Fault detection device, mobile vehicle, and fault detection method

Abstract

This device detects steering system malfunctions in mobile vehicles equipped with active casters. [Solution] The fault detection unit 60 of the mobile robot 1 includes a motor rotation speed detection unit 60a that detects the motor rotation speed, which is the rotation speed of motors 23A and 23B that drive the steering shaft 35 of the active caster 110; a first turning speed calculation unit 60b that calculates a first turning speed, which is the turning speed of the active caster 110, from the motor rotation speed detected by the motor rotation speed detection unit 60a; a steering shaft angle detection unit 60c that detects the steering shaft angle of the steering shaft 35; a second turning speed calculation unit 60d that calculates a second turning speed, which is the turning speed of the active caster 110, from the steering shaft angle detected by the steering shaft angle detection unit 60c; a comparison unit 60e that calculates the difference between the first turning speed and the second turning speed; and a determination unit 60f that determines whether or not a fault has occurred in the steering system based on the difference calculated by the comparison unit 60e and a first threshold.

Description

[Technical Field]

[0001] The present invention relates to a fault detection device, a mobile vehicle, and a fault detection method for detecting a failure in the steering system of a mobile vehicle equipped with active casters. [Background technology]

[0002] Conventionally, among mobile vehicles such as mobile robots and mobile carts that can move on the floor surface by wheels, so-called holonomic omnidirectional mobile vehicles have no constraints on their movement, and therefore can immediately start moving and turning in all directions (360°) from any position and orientation of the vehicle. An example of such a holonomic omnidirectional mobile vehicle is the mobile vehicle equipped with a single-wheel type active caster described in Patent Documents 1 and 2. In an active caster, the axis of rotation when the wheel rolls (wheel axis) is positioned at a predetermined distance in the direction of wheel rolling from the axis of rotation when the wheel direction is changed (steering axis), and it is possible to independently control the wheel rolling (driving) and the change of wheel direction (steering) with two motors.

[0003] Furthermore, as described in Non-Patent Document 1, by mounting two or more active casters as described above, the propelled vehicle can be made into a holonomic omnidirectional vehicle capable of independently controlling a total of three degrees of freedom: movement on a plane (2 degrees of freedom) and posture (1 degree of freedom). This makes it possible to achieve a speed of any direction and magnitude for the entire vehicle.

[0004] The overall speed of the moving vehicle refers to the speed at the vehicle's geometric or physical center of gravity, or at any point relative to the center of gravity (this is called the origin of the vehicle coordinate system). While the overall speed of the moving vehicle may sometimes be described as the vehicle's speed or vehicle velocity, unless otherwise specified, these terms have the same meaning.

[0005] Here, vehicle speed [ν x ν y ω z ] Tand the driving angular velocity ω of the wheel axis with respect to the floor surface of the coordinate value (axial center position of the steering axis provided on the moving vehicle body) of the i-th active caster out of the total of N casters iw (driving speed) and the turning angular velocity ω is (turning speed) are represented by the following formula (1) as described in Non-Patent Document 1. When a command value of the vehicle speed is given, based on the following formula (1), command values of the driving speed and turning speed of the active caster are calculated, and based on these, the motor is driven.

[0006] [Number]

[0007] In the above formula (1), l i and θ [[ID=1"9]] i are the length and angle of the line segment connecting from the geometric center of gravity or physical center of gravity of the vehicle or a point based on the center of gravity to the position where the i-th active caster is installed. r is the wheel radius of the active caster, s is the caster trail of the active caster, and φ i is the steering axis angle of the i-th active caster.

[0008] As represented by the above formula (1), for the calculation of the driving speed and turning speed of the active caster to realize the operation of the moving vehicle equipped with the active caster, information on the steering axis angle φ i is required. Here, to obtain the steering axis angle, for example, in the structure where motors are connected to the wheel axis and the steering axis respectively and the active caster is operated by driving them as disclosed in Patent Document 3, the steering axis angle can be obtained by the encoder of the motor connected to the steering axis. On the other hand, in the case of the active caster of the differential drive steering mechanism as disclosed in Patent Documents 1 and 2, it is necessary to install an encoder on the steering axis. Furthermore, there is also an example where, as disclosed in Patent Document 4, the steering axis and the steering axis angle detection unit are not arranged coaxially, and an angle detection device such as an encoder is installed on another axis via a gear from the steering axis to detect the steering axis angle. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 7198445 [Patent Document 2] Patent No. 5228156 [Patent Document 3] Patent No. 3560403 [Patent Document 4] Japanese Patent Publication No. 2024-014606 [Non-patent literature]

[0010] [Non-Patent Document 1] Masayoshi Wada. Modeling and control of an omnidirectional mobile robot using active casters. Journal of the Robotics Society of Japan, 2007, 25.7: 1100-1107. [Overview of the project] [Problems that the invention aims to solve]

[0011] However, in the conventional technology described above, if the steering axis angle sensor, which is the basis for calculating the drive speed and turning speed of the active caster, malfunctions, calculations will be performed based on the faulty signal even if the measured value of the steering axis angle obtained is poor, which may lead to unexpected operation of the active caster and, consequently, unexpected operation of the moving vehicle.

[0012] Furthermore, if a malfunction occurs in the power transmission mechanism from the motor to the steering shaft, the moving vehicle will not perform the expected operation, but calculations will be performed based on the faulty signal, which may also lead to unexpected operation. This is especially true in structures that operate the active caster using a differential mechanism, as disclosed in Patent Documents 1 and 2, as it can affect not only the power transmission mechanism from the motor to the steering shaft but also the power transmission mechanism from the motor to the wheel axle, potentially causing the active caster to output unexpected drive speeds and turning speeds.

[0013] As described above, a malfunction in the steering system of an active caster, which consists of a power transmission mechanism from the motor to the steering shaft and a steering shaft angle sensor, could lead to unexpected operation of a mobile vehicle equipped with an active caster. Before such a situation occurs, the mobile vehicle needs to be able to quickly detect any malfunctions in the steering system and take measures to transition to a safe state. Therefore, the present invention aims to provide a fault detection device, a mobile vehicle, and a fault detection method suitable for detecting faults in the steering system of a mobile vehicle equipped with active casters. [Means for solving the problem]

[0014] To solve the above problems, a fault detection device according to one aspect of the present invention is a fault detection device for a mobile vehicle equipped with an active caster whose steering shaft and wheel shaft are driven by the power of a motor, comprising: a motor rotation speed detection unit that detects the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster; a first turning speed calculation unit that calculates a first turning speed, which is the turning speed of the active caster, from the motor rotation speed detected by the motor rotation speed detection unit; a steering shaft angle detection unit that detects the steering shaft angle of the steering shaft; a second turning speed calculation unit that calculates a second turning speed, which is the turning speed of the active caster, from the steering shaft angle detected by the steering shaft angle detection unit; a difference calculation unit that calculates the difference between the first turning speed and the second turning speed; and a determination unit that determines whether or not a fault in the steering system has occurred based on the difference calculated by the difference calculation unit and a preset threshold.

[0015] This allows for the detection of steering system failures in mobile vehicles equipped with active casters, based on the swivel speed of the active casters calculated from the motor rotation speed and steering axis angle, respectively. As a result, if a failure is detected, measures to transition the mobile vehicle to a safe state, such as stopping the vehicle, can be taken immediately.

[0016] Furthermore, in order to solve the above problems, a fault detection device according to one aspect of the present invention is a fault detection device for a mobile vehicle equipped with an active caster in which the steering shaft and wheel shaft are driven by the power of a motor, comprising: a motor rotation speed detection unit that detects the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster; a steering shaft angle estimation unit that calculates an estimated steering shaft angle, which is an estimated value of the steering shaft angle of the steering shaft, by integrating the motor rotation speed detected by the motor rotation speed detection unit over time; a steering shaft angle detection unit that detects the steering shaft angle of the steering shaft; a difference calculation unit that calculates the difference between the estimated steering shaft angle calculated by the steering shaft angle estimation unit and the steering shaft angle detected by the steering shaft angle detection unit; and a determination unit that determines whether or not a fault in the steering system has occurred based on the difference calculated by the difference calculation unit and a preset threshold.

[0017] This allows for the detection of steering system failures in mobile vehicles equipped with active casters, based on an estimated steering axis angle calculated from the turning speed derived from the motor rotation speed and the detected steering axis angle. As a result, if a failure is detected, measures to transition the mobile vehicle to a safe state, such as stopping the vehicle, can be taken immediately. Furthermore, in the fault detection device described above, the determination unit may determine that a steering system fault has occurred if the difference exceeds the threshold, and determine that no steering system fault has occurred if the difference does not exceed the threshold. In this case, fault detection becomes possible through simple processing such as comparison with a threshold, allowing for rapid detection of steering system failures.

[0018] Furthermore, in the above-described fault detection device, the determination unit may determine whether the difference exceeds the threshold, and if the determination that it exceeds the threshold is made consecutively more than a predetermined number of times, it may determine that a fault has occurred in the steering system, and if the determination that it exceeds the threshold is made consecutively more than a predetermined number of times, it may determine that a fault has not occurred in the steering system. In this case, even if there is no malfunction in the steering system, if a situation occurs where the difference momentarily exceeds a threshold due to external disturbances such as noise, it is possible to avoid or reduce the false detection of this as a malfunction. Furthermore, the fault detection device described above may also be configured to include a noise reduction unit that removes high-frequency noise components from the signals indicating the first and second turning speeds. In this case, signal noise can be removed, thus avoiding or reducing false detection of faults caused by signal noise. Furthermore, in the fault detection device described above, the mobile vehicle may be equipped with multiple active casters, and it may be determined whether or not a steering system fault has occurred for each active caster. In this case, it is possible to detect a malfunction in the steering system of a mobile vehicle equipped with multiple active casters.

[0019] Furthermore, in the fault detection device described above, the active caster may be equipped with a steering shaft angle sensor that detects the rotation angle of the steering shaft and is provided coaxially with the steering shaft, and the steering shaft angle detection unit may detect the steering shaft angle based on the measurement value of the rotation angle by the steering shaft angle sensor. In this case, failures in the steering system can be detected, such as when a malfunction occurs in the steering shaft angle sensor or in the motor that drives the steering shaft. Furthermore, in the fault detection device described above, the active caster may be provided with a rotation angle sensor that detects the rotation angle of the sensor mounting shaft, which is an axis parallel to the steering axis and on which the rotational power of the steering axis is transmitted via a power transmission mechanism, and the steering axis angle detection unit may detect the steering axis angle based on the rotation angle measurement value obtained by the rotation angle sensor. In this case, failures in the steering system can be detected when a failure occurs in the steering shaft angle sensor, in the power transmission system between the steering shaft and the sensor mounting shaft, or in the motor that drives the steering shaft. Furthermore, a mobile vehicle according to one aspect of the present invention comprises an active caster and the above-mentioned fault detection device. This provides the same functionality and effects as the fault detection device described above.

[0020] Furthermore, a fault detection method according to one aspect of the present invention is a fault detection method for a mobile vehicle equipped with an active caster whose steering shaft and wheel shaft are driven by the power of a motor, comprising: a motor rotation speed detection step for detecting the motor rotation speed, which is the rotation speed of a motor that drives the steering shaft of the active caster; a first turning speed calculation step for calculating a first turning speed, which is the turning speed of the active caster, from the motor rotation speed detected in the motor rotation speed detection step; a steering shaft angle detection step for detecting the steering shaft angle of the steering shaft; a second turning speed calculation step for calculating a second turning speed, which is the turning speed of the active caster, from the steering shaft angle detected in the steering shaft angle detection step; a difference calculation step for calculating the difference between the first turning speed and the second turning speed; and a fault determination step for determining whether or not a fault has occurred in the steering system based on the difference calculated in the difference calculation step and a preset threshold. This provides the same functionality and effects as the fault detection device and motor control device described above.

[0021] Furthermore, a fault detection method according to one aspect of the present invention is a fault detection method for a mobile vehicle equipped with an active caster in which the steering shaft and wheel shaft are driven by the power of a motor, comprising: a motor rotation speed detection step for detecting the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster; an estimated value calculation step for calculating an estimated steering shaft angle, which is an estimated value of the steering shaft angle of the steering shaft, by integrating the rotation speed detected in the motor rotation speed detection step over time; a steering shaft angle detection step for detecting the steering shaft angle of the steering shaft; a difference calculation step for calculating the difference between the estimated steering shaft angle calculated in the estimated value calculation step and the steering shaft angle detected in the steering shaft angle detection step; and a fault determination step for determining whether or not a fault has occurred in the steering system based on the difference calculated in the difference calculation step and a preset threshold. This provides the same functionality and effects as the fault detection device and motor control device described above. [Effects of the Invention]

[0022] According to one aspect of the present invention, it is possible to detect a malfunction in the steering system of a mobile vehicle equipped with active casters. [Brief explanation of the drawing]

[0023] [Figure 1] This figure shows the schematic configuration of the mobile robot 1 in this embodiment, where (a) is a front view and (b) is a side view. [Figure 2] This is a perspective view showing an example of the basic configuration of an active caster according to the first embodiment. [Figure 3] This is a plan view showing an example of the basic configuration of an active caster according to the first embodiment. [Figure 4] Figure 3 is a cross-sectional view of the area along the BB line. [Figure 5] (a) is a cross-sectional view of line AA in Figure 3, and (b) is a plan view showing an example of the configuration of a multi-pole magnet ring for angle detection. [Figure 6] This is a schematic diagram showing the drive force transmission path of an active caster according to the first embodiment. [Figure 7] This is a block diagram illustrating the schematic configuration of the control system for mobile robot 1. [Figure 8] This is a block diagram showing a specific configuration example of the mobile robot control device 51. [Figure 9] (a) and (b) are diagrams showing examples of motor arrangement configurations. [Figure 10] This diagram illustrates the concept of the steering system of the mobile robot 1 according to the first embodiment. [Figure 11] This is an explanatory diagram of a fault that can be detected by the fault detection unit 60 of the mobile robot 1 according to the first embodiment. [Figure 12] This is a flowchart showing the fault diagnosis process according to the first embodiment. [Figure 13] Figures (a) to (e) show examples of changes in various parameters related to the steering system of the active caster during the operation of the mobile robot 1, illustrating the case where the steering system is functioning normally. [Figure 14] Figures (a) to (e) show examples of changes in various parameters related to the steering system of the active caster during the operation of the mobile robot 1, and illustrate the case when a fault is detected by the fault detection unit 60. [Figure 15] (a) is a diagram showing a first mounting configuration example of the steering shaft angle sensor 32, and (b) is a diagram showing a second mounting configuration example of the steering shaft angle sensor 32. [Figure 16] Figures (a) to (e) show examples of changes in various parameters related to the steering system of the active caster during the operation of the mobile robot 1, and illustrate the case when a fault is detected by the fault detection unit 60. [Figure 17] (a) is a diagram showing an example of a first noise reduction configuration that removes noise components from the turning speed signal, and (b) is a diagram showing an example of a second noise reduction configuration that removes noise components from the turning speed signal. [Figure 18] This is a flowchart showing the fault diagnosis process according to the fourth embodiment. [Figure 19] This is a block diagram showing the schematic configuration of the mobile robot control device 51A according to the fifth embodiment. [Figure 20] This flowchart shows the fault diagnosis process according to the fifth embodiment. [Modes for carrying out the invention]

[0024] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the attached drawings. The embodiments described below are merely examples of means for realizing the present invention, and should be modified or changed as appropriate depending on the configuration of the apparatus to which the present invention is applied and various conditions. The present invention is not limited to the embodiments described below.

[0025] Furthermore, in the following drawings, identical or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the vertical and horizontal dimensions and scale of the members or parts may differ from the actual dimensions. Therefore, specific dimensions and scales should be determined by referring to the following explanation. Also, it goes without saying that there may be parts where the dimensional relationships and ratios differ between drawings. (First Embodiment) (composition) First, a first embodiment of the present invention will be described. Figures 1 to 14 show the first embodiment.

[0026] Figure 1 is a diagram showing the schematic configuration of the mobile robot 1 according to the first embodiment, where Figure 1(a) is a front view and Figure 1(b) is a side view.

[0027] As shown in Figures 1(a) and (b), the mobile robot 1 comprises an egg-shaped body 100, a control device 102 and a power supply 104 located inside the body 100, and active casters 110_1 and 110_2 and a caster 112 attached to the lower end of the body 100. Active casters 110_1 and 110_2 are composed of identical active casters. Active caster 110_1 comprises a wheel 15_1, a steering shaft 35_1, and motors 23A_1 and 23B1 that drive the wheel 15_1 and the steering shaft 35_1. Active caster 110_2 comprises a wheel 15_2, a steering shaft 35_2, and motors 23A_2 and 23B_2 that drive the wheel 15_2 and the steering shaft 35_2. In other words, active casters 110_1 and 110_2 are motor-driven drive wheels. The last digit of the code for each motor and steering shaft indicates the wheel, steering shaft, and motor mounted on the active caster 110_1 if it is 1, and the wheel, steering shaft, and motor mounted on the active caster 110_2 if it is 2. In other words, it corresponds to the last digit of the code for the active caster. The same applies to other components. Caster 112 is a driven wheel that does not have a drive source. Note that the driven wheel is not limited to a driven caster, but may also be an omni-wheel or Mecanum wheel, which are omnidirectional movement mechanisms. Hereinafter, active casters 110_1 and 110_2 may be referred to as "active caster 110" when not distinguishing between them. Similarly, wheels 15_1 and 15_2 may be referred to as "wheel 15" when not distinguishing between them. Steering shafts 35_1 and 35_2 may be referred to as "steering shaft 35" when not distinguishing between them. Motors 23A_1 and 23A_2, and motors 23B_1 and 23B_2 may be referred to as "motor 23A" and "motor 23B" when not distinguishing between them. Next, the detailed configurations of the active casters 110_1 and 110_2 will be described based on Figures 2 to 5. Since the active casters 110_1 and 110_2 are identical and have the same configuration, they will be described hereafter as active caster 110. Figure 2 is a perspective view showing an example of the basic configuration of an active caster according to the first embodiment, and Figure 3 is a plan view showing an example of the basic configuration of an active caster according to the first embodiment. Figure 4 is a partial cross-sectional view of Figure 3 along line BB, Figure 5(a) is a cross-sectional view of Figure 3 along line AA, and Figure 5(b) is a plan view showing an example of the configuration of a multi-pole magnet ring for angle detection. Note that Figure 4 is a partial cross-sectional view of the portion including the wheel 15 and axle 37. As shown in Figures 2 to 5, the active caster 110 has a main body 10 that is fixed to the body 100 of the mobile robot 1 as described above, and a drive mechanism 11, a swivel section 12, a transmission mechanism 13, a power conversion mechanism 14, and wheels 15 are provided on this main body 10.

[0028] The drive mechanism 11 is the input of rotational force and is mainly located above the main body 10. The swivel section 12 is located below the main body 10. The transmission mechanism 13 transmits the rotational force input by the drive mechanism 11. The power conversion mechanism 14 transmits the rotational force of the transmission mechanism 13 to the wheels 15. The wheels 15 are rotatable by the rotational force input via the drive mechanism 11, the transmission mechanism 13, and the power conversion mechanism 14, and are also steerable by the swivel section 12.

[0029] The drive mechanism 11 includes a first belt drive mechanism 22A and a second belt drive mechanism 22B. The first belt drive mechanism 22A includes a motor 23A, a first drive pulley 24A, a first input shaft 25A, a first driven pulley 26A, and a first drive belt 27A. The first drive pulley 24A is fixed to the drive shaft 23Aa of the motor 23A. The first input shaft 25A is rotatably supported about the axis O1. The first driven pulley 26A is fixed to a portion of the first input shaft 25A that protrudes above the body 10. In the first belt drive mechanism 22A, the first drive pulley 24A rotates when the motor 23A is driven, and this rotation is transmitted from the first drive pulley 24A to the first driven pulley 26A via the first drive belt 27A, causing the first input shaft 25A to rotate.

[0030] The second belt drive mechanism 22B includes a motor 23B, a second drive pulley 24B, a second input shaft 25B, a second driven pulley 26B, and a second drive belt 27B. The second drive pulley 24B is fixed to the drive shaft 23Ba of the motor 23B. The second input shaft 25B is rotatably supported about the axis O1. The second input shaft 25B is cylindrical in shape and passes through the first input shaft 25A, and is positioned outside the first input shaft 25A via a pair of intermediate bearings 44 so as to rotate independently of the first input shaft 25A. The second driven pulley 26B is fixed to a portion of the second input shaft 25B that protrudes above the body 10. The second driven pulley 26B is formed to the same diameter as the first driven pulley 26A and is located below the first driven pulley 26A. The second belt drive mechanism 22B drives the motor 23B, causing the second drive pulley 24B to rotate. This rotation is transmitted from the second drive pulley 24B to the second driven pulley 26B via the second drive belt 27B, causing the second input shaft 25B to rotate.

[0031] The steering shaft 35 is rotatably supported via a steering bearing 45 in a circular through-hole 10a formed in the main body 10, with the axis O1 at the center of its disc shape. This allows the steering shaft 35 to rotate relative to the main body 10 about the axis O1. The steering shaft 35 is rotatable relative to the main body 10 regardless of the rotation of the first input shaft 25A. Furthermore, the steering shaft 35 is rotatable relative to the main body 10 regardless of the rotation of the second input shaft 25B. With this configuration, the first input shaft 25A, the second input shaft 25B, and the steering shaft 35 are rotatably arranged coaxially along the axis O1.

[0032] The steering shaft 35 has a disc shape, and a first support member 36A and a second support member 36B are provided on both sides of the wheel 15 in the horizontal direction, extending downward from the lower part of the disc shape. The wheel 15 is integrally provided with an axle 37 that extends along an axis O2 perpendicular to the direction in which the axis O1 extends (vertical direction). One end of the axle 37 along the axis O2 is rotatably supported by the first support member 36A via a wheel bearing (not shown), and the other end along the axis O2 is rotatably supported by the second support member 36B via a wheel bearing (not shown). The steering shaft 35, the first support member 36A, and the second support member 36B constitute the swivel section 12. Furthermore, the rotation axis O5 of the wheel 15, which is aligned in the vertical direction intersecting the axis O2 of the axle 37, is positioned offset horizontally from the axis O1 of the steering shaft 35, perpendicular to the axis O2 of the axle 37.

[0033] The first input shaft 25A has a first drive spur gear 38A fixed below the disc-shaped steering shaft 35. The second input shaft 25B has a second drive spur gear 38B fixed above the disc-shaped steering shaft 35. The first drive spur gear 38A meshes with the first driven spur gear 39A, and the second drive spur gear 38B meshes with the second driven spur gear 39B. The first driven spur gear 39A is fixed to the first output shaft 40A. The first output shaft 40A is supported at its upper part by the steering shaft 35 via the first output bearing 46, and at its lower part by the first support member 36A via the first output bearing 46, and is rotatably supported about the axis O3. The second driven spur gear 39B is fixed to the second output shaft 40B. The second output shaft 40B passes through the steering shaft 35, its upper part is supported by the steering shaft 35 via a second output bearing 47, and its lower part is supported by the second support member 36B via a second output bearing 47, so that it can rotate freely about the axis O4.

[0034] The first driven spur gear 39A and the first output shaft 40A, centered on axis O3, and the second driven spur gear 39B and the second output shaft 40B, centered on axis O4, are arranged perpendicular to both sides of the axis O2 of the axle 37 relative to the wheel 15. Furthermore, the rotation axis O5 of the wheel 15, which is perpendicular to the axis O2 of the axle 37, is positioned horizontally offset from the axis O1 of the steering shaft 35, perpendicular to the direction of the axis O2 of the axle 37.

[0035] The transmission mechanism 13 has a first spur gear mechanism 13A and a second spur gear mechanism 13B. The first spur gear mechanism 13A consists of a first drive spur gear 38A, a first driven spur gear 39A, and a first output shaft 40A, and the second spur gear mechanism 13B consists of a second drive spur gear 38B, a second driven spur gear 39B, and a second output shaft 40B.

[0036] The first output shaft 40A has a first drive helical gear 41A fixed to its lower part, and the second output shaft 40B has a second drive helical gear 41B fixed to its lower part. On the other hand, the axle 37 has a first driven helical gear 42A fixed to one end in the direction of the axis O2, and a second driven helical gear 42B fixed to the other end in the direction of the axis O2. The first drive helical gear 41A meshes with the first driven helical gear 42A. The second drive helical gear 41B meshes with the second driven helical gear 42B. The power conversion mechanism 14 of the first embodiment has a first helical gear mechanism 14A and a second helical gear mechanism 14B. The first helical gear mechanism 14A is composed of a first drive helical gear 41A and a first driven helical gear 42A. The second helical gear mechanism 14B consists of a second driving helical gear 41B and a second driven helical gear 42B.

[0037] The active caster 110 can rotate and steer the wheel 15 by rotating the first input shaft 25A and the second input shaft 25B using the drive mechanism 11. For example, by rotating the first input shaft 25A and rotating the second input shaft 25B in the opposite direction to the first input shaft 25A, and making the rotational speeds of the first input shaft 25A and the second input shaft 25B the same, the wheel 15 can be rotated without steering. At this time, by making the rotational speeds of the first input shaft 25A and the second input shaft 25B different, the wheel 15 can be steered while rotating or stationary. Here, the operation of the active caster 110 will be explained based on Figure 6. Figure 6 is a schematic diagram showing the drive force transmission path of the active caster according to the first embodiment. As shown in Figure 6, in the active caster 110, when the first input shaft 25A is rotated in the first direction A1, which is clockwise when viewed from above, the first drive spur gear 38A rotates in the same direction, and the first driven spur gear 39A, which meshes with the first drive spur gear 38A, rotates in the second direction A2, which is opposite to the first direction A1. When the first driven spur gear 39A rotates in the second direction A2, the first drive helical gear 41A, which is integrally provided with the first driven spur gear 39A via the first output shaft 40A, rotates in the same direction. Then, the first driven helical gear 42A, which meshes with the first drive helical gear 41A, rotates in the third direction A3, which is clockwise when viewed from the side, causing the axle 37, which is integral with the first driven helical gear 42A, to rotate in the same direction. On the other hand, when the second input shaft 25B is rotated in the fourth direction B1, which is opposite to the first direction A1, the second drive spur gear 38B rotates in the same direction, and the second driven spur gear 39B, which meshes with the second drive spur gear 38B, rotates in the fifth direction B2, which is opposite to the fourth direction. When the second driven spur gear 39B rotates in the fifth direction B2, the second drive helical gear 41B, which is integrally provided with the second driven spur gear 39B via the second output shaft 40B, rotates in the same direction. Then, the second driven helical gear 42B, which meshes with the second drive helical gear 41B, rotates in the fifth direction B3, which is opposite to the third direction A3, causing the axle 37, which is integral with the second driven helical gear 42B, to rotate in the same direction. Here, since the third direction A3 and the fifth direction B3 are the same direction of rotation, if the first input shaft 25A and the second input shaft 25B rotate at the same speed, the wheel 15 rotates without turning. At this time, if the rotational speed of the second input shaft 25B is reduced relative to the rotational speed of the first input shaft 25A, the rotational speed input from the second drive helical gear 41B to the axle 37 via the second driven helical gear 42B becomes lower than the rotational speed input from the first drive helical gear 41A to the axle 37 via the first driven helical gear 42A. As a result, the pivot shaft 35 rotates by the difference in rotational speed, causing the wheels 15 to pivot and steer. Also, if the rotation of the second input shaft 25B is stopped, the rotational speed input from the second drive helical gear 41B to the axle 37 via the second driven helical gear 42B becomes 0, and the wheels 15 pivot and steer without rotating.

[0038] Furthermore, as shown in Figure 1(a), the active casters 110_1 and 110_2 are equipped with steering shaft angle sensors 32_1 and 32_2 that detect the rotation angles of the steering shafts 35_1 and 35_2. Here, the last digit of the code for each steering shaft and steering shaft angle sensor corresponds to the last digit of the code for the active caster. Hereafter, when there is no need to distinguish between them, the steering shaft angle sensors 32_1 and 32_2 may be referred to as steering shaft angle sensor 32. The steering shaft angle sensor 32 can be composed of a semiconductor sensor comprising, for example, a multi-pole magnet ring 32a for angle detection and a sensor IC 32c including a Hall element and a signal processing circuit, as shown in Figure 5(a). The multi-pole magnet ring 32a has a configuration in which S-pole and N-pole magnets are alternately arranged along the circumferential direction, as shown in Figure 5(b). The multi-pole magnet ring 32a is fixed to the lower surface of the radial outer edge of the steering shaft 35, as shown in Figure 5(a), and rotates together with the steering shaft 35. The sensor IC 32c is mounted on the lower surface of a substrate 32b fixed to the lower surface of the main body 10, and is positioned opposite the side surface of the multi-pole magnet ring 32a with a predetermined distance between them. In the example in Figure 5(a), one sensor IC 32c is arranged, but a configuration with multiple sensor ICs 32c may be arranged depending on the performance of the sensor IC 32c. The sensor IC 32c is connected to the control device 102 via wiring and communication lines on the substrate 32b. Specifically, the steering shaft angle sensor 32_1 is mounted coaxially with the steering shaft 35_1 of the active caster 110_1 and detects the steering shaft angle of the steering shaft 35_1. The steering shaft angle sensor 32_2 is mounted coaxially with the steering shaft 35_2 of the active caster 110_2 and detects the steering shaft angle of the steering shaft 35_2. Note that the steering shaft angle sensors 32_1 and 32_2 are not limited to semiconductor sensors using a magnetic ring and Hall element for angle detection, but may also be composed of other magnetic steering shaft angle sensors, optical steering shaft angle sensors, etc.

[0039] Furthermore, as shown in Figure 1(a), the active casters 110_1 and 110_2 are equipped with motor angle sensors 28A_1 and 28B_1 and 28A_2 and 28B_2 for detecting the rotation angles of the motors 23A_1 and 23B_1 and 23A_2 and 23B_2. Here, the numbers at the end of each motor and motor angle sensor correspond to the numbers at the end of the active caster. The motor angle sensors 28A_1 and 28B_1 and 28A_2 and 28B_2 are not shown in the figure, but can be composed of, for example, optical rotary encoders. Note that they are not limited to optical types and may be composed of other motor angle sensors such as magnetic rotary encoders. In addition, although not shown in the diagram, the mobile robot 1 is equipped with other sensors necessary for robot movement, such as a camera that takes pictures of its surroundings and an ultrasonic sensor to avoid collisions with obstacles. Next, the configuration of the control system of the mobile robot 1 will be explained based on Figure 7. Figure 7 is a block diagram showing the schematic configuration of the control system of the mobile robot 1. As shown in Figure 7, the mobile robot 1 is equipped with a control device 102. The control device 102 comprises a mobile robot control device 51 and motor control devices 52a, 52b, 52c, and 52d. The control device 102 provides integrated control of the mobile robot 1 and, although not shown in the diagram, includes a computer system such as a microcomputer.

[0040] Although not shown in the diagram, the computer system includes, for example, a CPU (Central Processing Unit) that controls calculations and the entire device based on a control program, a ROM (Read Only Memory) that stores the CPU's control program and the like in advance in a predetermined area, a RAM (Random Access Memory) for storing data read from the ROM and the calculation results necessary for the CPU's calculation process, an I / F (Interface) that mediates data input and output to external devices, and an A / D converter that converts analog signals from various sensors into digital signals. These components are connected to each other and enable data exchange via a bus, which is a signal line for transferring data.

[0041] The control device 102 executes a control program using its CPU, and based on various information obtained from the various sensors on the mobile robot 1, sets the velocity command value ν in the Cartesian coordinate system as the velocity command value for the mobile robot 1. xcmd ν ycmd and ω zcmd It generates the velocity command value ν. xcmd ν ycmd and ω zcmd This is input to the mobile robot control device 51.

[0042] The mobile robot control device 51 is composed of processing circuits such as a system LSI (Large Scale Integration) or a computer system. In the first embodiment, it is composed of a computer system as an example. Here, the computer system may be shared with the control device 102, or it may be configured to be provided separately. The mobile robot control device 51 acquires information from the motor angle sensor and the steering axis angle sensor, and outputs drive command values ​​to the motor control devices 52a to 52d to control the mobile robot 1 via the motors and active casters. The mobile robot control device 51 is connected to the motor control devices 52a to 52d via communication lines. Furthermore, it is connected to the steering axis angle sensors 321 and 322 of the active casters 1101 and 1102, respectively, via communication lines.

[0043] In other words, the mobile robot control device 51 receives the motor rotation speed ω of motors 23A_1 and 23B_1 from motor control devices 52a to 52d via a communication line. 1a and ω 1b This is input at a predetermined sampling period. In addition, the motor rotation speed ω of motors 23A_2 and 23B_2 2a and ω 2b The data is input at a predetermined sampling period. Furthermore, the steering axis angle φ1 from the steering axis angle sensor 32_1 of the active caster 110_1 and the steering axis angle φ2 from the steering axis angle sensor 32_2 of the active caster 110_2 are input at a predetermined sampling period. Note that the predetermined sampling periods may be the same or different.

[0044] The mobile robot control device 51 diagnoses a malfunction in the steering system of the active casters 110_1 and 110_2 based on the various input information. Furthermore, based on the speed command value input from the control device 102, the detected steering axis angle, and the results of the malfunction diagnosis, it sets the drive command value ω of the motors 23A_1 and 23B_1. 1cmd1 and ω 1cmd2 This generates the drive command values ​​ω for motors 23A_2 and 23B_2. 2cmd1 and ω 2cmd2 It generates the drive command value ω. 1cmd1 The motor control device 52a receives the drive command value ω 1cmd2 The motor control device 52b receives the drive command value ω 2cmd1 The motor control device 52c receives the drive command value ω 2cmd2 These are input to the motor control device 52d.

[0045] The motor control device 52a receives the motor angle θ input from the motor angle sensor 28A_1. 11Based on the motor rotation speed ω 1a Calculate the motor angle θ. 11 By differentiating with respect to time, we obtain the motor rotation speed ω 1a The motor rotation speed ω is calculated and 1a The motor angle θ input from the motor angle sensor 28B_1 is input to the mobile robot control device 51. Similarly, the motor control device 52b receives the motor angle θ input from the motor angle sensor 28B_1. 12 Differentiating this with respect to time gives the motor rotation speed ω 1b The motor rotation speed ω is calculated and 1b The motor angle θ input from the motor angle sensor 28A_2 is input to the mobile robot control device 51. The motor control device 52c receives the motor angle θ input from the motor angle sensor 28A_2. 21 Differentiating this with respect to time gives the motor rotation speed ω 2a The motor rotation speed ω is calculated and 2a The motor angle θ input from the motor angle sensor 28B_2 is input to the mobile robot control device 51. The motor control device 52d receives the motor angle θ input from the motor angle sensor 28B_2. 22 Differentiating this with respect to time gives the motor rotation speed ω 2b The motor rotation speed ω is calculated and 2b This is input to the mobile robot control device 51.

[0046] Furthermore, the motor control device 52a receives the drive command value ω from the mobile robot control device 51. 1cmd1 Based on the motor drive current Id 11 Similarly, the motor control device 52b generates the input drive command value ω 1cmd2 Based on the motor drive current Id 12 The motor control device 52c receives the drive command value ω from the mobile robot control device 51. 2cmd1 Based on this, the motor drive current Id 21 Similarly, the motor control device 52d generates the input drive command value ω 2cmd2 Based on the motor drive current Id 22 It generates the motor drive current Id. Then, the motor control device 52a uses the generated motor drive current Id. 11 The motor drive current Id is input to motor 23A_1, and the motor control device 52b outputs the generated motor drive current Id 12The motor 23B_1 is input to the motor. Furthermore, the motor control device 52c outputs the generated motor drive current Id 21 The motor drive current Id is input to motor 23A_2, and the motor control device 52d outputs the generated motor drive current Id 22 This is input to motor 23B_2.

[0047] As a result, the motors 23A_1 and 23B_1 of the active caster 110_1 receive the motor drive current Id 11 and Id 12 It rotates at a rotational speed corresponding to the motor drive current Id. In addition, the motors 23A_2 and 23B_2 of the active caster 110_2 are driven by the motor drive current Id 21 and Id 22 It is driven to rotate at a rotational speed corresponding to the rotational speed. Next, a specific configuration example of the mobile robot control device 51 will be described based on Figures 8 and 9. Figure 8 is a block diagram showing a specific configuration example of the mobile robot control device 51. Figures 9(a) and (b) show examples of motor arrangement configurations.

[0048] As shown in Figure 8, the mobile robot control device 51 includes a fault detection unit 60 and a control unit 62. The fault detection unit 60 includes a motor rotation speed detection unit 60a, a first turning speed calculation unit 60b, a steering axis angle detection unit 60c, a second turning speed calculation unit 60d, a comparison unit 60e, and a determination unit 60f. In the first embodiment, each of these components is a functional component realized by executing a program by the CPU.

[0049] The motor rotation speed detection unit 60a receives the latest motor rotation speed ω from the motor control devices 52a to 52d according to a predetermined control cycle. ia and ω ib The motor rotation speed ω is obtained. ia and ω ibThis is input to the first turning speed calculation unit 60b. Here, i represents the last digit of the code of the active caster 110 and corresponds to the active caster 110_i. In the first embodiment, the mobile robot 1 is equipped with two-wheeled active casters 110_1 and 110_2, so the number i is either 1 or 2.

[0050] The first turning speed calculation unit 60b calculates the input motor rotation speed ω ia and ω ib For example, according to equation (2-1) or (2-2) below, the first slewing speed ω is the slewing speed based on the motor rotation speed of the active caster 110_i. isc1 The first turning speed ω is calculated. isc1 This is input to the comparison unit 60e.

[0051]

number

[0052] Equation (2-1) above is the equation for the case where identical motors 23A and 23B are arranged in the same direction, as shown in Figure 9(a). That is, in the example shown in Figure 9(a), when the first input shaft 25A and the second input shaft 25B of the active caster 110 are rotated in the same direction, the motor rotation shafts are also rotated in the same direction. In this case, as shown in equation (2-1) above, the first turning speed ω isc1 is the motor rotation speed ω ia ni ω ib The result can be obtained by adding the values, multiplying the result by -1, and then dividing by 2. On the other hand, equation (2-2) above is the equation for the case where identical motors 23A and 23B are arranged in the orientation shown in Figure 9(b), with the orientation of motor 23B remaining the same, but the orientation of motor 23A rotated 180° (upside down) relative to the orientation in Figure 9(a). In this case, if they are rotated with the same drive signal as when their orientations are aligned, the shaft of motor 23A will rotate in the opposite direction to that in Figure 9(a), as shown in Figure 9(b). That is, in the example shown in Figure 9(b), when the first input shaft 25A and the second input shaft 25B of the active caster 110 are rotated in the same direction, a drive signal is input that rotates the motor rotation shaft of motor 23A in the opposite direction to that of motor 23B. As a result, the motor rotation speed ω ia The sign of is reversed compared to the case in Figure 9(a). In this case, as shown in equation (2-2) above, the first turning speed ω isc1 is the motor rotation speed ω ia From ω ib The result can be obtained by subtracting and then dividing by 2.

[0053] The steering axis angle detection unit 60c receives the steering axis angle φ from the steering axis angle sensors 32_1 and 32_2 according to a predetermined sampling period. i This is stored in memory such as RAM. Furthermore, according to a predetermined control cycle, the latest steering axis angle φ at that time is stored. i (t) and the steering axis angle φ obtained just before it. i (t-1) is read from memory. Then, the read steering axis angle φ is obtained. i (t) and φ i (t-1) is input to the second turning speed calculation unit 60d.

[0054] The second turning speed calculation unit 60d calculates the steering axis angle φ from the input. i (t) and φ i From (t-1) according to equation (3) below, the second turning speed ω is the turning speed based on the steering axis angle of the active caster 110_i. isc2 The second turning speed ω is then calculated. isc2 This is input to the comparison unit 60e.

[0055]

number

[0056] That is, as shown in the above formula (3), the second turning speed ω isc2 is obtained by dividing the result of subtracting φ i (t) from φ i (t - 1) by the control period Δt [s].

[0057] Here, the first turning speed ω isc1 and the second turning speed ω isc2 are obtained for each active caster 110. In the first embodiment, for the two - wheel active casters 110_1 and 110_2, the first turning speed ω 1sc1 and the second turning speed ω 1sc2 as well as the first turning speed ω 2sc1 and the second turning speed ω 2sc2 are calculated.

[0058] The comparison unit 60e stores and holds the input first turning speed ω isc1 and the second turning speed ω isc2 in a memory such as a RAM in association with time information. Then, the calculation times of the first turning speed ω isc1 and the second turning speed ω isc2 stored in the memory are compared, and data at the same time is selected. This is because, even when the acquisition periods of the measured values of the motor rotation speed and the steering axis angle are different, it is necessary to compare the data at the same time. Then, the difference d isc1 between the selected first turning speed ω isc2 and the second turning speed ω i is calculated. Then, the calculated difference d i is input to the determination unit 60f.

[0059] The determination unit 60f compares the input difference d i with a predetermined threshold value (hereinafter referred to as the "first threshold value") for comparing the turning speed difference set in advance. When the difference d i exceeds the first threshold value, it is determined that there is a failure in the steering system of the active caster 110_i. On the other hand, when the difference di If the value is below the first threshold, it is determined that there is no malfunction in the steering system of the active caster 110_i. The determination result (diagnosis result) is then input to the control unit 62. Here, the first threshold is set in advance through experiments, etc., and is set to a value that results in a turning speed difference that causes unintended movements such as malfunctions in the mobile robot 1.

[0060] The control unit 62 receives the speed command value ν from the control device 102. xcmd ν ycmd and ω zcmd And the steering axis angle φ detected by the steering axis angle detection unit 60c i Based on (t) and the diagnosis result of the steering system fault input from the determination unit 60f, the drive command values ​​for the rotational coordinate system of motors 23A_i and 23B_i are calculated.

[0061] Specifically, the speed command value ν of mobile robot 1 xcmd ν ycmd and ω zcmd ν is a physical quantity expressed in a Cartesian coordinate system. Therefore, the control unit 62 converts the command value expressed in a Cartesian coordinate system to a command value expressed in the motor's rotational coordinate system. For example, the control unit 62 calculates the command value for the rotational speed of each motor by multiplying the velocity command value expressed in a Cartesian coordinate system by the inverse (or pseudo-inverse) of the Jacobian matrix. In that case, the control unit 62 performs the calculation shown in equation (4) below. Note that in equation (4) below, ν cmd ω is the velocity command value of mobile robot 1, J is the Jacobian matrix (and J+ is the pseudo-inverse of the Jacobian matrix), ω cmd This represents the commanded rotation speed for each motor.

[0062]

number

[0063] If the determination unit 60f determines that there is no malfunction in the steering system, the input speed command value ν xcmd ν ycmd and ω zcmdThis is converted to a velocity command value in a rotating coordinate system according to equation (4) above, and the drive command value ω for each motor is set based on the converted velocity command value. icmd1 and ω icmd2 This generates the following: If motor 23A, the last digit will be 1; if motor 23B, the last digit will be 2. For example, drive command value ω 1cmd1 If so, this becomes the speed command value for motor 23A_1 of the active caster 110_1. The control unit 62 then sets the drive command values ​​ω for the generated motors 23A_1, 23B_1, 23A_2, and 23B_2. 1cmd1 , ω 1cmd2 , ω 2cmd1 and ω 2cmd2 This is input to the motor control devices 52a to 52d.

[0064] On the other hand, if the determination unit 60f determines that there is a malfunction in the steering system, it inputs a pre-set speed command value for when a malfunction occurs to the motor control devices 52a to 52d. This speed command value is a command value that transitions the mobile robot 1 to a safe state, and may be, for example, a command value that immediately stops the mobile robot 1, or a command value that gradually decelerates and finally stops it. In the case of flat ground, the power supply 104 of the mobile robot 1 may be turned off to forcibly stop it. Next, we will explain steering system failures based on Figures 10 and 11. Figure 10 is a diagram illustrating the concept of the steering system of the mobile robot 1 according to the first embodiment. Figure 11 is a diagram illustrating the faults that can be detected by the fault detection unit 60 of the mobile robot 1 according to the first embodiment.

[0065] In conventional technology, the steering system of an active caster consists of a power transmission mechanism from the motor to the steering shaft and a steering shaft angle sensor. Therefore, even if a failure occurs in the steering system, the failure cannot be detected, and calculations are performed based on the fault signal. In such a situation, there was a risk of unexpected movement of the mobile robot. In contrast, as in the failure detection unit 60 of the mobile robot 1 according to the first embodiment, the mobile robot control device 51 can recognize a failure in the steering system of the active caster 110, so that the mobile robot 1 can quickly detect a failure in the steering system and take measures such as transitioning to a safe state.

[0066] Here, we will explain the failures that can be detected by the present invention. In the mobile robot 1 according to the first embodiment, as shown in Figure 10, the command values ​​for the drive speed and turning speed of the active caster 110 are calculated, and the motor is driven based on these values, thereby allowing the mobile robot 1 to perform any operation. This is because when a motor rotation speed is applied, the active caster 110 generates a drive speed and a turning speed. The value obtained by integrating the turning speed over time can be considered to correspond to the steering axis angle.

[0067] In the example shown in Figure 11, motor power is transmitted from the motor of the active caster 110 to the steering shaft 35 via a power transmission mechanism. As a result, the steering shaft 35 outputs a turning speed. The rotation of the motor is detected by a motor angle sensor, and based on this, a measured value of the motor rotation speed can be obtained. On the other hand, the rotation of the steering shaft 35 is detected as a steering shaft measurement value by a steering shaft angle sensor 32. Although the true value of the turning speed of the steering shaft 35 cannot be known, if the steering system of the active caster 110 is operating without malfunction, the difference between the first turning speed calculated based on the motor rotation speed measurement value and the second turning speed calculated based on the steering shaft angle measurement value is expected to fall within the range of accuracy and uncertainty in the measurement and calculation process. (Troubleshooting process) Next, the fault diagnosis process performed by the CPU of the mobile robot control device 51 will be described. Figure 12 is a flowchart of the fault diagnosis process according to the first embodiment. The fault diagnosis process is, for example, a process that is repeated at a predetermined control cycle. The CPU of the mobile robot control device 51 starts a control program stored in a predetermined area of ​​the ROM and executes the fault diagnosis process shown in the flowchart of Figure 12 according to that program. When the fault diagnosis process is executed in the CPU, it first proceeds to step S100, as shown in Figure 12.

[0068] In step S100, the motor rotation speed detection unit 60a receives the current motor rotation speed ω from the motor control devices 52a to 52d. 1a , ω 1b , ω 2a and ω 2b The motor rotation speed is obtained and input to the first turning speed calculation unit 60b. Then, the process proceeds to step S102.

[0069] In step S102, the first turning speed calculation unit 60b calculates the input motor rotation speed ω 1a , ω 1b , ω 2a and ω 2b Based on the above equation (2), the first rotation speed ω of the active caster 110_1 is 1sc1 And the first turning speed ω of the active caster 110_2 2sc1 The first turning speed ω is calculated. 1sc1 and ω 2sc1 The result is input to the comparison unit 60e, and the process proceeds to step S104.

[0070] In step S104, the steering axis angle detection unit 60c retrieves the current steering axis angles φ1(t) and φ2(t), as well as the previous steering axis angles φ1(t-1) and φ2(t-1), from memory. Then, the retrieved steering axis angles φ1 and φ2, as well as φ1(t-1) and φ2(t-1), are input to the second turning speed calculation unit 60d. After that, the process proceeds to step S106.

[0071] In step S106, the second turning speed calculation unit 60d calculates the second turning speed ω of the active caster 110_1 based on the input steering axis angles φ1(t) and φ1(t-1) using equation (3) above. 1sc2 The second turning speed ω of the active caster 110_2 is calculated based on the input steering axis angles φ2(t) and φ2(t-1) and equation (3) above. 2sc2 The second turning speed ω is then calculated. 1sc2 and ω 2sc2 The result is input to the comparison unit 60e, and the process proceeds to step S108.

[0072] In step S108, the comparison unit 60e calculates the first turning speed ω at the same time from the first turning speed and second turning speed stored in memory. 1sc1 and ω 2sc1 And the second turning speed ω 1sc2 and ω 2sc2 Select and . Then select the first turning speed ω 1sc1 and ω 2sc1 And the second turning speed ω 1sc2 and ω 2sc2 Based on this, the difference between the two, d1(ω 1sc1 -ω 1sc2 ) and the difference d2(ω 1sc1 -ω 1sc2 The differences d1 and d2 are then calculated. After that, the calculated differences d1 and d2 are input to the determination unit 60f, and the process proceeds to step S110.

[0073] In step S110, the determination unit 60f compares the differences d1 and d2 with a first threshold. It then determines whether at least one of the differences d1 and d2 exceeds the first threshold. If it determines that it does (Yes), it proceeds to step S112; otherwise, it proceeds to step S114.

[0074] If the process proceeds to step S112, the determination unit 60f determines that a malfunction has occurred in the steering system of the mobile robot 1. In other words, it diagnoses that a malfunction has occurred in the steering system of the active caster. This diagnosis result is then input to the control unit 62, and the series of processes is terminated.

[0075] On the other hand, if the process proceeds to step S114, the determination unit 60f determines that there is no malfunction in the steering system of the mobile robot 1. In other words, it diagnoses that there is no malfunction in the steering system of the active caster. This diagnosis result is then input to the control unit 62, and the series of processes is terminated. Next, based on Figures 13 and 14, we will describe the normal operation of the mobile robot 1 and the operation when a steering system failure occurs.

[0076] Figures 13(a) to 13(e) show examples of changes in various parameters related to the steering system of the active caster during the operation of the mobile robot 1, and indicate the case where the steering system is operating normally. Figures 14(a) to 14(e) show examples of changes in various parameters related to the steering system of the active caster during the operation of the mobile robot 1, and indicate the case where a fault is detected by the fault detection unit 60. In Figures 13 and 14, the first wheel represents the active caster 110_1, and the second wheel represents the active caster 110_2.

[0077] When mobile robot 1 operates at the robot speed shown in Figure 13(a), its trajectory moves in the +X direction (forward direction relative to mobile robot 1; to the right relative to the plane of the paper) in the robot coordinate system, as shown in Figure 13(e). The steering axis angle at this time is an example of a half-turn along the way, and as shown in Figure 13(b), the turning speed temporarily increases and decreases as active casters 110_1 and 110_2 turn. Figure 13(c) shows the first turning speed (solid line in the figure) and the second turning speed (dashed line in the figure), and for both the first and second wheels, the two are almost perfectly aligned. In this case, as shown in Figure 13(d), it can be seen that the comparison result (difference value) of the turning speeds has hardly changed. Therefore, mobile robot 1 operates normally. That is, as shown in Figure 13(e), its trajectory is straight. Thus, under normal conditions, the comparison between the first and second turning speeds shows a slight vertical movement due to sharp turns, but it remains within the range of accuracy and uncertainty (i.e., below the first threshold) in the measurement and calculation process.

[0078] Next, in the example shown in Figure 14, as shown in Figure 14(a), the turning speed of the mobile robot 1 increases sharply at time t1 in Figure 14(b). At this time, the measured value of the steering axis angle for the second wheel, as shown in Figure 14(b), is approximately fixed at 0 at time t1 in the same figure. In other words, the steering axis angle sensor 32_2 in the steering system of the second wheel is malfunctioning. The dotted line in Figure 14(b) shows the measured value of the steering axis angle under normal conditions. In this malfunction, the steering axis angle sensor 32_2 continues to output a constant value (0 in the example of Figure 14(b)) as the measured value after time t1. Therefore, the second turning speed of the second wheel drops sharply to approximately 0 at time t1, as shown in Figure 14(c). As a result, the difference between the first turning speed and the second turning speed of the second wheel increases sharply and becomes a large value, as shown in Figure 14(d). This is because the first turning speed, calculated from the motor rotation speed determined from the normal motor rotation angle, and the second turning speed, calculated from the measurement value of the faulty steering axis angle sensor, were used to compare and determine the difference between the two. In this situation, as shown in Figure 14(e), from time t1 onward, control is performed based on the incorrect measurement, and the trajectory of the mobile robot 1 curves sharply in the -Y direction. In other words, it deviates significantly from the intended movement shown in Figure 13(e).

[0079] In such cases, the fault detection unit 60 of the present invention exhibits a large fluctuation (a difference) in the comparison result of the second wheel's turning speed immediately after a fault occurs. As a result, this difference exceeds the first threshold, and a fault is detected at time t2, indicated by the × mark in Figure 14(b). Therefore, measures such as transitioning the mobile robot to a safe state can be initiated from time t2. Consequently, safety can be ensured before the robot's speed or trajectory deviates significantly from the intended path. (Effects of the first embodiment)

[0080] As described above, the mobile robot 1 of the first embodiment includes identical active casters 110_1 and 110_2 whose steering shaft 35 and axle 37 are driven by motor power, and a mobile robot control device 51 which includes a fault detection unit 60 and a control unit 62. The fault detection unit 60 controls the motor rotation speed ω, which is the rotation speed of the motors 23A_1 and 23B_1 and 23A_2 and 23B_2 that drive the steering shaft 35 of the active casters 110_1 and 110_2. 1a , ω 1b , ω 2a and ω 2b A motor rotation speed detection unit 60a detects the motor rotation speed ω detected by the motor rotation speed detection unit 60a. 1a , ω 1b , ω 2a and ω 2b The first turning speed ω is the turning speed of the active casters 110_1 and 110_2. 1sc1 and ω 2sc1 A first turning speed calculation unit 60b calculates the first turning speed ω of the steering shaft 35, a steering shaft angle detection unit 60c detects the steering shaft angles φ1 and φ2 of the steering shaft 35, and a second turning speed ω of the active casters 110_1 and 110_2 is calculated from the steering shaft angles φ1 and φ2 detected by the steering shaft angle detection unit 60c. 1sc2 and ω 2sc2 A second turning speed calculation unit 60d calculates the first turning speed ω stored in memory. 1sc1 and ω 2sc1 and second turning speed ω 1sc2 and ω 2sc2 The system includes a comparison unit 60e that compares the calculation time with that of the first turning speed and calculates the differences d1 and d2 between the first turning speed and the second turning speed at the same time, and a determination unit 60f that determines whether or not a steering system malfunction has occurred based on the differences d1 and d2 calculated by the comparison unit 60e and a preset first threshold.

[0081] With this configuration, a malfunction in the steering system of the mobile robot 1 can be detected based on the first and second turning speeds of the active casters 110_1 and 110_2, which are calculated from the motor rotation speed and steering axis angle, respectively. As a result, if a malfunction is detected, the control unit 62 can immediately take measures to transition the mobile robot 1 to a safe state, such as stopping the mobile robot 1. Furthermore, in the mobile robot 1 of the first embodiment, the determination unit 60f of the fault detection unit 60 determines that a steering system failure has occurred if at least one of the differences d1 and d2 exceeds the second threshold, and determines that no steering system failure has occurred if it does not exceed the threshold. In this case, fault detection becomes possible through simple processing such as comparison with a threshold, allowing for rapid detection of steering system failures.

[0082] Furthermore, in the mobile robot 1 of the first embodiment, the steering axis angle sensor 32_1 is provided coaxially with the steering axis 35_1 of the active caster 110_1, and the steering axis angle sensor 32_2 is provided coaxially with the steering axis 35_2 of the active caster 110_2. The steering axis angle detection unit 60c then detects the steering axis angles φ1 and φ2 based on the measured values ​​of the steering axis angle sensors 32_1 and 32_2. With this configuration, failures in the steering system can be detected in cases such as when the steering shaft angle sensors 32_1 and 32_2 fail, or when the motors driving the steering shafts 35_1 and 35_2 fail. (Correspondence in the first embodiment) In the first embodiment, the mobile robot 1 corresponds to a mobile vehicle, the fault detection unit 60 corresponds to a fault detection device, and the motor rotation speed detection unit 60a and step S100 correspond to a motor rotation speed detection unit. Furthermore, in the first embodiment, the first turning speed calculation unit 60b and step S102 correspond to the first turning speed calculation unit, and the steering axis angle detection unit 60c and step S104 correspond to the steering axis angle detection unit.

[0083] Furthermore, in the first embodiment, the second turning speed calculation unit 60d and step S106 correspond to the second turning speed calculation unit, the comparison unit 60e and step S108 correspond to the difference calculation unit, and the determination unit 60f and steps S110 to S112 correspond to the determination unit. (Second Embodiment) (composition) Next, a second embodiment of the present invention will be described with reference to the drawings. Figures 15 and 16 show the second embodiment. The second embodiment differs from the first embodiment in that the steering shaft 35 and the steering shaft angle sensors 32_1 and 32_2 are not arranged coaxially. The following describes in detail the parts that differ from the first embodiment described above, and the explanations of overlapping parts will be omitted as appropriate. Hereafter, when there is no need to distinguish between steering axis angle sensors 32_1 and 32_2, they will simply be referred to as "steering axis angle sensor 32".

[0084] Figure 15(a) shows an example of the first mounting configuration of the steering axis angle sensor 32, and Figure 15(b) shows an example of the second mounting configuration of the steering axis angle sensor 32. Figures 16(a) to (e) show examples of changes in each parameter related to the steering system of the active caster during the operation of the mobile robot 1, and show the case when a fault is detected by the fault detection unit 60. In Figure 15, the first wheel is shown as active caster 110_1, and the second wheel is shown as active caster 110_2. (First mounting configuration example)

[0085] The first mounting configuration example of the steering shaft angle sensor 32 according to the second embodiment is shown in Figure 15(a) and includes a first spur gear 125 that rotates together with the steering shaft 35 around the axis O1, and a second spur gear 126 that meshes with the first spur gear 125 and rotates in a driven manner around the axis O6 which is parallel to the axis O1. Furthermore, a third spur gear 127 that meshes with the second spur gear 126 and rotates in a driven manner around the axis O7 which is parallel to the axis O6 is provided. Furthermore, the third spur gear 127 is fixed concentrically to the lower end of the sensor mounting shaft 130, and the steering shaft angle sensor 32 is mounted on the sensor mounting shaft 130. With this configuration, when the first spur gear 125 rotates together with the steering shaft 35, the second spur gear 126 rotates in a driven manner, and when the second spur gear 126 rotates in a driven manner, the third spur gear 127 rotates in a driven manner together with the sensor mounting shaft 130. Therefore, by detecting the rotational position of the sensor mounting shaft 130, the steering shaft angle of the steering shaft 35 can be detected. In other words, the rotational position of the pivot section 12 relative to the main body 10 can be detected. (Second mounting configuration example)

[0086] The second mounting configuration example of the steering shaft angle sensor 32 according to the second embodiment is shown in Figure 15(b), and includes a first pulley 128 that rotates together with the steering shaft 35 around the axis O1, and a second pulley 129 that is concentrically fixed to the lower end of the sensor mounting shaft 130. Furthermore, a belt 131 is provided that is wrapped around the first pulley 128 and the second pulley 129. With this configuration, when the first pulley 128 rotates together with the steering shaft 35, this rotational force is transmitted to the second pulley 129 via the belt 131, and the second pulley 129 rotates in a driven manner together with the sensor mounting shaft 130. Therefore, the steering shaft angle of the steering shaft 35 can be detected by detecting the rotational position of the sensor mounting shaft 130. In other words, the rotational position of the pivoting part 12 relative to the main body 10 can be detected.

[0087] In the first mounting configuration example shown in Figure 15(a) above, steering system failure may occur due to detachment, damage, or poor meshing of the spur gear interposed between the steering shaft 35 and the sensor. In the second mounting configuration example shown in Figure 15(b) above, steering system failure may occur due to detachment or damage to the power transmission mechanism, such as the belt or pulley. In other words, steering system failure can occur not only due to failure of the steering shaft angle sensor 32, but also due to damage or other failures within the power transmission mechanism from the motor to the steering shaft 35.

[0088] As shown above, if a failure occurs within the power transmission mechanism, the motor will rotate, but the measurement value by the steering shaft angle sensor 32 will not change after time t1, as shown in Figure 16(b). Even in such a case, the failure detection unit 60 of the present invention can detect the failure. That is, as shown in Figure 16(d), the comparison result of the turning speed shows a large fluctuation immediately after the failure occurs in the second wheel. Therefore, the comparison result of the first turning speed and the second turning speed exceeds the first threshold, and a failure is detected at time t2, indicated by the x marks in Figures 16(a) to (e). In the example shown in Figure 16(e), no safety measures are taken, and the mobile robot 1, which should be moving straight in the X direction, is making a large turn in the +Y direction. On the other hand, with the configuration of the present invention, after a failure is detected at time t2, measures can be taken to transition the mobile robot 1 to a safe state. That is, by starting the measures immediately from time t2, safety can be ensured quickly. (Effects of the second embodiment)

[0089] As described above, the mobile robot 1 of the second embodiment includes a steering shaft angle sensor 32_1 which is provided on a sensor mounting shaft 130 that is parallel to the steering shaft 35_1 and to which the rotational power of the steering shaft 35_1 is transmitted via a power transmission mechanism (composed of spur gears, belts, etc.) and detects the rotation angle of the sensor mounting shaft 130. In addition, it includes a steering shaft angle sensor 32_2 which is provided on a sensor mounting shaft 130 that is parallel to the steering shaft 35_2 and to which the rotational power of the steering shaft 35_2 is transmitted via a power transmission mechanism (composed of spur gears, belts, etc.) and detects the rotation angle of the sensor mounting shaft 130. The steering shaft angle detection unit 60c of the fault detection unit 60 detects the steering shaft angles φ1 and φ2 of the steering shafts 35_1 and 35_2 based on the measured values ​​of the steering shaft angle sensors 32_1 and 32_2.

[0090] With this configuration, failures in the steering system can be detected in cases such as when the steering shaft angle sensors 32_1 and 32_2 fail, when the power transmission system between the steering shafts 35_1 and 35_2 and the sensor mounting shaft 130 fails, or when the motor driving the steering shafts 35_1 and 35_2 fails. (Correspondence in the second embodiment) In the second embodiment, the steering axis angle sensors 32_1 and 32_2 correspond to the rotation axis angle sensors. (Third embodiment) (composition) Next, a third embodiment of the present invention will be described with reference to the drawings. Figure 17 shows the third embodiment. The third embodiment differs from the first and second embodiments in that it removes high-frequency noise components from the signals indicating the first and second turning speeds calculated by the first turning speed calculation unit 60b and the second turning speed calculation unit 60d. The following describes in detail the parts that differ from the first and second embodiments described above, and the explanations of overlapping parts will be omitted as appropriate. Figure 17(a) shows an example of a first noise reduction configuration that removes noise components from the turning speed signal, and Figure 17(b) shows an example of a second noise reduction configuration that removes noise components from the turning speed signal. (Example of first noise reduction configuration)

[0091] The fault detection unit 60 according to the first noise reduction configuration example has a configuration in which a smoothing filter 60g is added between the first turning speed calculation unit 60b and the comparison unit 60e, as shown in Figure 17(a), compared with the fault detection unit 60 according to the first embodiment. In addition, a smoothing filter 60h is added between the second turning speed calculation unit 60d and the comparison unit 60e.

[0092] That is, as shown in Figure 17(a), in order to remove signal noise, the first rotation speed ω is set in the smoothing filters 60g and 60h. isc1 and second turning speed ω isc2 For example, a smoothing process such as a low-pass filter is applied. For example, when smoothing is performed using a low-pass filter, a phase delay occurs with respect to the input signal before smoothing. Considering the effect of this phase delay, the cutoff frequency of the low-pass filter is the first rotation speed ω isc1 and second turning speed ω isc2 It is desirable that the values ​​be the same for both. The smoothing filters 60g and 60h are composed of, for example, digital filters. Digital filters can be composed of, for example, infinite impulse response (IIR) filters or finite impulse response (FIR) filters. (Example of second noise reduction configuration)

[0093] The fault detection unit 60 in the second noise reduction configuration example has a configuration in which a smoothing filter 60k is added after the comparison unit 60e, as shown in Figure 17(b), compared to the fault detection unit 60 in the first embodiment. That is, the first turning speed ω isc1 From the second turning speed ω isc2 The difference d obtained by subtracting i The signal indicating this is smoothed using, for example, a low-pass filter. In this case, processing can be done with a single smoothing filter, so the first turning speed ω isc1 and second turning speed ω isc2No phase lag difference occurs in relation to this. (Effects of the third embodiment)

[0094] As described above, in the third embodiment of the mobile robot 1, the fault detection unit 60 is located after the first turning speed calculation unit 60b and the second turning speed calculation unit 60d, and calculates the first turning speed ω isc1 and second turning speed ω isc2 It includes smoothing filters 60g and 60h to remove high-frequency noise components from the signal. Alternatively, the fault detection unit 60, after the comparison unit 60e, calculates the difference d. i It is equipped with a smoothing filter 60k that removes high-frequency noise components from the signal. With this configuration, the first turning speed ω isc1 and second turning speed ω isc2 A signal indicating the difference d i Since high-frequency noise components can be removed from the signal, false detection of faults due to high-frequency noise can be avoided or reduced. (Correspondence in the third embodiment) In the third embodiment, the smoothing filters 60g and 60h or 60k correspond to the noise reduction section. (Fourth Embodiment) (composition) Next, a fourth embodiment of the present invention will be described with reference to the drawings. Figure 18 shows the fourth embodiment. The fourth embodiment differs from the first to third embodiments in that it does not diagnose a steering system failure in a single failure determination, but rather diagnoses a failure when the number of failure determinations exceeds a predetermined number. The following will explain in detail the differences from the first to third embodiments described above, and any overlapping parts will be omitted as appropriate. (Troubleshooting process) Figure 18 is a flowchart showing the fault diagnosis process according to the fourth embodiment. The fault diagnosis process is, for example, a process that is repeated at a predetermined control cycle. The CPU of the mobile robot control device 51 starts a control program stored in a predetermined area of ​​the ROM and executes the fault diagnosis process shown in the flowchart of Figure 18 according to that program. When the fault diagnosis process is executed in the CPU, it first proceeds to step S200, as shown in Figure 18. Here, the processing from steps S200 to S210 is the same as the processing from steps S100 to S110 in the first embodiment described above, so we will omit the explanation. If the process proceeds to step S212, the determination unit 60f increments the value of the counter variable by 1 and proceeds to step S214.

[0095] If the process proceeds to step S214, the determination unit 60f determines whether the count value indicated by the count variable has exceeded a predetermined count threshold. If it is determined that it has exceeded the threshold (Yes), the process proceeds to step S216; otherwise, it proceeds to step S218.

[0096] If the process proceeds to step S216, the determination unit 60f determines that a malfunction has occurred in the steering system of the mobile robot 1. That is, it diagnoses that a malfunction has occurred in the steering system of the active caster. The determination unit then inputs this diagnosis result to the control unit 62 and assigns 0 to the counter variable, ending the series of processes.

[0097] On the other hand, if the process proceeds to step S218, the determination unit 60f determines that there is no malfunction in the steering system of the mobile robot 1. In other words, it diagnoses that there is no malfunction in the steering system of the active caster. This diagnosis result is then input to the control unit 62, and the series of processes is terminated. In this case, the value of the counter variable is retained as is. Furthermore, if it is determined in step S210 that the first threshold has not been exceeded and the process proceeds to step S220, the determination unit 60f counts down the value of the counter variable by 1 and proceeds to step S222. In step S222, the determination unit 60f determines whether the value of the counter variable has become negative. If it is determined to be negative (Yes), the process proceeds to step S224; otherwise, it proceeds to step S214. If the process proceeds to step S224, the determination unit 60f assigns 0 to the counter variable and proceeds to step S214. (Effects of the fourth embodiment)

[0098] As explained above, in the mobile robot 1 of the fourth embodiment, the determination unit 60f of the fault detection unit 60 determines the difference d i The system determines whether the value exceeds the first threshold. If it does, it increments the counter variable by 1. If the counter variable's count exceeds a predetermined number of times (counter threshold), it is determined that a steering system malfunction has occurred. On the other hand, if the value does not exceed the counter threshold, it is determined that no steering system malfunction has occurred. With this configuration, even if there is no malfunction in the steering system, if a situation occurs where the difference momentarily exceeds a threshold due to external disturbances such as noise, it is possible to avoid or reduce the false detection of this as a malfunction. (Correspondence in the fourth embodiment) In the fourth embodiment, the determination unit 60f corresponds to the determination unit. (Fifth embodiment) (composition) Next, a fifth embodiment of the present invention will be described with reference to the drawings. Figures 19 and 20 show the fifth embodiment. The fifth embodiment differs from the first to fourth embodiments in that it calculates an estimated steering shaft angle from the motor rotation speed detected by the motor rotation speed detection unit 60a, and diagnoses a fault based on the estimated steering shaft angle and the steering angle detected by the steering shaft angle detection unit 60c. The following will explain in detail the differences from the first to fourth embodiments described above, and any overlapping parts will be omitted as appropriate. Figure 19 is a block diagram showing the schematic configuration of the mobile robot control device 51A according to the fifth embodiment. The mobile robot 1 according to the fifth embodiment, as shown in Figure 19, is equipped with a mobile robot control device 51A instead of a mobile robot control device 51. The mobile robot control device 51A includes a fault detection unit 60A and a control unit 62. The fault detection unit 60A includes a motor rotation speed detection unit 60a, a first turning speed calculation unit 60b, a steering axis angle detection unit 60c, a steering axis angle estimation unit 60m, a comparison unit 60e, and a determination unit 60f.

[0099] The steering axis angle detection unit 60c receives the steering axis angle φ at a predetermined control cycle. i This is stored in memory such as RAM. Furthermore, according to a preset control cycle, the latest steering axis angle φ at that time is stored. i The steering axis angle φ is read from memory. i This is input to the comparison unit 60e.

[0100] The steering axis angle estimation unit 60m calculates the first turning speed ω calculated by the first turning speed calculation unit 60b. isc1 Integrating this over time gives the estimated steering axis angle φ, which is the estimated steering axis angle of the steering axis 35. isc1 The estimated steering axis angle φ is then calculated. isc1 This is input to the comparison unit 60e.

[0101] The comparison unit 60e receives the input steering axis angle estimate φ isc1 The steering axis angle φi is then stored in memory such as RAM, corresponding to the time. The estimated steering axis angle φ stored in memory is then stored. isc1 and steering axis angle φ i The timestamps are compared, and data from the same time are selected. Then, the estimated steering axis angle φ is selected. isc1 and steering axis angle φ i The difference d i Calculate the difference d. i This is input to the determination unit 60f.

[0102] The determination unit 60f receives the input difference d i The difference d is compared with a predetermined threshold value for comparing steering axis angle differences (hereinafter referred to as the "second threshold value"), and the difference di If the second threshold is exceeded, it is determined that there is a malfunction in the steering system of the active caster 110_i. Meanwhile, the difference d i If the value is below the second threshold, it is determined that there is no malfunction in the steering system of the active caster 110_i. The determination result (diagnosis result) is then input to the control unit 62. Here, the second threshold is set in advance through experiments, etc., and is set to a value that is the difference in steering axis angle at which a malfunction occurs in the mobile robot 1. (Troubleshooting process) Figure 20 is a flowchart showing the fault diagnosis process according to the fifth embodiment. The fault diagnosis process is, for example, a process that is repeated at a predetermined control cycle. The CPU of the mobile robot control device 51 starts a control program stored in a predetermined area of ​​the ROM and executes the fault diagnosis process shown in the flowchart of Figure 20 according to that program. When the fault diagnosis process is executed in the CPU, it first proceeds to step S300, as shown in Figure 20. In step S300, the motor rotation speed detection unit 60a retrieves the current motor rotation speed ω from memory. 1a , ω 1b , ω 2a and ω 2b The motor rotation speed is obtained and input to the first turning speed calculation unit 60b. Then, the process proceeds to step S302.

[0103] In step S302, the first turning speed calculation unit 60b calculates the input motor rotation speed ω 1a , ω 1b , ω 2a and ω 2b Based on the above equation (2), the first rotation speed ω of the active caster 110_1 is 1sc1 And the first turning speed ω of the active caster 110_2 2sc1 The first turning speed ω is calculated. 1sc1 and ω 2sc1 The value is input to the steering axis angle estimation unit 60m, and the process proceeds to step S304.

[0104] In step S304, the steering axis angle estimation unit 60m receives the input first turning speed ω 1sc1 and ω 2sc1 Integrating over time gives the estimated steering axis angle φ 1sa and φ 2sa The estimated steering axis angle φ is then calculated. 1sa and φ 2sa The result is input to the comparison unit 60e, and the process proceeds to step S306. In step S306, the steering axis angle detection unit 60c obtains the current steering axis angles φ1 and φ2 from memory. Then, the obtained steering axis angles φ1 and φ2 are input to the comparison unit 60e. After that, the process proceeds to step S308.

[0105] In step S308, the comparison unit 60e calculates the estimated steering axis angle φ at the same time from the estimated steering axis angle stored in memory and the steering axis angle. 1sa and φ 2sa Then, select steering axis angles φ1 and φ2. Then, the estimated value of the selected steering axis angle φ 1sa and φ 2sa Based on the steering axis angles φ1 and φ2, the difference between them d1(φ 1sa -φ1) and the difference d2(φ 1sa The difference d1 and d2 are then calculated. After that, the calculated difference d1 and d2 are input to the determination unit 60f, and the process proceeds to step S310.

[0106] In step S310, the determination unit 60f compares the differences d1 and d2 with a second threshold. It then determines whether at least one of the differences d1 and d2 exceeds the second threshold. If it determines that it does (Yes), it proceeds to step S312; otherwise, it proceeds to step S314.

[0107] If the process proceeds to step S312, the determination unit 60f determines that a malfunction has occurred in the steering system of the mobile robot 1. That is, it diagnoses that a malfunction has occurred in the steering system of the active caster. The determination result is then input to the control unit 62, and the series of processes is terminated.

[0108] On the other hand, if the process proceeds to step S314, the determination unit 60f determines that there is no malfunction in the steering system of the mobile robot 1. In other words, it diagnoses that there is no malfunction in the steering system of the active caster. This diagnosis result is then input to the control unit 62, and the series of processes is terminated. (Effects of the fifth embodiment)

[0109] As described above, the mobile robot 1 according to the fifth embodiment comprises identical active casters 110_1 and 110_2 whose steering shaft 35 and axle 37 are driven by motor power, and a mobile robot control device 51A which includes a fault detection unit 60A and a control unit 62. The fault detection unit 60A controls the motor rotation speed ω, which is the rotation speed of the motors 23A_1 and 23B_1 and 23A_2 and 23B_2 that drive the steering shaft 35 of the active casters 110_1 and 110_2. 1a , ω 1b , ω 2a and ω 2b A motor rotation speed detection unit 60a detects the motor rotation speed ω detected by the motor rotation speed detection unit 60a. 1a , ω 1b , ω 2a and ω 2b The first turning speed ω is the turning speed of the active casters 110_1 and 110_2. 1sc1 and ω 2sc1 A first turning speed calculation unit 60b calculates the first turning speed ω calculated by the first turning speed calculation unit 60b. 1sc1 and ω 2sc1 Integrating over time gives the estimated steering axis angle φ 1sa and φ 2sa A steering axis angle estimation unit 60m calculates the steering axis angle φ1 and φ2 of the steering axis 35, and a steering axis angle detection unit 60c detects the steering axis angle φ1 and φ2 of the steering axis 35. 1sa and φ 2sa Furthermore, the steering axis angles φ1 and φ2 detected by the steering axis angle detection unit 60c are stored in memory, and the estimated steering axis angle φ stored in memory is also stored in memory. 1sa and φ 2saThe system includes a comparison unit 60e that compares the time with the steering axis angles φ1 and φ2 and calculates the difference d1 and d2 between the estimated steering axis angle and the steering axis angle at the same time, and a determination unit 60f that determines whether or not a steering system malfunction has occurred based on the difference d1 and d2 calculated by the comparison unit 60e and a preset second threshold.

[0110] With this configuration, a malfunction in the steering system of the mobile robot 1 equipped with active casters 110_1 and 110_2 can be detected based on the estimated steering axis angle value estimated from the turning speed of the active casters 110_1 and 110_2 and the steering axis angle detected based on the measurement value of the steering axis angle sensor. As a result, if a malfunction is detected, measures to transition the mobile robot 1 to a safe state, such as stopping the mobile robot 1, can be taken immediately. (Correspondence to the fifth embodiment) In the fifth embodiment, the mobile robot 1 corresponds to a mobile vehicle, the motor rotation speed detection unit 60a and step S300 correspond to the motor rotation speed detection unit, and the first turning speed calculation unit 60b and step S302 correspond to the first turning speed calculation unit. Furthermore, in the fifth embodiment, the steering axis angle estimation unit 60m and step S304 correspond to the steering axis angle estimation unit, and the steering axis angle detection unit 60c and step S306 correspond to the steering axis angle detection unit. Furthermore, in the fifth embodiment, the comparison unit 60e and step S308 correspond to the difference calculation unit, and the determination unit 60f and steps S310 to S312 correspond to the determination unit. (modified version)

[0111] In the first to fifth embodiments described above, the mobile robot 1 was described using the example of a case where it has two active casters 110 (drive wheels). However, the configuration is not limited to this, and it may also have one or three or more active casters 110. Furthermore, the number of drive wheels and driven wheels is not limited to a combination of two drive wheels and one driven wheel. For example, it may have other configurations such as three drive wheels and zero driven wheels, two drive wheels and two driven wheels, or one drive wheel and two driven wheels.

[0112] Furthermore, in the first to fourth embodiments and their variations described above, a configuration in which the difference between the first turning speed and the second turning speed is compared with a certain first threshold was used as an example, but the system is not limited to this configuration. For example, in cases where a sharp turn is performed that exceeds a predetermined steering angle, such as a half-turn (180-degree turn) midway through, as illustrated in Figures 13 and 14, the value of the first threshold may be increased compared to the case where the steering angle is less than the predetermined angle, thus making the first threshold variable according to the turning situation. In other words, during a sharp turn, the difference between the first turning speed and the second turning speed is larger than in other cases, so the first threshold is increased. This can reduce or prevent false detection of a malfunction when the steering system is functioning normally.

[0113] Furthermore, in the first to fourth embodiments and their variations described above, the configuration for calculating the second turning speed is based on the above formula (3), but the configuration is not limited to this. For example, if the turning speed is calculated from the time difference of the steering axis angle measurement value, the detection accuracy in the low-speed range will decrease. Therefore, the turning speed may be calculated using other means, such as a timing method that calculates the speed by measuring the time over which the steering axis angle measurement value changes. For the timing method, please refer to "Yui Suto, Yasuhiro Kakinuma, Kohei Onishi, Fujishiro Aoyama, Development of Sensorless Chatter Vibration Detection Technology Using a Disturbance Observer in End Mill Machining (Part 1) - High-Precision Process Monitoring Using Average Timing Method -, Journal of the Japan Society for Precision Engineering, 2011, 77.7:707-712".

[0114] Furthermore, in the first to fifth embodiments and their variations described above, the motor control devices 52a to 52d were described as having a configuration in which the motor rotation speed is calculated from the motor rotation angle of each motor, but the system is not limited to this configuration. For example, if a rotary encoder outputs a motor rotation speed signal, the motor rotation speed may be acquired by other methods, such as acquiring the motor rotation speed based on that signal.

[0115] Furthermore, in the first to fifth embodiments and their variations described above, examples were given of safety measures such as immediately stopping the mobile robot 1, slowing it down and stopping, or turning off the power supply 104 when a steering system failure is detected, but the configuration is not limited to these. For example, if a steering system failure is detected while going downhill, the configuration may be such that the robot stops with the brakes applied without stopping the motor.

[0116] Furthermore, in the first to fifth embodiments and their variations described above, the active casters (drive wheels) are set to two wheels, and a safety measure is described in which the mobile robot 1 is immediately stopped in the event of a steering system failure. However, the configuration is not limited to this. For example, if there are three drive wheels, and a steering system failure occurs in one wheel, this wheel may be treated as a driven wheel (for example, by turning off the power supply from the power source 104), and the remaining two wheels may be controlled to move to a safe position and then stop as a safety measure. Basically, the mobile robot can be moved as long as two or more wheels are functioning normally, so the same safety measures can be taken if the remaining two wheels are functioning normally.

[0117] Furthermore, while the first to fifth embodiments and their variations described above have been explained using a configuration with two identical active casters as an example, the configuration is not limited to this, and some configurations may be made with different types of active casters, for example, by using different types of active casters for the two front wheels and the two rear wheels.

[0118] Furthermore, in the first to fifth embodiments and their variations described above, the functional blocks shown in Figures 8 and 19 are configured so that the functions of each component are realized by the CPU executing a program (software), but the configuration is not limited to this. The functions of one or more components of the functional block may be implemented using hardware such as electrical circuits or electronic circuits. Furthermore, although the first to fifth embodiments and their variations described above were explained using the active caster configuration shown in Figures 2 to 5 as an example, the invention is not limited to this configuration. For example, the first and second input shafts may be omitted, and the first and second output shafts, which engage with the axle via gears, may be directly motor-driven.

[0119] Furthermore, while the first to fifth embodiments and their variations described above illustrate the application of the present invention to a mobile robot equipped with active casters, the invention is not limited to this configuration and can be applied to other mobile vehicles, such as carts equipped with active casters. Moreover, the present invention can be applied not only to automatically driven mobile vehicles but also to manually driven mobile vehicles with power assist. [Explanation of Symbols]

[0120] 1...Mobile robot, 10...Main body, 10a...Penetration section, 11...Drive mechanism, 12...Swivel section, 13...Transmission mechanism, 13A...First spur gear mechanism, 13B...Second spur gear mechanism, 14...Power conversion mechanism, 14A...First helical gear mechanism, 14B...Second helical gear mechanism, 15...Wheels, 22A...First belt drive mechanism, 22B...Second belt drive mechanism, 23A, 23A_1, 23A_2, 23B, 23B_1, 23B_2...Motors, 23Aa, 23Ba...Drive shafts, 24A...First drive pulley , 24B...Second drive pulley, 25A...First input shaft, 25B...Second input shaft, 26A...First driven pulley, 26B...Second driven pulley, 27A...First drive belt, 27B...Second drive belt, 28A, 28A_1, 28A_2, 28B, 28B_1, 28B_2...Motor angle sensor, 32, 32_1, 32_2...Steering shaft angle sensor, 35, 35_1, 35_2...Steering shaft, 36A...First support member, 36B...Second support member, 37...Axle, 38A...First drive spur gear, 3 8B...Second drive spur gear, 39A...First driven spur gear, 39B...Second driven spur gear, 40A...First output shaft, 40B...Second output shaft, 41A...First drive helical gear, 41B...Second drive helical gear, 44...Intermediate bearing, 45...Steering bearing, 46...First output bearing, 47...Second output bearing, 51, 51A...Mobile robot control device, 52a~52d...Motor control device, 60, 60A...Fault detection unit, 60a...Motor rotation speed detection unit, 60b...First turning speed calculation unit, 60c...Steering shaft Angle detection unit, 60d... Second turning speed calculation unit, 60e... Comparison unit, 60f... Judgment unit, 60g, 60h, 60k... Smoothing filter, 60m... Steering axis angle estimation unit, 62... Control unit, 100... Body, 102... Control device, 104... Power supply, 110, 110_1, 110_2... Active caster, 112... Caster, 125... First spur gear, 126... Second spur gear, 127... Third spur gear, 128... First pulley, 129... Second pulley, 130... Sensor mounting shaft, 131... Belt

Claims

1. A fault detection device for a mobile vehicle equipped with active casters whose steering shaft and axle are driven by motor power, A motor rotation speed detection unit detects the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster. A first slewing speed calculation unit calculates a first slewing speed, which is the slewing speed of the active caster, from the motor rotation speed detected by the motor rotation speed detection unit, A steering shaft angle detection unit for detecting the steering shaft angle of the steering shaft, A second turning speed calculation unit calculates a second turning speed, which is the turning speed of the active caster, from the steering axis angle detected by the steering axis angle detection unit, A difference calculation unit that calculates the difference between the first turning speed and the second turning speed, A fault detection device comprising: a determination unit that determines whether or not a steering system fault has occurred based on the difference calculated by the difference calculation unit and a preset threshold.

2. A fault detection device for a mobile vehicle equipped with active casters whose steering shaft and axle are driven by motor power, A motor rotation speed detection unit detects the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster. A steering shaft angle estimation unit calculates a steering shaft angle estimate, which is an estimated value of the steering shaft angle of the steering shaft, by integrating the motor rotation speed detected by the motor rotation speed detection unit over time. A steering shaft angle detection unit for detecting the steering shaft angle of the steering shaft, A difference calculation unit calculates the difference between the steering axis angle estimate calculated by the steering axis angle estimation unit and the steering axis angle detected by the steering axis angle detection unit. A fault detection device comprising: a determination unit that determines whether or not a steering system fault has occurred based on the difference calculated by the difference calculation unit and a preset threshold.

3. The fault detection device according to claim 1 or 2, wherein the determination unit determines that a steering system failure has occurred if the difference exceeds the threshold, and determines that no steering system failure has occurred if the difference does not exceed the threshold.

4. The fault detection device according to claim 1 or 2, wherein the determination unit determines whether the difference exceeds the threshold, determines that a steering system failure has occurred if the determination that it exceeds the threshold is made for a predetermined number of consecutive times, and determines that no steering system failure has occurred if the determination that the number of times does not exceed the predetermined number of times is made.

5. The fault detection device according to claim 1, further comprising a noise reduction unit that removes high-frequency noise components from signals indicating the first turning speed and the second turning speed.

6. The aforementioned mobile vehicle is equipped with multiple active casters, The fault detection device according to claim 1 or 2, which determines whether or not a steering system failure has occurred for each of the active casters.

7. The active caster includes a steering shaft angle sensor that detects the rotation angle of the steering shaft, which is provided coaxially with the steering shaft. The fault detection device according to claim 1 or 2, wherein the steering shaft angle detection unit detects the steering shaft angle based on the measurement value of the rotation angle by the steering shaft angle sensor.

8. The active caster includes a rotation angle sensor that detects the rotation angle of the sensor mounting shaft, which is mounted on a sensor mounting shaft that is parallel to the steering shaft and on which the rotational power of the steering shaft is transmitted via a power transmission mechanism. The fault detection device according to claim 1 or 2, wherein the steering shaft angle detection unit detects the steering shaft angle based on the rotation angle measurement value obtained by the rotation angle sensor.

9. An active caster in which the steering shaft and axle are driven by the power of a motor, A mobile vehicle comprising the fault detection device according to claim 1 or 2.

10. A method for detecting a fault in a mobile vehicle equipped with an active caster in which the steering shaft and axle are driven by the power of a motor, A motor rotation speed detection step for detecting the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster, A first turning speed calculation step calculates a first turning speed, which is the turning speed of the active caster, from the motor rotation speed detected in the motor rotation speed detection step, A steering shaft angle detection step for detecting the steering shaft angle of the steering shaft, A second turning speed calculation step is performed to calculate a second turning speed, which is the turning speed of the active caster, from the steering axis angle detected in the steering axis angle detection step, A difference calculation step for calculating the difference between the first turning speed and the second turning speed, A method for detecting a malfunction in a moving vehicle, comprising: a malfunction determination step that determines whether or not a steering system malfunction has occurred based on the difference calculated in the difference calculation step and a preset threshold.

11. A method for detecting a fault in a mobile vehicle equipped with an active caster in which the steering shaft and axle are driven by the power of a motor, A motor rotation speed detection step for detecting the motor rotation speed, which is the rotation speed of the motor that drives the steering shaft of the active caster, The motor rotation speed detection step involves calculating an estimated steering shaft angle value, which is an estimated value of the steering shaft angle of the steering shaft, by integrating the rotation speed detected in the motor rotation speed detection step over time. A steering shaft angle detection step for detecting the steering shaft angle of the steering shaft, A difference calculation step which calculates the difference between the estimated steering axis angle calculated in the estimated value calculation step and the steering axis angle detected in the steering axis angle detection step, A method for detecting a malfunction in a moving vehicle, comprising: a malfunction determination step of determining whether or not a steering system malfunction has occurred based on the difference calculated in the difference calculation step and a preset threshold.

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