JP6578146B2 - Slip control device - Google Patents

Description

  The present invention relates to a slip control device for suppressing tire slip of a vehicle and ensuring the stability of the vehicle posture.

  2. Description of the Related Art Conventionally, a slip control device for preventing a wheel from spinning or locking when a vehicle body is accelerated or decelerated is known. In addition, when accelerating or decelerating, pitching vibration may occur in which the front and rear of the vehicle vibrate up and down in opposite phases. A slip control device that suppresses pitching vibration or reduces the influence of pitching vibration on slip rate control is proposed. Has been. (For example, Patent Documents 1 and 2)

JP-A-8-20323 JP 2013-225975 A

When the vehicle accelerates, a so-called squat is generated in which the vehicle rises forward, but when the tire slips during acceleration and the driving torque is loosened by traction control, a force in the squat canceling direction acts on the vehicle body. As a result, a pitching vibration in which the front and rear of the vehicle body vibrate up and down in opposite phases is generated, and there is a problem that riding comfort is deteriorated.
In addition, when the vehicle decelerates, a so-called nose dive occurs that lowers the vehicle forward.If the tire slips during deceleration and the braking torque is loosened by antilock brake control, the force in the direction of eliminating the nose dive is applied to the vehicle body This causes a problem that the vehicle vibrates and pitches and the ride comfort is deteriorated.
In either case, the load applied to each wheel is changed by the pitching vibration of the vehicle body, and the pitching vibration frequency component is included in the waveforms of the slip ratio and the braking / driving torque, and the pitching vibration may be sustained.

  In Patent Document 1, the brake fluid pressure during a predetermined period from the start of control by the antilock brake control means is corrected to be shallower than the period following the predetermined period (the brake fluid pressure is slightly reduced). ing. As a result, even when nose diving accompanying braking begins to occur, the nose diving is mitigated, the pitching motion of the vehicle is suppressed, and the ride comfort can be prevented from being lowered. However, since the braking force is relaxed regardless of the occurrence of pitching vibration, the braking performance is degraded.

  In Patent Document 2, a band elimination filter is used to remove the pitching vibration frequency component of the vehicle body included in the slip ratio and the drive torque. Thereby, the influence which a pitching vibration frequency component has on the slip control of a wheel can be reduced. However, since the physical quantity used for the feedback control is filtered, there is a possibility that a delay occurs due to the filter, and the control accuracy deteriorates or the system becomes unstable.

  An object of the present invention is to provide a slip control device that can suppress tire slip that occurs when accelerating or decelerating, and that can also suppress pitching vibration of a vehicle body.

The slip controller 12 of the premise configuration includes a slip ratio calculating means 16 that calculates a slip ratio using the wheel rotation speed and the vehicle speed, and the calculated slip ratio does not exceed the slip ratio limit value. A slip control device comprising slip ratio control means 17 for performing slip ratio control, and slip ratio limit value changing means 18 capable of changing the magnitude of the slip ratio limit value,
Pitching vibration detection means 19 for detecting pitching vibration of the vehicle body is provided, and the slip ratio limit value changing means 18 is configured to perform the pitching control when slip ratio control by the slip ratio control means 17 is executed for one or more wheels. When the vibration detection means 19 detects the pitching vibration of the vehicle body, the slip ratio limit value of the front wheel 2 during acceleration and the rear wheel 3 during deceleration of at least one of the wheels on which slip ratio control is being executed The absolute value of is reduced.

According to this configuration, the slip ratio calculating means 16 and the slip ratio control means 17 for controlling the slip ratio so that the magnitude of the slip ratio does not exceed the magnitude of the slip ratio limit value are included. Tire slip can be suppressed.
Further, when the slip ratio limit value changing means 18 is provided and the pitching vibration of the vehicle body is detected during the execution of the slip ratio control, the slip ratio of at least one of the wheels on which the slip ratio control is being performed. Since the limit value is reduced, pitching vibration of the vehicle body can also be suppressed.

As described above, even when the slip control is activated during acceleration or deceleration and the pitching vibration is generated, the pitching vibration can be reduced.
Further, when no pitching vibration is detected, the slip ratio is controlled so that the maximum longitudinal force can be generated, so that the maximum acceleration or deceleration performance can be exhibited.
Even when the pitching vibration is detected and the mode is shifted to the pitching vibration suppression mode, if the slip rate is decreased only during the period during which the pitching vibration is generated and then returned to a predetermined value, the acceleration or deceleration performance is substantially reduced. I don't have to.

During acceleration, easy front wheel slip ratio becomes oscillatory for the front wheel load is decreased, the rear wheel slip ratio is liable to vibrate because the load of the rear wheel is decreased during deceleration. Therefore, pitching vibration can be effectively suppressed by reducing the absolute value of the slip ratio limit value of the front wheels during acceleration and the rear wheels during deceleration.

In the present invention, a band pass filter 20 having a characteristic of passing a frequency component near the pitching natural frequency of the vehicle body is provided for the longitudinal acceleration signal of the vehicle body detected by the longitudinal acceleration detection unit 14, and the pitching vibration detection unit 19 is provided. May determine whether or not pitching vibration is generated from the longitudinal acceleration filtered by the band-pass filter 20.
Since the presence or absence of pitching vibration is determined by the frequency component near the pitching natural frequency of the vehicle body, it is possible to extract the pitching vibration from various types of vibrations, and to accurately determine the presence or absence of the occurrence of pitching vibration. it can.

In this case, the slip ratio limit value changing means 18 gradually increases the absolute value of the reduced slip ratio limit value in accordance with a decrease in the amplitude of the longitudinal acceleration filtered by the bandpass filter 20 to a predetermined value. You may make it return to a value.
As the pitching vibration is reduced, the slip ratio limit value is gradually increased, so that the slip ratio limit value can be returned to the predetermined value without causing the pitching vibration again. Alternatively, the driving force can be generated again. The “predetermined value” is arbitrarily determined by design.

The inventions of the slip control device 12, Oite the premise construction, the slip rate limit value changing means 18 in accordance with a decrease in the operation amount of the accelerator operating means 13a or the brake operating means 13b, the slip rate limits decreased gradually increasing the absolute value of the value to return to a predetermined value.
The braking / driving force can be recovered without causing pitching vibration again by gradually increasing the slip ratio limit value according to the decrease in the accelerator operation amount and returning it to the reference slip ratio limit value. . The “predetermined value” is arbitrarily determined by design.

The slip control device according to the present invention includes a slip ratio calculating means for calculating a slip ratio using wheel rotational speed and vehicle speed, and a slip ratio so that the calculated slip ratio does not exceed the slip ratio limit value. In a slip control apparatus comprising slip ratio control means for performing rate control and slip ratio limit value changing means capable of changing the magnitude of the slip ratio limit value, pitching vibration detecting means for detecting pitching vibration of the vehicle body is provided. The slip ratio limit value changing means detects the slip ratio when the pitching vibration detecting means detects the pitching vibration of the vehicle body when the slip ratio control by the slip ratio control means is executed for one or more wheels. control over at least one wheel of the wheel running, acceleration front wheel, deceleration rear wheel slip rate limits The absolute value is lowered, the slip rate limit value changing means, according to the decrease of the operation amount of the accelerator operating means or the brake operating means, gradually predetermined value to increase the absolute value of the reduced slip rate limit order to return, it is possible to suppress the tire slip occurring when, for example acceleration or deceleration, it is possible to suppress the pitching vibration of the vehicle body.

It is a schematic explanatory drawing of the vehicle carrying the slip control apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of a conceptual composition of the slip control device. It is explanatory drawing of the example of a change of the slip ratio limit value in the slip control apparatus. It is explanatory drawing which shows the operation | movement description at the time of carrying out rapid acceleration on a low micro road in comparison with the case where the control of the embodiment is not performed. It is a schematic explanatory drawing of the vehicle to which the slip control apparatus which concerns on other embodiment of this invention is applied. It is a block diagram of a conceptual structure of the slip control apparatus which concerns on the said other embodiment. It is sectional drawing of schematic structure of an example of an in-wheel motor drive device.

A first embodiment of the present invention will be described with reference to FIGS. This embodiment is an example applied to an electric vehicle provided with an in-wheel motor drive device on four wheels.
In FIG. 1, an in-wheel motor drive device IWM is provided on the wheels 2 and 2 that are front wheels and the wheels 3 and 3 that are rear wheels of the vehicle 1. The in-wheel motor drive device IWM includes, for example, as shown in FIG. . The rotation of the motor 4 is transmitted to the wheels 2 and 3 via the speed reducer 6 and the wheel bearing 7. A brake rotor 8a constituting a friction brake 8 is fixed to the flange portion of the hub wheel 7a of the wheel bearing 7, and the brake rotor 8a rotates integrally with the wheels 2 and 3. The motor 4 is, for example, an embedded magnet type synchronous motor in which a permanent magnet is built in the core portion of the rotor 4a. The motor 4 is a motor in which a radial gap is provided between a stator 4b fixed to the housing 4c and a rotor 4a attached to the rotation output shaft 9. Each in-wheel motor drive unit IWM includes a wheel speed sensor 5 that detects the wheel rotation speed of the wheels 2 and 3.

  In FIG. 1, a vehicle 1 includes an inverter device 11 that controls each in-wheel motor drive device IWM of four wheels, and a host controller 10. The host controller 10 is, for example, an ECU (electric control unit) that performs overall cooperative control, overall control, and the like of the vehicle 1, and is based on the detected values of the operation amounts of the accelerator operation unit 13 a and the brake operation unit 13 ba. A braking / driving force distribution means 10a that calculates braking / driving torque and distributes the braking / driving torque to each inverter device 11 is provided. The accelerator operation means 13a and the brake operation means 13b are an accelerator pedal and a brake pedal, respectively, and the stroke amount and the depression amount are the operation amounts. In addition to this, the braking / driving force distribution means 10a may calculate the braking / driving torque in consideration of the detection values of other sensors for posture control and the like. In FIG. 1, the sensors for detecting the operation amounts of the accelerator operating means 13 a and the brake operating means 13 b and the other sensors are collectively referred to as various sensors 13 and shown as one block.

Slip control device 12 is a device for controlling the slip of each wheel 2, 3, separate from the host controller 10 or provided as part of the host controller 10. The Slip control device 12, the detection value of the detection to vehicle speed detecting means 15 and the longitudinal acceleration detected is and the vehicle speed longitudinal acceleration sensor 14 and the vehicle speed to measure the longitudinal acceleration of the vehicle 1 are inputted. The vehicle speed detection means 15 detects the rotational speeds of the wheels 2 and 3 by the wheel speed sensor 5 (see FIG. 7), and among them, the highest speed during deceleration and the lowest speed during acceleration are used as the vehicle speed. The vehicle speed is detected by a method, a method based on integration of acceleration of wheel rotation speed, a method combining the two, or the like. The vehicle speed detection means 15 may detect the wheel rotation speed of the wheels 2 and 3 from the output of a sensor (not shown) that detects the rotation of the motor 4 (see FIG. 7).

  FIG. 2 is a control block diagram of the slip control device 12. The slip control device 12 includes a slip ratio calculation means 16, a slip ratio control means 17, and a slip ratio limit value change means 18, and further includes a pitching vibration detection means 19 and a band pass filter 20.

  As described above, the torque command value of each wheel 2 and 3 output from the host controller 10 is a command value of driving torque or braking torque calculated from the stroke amount of the accelerator pedal or the depression force of the brake pedal. The braking torque is a negative value.

ここで、ｒはタイヤ半径である。スリップ率λはタイヤの滑り度合いを表しており、グリップ状態ではλ＝０、ロック時はλ＞０であり、ホイルスピン時（空転）はλ＜０とする。 The slip ratio calculating means 16 calculates the slip ratio λ (λ ₁ , λ ₂ , λ ₃ , λ ₄ ) of each wheel from the wheel rotation speed ω and the vehicle speed V according to the following equation.

Here, r is a tire radius. The slip ratio λ represents the degree of slipping of the tire. In the grip state, λ = 0, λ> 0 when locked, and λ <0 during wheel spin (idling).

The slip ratio control means 17 monitors the slip ratio calculated by the slip ratio calculation means 16 of each of the wheels 2 and 3, and the magnitude of the slip ratio of one of the wheels is the slip ratio limit value λ ^* (upper limit value ( <0)), or when the lower limit value (<0) is exceeded, the braking torque or drive torque of the wheel is controlled so that the excess wheel is within the slip ratio limit value (lower limit value and lower limit value). (Slip rate control) Specifically, when the magnitude of the slip ratio of any of the wheels exceeds the slip rate limit value lambda ^*, performs PID calculation based on the deviation between the slip ratio lambda and slip rate limit value lambda ^* in the controller 21 , PID calculation values K _PID1 , K _PID2 , K _PID3 , K _PID4 are obtained.

ここで、Ｋ_Ｐ，Ｋ_Ｉ，Ｋ_Ｄは、それぞれ比例演算，積分演算，微分演算のゲイン定数である。

Here, K _P , K _I , and K _D are gain constants for proportional calculation, integral calculation, and differential calculation, respectively.

The slip ratio calculating means 16 calculates torque command output values T _{1 to} T ₄ by adding PID calculation values (K _PID1 , K _PID2 , K _PID3 , K _PID4 ) to the torque command values for the wheels 2 and 3. To do. When the torque command value T (T _{1 to} T ₄ ) is negative, that is, when the regenerative brake is applied, the braking force is loosened, and when the torque command output value T (T _{1 to} T ₄ ) is positive, the drive is performed. Loosen the torque. As a result, the braking / driving torque (braking torque or driving torque) of the wheel is controlled so that the slip ratio λ is less than or equal to the slip ratio upper limit value (or the lower limit value), which is the slip ratio limit value λ ^*. Spin can be suppressed.

  The pitching vibration detection means 19 detects the pitching vibration of the vehicle body. In this case, a pitching vibration frequency component is extracted from the output signal of the longitudinal acceleration sensor 14 through the band pass filter 20. Here, the band pass filter 20 is designed to have the pitching natural frequency of the vehicle body as a pass band. The pitching vibration detection means 19 detects pitching vibration from the filtered longitudinal acceleration. That is, it is determined whether or not it is in a pitching vibration state. For example, when the longitudinal acceleration fluctuates a predetermined number of times with an amplitude equal to or greater than a predetermined threshold around 0, it is determined that the pitching vibration state is present.

The slip ratio limit value changing means 18 detects slipping vibration of the vehicle body by the pitching vibration detecting means 19 when slip ratio control by the slip ratio control means 17 is being executed for one or more wheels. The magnitude of the slip ratio limit value (absolute value) of at least one of the wheels on which rate control is being performed is reduced.
In this case, at the time of acceleration, the slip ratio lower limit value of the wheel for which slip ratio control is being performed is increased from a predetermined reference slip ratio limit value −λ ^* _S (<0) (the magnitude of the lower limit value is decreased). When the vehicle is decelerating, the upper limit value of the slip rate of the wheel for which slip rate control is being performed is reduced below a predetermined reference slip rate limit value λ ^* _S (<0) (when this control is referred to as “pitching vibration suppression mode”) There).

When accelerating, the load on the front wheels decreases, so the slip ratio of the front wheels tends to be oscillating, and when decelerating, the load on the rear wheels decreases, so the slip ratio of the rear wheels tends to oscillate. Therefore, pitching vibration can be effectively suppressed by reducing the absolute value of the slip ratio limit value of the front wheels during acceleration and the rear wheels during deceleration.
Since the slip ratio limit value of the wheel that increases the load (rear wheel during acceleration, front wheel during deceleration) is not changed, acceleration / deceleration performance is hardly degraded. Generally, since the longitudinal force that can be generated saturates as the wheel slip ratio increases, the slip ratio at which the longitudinal force is approximately saturated is set as the reference slip ratio limit value λ ^* _S.

  After that, as will be described later, the absolute value of the slip ratio limit value is gradually increased (lower limit value is increased or upper limit value is increased) to return to the reference slip ratio limit value value in accordance with the decrease in the longitudinal acceleration amplitude. .

When the slip ratio limit value (absolute value) decreases, the actual slip ratio also decreases and the pitching vibration frequency component included in the actual slip ratio also decreases. Thereby, the magnitude of the pitching vibration frequency component included in the braking / driving torque is also reduced, and the pitching vibration is reduced.
When slip ratio control is executed for all four wheels, the slip ratio limit value changing means 18 reduces the magnitude of the slip ratio limit value (absolute value) for only the front wheels during acceleration and only for the rear wheels during deceleration. The front wheel during acceleration and the rear wheel load during deceleration are reduced, and the slip rate is easily affected by load fluctuations caused by pitching vibration. Therefore, it is possible to effectively reduce pitching vibration and increase the load (rear wheel during acceleration). Since the slip ratio of the front wheels during deceleration does not decrease, the decrease in acceleration or deceleration performance can be suppressed.

  The slip ratio limit value changing means 18 gradually increases the magnitude of the slip ratio limit value (absolute value) in accordance with the decrease in the longitudinal acceleration amplitude filtered by the bandpass filter 20 (decreases the lower limit value, or Increase the upper limit value) and return it to the value of the reference slip ratio limit value. Alternatively, the magnitude of the slip ratio limit value (absolute value) is gradually increased in accordance with a decrease in the accelerator or brake depression amount (operation amount) to return to the reference slip ratio limit value. As a result, the braking / driving force can be recovered without generating pitching vibration again.

When pitching vibration of the vehicle body is detected by the above control, the slip ratio limit value (absolute value) is reduced, and the actual slip ratio is also reduced by the slip control. Therefore, the slip ratio is included in the slip ratio. The amplitude of the pitching vibration frequency component is reduced. Thereby, the amplitude of the pitching vibration frequency component included in the braking / driving torque is also reduced, and the pitching vibration is reduced. As the pitching vibration is reduced, the slip ratio limit value (absolute value) is gradually increased, so that it can be returned to the predetermined value without causing the pitching vibration again, and the maximum braking or driving that can occur. Force can be generated again.
When the pitching vibration of the vehicle body is not detected, the mode does not shift to the pitching vibration suppression mode, and the acceleration or deceleration performance does not deteriorate. Even when the pitching vibration is detected and the mode is shifted to the pitching vibration suppression mode, the slip ratio is decreased only during the period when the pitching vibration is generated and then returned to a predetermined value, so that the acceleration or deceleration performance is almost lowered. Absent.

  FIG. 3 shows an example of changing the slip ratio limit value. When no pitching vibration is detected, the reference slip ratio limit value, that is, the slip ratio at which the maximum longitudinal force can be generated is controlled, so that the maximum acceleration or deceleration performance can be exhibited. Even when the pitching vibration is detected and the mode is shifted to the pitching vibration suppression mode, the slip ratio is reduced only during the period in which the pitching vibration is generated, and then returned to a predetermined value, so that the acceleration or deceleration performance is almost lowered. There is nothing.

  FIG. 4 shows an operation example of the control of this embodiment (referred to as “main control”) when the vehicle is suddenly accelerated on a low μ road. When this control is not applied, the longitudinal acceleration vibrates greatly after the start of acceleration, and pitching vibration is generated. When this control is applied, pitching vibration occurs immediately after the start of acceleration, but by detecting the pitching vibration and increasing the slip ratio lower limit value, the amplitude of vibration in the longitudinal acceleration is reduced and the pitching vibration is suppressed. Yes.

  In the above-described embodiment, the description has been given using the electric vehicle including the in-wheel motor driving device IWM on the four wheels. Control methods can be applied.

  For example, the control during deceleration can be applied to a vehicle (FIGS. 5 and 6) in which the friction brake 8 is mounted on each wheel. In this case, the braking force command value calculated by the slip control device 12 is sent to the hydraulic control device 31 for each wheel. The hydraulic control device 31 for each wheel controls the friction brake 8 independently for each wheel so as to generate the braking force of the received braking force command value. 5 and FIG. 6 are the same as those in the first embodiment described above with reference to FIGS.

  In FIG. 5, a total of four hydraulic control devices 31 are described for each wheel, but a hydraulic circuit for four wheels is provided in one hydraulic control device, and the hydraulic pressure of each wheel is controlled using a valve or the like. It may be configured. In addition, in a vehicle equipped with the in-wheel motor drive device IWM, when the regenerative brake and the friction brake 8 by the in-wheel motor drive device IWM are used at the time of deceleration, the in-wheel motor drive device and the friction brake 8 are coordinated to control slip. The rate may be controlled. This control can also be applied to the front-wheel drive vehicle that can control the drive torque independently on the left and right.

  As mentioned above, although the form for implementing this invention based on embodiment was demonstrated, embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Vehicle 2, 3 ... Wheel 4 ... Motor 5 ... Wheel speed sensor 8 ... Friction brake 10 ... Host controller 11 ... Inverter device 12 ... Slip control device 13a ... Accelerator operating means 13b ... Brake operating means 14 ... Longitudinal acceleration sensor (front / rear) Acceleration detection means)
DESCRIPTION OF SYMBOLS 15 ... Vehicle speed detection means 16 ... Slip ratio calculation means 17 ... Slip ratio control means 18 ... Slip ratio limit value change means 19 ... Pitching vibration detection means 20 ... Band pass filter IWM ... In-wheel motor drive device

Claims (3)

Slip ratio calculating means for calculating a slip ratio using wheel rotational speed and vehicle speed, and slip ratio control means for controlling the slip ratio so that the calculated slip ratio does not exceed the slip ratio limit value And a slip control device comprising a slip rate limit value changing means capable of changing the magnitude of the slip rate limit value,
Pitching vibration detecting means for detecting pitching vibration of the vehicle body is provided, and the slip ratio limit value changing means is configured to detect the pitching vibration when the slip ratio control by the slip ratio control means is executed for one or more wheels. When detecting the pitching vibration of the vehicle body, the absolute value of the slip ratio limit value of the front wheel during acceleration and the rear wheel slip ratio during deceleration is reduced for at least one of the wheels for which slip ratio control is being executed. so, the slip rate limit value changing means, characterized that you back in accordance with a decrease in the operation amount of the accelerator operating means or the brake operating means, gradually predetermined value to increase the absolute value of the reduced slip rate limit Slip control device . The slip control device according to claim 1 , further comprising a bandpass filter having a characteristic of passing a frequency component in the vicinity of the pitching natural frequency of the vehicle body with respect to the longitudinal acceleration signal of the vehicle body detected by the longitudinal acceleration detection unit, The pitching vibration detection means is a slip control device that determines whether or not pitching vibration is generated from the longitudinal acceleration filtered by the bandpass filter. 3. The slip control device according to claim 2 , wherein the slip ratio limit value changing means calculates an absolute value of the reduced slip ratio limit value according to a decrease in amplitude of longitudinal acceleration filtered by the bandpass filter. Slip control device that gradually raises to a predetermined value.

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