Vehicle control device and vehicle control method

Abstract

To efficiently ensure the vehicle's straight-line stability through torque control. [Solution] The vehicle control device 10 according to this embodiment has a controller 12 that controls in-wheel motors 22 that drive each of the multiple wheels provided on the vehicle 1. The controller 12 controls the in-wheel motors 22 by torque control and adjusts the torque distribution of each in-wheel motor 22 according to the difference in rotational speed between the front and rear wheels of the vehicle when the vehicle 1 is moving laterally.

Description

Technical Field

[0001] The present invention relates to a vehicle control device and a vehicle control method.

Background Art

[0002] Conventionally, when a vehicle such as a forklift is made to travel in a lateral movement mode, by steering the left and right wheels on the front wheel side where the forks are provided in a V-shaped pattern, even if there is a bias in the state of the front and rear loads of the vehicle, a technique for maintaining straight-ahead performance is known (see, for example, Patent Document 1).

[0003] The technique described in this Patent Document 1 is a method of forcibly running the vehicle in a state where the wheels are in a V-shaped pattern during lateral movement, that is, a state where the wheels are not facing the direction in which the vehicle is to be advanced (a state where the left and right wheels are facing different directions). For this reason, the direction of the wheels does not match the traveling direction, and the efficiency decreases.

[0004] Also, as a control method for a motor that drives a vehicle, there are rotational speed control and torque control. And when the vehicle is moving laterally, it is conceivable to use rotational speed control that enables high straight-ahead performance even if there is a bias in the state of the front and rear loads of the vehicle.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, since rotational speed control causes the vehicle to behave differently from torque control, which is often used when traveling in the normal vehicle front-rear direction, some drivers may feel a sense of discomfort.

[0007] The present invention has been made in view of the above, and aims to efficiently ensure the straight-line stability of a vehicle even when torque control is used during lateral movement. [Means for solving the problem]

[0008] The vehicle control device according to the present invention has a controller that controls motors that drive each of the multiple wheels provided on a vehicle capable of lateral movement. The controller controls the motors by torque control and adjusts the distribution of torque to each motor according to the difference in rotational speed between the front and rear wheels of the vehicle when the vehicle is moving laterally. [Effects of the Invention]

[0009] According to the present invention, even when the lateral movement of a vehicle is controlled by torque, the torque is adjusted according to the rotational speed of the wheels, thereby efficiently ensuring the straight-line stability of the vehicle. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 shows an example of the configuration of a vehicle according to this embodiment. [Figure 2] Figure 2 is a functional block diagram of the controller. [Figure 3] Figure 3 illustrates the control of an in-wheel motor. [Figure 4] Figure 4 is a functional block diagram of the calculation unit. [Figure 5] Figure 5 is a flowchart showing the processing flow of the controller. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the vehicle control device and vehicle control method disclosed in this application will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments described below.

[0012] The configuration of the vehicle according to the embodiment will be explained using Figure 1. Figure 1 is a diagram showing an example of the configuration of the vehicle according to the embodiment. The entire vehicle or a part of it may be called the vehicle control system.

[0013] As shown in Figure 1, the vehicle 1, which is capable of lateral movement in addition to normal forward and backward movement, has a vehicle control device 10. The vehicle control device 10 is, for example, a VCU (Vehicle Control Unit). The vehicle 1 also has a wheel 21LF, an in-wheel motor 22LF, a wheel 21RF, an in-wheel motor 22RF, a wheel 21LR, an in-wheel motor 22LR, a wheel 21RR, and an in-wheel motor 22RR.

[0014] The alphabetical sequences "LF," "RF," "LR," and "RR" included in the symbols correspond to the left front wheel, right front wheel, left rear wheel, and right rear wheel, respectively. For example, in-wheel motor 22RF drives the right front wheel 21RF. When the corresponding wheels are not distinguished, the alphabetical sequences may be omitted from each symbol. For example, in-wheel motors 22LF, 22RF, 22LR, and 22RR may all be referred to simply as in-wheel motor 22. The in-wheel motor 22 includes a control computer capable of communicating with the vehicle control device 10.

[0015] In Figure 1, the positive x-axis direction (the direction the arrow is pointing, to the left in the diagram) is considered the front of Vehicle 1, and the negative x-axis direction (the direction to the right in the diagram) is considered the rear. Similarly, the positive y-axis direction (the direction the arrow is pointing, upward in the diagram) is considered the right, and the negative y-axis direction (the direction the arrow is pointing downward in the diagram) is considered the left. The right and left directions are sometimes referred to as the lateral direction. The positive z-axis direction (the direction the arrow is pointing, towards the viewer in the diagram) is vertically upward, and the negative z-axis direction (towards the viewer in the diagram) is vertically downward. Furthermore, the directions of turning and rotation are explained based on the perspective of looking down at Vehicle 1 from above, i.e., vertically downward. For example, a right turn is when Vehicle 1 turns to the right.

[0016] The in-wheel motor 22 controls the wheel 21 according to the signal received from the vehicle control device 10. For example, the vehicle control device 10 can transmit signals to the in-wheel motor 22LF, the in-wheel motor 22RF, the in-wheel motor 22LR, and the in-wheel motor 22RR by CAN (Controller Area Network) communication.

[0017] In addition to the communication function, the in-wheel motor 22 includes a motor and a drive circuit of the motor. The in-wheel motor 22 controls the rotation state of the wheel 21 connected to the motor by driving and controlling the motor by the drive circuit of the motor based on the control value (for example, torque command value or target rotational speed) obtained from the received signal.

[0018] As shown in FIG. 1, the vehicle control device 10 has an interface 11, a controller 12, and a memory 13.

[0019] The interface 11 performs input and output of data between the vehicle control device 10 and other devices (for example, the in-wheel motor 22). For example, the interface 11 is a port corresponding to USB (Universal Serial Bus), Ethernet (registered trademark), CAN, etc.

[0020] The controller 12 reads and executes the program stored in the memory 13. The controller 12 is a CPU (Central Processing Unit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), a GPU (Graphics Processing Unit), a SoC (System on a Chip), etc.

[0021] The controller 12 may be a single processor. The controller 12 may have a multi-processor configuration. Also, the controller 12 may have a multi-core configuration having a plurality of cores in a single chip connected by a single socket.

[0022] By executing a program, the controller 12 realizes each processing unit shown in FIG. 2. FIG. 2 is a functional block diagram of the controller. As shown in FIG. 2, the controller 12 includes a drive control unit 121 and a calculation unit 122. By these processing units, the controller 12 controls the in-wheel motors 22 that drive each of the plurality of wheels provided on the vehicle 1.

[0023] The drive control unit 121 transmits a control value to the in-wheel motor 22. In the present embodiment, the drive control unit 121 transmits torque as the control value. The torque (torque command value) to be transmitted is determined by the vehicle control device 10 based on the accelerator opening degree or the like. The calculation unit 122 calculates the torque command value by referring to the rotational speed of each wheel acquired as feedback in addition to the accelerator opening degree.

[0024] Here, since the vehicle 1 employs the in-wheel motor 22 and can perform four-wheel independent steering, it can move straight sideways. In this case, the wheel 21 is directed in the lateral direction, that is, in a direction parallel to the y-axis.

[0025] In a vehicle with a long wheelbase, such as a truck and a bus, a turning motion may occur due to the difference in load applied to the front and rear wheels during lateral movement. For example, when trying to move straight sideways, if torque corresponding to the accelerator opening degree is output with the same front and rear distribution, the vehicle will turn about the wheel side with a large load and high load (for example, the rear wheel side in the case of a truck with a load on the rear).

[0026] In addition, since the moment becomes large when the wheelbase is long, it becomes more difficult to suppress turning.

[0027] Furthermore, by employing in-wheel motors, the rotation speed of the wheels can be precisely controlled. Therefore, during lateral movement, the control mode is set to rotation speed control, and the rotation speed command is determined based on the accelerator opening. In this case, the front and rear wheels are controlled to the same rotation speed regardless of the load, so the occurrence of turning can be suppressed. However, since this behaves differently from the torque control of an engine-powered vehicle, it may feel unnatural to the driver.

[0028] To solve these problems, the controller 12 of this embodiment performs torque control during lateral movement.

[0029] Figure 3 illustrates the control of the in-wheel motor. As shown in the lower part of Figure 3, the controller 12 suppresses turning and ensures straight-line stability by changing the torque of the front and rear wheels of the vehicle 1.

[0030] The front wheels consist of wheels equipped with wheel 21LF and wheels equipped with wheel 21RF. The rear wheels consist of wheels equipped with wheel 21LR and wheels equipped with wheel 21RR. Each wheel includes a wheel and a tire as its components.

[0031] The process by which the controller 12 calculates the torque command will be explained using Figures 4 and 5. Figure 4 is a functional block diagram of the calculation unit. Figure 5 is a flowchart showing the processing flow of the controller.

[0032] As shown in Figure 5, the controller 12 determines whether or not the vehicle 1 is moving laterally (step S101). For example, the controller 12 makes this determination based on whether or not the wheels are oriented laterally, and whether or not the internal mode of the vehicle 1 is in lateral movement mode.

[0033] If vehicle 1 is not moving laterally (step S101; No), the controller 12 terminates the torque control process.

[0034] If vehicle 1 is moving laterally (step S101; Yes), the controller 12 obtains the rotation speed of each wheel (step S102). As shown in Figure 4, the controller 12 obtains the rotation speed of the left front wheel, the rotation speed of the right front wheel, the rotation speed of the left rear wheel, and the rotation speed of the right rear wheel.

[0035] Next, the controller 12 calculates the vehicle speed based on the acquired rotational speed (step S103 in Figure 5) (step 122a in Figure 4). For example, the controller 12 calculates the vehicle speed from the acquired rotational speed and a pre-given wheel diameter.

[0036] Here, the controller 12 calculates the total torque using a torque map based on the accelerator opening and the calculated vehicle speed (step S104 in Figure 5) (step 122b in Figure 4). The torque map is data that associates the accelerator opening, vehicle speed, and total torque.

[0037] Next, the controller 12 calculates the difference between the front wheel rotation speed and the rear wheel rotation speed (step S105 in Figure 5) (steps 122e, 122f, and 122g in Figure 4).

[0038] As shown in Figure 4, the controller 12 calculates the front wheel rotation speed as the average of the left front rotation speed and the right front rotation speed. The controller 12 also calculates the rear wheel rotation speed as the average of the left rear rotation speed and the right rear rotation speed. Then, the controller 12 calculates the deviation by subtracting the front wheel rotation speed from the rear wheel rotation speed.

[0039] The controller 12 then calculates the distribution of front wheel rotation speed and rear wheel rotation speed using PI control based on the deviation (step S106 in Figure 5) (steps 122h and 122i in Figure 4). The controller 12 calculates the rear wheel distribution by subtracting the front wheel rotation speed calculated by PI control from 100%.

[0040] The controller 12 calculates the torque command value for each wheel based on the distribution and total torque (step S107 in Figure 5) (steps 122c, 122j, 122d, 122k in Figure 4). For example, the controller 12 calculates the left front wheel torque by multiplying the total torque by the front wheel distribution and then by 0.5. The coefficient of 0.5 is based on the assumption that the torque distribution between the left and right wheels is equal.

[0041] In this way, the controller 12 controls the in-wheel motors 22 by torque control and adjusts the torque distribution of each in-wheel motor 22 according to the difference in rotational speed between the front and rear wheels of the vehicle when the vehicle 1 is moving laterally. Because the controller 12 performs torque control while taking rotational speed into consideration, it can efficiently ensure the straight-line movement of the vehicle 1.

[0042] The controller 12 may perform the same control during normal driving as it does during lateral movement. That is, the controller 12 controls the in-wheel motor 22 by torque control both when the vehicle 1 is moving laterally and when the vehicle 1 is moving forward or backward.

[0043] As a result, the controller 12 can efficiently ensure the straight-line stability of the vehicle 1 not only during lateral movement but also during normal driving.

[0044] During normal driving, in the block diagram of Figure 4, the controller 12 calculates the average of the left front wheel and the left rear wheel in step 122e, the average of the right front wheel and the right rear wheel in step 122f, the left wheel distribution in step 122h, and the right wheel distribution in step 122i.

[0045] In this case, during lateral movement, the driver's ability to adjust the direction of travel may be impossible or limited to a very small range due to the constraints of the steering angle. On the other hand, during normal driving, the driver often adjusts the direction of travel themselves by operating the steering wheel.

[0046] Therefore, the controller 12 controls the vehicle so that torque distribution correction is more readily performed during lateral movement compared to normal driving, that is, so that the sensitivity of the correction is increased (so that it reacts more quickly). As a result, the controller 12 can suppress the discomfort felt by the driver during normal driving, unify the operability during normal driving and lateral movement, and ensure straight-line stability during lateral movement.

[0047] For example, when the vehicle 1 is moving laterally (lateral movement), the controller 12 increases the gain (PI gain) for adjusting the torque distribution of each in-wheel motor 22 compared to when the vehicle 1 is moving forward or backward (normal driving).

[0048] Furthermore, for example, when the vehicle 1 is moving forward or backward, the controller 12 adjusts the torque distribution of each in-wheel motor 22 if the difference in rotational speed between multiple wheels exceeds a first threshold. Then, when the vehicle 1 is moving sideways, the controller 12 adjusts the torque distribution of each in-wheel motor 22 if the difference in rotational speed between multiple wheels exceeds a second threshold that is smaller than the first threshold. In this case, the controller 12 adjusts the torque distribution only if the absolute value of the deviation calculated in step 121g is greater than or equal to the threshold.

[0049] Furthermore, the controller 12 may disable the function of adjusting torque distribution according to the steering angle during normal driving, or it may adjust the torque by taking into account the rotational speed difference (inner wheel difference) expected from the steering angle.

[0050] Furthermore, since the weight of the load affects the straight-line stability during lateral movement, the controller 12 may estimate the load using the acceleration during normal driving, pre-adjust the torque distribution in a feedforward manner using the estimated load, and then start the processing shown in Figure 5.

[0051] For example, if acceleration is low during normal driving, a large load is expected, which may result in a large load on the rear wheels. In this case, the controller 12 maintains straight-line stability by setting a large initial value for the load distribution to the rear wheels from the start of lateral movement. This improves straight-line stability during lateral movement from the initial stage.

[0052] The controller 12 may control the vehicle 1's movement by combining torque correction with automatic steering correction. Furthermore, the controller 12 may adjust the torque according to the inclination detected by the sensor.

[0053] Further effects and modifications can be readily derived by those skilled in the art. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and equivalents. [Explanation of Symbols]

[0054] 1 vehicle 10. Vehicle control system 11 Interfaces 12 controllers 13 memory 21, 21LF, 21RF, 21LR, 21RR wheels 22, 22LF, 22RF, 22LR, 22RR In-wheel motors 121 Drive control unit 122 Calculation section

Claims

1. It has a controller that controls the motors that drive each of the multiple wheels equipped on a vehicle capable of lateral movement, The aforementioned controller, The motor is controlled by torque control, When the vehicle is moving laterally, the torque distribution of each motor is adjusted according to the difference in rotational speed between the front and rear wheels of the vehicle. Vehicle control system.

2. The aforementioned controller, The motor is controlled by torque control when the vehicle is moving laterally, and when the vehicle is moving forward or backward. The vehicle control device according to claim 1.

3. The aforementioned controller, When the vehicle is moving laterally, the gain for adjusting the torque distribution of each motor is increased compared to when the vehicle is moving forward or backward. The vehicle control device according to claim 1.

4. The aforementioned controller, When the vehicle is moving forward or backward, the torque distribution of each motor is adjusted when the difference in rotational speed between the multiple wheels exceeds a first threshold. When the vehicle is moving sideways, the torque distribution of each motor is adjusted when the difference in rotational speed between the multiple wheels exceeds a second threshold that is smaller than the first threshold. The vehicle control device according to claim 1.

5. A controller that controls the motors that drive each of the multiple wheels on a vehicle capable of lateral movement, The motor is controlled by torque control, The torque distribution of each motor is adjusted according to the difference in rotational speed between the front and rear wheels of the vehicle when the vehicle is moving its multiple wheels laterally. Vehicle control method.

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