JP4600381B2 - Vehicle wheel torque estimation device and vibration suppression control device - Google Patents

Description

  The present invention relates to a device for estimating wheel torque during travel (acting on a road surface) of a vehicle such as an automobile, and a vibration suppression control device for a vehicle using the estimated wheel torque value.

  In some of the vehicle travel control, motion control, and braking / driving force control, torque that acts between the wheels and the ground road surface while the vehicle is traveling for the purpose of properly controlling the vehicle driving force. (Hereinafter, simply referred to as “wheel torque” in this specification) is referred to as a parameter. For example, on the basis of a so-called sprung / unsprung vibration motion model of the vehicle body, the vehicle body control that controls the drive output of the engine or other drive device to suppress the pitch / bounce vibration of the vehicle body while the vehicle is running is performed. In vibration control, the wheel torque that the driving wheel actually acts on the road surface is used as an input parameter for feedback for suppressing disturbance in the control (see, for example, Patent Documents 1 and 2). . Also, in various controls such as TRC, ABS, and VSC, wheel torque is referred to in order to refer to the road surface reaction force in the wheel or to inspect the running performance of the vehicle (for example, (See Patent Documents 3 and 4).

The value of the wheel torque while the vehicle is running may be such that a wheel torque sensor, a wheel six component force meter, etc. are provided on the wheel and the generated torque can be detected directly. Due to the problem in terms of cost or cost, it is not mounted on a normal vehicle except for a test vehicle (Patent Document 4). Therefore, in various types of vehicle control as described above, an estimated value of wheel torque based on other easily detectable parameters such as wheel speed is used (Patent Documents 1 to 3). 2), the wheel torque is expressed as a torque reaction force estimated value or a road surface disturbance estimated value.
JP 2004-168148 A JP 2006-69472 A JP 11-37872 A JP-A-2005-69897

  In the running, motion or braking / driving force control of various vehicles as described above, when the wheel torque is not directly detected but is obtained by estimation using parameters such as wheel speed, wheels or tires are used. Depending on the operating state, the estimation accuracy may deteriorate, and this may cause the vehicle control to fail. For example, in the case where the wheel torque is estimated based on the detected value of the wheel speed, the estimation accuracy may be deteriorated if the wheel (drive wheel during driving) is in a slip state. In addition, many wheel speed sensors used in ordinary vehicles detect the rotational speed of the wheel, but the direction of rotation (that is, whether the vehicle is moving forward or backward relative to the traveling direction of the vehicle) In the control process, it is possible to erroneously use the direction of the estimated wheel torque. If the estimated value or direction of the wheel torque deviates from the actual value or direction of the wheel torque generated on the wheel, for example, the drive output is controlled as described above to control the pitch or bounce vibration. In the control for performing the above, there may be a case where a good vibration damping effect cannot be obtained or the vibration is amplified. However, in a conventional wheel torque estimation device, a vehicle vibration suppression control device that uses an estimated value of wheel torque as a parameter, or another vehicle running, motion, or braking / driving force control device, the estimation of wheel torque is not possible. The case where it does not perform well is not considered much.

  Thus, one of the main objects of the present invention is an apparatus or means for estimating wheel torque referred to in various vehicle running, motion, braking / driving force control, etc. When it is not possible to perform well, it is necessary to provide an apparatus or means for generating an estimated value of the wheel torque in consideration of the fact.

  Another object of the present invention is an apparatus for controlling vibration during vehicle running by controlling the driving force of the vehicle based on the wheel torque estimated value obtained by the wheel torque estimating device or means as described above. If the estimation of the wheel torque cannot be performed satisfactorily, an apparatus that uses the estimated value of the wheel torque in consideration of that fact is provided.

  According to the present invention, in brief, in vehicle running, motion or braking / driving force control, in which the estimated value of the wheel torque is used without using a torque sensor or the like that actually measures the wheel torque. The wheel torque is configured to correct the estimated wheel torque when the estimated value or direction of the wheel torque deviates from that actually acting on the wheel due to various factors. An estimation device and a vehicle vibration suppression control device using the estimated wheel torque value corrected in this way are provided.

  According to one aspect of the present invention, an apparatus for estimating a wheel torque acting between a vehicle wheel and a road surface is a torque estimation method for estimating a wheel torque estimated value generated at a contact point between the wheel and the road surface. And a slip state amount calculating unit for calculating a wheel slip state amount indicating a slip state of the wheel, and a wheel torque estimated value so that an absolute value of the wheel torque estimated value is decreased as a degree of slip represented by the wheel slip state amount is increased. And a wheel torque correction unit that corrects. In this specification, the “slip state of the wheel” means that the force that the wheel acts on the road surface while the vehicle is running is the grip limit (maximum friction) of the wheel (or tire). This means that the wheel “slides” on the road surface beyond the circle), and “the degree of slip” corresponds to the magnitude of the frictional force between the wheel surface and the road surface when slipping. (When relative slip occurs between the wheel surface and the road surface, the wheel surface, road surface, and slip increase as the frictional force at that time decreases.) The estimated wheel torque value is usually calculated on the assumption that the wheel grips the road surface, depending on the estimation method. However, when the wheel is in a slipping state, such a premise is lost and the accuracy of the estimated wheel torque value is deteriorated. Therefore, in the wheel torque estimation device of the present invention, the “wheel slip state amount” indicating the slip state of the wheel is calculated, and the greater the degree of slip represented by the wheel slip state amount, the more the wheel torque estimated value becomes The absolute value is corrected to be small. The estimated wheel torque value is based on the assumption that the wheel is gripping the road surface.If the wheel slips, the force or torque transmitted from the road surface to the wheel is reduced. It is expected that the estimated wheel torque value is closer to the actual value by correcting the estimated wheel torque value at a certain time.

  It should be understood that the “wheel slip state amount” representing the slip state of the wheel may be an arbitrary amount as long as it is an index that can detect the transition of the wheel from the grip state to the slip state. For example, a wheel slip ratio or a slip ratio may be used as a wheel slip state quantity (in these terms, the term “slip” is used. Regardless of whether or not the vehicle is gripping the road surface, this means a deviation between the vehicle speed and the wheel speed (the value obtained by multiplying the wheel rotation speed by the wheel radius). This is different from “slip” in the sense that the wheel “slides” on the road surface.) Preferably, for example, when the vehicle is driven, the wheel speed of the driving wheel of the vehicle and the wheel speed of the driven wheel of the vehicle are May be used as the wheel slip state quantity (during vehicle acceleration, the wheel speed of the driven wheel will be a value corresponding to the vehicle speed, regardless of whether or not the drive wheel is in the grip state. The wheel speed of the wheel is the vehicle speed when the drive wheel slips. Corresponding not.).

  In the wheel torque estimation device described above, the estimation of the wheel torque estimated value may be performed by an arbitrary method, but typically, as described in an embodiment of the present invention described later, This may be done based on the wheel speed (or the rotational speed of the wheel) detected by the wheel speed sensor of the wheel. In this case, when the vehicle is driven, the estimated wheel torque value may be calculated as a function of the differential value of the wheel speed of the drive wheel.

  In another aspect of the present invention, the wheel torque estimating device includes a torque estimating unit that estimates a wheel torque estimated value based on a wheel speed detected by a wheel speed sensor of the wheel, and the vehicle is moving backward. And a wheel torque correction unit that corrects the estimated wheel torque value to a negative value. As briefly mentioned above, when estimating the wheel torque estimation value based on the wheel speed given by the wheel speed sensor, most of the wheel speed sensors mounted on a normal mass-produced vehicle are partly high-end. The rotation direction of the wheel cannot be detected except for a sensor. Therefore, in the control using the wheel speed torque as one of the inputs, if the estimated wheel torque value estimated from the wheel speed sensor is used as it is, the wheel torque is calculated when the wheel is moving backward, such as when the vehicle is moving backward. It can happen that the contribution of is reflected in the opposite direction. Therefore, as one aspect of the correction of the estimated wheel torque value of the present invention, as described above, when the wheel is moving backward (the vehicle reverse or wheel reverse is caused by the shift lever or switch of the vehicle transmission). The wheel torque estimated value may be corrected to a negative value (with the magnitude unchanged). It should be understood that the correction for making the estimated wheel torque value negative may be performed together with the correction based on the wheel slip state quantity.

  In the present invention, the wheel torque estimated value that is appropriately corrected based on the slip state amount of the wheel as described above or corrected when the vehicle is moving backward is controlled by controlling the driving force of the vehicle. It is advantageously used in a vehicle vibration suppression control device for suppressing pitch or bounce vibration. Therefore, in one aspect of the present invention, the vibration damping control device for a vehicle acquires a wheel torque estimated value that acts on a wheel generated at a contact point between the vehicle wheel and a road surface. An acquisition unit, and a driving force control unit that controls the driving force of the vehicle so as to suppress the pitch or bounce vibration amplitude based on the estimated wheel torque value, and further acquires a wheel slip state amount indicating a slip state of the wheel. A slip state quantity acquisition unit is provided, and as the degree of slip represented by the wheel slip state quantity increases, the absolute value of the wheel torque estimation value or the control amount of the driving force is corrected to be smaller, and the driving force of the vehicle is controlled with reference to this. Is done. In another aspect of the present invention, in the vehicle vibration damping control apparatus having the wheel torque estimated value acquisition unit and the driving force control unit as described above, the wheel torque is detected by a wheel speed sensor of the wheel. When the vehicle speed is estimated, the wheel torque estimated value acquired by the wheel torque estimated value acquisition unit is corrected to a negative value when the vehicle is moving backward, and the vehicle is driven with reference to this. Force is controlled. In the above vibration suppression control device, an estimated wheel torque value generated by a device different from the vibration suppression control device may be used. A torque estimation device or means for generating a wheel torque estimated value may be provided, and the estimated value generated there may be corrected.

  A vehicle vibration suppression control device that suppresses vehicle pitch or bounce vibration by controlling the driving force of the vehicle described above is, for example, a wheel as described in more detail in the embodiments of the present invention described later. Assuming a dynamic motion model of the sprung vibration or unsprung vibration of the vehicle body during running, where the torque is an external force that generates pitch or bounce vibration in the vehicle body, and based on the motion model, It may be a device that adjusts the wheel torque, that is, the driving force of the vehicle so as to reduce the amplitude of the unsprung vibration. The estimated wheel torque value is input as feedback or disturbance in the vibration suppression control. At that time, if the wheel is in a slip state or is rotating backward, it is the same as in the case of the wheel torque estimating device described above. It will be corrected by this process. As will be understood from the above description of the wheel torque estimation device, the wheel used in the vibration suppression control device is corrected by correcting the wheel torque estimation value when the wheel is in a slipping state or when it is rotating backward. The estimated torque value is expected to be closer to the actual wheel torque value with respect to its magnitude or direction. Therefore, even if the estimation of the wheel torque cannot be performed satisfactorily, good vibration suppression control is possible. Expected to be achieved. It should be noted that the technical idea of correcting the estimated wheel torque value of the present invention can be used for a vibration damping control device using a wheel torque estimated value other than the vibration damping control device as described above. It should be understood that it belongs to the scope.

  By the way, in the vibration damping control apparatus by the driving force control of the vehicle in the above aspect of the present invention, the estimated wheel torque value is estimated based on the wheel speed detected by the wheel speed sensor of the driving wheel of the vehicle. When the wheel speed sensor is abnormal, the estimated wheel torque value may be corrected to a value estimated based on the rotational speed of the output shaft of the vehicle drive device. In principle, the wheel speed corresponds to the rotational speed of the output shaft of the vehicle drive device (if the wheel speed changes due to a certain factor, the “rotational speed” of the output shaft of the drive device also changes. If the wheel speed sensor is abnormal and the wheel speed cannot be detected accurately, the output shaft of the drive device is calculated using the relationship between the wheel speed and the rotational speed of the output shaft of the vehicle drive device. A wheel torque estimated value is acquired on the basis of the rotational speed of the wheel, and thus vibration damping control can be executed even when the wheel speed sensor is abnormal.

  In the above vibration damping control device, if it is determined that the vibration damping control cannot be satisfactorily executed even after correcting the wheel torque estimated value, the control of the driving force based on the wheel torque estimated value is stopped. You may come to do. In addition, the effect of the vibration suppression control is for improving the steering stability and ride comfort of the vehicle, and the vibration suppression control is performed even when the wheel slips, when the vehicle reverses or when the wheel speed sensor is abnormal. Even when it is determined that it is not necessary, the control of the driving force based on the estimated wheel torque value may be stopped. In particular, when the wheel is in a slip state, the control of the driving force based on the estimated wheel torque value may be stopped when the slip degree represented by the wheel slip state amount is greater than a predetermined degree. According to such a configuration, occurrence of vibration amplification due to input of a torque value that is incompatible with the vibration suppression control is suppressed.

  In general, according to the present invention, even when the estimation of the wheel torque cannot be performed satisfactorily, an estimated value close to the actual wheel torque value is obtained, and therefore various control of the vehicle is executed better than before. Is expected to be. In particular, in a vibration suppression control apparatus for pitch / bounce vibration of a vehicle, if the wheel torque value that is fed back is different from the actual value, the vibration may be amplified rather than suppressed. As a result, according to the present invention, the possibility of occurrence of vibration amplification by control is reduced. Further, it should be understood as an advantage of the present invention that, in the past, in order to obtain a wheel torque value even when the wheel is in a slipping state or when it is being rotated backward, a device such as a torque sensor is provided on the wheel. However, according to the present invention, the value of the wheel torque used in the vehicle running, motion, braking / driving force or damping control can be obtained without using such a sensor device. It is a point that can be used. Since it is not necessary to separately provide a torque sensor device for obtaining the wheel torque value, the cost for the vehicle or the control device or the labor required for the design is reduced.

  Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

  In the following description of the embodiment, the present invention is described as estimating wheel torque used as parameters for various controls such as vibration control of the vehicle. It should be understood that the value can be used for other applications and still be within the scope of the present invention.

  The present invention will now be described in detail with reference to a few preferred embodiments with reference to the accompanying drawings. In the figure, the same reference numerals indicate the same parts.

Configuration of Device FIG. 1A schematically shows an automobile on which a preferred embodiment of a wheel torque estimating device or a vibration damping control device of the present invention is mounted. In the figure, the vehicle 10 having the left and right front wheels 12FL and 12FR and the left and right rear wheels 12RL and 12RR generates a driving force on the rear wheels according to the depression of the accelerator pedal 14 by the driver in a normal manner. A driving device 20 is mounted. In the illustrated example, the driving device 20 is configured such that driving torque or rotational driving force is transmitted from the engine 22 to the rear wheels 12RL and 12RR via the torque converter 24, the automatic transmission 26, the differential gear device 28, and the like. Although configured, an electric type in which an electric motor is used instead of the engine 22 or a hybrid type driving device having both an engine and an electric motor may be used. Further, the vehicle may be a four-wheel drive vehicle in which driving force is transmitted to the front wheels. Although not shown for the sake of simplicity, the vehicle 10 is provided with a braking system device that generates a braking force on each wheel and a steering device for controlling the steering angle of the front wheels or the front and rear wheels, as in a normal vehicle. It is done.

  The operation of the driving device 20 is controlled by the electronic control device 50. The electronic control unit 50 may include a microcomputer having a CPU, a ROM, a RAM, and an input / output port device, which are connected to each other by a bidirectional common bus, and a driving circuit. The electronic control device 50 includes a signal representing a wheel speed Vwi (i = FL, FR, RL, RR) from a wheel speed sensor 30i (i = FL, FR, RL, RR) mounted on each wheel, a vehicle Signals such as the engine rotation speed Er, the transmission rotation speed Dr, and the accelerator pedal depression amount θa are input from sensors provided in the respective sections. In addition to the above, it should be understood that various detection signals for obtaining various parameters necessary for various controls to be executed in the vehicle of the present embodiment may be input. As schematically shown in more detail in FIG. 1B, the electronic control unit 50 operates the drive control unit 50a for controlling the operation of the drive unit 20 and the operation of the braking unit (not shown). You may comprise from the braking control apparatus 50b to control. In the braking control device, electric signals in the form of pulses are generated from the wheel speed sensors 30FR, FL, RR, RL of each wheel, which are sequentially generated every time the wheel rotates by a predetermined amount, and the sequential control is performed. The rotational speed of the wheel is calculated by measuring the time interval of the arrival of the pulse signal input to, and the wheel speed value is calculated by multiplying this by the wheel radius. (The calculation from the wheel rotation speed to the wheel speed may be performed by the drive control apparatus 50a. In this case, the wheel rotation speed is calculated from the braking control apparatus 50b. To the drive control device 50a). In addition, for the purpose described in more detail below, the wheel speed invalid state information indicating that when the wheel speed value cannot be acquired, in addition to the wheel speed value, from the braking control apparatus 50b to the drive control apparatus 50a. The wheel slip state amount indicating whether or not the driving wheel is in a slip state or the information indicating whether or not various controls for controlling the slip ratio of the wheel such as VSC, ABS, or TRC are performed is transmitted.

  In the drive control device 50a, the target output torque (driver required torque) of the drive device requested by the driver based on the accelerator pedal depression amount θa is determined based on the driving request from the driver. However, in the drive control device of the present invention, the driver request torque is corrected to execute the pitch / bounce vibration damping control of the vehicle body by the drive force control, and the control command corresponding to the corrected request torque is executed. Is applied to the drive device 20. In this pitch / bounce vibration damping control, (1) calculation of the estimated wheel torque of the driving wheel by the force acting between the driving wheel and the road surface, and (2) pitch based on the vehicle vibration model. / Calculation of bounce vibration state quantity, (3) Calculation of correction amount of wheel torque for suppressing pitch / bounce vibration state quantity, and correction of required torque based on this. The estimated wheel torque value (1) is calculated based on the wheel speed value of the driving wheel (or the wheel rotational speed of the driving wheel) received from the braking control device 50b. The wheel torque estimation device of the present invention is realized in the processing operation of (1), and the vibration suppression control device of the present invention is realized in the processing operation of (1)-(3). That should be understood.

FIG. 2 (A) shows an example of a driving force control system that performs pitch / bounce vibration damping control of a vehicle body, when the driving device is activated based on the driving request of the driver and the wheel torque fluctuates. In the vehicle body 10 as described above, bounce vibration in the vertical direction (z direction) of the center of gravity Cg of the vehicle body and pitch vibration in the pitch direction (θ direction) around the center of gravity of the vehicle body can occur. Further, when an external force or torque (disturbance) acts on the wheels from the road surface while the vehicle is running, the disturbance is transmitted to the vehicle, and vibrations in the bounce direction and the pitch direction may also occur in the vehicle body. Therefore, in the illustrated embodiment, a motion model of the pitch / bounce vibration of the vehicle body is constructed, in which the driver's required torque (value converted into wheel torque) and the current wheel torque (of Vehicle body displacement z and θ and their change rates dz / dt and dθ / dt, that is, state variables of vehicle body vibration, are calculated, and the state variables obtained from the model converge to zero. In other words, the drive torque of the drive device is adjusted so that the pitch / bounce vibration is suppressed (the driver-requested torque is corrected).

  FIG. 2B schematically shows the configuration of the driving force control in the embodiment of the present invention in the form of a control block (note that the operation of each control block (except for C0 and C3) It is executed by either the drive control device 50a or the braking control device 50b of the electronic control device 50). Referring to FIG. 2B, in the driving force control according to the embodiment of the present invention, generally speaking, a driving controller that gives a driving request of the driver to the vehicle, and a pitch / bounce vibration of the vehicle body is suppressed. And a vibration suppression controller for correcting the driving request of the driver. In the drive controller, after the driver's drive request, that is, the accelerator pedal depression amount (C0) is converted into the driver request torque in a normal manner (C1), the driver request torque is Then, it is converted into a control command for the drive device (C2) and transmitted to the drive device (C3). [The control command includes a target throttle opening for a gasoline engine, a target fuel injection amount for a diesel engine, a target current amount for a motor, and the like. ]

  On the other hand, the vibration damping controller includes a feedforward control part and a feedback control part. The feedforward control portion has a so-called optimum regulator configuration, and here, as described below, a value obtained by converting the driver required torque of C1 into wheel torque (driver required wheel torque Tw0) is the vehicle body torque. An input to the motion model portion (C4) of the pitch bounce vibration, and in the motion model portion (C4), the response of the state variable of the vehicle body to the input torque is calculated, and the driver request wheel that converges the state variable to the minimum A torque correction amount is calculated (C5). In the feedback control portion, the wheel torque estimator (C6) calculates a wheel torque estimated value Tw as described later, and the wheel torque estimated value is calculated based on the FB gain (driver in the driving model). After being multiplied by a gain for adjusting the balance of contribution between the requested wheel torque Tw0 and the estimated wheel torque value Tw), the disturbance input is added to the driver requested torque and input to the motion model portion (C4). Thereby, the correction amount of the driver request wheel torque with respect to the disturbance is also calculated. The correction amount of the driver required wheel torque of C5 is converted into the unit of the required torque of the driving device and transmitted to the adder (C1a), and thus the driver required torque is set so that pitch bounce vibration does not occur. After the correction, it is converted into a control command (C2) and given to the driving device (C3).

Principle of Vibration Suppression Control In the vibration suppression control in the embodiment of the present invention, as already mentioned, first, assuming the dynamic motion model in the bounce direction and the pitch direction of the vehicle body, the driver requested wheel A state equation of state variables in the bounce direction and the pitch direction is input with the torque Tw0 and the estimated wheel torque value Tw (disturbance) as inputs. From this state equation, the input (torque value) for converging the bounce and pitch state variables to 0 is determined using the theory of the optimal regulator, and the driver required torque is corrected based on the obtained torque value. Is done.

ここに於いて、Ｌｆ、Ｌｒは、それぞれ、重心から前輪軸及び後輪軸までの距離であり、ｒは、車輪半径であり、ｈは、重心の路面からの高さである。なお、式（１ａ）に於いて、第１、第２項は、前輪軸から、第３、４項は、後輪軸からの力の成分であり、式（１ｂ）に於いて、第１項は、前輪軸から、第２項は、後輪軸からの力のモーメント成分である。式（１ｂ）に於ける第３項は、駆動輪に於いて発生している車輪トルクＴ（＝Ｔｗ０＋Ｔｗ）が車体の重心周りに与える力のモーメント成分である。 As a dynamic motion model in the bounce direction and pitch direction of the vehicle body, for example, as shown in FIG. 3A, the vehicle body is regarded as a rigid body S of mass M and moment of inertia I, and the rigid body S has an elastic modulus kf. And a front wheel suspension having a damping rate cf, and a rear wheel suspension having an elastic modulus kr and a damping rate cr (car body sprung vibration model). In this case, the motion equation in the bounce direction and the motion equation in the pitch direction of the center of gravity of the vehicle body are expressed as the following Equation 1.

Here, Lf and Lr are distances from the center of gravity to the front wheel shaft and the rear wheel shaft, respectively, r is a wheel radius, and h is a height of the center of gravity from the road surface. In Equation (1a), the first and second terms are components of force from the front wheel shaft, and the third and fourth terms are components of force from the rear wheel shaft. In Equation (1b), the first term Is the moment component of the force from the front wheel shaft, and the second term is the force from the rear wheel shaft. The third term in the equation (1b) is a moment component of the force that the wheel torque T (= Tw0 + Tw) generated in the drive wheel gives around the center of gravity of the vehicle body.

であり、行列Ａの各要素a1-a4及びb1-b4は、それぞれ、式（１ａ）、（１ｂ）にｚ、θ、ｄｚ／ｄｔ、ｄθ／ｄｔの係数をまとめることにより与えられ、
a1=-(kf+kr)/M、a2=-(cf+cr)/M、
a3=-(kf・Lf-kr・Lr)/M、a4=-(cf・Lf-cr・Lr)/M、
b1=-(Lf・kf-Lr・kr)/I、b2=-(Lf・cf-Lr・cr)/I、
b3=-(Lf²・kf+Lr²・kr)/I、b4=-(Lf²・cf+Lr²・cr)/I
である。また、ｕ(t)は、
ｕ(t)＝Ｔ
であり、状態方程式（２ａ）にて表されるシステムの入力である。従って、式（１ｂ）より、行列Ｂの要素p1は、
p1=h/(I・r)
である。 The above formulas (1a) and (1b) are expressed as (linear) as shown in the following formula (2a) with the vehicle body displacements z and θ and their change rates dz / dt and dθ / dt as the state variable vector X (t). It can be rewritten in the form of a system state equation.
dX (t) / dt = A · X (t) + B · u (t) (2a)
Here, X (t), A, and B are respectively

And each element a1-a4 and b1-b4 of the matrix A is given by combining the coefficients of z, θ, dz / dt, dθ / dt in the equations (1a) and (1b), respectively.
a1 =-(kf + kr) / M, a2 =-(cf + cr) / M,
a3 =-(kf ・ Lf-kr ・ Lr) / M, a4 =-(cf ・ Lf-cr ・ Lr) / M,
b1 =-(Lf ・ kf-Lr ・ kr) / I, b2 =-(Lf ・ cf-Lr ・ cr) / I,
b3 =-(Lf ²・ kf + Lr ²・ kr) / I, b4 =-(Lf ²・ cf + Lr ²・ cr) / I
It is. U (t) is
u (t) = T
And is an input of the system represented by the state equation (2a). Therefore, from equation (1b), the element p1 of the matrix B is
p1 = h / (I ・ r)
It is.

In the equation of state (2a)
u (t) = − K · X (t) (2b)
Then, the equation of state (2a) is
dX (t) / dt = (A-BK) .X (t) (2c)
It becomes. Accordingly, the initial value X ₀ (t) of X (t) is set as X ₀ (t) = (0,0,0,0) (assuming that there is no vibration before torque is input). ), When the differential equation (2c) of the state variable vector X (t) is solved, the magnitude of X (t), that is, the displacement rate in the bounce direction and the pitch direction and its time change rate, is converged to zero. When the gain K is determined, the torque value u (t) for suppressing the bounce / pitch vibration is determined.

The gain K can be determined by using a so-called optimal regulator theory. According to this theory, a quadratic evaluation function J = 1/2 · ∫ (X ^T QX + u ^T Ru) dt (3a)
(Integral range is 0 to ∞)
When the value of is the minimum, the matrix K that minimizes the evaluation function J by the stable convergence of X (t) in the state equation (2a) is
K = R ⁻¹・ B ^T・ P
It is known to be given by Where P is the Riccati equation
^{-dP / dt = A T P +} PA + Q-PBR -1 B T P
Is the solution. The Riccati equation can be solved by any method known in the field of linear systems, which determines the gain K.

などと置いて、式（３ａ）に於いて、状態ベクトルの成分うち、特定のもの、例えば、ｄｚ／ｄｔ、ｄθ／ｄｔ、のノルム（大きさ）をその他の成分、例えば、ｚ、θ、のノルムより大きく設定すると、ノルムを大きく設定された成分が相対的に、より安定的に収束されることとなる。また、Ｑの成分の値を大きくすると、過渡特性重視、即ち、状態ベクトルの値が速やかに安定値に収束し、Ｒの値を大きくすると、消費エネルギーが低減される。 Note that Q and R in the evaluation function J and Riccati equation are respectively a semi-positive definite symmetric matrix and a positive definite symmetric matrix, which are weight matrices of the evaluation function J determined by the system designer. For example, in the case of the motion model considered here, Q and R are

In Equation (3a), a specific one of the components of the state vector, for example, the norm (magnitude) of dz / dt, dθ / dt, and the other components, for example, z, θ, If the value is set to be larger than the norm, components having a larger norm are converged relatively stably. Further, when the value of the Q component is increased, the transient characteristics are emphasized, that is, the value of the state vector quickly converges to a stable value, and when the value of R is increased, the energy consumption is reduced.

  In actual vibration suppression control, as shown in the block diagram of FIG. 2B, in the motion model C4, by solving the differential equation of equation (2a) using the torque input value, A state variable vector X (t) is calculated. Next, at C5, the value U () obtained by multiplying the state vector X (t), which is the output of the motion model C4, by the gain K determined to converge the state variable vector X (t) to 0 or the minimum value as described above. t) is subtracted from the driver request torque (converted to the torque of the driving device) from the driver request torque (for the calculation of the motion model C4, it is also fed back to the torque input value of the motion model C4). (State feedback). The system represented by equations (1a) and (1b) is a resonant system, and for any input, the value of the state variable vector is substantially the natural frequency of the system. It becomes only the ingredient of. Therefore, by configuring so that U (t) (converted value) is subtracted from the driver required torque, the component of the natural frequency of the system, that is, pitch bounce vibration in the vehicle body, of the driver required torque. Will be corrected and the pitch bounce vibration in the car body will be suppressed. (If the system's natural frequency component disappears in the required torque given by the driver, it will be input to the drive unit. Among the required torque commands, the component of the natural frequency of the system is only -U (t), and the vibration due to Tw (disturbance) converges.

ここに於いて、xf、xrは、前輪、後輪のばね下変位量であり、mf、mrは、前輪、後輪のばね下の質量である。式（４ａ）−（４ｂ）は、ｚ、θ、xf、xrとその時間微分値を状態変数ベクトルとして、図３（Ａ）の場合と同様に、式（２ａ）の如き状態方程式を構成し（ただし、行列Ａは、８行８列、行列Ｂは、８行１列となる。）最適レギュレータの理論に従って、状態変数ベクトルの大きさを０に収束させるゲイン行列Ｋを決定することができる。実際の制振制御は、図３（Ａ）の場合と同様である。
As a dynamic motion model in the bounce direction and pitch direction of the vehicle body, for example, as shown in FIG. 3 (B), in addition to the configuration of FIG. 3 (A), the spring elasticity of the front and rear tires is considered. The model (car spring top / bottom vibration model) may be employed. Assuming that the tires for the front wheels and the rear wheels have the elastic moduli ktf and ktr, respectively, the equation of motion in the bounce direction and the equation of motion in the pitch direction of the center of gravity of the vehicle body are as understood from FIG. The following equation 4 is expressed.

Here, xf and xr are unsprung displacement amounts of the front and rear wheels, and mf and mr are unsprung masses of the front and rear wheels. Equations (4a)-(4b) form a state equation as shown in Equation (2a), similarly to the case of FIG. 3A, with z, θ, xf, xr and their time differential values as state variable vectors. (However, the matrix a is 8 rows and 8 columns, matrix B,. a 8 rows and one column) can be according to the optimal regulator theory, determines the gain matrix K for converging the size of the state variable vector to 0 . Actual vibration suppression control is the same as in the case of FIG.

Calculation of estimated wheel torque In the feedback control part of the vibration damping controller shown in FIG. 2 (B), the wheel torque input as disturbance to the feedforward control part is ideally provided with a torque sensor for each wheel. However, as described above, since it is difficult to provide a torque sensor for each wheel of a normal vehicle, a wheel torque estimator (from other detectable values in a running vehicle ( The estimated wheel torque estimated in C6) is used.

The wheel torque estimated value Tw is typically obtained by using a wheel rotational speed ω obtained from a wheel speed sensor of a driving wheel or a time derivative of a wheel speed value r · ω,
Tw = M · r ² · dω / dt (5)
Can be estimated. Here, M is the mass of the vehicle, and r is the wheel radius. [If the sum of the driving forces generated at the contact points of the driving wheels on the road surface is equal to the overall driving force MG (G is acceleration) of the vehicle, the wheel torque Tw is
Tw = M · G · r (5a)
Given in The acceleration G of the vehicle is obtained from the differential value of the wheel speed r · ω,
G = r · dω / dt (5b)
Therefore, the wheel torque is estimated as shown in Equation (5). ]

  In the estimation of the wheel torque as described above, when the driving wheel tire grips the road surface to generate the driving force while the vehicle is traveling forward, the formula (5) is actually generated. It is expected to roughly match the wheel torque. However, when the road surface reaction force on the driving wheel increases and exceeds the maximum friction circle, the tire enters a slip state (the tire slips), and the equation (5b) does not hold. The accuracy of the estimated value will deteriorate. In addition, with the exception of some high-function sensors, the magnitude of the rotational speed of the wheel can be detected from the signal from the wheel speed sensor normally mounted on the wheel, but whether the wheel is rotating forward or backward. You cannot get information about what you are doing. Therefore, the vibration suppression controller is normally configured on the assumption that the vehicle is moving forward. However, when the vehicle is moving backward, the above estimated value is directly input to the vibration suppression controller. If this occurs, the wheel torque is input to the vibration suppression controller in the opposite direction from the actual one. Furthermore, even when the wheel speed cannot be accurately detected, such as when the wheel speed sensor is broken, the accuracy of the estimated wheel torque value of Equation (5) also deteriorates. Therefore, in the present invention, in the situation where the estimation accuracy of the wheel torque estimated value by the wheel torque estimator (C6) is deteriorated as described above, the wheel torque estimated value is corrected as follows.

Correction of wheel torque estimate 1
When the tire of the driving wheel is slipped, the value of the acceleration G calculated by time differentiation of the wheel speed in the equation (5b) becomes larger than the actual acceleration, and therefore the wheel estimated from the wheel speed. The estimated torque value is expected to be larger than the actual value. Therefore, when the tire of the drive wheel enters the slip state, the estimated wheel torque value is corrected downward according to an arbitrary index (wheel slip state amount) indicating the slip state of the tire. In this case, the estimated wheel torque value of equation (5) is, for example,
Tw = κslip · M · r ² · dω / dt (6)
May be. κslip is a quantity given as a function of the wheel slip state quantity, and is given using a map as shown in FIG. What is important in FIG. 4 is that when the tire is in the grip state, κ slip = 1 is set, the tire is in the slip state, and the wheel spins completely (the vehicle is not subjected to wheel torque). Is that κslip = 0.

  The wheel slip state quantity that is an index representing the degree of slip of the wheel tire may be, for example, a ratio of the average value of the wheel speeds of the left and right driven wheels to the average value of the wheel speeds of the left and right drive wheels. In this case, when the driving wheel is in the slip state, the wheel speed of the driving wheel relatively increases, and as a result, the ratio of the wheel speed, that is, the wheel slip state amount is reduced. Further, as the wheel slip state quantity, a tire slip ratio and a slip ratio may be used. When the wheel slip state quantity is defined as a value that increases as the degree of slip increases, the wheel slip state quantity increases and the value of κslip is reduced. As shown in the example of FIG. If the slip state quantity is defined as a value that decreases as the degree of slip increases, the wheel slip state quantity should be reduced and the value of κslip should be reduced. It should be understood that it belongs to the scope.

The correction of the estimated wheel torque as in equation (6) by κslip may be made by monitoring the value of the wheel slip state quantity, but the wheel slip when the following conditions (a)-(c) are satisfied: It may be executed based on the value of the state quantity.
(A) When VSC, TRC, or ABS control is executed (when these controls are executed, it is usually when the tire transitions from the grip state to the slip state).
(B) The difference between the average value of the wheel speeds of the left and right driven wheels and the average value of the wheel speeds of the left and right drive wheels exceeds a predetermined amount for a predetermined period.
(C) When the time differential value of the wheel speed exceeds a predetermined threshold for a predetermined time. Note that the predetermined threshold may be set to an acceleration that cannot be generated by the vehicle.

  The slip state amount calculation unit for calculating the wheel slip state amount and the wheel torque correction unit for correction by κslip are realized by the operation of the CPU and other components in the drive control device 50a (FIG. 1B).

Correction of wheel torque estimate 2
As described above, the normal wheel speed sensor cannot detect the direction of the wheel, but the estimated value given by the formula (5) in the wheel torque estimator indicates that the wheel is rotating forward. Calculated as a premise. Therefore, when the wheel is moving backward, the estimated value is opposite in sign to the actual value. Therefore, the wheel torque estimator of the present invention detects when the wheel from information other than the wheel speed sensor is the rear rolling, in that time, equation (5) Tw = -M · r 2 · dω / dt ... (7)
And an estimated wheel torque value is output.

When turning a wheel, for example,
(D) If it is an automatic vehicle, the shift lever of the transmission is in the R range,
(E) If it is a manual vehicle, it may be detected when the reverse switch is ON. If the wheel speed sensor mounted on the wheel can detect the rotation direction of the wheel, Formula (5) may be used with the wheel rotation speed ω set to a negative value during the reverse rotation of the wheel. .

Correction of wheel torque estimate 3
If an abnormality occurs in the wheel speed sensor and the detection accuracy of the wheel speed deteriorates, the accuracy of the estimated wheel torque according to the equation (5) also deteriorates. The speed may be calculated from the rotational speed of the drive device. When the rotational speed Ne of the output shaft of the engine or motor of the driving device is used, the wheel rotational speed of the driving wheel is
ωe = Ne × transmission (transmission) gear ratio × diff (differential gear) gear ratio (8)
Given by. Moreover, when using the rotational speed No of the output shaft of the transmission,
ωo = No x differential gear ratio (9)
Given by. Then, the estimated value of the wheel rotational speed ω of the drive wheel in Expression (8) or (9) is substituted into Expression (5), and the estimated wheel torque value is calculated.

The calculation of the estimated wheel torque value according to the equation (8) or (9) may be executed, for example, when any of the following conditions (f)-(i) is satisfied.
(F) When an abnormality occurs in the signal of the wheel speed sensor and it is determined that the state is “abnormal”.
(G) When an abnormality of the wheel speed sensor is determined in another control device such as ABS, VSC, TRC or the braking control device 50b (FIG. 1B).
(H) When the difference between the wheel speed calculated from the signal from the wheel speed sensor and the wheel speed calculated from the rotational speed of the output shaft of the drive device by equation (8) exceeds a predetermined value for a predetermined period. .
(I) When the difference between the wheel speed calculated from the signal from the wheel speed sensor and the wheel speed calculated from the rotational speed of the output shaft of the transmission according to equation (9) exceeds a predetermined value for a predetermined period. .

It should be understood that the wheel torque estimator (C6) may be configured such that all of the corrections of the wheel torque estimation values described above can be realized. In such a case, the wheel torque estimate in equation (5) will be modified as follows.
Tw = κslip · κsign · M · r ² · dω / dt (10)
In this case, κslip is normally κslip = 1, and is given by the map of FIG. 4 when any of the above conditions (a)-(c) is satisfied. Also, κsign is normally κsign = 1, and when the above condition (d) or (e) is satisfied, κsign = -1. Further, ω is usually a wheel rotation speed obtained from a signal from a wheel speed sensor, and when the condition (f)-(i) is satisfied, ωe or ωo given by the equation (8) or (9) is set. Replaced. Therefore, for example, when the conditions (a), (d), and (f) are satisfied, the estimated wheel torque value is
Tw = −κslip · M · r ² · dωe / dt
It will be.

Correction of Vibration Suppression Control If it is determined that the accuracy of the wheel torque estimated value is not improved even after executing the above-described correction 1-3 of the wheel torque estimated value, the wheel torque estimated value is input to the motion model C4. May be blocked. The purpose of the vibration suppression control of the present invention is primarily to improve the driving stability and ride comfort of the vehicle, and the wheel slip state in which the wheel torque estimation value correction 1-3 is executed. The situation such as when the vehicle is moving backwards or when the wheel speed sensor is abnormal is a special situation in the traveling of the vehicle, and in some cases, control for stabilizing the traveling of another vehicle or ensuring safety Therefore, the input of the wheel torque estimated value to the motion model C4 may be cut off. Therefore, in the control configuration of FIG. 2B, when the conditions (a) to (i) are satisfied, the input of the estimated wheel torque value to the motion model C4 may be cut off. . Further, as for the case where the wheel is in a slip state, when the degree of slip represented by the wheel slip state quantity is larger than a predetermined degree, for example, in the map of FIG. At this time, as indicated by a broken line, κslip = 0 may be set so that the wheel torque estimation value input to the motion model C4 is substantially cut off. Further, when the condition (a)-(i) is satisfied, U (t) = 0 may be set to stop the execution of the vibration damping control (stop the correction of the driver request torque).

  Although the above description has been made in relation to the embodiment of the present invention, many modifications and changes can be easily made by those skilled in the art, and the present invention is limited to the embodiment exemplified above. It will be apparent that the invention is not limited and applies to various devices without departing from the inventive concept.

  For example, in the above embodiment, the wheel torque estimator (estimator) is incorporated in the vibration damping controller, but the wheel torque estimator may be configured as an independent unit. In the wheel torque estimator of the above embodiment, the case of estimating the wheel torque of the driving wheel at the time of driving is described, but the case of estimating the wheel torque of the driving wheel and the driven wheel at the time of braking is supported. The wheel torque estimation value of each wheel estimated from the wheel speed to be corrected may be corrected according to the amount of wheel slip state and whether the wheel is reversed, and such a case is also within the scope of the present invention. Belongs.

  Moreover, although the wheel torque estimated value in the above embodiment is estimated from the wheel speed, the wheel torque estimated value is estimated from parameters other than the wheel speed, and the wheel slip state or The present invention may be applied to a case where the estimated value and the actual value may deviate when the wheel is reversed.

  Furthermore, the vibration suppression control in the above embodiment is a vibration suppression control using the theory of an optimal regulator assuming a sprung or sprung / unsprung motion model as a motion model. As long as the estimated value of wheel torque is used, it is also applied to those using a motion model other than those introduced here, or those that are controlled by a control method other than the optimal regulator. Are also within the scope of the present invention.

FIG. 1A shows a schematic diagram of an automobile in which a preferred embodiment of a wheel torque estimating device and a vibration damping control device according to the present invention is realized. FIG. 1B is a more detailed schematic diagram of the internal configuration of the electronic control device of FIG. 1A. FIG. 2A is a diagram for explaining the state variables of the vehicle body vibration that are suppressed in the vibration damping control device that is one of the preferred embodiments of the present invention. FIG. 2B is a diagram showing the configuration of the vibration damping control in the preferred embodiment of the present invention in the form of a control block diagram. FIG. 3 is a diagram for explaining a mechanical motion model of vehicle body vibration assumed in the vibration damping control device according to the preferred embodiment of the present invention. FIG. 3A shows a case where a sprung vibration model is used, and FIG. 3B shows a case where a sprung / unsprung vibration model is used. FIG. 4 is a graph showing a map of the correction coefficient κslip for the estimated wheel torque value that changes according to the wheel slip state quantity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Car body 12FL, FR, RL, RR ... Wheel 14 ... Accelerator pedal 30FL, FR, RL, RR ... Wheel speed sensor 50 ... Electronic control unit

Claims (10)

  A device for estimating wheel torque acting between a wheel of a vehicle and a road surface, a torque estimating unit for estimating a wheel torque estimated value acting on a wheel generated at a contact point between the wheel and the road surface; A slip state amount calculation unit that calculates a wheel slip state amount indicating a slip state of the wheel, and the wheel torque so that the absolute value of the estimated value of the wheel torque decreases as the degree of slip represented by the wheel slip state amount increases. And a wheel torque correction unit for correcting the estimated value.   The apparatus according to claim 1, wherein the wheel torque estimated value is calculated as a negative value when the wheel rotates backward.   2. The apparatus of claim 1, wherein the wheel slip state quantity is a ratio of a wheel speed of a driving wheel of the vehicle and a wheel speed of a driven wheel of the vehicle.   2. The apparatus according to claim 1, wherein the estimated wheel torque value is a function of a differential value of a wheel speed detected by a wheel speed sensor of a driving wheel of the vehicle. A vehicle vibration control device that suppresses pitch or bounce vibration of the vehicle by controlling the driving force of the vehicle, the wheel torque acting on a wheel generated at a contact point between the wheel of the vehicle and a road surface A wheel torque estimated value acquisition unit that acquires an estimated value; and a driving force control unit that controls the driving force of the vehicle so as to suppress the pitch or bounce vibration amplitude based on the wheel torque estimated value; A slip state amount acquisition unit that acquires a wheel slip state amount indicating a slip state of a wheel is provided, and the absolute value of the estimated wheel torque value is corrected to be smaller as the degree of slip represented by the wheel slip state amount is larger. A vehicle vibration control device. 6. The apparatus according to claim 5 , wherein the estimated wheel torque value is a negative value when the wheel is rotating backward. 6. The apparatus of claim 5 , wherein the wheel slip state quantity is a ratio of a wheel speed of a driving wheel of the vehicle and a wheel speed of a driven wheel of the vehicle. 6. The apparatus according to claim 5 , wherein the estimated wheel torque value is a function of a differential value of a wheel speed detected by a wheel speed sensor of a driving wheel of the vehicle. 6. The apparatus according to claim 5 , wherein the estimated wheel torque value is a value estimated based on a wheel speed detected by a wheel speed sensor of a driving wheel of the vehicle, and when the wheel speed sensor is abnormal, the wheel The torque estimated value is a value estimated based on the rotational speed of the output shaft of the drive device of the vehicle. 6. The apparatus according to claim 5 , wherein the estimated wheel torque value is a value estimated based on a wheel speed detected by a wheel speed sensor of a driving wheel of the vehicle, and when the wheel speed sensor is abnormal, the wheel An apparatus characterized by stopping control of the driving force based on a torque estimation value.

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