Motion control device for left and right independent drive vehicles

Abstract

To provide a motion control device of a right and left independent drive vehicle which corrects motor torque difference by considering external influences and improves control accuracy of driving forces of right and left wheels.SOLUTION: A motion control device 2 calculates a wheel torque value from a difference between a reference vehicle state quantity calculated from operation information of a driver or operation indication of a higher-order driving device, and an actual vehicle state quantity calculated from information concerning a motion and a posture of the vehicle and, based thereon, controls a plurality of motors and drives right and left wheels independently. Further, the motion control device 2 calculates a momentum error from a difference between a reference momentum calculated based on a wheel rotation speed and a tire steering angle and an actual momentum calculated based on information concerning the motion and the posture of the vehicle, extracts a momentum error due to the torque difference of the motor from the calculated momentum error, calculates a wheel torque correction amount based on the momentum error due to the extracted torque difference of the motor, adds the wheel torque correction amount to the wheel torque value, and outputs wheel torque instruction to the plurality of motors.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to the configuration of a control device for controlling the motion of a vehicle, and more particularly to a motion control device for a vehicle in which left and right wheels are driven independently by motors. [Background technology]

[0002] As we move towards a carbon-neutral and autonomous driving society, the electrification of automobiles is progressing. In vehicles that use motors to drive the left and right wheels independently, controlling the driving force independently can add yaw moment, pitch moment, and roll moment to the vehicle, and by making effective use of the tire's capabilities, it is possible to improve the vehicle's maneuverability and stability.

[0003] However, if the control accuracy of the driving force of the left and right wheels is low and the intended driving force cannot be applied, this will actually worsen the vehicle's maneuverability and stability, so improving the control accuracy of the driving force of the left and right wheels is a challenge.

[0004] To address this issue, a technology such as that described in Patent Document 1 has been proposed. In Patent Document 1, an electric vehicle is equipped with two traction motors that independently drive left and right drive wheels, and the two traction motors are driven based on a command value from a torque command means. The torque output characteristics of the traction motors can vary depending on factors such as the motor's manufacturing precision, assembly accuracy, level of matching adjustment with the inverter, and aging. To address this issue, Patent Document 1 provides a torque difference determination means and a driving force difference reduction means. The torque difference determination means determines whether a difference exists between the actual driving forces TL and TR of the left and right drive wheels, even though the torque command means provides identical torque command values ​​TL* and TR* to the two traction motors based on steering torque information. The driving force difference reduction means controls the vehicle to reduce the driving force difference when the torque difference determination means determines that a driving force difference between the left and right drive wheels is greater than or equal to a set value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-158123 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the technology described in Patent Document 1, when determining whether a difference in actual driving force occurs between the left and right drive wheels from steering torque information acting on the steering device despite the same torque command value being applied, it is not possible to distinguish whether the cause of the change in steering torque information is a difference in driving force between the left and right wheel motors or an external factor such as the road gradient. As a result, it is not possible to appropriately correct the difference in driving force between the motors, and it may be difficult to improve the control accuracy of the driving force between the left and right wheels. For example, if a vehicle is traveling uphill by increasing the driving force of one of the left and right motors, the driving force of the motor that is increasing the driving force may become excessive when the vehicle finishes traveling uphill, potentially causing the vehicle to become unstable.

[0007] An object of the present invention is to provide a motion control device for a vehicle with independent left and right drive that can correct the torque difference between the motors taking into account external influences such as road gradient, thereby improving the control accuracy of the driving forces of the left and right wheels. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides a motion control device for a vehicle with left and right independent drive, which calculates a wheel torque value from the difference between a vehicle state quantity reference calculated from driver operation information or operation instructions from a higher-level driving device and an actual vehicle state quantity calculated from information on the vehicle's motion and attitude, and controls a plurality of motors based on the wheel torque value to drive left and right wheels independently, and the motion control device calculates a wheel torque value based on wheel rotation speed and tire steering angle. Estimated lateral acceleration and, longitudinal acceleration, lateral acceleration, and yaw rate of the vehicle Calculated based on Actual lateral accelerationThe momentum error is calculated from the difference between Separating a disturbance component for the vehicle from the frequency characteristics related to the momentum error The present invention is characterized in that a momentum error caused by the torque difference of the motors is extracted, a wheel torque correction amount is calculated based on the extracted momentum error caused by the torque difference of the motors, and the wheel torque correction amount is added to the wheel torque value to output a wheel torque command to the multiple motors. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a motion control device for a vehicle with independent left and right drive that can correct the torque difference between the motors by taking into account external influences such as road gradient, thereby improving the control accuracy of the drive forces of the left and right wheels. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a plan view showing a schematic configuration of a vehicle 1 equipped with a vehicle motion control device 2 according to a first embodiment of the present invention. [Figure 2] 1 is a diagram showing the connection relationship between components of a vehicle and a vehicle motion control device according to a first embodiment of the present invention. [Figure 3] 1 is a diagram showing a control block in a vehicle motion control device 2 according to a first embodiment of the present invention. [Figure 4] FIG. 10 is a diagram showing characteristics when there is a torque difference between the left and right motors. [Figure 5] 10A and 10B are diagrams showing an example of vehicle movement when there is a torque difference between the left and right motors; [Figure 6] 10 is a diagram showing lateral acceleration when there is a longitudinal acceleration command to the vehicle and a torque difference between the motors, and when there is no torque difference between the motors. FIG. [Figure 7] FIG. 10 is a diagram illustrating the relationship between frequency and lateral acceleration intensity. [Figure 8] FIG. 10 is a diagram showing the relationship between the frequency of each general behavior and the lateral acceleration intensity. [Figure 9] FIG. 10 is a diagram showing the characteristics of the lateral acceleration generated in the vehicle on the frequency axis due to the motor torque difference. [Figure 10]1 is a diagram showing the configuration of a vehicle motion control device 2 equipped with a plurality of band-pass filters. [Figure 11] FIG. 10 is a diagram showing torque magnitude and attitude change in the case of four-wheel independent drive. DETAILED DESCRIPTION OF THE INVENTION

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Like elements are designated by like reference numerals and similar descriptions will not be repeated.

[0012] The various components of the present invention do not necessarily have to be independent entities, and it is acceptable for one component to be made up of multiple members, for multiple components to be made up of one member, for one component to be part of another component, or for part of one component to overlap with part of another component.

[0013] A motion control device for a vehicle with independent left and right drive will be described using Figures 1 to 11. In this embodiment, as will be described below, a vehicle is provided with multiple independent motors on the left and right sides, and the multiple motors are controlled based on wheel torque values ​​to drive the left and right wheels independently.

[0014] FIG. 1 is a plan view showing a schematic configuration of a vehicle 1 equipped with a vehicle motion control device 2 according to a first embodiment of the present invention.

[0015] In FIG. 1, the vehicle 1 of this embodiment is equipped with a vehicle momentum sensor 3, an accelerator pedal 4, a brake pedal 5, a steering wheel 6A, a steering mechanism 6B, in-wheel motors (front left 7FL, front right 7Fr, rear left 7RL, rear right 7Rr), tires (front left 8FL, front right 8Fr, rear left 8RL, rear right 8Rr), and a controller area network 9 connecting each device.

[0016] Although other components and power wiring to each device are the same as those of a normal vehicle, they are not necessary for the explanation of this embodiment and will not be illustrated or explained. The coordinate system used in the explanation is such that the front-to-rear direction of the vehicle 1 is the x-axis (forward direction is positive), the left-to-right direction is the y-axis (left direction is positive), and the up-to-down direction is the z-axis (upward direction is positive).

[0017] The vehicle 1 is driven by generating driving force in the in-wheel motors of each wheel in response to accelerator pedal input. In this embodiment, each tire can independently generate driving and braking torque, which can be adjusted according to the driving conditions, etc.

[0018] The direction of travel of the vehicle is changed by steering the front wheels with a steering mechanism 6B in reference to the input of a steering wheel 6A. In this embodiment, a by-wire system is used in which the steering wheel and the steering mechanism are connected by electric wires.

[0019] Braking of the vehicle is done by using the brake pedal5 Input In order to deal with areas that cannot be controlled by the in-wheel motors, friction brakes are used or combined with them, but as mentioned above, they are unnecessary components for the explanation of this embodiment and will not be described here.

[0020] FIG. 2 is a diagram showing the connection relationship between the components of a vehicle and a vehicle motion control device 2 according to the first embodiment of the present invention. The vehicle motion control device 2 receives information related to the motion and attitude of the vehicle from a vehicle motion quantity sensor 3, and receives driver operation information from an accelerator pedal 4, a brake pedal 5, and a steering wheel 6A. Then, the vehicle motion control device 2 calculates the steering angle of the front wheels and the braking / driving torque of each wheel to realize a desired vehicle motion, and controls the steering mechanism 6B and each in-wheel motor (front left 7FL, front right 7Fr, rear left 7RL) to adjust the steering angle and the braking / driving torque of each wheel. 、The steering mechanism 6B outputs a torque command to the right rear wheel 7Rr. At the same time, it receives device information such as steering angle, steering force, and wheel rotation speed from the steering mechanism 6B and each in-wheel motor. The information related to the vehicle's movement and attitude includes longitudinal acceleration, lateral acceleration, roll rate, pitch rate, yaw rate, etc. In addition to the above, the information related to the vehicle's movement and attitude may also be the difference in rotation speed and rotation angle between the motors.

[0021] 3 is a diagram showing control blocks in a vehicle motion control device 2 according to a first embodiment of the present invention. Inputs to the vehicle motion control device 2 include the wheel rotation speeds and tire steering angles from the steering mechanism and each in-wheel motor as device information, longitudinal acceleration, lateral acceleration, and yaw rate from vehicle momentum sensors as information related to the vehicle motion and attitude, and accelerator position, brake position, and steering wheel position from the accelerator pedal, brake pedal, and steering wheel as driver operation information. Outputs from the vehicle motion control device 2 are wheel torque commands and tire steering angle commands.

[0022] Furthermore, the present invention is equally applicable to both manually driven vehicles and vehicles driven by automatic driving devices, and instead of driver operation information, operation instructions from a higher-level driving device such as an automatic driving device can be used as input to the vehicle's motion control device 2.

[0023] The processing in the vehicle motion control device 2 is roughly divided into two parts. The first part is a part that controls the vehicle state, and the second part is a part that calculates the amount of correction for the wheel torque value.

[0024] The first part of the vehicle state control calculates a vehicle state quantity reference using a vehicle state quantity reference input element 2C based on the driver's operation information. Also, an actual vehicle state quantity is calculated using an actual vehicle state quantity calculation element 2D based on information related to the vehicle's motion and attitude. Next, a vehicle state quantity error is calculated from the difference between the vehicle state quantity reference and the actual vehicle state quantity, and based on this error, a vehicle state controller 2G calculates the wheel torque value and tire steering angle, which are the operation quantities.

[0025] In the part that calculates the correction amount for the second wheel torque value, a momentum reference is calculated by a momentum reference input element 2A from the above-mentioned device information. Also, an actual momentum calculation element 2B calculates the actual momentum from information about the vehicle's motion and attitude. Next, a momentum error is calculated from the difference between the momentum reference and the actual momentum, and a separation means 2E extracts from this error the momentum error caused by the motor torque difference. Then, a correction amount calculation means 2F calculates a wheel torque correction amount from this extracted error. Finally, the wheel torque value calculated in the part that controls the first vehicle state is corrected by adding the wheel torque correction amount calculated in the part that calculates the correction amount for the second wheel torque value, and this is output from the motion control device 2 as a wheel torque command. Note that the tire steering angle command is the value calculated in the part that controls the first vehicle state, and is output from the motion control device 2 as a tire steering angle command without any change.

[0026] In this embodiment, the vehicle is operated by a driver who gets in the vehicle, but the present invention is not limited to this, and for example, the input to the vehicle motion control device 2 may be provided from a higher-level automatic driving control device. Also, in this embodiment, the vehicle is equipped with four in-wheel motors, but the present invention is not limited to this, and for example, the vehicle may drive only the two front wheels or only the two rear wheels, or the left and right wheels may be driven by two motors mounted on the vehicle body instead of in-wheel motors.

[0027] Specific operations according to this embodiment will be described below using the example of driving with straight-line acceleration by applying driving force only to the rear wheels. Figure 4 shows the characteristics when there is a torque difference between the left and right motors. As shown in Figure 4, there are individual differences between the left and right motors arranged on the rear wheels, and for the same wheel torque command, the torque F42 of the right motor is greater than the torque F41 of the left motor.

[0028] When the vehicle accelerates in a straight line, the driver operates the accelerator. In the vehicle motion control device 2, the vehicle state quantity reference input element 2C receives this input and calculates the reference longitudinal acceleration, which is set as the vehicle state quantity reference. Here, the vehicle state controller 2G calculates and outputs a wheel torque command so that the current longitudinal acceleration is equal to the reference longitudinal acceleration. Since the vehicle is traveling in a straight line in this state, equal values ​​are commanded for the left and right wheel torques.

[0029] FIG. 5 shows an example of vehicle motion when there is a torque difference between the left and right motors. Based on the wheel torque command output by the vehicle state controller 2G, the in-wheel motor generates torque, generating a tractive force that moves the vehicle forward. Here, the left and right in-wheel motors (left rear 7RL) 、 Because there are individual differences in the right rear (Rr), the right tractive force F53 is greater than the left tractive force F52 (F53>F52), and the vehicle motion turns left as shown in path F51. The left turn generates a positive yaw rate and positive lateral acceleration in the vehicle. Thus, even though the command from the vehicle motion control device 2 is to equalize the left and right wheel torques and generate straight-line acceleration, the difference in actual motor torque results in the vehicle turning left.

[0030] FIG. 6 is a diagram showing the lateral acceleration when there is a longitudinal acceleration command to the vehicle and a torque difference between the motors, and when there is no torque difference between the motors.

[0031] When a wheel torque value is generated by a longitudinal acceleration command F61 to the vehicle, if there is a torque difference between the left and right motors, a positive lateral acceleration F62 occurs, as shown in the operation described above. At this time, the lateral acceleration is affected not only by the torque difference between the motors but also by vehicle motion due to road noise caused by road surface irregularities, suspension operation, and various component deflections, resulting in a distorted shape as shown in the figure. On the other hand, if there is no torque difference between the left and right motors, only the effects of vehicle motion due to road noise caused by road surface irregularities, suspension operation, and various component deflections are observed, as shown in normal lateral acceleration F63.

[0032] Figure 7 shows the relationship between frequency and lateral acceleration intensity. Figure 7 shows the results of frequency analysis of lateral acceleration F62 (Figure 6) when there is a motor torque difference. Three peaks are observed, starting from the lowest frequency. The peaks correspond to behavior F71, vehicle motion F72, and road noise F73, which are caused by the motor torque difference.

[0033] Here, the frequency characteristics of each general behavior will be explained. Fig. 8 is a diagram showing the relationship between the frequency of each general behavior and the lateral acceleration intensity. In Fig. 8, the frequency characteristics are, from lowest frequency, behavior F81 caused by the torque difference of the motor, vehicle motion F82, and road noise F83. As shown in Fig. 8, behavior F81, vehicle motion F82, and road noise F83 caused by the torque difference of the motor can be identified from the difference in frequency with respect to the lateral acceleration intensity.

[0034] From the above, by filtering the lateral acceleration in the frequency domain, it is possible to extract only the component of the lateral acceleration generated in the vehicle that is caused by the torque difference between the motors. Specifically, a low-pass filter is applied to extract only the component that is caused by the torque difference between the motors.

[0035] The vehicle motion control device 2 of this embodiment uses this principle to calculate the wheel torque correction amount. That is, the momentum reference input element 2A calculates an estimated lateral acceleration based on the wheel rotation speed and tire steering angle to set it as the momentum reference, and the actual momentum calculation element 2B calculates an actual lateral acceleration based on the longitudinal acceleration, lateral acceleration, and yaw rate to set it as the actual momentum, and calculates the difference from the momentum reference (momentum error).

[0036] This difference (momentum error) is filtered by a separation means 2E using a low-pass filter to extract the momentum error caused by the motor torque difference. Because the momentum error as a difference is a lateral acceleration component, the disturbance components to the vehicle are separated using a low-pass filter due to differences in frequency characteristics, making it possible to extract only the momentum error caused by the motor torque difference. Furthermore, a correction amount calculation means 2F calculates a wheel torque correction amount from the relational expression between lateral acceleration and wheel torque difference used in this embodiment. This wheel torque correction amount is added to the wheel torque value calculated by the vehicle state controller 2G, and is output as a wheel torque command from the vehicle motion control device 2. The wheel torque command is output to each of the left and right motors.

[0037] Through the above operations, the wheel torque command is corrected by the torque difference between the motors, and the tractive force generated on the left and right sides of the vehicle is finally equalized, allowing the vehicle to properly accelerate in a straight line without turning in response to the command to accelerate in a straight line. In the case of Figure 5, the right tractive force F53 is greater than the left tractive force F52, so to make the right tractive force F53 and the left tractive force F52 equal, for example, the left wheel torque command is made 5% higher than the right wheel torque command. Alternatively, the right wheel torque command is made 5% lower than the left wheel torque command.

[0038] Furthermore, in calculating the wheel torque correction amount, the effects of road noise due to road surface irregularities and vehicle movement due to suspension operation and deflection of various parts are removed in addition to the torque difference between the motors, and only the torque difference between the left and right motors is correctly corrected, thereby preventing incorrect corrections from being made and providing a vehicle motion control device that can improve the control accuracy of the driving forces of the left and right wheels.

[0039] Furthermore, by performing more detailed frequency domain separation in the separation means 2E as shown in Fig. 9, it is possible to separate the components resulting from motor torque differences into behavior F91 resulting from permanent differences such as individual differences between motors and behavior F92 resulting from temporary differences due to temperature, etc. By configuring in this way, it is possible to provide a vehicle motion control device that can perform even more accurate corrections and improve the control accuracy of the drive forces of the left and right wheels. The configuration for achieving this is shown in Fig. 10.

[0040] FIG. 10 is a diagram showing the configuration of a vehicle motion control device 2 equipped with a plurality of band-pass filters.

[0041] The separating means 2E is equipped with n bandpass filters. The bandpass filters (1st to nth bandpass filters) are installed with different passing frequency bands, and extract the influence of each target cause from the signal input to the separating means 2E.

[0042] The correction amount calculation means 2F is configured to incorporate a plurality of integrators (first to nth integrators) corresponding to the respective band-pass filters, calculate the respective correction amounts, and then combine the calculated wheel torque correction amounts. The calculated wheel torque correction amounts are output from the lateral acceleration controller of the correction amount calculation means 2F.

[0043] As described above, the vehicle motion control device 2 of this embodiment separates the difference between the estimated value and the actual value of the vehicle motion amount by frequency, and calculates the driving torque between the motors. difference The drive torque difference between the motor and the vehicle disturbance is accurately corrected. difference Therefore, it is possible to provide a vehicle motion control device 2 that can accurately correct the above.

[0044] In this embodiment, the explanation is given for simple straight-line acceleration, but the present invention is not limited to this, and correction may be applied, for example, when accelerating in an acceleration lane on a highway, accelerating to merge onto a main road, stopping at a traffic light on a general road (the correction amount is calculated based on the behavior of braking torque), traveling while climbing a slope, etc. Also, a configuration in which the correction amount is calculated at all times is also possible.

[0045] [Modification] The case of four-wheel independent drive, in which four motors are controlled to drive four wheels, will be explained using Fig. 11. Fig. 11 is a diagram showing the relationship between torque magnitude and posture change in the case of four-wheel independent drive. As shown in Fig. 11, there is a correlation between the relationship between torque magnitude and how it affects posture change.

[0046] For example, even if the motor torque on the left side is excessively large compared to the motor torque on the right side, the change in vehicle posture will differ depending on the front or rear position of the motor where the motor torque is excessive. In Figure 11, when the front-left motor torque is excessively large compared to the front-right, rear-right, and rear-left, the vehicle's roll rate and yaw rate will show negative changes, and the pitch rate will show positive changes. When the rear-left motor torque is excessively large compared to the front-right, rear-right, and front-left, even on the same left side, the vehicle's roll rate and pitch rate will show positive changes, and the yaw rate will show negative changes.

[0047] In this embodiment, the above relationship is utilized to calculate the momentum errors for the four motors based on the attitude change (information about the vehicle's motion and attitude), and the wheel torque correction amount is calculated, thereby enabling a more accurate calculation of the wheel torque correction amount. Therefore, by configuring the motion control device 2 using this mechanism, it is possible to provide a vehicle motion control device that can further improve the accuracy of driving force control.

[0048] In this embodiment, the vehicle state quantity reference is calculated from the driver's operation information, but the vehicle state quantity reference may also be calculated from the operation instructions of a higher-level driving device, such as a so-called automatic driving device. [Explanation of symbols]

[0049] 1...vehicle, 2...motion control device, 2E...separation means, 2F...correction amount calculation means, 3...vehicle momentum sensor, 4...accelerator pedal, 5...brake pedal, 6A...steering wheel, 6B...steering mechanism, 7FL...left front in-wheel motor, 7Fr...right front in-wheel motor, 7RL...left rear in-wheel motor, 8Rr...right rear in-wheel motor, 8FL...left front tire, 8Fr...right front tire, 8RL...left rear tire, 8Rr...right rear tire, 9...controller area network

Claims

1. A motion control device for a left and right independently driven vehicle, which calculates a wheel torque value from a difference between a vehicle state quantity reference calculated from driver operation information or an operation instruction from a higher-level driving device and an actual vehicle state quantity calculated from information on the vehicle's motion and attitude, and controls a plurality of motors based on the wheel torque value to independently drive left and right wheels, a wheel torque correction amount based on the extracted momentum error caused by the torque difference between the motors; and adding the wheel torque correction amount to the wheel torque value to output wheel torque commands to the plurality of motors.

2. 2. A motion control device for a left and right independently drive vehicle according to claim 1, The motion control device for a vehicle with independent left and right drive is characterized in that the motion control device separates behavior caused by permanent differences due to individual differences in the motor and behavior caused by temporary differences due to temperature according to frequency characteristics from momentum errors caused by torque differences between the motors.

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