Vehicle control device, program, and vehicle control method

Abstract

To provide a vehicle control device, a program, and a vehicle control method capable of shortening a period from the start to the completion of discharge of the residual charge of a capacitor.SOLUTION: A control device 70 is applied to an unmanned conveyance vehicle 10 comprising: motors 20R, 20L, 40R, 40L each having a rotor for imparting rotational force to wheels 12L, 12R, 13L, 13R, respectively, and an armature winding; inverters 30R, 30L, 50R, 50L electrically connected respectively to the armature windings; a capacitor connected in parallel with a series connection body of upper and lower arm switches of the inverters; and a brake device 15 for imparting braking torque to hinder rotation of the wheels 12L, 12R, 13L, 13R. The control device 70 performs discharge control that is a switching control for supplying a d-axis current and a q-axis current to the armature windings in order to discharge the capacitor in a state where the brake device 15 is instructed to impart braking torque.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a vehicle control device, a program, and a vehicle control method. [Background technology]

[0002] A vehicle equipped with a motor, an inverter, and a control device is known. The motor includes a rotor that applies rotational force to the vehicle wheels and an armature winding. The inverter includes a series connection of upper and lower arm switches electrically connected to the armature winding.

[0003] A capacitor is connected in parallel to the series-connected upper and lower arm switches for the purpose of smoothing the input voltage of the inverter, etc. In order to discharge the residual charge in the capacitor, the control device controls the switching of the upper and lower arm switches.

[0004] Patent Document 1 describes switching control in which a d-axis current flows through the armature winding in order to reduce the torque generated by the motor to zero while the residual charge is being discharged. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3289567 Summary of the Invention [Problem to be solved by the invention]

[0006] A technique for shortening the time period from the start to the completion of discharge of residual charge in a capacitor is desired.

[0007] A primary object of the present disclosure is to provide a vehicle control device, a program, and a vehicle control method that can shorten the period from the start to the completion of discharge of residual charge in a capacitor. [Means for solving the problem]

[0008] The present disclosure provides an inverter having a series connection of upper and lower arm switches, the upper and lower arm switches being electrically connected to the armature winding; a capacitor connected in parallel to the series-connected body of the upper and lower arm switches; a brake device that applies a braking torque to at least one of the wheel, the rotor, and a power transmission path from the rotor to the wheel, the braking torque preventing the wheel from rotating; In the vehicle control device applied to the vehicle, an instruction unit that instructs the brake device to apply a braking torque; a discharge control unit that performs discharge control, which is switching control of the upper and lower arm switches to cause a d-axis current and a q-axis current to flow through the armature winding in order to discharge the capacitor, when the instruction unit instructs application of a braking torque; Equipped with.

[0009] In this disclosure, in order to discharge the capacitor, switching control is performed on the upper and lower arm switches that pass a q-axis current in addition to a d-axis current. This allows the residual charge in the capacitor to be discharged more quickly than when only the d-axis current is passed through the d- and q-axis currents. In this case, even if the motor torque is generated by the flow of the q-axis current, it is possible to prevent the wheels from rotating due to the braking torque of the brake device.

[0010] In this way, according to the present disclosure, it is possible to reduce the period from the start to the completion of discharge of the residual charge in the capacitor while suppressing the occurrence of an incident in which the wheels rotate. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing the overall configuration of an automated guided vehicle according to a first embodiment. [Figure 2] Side view of an automated guided vehicle. [Figure 3] Overall configuration diagram of an in-vehicle control system. [Figure 4]4 is a time chart showing an output signal of a Hall element. [Figure 5] FIG. 4 is a block diagram of a discharge control process executed by a control device. [Figure 6] 4 is a flowchart of a discharge control process. [Figure 7] 10 is a flowchart of a discharge control process according to a second embodiment. [Figure 8] FIG. 11 is a diagram showing the direction of torque generated on an upwardly inclined road surface according to the third embodiment. [Figure 9] FIG. 10 is a diagram showing the direction of torque generated on a downward slope road surface. [Figure 10] 4 is a flowchart of a discharge control process. [Figure 11] 10 is a flowchart of a discharge control process according to a fourth embodiment. [Figure 12] FIG. 13 is a diagram showing the direction of torque generated at each drive wheel according to the fifth embodiment. [Figure 13] FIG. 4 is a diagram showing the direction of torque generated at each drive wheel. [Figure 14] FIG. 4 is a diagram showing the direction of torque generated at each drive wheel. [Figure 15] FIG. 4 is a diagram showing the direction of torque generated at each drive wheel. [Figure 16] 4 is a flowchart of a discharge control process. [Figure 17] FIG. 13 is a diagram showing the direction of torque generated at each drive wheel according to a modification of the fifth embodiment. [Figure 18] FIG. 13 is a diagram showing the direction of torque generated at each drive wheel according to a modification of the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Several embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding and / or associated parts may be assigned the same reference numerals or reference numerals that differ in the hundredth or more digit. For corresponding and / or associated parts, reference may be made to the descriptions of other embodiments.

[0013] First Embodiment A first embodiment of a control device according to the present disclosure will be described below with reference to the drawings. The control device of this embodiment is applied to a small mobility vehicle. The small mobility vehicle of this embodiment is a vehicle that travels at a low speed (specifically, a maximum traveling speed) of, for example, 10 km / h or less, and specifically is an automated guided vehicle (AGV) that is an electric vehicle used in factories.

[0014] As shown in FIGS. 1 and 2, the automated guided vehicle 10 includes a vehicle body 11 and a plurality of wheels. The automated guided vehicle 10 includes a right front wheel 12R (corresponding to the "first right wheel"), a left front wheel 12L (corresponding to the "first left wheel"), a right rear wheel 13R (corresponding to the "second right wheel"), and a left rear wheel 13L (corresponding to the "second left wheel"). The right front wheel 12R and the left front wheel 12L are aligned in the vehicle width direction of the automated guided vehicle 10. The right rear wheel 13R and the left rear wheel 13L are aligned in the vehicle width direction. The right rear wheel 13R and the left rear wheel 13L are aligned in the vehicle length direction of the automated guided vehicle 10 relative to the right front wheel 12R and the left front wheel 12L.

[0015] The upper part of the vehicle body 11 is a loading section 11a on which an object to be transported is placed. The wheels 12R, 12L, 13R, and 13L are provided below the loading section 11a.

[0016] The automated guided vehicle 10 is equipped with a DC power supply 14 that serves as a power supply source for propelling the automated guided vehicle 10. The DC power supply 14 is, for example, a storage battery or a fuel cell. The storage battery is, for example, a secondary battery such as a lithium-ion storage battery, a nickel-metal hydride storage battery, or a lead storage battery.

[0017] The automated guided vehicle 10 is equipped with motors and inverters for causing each of the wheels 12R, 12L, 13R, and 13L to function as a drive wheel. Specifically, the automated guided vehicle 10 is equipped with the following motors: a right front motor 20R (corresponding to a "first right motor") that rotates the right front wheel 12R; a left front motor 20L (corresponding to a "first left motor") that rotates the left front wheel 12L; a right rear motor 40R (corresponding to a "second right motor") that rotates the right rear wheel 13R; and a left rear motor 40L (corresponding to a "second left motor") that rotates the left rear wheel 13L. In this embodiment, for convenience, it is assumed that the torque generated by each of the motors 20R, 20L, 40R, and 40L is transmitted to each of the wheels 12R, 12L, 13R, and 13L without passing through a transmission. The motors 20R, 20L, 40R, and 40L may be on-board motors provided on the vehicle body 11, or may be in-wheel motors.

[0018] The automated guided vehicle 10 is equipped with inverters including a right front inverter 30R (corresponding to the "right first inverter"), a left front inverter 30L, a right rear inverter 50R (corresponding to the "right second inverter"), and a left rear inverter 50L (corresponding to the "left second inverter"). Each of the inverters 30R, 30L, 50R, and 5L is electrically connected to the armature windings of each of the motors 20R, 20L, 40R, and 40L.

[0019] The automated guided vehicle 10 is equipped with a mechanical brake device 15. The brake device 15 is provided corresponding to each of the wheels 12R, 12L, 13R, and 13L, and generates a braking torque by applying a frictional force to the wheel. The brake device 15 in this embodiment is a non-excitation brake device that applies a braking torque to the wheel in a non-energized state and releases the application of the braking torque to the wheel in a powered state. Note that if the motors 20R, 20L, 40R, and 40L are in-wheel motors, the brake device 15 may be built into each of the motors 20R, 20L, 40R, and 40L, for example.

[0020] Next, the electrical configuration of the automatic guided vehicle 10 will be described with reference to FIG.

[0021] The right front inverter 30R is a power conversion circuit that converts DC power supplied from the DC power supply 14 into three-phase AC power and supplies it to the armature winding of the right front motor 20R.

[0022] The right front inverter 30R includes three phases of series-connected upper arm switches SH and lower arm switches SL. In this embodiment, each switch SH, SL is a voltage-controlled semiconductor switching element, more specifically, an N-channel MOSFET. The high-potential side terminal of each switch SH, SL is the drain, and the low-potential side terminal is the source. Each switch SH, SL includes a body diode DH, DL. Note that each switch SH, SL may be, for example, an IGBT. In this case, the high-potential side terminal of each switch SH, SL is the collector, the low-potential side terminal is the emitter, and a freewheel diode is connected in anti-parallel to each switch SH, SL.

[0023] The right front motor 20R includes a rotor 24 and a stator 21. The rotor 24 is capable of transmitting power to the right front wheel 12R. In this embodiment, the right front motor 20R is a permanent magnet field type synchronous machine. The rotor 24 includes a rotor core 25 and permanent magnets 26 (e.g., neodymium magnets) that are field poles provided on the rotor core 25.

[0024] The stator 21 includes a stator core 22 and armature windings 23 for three phases (U, V, and W phases) wound around the stator core 22. The armature windings 23 for each phase are arranged on the stator core 22 with an electrical angle of 120° between them. In each phase, a first end of the armature winding 23 is connected to the source of the upper arm switch SH and the drain of the lower arm switch SL. In addition, in each phase, a second end of the armature winding 23 is connected to the neutral point.

[0025] The right front inverter 30R includes a capacitor 31. The capacitor 31 functions as a smoothing capacitor. The capacitor 31 is connected in parallel to the series connection of the upper and lower arm switches SH and SL of each phase.

[0026] In this embodiment, the left front inverter 30L, the right rear inverter 50R, and the left rear inverter 50L are configured similarly to the right front inverter 30R. Therefore, detailed descriptions of the inverters 30L, 50R, and 50L will be omitted. Furthermore, the left front motor 20L, the right rear motor 40R, and the left rear motor 40L are configured similarly to the right front motor 20R. Therefore, detailed descriptions of the motors 20L, 40R, and 40L will be omitted.

[0027] The automated guided vehicle 10 is equipped with a high-potential side path 16H, a low-potential side path 16L, a high-potential side power switch 17H, and a low-potential side power switch 17L as components for electrically connecting each inverter 30R, 30L, 50R, and 50L to the DC power supply 14.

[0028] A high potential side path 16H is connected to the high potential side terminal of each upper arm switch SH of each inverter 30R, 30L, 50R, 50L. The high potential side path 16H is connected to the positive terminal of the DC power supply 14 by a high potential side power switch 17H. A low potential side path 16L is connected to the low potential side terminal of each lower arm switch SL of each inverter 30R, 30L, 50R, 50L. The low potential side path 16L is connected to the negative terminal of the DC power supply 14 by a low potential side power switch 17L.

[0029] In this embodiment, the power switches 17H, 17L are normally-off switches. When the power switches 17H, 17L are turned on by energizing the power switches 17H, 17L, the DC power supply 14 is electrically connected to the inverters 30R, 30L, 50R, 50L and the brake devices 15. On the other hand, when the power switches 17H, 17L are turned off by deenergizing the power switches 17H, 17L, the DC power supply 14 is electrically disconnected from the inverters 30R, 30L, 50R, 50L and the brake devices 15.

[0030] The high potential side terminal of each braking device 15 is connected to the high potential side path 16H via the changeover switch 18. The low potential side terminal of each braking device 15 is connected to the low potential side path 16L. The changeover switch 18 in this embodiment is a normally-off switch. When the changeover switch 18 is turned on by energizing the changeover switch 18 while the power switches 17H, 17L are on, power is supplied from the DC power supply 14 to the braking device 15. This stops the application of braking torque to the wheels from the braking device 15. On the other hand, when the changeover switch 18 is turned off by stopping the energizing operation of the changeover switch 18, power supply to the braking device 15 is stopped. This causes the braking torque to be applied to the wheels from the braking device 15.

[0031] The changeover switch 18 may be a switch provided individually for each brake device 15, or may be a switch common to all brake devices 15.

[0032] The automated guided vehicle 10 has a configuration for controlling the travel of the automated guided vehicle 10 by controlling the inverters 30R, 30L, 50R, 50L and the brake devices 15. In more detail, the automated guided vehicle 10 has a voltage sensor 60, a current sensor 61, a rotation angle sensor 62, an inertia sensor 63, and a control device 70.

[0033] The voltage sensor 60 detects the voltage across the capacitor 31 in each of the inverters 30R, 30L, 50R, and 50L. The current sensor 61 detects the phase current flowing through the armature winding 23 of each phase in each of the motors 20R, 20L, 40R, and 40L. The rotation angle sensor 62 detects the electrical angle of the rotor 24 in each of the motors 20R, 20L, 40R, and 40L.

[0034] Although the sensors 60, 61, and 62 are provided individually corresponding to the motors 20R, 20L, 40R, and 40L, they are not shown individually in FIG. 3 for the sake of convenience.

[0035] The inertial sensor 63 detects three-dimensional inertial motion of the automatic guided vehicle 10. Specifically, the inertial sensor 63 includes an acceleration sensor that detects translational motion on three orthogonal axes, and a gyro sensor that detects rotational motion around the three orthogonal axes.

[0036] The detection values ​​of the sensors 60 to 63 are input to the control device 70. The control device 70 is an electronic control unit (ECU) that performs various driving controls for the automated guided vehicle 10, and includes a processor 71 and a storage unit 72 as hardware. In the control device 70, the processor 71 and the storage unit 72 are connected to each other via a communication bus 73. In the automated guided vehicle 10, each on-board device can be controlled by an ECU corresponding to that device. However, for convenience, multiple ECUs are shown as one control device 70 in FIG. 3.

[0037] The memory unit 72 includes a memory and a storage as hardware. The memory is a storage device for storing data used in the processing of the control device 70. The memory provides the processor 71 with a working area for temporary use when the processor 71 performs processing, for example. The memory includes, for example, a ROM or a RAM. The storage is a storage device for storing various programs and data to be read and executed by the processor 71, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or a flash memory. The storage stores program information and the like for the processing shown in Figures 5 and 6, which will be described later.

[0038] For example, program information stored in a non-transient physical recording medium is installed in the storage unit 72. The recording medium is, for example, a USB memory, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as over the air (OTA), is installed in the storage unit 72.

[0039] Next, the rotation angle sensor 62 of this embodiment will be described in detail. The rotation angle sensor 62 of this embodiment is a digital sensor, a Hall sensor with a detection resolution of 60°. As shown in FIG. 4, the Hall sensor includes a Hall element and a comparator that output three signals Ha, Hb, and Hc whose logic is inverted every 180° of electrical angle. The signals Ha, Hb, and Hc are shifted in phase by 120° in electrical angle. In this embodiment, the resolution of the electrical angle detected by the rotation angle sensor 62 is 360° / (P×6), where P is the number of pole pairs of the rotor 24. Because the resolution is 60°, the number of pole pairs P of the rotor 24 in this embodiment is 1.

[0040] The control device 70 controls the discharge of the capacitors 31 of the inverters 30R, 30L, 50R, and 50L before an operator replaces the DC power supply 14 of the automatic guided vehicle 10. Fig. 5 shows a block diagram of the discharge control.

[0041] The control device 70 includes a discharge control unit 80 and an instruction unit 90. The discharge control unit 80 performs switching control of each of the inverters 30R, 30L, 50R, and 50L to cause d-axis and q-axis currents to flow through the armature windings 23 in order to discharge the residual charge of the capacitor 31 in the automated guided vehicle 10 whose operation has been stopped. The instruction unit 90 instructs energization or de-energization of the changeover switch 18.

[0042] First, the discharge control unit 80 will be described.

[0043] The command torque calculation unit 81 calculates a command torque Tcmd generated by each of the motors 20R, 20L, 40R, and 40L in discharge control based on the maximum allowable braking torque Tmax that can be applied to the wheels by the brake device 15. Specifically, the command torque calculation unit 81 calculates the command torque Tcmd (= Tmax × G) by multiplying the maximum allowable braking torque Tmax by a gain G (0 < G < 1). The gain G is set, for example, to "0.5 < G < 1".

[0044] In the present embodiment, for example, in order to reduce the cost of the automated guided vehicle 10, a sensor with low resolution is used as the rotation angle sensor 62. Even in this case, by setting the command torque Tcmd in consideration of the maximum allowable braking torque Tmax, the stopped state of the automated guided vehicle 10 is maintained during discharge control.

[0045] Note that, for example, when it is desired to shorten the period until discharge is completed, the gain G is increased. On the other hand, when it is desired to reduce the force acting on the power transmission path and the like due to the generation of motor torque, the gain G is decreased.

[0046] The command current calculation unit 82 calculates a q-axis command current Iq* to be passed through the armature windings 23 of each of the motors 20R, 20L, 40R, and 40L based on the calculated command torque Tcmd. Specifically, the command current calculation unit 82 calculates the q-axis command current Iq* (= Tcmd / Kt) by dividing the command torque Tcmd by the torque constant Kt.

[0047] The command current calculation unit 82 calculates the d-axis command current Id* to be passed through the armature windings 23 of each of the motors 20R, 20L, 40R, and 40L based on the calculated q-axis command current Iq* and the maximum current Imax that can be passed through the armature windings 23. More specifically, the command current calculation unit 82 calculates the d-axis command current Id* (=Imax-Iq*) by subtracting the q-axis command current Iq* from the maximum current Imax. The maximum current Imax is set to a value that prevents overcurrent abnormalities from occurring in each of the motors 20R, 20L, 40R, and 40L and each of the inverters 30R, 30L, 50R, and 50L.

[0048] The angle calculation unit 83 calculates the estimated electrical angle θc of the rotor 24 for each of the motors 20R, 20L, 40R, and 40L individually based on the output signal of the rotation angle sensor 62. More specifically, the angle calculation unit 83 calculates the estimated electrical angle θc by adding ½ of the resolution (30°) to the current electrical angle θr calculated based on the output signal of the rotation angle sensor 62. This reduces the effect of the difference on the calculation accuracy of the phase command currents Iu*, Iv*, and Iw*, which will be described later, even if there is a large difference between the calculated electrical angle θr and the actual electrical angle.

[0049] For example, if the calculated current electrical angle θr is 0°, the angle calculation unit 83 calculates the estimated electrical angle value θc as 30°. If the calculated current electrical angle θr is 120°, the angle calculation unit 83 calculates the estimated electrical angle value θc as 150°.

[0050] The three-phase conversion unit 84 calculates U-, V-, and W-phase command currents Iu*, Iv*, and Iw* in the three-phase fixed coordinate system individually for each of the motors 20R, 20L, 40R, and 40L based on the calculated d- and q-axis command currents Id* and Iq* and the calculated current electrical angle estimate value θc.

[0051]

number

[0052] FIG. 6 shows a flowchart of the discharge control process executed by the processor 71 of the control device .

[0053] In step S10, the discharge control unit 80 determines whether or not a command to stop the operation of the automatic guided vehicle 10 has been issued.

[0054] If it is determined that an operation stop command has been issued, the process proceeds to step S11, where the discharge control unit 80 switches off the power switches 17H and 17L.

[0055] In step S12, the instruction unit 90 instructs the changeover switch 18 to stop energizing, thereby switching the changeover switch 18 off and causing the brake device 15 to apply braking torque to each of the wheels 12R, 12L, 13R, and 13L.

[0056] In step S13, the angle calculation unit 83 calculates the current estimated electrical angle θc.

[0057] In step S14, a command torque Tcmd is calculated in a command torque calculation section 81. Furthermore, a command current calculation section 82 calculates d-axis and q-axis command currents Id* and Iq* based on the command torque Tcmd.

[0058] In step S15, the three-phase conversion unit 84 calculates U-, V-, and W-phase command currents Iu*, Iv*, and Iw* based on the electrical angle estimated value θc calculated in step S13 and the d- and q-axis command currents Id* and Iq* calculated in step S14.

[0059] In step S16, the switch control unit 85 generates drive signals for the inverters 30R, 30L, 50R, and 50L to control the detected U-, V-, and W-phase currents Iur, Ivr, and Iwr for the motors 20R, 20L, 40R, and 40L to the U-, V-, and W-phase command currents Iu*, Iv*, and Iw* calculated in step S15. This starts switching control, and discharge of residual charge in the capacitors 31 of the inverters 30R, 30L, 50R, and 50L begins.

[0060] In step S17, the discharge control unit 80 determines whether the AGV 10 is maintained in a stopped state during switching control for discharging residual charge. For example, it may be determined whether the AGV 10 is maintained in a stopped state based on the detection value of the inertial sensor 63.

[0061] If it is determined in step S17 that the vehicle is maintained in a stopped state, the process proceeds to step S18. In step S18, the discharge control unit 80 determines whether or not the discharge of residual charge from the capacitors 31 provided in each of the inverters 30R, 30L, 50R, and 50L has been completed. For example, if it is determined that the inter-terminal voltage of each capacitor 31 detected by the voltage sensor 60 is equal to or less than a voltage threshold, it may be determined that the discharge has been completed. The voltage threshold may be set to 0 or a predetermined voltage Vth slightly greater than 0. When the rated voltage of the DC power supply 14 is Vbc, the predetermined voltage Vth is set to, for example, "Vbc × 1 / 20≦Vth≦Vbc × 1 / 10" or "Vbc × 1 / 15≦Vth≦Vbc × 1 / 10".

[0062] If it is determined in step S18 that the discharge is not complete, the process proceeds to step S17, where the switching control for the discharge continues. On the other hand, if it is determined in step S18 that the discharge is complete, the discharge control ends.

[0063] If the torque generated by each of the motors 20R, 20L, 40R, and 40L exceeds the braking torque, the wheels 12R, 12L, 13R, and 13L may rotate. In this case, the AGV 10, which is in a stopped state, may attempt to move. Therefore, if it is determined in step S17 that the stopped state is not maintained, the process proceeds to step S19, where the q-axis command current Iq* used in the discharge control of each of the motors 20R, 20L, 40R, and 40L is reduced by a predetermined amount compared to the q-axis command current Iq* calculated in step S14. More specifically, the q-axis command current Iq* is reduced by reducing the gain G used in calculating the command torque Tcmd. Then, the process proceeds to step S17.

[0064] By the processing of steps S17 and S19, the q-axis command current Iq* is gradually reduced and the torque generated by each of the motors 20R, 20L, 40R, and 40L is gradually reduced until it is determined that the stopped state of the automatic guided vehicle 10 will be maintained. This allows the charge of the capacitor 31 to continue to be discharged, and maintains the stopped state of the automatic guided vehicle 10.

[0065] As described above, in this embodiment, in order to discharge the capacitor 31, switching control is performed on the inverters 30R, 30L, 50R, and 50L to pass a q-axis current in addition to a d-axis current. This allows the residual charge in the capacitor 31 to be discharged more quickly than when only the d-axis current of the d- and q-axis currents is passed. Even if torque is generated in the motors 20R, 20L, 40R, and 40L due to the flow of the q-axis current, it is possible to prevent the wheels 12R, 12L, 13R, and 13L from rotating due to the braking force of the brake device 15. This allows the automated guided vehicle 10 to be kept stopped while shortening the time from the start to the completion of discharge of the residual charge in the capacitor 31.

[0066] <Modification of the first embodiment> In step S17, the discharge control unit 80 may determine whether the AGV 10 is maintained in a stopped state based on, for example, a detection value of a wheel speed sensor. The wheel speed sensor is a sensor that detects the rotation speed of at least one of the wheels 12R, 12L, 13R, and 13L.

[0067] Second Embodiment The second embodiment will be described below with reference to the drawings, focusing on differences from the first embodiment. In this embodiment, the configuration of the brake device 15 is modified. Specifically, the brake device 15 is configured so that the braking torque applied to the wheel increases as the current passing through the brake device 15 increases. The brake device 15 is, for example, an electric brake device including a brake rotor provided on the wheel, brake pads pressed against the brake rotor, and an electric actuator capable of adjusting the pressing force of the brake pads against the brake rotor by the current passing through the brake device 15. The instruction unit 90 of the control device 70 controls the adjustment of the current passing through the brake device 15. With the power switches 17H and 17L and the selector switch 18 turned on, the instruction unit 90 can increase the braking torque as the current passing through the brake device 15 increases. On the other hand, when the selector switch 18 is turned off, power supply to the brake device 15 is stopped, and the application of braking torque from the brake device 15 to the wheel is canceled.

[0068] FIG. 7 shows a flowchart of the discharge control process executed by the processor 71.

[0069] Since the braking device 15 has a variable braking torque, the braking torque can be adjusted during discharge control. For example, after the processing of step S11, in step S20, the instruction unit 90 can adjust the braking torque by adjusting the current supplied to the braking device 15. For example, the braking torque may be reduced by setting a condition that the braking torque be equal to or greater than the command torque Tcmd, and reducing the current supplied as the voltage between the terminals of the capacitor 31 detected by the voltage sensor 60 becomes lower.

[0070] After the process of step S19, in step S20, the smaller the q-axis command current Iq*, the smaller the current supplied to the brake device 15 by the instructing unit 90. As a result, the braking torque decreases in accordance with the decrease in the torque generated by each of the motors 20R, 20L, 40R, 40L.

[0071] <Modification of the second embodiment> The series-connected brake devices 15 and changeover switches 18 corresponding to the wheels 12R, 12L, 13R, and 13L may be connected to the DC power supply 14 without passing through the high- and low-potential power switches 17H and 17L, rather than the high- and low-potential paths 16H and 16L as shown in FIG. 1 . In this case, the instructing unit 90 may, for example, impose a condition that the braking torque be equal to or greater than the command torque Tcmd, and reduce the current supplied to the brake devices 15 to reduce the braking torque as the detected value of a power supply voltage sensor that detects the voltage between the terminals of the DC power supply 14 decreases. Furthermore, the instructing unit 90 may, for example, impose a condition that the braking torque be equal to or greater than the command torque Tcmd, and reduce the current supplied to the brake devices 15 to reduce the braking torque as the q-axis command current Iq* decreases in step S20. This reduces the power consumption of the DC power supply 14.

[0072] <Third embodiment> The third embodiment will be described below with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, when the automated guided vehicle 10 is parked on an inclined road surface with an upward or downward gradient, discharge control is performed to further shorten the period until the discharge of the capacitor 31 is completed.

[0073] In detail, when the discharge control unit 80 determines that the automated guided vehicle 10 is stopped on the inclined road surface, it calculates the q-axis command current Iq* in the discharge control to rotate each wheel 12R, 12L, 13R, 13L in the direction in which the automated guided vehicle 10 climbs the inclined road surface.

[0074] This allows the q-axis command current Iq* to be increased by an amount corresponding to the component of gravity acting on the AGV 10 along the inclined road surface (i.e., the component that tries to move the AGV 10 down). Therefore, the q-axis command current Iq* in the discharge control can be increased compared to when the AGV 10 is stopped on a flat road, for example. This allows the discharge period of the capacitor 31 to be further shortened.

[0075] 8 shows a state in which the automated guided vehicle 10, which had been traveling, stops on an inclined road surface with an upward gradient. In this case, the discharge control unit 80 calculates the q-axis command current Iq* corresponding to the positive torque that attempts to rotate each of the wheels 12R, 12L, 13R, and 13L in the first direction.

[0076] 9 shows a state in which the traveling automated guided vehicle 10 stops on a downwardly inclined road surface. In this case, the discharge control unit 80 calculates the q-axis command current Iq* corresponding to the negative torque that attempts to rotate each of the wheels 12R, 12L, 13R, and 13L in a second direction that is opposite to the first direction.

[0077] FIG. 10 is a flowchart showing the discharge control process executed by the processor 71.

[0078] After the process of step S14 is completed, in step S21, it is determined based on the detection value of the inertial sensor 63 whether the inclined road surface on which the automatic guided vehicle 10 is stopped is an upward gradient or a downward gradient.

[0079] If it is determined in step S21 that the gradient is uphill, the process proceeds to step S22, and the d- and q-axis command currents Id* and Iq* calculated in step S14 are used in step S15. In this embodiment, the d- and q-axis command currents Id* and Iq* calculated in step S14 correspond to command currents that generate positive torque in the motors 20R, 20L, 40R, and 40L.

[0080] On the other hand, if it is determined in step S21 that the gradient is downward, the process proceeds to step S23, and the d- and q-axis command currents Id* and Iq* that generate negative torque in 20R, 20L, 40R, and 40L are used in step S15. For example, the d- and q-axis command currents Id* and Iq* that have the signs inverted from the d- and q-axis command currents Id* and Iq* calculated in step S14 are calculated as command currents that generate negative torque.

[0081] According to the present embodiment described above, the discharge period of the capacitor 31 can be further shortened.

[0082] <Fourth embodiment> The fourth embodiment will be described below with reference to the drawings, focusing on the differences from the third embodiment. In this embodiment, the automatic guided vehicle 10 is provided with a weight sensor that detects the weight of the automatic guided vehicle 10. When the weight detected by the weight sensor is large, the discharge control unit 80 increases the q-axis current in the discharge control more than when the weight is small.

[0083] FIG. 11 is a flowchart showing the discharge control process executed by the processor 71.

[0084] After completing the processing of step S22 or S23, the process proceeds to step S24, where the q-axis command current Iq* calculated in step S14 is increased as the weight detected by the weight sensor increases. The greater the weight, the greater the static friction force acting between each wheel 12R, 12L, 13R, 13L and the road surface. Therefore, it is considered that the greater the weight, the more the automated guided vehicle 10 can be maintained in a stopped state during discharge control, even if the q-axis current is increased to increase the torque generated by the motor.

[0085] In the automated guided vehicle 10 in which various objects are placed on the platform 11a, the discharge period of the capacitor 31 can be further shortened by increasing the q-axis command current Iq* in accordance with an increase in weight.

[0086] <Modification of the Fourth Embodiment> The processes of steps S21 to S23 in Fig. 11 may not be provided, in which case the process may proceed to step S24 after the process of step S14 is completed.

[0087] Fifth Embodiment The fifth embodiment will be described below with reference to the drawings, focusing on differences from the third and fourth embodiments. In this embodiment, the discharge control unit 80 performs discharge control by controlling the switching of the inverters 30R, 30L, 50R, and 50L so as to cause the rotation direction of the right front wheel 12R to be opposite to the rotation direction of the right rear wheel 13R and the rotation direction of the left front wheel 12L to be opposite to the rotation direction of the left rear wheel 13L. In this case, the discharge control unit 80 sets the command torques Tcmd of the motors 20R, 20L, 40R, and 40L to be the same or equivalent.

[0088] Figure 12 shows an example in which negative torque is generated in each front motor 20R, 20L to rotate each front wheel 12R, 12L in a second direction, and positive torque is generated in each rear motor 40R, 40L to rotate each rear wheel 13R, 13L in a first direction.

[0089] FIG. 13 shows an example in which a positive torque is generated in each front motor 20R, 20L to rotate each front wheel 12R, 12L in a first direction, and a negative torque is generated in each rear motor 40R, 40L to rotate each rear wheel 13R, 13L in a second direction.

[0090] Figure 14 shows an example in which negative torque is generated in the left front motor 20L and the right rear motor 40R to rotate the left front wheel 12L and the right rear wheel 13R in a second direction, and positive torque is generated in the right front motor 20R and the left rear motor 40L to rotate the right front wheel 12R and the left rear wheel 13L in a first direction.

[0091] Figure 15 shows an example in which positive torque is generated in the left front motor 20L and the right rear motor 40R to rotate the left front wheel 12L and the right rear wheel 13R in a first direction, and negative torque is generated in the right front motor 20R and the left rear motor 40L to rotate the right front wheel 12R and the left rear wheel 13L in a second direction.

[0092] According to the discharge control described above, torques of the left and right wheels aligned in the vehicle width direction of the automated guided vehicle 10 can be cancelled out, and torques of the front and rear wheels aligned in the vehicle length direction can be cancelled out. This makes it possible to increase the command torque Tcmd of each motor 20R, 20L, 40R, 40L, and further shorten the discharge period of the capacitor 31. Furthermore, because torques in the vehicle width direction and vehicle length direction can be cancelled out, the automated guided vehicle 10 can be accurately maintained in a stopped state during the discharge control.

[0093] FIG. 16 is a flowchart showing the discharge control process executed by the processor 71.

[0094] After completing the process of step S24, the process proceeds to step S25, where d- and q-axis command currents Id* and Iq* corresponding to the motors 20R, 20L, 40R, and 40L are calculated based on the d- and q-axis command currents Id* and Iq* calculated in step S14 so as to cause a q-axis current to flow that causes the rotation direction of the right front wheel 12R to be opposite to that of the right rear wheel 13R and that causes the rotation direction of the left front wheel 12L to be opposite to that of the left rear wheel 13L. Note that the method of calculating the command currents corresponding to the positive torque and the negative torque may be the same as that described in the third embodiment.

[0095] According to the present embodiment described above, the automatic guided vehicle 10 can be accurately maintained in a stopped state during discharge control, and the discharge period of the capacitor 31 can be further shortened.

[0096] <Other embodiments> The above-described embodiments may be modified as follows.

[0097] In the fifth embodiment, the discharge control may be performed in the manner shown in Fig. 17 or 18. Fig. 17 shows an example in which the discharge control unit 80 performs the discharge control so that positive torque is generated in each of the left motors 20L, 40L to rotate each of the left wheels 12L, 13L in a first direction, and negative torque is generated in each of the right motors 20R, 40R to rotate each of the right wheels 12R, 13R in a second direction.

[0098] Figure 18 shows an example in which the discharge control unit 80 performs discharge control so as to generate negative torque in each of the left motors 20L, 40L to rotate each of the left wheels 12L, 13L in the second direction, and generate positive torque in each of the right motors 20R, 40R to rotate each of the right wheels 12R, 13R in the first direction.

[0099] In a state where the application of braking torque from the brake device 15 to the wheels is canceled by the instruction unit 90, the discharge control shown in FIGS. 12 to 15 of the fifth embodiment and FIGS. 17 and 18 of the modified example may be executed.

[0100] In each of the above embodiments, the discharge control unit 80 determines whether a specific wheel, which is at least one of the wheels 12R, 12L, 13R, and 13L, has rotated during discharge control. If the discharge control unit 80 determines that the specific wheel has rotated, in step S19, the discharge control unit 80 may perform switching control of the inverters 30R, 30L, 50R, and 50L so as to reduce the q-axis current flowing through the armature winding 23 of the motor corresponding to the specific wheel among the motors 20R, 20L, 40R, and 40L compared to before it was determined that the specific wheel had rotated.

[0101] The capacitor 31 is not limited to being provided individually for each of the inverters 30R, 30L, 50R, and 50L, but may be a capacitor common to all of the inverters 30R, 30L, 50R, and 50L. In this case, the control device 70 may perform switching control of only some of the inverters 30R, 30L, 50R, and 50L during discharge control.

[0102] The resolution of the electrical angle detected by the rotation angle sensor is not limited to 60°. For example, as described above, if the resolution is "360° / (P×6)", the number of pole pairs P may be 2 or more.

[0103] A transmission may be provided in the power transmission path between the rotor and the wheels. For example, the transmission may be a reduction gear that reduces the rotational speed of the rotor. In this case, the discharge control unit 80 may calculate d- and q-axis command currents Id* and Iq* in the discharge control such that the torque applied to the wheels from the reduction gear is equal to or less than the braking torque of the brake device 15.

[0104] The object to which the braking torque is applied by the brake device is not limited to the wheels, but may also be, for example, the rotor of the motor or a component of the power transmission path from the rotor to the wheels.

[0105] The automated guided vehicle is not limited to a four-wheel vehicle, but may be, for example, a six-wheel vehicle with three sets of drive wheels aligned in the vehicle width direction, or a two-wheel vehicle with one set. Also, the automated guided vehicle is not limited to one in which all wheels are drive wheels, but may be one in which some wheels are driven wheels.

[0106] The automated guided vehicles used in factories are not limited to AGVs, but may also be, for example, autonomous mobile robots (AMRs).

[0107] Furthermore, the small electric vehicle is not limited to an unmanned guided vehicle, but may be, for example, an electric wheelchair or a senior cart with a maximum speed of 20 km / h or less, 15 km / h or less, or 10 km / h or less. Furthermore, the vehicle is not limited to a small electric vehicle.

[0108] The control unit and method described herein may be implemented by a special-purpose computer configured by configuring a processor and memory programmed to perform one or more functions embodied in a computer program. Alternatively, the control unit and method described herein may be implemented by a special-purpose computer configured by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit and method described herein may be implemented by one or more special-purpose computers configured by combining a processor and memory programmed to perform one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0109] 10...automated guided vehicle, 12L, 12R, 13L, 13R...wheel, 15...brake device, 20R, 20L, 40R, 40L...motor, 30R, 30L, 50R, 50L...inverter, 31...capacitor, 70...control device

Claims

1. a rotor (24) for applying a rotational force to wheels (12L, 12R, 13L, 13R) of a vehicle (10), and a motor (20R, 20L, 40R, 40L) having an armature winding (23); an inverter (30R, 30L, 50R, 50L) having upper and lower arm switches (SH, SL) connected in series, the upper and lower arm switches being electrically connected to the armature winding; a capacitor (31) connected in parallel to the series connection of the upper and lower arm switches; a brake device (15) that applies a braking torque to at least one of the wheel, the rotor, and a power transmission path from the rotor to the wheel, the braking torque preventing the wheel from rotating; In a vehicle control device (70) applied to the vehicle, an instruction unit (90) that instructs the brake device to apply a braking torque; a discharge control unit (80) that performs discharge control, which is switching control of the upper and lower arm switches to pass a d-axis current and a q-axis current to the armature winding for discharging the capacitor, when the instruction unit instructs application of a braking torque; A vehicle control device comprising:

2. The vehicle includes a rotation angle sensor (62) that detects the electrical angle of the rotor, 2. The vehicle control device according to claim 1, wherein the discharge control unit performs the switching control based on the electrical angle detected by the rotation angle sensor so that the torque applied from the motor to the wheels is equal to or less than the braking torque of the brake device.

3. The resolution of the electrical angle detected by the rotation angle sensor is 360° / (P×6), The vehicle control device according to claim 2 , wherein P is the number of pole pairs of the rotor.

4. The discharge control unit determining whether the wheel rotates during a period from when the discharge of the capacitor is started to when the discharge control is completed; 4. The vehicle control device according to claim 3, wherein, when it is determined that the wheel has rotated, the switching control is performed so as to reduce the q-axis current before the discharge of the capacitor is completed, compared to when it is determined that the wheel is not rotating.

5. The discharge control unit determining whether the vehicle is located on an inclined road surface, either an uphill or downhill slope; 5. The vehicle control device according to claim 1, wherein, when it is determined that the vehicle is located on the sloped road surface, the switching control is performed so as to pass a q-axis current that rotates the wheels in a direction in which the vehicle climbs the sloped road surface.

6. The vehicle has, as the wheels: a first right wheel (12R) and a first left wheel (12L) arranged in a width direction of the vehicle; a second right wheel (13R) and a second left wheel (13L) arranged in a vehicle length direction of the vehicle and arranged in a vehicle width direction with respect to the first right wheel and the first left wheel; Equipped with The vehicle includes, as the motor: a right-side first motor (20R) for rotating the right-side first wheel; a first left motor (20L) that rotates the first left wheel; a right-side second motor (40R) for rotating the right-side second wheel; a second left motor (40L) for rotating the second left wheel; Equipped with The vehicle includes, as the inverter: a right-side first inverter (30R) electrically connected to the armature winding of the right-side first motor; a left-side first inverter (30L) electrically connected to the armature winding of the left-side first motor; a right-side second inverter (50R) electrically connected to the armature winding of the right-side second motor; a second left inverter (50L) electrically connected to the armature winding of the second left motor; The vehicle control device according to any one of claims 1 to 4, comprising:

7. 7. The vehicle control device according to claim 6, wherein the discharge control unit performs the switching control of each of the right-side first inverter, the right-side second inverter, the left-side first inverter, and the left-side second inverter so as to cause a q-axis current to flow that causes the rotation direction of the right-side first wheel to be opposite to the rotation direction of the right-side second wheel and the rotation direction of the left-side first wheel to be opposite to the rotation direction of the left-side second wheel.

8. a rotor (24) for applying a rotational force to wheels (12L, 12R, 13L, 13R) of a vehicle (10), and a motor (20R, 20L, 40R, 40L) having an armature winding (23); an inverter (30R, 30L, 50R, 50L) having upper and lower arm switches (SH, SL) connected in series, the upper and lower arm switches being electrically connected to the armature winding; a capacitor (31) connected in parallel to the series connection of the upper and lower arm switches; In a vehicle control device (70) applied to the vehicle, The vehicle has, as the wheels: a first right wheel (12R) and a first left wheel (12L) arranged in a width direction of the vehicle; a second right wheel (13R) and a second left wheel (13L) arranged in a vehicle length direction of the vehicle and arranged in a vehicle width direction with respect to the first right wheel and the first left wheel; Equipped with The vehicle includes, as the motor: a right-side first motor (20R) for rotating the right-side first wheel; a first left motor (20L) that rotates the first left wheel; a right-side second motor (40R) for rotating the right-side second wheel; a second left motor (40L) for rotating the second left wheel; Equipped with The vehicle includes, as the inverter: a right-side first inverter (30R) electrically connected to the armature winding of the right-side first motor; a left-side first inverter (30L) electrically connected to the armature winding of the left-side first motor; a right-side second inverter (50R) electrically connected to the armature winding of the right-side second motor; a second left inverter (50L) electrically connected to the armature winding of the second left motor; Equipped with a discharge control unit (80) that performs discharge control, which is switching control of the upper and lower arm switches of each of the right-side first inverter, the right-side second inverter, the left-side first inverter, and the left-side second inverter, in order to pass a d-axis current and a q-axis current for discharging the capacitor through the armature windings of each of the right-side first motor, the left-side first motor, the right-side second motor, and the left-side second motor; The discharge control unit performs the switching control of each of the right side first inverter, the right side second inverter, the left side first inverter, and the left side second inverter so as to cause a q-axis current to flow that causes the rotation direction of the right side first wheel to be opposite to the rotation direction of the right side second wheel and the rotation direction of the left side first wheel to be opposite to the rotation direction of the left side second wheel.

9. 7. The vehicle control device according to claim 6, wherein the discharge control unit performs the switching control of each of the right-side first inverter, the right-side second inverter, the left-side first inverter, and the left-side second inverter so as to cause a q-axis current to flow that causes a rotation direction of the right-side first wheel to be opposite to a rotation direction of the left-side first wheel and a rotation direction of the right-side second wheel to be opposite to a rotation direction of the left-side second wheel.

10. The discharge control unit acquiring weight information of the vehicle; 5. The vehicle control device according to claim 1, wherein, based on the acquired weight information, when the weight of the vehicle is large, the q-axis current in the discharge control is increased more than when the weight of the vehicle is small.

11. 5. The vehicle control device according to claim 1, wherein the brake device is a non-excitation brake device that applies a braking torque in a non-energized state and cancels the application of the braking torque in a powered state.

12. The brake device is configured so that the braking torque increases as the current flowing therethrough increases, The discharge control unit 5. The vehicle control device according to claim 1, wherein the instruction unit issues an instruction to reduce the energizing current as the q-axis current in the discharge control decreases.

13. a rotor (24) for applying a rotational force to wheels (12L, 12R, 13L, 13R) of a vehicle (10), and a motor (20R, 20L, 40R, 40L) having an armature winding (23); an inverter (30R, 30L, 50R, 50L) having upper and lower arm switches (SH, SL) connected in series, the upper and lower arm switches being electrically connected to the armature winding; a capacitor (31) connected in parallel to the series connection of the upper and lower arm switches; a brake device (15) that applies a braking torque to at least one of the wheel, the rotor, and a power transmission path from the rotor to the wheel, the braking torque preventing the wheel from rotating; In the program applied to the vehicle, A processor (71) an instruction process for instructing the brake device to apply a braking torque; a discharge control process for performing a discharge control, which is a switching control of the upper and lower arm switches for causing a d-axis current and a q-axis current to flow through the armature winding in order to discharge the capacitor, when the application of a braking torque is instructed by the instruction process; A program that executes.

14. a rotor (24) for applying a rotational force to wheels (12L, 12R, 13L, 13R) of a vehicle (10), and a motor (20R, 20L, 40R, 40L) having an armature winding (23); an inverter (30R, 30L, 50R, 50L) having upper and lower arm switches (SH, SL) connected in series, the upper and lower arm switches being electrically connected to the armature winding; a capacitor (31) connected in parallel to the series connection of the upper and lower arm switches; a brake device (15) that applies a braking torque to at least one of the wheel, the rotor, and a power transmission path from the rotor to the wheel, the braking torque preventing the wheel from rotating; A vehicle control method applied to the vehicle comprising: an instruction step of instructing the brake device to apply a braking torque; a discharge control step of performing, in a state in which application of a braking torque is instructed by the instructing step, discharge control that is switching control of the upper and lower arm switches to cause a d-axis current and a q-axis current to flow through the armature winding for discharging the capacitor; A vehicle control method comprising:

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