrarily changed or executed in parallel as long as no inconsistency occurs in the processing content. [Explanation of symbols]

[0052] 1...transport vehicle, 2a, 2b...sensor, 3...PLC, 4...servo driver, 5a, 5b, 5c, 5d...servo motor, 11...protection area setting unit, 12...abnormality detection unit, 13...object detection unit, 14...stop control unit, B...virtual bumper, Ra, Rb...scanning range

Claims

1. a servo driver that supplies a drive voltage to a motor included in a vehicle body movement mechanism based on a target value for the motor; an encoder that detects an operating condition of the motor and feeds the detected operating condition back to the servo driver; an abnormality detection unit that detects, based on the target value and the detection value of the encoder, that there is an abnormality in a path that feeds back the detection value of the encoder from the encoder to the servo driver; A transport vehicle equipped with the above.

2. the abnormality detection unit detects that there is an abnormality in a path for feeding back the detection value of the encoder from the encoder to the servo driver when the target value is equal to or greater than a predetermined value and the detection value of the encoder does not change for a predetermined time. The transport vehicle according to claim 1.

3. the abnormality detection unit determines that the detection value of the encoder has not changed for a predetermined time when a state in which there is no difference between the current detection value of the encoder and the previous detection value of the encoder continues for a predetermined time or more. The transport vehicle according to claim 2.

4. the abnormality detection unit further includes, as a condition for detecting an abnormality in a path for feeding back a detection value of the encoder from the encoder to the servo driver, that a drive voltage is being supplied to the motor; The transport vehicle according to claim 2.

5. The motor and the encoder are provided in a plurality of pairs, The abnormality detection unit detects, for each of the groups, that there is an abnormality in a path for feeding back the detection value of the encoder from the encoder to the servo driver. The transport vehicle according to claim 1.

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