JP2009214678A - Vehicle body attitude control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicle body attitude control device suitably operable under all travel conditions, by properly determining which of a measured value and an estimate value of a state variable such as the roll moment or lateral acceleration is ought to be preferentially adopted in response to a travel state. <P>SOLUTION: The state variable such as the roll moment or the lateral acceleration to be used, is determined as a weighted means weighted in response to the size of a friction coefficient of a road surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vehicle body posture control device that can be used for various types of suspension devices including those equipped with variable damping force dampers or actuators.

  In order to control the posture of the vehicle, it is necessary to detect the force or acceleration that causes the change in the posture of the vehicle without delay, operate the variable suspension element of the suspension device, and control the change in the posture of the vehicle. As a method for obtaining a force or acceleration that causes a change in the posture of the vehicle, a method of actually measuring with a sensor or a method of estimating from a state variable of the vehicle is known. The method of actually measuring with a sensor can accurately detect the force or acceleration that causes the problem, but there is a problem of being affected by noise, and the noise may hinder suitable control. On the other hand, in the method of estimating from the state variables of the vehicle, an estimated value greatly deviating from the actual value may be given depending on the setting of the parameters of the vehicle model to be used and the operating conditions of the vehicle.

Patent Document 1 discloses an active roll control that controls an actuator to suppress a roll of a vehicle body, and does not reflect a turning state of a vehicle with respect to a roll moment due to road surface unevenness. Therefore, it is disclosed that roll control is not performed. In that case, it is mentioned that the active roll control is executed based on the sum of the actual roll moment, which is an actual measurement value, and the estimated roll moment, which is an estimated value, weighted. It is not disclosed whether to perform the correct processing.
JP 2006-256539 A

Patent Document 2 discloses a technique for changing the estimated lateral acceleration map in accordance with the road surface state. However, it is still an estimated value, and in order to cope with all road surface conditions, a large number of maps are required, and either the system is complicated or the control accuracy is low. There must be.
JP 02-306812

  As described above, the inventor of the present application uses the measured value or estimated value when the measured value or estimated value of the vehicle state variable such as roll moment and lateral acceleration is used when controlling the attitude of the vehicle. Focusing on the merits and demerits of each, the knowledge that the optimal attitude control would be possible by preferentially adopting one of them depending on the running state of the vehicle was obtained.

  In view of such problems of the prior art and the inventor's knowledge, the main object of the present invention is to prioritize either the measured value or estimated value of a state variable such as roll moment or lateral acceleration depending on the running state. It is an object of the present invention to provide a vehicle body attitude control device that appropriately determines whether or not it should be employed and can be suitably operated under all traveling conditions.

  A second object of the present invention is to provide a vehicle body posture control apparatus that minimizes the influence of noise of a sensor for detecting an actual value of a state variable and that exhibits good responsiveness.

  According to the present invention, such an object is achieved by a variable suspension element provided between each wheel and the vehicle body, means for detecting a predetermined state variable of the vehicle, and the variable suspension element based on the state variable. A control unit for controlling the vehicle, a real state variable sensor for detecting the state variable, an estimated state variable calculating means for estimating the state variable based on a motion state of the vehicle, and the vehicle A motion parameter determination means for obtaining a motion parameter of the motion parameter, and the state variable as a weighted average value of the estimated state variable and the actual state variable determined according to the motion parameter determined by the motion parameter determination means This is achieved by providing a vehicle body attitude control device characterized in that it is determined. In this case, the state variable may be selected from the lateral acceleration, the longitudinal acceleration, and the yaw rate, and the motion parameter is selected from the road friction coefficient and the degree of unevenness of the road surface. Good.

  According to the inventor's experiment, when the road surface friction coefficient is relatively large, the noise of the state variable sensor such as the lateral acceleration sensor tends to be high, and when the road surface friction coefficient is relatively small, the noise of the state variable sensor is low. It has been found that Conversely, when the road surface friction coefficient is relatively large, the accuracy of state variables such as estimated lateral acceleration tends to increase, and when the road surface friction coefficient is relatively small, the accuracy of estimated state variables may tend to decrease. Has been found. The degree of unevenness on the road surface has the same effect as the degree of the road surface friction coefficient. Therefore, as the road surface friction coefficient increases, the weight of the real state variable such as the actual lateral acceleration in the weighted average value is increased so that the maximum value is always obtained regardless of the size of the road surface friction coefficient. Control accuracy can be ensured.

  The preferred embodiment of the present invention comprises, in particular, a vehicle body posture control apparatus for performing vehicle roll control, in which the state variable includes lateral acceleration and the motion parameter includes a road surface friction coefficient.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  FIG. 1 is a diagram schematically showing a vehicle suspension system to which the present invention is applied. A suspension system S for suspending each wheel W of a four-wheeled vehicle includes a suspension arm 6 that supports the wheel W so as to be movable up and down with respect to the vehicle body 1 via a knuckle 3, and a suspension arm 6 between the suspension arm 6 and the vehicle body 1. And a damper 4 disposed between the suspension arm 6 and the vehicle body 1 in parallel with the coil spring 2. The damper 4 is of a type that generates a load (damping force) corresponding to the moving speed when the piston moves inside the cylinder filled with oil. In this embodiment, for example, the MRF fluid Is used, and a control signal from the electronic control unit ECU is appropriately applied to the actuator 5 to change the damping characteristic, thereby performing the required vehicle body posture control.

  As shown in FIG. 2, the electronic control unit ECU that controls the operation of the actuator 5 includes a sprung acceleration sensor 13 that detects the sprung acceleration, a damper displacement sensor 14 that detects the displacement (stroke) of the damper 4, and the vehicle. A signal from the longitudinal acceleration sensor 16 for detecting the longitudinal acceleration is supplied.

  The electronic control unit ECU includes a skyhook riding comfort control unit 31, a roll posture control unit 32, a pitch posture control unit 33, and an unsprung control unit 35. The sprung acceleration output from the sprung acceleration sensor 13 is integrated by the integrating means 21 to become a sprung vertical speed and is input to the skyhook riding comfort control unit 31. The damper displacement output from the damper displacement sensor 14 is directly input to the unsprung control unit 35, differentiated by the differentiating means 22 to become a damper speed, and input to the skyhook riding comfort control unit 31 and the unsprung control unit 35. . The longitudinal acceleration output by the longitudinal acceleration sensor 16 is differentiated by the differentiating means 24 to obtain a longitudinal acceleration differential value, which is input to the pitch attitude control unit 33.

The vehicle body attitude control device further includes a lateral acceleration sensor 15, a road surface friction coefficient estimation unit 41, a front wheel steering angle sensor 42, a vehicle speed sensor 43, and a yaw rate sensor 44. The road surface friction coefficient estimating unit 41 may be of a known type as disclosed in Patent Documents 3 and 4, and the electronic control unit ECU may have such a function.
JP-A-6-3257 JP-A-9-281030

  The electronic control unit ECU further includes a lateral acceleration estimation unit 45 that estimates lateral acceleration from the outputs of the front wheel steering angle sensor 42 and the vehicle speed sensor 43. The actual lateral acceleration signal obtained from the lateral acceleration sensor 15 and the estimated lateral acceleration signal obtained from the lateral acceleration estimation unit 45 are supplied to the weighted average calculation unit 47, and both signals are referred to the output of the road surface friction coefficient estimation unit 41. A weighted average, that is, a weighted average is performed. FIG. 4 shows a weighting coefficient when performing such weighted average. That is, when the weight of the estimated lateral acceleration is w (a value between 0 and 1) and the estimated lateral acceleration and the actual lateral acceleration are Ae and Am, respectively, the weighted average combined lateral acceleration is w · Ae + ( 1-w) · Am.

  In the illustrated embodiment, the weight of the estimated lateral acceleration is continuously changed according to the road surface friction coefficient. However, when the road surface friction coefficient is a predetermined value or less, the actual lateral acceleration is adopted, and the road surface friction coefficient is predetermined. Alternatively, the lateral acceleration may be determined alternatively so that the estimated lateral acceleration is adopted when the value is exceeded. In order to avoid a sudden change in the behavior of the vehicle when the lateral acceleration is changed in this way, it is conceivable to provide hysteresis for the threshold value when changing the vehicle or to gradually change the time.

  The output of the damper displacement sensor 14 is differentiated by the differentiating means 22 and converted into a damper speed, and the damper speed is further supplied to the roll attitude controller 32 and the pitch attitude controller 33.

The combined lateral acceleration obtained from the weighted average computing unit 47 is differentiated by the differentiating means 23 through the filter 48 and converted into a lateral acceleration change rate, and is input to the roll posture control unit 32, and (proportional constant) × (lateral) The roll control target load (target damping force to be generated in the damper 4 for performing roll control) is calculated from the acceleration differential value). At that time, a vehicle speed signal obtained from the vehicle speed sensor 43 and a yaw rate signal obtained from the yaw rate sensor 44 through the filter 46 are also supplied to the roll attitude control unit 32. Thus, by adding the yaw rate correction term to the roll control, it is possible to improve the rising response of the roll control signal particularly in the low speed region. For a method for considering the yaw rate when calculating the roll control target load, see Patent Document 5. Further, by referring to the damper speed obtained by differentiating the damper displacement by the differentiating means 22, the roll control current necessary for generating the roll control target load is retrieved from a predetermined map, and the obtained roll control current is obtained. Is output to the high-select means 26.
JP 2006-281876 A

  Similar to the calculation of the roll control current described above, the pitch posture control unit 33 receives the vehicle longitudinal acceleration signal from the longitudinal acceleration sensor 16 in order to suppress the nose up during sudden acceleration of the vehicle and the nose down during sudden braking. Is calculated from the longitudinal acceleration differential value obtained by differentiating with the differentiating means 24, and the pitch control target load (target damping force to be generated in the damper 4 to perform pitch control) is calculated, and based on the pitch control target load and the damper speed, The pitch control current is retrieved from a predetermined map, and the obtained pitch control current is output to the high select means 26.

  In addition to the roll control current and the pitch control current, a sky hook control current (target current for performing the sky hook control) from the sky hook riding comfort control unit 31 is also input to the high select means 26. The high selection means 26 outputs the larger one of the roll control current, the pitch control current, and the skyhook control current. Then, the high select value output from the high select means 26 and the unsprung control current output from the unsprung control section 35 (target current for performing unsprung control) are added by the adding means 27, and based on the added value. Thus, the operation of the actuator 5 of the damper 4 is controlled.

  Thus, since any one of the roll control current, pitch control current, and skyhook control current is selected by the high select means 26 and output to the actuator 5, the roll control current, pitch control current, and skyhook control current are output. While any one of the control currents is being selected, if any different control current increases beyond that, then such a control current will be selected. Therefore, in any case, since the high-select current output from the high-select means 26 at the time of switching does not change suddenly and discontinuously, the operation of the actuator 5 of the damper 4 is avoided from giving the driver a sense of incongruity. .

  In Skyhook control, even if the control gain is changed, only the vibration transmissibility in the vicinity of 1 Hz which is the sprung resonance frequency is changed, and the vibration transmissibility in the vicinity of 10 Hz which is the unsprung resonance frequency cannot be controlled. There is. The unsprung control unit 35 is provided to solve this problem, and pays attention to the product of the damper speed and the damper displacement as an index for grasping and controlling the vibration in the unsprung resonance region. The unsprung control current is calculated by x (damper speed) x (damper displacement), and this unsprung control current is added to the high select current output from the high select means 26 in the adding means 27. As a result, it is possible to suppress vibration in the unsprung resonance region in the vicinity of 10 Hz independently of the skyhook control, particularly when the damper speed and the damper displacement are large.

  Thus, according to the present embodiment, a vehicle body attitude control device that always ensures the highest control accuracy regardless of the road surface condition and minimizes the influence of noise is provided. In addition, when the road surface friction coefficient changes, the distribution ratio between the estimated lateral acceleration and the actual lateral acceleration can be made appropriate and continuously changed, so that a sense of incongruity at the time of switching and a deviation from the actual signal can be reduced. Deterioration of comfort can be prevented. FIG. 4 is a graph comparing temporal changes in the combined lateral acceleration and the target damping force when the weighting in the weighted average of the combined lateral acceleration is changed. 4A shows an output waveform of the lateral acceleration sensor 15, and FIG. 4B shows a temporal change of the target damping force when this data is used as it is. Since the sensor output includes a considerable amount of noise, the target damping force also changes drastically. That is, the control operation amount tends to increase, the deviation increases, and the current consumption of the actuator increases. FIG. 4C shows a waveform of the combined lateral acceleration when a weight of 0.1 is applied to the actual lateral acceleration and a weight of 0.9 is applied to the estimated lateral acceleration. FIG. 4D shows a case where this data is used. Shows the change over time of the target damping force. Compared to FIGS. 4A and 4B, the temporal change in the waveform of the combined lateral acceleration and the target damping force is relatively gradual. Therefore, the control operation amount can be reduced, the deviation is suppressed, and the current consumption of the actuator is reduced.

  Although the embodiments of the present invention have been described above, various design changes can be made without departing from the scope of the present invention.

It is a diagram showing a model of a vehicle suspension device. It is a block diagram of the control system of the vehicle body posture control apparatus based on this invention. It is a graph which shows the relationship with the road surface friction coefficient of the weight of the actual lateral acceleration in the weighted average for calculating a synthetic lateral acceleration. 6 is a graph comparing the time variation of the lateral acceleration employed in the vehicle body attitude control device of the present invention and the target damping force obtained thereby with the case where the output of the lateral acceleration sensor is used as it is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Car body 2 Spring 3 Knuckle 4 Damper 5 Actuator 6 Suspension arm 14 Damper displacement sensor 16 Longitudinal acceleration sensor 15 Lateral acceleration sensor 21 Integration means 22-24 Differentiation means 26 High selection means 32 Roll attitude control part 33 Pitch attitude control part 41 Road surface friction Coefficient estimation unit 42 Front wheel steering angle sensor 43 Vehicle speed sensor 45 Lateral acceleration estimation unit 47 Weighted average calculation unit S Suspension device W Wheel

Claims (6)

Variable suspension elements provided between each wheel and the vehicle body,
Means for detecting a predetermined state variable of the vehicle;
A vehicle body attitude control device having a control unit for controlling the variable suspension element based on the state variable,
A real state variable sensor for detecting the state variable;
Estimated state variable calculating means for estimating the state variable based on the motion state of the vehicle;
Motion parameter determining means for determining a motion parameter of the vehicle,
The vehicle body posture control device, wherein the state variable is determined as a weighted average value of the estimated state variable and the actual state variable determined according to the motion parameter determined by the motion parameter determination means.   The vehicle body posture control device according to claim 1, wherein the state variable is selected from a lateral acceleration, a longitudinal acceleration, and a yaw rate.   2. The vehicle body attitude control device according to claim 1, wherein the motion parameter is selected from a road surface friction coefficient and a degree of road surface unevenness.   The vehicle body posture control apparatus according to claim 1, wherein the state variable includes a lateral acceleration, and the motion parameter includes a road surface friction coefficient.   The vehicle body attitude control device according to claim 4, wherein the control unit performs roll control of the vehicle.   6. The vehicle body attitude control device according to claim 5, wherein the weight of the actual lateral acceleration in the weighted average value is increased as the road surface friction coefficient increases.

Images