Vehicle driving control device and driving control program

Abstract

The present invention is a travel control device (10) for a vehicle (100) that travels by transmitting the power from driving motors (89, 90) to tires (111, 112, 121, 122). The device is provided with: a relaxation length calculation unit (32) that calculates a relaxation length in the front-rear direction of the tire, which is a movement distance required until the lateral force reaches a steady value when the tire has a slip angle; and a slip ratio calculation unit (33) that calculates a slip ratio indicating the degree of slip between the tire and the road surface, by dividing the length of the deformation displacement in the front-rear direction of the tire by the relaxation length calculated by the relaxation length calculation unit.

Description

Cross-reference of related applications

[0001] This application is based on Japanese Patent Application No. 2023-084890, filed on May 23, 2023, and its contents are incorporated herein by reference. [Technical Field]

[0002] This disclosure relates to a vehicle driving control device and a driving control program. [Background technology]

[0003] In vehicles that run by transmitting power from a drive motor to the tires, the wheel speed, which is the rotational speed of the tires, is detected by a wheel speed sensor, and various driving controls are performed accordingly.

[0004] For example, Patent Document 1 discloses a vehicle control device comprising a drive motor, a rotation speed detection means for detecting the rotation speed of the motor, a target rotation speed calculation means for calculating a target rotation speed of the drive wheels based on the vehicle's body speed, and a slip control means for detecting slip of the drive wheels when the wheel speed exceeds the target rotation speed of the drive wheels, and controlling the motor torque of the motor so that the wheel speed becomes an appropriate rotation speed when slip is detected, wherein the slip control means appropriately suppresses slip by controlling the motor torque through feedback control according to the difference between the motor rotation speed and the target rotation speed of the drive wheels when slip is detected. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-127281 [Overview of the project]

[0006] The conventional control methods described above assume that the wheel speed of the drive wheels can be detected by a wheel speed sensor. However, when a vehicle is traveling at an extremely low speed of about 1 km / h, pulse-generating wheel speed sensors have difficulty generating vehicle speed pulses that indicate wheel speed, making it difficult to detect the actual wheel speed. As a result, vehicle driving control based on wheel speed may not be performed correctly.

[0007] In particular, the slip ratio, which indicates the degree of slippage between the tire and the road surface, is generally calculated using the formula (vehicle speed - wheel speed) / vehicle speed. Therefore, when the vehicle speed is close to zero, the denominator in the formula becomes zero, resulting in what is known as division by zero, making it impossible to calculate the correct slip ratio.

[0008] Furthermore, if the correct slip ratio cannot be calculated, the micro-slip control, which estimates the friction coefficient μ between the tire and the road surface and controls the motor torque to prevent slippage during vehicle startup, cannot be properly executed.

[0009] Furthermore, if the wheel speed at extremely low speeds cannot be detected correctly, the control accuracy of crawl control, which controls the vehicle to travel at a constant speed at extremely low speeds on rough roads such as rocky roads, and reverse prevention control, which prevents the vehicle from moving backward during regenerative braking, which stops the vehicle using the regenerative resistance of the motor, may deteriorate.

[0010] The purpose of this disclosure is to provide a vehicle driving control device and a driving control program that can estimate the slip ratio at extremely low speeds where no vehicle speed pulses are generated.

[0011] A vehicle driving control device according to one aspect of the present disclosure is a vehicle driving control device that transmits power from a drive motor to tires for driving, A relaxation length calculation unit calculates the relaxation length in the longitudinal direction of the tire, which is the distance required to move before the lateral force reaches a steady value when the tire is subjected to a slip angle. The system includes a slip ratio calculation unit that calculates a slip ratio indicating the degree of slip between the tire and the road surface by dividing the length of the deformation displacement of the tire in the longitudinal direction by the relaxation length calculated by the relaxation length calculation unit.

[0012] Furthermore, a vehicle driving control program according to one aspect of the present disclosure is a vehicle driving control program for controlling a vehicle that drives by transmitting power from a drive motor to tires, At least one processor, The tire's longitudinal relaxation length is calculated as the distance required for the lateral force to reach a steady state when the tire is subjected to a slip angle. The slip ratio, which indicates the degree of slip between the tire and the road surface, is calculated by dividing the length of the deformation displacement of the tire in the longitudinal direction by the calculated relaxation length.

[0013] According to this disclosure, it is possible to provide a vehicle driving control device and a driving control program that can estimate the slip ratio at extremely low speeds where no vehicle speed pulse is generated. [Brief explanation of the drawing]

[0014] The purposes and other purposes, features and benefits of this disclosure will be further clarified by the following detailed description with reference to the attached drawings. Those drawings are: [Figure 1] Figure 1 is a block diagram showing the schematic configuration of a vehicle according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a block diagram illustrating the configuration of the travel control device 10 shown in Figure 1. [Figure 3] Figure 3 is a block diagram illustrating the detailed configuration of the wheel speed estimation unit 20 shown in Figure 2, and Figure 1 is a block diagram illustrating the detailed configuration of the wheel speed estimation unit 20 shown in Figure 2. [Figure 4] Figure 4 shows the calculation formula used in the wheel speed estimation unit 20 to calculate the wheel speed. [Figure 5] Figure 5 is a flowchart illustrating the overall operation of the wheel speed estimation unit 20. [Figure 6] Figure 6 shows the calculation formula for the tire rotation angle correction value θrevise in the tire rotation angle correction value calculation unit 22. [Figure 7] Figure 7 shows the calculation formula used to calculate the backlash angle θbacklash in the tire rotation angle correction value calculation unit 22. [Figure 8] Figure 8 shows the determination formula for the backlash passing flag FBL. [Figure 9] Figure 9 is a block diagram showing the detailed configuration of the slip ratio calculation unit 30 shown in Figure 2. [Figure 10] Figure 10 is a diagram illustrating the formulas used in the slip ratio calculation unit 30 to calculate the slip ratio λ and relaxation length ε. [Figure 11] Figure 11 shows an example of a case where the relaxation length ε is set according to the estimated μ-peak value. [Figure 12] Figure 12 is a block diagram showing the detailed configuration of the μ-peak estimation unit 40 shown in Figure 2. [Figure 13] Figure 13 is a diagram illustrating the specific calculation method used when calculating the friction coefficient μ in the μ calculation unit 41. [Figure 14] Figure 14 is a diagram illustrating the specific calculation method used to estimate the slope ξ in the μ-S slope estimation unit 42. [Figure 15] Figure 15 shows the μ-S curves for dry roads (asphalt), compacted snow roads, and icy roads. [Figure 16] Figure 16 shows an example of a map used by the μ-peak value calculation unit 43 to estimate the μ-peak value from the slope ξ. [Figure 17] Figure 17 is a block diagram showing the detailed configuration of the micro-slip control unit 50 shown in Figure 2. [Figure 18] Figure 18 is a flowchart illustrating the operation of the micro-slip control in the micro-slip control unit 50. [Figure 19]Figure 19 shows the changes in wheel speed, slip ratio λ, μ peak value, and MG required torque when the road surface is an ice sheet. [Figure 20] Figure 20 shows the changes in wheel speed, slip ratio λ, μ peak value, and MG required torque when the road surface is dry. [Figure 21] Figure 21 is a block diagram showing the detailed configuration of the crawl control unit 60 shown in Figure 2. [Figure 22] Figure 22 is a flowchart illustrating the operation of crawl control in the crawl control unit 60. [Figure 23] Figure 23 is a flowchart illustrating the operation of the reverse prevention control in the reverse prevention control unit 72. [Modes for carrying out the invention]

[0015] A vehicle control device according to one embodiment of this disclosure will be described below with reference to the attached drawings.

[0016] A schematic configuration of a vehicle 100 according to one embodiment of the present disclosure is shown in the block diagram of Figure 1. The control device 10 of the vehicle according to one embodiment of the present disclosure is mounted on the vehicle 100 and is configured as a device for controlling the operation of the vehicle 100.

[0017] The vehicle 100 is equipped with a driving control device 10, four tires 111, 112, 121, 122, wheel speed sensors 81, 82, 83, 84, reduction gears 85, 86, drive shafts 87, 88, motors 89, 90 as drive sources, resolvers 91, 92, brake hydraulic pressure sensor 93, longitudinal acceleration sensor 94, lateral acceleration sensor 95, inverters 96, 97, current sensors 98, 99, battery 110, and brake ECU 120.

[0018] Vehicle 100 is designed to move by transmitting power from drive motors 89 and 90 to tires 111, 112, 121, and 122.

[0019] Motors 89 and 90 generate driving force at rotational speeds controlled by inverters 96 and 97, respectively. The driving force generated by motors 89 and 90 is then transmitted to the four tires 111, 112, 121, and 122 via reduction gears 85 and 86 and drive shafts 87 and 88, respectively. Motors 89 and 90 also function as generators, regenerating braking energy generated when braking the vehicle 100 using regenerative braking, converting it into electrical energy, and charging the battery 110.

[0020] In this way, motors 89 and 90 are configured to function as both electric motors and generators, and are called motor-generators (MG).

[0021] In this embodiment, the vehicle 100 is described as a four-wheel drive vehicle equipped with two motors 89 and 90, which drives the four wheels: the front wheels 111 and 112 and the rear wheels 121 and 122. However, this disclosure is not limited to this case, and can be similarly applied when only the front wheels 111 and 112 are driven, or when only the rear wheels 121 and 122 are driven.

[0022] Furthermore, although this embodiment describes the application of the disclosure to an electric vehicle in which the drive source is only motors 89 and 90, the disclosure is also applicable to hybrid vehicles equipped with a gasoline engine and a motor.

[0023] Wheel speed sensors 81, 82, 83, and 84 detect the wheel speed, which is the rotational speed of tires 111, 112, 121, and 122, respectively, and output it as a vehicle speed pulse to the driving control device 10.

[0024] The brake hydraulic pressure sensor 93 detects the brake hydraulic pressure generated when the vehicle 100 is braked and outputs brake torque information to the driving control device 10. The brake ECU 120 controls the brakes when braking the vehicle 100.

[0025] The longitudinal acceleration sensor 94 measures the longitudinal acceleration G of the vehicle 100. X This is a G sensor that detects and outputs to the driving control device 10. The lateral acceleration sensor 95 also detects the lateral acceleration G of the vehicle 100. Y This is a G-sensor that detects and outputs to the driving control device 10.

[0026] The resolvers 91 and 92 are configured to rotate together with the rotation of the motors 89 and 90, and the motor rotation speed ω of the motors 89 and 90 M It functions as a rotational speed detection unit that detects [something].

[0027] Furthermore, inverters 96 and 97 are equipped with current sensors 98 and 99, respectively. These current sensors 98 and 99 detect the motor current flowing through motors 89 and 90, respectively, and output the motor current value information to the travel control device 10.

[0028] The driving control device 10 controls the driving of the vehicle 100 based on information input from various sensors as described above, and the MG required torque T is the torque that the motors 89 and 90 should generate. MG The information is output to inverters 96 and 97. Inverters 96 and 97 receive the MG request torque T from the travel control device 10. MG Based on this, the motors 89 and 90 are driven using power supplied from the battery 110.

[0029] Next, the configuration of the travel control device 10 shown in Figure 1 will be explained with reference to the block diagram in Figure 2.

[0030] As shown in Figure 2, the driving control device 10 includes a motor torque calculation unit 11, a vehicle speed calculation unit 12, a wheel speed estimation unit 20, a slip ratio calculation unit 30, a μ peak estimation unit 40, a minute slip control unit 50, a crawl control unit 60, a driver-requested torque generation unit 71, and a reverse movement prevention control unit 72.

[0031] Note that the travel control device 10 also has functions other than those shown in FIG. 2, but those other than the functions related to the present embodiment are omitted in FIG. 2.

[0032] The motor torque calculation unit 11 detects the motor torque generated in the motors 89 and 90 based on the motor current values detected by the current sensors 98 and 99.

[0033] The vehicle body speed calculation unit 12 calculates the vehicle body speed of the vehicle 100 by integrating the longitudinal acceleration G, which is the acceleration in the longitudinal direction of the vehicle 100. X

[0034] The wheel speed estimation unit 20 estimates the wheel speed ω, which is the rotational speed of the tires 111, 112, 121, and 122, based on the motor rotational speed ω detected by the resolver 91 and 92, which is a rotational speed detection unit, and the motor torque T calculated by the motor torque calculation unit 11 when the vehicle 100 is at an extremely low speed. M M tire

[0035] More specifically, the wheel speed estimation unit 20 estimates the wheel speed ω using the transmission characteristics when the driving force of the motors 89 and 90 is transmitted in the connecting portion connecting the motors 89 and 90 and the tires 111, 112, 121, and 122, in addition to the motor rotational speed ω and the motor torque T. M M tire

[0036] Note that the wheel speed estimation unit 20 actually calculates not the wheel speeds of the respective tires 111, 112, 121, and 122, but the average wheel speed of the front wheels and the average wheel speed of the rear wheels. Specifically, the wheel speed estimation unit 20 calculates the average of the wheel speed of the tire 111 and the wheel speed of the tire 112 as the average wheel speed of the front wheels, and calculates the average of the wheel speed of the tire 121 and the wheel speed of the tire 122 as the average wheel speed of the rear wheels.

[0037] Here, the connecting section consists of reduction gears 85 and 86 that reduce the rotational speed generated in the motors 89 and 90, and drive shafts 87 and 88 that transmit the rotation of the reduction gears 85 and 86 to the tires 111, 112, 121, and 122.

[0038] Furthermore, the reduction gears 85 and 86 also function as differential gears (differential devices) that absorb the difference in rotational speed between the left and right tires when the vehicle 100 turns on curves, etc.

[0039] In the driving control device 10, when the vehicle 100 is traveling at a normal speed, the wheel speed of each of the tires 111, 112, 121, and 122 can be detected by vehicle speed pulses from the wheel speed sensors 81 to 84. However, at extremely low speeds of 1 km / h or less, it becomes difficult for the wheel speed sensors 81 to 84 to generate vehicle speed pulses. Therefore, in the driving control device 10 of this embodiment, when the vehicle 100 is traveling at an extremely low speed such that vehicle speed pulses are not generated by the wheel speed sensors 81 to 84, the wheel speed ω estimated by the wheel speed estimation unit 20 is used. tire This will be used to calculate the slip ratio λ, perform reverse movement prevention control, crawl control, etc.

[0040] The slip ratio calculation unit 30 calculates the wheel speed ω estimated by the wheel speed estimation unit 20. tire The slip ratio λ, which indicates the degree of slip between tires 111, 112, 121, and 122 and the road surface, is calculated using this method.

[0041] The μ (friction coefficient) peak estimation unit 40 estimates the brake torque and motor torque T. M Furthermore, the slip ratio λ calculated by the slip ratio calculation unit 30 is used to estimate the μ peak value, which is the peak value of the friction coefficient μ between the tires 111, 112, 121, and 122 and the road surface.

[0042] The micro-slip control unit 50 uses the slip ratio λ calculated by the slip ratio calculation unit 30 and the μ peak value estimated by the μ peak estimation unit 40 to control the required torque for motors 89 and 90 in order to suppress the slip that occurs between tires 111, 112, 121, and 122 and the road surface. If such micro-slip control is to be properly performed even immediately after the vehicle starts moving, the wheel speed ω at extremely low speeds will be tire It is necessary to calculate the slip ratio λ by calculating the following.

[0043] The crawl control unit 60 controls the vehicle 100 to travel at a constant low speed. Here, crawl control is a control technique used when the vehicle is traveling off-road, such as on a rocky road, and the driver's body is shaking, making it difficult to perform delicate accelerator and brake operations. When crawl control is selected by operating a switch inside the vehicle, the vehicle is controlled to maintain a constant, extremely low speed without requiring accelerator or brake operation. And in order to perform such crawl control, the wheel speed ω at extremely low speeds is tire An estimation is required.

[0044] The driver-requested torque generation unit 71 generates and outputs driver-requested torque to the motors 89 and 90 based on the accelerator opening angle of the accelerator operation by the driver.

[0045] The reverse movement prevention control unit 72 performs reverse movement prevention control to prevent the vehicle 100 from moving backward immediately after stopping during regenerative braking, which stops the vehicle 100 using the regenerative resistance of the motors 89 and 90.

[0046] The minute slip control unit 50 receives the driver-requested torque from the driver-requested torque generation unit 71 and then generates the requested torque T mg1 The crawl control unit 60 outputs the requested torque T from the minute slip control unit 50. mg1 Received the requested torque T mg2The reverse prevention control unit 72 outputs the requested torque T from the crawl control unit 60. mg2 Upon receiving the final MT request torque T MG The output is then sent to inverters 96 and 97.

[0047] Next, the detailed configuration of the wheel speed estimation unit 20 shown in Figure 2 will be explained with reference to the block diagram in Figure 3.

[0048] The wheel speed estimation unit 20 uses the motor rotation speed ω detected by the rotation speed detection unit resolvers 91 and 92. M Using this, the wheel speed ω is the rotational speed of tires 111, 112, 121, and 122. tire We estimate this.

[0049] Specifically, the wheel speed estimation unit 20 determines the motor rotation speed ω M The motor rotation angle θ is calculated based on M Therefore, the tire rotation angle correction value θ is calculated by summing the angular component generated by the twisting of the drive shafts 87 and 88, the angular component due to the motor's inertia, and the angular component based on the backlash in the reduction gears 85 and 86. revise By subtracting this as a correction value, the tire rotation angle θ tire The calculated tire rotation angle θ tire By differentiating the wheel speed ω tire We estimate this.

[0050] To perform the above processing, the wheel speed estimation unit 20 is composed of a motor rotation angle calculation unit 21, a tire rotation angle correction value calculation unit 22, a subtractor 23, and a differential calculation unit 24, as shown in Figure 3. The calculation formula used by the wheel speed estimation unit 20 to calculate the wheel speed is shown in Figure 4.

[0051] As shown in Figure 1, the driving force is transmitted between the motors 89 and 90 and the tires 111, 112, 121, and 122 via connecting parts such as the reduction gears 85 and 86 and the drive shafts 87 and 88. Therefore, in order to accurately predict the wheel speed, which is the rotational speed of the tires 111, 112, 121, and 122, from the rotational speed of the motors 89 and 90, it is necessary to correct for the torsional component of the drive shafts 87 and 88, the inertia component of the motors 89 and 90, and the backlash component of the reduction gears 85 and 86.

[0052] Next, the overall operation of the wheel speed estimation unit 20 will be explained with reference to the flowchart in Figure 5.

[0053] In the wheel speed estimation unit 20, first, the motor rotation angle calculation unit 21 calculates the motor rotation speed ω as shown in equation (1) in Figure 4. M The rotation angle θ of the motor is obtained by integrating it. M Calculate (Step S101).

[0054] Next, the tire rotation angle correction value calculation unit 22 calculates the motor rotation speed ω M and the motor torque T calculated by the motor torque calculation unit 11 M Using the tire rotation angle correction value θ, revise Calculate the tire rotation angle correction value θ (step S102). revise Details on how to calculate this will be explained later.

[0055] Then, as shown in equation (2) in Figure 4, the subtractor 23 calculates the motor rotation angle θ calculated by the motor rotation angle calculation unit 21. M From there, the tire rotation angle correction value θ calculated by the tire rotation angle correction value calculation unit 22 revise By subtracting this, the tire rotation angle θ tire Calculate (Step S103).

[0056] Finally, the differential calculation unit 24 calculates the tire rotation angle θ as shown in equation (3) in Figure 4. tire By differentiating the wheel speed ω tire Calculate (Step S104).

[0057] Furthermore, the tire rotation angle correction value calculation unit 22 calculates the motor torque T M When the polarity reverses, the backlash passing flag F indicates that there is a period during which the driving force from motors 89 and 90 is not being transmitted to drive shafts 87 and 88 due to backlash in reduction gears 85 and 86. BL Outputs.

[0058] Here, backlash refers to the gap or play between gears, or the dead zone between forward and reverse rotation. Since reduction gears 85 and 86 are composed of multiple gears, backlash exists in reduction gears 85 and 86, and the motor torque T M Even if the polarity reverses, the driving force will not be transmitted in the opposite direction until it passes through this backlash.

[0059] Next, the tire rotation angle correction value θ in the tire rotation angle correction value calculation unit 22. revise The details of the calculation method will be explained by referring to the formulas in Figures 6 to 8.

[0060] As described above, the tire rotation angle correction value calculation unit 22 calculates the tire rotation angle correction value θ by adding together the drive shaft twist angle, which is the angular component generated by the twisting of the drive shafts 87 and 88, the inertia equivalent angle, which is the angular component due to the motor's inertia, and the backlash angle, which is the angular component based on the backlash in the reduction gears 85 and 86, as shown in equation (4) in Figure 6. revise Calculate.

[0061] Here, the drive shaft twist angle is given by the motor torque T, as shown in equation (5) in Figure 6. M The spring constant K indicates the rigidity of drive shafts 87 and 88. ds It is calculated by dividing by [the specified factor].

[0062] Furthermore, the inertia equivalent angle is calculated based on equation (6) in Figure 6. Here, I MThis represents the inertia of motors 89 and 90. In other words, the equivalent inertia angle is calculated from the rotational acceleration of motors 89 and 90.

[0063] Then, the backlash angle is θ backlash Expressed as, the tire rotation angle correction value θ revise This can be expressed as shown in equation (7) in Figure 6.

[0064] Then, in the wheel speed estimation unit 20, the tire rotation angle correction value calculation unit 22 uses a second-order transfer function that represents the torsional resonance of the drive shafts 87 and 88 to calculate the backlash angle θ, which is the angular component based on the backlash in the reduction gears 85 and 86. backlash Calculate.

[0065] Specifically, the tire rotation angle correction value calculation unit 22 calculates the backlash angle θ using the calculation formula shown in equation (8) in Figure 7. backlash Calculate.

[0066] Here, the LPF is a second-order lag transfer function that represents the resonance of drive shafts 87 and 88, and is expressed by equation (9) in Figure 7. In this equation, s is the Laplace operator, and ω ds This is the resonant angular frequency of drive shafts 87 and 88. Note that ω ds The inertia of motors 89 and 90 is I M And the spring constant K of drive shafts 87 and 88 ds Therefore, it is calculated using the formula shown in equation (10) in Figure 7.

[0067] Furthermore, θ in equation (8) is expressed by equation (11) in Figure 7. Here, θa is the maximum value of the backlash angle of the reduction gears 85 and 86, and is set by the measured value or the design value. Also, the backlash angle θ backlash(old) The backlash angle θ is backlash This is the previous value.

[0068] Furthermore, the tire rotation angle correction value calculation unit 22 determines the backlash passing flag F using the determination formula shown in equation (12) in Figure 8. BLIt determines whether it is on or off. Here, the backlash passing flag F BL If it is 1 (on), it indicates that backlash is being passed, and the backlash passing flag F BL A value of 0 (off) indicates that the backlash has passed.

[0069] As described above, in the driving control device 10 of this embodiment, the wheel speed is estimated in the wheel speed estimation unit 20 by the calculation method described above, so the wheel speed ω at extremely low speeds when no vehicle speed pulse is generated in the wheel speed sensors 81-84 tire It becomes possible to estimate this.

[0070] Next, the detailed configuration of the slip ratio calculation unit 30 shown in Figure 2 will be explained with reference to the block diagram in Figure 9.

[0071] As shown in Figure 9, the slip ratio calculation unit 30 consists of a vehicle speed calculation unit 31, a relaxation length calculation unit 32, and a slip ratio calculation unit 33.

[0072] The vehicle speed calculation unit 31 calculates the wheel speed ω estimated by the wheel speed estimation unit 20. tire The vehicle speed V is the speed of vehicle 100, derived from the radii of tires 111, 112, 121, and 122. w The following is calculated: Note that this vehicle speed V w This is the speed of vehicle 100 based on the circumferential speeds of tires 111, 112, 121, and 122.

[0073] The relaxation length calculation unit 32 calculates the longitudinal relaxation length ε of tires 111, 112, 121, and 122, which is the distance required for the lateral force to reach a steady value when a slip angle is applied to the tires 111, 112, 121, and 122.

[0074] The relaxation length ε is set according to the μ peak value, which is the peak value of the friction coefficient between the tires 111, 112, 121, and 122 and the road surface. Therefore, the relaxation length calculation unit 32 determines the relaxation length ε based on the μ peak value estimated by the μ peak estimation unit 40. Details of this method for determining the relaxation length ε will be described later.

[0075] The slip ratio calculation unit 33 calculates a slip ratio λ, which indicates the degree of slip between the tires 111, 112, 121, and 122 and the road surface, by dividing the length of the longitudinal deformation displacement of the tires 111, 112, 121, and 122 by the relaxation length ε calculated by the relaxation length calculation unit 32.

[0076] The slip ratio calculation unit 33 calculates the vehicle speed V based on the wheel speed estimated by the wheel speed estimation unit 20. W Then, using the vehicle speed V calculated by the vehicle speed calculation unit 12, the length of the longitudinal deformation displacement of the tires 111, 112, 121, and 122 is calculated.

[0077] Here, during the movement of vehicle 100, it takes time for the deformation of tires 111, 112, 121, and 122 to be transmitted from the front to the back. Therefore, the dynamic relationship is expressed by equation (13) in Figure 10. Here, λ is the slip ratio of tires 111, 112, 121, and 122, and λ old This is its previous value. ε is the longitudinal relaxation length of the tire as described above. The derivative of the slip ratio λ is expressed by equation (14) in Figure 10.

[0078] Then, from equations (13) and (14), the slip ratio λ is expressed as shown in equation (15) in Figure 10.

[0079] The relaxation length ε is expressed by equation (16) in Figure 10. Here, K is the driving stiffness of the tire, and K x This refers to the front-to-rear stiffness of the tire.

[0080] Here, the tire's driving stiffness K changes according to the μ-peak value between the tire and the road surface, so a relaxation length ε is set according to the estimated μ-peak value. An example of setting the relaxation length ε according to the μ-peak value in this way is shown in Figure 11.

[0081] In Figure 11, the relaxation length ε is set to 0.1 [m] when the μ peak value is 0.1 (equivalent to an ice-covered road), 0.3 [m] when the μ peak value is 0.4 (equivalent to a compacted snow road), and 0.5 [m] when the μ peak value is 1.0 (equivalent to a dry road).

[0082] By calculating the slip ratio λ at extremely low speeds using this method, the accuracy of estimating the slip ratio λ at the initial stage of vehicle 100's acceleration on dry roads is improved. Furthermore, on low-μ road surfaces such as icy or compacted snow, it becomes easier to accurately and continuously grasp the slip state between the tires and the road surface.

[0083] The μ-peak value between the tire and the road surface is estimated by the μ-peak estimation unit 40 using the method described below.

[0084] Next, the detailed configuration of the μ-peak estimation unit 40 shown in Figure 2 will be explained with reference to the block diagram in Figure 12.

[0085] As shown in Figure 12, the μ peak estimation unit 40 consists of a μ (friction coefficient) calculation unit 41, a μ-S slope estimation unit 42, and a μ (friction coefficient) peak value calculation unit 43.

[0086] The μ calculation unit 41 calculates the motor torque T calculated by the motor torque calculation unit 11. M Then, the friction coefficient μ between the tires 111, 112, 121, and 122 and the road surface is calculated using the brake torque when braking the vehicle 100 and the vehicle speed V calculated by the vehicle speed calculation unit 12.

[0087] The μ-S slope estimation unit 42 estimates the slope ξ when the relationship between the slip ratio λ calculated by the slip ratio calculation unit 30 and the friction coefficient μ calculated by the μ calculation unit 41 is expressed as a linear function.

[0088] The μ-peak value calculation unit 43 calculates the μ-peak value, which is the peak value of the friction coefficient μ between the tires 111, 112, 121, and 122 and the road surface, from the slope ξ estimated by the μ-S slope estimation unit 42.

[0089] Here, the specific calculation method for calculating the friction coefficient μ in the μ calculation unit 41 will be explained with reference to Figure 13.

[0090] The coefficient of friction μ is given by equation (17) in Figure 13, where F is the horizontal load on the tire. x The vertical load F of the tire z It is calculated by dividing by the horizontal load F of the tire. x This is expressed by equation (18) in Figure 13. Here, T M This is the motor torque converted to the tire axle, and T BRK R is the tire axle equivalent value of the brake torque, R is the tire radius, and I pt α is the inertia of the drivetrain, and α is the acceleration of the drivetrain. Also, A, B, and C are the driving resistance (F) when the vehicle travels at a constant speed on a level paved road, respectively. roadload This is the load-load coefficient used to calculate the vehicle speed. V is the vehicle speed calculated by the vehicle speed calculation unit 12.

[0091] Also, the vertical load F of the tire Z This is expressed by equation (19) in Figure 13. Here, m is the weight of the vehicle and g is the acceleration due to gravity. Also, L r is the distance from the center of gravity to the rear axle, L is the wheelbase length, and h cg This is the height of the center of gravity. Also, G x This represents the acceleration reported for vehicle 100 in the forward and backward directions.

[0092] Next, the specific calculation method for estimating the slope ξ in the μ-S slope estimation unit 42 will be explained with reference to Figure 14.

[0093] The μ-S slope estimation unit 42 estimates the slope ξ in the μ-S curve using a successive least squares estimation method with a forgetting factor. Specifically, the μ-S slope estimation unit 42 estimates the slope ξ using the equation shown in Figure 14. Here, φ is the forgetting factor, and in Figure 14, a value of 0.75 is used. Also, λ is the slip ratio calculated in the slip ratio calculation unit 30, and μ is the friction coefficient calculated in the μ calculation unit 41.

[0094] Next, the specific estimation method used in the μ-peak value calculation unit 43 to estimate the μ-peak value from the estimated slope ξ will be explained with reference to Figures 15 and 16.

[0095] Figure 15 shows the μ-S curves for dry roads (asphalt), compacted snow roads, and ice roads. The μ-peak value calculation unit 43 estimates the μ-peak value based on the slope near the zero point of these μ-S curves. The μ-peak value calculation unit 43 estimates the μ-peak value using a map that estimates the μ-peak value from the slope ξ as shown in Figure 16.

[0096] In other words, the μ-peak value calculation unit 43 estimates that the μ-peak value is 0.1 based on the map shown in Figure 16 if the slope ξ estimated by the μ-S slope estimation unit 42 is 10, and estimates that the μ-peak value is 0.3 if the estimated slope ξ is 15.

[0097] Next, the detailed configuration of the micro-slip control unit 50 shown in Figure 2 will be explained with reference to the block diagram in Figure 17.

[0098] As shown in Figure 17, the minute slip control unit 50 consists of a slip determination unit 51, a slip control torque calculation unit 52, and a switching unit 53.

[0099] The slip determination unit 51 determines whether or not the tires 111, 112, 121, and 122 are slipping based on the slip ratio λ calculated by the slip ratio calculation unit 30, and determines the start timing of the minute slip control. Specifically, the slip determination unit 51 determines that slip is occurring when the slip ratio λ calculated by the slip ratio calculation unit 30 exceeds a preset threshold, for example, 3%, and sets the minute slip control start flag F start Turn it on.

[0100] The slip control torque calculation unit 52 calculates a slip control torque that limits the driver-requested torque according to the μ-peak value estimated by the μ-peak estimation unit 40. Specifically, when the μ-peak value is 0.5 or less, the slip control torque calculation unit 52 calculates a slip control torque that limits the driver-requested torque according to the μ-peak value.

[0101] The switching unit 53 is the minute slip control start flag F start If it is off, the driver-requested torque from the driver-requested torque generation unit 71 will be used as is, the requested torque T mg1 It outputs as follows. Also, the switching unit 53 outputs the minute slip control start flag F start When this is ON, the smaller of the slip control torque calculated by the slip control torque calculation unit 52 and the driver-requested torque is used to determine the requested torque T. mg1 Output as follows.

[0102] Next, the operation of the micro-slip control unit 50 described above will be explained with reference to the flowchart in Figure 18.

[0103] First, in the micro-slip control unit 50, the slip control torque calculation unit 52 determines whether the μ-peak value estimated by the μ-peak estimation unit 40 exceeds 0.5 (step S201).

[0104] Then, when the slip control torque calculation unit 52 determines that the μ peak value is 0.5 or less, it limits the driver demand torque to a torque corresponding to the μ peak value and sets it as the slip control torque (step S202).

[0105] Next, the slip determination unit 51 determines whether the slip ratio λ calculated by the slip ratio calculation unit 30 exceeds the threshold value of 3% (step S203).

[0106] When the slip ratio λ exceeds the threshold value of 3%, the slip determination unit 51 turns on the micro slip control start flag F start As a result, the switching unit 53 outputs the smaller value between the slip control torque and the driver demand torque as the demand torque T mg1 (step S204).

[0107] When the slip ratio λ is 3% or less, which is the threshold value, the slip determination unit 51 turns off the micro slip control start flag F start As a result, the switching unit 53 outputs the driver demand torque as it is as the demand torque T mg1 (step S205).

[0108] Changes in the MG demand torque when the above-described micro slip control is performed are shown in FIGS. 19 and 20 for the case of an icy road surface and a dry road surface, respectively.

[0109] FIG. 19 is a diagram showing changes in wheel speed, slip ratio λ, μ peak value, and MG demand torque when the road surface is an icy road surface.

[0110] In FIG. 19, the vehicle 100 starts at time T1. Then, since the estimated μ peak value at time T2 is lower than 0.5, the MG demand torque is also limited according to the μ peak value. Then, since the slip ratio λ exceeds the threshold value of 3% at time T3, the micro slip control is started and the smaller value between the driver demand torque and the slip control torque is selected and output.

[0111] Figure 20 shows the changes in wheel speed, slip ratio λ, μ peak value, and MG required torque when the road surface is dry.

[0112] In Figure 20, vehicle 100 starts moving at time T1. However, since the μ peak value does not fall below the threshold and the slip ratio λ does not exceed the threshold, torque limiting is not performed and the driver-requested torque is output as the MG-requested torque.

[0113] Next, the detailed configuration of the crawl control unit 60 shown in Figure 2 will be explained with reference to the block diagram in Figure 21.

[0114] The crawl control unit 60 controls the motor torque T M When the polarity reverses, if the difference between the rotation angles of motors 89 and 90 and the rotation angles of tires 111, 112, 121, and 122 is less than the maximum value of the backlash angle of reduction gears 85 and 86, the wheel speed ω tire Crawl control is performed by reducing the feedback gain (FB gain) in feedback control (FB control), which controls the rotation of motors 89 and 90 by changing the required torque output to motors 89 and 90 based on this.

[0115] As shown in Figure 21, the crawl control unit 60 consists of a backlash passage processing unit 61, a rotation speed FB control unit 62, and a switching unit 63.

[0116] During normal operation when crawl control is not being performed, the switching unit 63 receives the requested torque T from the minute slip control unit 50. mg1 The required torque T mg2 The reverse movement prevention control unit 72 outputs the following. Then, when crawl control is selected by user operation, the switching unit 63 receives the requested torque T from the minute slip control unit 50. mg1 Instead, the crawl request torque generated in the rotation speed FB control unit 62 is the requested torque T mg2 This is output to the reverse-prevention control unit 72.

[0117] The rotational speed FB control unit 62 performs feedback control based on the wheel speed ω estimated by the wheel speed estimation unit 20, thereby generating a crawl request torque for the vehicle 100 to perform a crawl operation and outputting the torque to the switching unit 63. tire When the backlash passage processing unit 61 determines that the backlash passage flag F from the wheel speed estimation unit 20 is on, it performs control to reduce the FB gains such as the P gain (proportional gain) and D gain (differential gain) in the rotational speed FB control unit 62.

[0118] The backlash passage processing unit 61 is based on the backlash passage flag F from the wheel speed estimation unit 20 BL When it is on, control is performed to reduce the FB gains such as the P gain (proportional gain) and D gain (differential gain) in the rotational speed FB control unit 62.

[0119] Next, the operation of the crawl control in the crawl control unit 60 will be described with reference to the flowchart of FIG. 22.

[0120] When the crawl control is being performed, the backlash passage processing unit 61 determines whether the backlash passage flag F from the wheel speed estimation unit 20 BL is on (step S301).

[0121] Then, when the backlash passage flag F in the backlash passage processing unit 61 BL is on, control is performed to reduce the FB gain in the rotational speed FB control unit 62 (step S302).

[0122] Then, the rotational speed FB control unit 62 performs feedback control based on the estimated wheel speed ω tire to generate a crawl request torque for the vehicle 100 to perform a crawl operation. The generated crawl request torque is output from the switching unit 63 as the request torque T mg2 to the reverse rotation prevention control unit 72 (step S303).

[0123] By performing the above-described control, during the crawl control, the motor torque T MEven when the polarity reverses, the FB gain is weakened while passing through the backlash, which suppresses the occurrence of hunting, a phenomenon in which the drive system vibrates.

[0124] Next, the operation of the reverse prevention control in the reverse prevention control unit 72 will be explained with reference to the flowchart in Figure 23.

[0125] The reverse movement prevention control unit 72 determines the wheel speed ω estimated by the wheel speed estimation unit 20 while the vehicle 100 is moving forward or backward. tire If the value becomes zero or less, the MG required torque T will be output to motors 89 and 90. MG By setting this to zero, the reverse movement of vehicle 100 is prevented.

[0126] Furthermore, the reverse-prevention control unit 72 controls the motor torque T M When the polarity reverses, if the difference between the rotation angles of motors 89 and 90 and the rotation angles of tires 111, 112, 121, and 122 is less than the maximum value of the backlash angle of reduction gears 85 and 86, the MG required torque T output to motors 89 and 90 will be reduced. MG By setting this to zero, the reverse movement of vehicle 100 is prevented.

[0127] Next, the operation of the reverse prevention control in the reverse prevention control unit 72 will be explained with reference to the flowchart in Figure 23.

[0128] First, the reverse prevention control unit 72 uses the wheel speed ωtire estimated by the wheel speed estimation unit 20 to calculate the reverse prevention torque T using the following equation (20). rev Calculate (step S401).

[0129] Reverse prevention torque wrench rev =-KV w ...(20)

[0130] Here, the vehicle speed V w This is the wheel speed ω estimated by the wheel speed estimation unit 20. tireThis is the speed of vehicle 100, calculated from the radii of tires 111, 112, 121, and 122. Also, K is a coefficient determined by the backlash impact of the drivetrain.

[0131] Next, the reverse prevention control unit 72 flags the backlash passing flag F BL Determine whether the function is ON or whether the vehicle speed Vw is negative (step S402).

[0132] And then, flag F during backlash passage BL If the switch is ON, or if the vehicle speed Vw is negative, the reverse prevention control unit 72 will set the MG requested torque T MG The value is set to zero and output to inverters 96 and 97 (step S403).

[0133] Also, backlash passing flag F BL If the reverse prevention control unit 72 is not on and the vehicle speed Vw is zero or greater, the reverse prevention torque T rev However, the driver's required torque, that is, the required torque T mg2 Determine whether it exceeds (step S404).

[0134] And, reverse prevention torque T rev If the torque exceeds the driver's requested torque, the reverse prevention control unit 72 will set the reverse prevention torque T rev MG required torque T MG The output is then sent to inverters 96 and 97 (step S405).

[0135] Also, reverse-prevention torque wrench rev If the driver's requested torque is less than or equal to the driver's requested torque, the reverse prevention control unit 72 will set the driver's requested torque (requested torque T mg2 ) MG required torque T MG The output is then sent to inverters 96 and 97 (step S406).

[0136] By implementing the reverse-movement prevention control described above, even when vehicle 100 is stopped by regenerative braking, it becomes possible to suppress the phenomenon of rebound after stopping, which occurs because regenerative torque continues to be output even though the actual speed of vehicle 100 has become negative.

[0137] The control unit and method described herein may be implemented by a dedicated computer comprising a processor programmed to execute one or more functions embodied by a computer program. Alternatively, the apparatus and method described herein may be implemented by a dedicated computer comprising a processor composed of dedicated hardware logic circuits. Alternatively, the apparatus and method described herein may be implemented by one or more dedicated computers comprising a combination of a processor that executes a computer program and one or more hardware logic circuits. Furthermore, the computer program may be stored as instructions executed by the computer on a computer-readable non-transitional tangible recording medium.

[0138] 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 driving control device (10) for a vehicle (100) that drives by transmitting power from drive motors (89, 90) to tires (111, 112, 121, 122), A relaxation length calculation unit (32) calculates the relaxation length in the longitudinal direction of the tire, which is the distance required to move for the lateral force to reach a steady value when the tire is subjected to a slip angle, A slip ratio calculation unit (33) calculates a slip ratio indicating the degree of slip between the tire and the road surface by dividing the length of the deformation displacement of the tire in the longitudinal direction by the relaxation length calculated by the relaxation length calculation unit, A vehicle driving control device equipped with the following:

2. A rotation speed detection unit (91, 92) for detecting the motor rotation speed of the motor, A wheel speed estimation unit (20) estimates the wheel speed, which is the rotation speed of the tire, using the motor rotation speed detected by the rotation speed detection unit, The system further includes a vehicle speed calculation unit (12) that calculates the vehicle's body speed by integrating the vehicle's longitudinal acceleration, The slip ratio calculation unit calculates the length of the longitudinal deformation displacement of the tire using the wheel speed estimated by the wheel speed estimation unit and the vehicle speed calculated by the vehicle speed calculation unit. A vehicle driving control device according to claim 1.

3. The motor further comprises a torque calculation unit (11) that calculates the motor torque generated in the motor, The wheel speed estimation unit estimates the wheel speed using the motor rotation speed detected by the rotation speed detection unit, the motor torque calculated by the torque calculation unit, and the transmission characteristics of the coupling unit connecting the motor and the tire. The vehicle driving control device according to claim 2.

4. The vehicle driving control device according to claim 3, wherein the connecting portion comprises a reduction gear (85, 86) for reducing the rotational speed generated in the motor and a drive shaft (87, 88) for transmitting the rotation of the reduction gear to the tire.

5. The vehicle driving control device according to claim 4, wherein the wheel speed estimation unit calculates the rotation angle of the tire by subtracting, as correction values, an angular component generated by the twisting of the drive shaft, an angular component due to the inertia of the motor, and an angular component due to backlash in the reduction gear from the rotation angle of the motor calculated based on the motor rotation speed, and estimates the wheel speed by differentiating the calculated rotation angle of the tire.

6. The vehicle driving control device according to claim 5, wherein the wheel speed estimation unit calculates the angular component based on the backlash in the reduction gear using a second-order transfer function that represents the torsional resonance of the drive shaft.

7. The vehicle driving control device according to any one of claims 1 to 6, wherein the relaxation length is set according to the peak value of the coefficient of friction between the tire and the road surface.

8. A friction coefficient calculation unit (41) calculates the friction coefficient between the tire and the road surface using the motor torque calculated by the torque calculation unit, the brake torque when braking the vehicle, and the vehicle speed calculated by the vehicle speed calculation unit. A slope estimation unit (42) estimates the slope when the relationship between the slip ratio calculated by the slip ratio calculation unit and the friction coefficient calculated by the friction coefficient calculation unit is expressed as a linear function, The system further includes a friction coefficient peak value calculation unit (43) that calculates the peak value of the friction coefficient between the tire and the road surface from the slope estimated by the slope estimation unit, The relaxation length calculation unit determines the relaxation length based on the peak value of the friction coefficient calculated by the friction coefficient peak value calculation unit. A vehicle driving control device according to claim 3.

9. A vehicle driving control program for controlling a vehicle that moves by transmitting power from a drive motor to its tires, At least one processor, The tire's longitudinal relaxation length is calculated as the distance required for the lateral force to reach a steady state when the tire is subjected to a slip angle. The slip ratio, which indicates the degree of slip between the tire and the road surface, is calculated by dividing the length of the deformation displacement of the tire in the longitudinal direction by the calculated relaxation length. Vehicle driving control program.

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