Control device for electric vehicle, electric drive device, program, and control method for electric vehicle

Abstract

A control device (80) is applied to an electric vehicle (10) that conveys an object (15) and that comprises: drive wheels (12); a motor (31) for rotationally driving the drive wheels; and an inverter (34) electrically connected to armature windings (31a) of the motor. This control device comprises: switch control units (90-93) that perform switching control of the inverter in order to feedback-control the rotational speed of the drive wheels or the rotational speed of a rotor of the motor so that the same becomes a command rotational speed; and a gain setting unit (94) that makes the control gain of the feedback control variable, on the basis of the rotational speed and / or the total weight of the object and the electric vehicle.

Description

Control device for electric vehicle, electric drive device, program, and control method for electric vehicle Cross-reference to related applications

[0001] This application is based on Japanese Application No. 2024-221496 filed on December 18, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a control device for an electric vehicle, an electric drive device, a program, and a control method for an electric vehicle.

[0003] Conventionally, for example, as described in Patent Document 1, an electric vehicle that includes drive wheels, a motor for rotationally driving the drive wheels, and an inverter electrically connected to the armature winding of the motor and transports an object is known.

[0004] Japanese Patent Application Laid-Open No. 2011-93676

[0005] Appropriate running control according to the state of the electric vehicle, such as the weight of an object loaded on the electric vehicle, is desired.

[0006] A main object of the present disclosure is to provide a control device for an electric vehicle, an electric drive device, a program, and a control method for an electric vehicle that can execute appropriate running control according to the state of the electric vehicle.

[0007] In a control device for an electric vehicle applied to an electric vehicle that includes drive wheels, a motor for rotationally driving the drive wheels, and an inverter electrically connected to the armature winding of the motor and transports an object, a switch control unit that performs switching control of the inverter to feedback-control the rotational speed of the drive wheels or the rotational speed of the rotor of the motor to a command rotational speed, and a gain setting unit that makes the control gain of the feedback control variable based on at least one of the total weight of the object and the electric vehicle and the rotational speed are provided.

[0008] In the present disclosure, in a control system that feedback-controls the rotational speed of the drive wheels or the rotor to the command rotational speed, the control gain is made variable based on at least one of the total weight of the object and the electric vehicle and the rotational speed. Thereby, appropriate running control according to the state of the electric vehicle can be executed.

[0009] The above-mentioned objectives and other objectives, features and advantages of this disclosure will become clearer from the following detailed description with reference to the attached drawings. The drawings are as follows: Figure 1 is an overall configuration diagram of an automated guided vehicle according to the first embodiment; Figure 2 is a diagram showing the electric drive unit and its surrounding configuration; Figure 3 is a block diagram of the rotational speed control process by the controller; Figure 4 is a schematic diagram of an automated guided vehicle traveling on a road surface; Figure 5 is a diagram showing the rotational speed control system; Figure 6 is a diagram showing the relationship between total weight and proportional gain; Figure 7 is a diagram showing the relationship between friction coefficient and integral gain; Figure 8 is a flowchart of the gain setting process; Figure 9 is a diagram showing an example of acceleration / deceleration period and constant speed period; Figure 10 is a block diagram of the rotational speed control process corresponding to the left and right wheels; and Figure 11 is a flowchart of the integral gain setting process according to the second embodiment.

[0010] Multiple embodiments will be described with reference to the drawings. In multiple embodiments, functionally and / or structurally corresponding and / or related parts may be given the same reference numeral, or reference numerals that differ by hundreds or more digits. For corresponding and / or related parts, refer to the descriptions of other embodiments.

[0011] <First Embodiment> Hereinafter, a first embodiment of the control device according to the present disclosure will be described with reference to the drawings. In this embodiment, the control device is mounted on an automated guided vehicle (AGV) (small electric vehicle). The AGV is an AGV (Automatic Guided Vehicle) that is guided by magnetic tape (magnetic line) in a factory or warehouse, for example.

[0012] As shown in Figure 1, the automated guided vehicle (AGV) 10 comprises a vehicle body 11, four sets (multiple sets) of drive wheels 12 and drive shafts 13, and a drive unit 20. Each drive wheel 12 is connected to each drive shaft 13 and rotates around each drive shaft 13. The four drive wheels 12 are the left and right front wheels and left and right rear wheels of the AGV 10.

[0013] The drive unit 20 is housed within the vehicle body 11. The drive unit 20 includes an electric drive device 30 corresponding to each drive wheel 12, a brake 60 corresponding to each drive wheel 12, a higher-level controller 70, a battery 71, a main switch 73, a brake switch 75, and sensors 77, etc. The main switch 73 and the brake switch 75 are, for example, relays (specifically, mechanical relays). In Figure 1, power lines PL1 and PL2 are shown as solid lines, and the signal line SL is shown as a dashed line.

[0014] Each electric drive unit 30 drives each drive shaft 13. Each electric drive unit 30 is fixed to the vehicle body 11. Each electric drive unit 30 is equipped with an MCU (Motor Control Unit) and a reduction gear 59.

[0015] Each MCU is connected to the battery 71 by a power line PL1. A main switch 73 is provided between the battery 71 and the four MCUs on the power line PL1. The main switch 73 can be switched between ON, which supplies power from the battery 71 to the four MCUs (electric drive units 30), and OFF, which cuts off power to the four MCUs. When the main switch 73 is ON, each MCU is powered and driven by the battery 71.

[0016] The reduction gear 59 reduces the rotational speed of the motor 31 (see Figure 2) of the MCU and transmits it to the drive shaft 13. The reduction gear 59 is, for example, a planetary gear mechanism or a cycloidal gear mechanism.

[0017] Each brake 60 applies braking force to each drive shaft 13. Each brake 60 is fixed to the vehicle body 11. Each brake 60 is connected to the battery 71 by a power line PL2. A brake switch 75 is provided between the battery 71 and the four brakes 60 in the power line PL2. The brake switch 75 can be switched between ON, which supplies power from the battery 71 to the four brakes 60, and OFF, which cuts off power to the four brakes 60. Each brake 60 is powered and driven by the battery 71 when the brake switch 75 is ON. Each brake 60 is an unexcited electromagnetic brake that applies braking force to each drive shaft 13, for example, when no power is supplied. The braking force applied by each brake 60 to each drive shaft 13 can also be controlled by each MCU or a higher-level controller 70.

[0018] The upper-level controller 70 and the four MCUs are connected to each other by a signal line SL. The upper-level controller 70 is, for example, an ECU (Electronic Control Unit) equipped with a CPU, ROM, RAM, and input / output interface. The signal line SL is, for example, a signal line that conforms to the CAN (Controller Area Network) communication standard. The upper-level controller 70 and the four MCUs send and receive information to each other through the signal line SL. The upper-level controller 70 controls the four MCUs by inputting commands to each MCU through the signal line SL. The upper-level controller 70 switches the main switch 73 and the brake switch 75 on and off. The upper-level controller 70 keeps the main switch 73 and the brake switch 75 on while the drive unit 20 is operating.

[0019] The sensors 77 include, for example, an abnormal stop button, a collision detection switch, a magnetic sensor for detecting the magnetism of a magnetic tape, a position information sensor for reading floor position information, and a human presence sensor for detecting people. The detection results from the sensors 77 are input to the higher-level controller 70.

[0020] Figure 2 is a block diagram showing the electric drive unit 30 and its surrounding configuration. Since the four electric drive units 30 have similar configurations, we will explain using one electric drive unit 30 as an example.

[0021] The electric drive unit 30 is equipped with multiple power switches 32, inverters 34, current sensors 41, and angle sensors 42, each in multiple systems (specifically, two systems). The electric drive unit 30 is equipped with one motor 31, a reduction gear 59, and a controller 80. The power switch 32 is, for example, a relay (specifically, for example, a mechanical relay).

[0022] Each inverter 34 is connected to the battery 71 via a power switch 32 and a main switch 73. The power switch 32 can be switched between ON, which supplies power from the battery 71 to the inverter 34, and OFF, which cuts off the power.

[0023] The inverter 34 is equipped with upper and lower arm switches corresponding to each phase, and is, for example, a three-phase inverter. The inverter 34 converts the DC power supplied from the battery 71 into AC power and supplies the converted AC power to the armature winding 31a of the motor 31.

[0024] The motor 31 is, for example, a three-phase motor and comprises one rotor (not shown) and two armature windings 31a. AC power is input to each armature winding 31a from the inverter 34 of each system.

[0025] Each current sensor 41 detects the current flowing through the armature winding 31a of each system. Each angle sensor 42 detects the rotation angle (electrical angle) of the rotor. The detected values ​​from the current sensors 41 and angle sensors 42 are input to the controller 80.

[0026] The electric drive unit 30 is equipped with a voltage sensor 43 that detects the voltage between the terminals of the battery 71. The value detected by the voltage sensor 43 is input to each controller 80.

[0027] The controller 80 is an ECU that performs various controls on the electric drive unit 30, and comprises a processor 81 as hardware, a storage unit 82, and a communication bus 83 that connects the processor 81 and the storage unit 82.

[0028] The memory unit 82 includes memory and storage as hardware. The memory is a storage device for storing data used in the processing of the controller 80. The memory provides the processor 81 with a temporary workspace for use when the processor 81 performs processing. The memory includes, for example, ROM or RAM. The storage is a storage device that stores various programs and data for the processor 81 to read and execute, and is a non-transitory tangible storage medium. The storage includes, for example, an HDD or flash memory. The storage stores program information and the like for processing described later.

[0029] For example, program information stored on a non-transitional physical recording medium is installed in the storage unit 82. The recording medium is, for example, a USB memory stick, a CD-ROM, or a DVD. Also, for example, program information transmitted via a communication network, such as OTA (Over The Air), is installed in the storage unit 82.

[0030] The controller 80 controls the power switches 32 of each system to turn on or off. Specifically, the controller 80 keeps the power switches 32 on while the electric drive unit 30 is operating. The controller 80 controls the switching of the inverters 34 of each system based on commands from the higher-level controller 70, the detected values ​​of the current sensors 41 and angle sensors 42 of each system, and the detected values ​​of the voltage sensor 43. The controller 80 controls the switching of the inverters 34 of each system so that the rotational speed of the drive wheels 12 corresponding to itself matches the commanded rotational speed received from the higher-level controller 70.

[0031] Figure 3 is a block diagram of the processing performed by the controller 80.

[0032] In the controller 80, the speed calculation unit 90 calculates the rotational speed Nr of the drive wheel 12 based on the value detected by the angle sensor 42. Specifically, the speed calculation unit 90 calculates the rotational speed Nr based on the value detected by the angle sensor 42 and the gear ratio (specifically the reduction ratio) of the reduction gear 59.

[0033] The speed deviation calculation unit 91 calculates the rotational speed difference ΔN (= N* - Nr), which is the difference between the commanded rotational speed N* input from the upper controller 70 and the calculated rotational speed Nr.

[0034] The speed feedback control unit 92 calculates the d-axis command current Id* and the q-axis command current Iq* to be flowed through the armature winding 31a as manipulated variables for feedback control to set the calculated rotational speed difference ΔN to 0. In this embodiment, the feedback control is proportional-integral control. Therefore, the speed feedback control unit 92 calculates the d-axis command current Id* and the q-axis command current Iq* using the following equations (eq1) and (eq2). In the following equations (eq1) and (eq2), Kp is the proportional gain for calculating the d and q-axis command currents Id* and Iq*, and Ki is the integral gain for calculating the d and q-axis command currents Id* and Iq*.

[0035]

[0036] The current feedback control unit 93 calculates the d,q axis command voltages Vd* and Vq* to be applied to the armature winding 31a as manipulated variables for feedback control of the d,q axis command currents Id* and Iq* calculated by the speed feedback control unit 92 to the d,q axis currents Idr and Iqr flowing through the armature winding 31a. The feedback control in the current feedback control unit 93 is, for example, proportional-integral control. The current feedback control unit 93 calculates the d,q axis currents Idr and Iqr based on the detected values ​​of the current sensor 41 and the angle sensor 42.

[0037] The current feedback control unit 93 converts the d and q axis command voltages Vd* and Vq* in the two-phase rotating coordinate system (dq-axis coordinate system) into U, V, and W phase command voltages Vu*, Vv*, and Vw* in the three-phase fixed coordinate system (UVW coordinate system) based on the values ​​detected by the angle sensor 42. Based on the converted U, V, and W phase command voltages Vu*, Vv*, and Vw* and the values ​​detected by the voltage sensor 43, the current feedback control unit 93 generates drive signals to turn on or off the upper and lower arm switches of each phase of the inverter 34. The current feedback control unit 93 supplies the generated drive signals to the gates of the upper and lower arm switches of each phase. This controls the switching of the upper and lower arm switches of the inverter 34 so that the rotational speed Nr becomes the commanded rotational speed N*. In this embodiment, the speed calculation unit 90, the speed deviation calculation unit 91, the speed feedback control unit 92, and the current feedback control unit 93 correspond to the "switch control unit".

[0038] In this embodiment, the controller 80 includes a gain setting unit 94 to vary the control gains Kp and Ki of the feedback control in the speed feedback control unit 92 based on the total weight of the object mounted on the automated guided vehicle 10 and the automated guided vehicle 10 itself. The method for setting the control gains will be described below with reference to Figures 4 and 5.

[0039] Figure 4 is a schematic diagram of the automated guided vehicle (AGV) 10. In Figures 4 and 5, Vr is the travel speed of the AGV 10, and V* is the commanded travel speed of the AGV 10. r is the radius of the drive wheel 12, and Trq is the torque of the drive wheel 12. The relationship between r, Trq, and F is "F = Trq / r". M is the total weight of the AGV 10 and the transported object 15, and B is the coefficient of friction (specifically, the coefficient of kinetic friction) of the frictional force acting between the drive wheel 12 and the road surface 16. s is the Laplace operator.

[0040] In Figure 5, 100 is a PI controller that takes the deviation between the travel speed Vr and the commanded travel speed V* as input and outputs the torque Trq. 101 is a plant model of the automated guided vehicle 10 that takes the torque Trq as input and outputs the travel speed Vr. τ is the target time constant in the PI controller 100.

[0041] In the control system shown in FIG. 5, the following equation (eq3) holds. According to the following equation (eq3), the control system shown in FIG. 5 becomes an ideal first-order lag system.

[0042] The PI controller 100 is expressed as in the following equation (eq4).

[0043] In the above equation (eq4), "M / τ" in the first term represents the proportional gain, and "B / τ" in the second term represents the integral gain. "V* - Vr", which is the input of the PI controller 100, corresponds to the rotational speed difference ΔN in FIG. 3. Therefore, the proportional gain Kp in the above equations (eq1) and (eq2) corresponds to the first term in the above equation (eq4), and the integral gain Ki in the above equations (eq1) and (eq2) corresponds to the second term in the above equation (eq4).

[0044] The proportional gain (M / τ) in the first term of the above equation (eq4) increases as the total weight M increases. Therefore, as shown in FIG. 6, the gain setting unit 94 increases the proportional gain Kp as the total weight M increases.

[0045] The integral gain (B / τ) in the second term of the above equation (eq4) increases as the friction coefficient B increases. Therefore, as shown in FIG. 7, the gain setting unit 94 increases the integral gain Ki as the friction coefficient B increases.

[0046] By setting the control gain in this way, the acceleration and deceleration of the automated guided vehicle 10 can be set to appropriate values according to the total weight M, and stable running of the automated guided vehicle 10 can be realized.

[0047] FIG. 8 is a flowchart of the process executed by the controller 80 (specifically, the gain setting unit 94).

[0048] In step S10, the controller 80 acquires the commanded rotational speed N* from the upper controller 70.

[0049] In steps S11 and S12, the controller 80 performs a process to estimate the total weight M without using a weight sensor to detect the total weight M. Specifically, in step S11, the controller 80 determines, for example, whether the automated guided vehicle 10 is accelerating or decelerating based on the commanded rotational speed N*. Figure 9 shows an example of the progression of the commanded rotational speed N*. In Figure 9, the period from time t1 to t2 is the acceleration period, and the period from time t3 to t4 is the deceleration period. In the equation of motion of the automated guided vehicle 10 transporting the object 15, the inertial force term is expressed as "M × s × Vr". Since "s × Vr" corresponds to acceleration or deceleration, the inertial force term becomes 0 if the vehicle is not accelerating or decelerating. For this reason, the process in step S11 is provided.

[0050] If the controller 80 determines that the vehicle is accelerating or decelerating, it determines that the conditions for executing the weight estimation process are met and proceeds to step S12. In step S12, the controller 80 estimates the total weight M. In this embodiment, the controller 80 estimates the total weight M based on the detected value of the current sensor 41 and the detected value of the angle sensor 42. The detected value of the current sensor 41 correlates with the torque Trq, and the torque Trq correlates with the driving force F. In addition, the acceleration / deceleration (s × Vr) of the automated guided vehicle 10 can be determined based on the detected value of the angle sensor 42. According to the plant model 101 in Figure 5, the following equation (eq5) holds true in the transfer function that takes the driving force F as input and the travel speed Vr as output.

[0051] The above equation (eq5) shows the relationship between the driving force F and acceleration / deceleration (s × Vr) and the total weight M. From the above, the controller 80 estimates the total weight M based on the detected value of the current sensor 41 and the detected value of the angle sensor 42. Specifically, the controller 80 may, for example, use the detected value of the current sensor 41 and the detected value of the angle sensor 42 as input and estimate the total weight M using an algorithm such as the successive least squares method, the fixed trace method, or the Kalman filter.

[0052] After step S12 is completed, or if a negative determination is made in step S11, the controller 80 performs a process to estimate the friction coefficient B in steps S13 and S14. Specifically, in step S13, the controller 80 determines, for example, whether the automated guided vehicle 10 is traveling at a constant speed based on the commanded rotational speed N*. In the example shown in Figure 9, the period from time t2 to t3 is the constant speed travel period.

[0053] If the controller 80 determines that the vehicle is traveling at a constant speed, it determines that the conditions for estimating the friction coefficient B are met and proceeds to step S14. In this embodiment, the controller 80 estimates the friction coefficient B based on the detected value of the current sensor 41 and the detected value of the angle sensor 42. The detected value of the current sensor 41 correlates with the torque Trq, and the torque Trq correlates with the driving force F. In addition, the travel speed Vr of the automated guided vehicle 10 can be determined based on the detected value of the angle sensor 42. According to the plant model 101 in Figure 5, in a transfer function that takes the driving force F as input and the travel speed Vr as output, if the condition of constant speed travel (i.e., "s × Vr = 0") is imposed, the following equation (eq6) holds. From the above, the detected value of the current sensor 41 and the detected value of the angle sensor 42 are used to calculate the friction coefficient B.

[0054] Specifically, the controller 80 can take the detected values ​​from the current sensor 41 and the angle sensor 42 as inputs and estimate the friction coefficient B using an algorithm such as the successive least squares method, the fixed trace method, or the Kalman filter.

[0055] After step S14 is completed, or if a negative determination is made in step S13, the controller 80 proceeds to step S15, and increases the proportional gain Kp as the total weight M increases in step S12. The controller 80 may set the proportional gain Kp to increase continuously or in steps as the total weight M increases. If the controller 80 has not been able to perform the estimation process for the total weight M, it may use the default value of the total weight M to set the proportional gain Kp.

[0056] In the subsequent step S16, the controller 80 increases the integral gain Ki as the friction coefficient B estimated in step S14 increases. The controller 80 can either continuously increase the integral gain Ki as the friction coefficient B increases, or increase it in steps. If the controller 80 has not been able to perform the friction coefficient B estimation process, it can use the default value of the friction coefficient B to set the integral gain Ki.

[0057] According to the embodiment described above, in a control system that feeds back the rotational speed of the drive wheels 12 to a commanded rotational speed N*, it is possible to perform appropriate driving control of the automated guided vehicle 10 according to the total weight M.

[0058] In practice, a command rotation speed corresponding to each of the left and right drive wheels 12 is set. In Figure 10, the command value setting unit 95 of the automated guided vehicle 10 calculates the command rotation speed Nright* for the right drive wheel 12 and the command rotation speed Nleft* for the left drive wheel 12 based on the command rotation speed N* input from the higher-level controller 70.

[0059] More specifically, when the command value setting unit 95 determines that the automated guided vehicle 10 is instructed to travel in a straight line, it sets the command rotation speeds Nright* and Nleft* so that the left and right drive wheels 12 rotate in the same direction and at the same rotation speed. Specifically, the command value setting unit 95 sets the command rotation speeds Nright* and Nleft* to the input command rotation speed N*. The set command rotation speed Nright* for the right drive wheel 12 is input to the controller 80 corresponding to the right drive wheel 12. The set command rotation speed Nleft* for the left drive wheel 12 is input to the controller 80 corresponding to the left drive wheel 12.

[0060] On the other hand, if the command value setting unit 95 determines that the automated guided vehicle 10 is instructed to travel around a curve (turn), it performs wheel speed difference control to create a difference between the commanded rotation speed Nright* of the right drive wheel 12 and the commanded rotation speed Nleft* of the left drive wheel 12. Specifically, the command value setting unit 95 rotates both the left and right drive wheels 12 in the same direction and sets the commanded rotation speed Nright* of the right drive wheel 12 and the commanded rotation speed Nleft* of the left drive wheel 12 so that the rotation speed of the drive wheel 12 in the instructed turning direction is lower than the rotation speed of the remaining drive wheel 12.

[0061] For example, if the command value setting unit 95 determines that a right turn is instructed, it sets "Nright* < N*" and "Nleft* > N*". On the other hand, if the command value setting unit 95 determines that a left turn is instructed, it sets "Nright* > N*" and "Nleft* < N*".

[0062] <Second Embodiment> The second embodiment will now be described, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the controller 80 (gain setting unit 94) sets the integral gain Ki in the extremely low-speed driving mode to be greater than the integral gain Ki in the normal mode, as shown in Figure 11.

[0063] More specifically, in step S20, the controller 80 determines whether the currently instructed driving mode of the automated guided vehicle 10 is the extremely low-speed driving mode or the normal driving mode. The normal driving mode is a driving mode in which the driving speed Vr of the automated guided vehicle 10 is "0.5 km / h ≤ Vr ≤ 20 km / h". For example, the normal driving mode is a driving mode of "0.5 km / h ≤ Vr ≤ 15 km / h", "0.5 km / h ≤ Vr ≤ 10 km / h", "0.5 km / h ≤ Vr ≤ 5 km / h", or "0.5 km / h ≤ Vr ≤ 2 km / h".

[0064] The extremely low-speed driving mode is a mode in which the driving speed is lower than the normal driving mode, specifically a driving mode where, for example, "0 < Vr ≤ 0.1 km / h".

[0065] If the controller 80 determines in step S20 that it is in normal driving mode, it proceeds to step S21 and sets the proportional gain Kp and integral gain Ki for normal driving mode. Then, the controller 80 performs the processing of the first embodiment shown in Figure 8, etc.

[0066] On the other hand, if the controller 80 determines in step S20 that it is in an extremely low-speed driving mode, it proceeds to step S22 and sets the integral gain Ki to a value that is 5 times or more and 50 times or less the integral gain Ki in normal mode.

[0067] In the extremely low-speed driving mode, the rotational speed Nr of the drive wheels 12 may drop significantly from the commanded rotational speed N* due to steps (for example, magnetic tape) on the road surface of the automated guided vehicle 10. In this case, although feedback control is used to make the rotational speed Nr follow the commanded rotational speed N*, the tracking performance deteriorates when using proportional control with a proportional gain Kp because the rotational speed difference ΔN is small. Therefore, in this embodiment, the integral gain Ki is increased significantly in the extremely low-speed driving mode compared to the integral gain Ki in the normal driving mode. This suppresses the occurrence of situations where tracking performance deteriorates. After setting the integral gain, the controller 80 performs the processing of the first embodiment as shown in Figure 8.

[0068] Furthermore, the integral gain Ki in the extremely low-speed driving mode should be set to a value that is, for example, 10 times or more and 50 times or less the integral gain Ki in the normal mode, 10 times or more and 30 times or less the integral gain Ki in the normal mode, or 15 times or more and 25 times or less the integral gain Ki in the normal mode.

[0069] According to the embodiment described above, it is possible to suppress the occurrence of a situation in which the responsiveness of the rotational speed Nr to the commanded rotational speed N* decreases during extremely low-speed driving mode.

[0070] <Other Embodiments> The above embodiments may be modified and implemented as follows.

[0071] The gain setting unit 94 may vary the integral gain Ki in addition to or instead of the proportional gain Kp based on the total weight M. For example, the gain setting unit 94 may set the integral gain Ki to be larger as the total weight M increases.

[0072] - The gain setting unit 94 may, for example, set the integral gain Ki to be larger as the commanded rotational speed N* increases.

[0073] - In the gain setting process shown in Figure 8, the weight estimation process does not necessarily have to be performed. In this case, the gain setting unit 94 can set the proportional gain Kp based, for example, on the detected value of a weight sensor, which is a sensor provided by the automated guided vehicle 10 that detects the weight of the transported object, or on the weight information of the object 15 transmitted from the higher-level controller 70.

[0074] The feedback control in the speed feedback control unit 92 is not limited to proportional-integral control, but may also include, for example, differential control. In this case, the gain setting unit 94 may make the differential gain in the differential control variable based on the estimated weight mc and friction coefficient B.

[0075] In the speed feedback control system, the rotational speed Nm of the motor 31 rotor may be used instead of the rotational speed Nr of the drive wheel 12. In this case, the higher-level controller 70 only needs to transmit the commanded rotational speed of the rotor instead of the commanded rotational speed N* of the drive wheel 12. The speed calculation unit 90 should calculate the rotational speed Nm of the rotor and input the calculated rotational speed Nm to the speed deviation calculation unit 91.

[0076] • Automated guided vehicles (AGVs) are not limited to four-wheeled vehicles; for example, they may be six-wheeled vehicles with three sets of drive wheels arranged in the width direction, two-wheeled vehicles with one set of drive wheels, or vehicles with one drive wheel. Furthermore, AGVs are not limited to those with some wheels as driven wheels (casters); all wheels may be drive wheels.

[0077] • Unmanned guided vehicles used in factories are not limited to AGVs; for example, autonomous mobile robots (AMRs) may also be used.

[0078] In this disclosure or claims, the term "processor" means one or more hardware processors configured to execute processing defined by computer program code (i.e., one or more instructions of a computer program) contained in a computer program by reading the computer program code each time. In other words, a "processor" is a hardware device that executes one or more programmed processes. Therefore, computer program code can also be said to be software that can define the processing of the processor according to its content. A "processor" can be a general-purpose or specific-purpose processor, and may be, but is not limited to, a CPU, microprocessor, GPU, and DFP (Data Flow Processor).

[0079] In this disclosure or claims, the term “memory” means one or more hardware memories that are non-transitional tangible recording media configured to record computer program code and / or data in a manner accessible from a processor. “Memory” can be implemented by memory technology such as SRAM, SDRAM, non-volatile / flash type memory, or other types of memory. The computer program code that constitutes the program is recorded in memory and executed by a processor, thereby enabling the processor to perform the various functions described above.

[0080] In this disclosure or claims, the term “circuit” refers to one or more logic circuits as hardware, configured to perform specific processing defined by a pre-designed circuit configuration. In other words (and, in contrast to “processor”), “circuit” in this disclosure or claims refers to a hardware device that performs specific processing based on a circuit configuration, rather than processing defined by software such as the computer program code described above. For example, “circuit” may include custom ICs such as ASICs (Application Specific Integrated Circuits) and FPGAs (Field Programmable Gate Arrays) designed with Hardware Description Language (HDL). That is, “circuit” in this disclosure or claims includes all hardware circuits except for the processors described above that perform processing by reading computer program code.

[0081] In this disclosure or claims, the expression "at least one of the circuit and processor" should be interpreted as disjunctive (logical OR) and not as "at least one circuit and at least one processor." Therefore, in this disclosure or claims, "at least one of the circuit and processor causes the control device to perform functions" includes cases where the circuit alone causes the control device to perform all functions. Also, "at least one of the circuit and processor causes the control device to perform functions" includes cases where the processor alone causes the control device to perform all functions. Furthermore, "at least one of the circuit and processor causes the control device to perform functions" includes cases where the circuit causes the control device to perform some functions and the processor causes the control device to perform the remaining functions. In the last example, for example, if the control device performs functions A to C, functions A and B may be implemented by the circuit, and the remaining function C may be implemented by the processor.

[0082] The following describes characteristic configurations extracted from each of the embodiments described above. [Configuration 1] A control device (80) for an electric vehicle (10) that transports an object (15), comprising: a drive wheel (12); a motor (31) for rotating the drive wheel; and an inverter (34) electrically connected to the armature winding (31a) of the motor, wherein the control device (80) comprises: a switch control unit (90-93) that performs switching control of the inverter in order to feedback control the rotational speed of the drive wheel or the rotational speed of the motor rotor to a commanded rotational speed; and a gain setting unit (94) that varies the control gain of the feedback control based on at least one of the total weight of the object and the electric vehicle and the rotational speed. [Configuration 2] The control device for an electric vehicle according to Configuration 1, wherein the gain setting unit makes the control gain larger when the total weight is large than when the total weight is small. [Configuration 3] The control device for an electric vehicle according to Configuration 2, wherein the feedback control includes proportional control in which a proportional gain is used as the control gain, and the gain setting unit increases the proportional gain when the total weight is large compared to when the total weight is small. [Configuration 4] The control device for an electric vehicle according to Configuration 2 or 3, wherein the gain setting unit performs a process to estimate the total weight, and increases the proportional gain when the estimated total weight is large compared to when the estimated total weight is small. [Configuration 5] The control device for an electric vehicle according to Configuration 4, wherein the gain setting unit estimates the total weight when the electric vehicle is accelerating or decelerating. [Configuration 6] The control device for an electric vehicle according to any one of Configurations 1 to 5, wherein the feedback control includes integral control in which an integral gain is used as the control gain, and the gain setting unit performs a process to estimate the coefficient of friction of the frictional force acting between the road surface (16) of the electric vehicle and the drive wheels, and increases the integral gain when the estimated coefficient of friction is large compared to when the estimated coefficient of friction is small. [Configuration 7] The control device for the electric vehicle according to Configuration 6, wherein the gain setting unit estimates the friction coefficient when the electric vehicle is traveling at a constant speed.[Configuration 8] The control device for an electric vehicle according to any one of Configurations 1 to 7, wherein the feedback control includes integral control using an integral gain as the control gain, and the gain setting unit performs a process to make the integral gain variable based on the rotational speed. [Configuration 9] The control device for an electric vehicle according to Configuration 8, wherein the gain setting unit performs a process to make the integral gain in the extremely low-speed driving mode of the electric vehicle greater than the integral gain in the normal mode at a driving speed higher than the driving speed of the electric vehicle in the extremely low-speed driving mode. [Configuration 10] The control device for an electric vehicle according to Configuration 9, wherein the gain setting unit sets the integral gain in the extremely low-speed driving mode to a value that is 5 times or more and 50 times or less than the integral gain in the normal mode.

[0083] This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure.

Claims

1. A control device (80) for an electric vehicle (10) that transports an object (15), comprising: a drive wheel (12); a motor (31) for rotating the drive wheel; and an inverter (34) electrically connected to the armature winding (31a) of the motor, wherein the control device (80) comprises: a switch control unit (90-93) that performs switching control of the inverter in order to feedback control the rotational speed of the drive wheel or the rotational speed of the motor rotor to a commanded rotational speed; and a gain setting unit (94) that varies the control gain of the feedback control based on at least one of the total weight of the object and the electric vehicle and the rotational speed.

2. The control device for an electric vehicle according to claim 1, wherein the gain setting unit increases the control gain when the total weight is large compared to when the total weight is small.

3. The control device for an electric vehicle according to claim 2, wherein the feedback control includes proportional control in which a proportional gain is used as the control gain, and the gain setting unit increases the proportional gain when the total weight is large compared to when the total weight is small.

4. The control device for an electric vehicle according to claim 3, wherein the gain setting unit performs a process to estimate the total weight, and increases the proportional gain when the estimated total weight is large compared to when the estimated total weight is small.

5. The control device for an electric vehicle according to claim 4, wherein the gain setting unit estimates the total weight when the electric vehicle is accelerating or decelerating.

6. The control device for an electric vehicle according to any one of claims 1 to 5, wherein the feedback control includes integral control in which an integral gain is used as the control gain, the gain setting unit performs a process to estimate the coefficient of friction of the frictional force acting between the road surface (16) of the electric vehicle and the drive wheels, and increases the integral gain to a larger value when the estimated coefficient of friction is large than when the estimated coefficient of friction is small.

7. The control device for an electric vehicle according to claim 6, wherein the gain setting unit estimates the coefficient of friction when the electric vehicle is traveling at a constant speed.

8. The control device for an electric vehicle according to any one of claims 1 to 5, wherein the feedback control includes integral control using the integral gain as the control gain, and the gain setting unit performs a process to make the integral gain variable based on the rotational speed.

9. The control device for an electric vehicle according to claim 8, wherein the gain setting unit performs a process to make the integral gain variable, by making the integral gain in the extremely low-speed driving mode of the electric vehicle greater than the integral gain in the normal mode at a driving speed higher than the driving speed of the electric vehicle in the extremely low-speed driving mode.

10. The control device for an electric vehicle according to claim 9, wherein the gain setting unit sets the integral gain in the extremely low-speed driving mode to a value that is five times or more and fifty times or less the integral gain in the normal mode.

11. An electric drive device comprising: a control device for an electric vehicle according to any one of claims 1 to 5; the motor; and the inverter.

12. A program applied to an electric vehicle (10) that transports an object (15), comprising: a drive wheel (12); a motor (31) for rotating the drive wheel; and an inverter (34) electrically connected to the armature winding (31a) of the motor, wherein the program causes a processor (81) to perform: a switch control process that performs switching control of the inverter in order to feedback control the rotational speed of the drive wheel or the rotational speed of the motor rotor to a commanded rotational speed; and a gain setting process that makes the control gain of the feedback control variable based on at least one of the total weight of the object and the electric vehicle and the rotational speed.

13. A control method for an electric vehicle (10) that transports an object (15), comprising: a drive wheel (12); a motor (31) for rotating the drive wheel; and an inverter (34) electrically connected to the armature winding (31a) of the motor, wherein the control method for an electric vehicle involves causing a processor (81) to perform: a switch control process that performs switching control of the inverter in order to feed back control the rotational speed of the drive wheel or the rotational speed of the motor rotor to a commanded rotational speed; and a gain setting process that makes the control gain of the feedback control variable based on at least one of the total weight of the object and the electric vehicle and the rotational speed.

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