Vehicle control device

Abstract

The vehicle control device (10) of the present application is provided with: an arithmetic unit (11) that calculates a target slip ratio (y) that is a target value of a slip ratio (λ) of a wheel (5); a limit unit (12) that sets an upper limit value (y max ) of the target slip ratio (y) based on at least a vehicle speed (V) of a vehicle (1), and limits the target slip ratio (y) calculated by the arithmetic unit (11) to be equal to or lower than the upper limit value (y max ); and a control unit (13) that controls a drive torque of the vehicle (1) so as to achieve a wheel speed that is the target slip ratio (y) limited by the limit unit (12).

Description

Technical Field

[0001] This invention relates to a vehicle control device mounted on a vehicle to control the slippage state of the wheels. Background Technology

[0002] Conventional methods involve calculating a target slip ratio for the vehicle and adjusting the vehicle's drive torque to match the actual wheel slip ratio. The target slip ratio is calculated, for example, based on the vehicle's required driving force. However, if the target slip ratio becomes too large, the wheels are prone to slipping. Therefore, the target slip ratio is limited to a predetermined upper limit (see Patent Documents 1-3).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2009-65793

[0006] Patent Document 2: Japanese Patent No. 4637136

[0007] Patent Document 3: Japanese Patent No. 4907390

[0008] The technical problem that the invention aims to solve

[0009] On the other hand, the optimal slip ratio can vary depending on the vehicle's driving conditions and road surface conditions. Therefore, if drive torque control is implemented with a fixed upper limit for the target slip ratio, driving performance and stability may decrease. For example, if the upper limit of the target slip ratio is too small, the friction between the wheels and the road surface decreases, resulting in a decline in driving performance (driving force and braking force). Conversely, if the upper limit of the target slip ratio is too large, the lateral force acting on the wheels decreases, leading to a decrease in vehicle body stability. Summary of the Invention

[0010] One objective of this invention is to provide a vehicle control device that improves the driving performance and stability of a vehicle, addressing the technical problems described above. Furthermore, this invention is not limited to this objective; other objectives can also be defined by the effects derived from the various structures shown in the "Detailed Embodiments" section below, which can produce effects unattainable using existing technologies.

[0011] Technical means for solving technical problems

[0012] The present invention can be implemented in the manner or application examples disclosed below. The vehicle control device of the present invention solves at least a portion of the above-described technical problems.

[0013] The vehicle control device disclosed herein is a vehicle control device mounted on a vehicle to control the slip state of the wheels, comprising: a calculation unit that calculates a target slip ratio as a target value of the slip ratio of the wheels; a limiting unit that sets an upper limit value of the target slip ratio based at least on the vehicle speed, and limits the target slip ratio calculated by the calculation unit to below the upper limit value; and a control unit that controls the driving torque of the vehicle to achieve a wheel speed that becomes the target slip ratio limited by the limiting unit.

[0014] The effects of the invention

[0015] The vehicle control device invented can improve the driving performance and stability of a vehicle. Attached Figure Description

[0016] Figure 1 This is a diagram illustrating a vehicle to which the vehicle control device, as an example, is applied.

[0017] Figure 2 It means Figure 1 The diagram shows the structural skeleton of the vehicle's drive system.

[0018] Figure 3 yes Figure 2 The velocity curve of the planetary gear mechanism is shown.

[0019] Figure 4 It means Figure 1 The diagram shows a block diagram of the structure of the vehicle control device.

[0020] Figure 5 It means by Figure 1 The mapping between the speed limit set by the limiting department and the upper limit value. Detailed Implementation

[0021] [1. Vehicle]

[0022] As an example, the vehicle control device is applied to Figure 1 The vehicle 1 shown is equipped with: left and right wheels 5 arranged side by side in the vehicle width direction; a power distribution mechanism 3 (differential mechanism) that imparts a torque difference to the left and right wheels 5; and a pair of electric motors 2 connected to the power distribution mechanism 3. In the figure, the letters R and L marked with numerical symbols indicate the configuration position of the element involved (on the right and left sides of the vehicle 1). For example, 5R indicates the right wheel (right side) of the left and right wheels 5, and 5L indicates the left wheel (left side).

[0023] The electric motor 2 has the function of driving at least one of the front or rear wheels of the vehicle 1, and may also have the function of driving all four wheels. The one of the pair of electric motors 2 located on the right is also referred to as the right motor 2R (right motor), and the one located on the left is also referred to as the left motor 2L (left motor). The right motor 2R and the left motor 2L operate independently of each other and can output different magnitudes of driving force respectively. These electric motors 2 are connected to the power distribution mechanism 3 via a pair of separately arranged reduction gears. In this embodiment, the right motor 2R and the left motor 2L have the same rated output and are arranged in pairs opposite each other.

[0024] Vehicle 1 is equipped with a power distribution mechanism 3, which amplifies the torque difference between a pair of electric motors 2 and distributes it to the left and right wheels 5 respectively. In this embodiment, the power distribution mechanism 3 is a differential mechanism with yaw control (AYC) function, and is inserted between the wheel axle 4 (left wheel axle 4L) connected to the left wheel 5L and the wheel axle 4 (right wheel axle 4R) connected to the right wheel 5R. The yaw control function refers to the function of adjusting the yaw torque by actively controlling the distribution ratio of the driving force (driving torque) of the left and right wheels 5, thereby stabilizing the posture of vehicle 1. Planetary gear mechanisms, differential gear mechanisms, etc., are built into the power distribution mechanism 3. Furthermore, the vehicle drive system including a pair of electric motors 2 and the power distribution mechanism 3 is also called a DM-AYC (Dual-Motor Active Yaw Control) device.

[0025] like Figure 2 As shown, the power distribution mechanism 3 includes a pair of reduction gears (composed of...) to reduce the rotational speed of the motor 2. Figure 2 The gear system enclosed by the dotted lines in the image), and the transmission mechanism (composed of...) Figure 2 (The gear system enclosed by a single-dot dashed line). The reduction mechanism is a mechanism that increases torque by reducing the torque (driving force) output from the motor 2. The reduction ratio of the reduction mechanism is appropriately set according to the output characteristics and performance of the motor 2. If the torque performance of the motor 2 is sufficiently high, the reduction mechanism can be omitted. In addition, the speed change mechanism is a mechanism that amplifies the torque difference transmitted to the left and right wheels 5 respectively.

[0026] Figure 2The transmission mechanism of the power distribution mechanism 3 shown includes a pair of planetary gear mechanisms. These planetary gear mechanisms have a structure in which the rotation axes of the planetary gears mounted on their respective planetary carriers are connected to each other. Each planetary carrier supports the planetary gears so that they can rotate on their own axes and also supports the planetary gears so that they can revolve between the sun gear and the ring gear. Furthermore, the driving force transmitted from the left and right motors 2 is input to the ring gear and sun gear of one planetary gear mechanism. The driving force transmitted to the left and right wheels 5 is output from the sun gear and planetary carrier of the other planetary gear mechanism. The ring gear of the other planetary gear mechanism is absent. Furthermore, Figure 2 The power distribution mechanism 3 shown is only one example of a mechanism for implementing yaw control; other known mechanisms can also be used.

[0027] Each motor 2L and 2R is electrically connected to the battery 7 via inverter 6 (6L, 6R). Inverter 6 is a converter (DC-AC inverter) that converts the power from the DC circuit on the battery 7 side (DC power) to the power from the AC circuit on the motor 2 side (AC power). The battery 7 is, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery, capable of supplying a high-voltage DC current of several hundred volts. When motor 2 is running, the DC power is converted to AC power by inverter 6 and supplied to motor 2. When motor 2 generates electricity, the generated electricity is converted to DC power by inverter 6 and used to charge the battery 7. The operation of inverter 6 is controlled by vehicle control device 10.

[0028] The vehicle control unit 10 is one of the electronic control units (ECU, Electronic Control Unit) installed in the vehicle 1. The vehicle control unit 10 includes a processor (central processing unit), a memory (main memory), a storage device, an interface device, etc. (not shown), and these components are connected to each other via an internal bus to enable communication. The decisions and controls performed by the vehicle control unit 10 are stored in the memory as firmware and application programs. During program execution, the program content is expanded in the memory space and executed by the processor.

[0029] like Figure 1As shown, the vehicle control unit 10 is connected to a throttle opening sensor 21, a brake sensor 22, a steering angle sensor 23, a mode selection switch sensor 24, a rotary transformer 25, and a wheel speed sensor 26. The throttle opening sensor 21 detects the amount of pressure applied to the accelerator pedal (throttle opening) and its application speed. The brake sensor 22 detects the amount of pressure applied to the brake pedal (brake pedal travel) and its application speed. The steering angle sensor 23 detects the steering angle (actual steering angle or steering wheel operation angle) of the left and right wheels 5. The mode selection switch sensor 24 is a device that integrates a switch for setting the vehicle 1's driving mode (e.g., snow mode, tarmac mode, etc.) selectable by the occupants and a sensor for detecting the operating state of the switch.

[0030] The rotary transformer 25 is used to detect the rotational angular velocity (i.e., the motor angular velocity ω) of the electric motor 2. Rm ω Lm The sensors are individually installed on each motor 2. Additionally, the wheel speed sensor 26 detects the rotational angular velocity (wheel angular velocity ω) output from the power distribution mechanism 3 to the wheel axle 4. Rds ω Lds The sensors 21-26 are located near the connection points between the power distribution mechanism 3 and the left and right wheel axles 4. The vehicle control unit 10 controls the operating state of the inverter 6 based on the information detected by these sensors 21-26, thereby controlling the output of the pair of electric motors 2. Furthermore, the type of sensor used to detect the rotational angular velocity of the electric motors 2 is not limited to the resolver 25, but can also be other sensors (such as Hall effect sensors or encoders).

[0031] [2. Control Model]

[0032] The control model associated with this embodiment will be explained. When a braking torque (braking torque and driving torque) is applied to the wheel 5 of the vehicle, causing a change in the rotational speed of the wheel 5, the relative speed with the vehicle body changes (slippage), and the ground contact deformation generates a braking force (braking force and driving force). Here, the vehicle weight is set as M, the vehicle speed (vehicle speed) is set as v, and the braking force is set as F. x Let the wheel inertia (moment of inertia) be J. w Set the wheel angular velocity to ω ds Shaft torque (braking drive torque) is set to T. ds Let the effective radius of the tire be r, and the wheel speed be V. w If we set the slip ratio as λ (the slip ratio obtained by standardizing the relative speeds of the vehicle body speed and the wheel speed), then the following equation holds true.

[0033]

Mathematical Formula 1

[0034] Formula 1

[0035] Formula 2

[0036] Formula 3 V w =rω ds

[0037] Formula 4

[0038] Furthermore, the variable obtained by standardizing the braking force by dividing it by the vertical resistance is called the friction coefficient μ. Generally, the relationship between the friction coefficient μ and the slip ratio λ is non-linear. The value of the friction coefficient μ is the specified slip ratio (optimal slip ratio λ). p0 The maximum value μ is obtained when ) ma x. Here, the transfer function of the wheel angular velocity relative to the axle torque input (expressing the input-output relationship as a function of the complex number s) is shown below. J in the following equation... n This is the nominal inertia. That is, for a certain slip ratio λ... n At (nominal slip ratio), the equivalent inertia of wheel 5 observed from the drive side is considered to be J. n .

[0039]

Mathematical Formula 2

[0040] Formula 5

[0041] Figure 3 This is a velocity graph related to the input and output of the power distribution mechanism 3. b1 and b2 in the graph are equivalent second speed ratios determined by the structure of the gears built into the power distribution mechanism 3. In this embodiment, the following equation holds.

[0042]

Mathematical Expression 3

[0043] Formula 6

[0044] T Rin T Lin It is based on the input torque after gear reduction and connection, and also includes the inertial torque on the motor side. Additionally, T Rm T Lm It is the torque after subtracting the inertial torque on the motor side, and can be expressed as follows.

[0045]

Mathematical Expression 4

[0046] Formula 7

[0047] T RIm T LIm This is the inertial torque of motor 2. Additionally, I... mIt is the inertia of motor 2, ω Rm ω Lm This is the angular velocity on the motor side after the first deceleration. Motor angular velocity ω Rm ω Lm Angular velocity ω on the drive shaft side Rds ω Lds The relationship is expressed by the following formula.

[0048]

Mathematical Expression 5

[0049] Formula 8

[0050] Due to the torque T transmitted to the drive shaft side Rds T Lds It is the coupled torque after subtracting the inertial torque of motor 2, and is therefore expressed by the following formula.

[0051]

Mathematical Expression 6

[0052] Formula 9

[0053] In addition, the following formula can be used in the calculation of inertial torque using wheel speed.

[0054]

Mathematical Expression 7

[0055] Formula 10

[0056]

[0057] Formula 11

[0058]

[0059] [3. Vehicle control device]

[0060] like Figure 1 As shown, at least an arithmetic unit 11, a limiting unit 12, and a control unit 13 are provided inside the vehicle control device 10. In this embodiment, as... Figure 4 As shown, the control unit 13 includes an FF control unit 14 and an FB control unit 15. In addition to the elements described above, a model calculation unit 16 and a driving force observer unit 17 are also provided. These elements are represented for the convenience of classifying the functions of the vehicle control device 10. These elements can be described as independent programs or as composite programs combining multiple elements. The programs corresponding to each element are stored in the memory or storage device of the vehicle control device 10 and executed by the processor.

[0061] The calculation unit 11 is a structure that separately calculates the target value of the slip ratio λ of wheels 5R and 5L, namely the target slip ratio y (slip ratio command value). The value of the target slip ratio y is calculated based at least on the required driving force of vehicle 1. In this embodiment, the value of the target slip ratio y is calculated based on the required driving force and the estimated driving force of vehicle 1. For example, the target slip ratio y is calculated based on the value (error) obtained by integrating the value obtained by subtracting the estimated driving force from the required driving force. The required driving force is calculated, for example, based on the information detected by sensors 21 to 26. Here, the definition of the target slip ratio y is as follows.

[0062]

Mathematical Expression 8

[0063] Formula 12

[0064] The target slip ratio y is defined in the same way as the slip ratio λ of vehicle 1 during braking (deceleration). The relationship between the braking slip ratio λ and the target slip ratio y is expressed by the following formula. If the slip ratio λ is sufficiently small, the two values ​​will be approximately the same.

[0065]

Mathematical Expression 9

[0066] Formula 13

[0067] Furthermore, if the value of the target slip ratio y calculated by the calculation unit 11 is too large, this value (absolute value) is limited to the upper limit value y set by the limiting unit 12 described later. max The following range. In this case, exceeding the upper limit value y. max The value of the quantity is discarded as the value of the remaining quantity. Therefore, in order to reflect the value of the remaining quantity in the next subsequent operation, it is also possible to import it back into the upstream side of the operation unit 11 after multiplying it by the specified gain and subtract it from the operation structure that requires the driving force.

[0068] Limiting section 12 sets an upper limit value for the target slip ratio y based at least on the vehicle speed V of vehicle 1. max Furthermore, the absolute value |y| of the target slip ratio y calculated by the calculation unit 11 is limited to the upper limit value y. max Below. From the upper limit value y max The target slip ratio y also includes the value on the braking side (negative side). Although the vehicle speed V mentioned here can also be based on the wheel angular velocity ω detected by the wheel speed sensor 26. Lds ω Rds The calculated value, but preferably based on the motor angular velocity ω detected by the rotary transformer 25. Rm ω Lm The calculated value. Upper limit value y max It functions as a limiter for the target slip ratio y. Figure 5This example illustrates the vehicle speed V and its upper limit value y. max The mapping of relationships. In Figure 5 The map represents the limiting characteristics of the driving side (positive side). This mapping is stored inside the vehicle control unit 10 (e.g., inside the limiting unit 12, in a memory accessible by the limiting unit 12, etc.).

[0069] In the above mapping, we set y as the upper limit value that increases with vehicle speed V. max The first speed range of the increasing vehicle speed region, V1 to V2, and the upper limit value y as the vehicle speed V increases. max The second speed range, V3 to V4, represents a decrease in vehicle speed. The first speed range, V1 to V2, represents the range where vehicle speed V increases from the first speed V1 to the second speed V2. The second speed range, V3 to V4, represents the range where vehicle speed V increases from the third speed V3 to the fourth speed V4. The values ​​of vehicle speed V are in the order 0 < V1 < V2 < V3 < V4. Compared to the first speed range, V1 to V2, the second speed range, V3 to V4, represents the higher speed range.

[0070] like Figure 5 As shown, the upper limit value y is set in the first vehicle speed range V1 to V2. max The value of has the characteristic of increasing with respect to vehicle speed V by an ascending gradient, the ascending gradient being A1. On the other hand, the upper limit value y is set in the second vehicle speed region V3~V4. max The value of has the characteristic that the gradient decreases as it rises relative to the vehicle speed V, and its descent gradient is -A2. Here, when comparing the absolute values ​​of the two gradients, the absolute value of the ascending gradient |A1| is set to be greater than the absolute value of the descent gradient |-A2|.

[0071] By making the absolute value of the ascending gradient |A1| a relatively large value, the upper limit value y is determined relative to the increase in vehicle speed V. max As the value of λ increases further, the target slip ratio y tends to approach the optimal slip ratio λ. p0 Furthermore, if the absolute value of the descent gradient |-A2| is set to be greater than or equal to the absolute value of the ascent gradient |A1|, then after the vehicle speed V increases to a certain level, the upper limit value y will be... max The value of |A2| decreases sharply, and the torque is excessively suppressed. In contrast, this decrease in experience can be prevented by setting the absolute value of the descent gradient |-A2| smaller than the absolute value of the ascent gradient |A1|.

[0072] Furthermore, in the above mapping, an upper limit value y is set that is independent of the magnitude of the vehicle speed V. max The third speed range V0 to V1 is set as the first predetermined value y1, and the upper limit value y is set independently of the magnitude of the speed V. maxThe fourth speed range, V4 to V5, is defined as the second specified value y2. The third speed range, V0 to V1, represents the speed range from the specified speed V0 to the first speed V1. The fourth speed range, V4 to V5, represents the speed range from the fourth speed V4 to the fifth speed V5. The values ​​of speed V are in the order 0 ≤ V0 < V1, V4 < V5.

[0073] The third speed range V0-V1 is a speed range on the lower speed side compared to the first speed range V1-V2, and the fourth speed range V4-V5 is a speed range on the higher speed side compared to the second speed range V3-V4. Here, the first predetermined value y1 is set to a value smaller than the second predetermined value y2. Furthermore, in the fifth speed range V2-V3, which is sandwiched between the first speed range V1-V2 and the second speed range V3-V4, the upper limit value y1 is independent of the magnitude of the speed V. max It is set to the third specified value y3. The upper limit value y max The size relationship is y1 <y2<y3。

[0074] By setting the first specified value y1 to a smaller value (smaller than the second specified value y2), the slippage of the stopped vehicle 1 after it starts moving is more strongly restricted, and acceleration is more easily increased. On the other hand, by setting the third specified value y3 to a larger value (larger than the first specified value y1 and the second specified value y2), the target slip ratio y is more easily maintained within the slip ratio λ range where the friction of the wheels 5R and 5L increases, and driving force is more easily increased. In addition, by setting the second specified value y2 to a smaller value again (at least smaller than the third specified value y3), vibrations caused by slippage and torque suppression in the mid-to-high speed range can be prevented. Furthermore, compared to when the vehicle 1 starts, acceleration is more easily increased in the mid-to-high speed range without excessively restricting the target slip ratio y. That is, by setting the second specified value y2 to a larger value than the first specified value y1, not only vibration reduction performance but also acceleration performance is improved.

[0075] In addition, parameters other than vehicle speed V can be reflected in the upper limit value y. max For example, the upper limit value y can also be set based on the driver's input, vehicle status (lateral acceleration, yaw rate, etc.), and road conditions. max To provide a specific example, when vehicle 1 is in snow mode, compared to when vehicle 1 is in asphalt mode, the upper limit value y will be used to correct it. maxThe gain X is set to a smaller value. Alternatively, when the road surface is prone to slippage (when the estimated coefficient of friction of the road surface is smaller than that of a normal road surface) and the acceleration and deceleration acting on vehicle 1 are large, the gain X is set to a smaller value; when the road surface is difficult to slippage and the acceleration and deceleration acting on vehicle 1 are small, the gain X is set to a larger value.

[0076] Gain X is related to the upper limit value y max The parameters being multiplied, for example, are set in a range greater than 0. The smaller the gain X is compared to 1, the higher the upper limit y becomes. max The smaller the product of y and gain X, the larger the gain X is compared to 1, and the upper limit of y. max The larger the product with the gain X, the higher the value. The value obtained after multiplying by the gain X is used as the upper limit of the final target slip ratio y. max With this design, the more slippery the road surface, the stronger the ability to suppress slippage, thus improving the stability of the vehicle's posture.

[0077] Control unit 13 controls the drive torque of vehicle 1 for each wheel 5R, 5L to achieve a wheel speed that meets the target slip ratio y limited by limit unit 12. Control unit 13 includes an FF control unit 14 responsible for controlling the required drive force and an FB control unit 15 responsible for controlling the target slip ratio y limited by limit unit 12. In FF control unit 14, the effective radius r of the controlled wheel 5R, 5L is multiplied by the required drive force to calculate the required wheel torque for that wheel 5R, 5L. If the wheels 5R, 5L are stuck, the left side of formula 1 is sufficiently small, and the shaft torque T... ds With the effective radius r of the tire and the braking driving force F x The product rF x They are roughly the same. Therefore, by generating a driving force that is approximately equal to the driving force command value through feedforward, the driving force control system can compensate for slight errors through feedback.

[0078] Furthermore, in the FB control unit 15, feedback control quantities for the torque of wheels 5R and 5L are calculated. The required wheel torque calculated by the FF control unit 14 is added to the feedback control quantity calculated by the FB control unit 15 to obtain the final output torque T of wheels 5R and 5L. Based on this output torque T, the operating state of a pair of motors 2 is controlled. In addition, known methods can be applied as the calculation method for converting the torque of wheel axle 4 into the torque of motor 2.

[0079] Regarding the calculation of the feedback control quantity, in the FB control unit 15, for example, the value obtained by multiplying the vehicle speed v in the previous calculation cycle by the target slip ratio y plus 1 is used. Furthermore, this value is divided by the effective radius r of the wheels 5R and 5L, which are the controlled objects, to calculate the target angular velocity value ω* of those wheels 5R and 5L. Subsequently, the torque feedback control quantity (e.g., PI control quantity) is calculated in a way that reduces the difference between the actual angular velocity ω of those wheels 5R and 5L in the previous calculation cycle and the target angular velocity value ω* (ideally, the difference is 0). Alternatively, the estimated values ​​of vehicle speed v and angular velocity ω calculated by the model calculation unit 16 can be used instead of the vehicle speed v and angular velocity ω from the previous calculation cycle.

[0080] Furthermore, when designing wheel speed control using the extreme configuration method, if the poles are set as conjugate complex numbers, the real part is set as -a (a>0), and the imaginary part is set as b, then the wheel speed control is PI (proportional-integral) control, and its proportional gain K... p and integral gain K i As shown below. Here, if b = 0, then since it is a repeated real root, the response of the wheel speed control cycle becomes critically decaying.

[0081]

Mathematical Formula 10

[0082] Formula 14 K p =2I n a

[0083] Formula 15 K i =J n (a 2 +b 2 )

[0084] The model calculation unit 16 calculates estimated values ​​of vehicle speed, wheel speed, and vehicle body acceleration when wheels 5R and 5L are driven by the output torque T, based on a specified vehicle model. These estimated values ​​can be derived, for example, by applying a known calculation method for converting the torque of the motor 2 into the torque of the wheel axle 4.

[0085] The driving force observer unit 17 calculates the estimated driving force based at least on the output torque T. Here, for example, the inertial torque J of each of the left and right wheels 5 is calculated based on the wheel speeds calculated by the model calculation unit 16. ws Next, the inertial torque J is subtracted from the output torque T. ws The estimated shaft torque is then obtained. The estimated driving force is calculated by dividing this estimated shaft torque by the effective radius r of the wheel 5R, 5L.

[0086] The aforementioned inertial torque J wsAlternatively, it can be calculated based on the detection value of the rotary transformer 25. For example, based on Formula 8 above, the motor angular velocity ω detected by the rotary transformer 25 can be used. Rm ω Lm Estimate the wheel speeds of the left and right wheels 5 (angular velocity ω on the drive axle side). Rds ω Lds Additionally, due to the inertial torque J of each of the left and right wheels 5 ws This is equivalent to the second term on the right side of Formula 10 and the second term on the right side of Formula 11, and therefore can be calculated based on the respective wheel speeds. Subsequently, by subtracting the inertial torque J from the output torque T... ws The estimated driving force is calculated by dividing the estimated shaft torque obtained later by the effective radius r of the wheel 5R and 5L.

[0087] [4. Function / Effect]

[0088] (1) In the above embodiment, the vehicle control device 10 is provided with a calculation unit 11, a limiting unit 12, and a control unit 13. The calculation unit 11 calculates the target value of the slip ratio λ of wheels 5R and 5L, i.e., the target slip ratio y. The limiting unit 12 sets an upper limit value y of the target slip ratio y based at least on the vehicle speed V of vehicle 1. max The target slip ratio y calculated by the calculation unit 11 is limited to an upper limit value y. max The control unit 13 controls the driving torque of the vehicle 1 to achieve a wheel speed that reaches the target slip ratio y limited by the limiting unit 12.

[0089] This structure allows the target slip ratio y to approach the optimal value corresponding to vehicle speed V, thereby improving the driving performance and stability of vehicle 1. In particular, it relates to the upper limit value y. max Compared to existing controls, the values ​​are set to be fixed, which allows for the appropriate separation of the permissible slip speed range and the speed range limiting the slip of wheels 5L and 5R, thereby improving the driving performance and stability of vehicle 1.

[0090] (2) In the above embodiment, the limiting unit 12 can set an upper limit value y based on the driver's operation amount, vehicle status (lateral acceleration, yaw rate, etc.), and road surface status of the vehicle 1. max For example, the upper limit value y is set according to the driving mode selected by the mode selection switch sensor 24. max This can further improve the driving performance and stability of vehicle 1. Additionally, in situations where the road surface is prone to slippage or the acceleration and deceleration acting on vehicle 1 are large, reducing the upper limit value y... max This can effectively suppress slippage and improve the stability of the vehicle's posture. On the other hand, when the road surface is not prone to slippage and the acceleration and deceleration acting on vehicle 1 are relatively small, increasing the upper limit value y... maxThis allows the target slip ratio y to approach the optimal slip ratio λ. p0 This will improve the driving performance of vehicle 1.

[0091] (3) In the above embodiment, the calculation unit 11 can calculate the target slip ratio y based on the required driving force and the estimated driving force of the vehicle 1. With this structure, the responsiveness of the feedback can be improved, and the target slip ratio y can be controlled with high precision. Therefore, the driving performance and stability of the vehicle 1 can be improved.

[0092] (4) In the above embodiment, the limiting part 12 can use the rotational angular velocity of the motor 2 (motor angular velocity ω). Rm ω Lm To set the upper limit value of the target slip ratio y for each of the left and right wheels 5. max With this structure, the detected value (wheel angular velocity ω) can be used, for example, based on the wheel speed sensor 26. Lds ω Rds The upper limit value y is set based on the vehicle speed V. max Compared to the previous situation, it can improve the responsiveness and controllability of the target slip ratio y. Therefore, it can improve the driving performance and stability of vehicle 1.

[0093] (5) Figure 5 As shown, at the specified vehicle speed V and the upper limit value y max In the mapping of the relationship, an upper limit value y is set as an increase accompanying the vehicle speed V. max The first speed region V1~V2 of the increasing vehicle speed range and the speed region V1~V2 which is the high-speed side, with the upper limit y increasing as the vehicle speed V increases. max The second speed region, V3–V4, is decreasing. Furthermore, the absolute value of the upward gradient |A1| in the first speed region V1–V2 is set to be larger than the absolute value of the downward gradient |-A2| in the second speed region V3–V4. This structure allows the target slip ratio y in the low-speed region to approach the optimal slip ratio λ earlier. p0 This improves the driving performance of vehicle 1. Furthermore, it avoids excessive torque suppression in the mid-to-high speed range, preventing a decline in driving experience.

[0094] (6) In Figure 5 In the mapping shown, a speed region is set as the lower speed side compared to the first speed region V1~V2, and the upper limit value y is set regardless of the magnitude of the speed V. max The third speed range V0~V1 is set as the first predetermined value y1, and the speed range V3~V4, compared to the second speed range, is the high-speed side speed range, with the upper limit value y1 being independent of the magnitude of the speed V. maxThe fourth vehicle speed range, V4 to V5, is defined as the second predetermined value y2. Furthermore, the first predetermined value y1 is set to be smaller than the second predetermined value y2. This structure suppresses slippage during vehicle 1's start-up (at extremely low speeds), improving acceleration performance. Additionally, by preventing slippage in the mid-to-high speed range and vibrations associated with torque suppression, vibration damping and acceleration performance are further improved.

[0095] [5. Variations]

[0096] The above embodiments are merely illustrative and are not intended to exclude the application of various modifications and techniques not explicitly shown in these embodiments. The structures of these embodiments can be modified and implemented in various ways without departing from their main principles. Furthermore, they can be selected or appropriately combined as needed.

[0097] For example, in the above embodiment, a vehicle control device 10 applied to the rear wheels of vehicle 1 is illustrated, but the same vehicle control device can also be applied to the front wheels, or the same vehicle control device can be applied to both the front and rear wheels. In a vehicle 1 that has at least a vehicle control device 10 for controlling the slip state of wheels 5R and 5L, the same effect as the above embodiment can be achieved by implementing the same control as in the above embodiment.

[0098] When implementing the vehicle control device involved in this application, the driving force control method described in the following references can be referred to.

[0099] Hiroshi Fujimoto, Takeshi Takano, Hidetoshi Nobumoto, and Toshimi Okazaki, “Drive Force Control Technology Based on High-Precision Slip Ratio Control”, Mazda Technical Report, No. 32, pp. 228-233 (2015);

[0100] Hiroshi Fujimoto, Junya Amada, and Takayuki Miyajima, “Development and Control of Electric Vehicles with Variable Drive Unit Systems”, Proceedings of the 2013 Spring Conference of the Automotive Technology Society, No. 8-13, pp. 17-20 (2013);

[0101] Masataka Yoshimura and Hiroshi Fujimoto, “Driving Torque Control Method for Electric Vehicles Equipped with Wheel Motors”, Journal of Electrical Engineering, Vol. 131, No. 5, p. 721-728 (2011).

[0102] Symbol Explanation

[0103] 1 vehicle

[0104] 2 electric motors

[0105] 3. Power distribution mechanism (differential mechanism)

[0106] 4 wheel axles

[0107] 5. Left and right wheels (wheels)

[0108] 6 inverters

[0109] 7 batteries

[0110] 10. Vehicle Control Unit (ECU)

[0111] 11 Computational Department

[0112] 12 Restriction Section

[0113] 13 Control Department

[0114] 14FF Control Unit

[0115] 15FB Control Department

[0116] 16 Model Calculation Department

[0117] 17 Driving Force Observation Unit

[0118] 21 Throttle Opening Sensor

[0119] 22 Brake Sensors

[0120] 23 Steering angle sensor

[0121] 24-mode selection switch sensor

[0122] 25 Rotary Transformers

[0123] 26 wheel speed sensors

[0124] λ slip ratio

[0125] λ p0 Optimal slip ratio

[0126] y target slip ratio

[0127] y max Upper limit

Claims

1. A vehicle control device, mounted on a vehicle and controlling the slippage state of the wheels, characterized in that, have: The calculation unit calculates the target slip ratio, which is the target value of the slip ratio of the wheel; A limiting unit, which sets an upper limit value for the target slip ratio based at least on the vehicle speed, and limits the target slip ratio calculated by the calculation unit to below the upper limit value; and A control unit controls the driving torque of the vehicle to achieve a wheel speed that achieves the target slip ratio limited by the limiting unit. The calculation unit calculates the target slip ratio based on the value obtained by integrating the value obtained by subtracting the estimated driving force from the required driving force of the vehicle.

2. The vehicle control device according to claim 1, characterized in that, The limiting unit sets the upper limit value based on the driver's operating volume, vehicle status, or road conditions.

3. The vehicle control device according to claim 1, in a vehicle having a differential mechanism that imparts a torque difference to the left and right wheels and a pair of electric motors connected to the differential mechanism, the vehicle control device controls the slip state of the left and right wheels respectively by controlling the operating state of the pair of electric motors, characterized in that, The limiting unit sets the upper limit value of the target slip ratio for each of the left and right wheels based on the rotational angular velocity of the pair of electric motors.

4. The vehicle control device according to claim 2, in a vehicle comprising a differential mechanism that imparts a torque difference to the left and right wheels and a pair of electric motors connected to the differential mechanism, wherein the vehicle control device controls the slip state of the left and right wheels respectively by controlling the operating state of the pair of electric motors, characterized in that, The limiting unit sets the upper limit value of the target slip ratio for each of the left and right wheels based on the rotational angular velocity of the pair of electric motors.

5. The vehicle control device according to any one of claims 1 to 4, characterized in that, The limiting part has a mapping that specifies the relationship between the vehicle speed and the upper limit value. The mapping has a first vehicle speed region and a second vehicle speed region. In the first vehicle speed region, the upper limit value increases as the vehicle speed increases. The second vehicle speed region is a high-speed region compared to the first vehicle speed region. In the second vehicle speed region, the upper limit value decreases as the vehicle speed increases. The absolute value of the upper limit value in the first speed region relative to the upward gradient of the speed is greater than the absolute value of the upper limit value in the second speed region relative to the downward gradient of the speed.

6. The vehicle control device according to claim 5, characterized in that, The mapping has a third speed region and a fourth speed region. The third speed region is a speed region on the lower speed side compared to the first speed region, and in this third speed region, the upper limit value is set to a first predetermined value regardless of the magnitude of the vehicle speed. The fourth speed region is a speed region on the higher speed side compared to the second speed region, and in this fourth speed region, the upper limit value is set to a second predetermined value regardless of the magnitude of the vehicle speed. The first specified value is smaller than the second specified value.

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