JP7624381B2 - Vehicle attitude control device - Google Patents

Description

This disclosure relates to a vehicle body attitude control device suitable for use in vehicles such as four-wheeled automobiles.

Patent Document 1 discloses that a target pitch rate is calculated so that the vehicle body tilts forward downward in response to the roll rate, and the damping force of the suspension device is controlled in response to the target pitch rate.

JP 2012-46172 A

Patent Document 1 discloses a vehicle body attitude control device that is capable of roll control in addition to pitch control for a downward forward motion. Here, a pitch moment may occur in the vehicle body due to roll control. In contrast, the vehicle body attitude control device described in Patent Document 1 does not take into account the variable range of the damping force. For this reason, there is a risk that pitch control may not necessarily be appropriate for the vehicle.

The objective of one embodiment of the present invention is to provide a vehicle attitude control device that is capable of appropriate pitch control even when roll control is being performed.

One embodiment of the present invention is a vehicle body attitude control device that controls the attitude of the vehicle body by controlling the force generated by a force generating mechanism provided between the wheels and the vehicle body of the vehicle, and is characterized by having a roll command value calculation means that calculates a roll command value for controlling the roll state of the vehicle body from the road surface condition, a pitch moment prediction means that predicts the pitch moment generated in the vehicle body based on the roll command value by the roll command value calculation means, a target pitch rate calculation means that calculates a target pitch rate so that the degree to which the vehicle body dives increases according to the magnitude of the roll rate of the vehicle body, and a pitch rate correction means that corrects the calculated value by the target pitch rate calculation means in consideration of the predicted value by the pitch moment prediction means.

According to one embodiment of the present invention, appropriate pitch control can be performed even when roll control is being performed.

1 is a perspective view showing a four-wheeled automobile to which a vehicle body attitude control device according to a first to third embodiments of the present invention is applied; 1 is a control block diagram showing a vehicle body attitude control device according to a first embodiment; FIG. 3 is a control block diagram showing a correction target pitch moment calculation unit in FIG. 2 . FIG. 4 is a characteristic diagram showing the relationship between the steering angle, roll angle, pitch angle, roll rate, pitch rate, front downward pitch correction amount, and current command value during cornering. FIG. 11 is a control block diagram showing a vehicle body attitude control device according to a second embodiment. FIG. 6 is a control block diagram showing a current correction value calculation unit in FIG. 5 . FIG. 11 is a control block diagram showing a vehicle body attitude control device according to a third embodiment.

The vehicle body attitude control device according to an embodiment of the present invention will be described in detail below with reference to the attached drawings, taking as an example a case where it is applied to a four-wheeled vehicle.

Here, Figs. 1 to 4 show a first embodiment of the present invention. As shown in Fig. 1, a vehicle body 1 constitutes the body of a vehicle. For example, left and right front wheels 2 and left and right rear wheels 3 (only one of which is shown) are provided on the underside of the vehicle body 1.

The front-wheel suspension device 4 is installed between the left and right front wheels 2 and the vehicle body 1. Each suspension device 4 is composed of left and right suspension springs 5 (hereafter referred to as springs 5) and left and right damping force adjustable shock absorbers 6 (hereafter referred to as variable damping dampers 6) installed in parallel with each spring 5 between the left and right front wheels 2 and the vehicle body 1.

The rear wheel suspension device 7 is installed between the left and right rear wheels 3 and the vehicle body 1. Each suspension device 7 is composed of left and right suspension springs 8 (hereafter referred to as springs 8) and left and right damping force adjustable shock absorbers 9 (hereafter referred to as variable damping dampers 9) installed in parallel with each spring 8 between the left and right rear wheels 3 and the vehicle body 1.

Here, the variable damping force dampers 6, 9 of each suspension device 4, 7 are configured using hydraulic shock absorbers with adjustable damping force. The variable damping force dampers 6, 9 are provided between the wheels (front wheels 2, rear wheels 3) and the vehicle body 1, and are force generating mechanisms that generate a force (damping force). The variable damping force dampers 6, 9 are provided with actuators (not shown) consisting of a damping force adjustment valve, a solenoid, etc., to continuously adjust the damping force characteristics from hard characteristics to soft characteristics. The actuator for adjusting the damping force does not necessarily have to be configured to continuously change the damping force characteristics, and may be configured to intermittently adjust the damping force characteristics in two or three or more stages. The variable damping force dampers 6, 9 may be pneumatic dampers or electromagnetic dampers as long as they can switch the damping force.

The steering angle sensor 10 is provided on the vehicle body 1. The steering angle sensor 10 detects the steering angle (corresponding to the front wheel steering angle δf described below) when the driver of the vehicle steers the steering wheel during cornering, etc., and outputs the detection signal to the controller 21.

The vehicle speed sensor 11 is provided on the vehicle body 1. The vehicle speed sensor 11 detects, for example, the vehicle's traveling speed (corresponding to vehicle speed V described below) and outputs the detection signal to the controller 21.

The controller 21 is a control means constituted by a microcomputer or the like. The input side of the controller 21 is connected to the steering angle sensor 10, the vehicle speed sensor 11, etc., and the output side is connected to actuators (not shown) of the FR damper (variable damping force damper 6 for the right front wheel), FL damper (variable damping force damper 6 for the left front wheel), RR damper (variable damping force damper 9 for the right rear wheel), and RL damper (variable damping force damper 9 for the left rear wheel), etc.

As shown in FIG. 2, the controller 21 includes a vehicle model unit 22, target damping force calculation units 25 and 26 for roll suppression, an absolute value calculation unit 29, a target pitch moment calculation unit 30, damper command value calculation units 40, 41, 42 and 43 for each wheel, and a correction target pitch moment calculation unit 51.

In this case, the controller 21 estimates (calculates) the lateral acceleration in the vehicle model unit 22 based on the steering angle signal detected by the steering angle sensor 10 and the vehicle speed signal detected by the vehicle speed sensor 11. The controller 21 calculates the target pitch moment based on the estimated lateral acceleration (estimated lateral acceleration). The controller 21 performs feedforward control (FF control) of the damping force variable dampers 6, 9 according to the target pitch moment. In this way, the controller 21 is able to achieve an improved roll sensation.

The vehicle model unit 22 estimates the lateral acceleration αy using a vehicle model shown in the following formula 1 based on the steering angle (front wheel steering angle δf) and the vehicle speed V. Here, the lateral acceleration αy can be calculated by formula 1, assuming a linear model of the vehicle and ignoring dynamic characteristics, where V is the vehicle speed [m/s], A is the stability factor [ ^S2 / ^m2 ], δf is the front wheel steering angle [rad], and L is the wheelbase [m].

The phase adjustment filter 23 compensates for the dynamics from the steering angle input to the lateral acceleration and roll angle generation. The differentiation unit 24 differentiates the lateral acceleration to calculate the lateral jerk. At this time, the lateral acceleration almost coincides with the roll angle. The lateral jerk almost coincides with the roll rate. For this reason, the target damping force calculation units 25 and 26 in the next stage multiply the lateral jerk, which is correlated with the roll rate, by the Fr gain for the right front wheel and the Rr gain for the right rear wheel to obtain a target damping force for roll suppression. The target damping force calculation units 25 and 26 constitute a roll command value calculation means for calculating a roll command value for controlling the roll state of the vehicle body 1 from the lateral jerk (roll rate) as the road surface condition. At this time, the target damping force for roll suppression output by the target damping force calculation units 25 and 26 corresponds to the roll command value.

The sign reversal units 27 and 28 multiply the target damping force for roll suppression by -1 to reverse the target damping force for the left wheels (left front wheel, left rear wheel) from that for the right wheels. The relative speed estimation unit 44 estimates the relative speed of each wheel using the lateral jerk calculated by the differentiation unit 24.

The absolute value calculation unit 29 calculates the absolute value |u| of the lateral acceleration (roll angle). The target pitch moment calculation unit 30 (target pitch moment calculation means) multiplies the absolute value |u| of the lateral acceleration by the gain "Kroll2r" to calculate the target pitch moment Ma0. The absolute value calculation unit 29 and the target pitch moment calculation unit 30 constitute a target pitch rate calculation means that calculates a target pitch rate (target pitch moment Ma0) so that the degree to which the vehicle body 1 dives increases according to the magnitude of the roll rate of the vehicle body 1. Here, the reason why the target pitch moment Ma0 is calculated in proportion to the lateral acceleration is that the transfer function from the pitch rate to the pitch moment used in the first embodiment has a phase characteristic of -90 degrees when the steering input frequency is 1 Hz or less, which is the target frequency this time, so it is sufficient to be proportional to the roll angle obtained by integrating the roll rate, and since the roll angle is correlated with the lateral acceleration, it is sufficient to be proportional to the lateral acceleration.

The target pitch moment Ma0 is corrected by a correction target pitch moment calculation unit 51, which will be described later. The correction target pitch moment calculation unit 51 outputs a correction target pitch moment Ma1, which is a correction of the target pitch moment Ma0.

When the correction target pitch moment Ma1 is input, the equal distribution calculation unit 31 divides the correction target pitch moment Ma1 into four parts and distributes the target damping force to each wheel (i.e., the left and right front wheels 2 and rear wheels 3) accordingly. The next target damping force calculation units 32 and 33 calculate the target damping force of the right front wheel 2 and the left front wheel 2, which is the pitch generation part, by dividing the equally distributed moment (Ma1/4) by the distance lf to the center of gravity on the front wheel 2 side. In addition, the target damping force calculation units 34 and 35 calculate the target damping force of the right rear wheel 3 and the left rear wheel 3 by dividing the equally distributed moment (Ma1/4) by the distance lr to the center of gravity on the rear wheel 3 side.

The adder 36 adds the target damping force for roll suppression from the target damping force calculation unit 25 to the target damping force for pitch generation from the target damping force calculation unit 32, and calculates the target damping force after the addition as the target damping force for the right front wheel 2. The adder 37 adds the target damping force for roll suppression from the target damping force calculation unit 25 to the target damping force for pitch generation from the target damping force calculation unit 33, and calculates the target damping force after the addition as the target damping force for the left front wheel 2.

The pitch components are reversed between the front wheels 2 and the rear wheels 3. Therefore, the subtraction unit 38 subtracts the target damping force for roll suppression from the target damping force calculation unit 26 from the target damping force for pitch generation from the target damping force calculation unit 34, and calculates the target damping force after subtraction as the target damping force for the right rear wheel 3. The subtraction unit 39 subtracts the target damping force for roll suppression from the target damping force calculation unit 26 from the target damping force for pitch generation from the target damping force calculation unit 35, and calculates the target damping force after subtraction as the target damping force for the left rear wheel 3.

After calculating the target damping force for each wheel by adding or subtracting the target damping force calculated based on the roll suppression amount and the pitch generation amount, the damper command value calculation units 40, 41, 42, and 43 output the required current value based on the target damping force and the relative speed estimated by the relative speed estimation unit 44 using a damper characteristic map stored in advance. That is, the damper command value calculation units 40, 41, 42, and 43 calculate the damper command value to be output as a current value (current command value) to the actuator (not shown) of the FR damper (variable damping force damper 6 for the right front wheel 2), FL damper (variable damping force damper 6 for the left front wheel 2), RR damper (variable damping force damper 9 for the right rear wheel 3), and RL damper (variable damping force damper 9 for the left rear wheel 3).

The damping force variable dampers 6, 9 on each wheel (left and right front wheels 2, rear wheels 3) are controlled so that the damping force characteristics are continuously controlled between hard and soft, or variably controlled in multiple stages, according to the current value (damper command value) supplied to the actuator.

Next, the correction target pitch moment calculation unit 51 will be described in detail with reference to FIG. 3. The correction target pitch moment calculation unit 51 receives the target pitch moment Ma0 from the target pitch moment calculation unit 30 and the target damping forces from the target damping force calculation units 25 and 26. The correction target pitch moment calculation unit 51 corrects the target pitch moment Ma0 taking into account the moment generated by roll control, and outputs the correction target pitch moment Ma1. As shown in FIG. 3, the correction target pitch moment calculation unit 51 includes a pitch moment prediction unit 52 and a pitch rate correction unit 53.

The pitch moment prediction unit 52 constitutes a pitch moment prediction means for predicting the pitch moment generated in the vehicle body 1 based on the target damping force (roll command value) for roll suppression output by the target damping force calculation units 25, 26. The pitch moment prediction unit 52 includes doubling calculation units 52A, 52B, moment calculation units 52C, 52D, and a subtraction unit 52E. The doubling calculation units 52A, 52B double the target damping force by the target damping force calculation units 25, 26 to obtain a damping force for two wheels from the target damping forces for the front and rear wheels that can be generated by roll control. For this reason, the doubling calculation unit 52A doubles the target damping force for the front wheels. The doubling calculation unit 52B doubles the target damping force for the rear wheels.

The moment calculation unit 52C multiplies the damping force output from the doubling calculation unit 52A by the distance lf from the center of gravity to the front axle (front wheel 2). The moment calculation unit 52D multiplies the damping force output from the doubling calculation unit 52B by the distance lr from the center of gravity to the rear axle (rear wheel 3). In this way, the moment calculation units 52C and 52D calculate the moments of the front wheels 2 and rear wheels 3. The subtraction unit 52E subtracts the moment of the rear wheels 3 from the moment of the front wheels 2, and calculates the moment MaR generated by roll control from the difference between these.

The pitch rate correction unit 53 constitutes a pitch rate correction means that corrects the calculated value (target pitch moment Ma0) by the target pitch moment calculation unit 30, taking into account the predicted value (moment MaR) by the pitch moment prediction unit 52. The pitch rate correction unit 53 is composed of a subtractor. The pitch rate correction unit 53 subtracts the moment MaR generated by roll control from the target pitch moment Ma0. In other words, the pitch rate correction unit 53 calculates the difference between the target pitch moment Ma0 and the moment MaR, and calculates the corrective target pitch moment Ma1 from these differences.

The vehicle body attitude control device according to this embodiment has the configuration described above, and next, the attitude control process of the vehicle body 1 by the controller 21 will be described with reference to FIG. 4. FIG. 4 shows a time chart of the steering angle, roll angle, pitch angle, roll rate, pitch rate, front drop correction amount, and current command value during control. The dashed line in FIG. 4 shows the characteristics of a comparative example (equivalent to the conventional technology described in Patent Document 1, for example), and the solid line shows the characteristics of this embodiment.

When a vehicle approaches a corner on a road and must turn, the steering operation is performed in the following order, for example: straight ahead → transitional turn → steady turn → transitional turn → straight ahead. At this time, the driver of the vehicle operates the steering wheel to change the steering angle along the road.

When the vehicle is traveling straight, the steering angle is nearly zero and kept neutral, and when it reaches a transitional turn, the steering angle is increased by the required angle. When it reaches a steady turn, the steering angle is kept at a nearly constant angle to maintain the required angle, and when it reaches a transitional turn, an operation is performed to return the steering angle to neutral, and when it returns to traveling straight, it is kept neutral at nearly zero.

The lateral acceleration generated on the vehicle body 1 side changes in response to the steering angle, increasing or decreasing in a manner nearly proportional to the steering angle. The roll angle on the vehicle body 1 side also changes in response to the steering angle, increasing or decreasing in a manner nearly proportional to the steering angle.

In this embodiment and the comparative example, for example, the pitch angle is controlled to be low during steady turning, and then the pitch angle is controlled to be a negative value during the subsequent transient turning. For this reason, in this embodiment and the comparative example, a target pitch rate proportional to the roll rate is calculated, and the damping force characteristics of the damping force variable dampers 6, 9 provided on each wheel (left and right front wheels 2, rear wheels 3) are variably controlled to achieve this target pitch rate, thereby generating a pitch moment on the vehicle body 1.

In this way, by making the pitch rate and roll rate proportional when the vehicle is cornering, no shaking occurs in the rotation axis of the vehicle body 1, improving the steering feeling. Also, by calculating a target pitch rate according to the roll rate and controlling the vehicle body 1 to generate a pitch moment so as to achieve this target pitch rate, the roll rate and pitch rate are made proportional, and by inverting the target pitch rate according to the sign of the roll angle, the vehicle always pitches head-down, stabilizing the rotation axis of the vehicle body 1 and improving the roll feeling.

In the comparative example, the target pitch moment, which is the front-down pitch correction amount, is calculated without taking into account the pitch moment due to roll control. Therefore, as shown by the dashed line in FIG. 4, the front-down pitch correction amount is added to the control amount of roll control, and as a result, the command value may exceed the upper or lower limit of the variable damping force width generated by the damping force variable dampers 6 and 9. In this case, the comparative example may not be able to generate a damping force that exceeds the upper or lower limit of the variable damping force width. Also, since the comparative example does not take into account the pitch moment due to roll control, even if the command value is within the range of the variable damping force width, it may not be possible to execute appropriate pitch angle control according to the vehicle state. Therefore, the comparative example has a problem in that it may not be possible to control to the intended front-down pitch angle.

In contrast, in this embodiment, the front-down pitch correction amount is a corrective target pitch moment Ma1 obtained by correcting the target pitch moment by taking into account the pitch moment due to roll control. Therefore, as shown by the solid line in FIG. 4, in this embodiment, when the direction of the pitch moment due to roll control and the direction of the target pitch moment are the same, the command value can be reduced and the command value can be output within the range of the upper and lower limits of the damping force variable width generated by the damping force variable dampers 6 and 9. In addition, since the pitch moment due to roll control is taken into account in this embodiment, even when the direction of the pitch moment due to roll control and the direction of the target pitch moment differ, appropriate pitch angle control can be performed according to the vehicle state. As a result, in this embodiment, appropriate front-down pitch control can be realized even when roll control is being performed.

Thus, in this embodiment, the controller 21 has target damping force calculation units 25, 26 (roll command value calculation means) that calculate a roll command value (target damping force for roll suppression) for controlling the roll state of the vehicle body from the road surface condition, a pitch moment prediction unit 52 (pitch moment prediction means) that predicts the pitch moment generated in the vehicle body 1 based on the target damping force by the target damping force calculation units 25, 26, an absolute value calculation unit 29 and a target pitch moment calculation unit 30 (target pitch rate calculation means) that calculate a target pitch moment Ma0 (target pitch rate) so that the degree to which the vehicle body 1 dives increases according to the magnitude of the roll rate of the vehicle body 1, and a pitch rate correction unit 53 (pitch rate correction means) that corrects the target pitch moment Ma0 (calculated value) taking into account the moment MaR (predicted value) by the pitch moment prediction unit 52. Therefore, even when roll control is being performed, appropriate pitch control can be performed.

The target damping force calculation units 25, 26 also calculate a target damping force for roll control (roll control target damping force) as a roll command value, and the pitch moment prediction unit 52 predicts the moment MaR (pitch moment) generated in the vehicle body 1 based on the target damping force for roll control. At this time, the damping force variable dampers 6, 9 control these damping forces based on the target damping force for roll control. Therefore, the pitch moment prediction unit 52 can calculate the pitch moment generated by roll control based on the target damping force for roll control.

Next, Figures 1, 5, and 6 show a second embodiment of the present invention. The second embodiment is characterized in that the pitch moment prediction unit predicts the pitch moment generated in the vehicle body based on the command current supplied to the damping force variable damper. In the second embodiment, the same components as those in the first embodiment described above are given the same reference numerals, and their explanation will be omitted.

The controller 61 is a control means constituted by a microcomputer or the like. The input side of the controller 61 is connected to the steering angle sensor 10, the vehicle speed sensor 11, etc., and the output side is connected to actuators (not shown) of the FR damper (variable damping force damper 6 for the right front wheel), FL damper (variable damping force damper 6 for the left front wheel), RR damper (variable damping force damper 9 for the right rear wheel), and RL damper (variable damping force damper 9 for the left rear wheel), etc.

5, the damper command value calculation units 62, 63, 64, and 65 are configured in the same manner as the damper command value calculation units 40, 41, 42, and 43 according to the first embodiment. The damper command value calculation units 62, 63, 64, and 65 output the required current value from the damper characteristic map stored in advance based on the target damping force for roll suppression output by the target damping force calculation units 25 and 26 and the relative speed estimated by the relative speed estimation unit 44. That is, the damper command value calculation units 62, 63, 64, and 65 calculate the damper command value for roll suppression to be output to the actuators (not shown) of the FR damper (variable damping force damper 6 for the right front wheel 2), the FL damper (variable damping force damper 6 for the left front wheel 2), the RR damper (variable damping force damper 9 for the right rear wheel 3), and the RL damper (variable damping force damper 9 for the left rear wheel 3) as a current value (current command value). In addition, to reverse the target damping force for roll suppression for the left wheels (left front wheel, left rear wheel) from that for the right wheels, the target damping force multiplied by "-1" by the sign reversal units 27, 28 is input to the damper command value calculation units 63, 65.

The adders 66 and 67 calculate a total current command value by adding the current value for roll suppression from the damper command value calculators 62 and 63 and the current correction value from the current correction value calculator 81, which will be described later. That is, the adders 66 and 67 add the current correction value from the current correction value calculator 81 to the current command value for roll control. The current command value from the adders 66 and 67 is supplied to the actuators of the FR damper (the variable damping force damper 6 for the right front wheel 2) and the FL damper (the variable damping force damper 6 for the left front wheel 2) via the saturation processors 70 and 71. When the current command value exceeds the limit value (upper limit value or lower limit value) of the current that can be supplied to the actuator of the variable damping force damper 6, the saturation processors 70 and 71 limit the current command value to the limit value.

The adders 68 and 69 add the current value for roll suppression from the damper command value calculation units 64 and 65 and the current correction value from the current correction value calculation unit 81 described later to calculate a total current command value. That is, the adders 68 and 69 add the current correction value from the current correction value calculation unit 81 to the current command value for roll control. The current command values from the adders 68 and 69 are supplied to the actuators of the RR damper (the damping force variable damper 9 of the right rear wheel 3) and the RL damper (the damping force variable damper 9 of the left rear wheel 3) via the saturation processing units 72 and 73. When the current command value exceeds the limit value (upper limit value or lower limit value) of the current that can be supplied to the actuator of the damping force variable damper 9, the saturation processing units 72 and 73 limit the current command value to the limit value. In addition, the current command values output from the saturation processing units 70, 71, 72, and 73 are input to the current correction value calculation unit 81 via the delay unit 74. At this time, the current command value that has passed through the delay unit 74 is input to the current correction value calculation unit 81 as the current command FB value.

Next, the current correction value calculation unit 81 will be described in detail with reference to FIG. 6. The current correction value calculation unit 81 receives the target pitch moment from the target pitch moment calculation unit 30, the lateral acceleration (roll angle) from the phase adjustment filter 23, the relative speed of each wheel from the relative speed estimation unit 44, and the current command value (current command FB value) of each wheel from the delay unit 74. The current correction value calculation unit 81 calculates a current correction value based on the target pitch moment, the lateral acceleration (roll angle), the relative speed of each wheel, and the current command value (current command FB value) of each wheel. The current correction value calculation unit 81 includes a pitch moment prediction unit 83 and pitch rate correction units 84 and 85.

The front/rear wheel distribution unit 82 distributes the target pitch moment to the front wheel portion and the rear wheel portion. The front/rear wheel distribution unit 82, together with the absolute value calculation unit 29 and the target pitch moment calculation unit 30, constitutes a target pitch rate calculation means. The front/rear wheel distribution unit 82 includes a division unit 82A and target pitch moment calculation units 82B and 82C. The division unit 82A divides the target pitch moment by twice the wheelbase Iwb to calculate the front downward pitch target damping force for one wheel of the front downward pitch moment. The target pitch moment calculation unit 82B multiplies the front downward pitch target damping force by the distance lf from the front axle (front wheel 2) to the center of gravity to output the target pitch moment for the front wheel 2. The target pitch moment calculation unit 82C multiplies the front downward pitch target damping force by the distance lr from the rear axle (rear wheel 3) to the center of gravity to output the target pitch moment for the rear wheel 3.

The pitch moment prediction unit 83 constitutes a pitch moment prediction means for predicting the pitch moment generated in the vehicle body 1 based on the target damping force for roll suppression output by the target damping force calculation units 25, 26. At this time, the current command FB value for each wheel is set based on the target damping force for roll suppression. Therefore, the pitch moment prediction unit 83 estimates the pitch moment generated in the vehicle body 1 based on the current command FB value for each wheel, and outputs the estimated pitch moment.

The pitch moment prediction unit 83 includes a map 83A, a phase adjustment filter 83B, a lever ratio multiplication unit 83C, a sign reversal unit 83D, and an estimated pitch moment calculation unit 83E, 83F. The map 83A uses the current command FB value of each wheel and the relative speed of each wheel to calculate the damping force generated by the damping force variable dampers 6, 9 of each wheel. The phase adjustment filter 83B adjusts the phase from the current command to the generation of the damping force. The lever ratio multiplication unit 83C multiplies the damping force phase-adjusted by the phase adjustment filter 83B by the lever ratio to calculate the estimated damping force at the wheel position. Here, since the damping force of the rear wheel 3 is in the opposite direction to that of the front wheel 2, the sign reversal unit 83D multiplies the estimated damping force output from the lever ratio multiplication unit 83C by "-1". After that, the estimated pitch moment calculation unit 83E multiplies the estimated damping force by the distance lf from the front axle (front wheel 2) to the center of gravity to output the estimated pitch moment of the front wheel 2. The estimated pitch moment calculation unit 83F multiplies the estimated damping force by the distance lr from the rear axle (rear wheel 3) to the center of gravity, and outputs the estimated pitch moment of the rear wheel 3.

The pitch rate correction units 84 and 85 constitute pitch rate correction means that correct the calculated value (target pitch moment) by the target pitch moment calculation units 82B and 82C in consideration of the predicted value (estimated pitch moment) by the pitch moment prediction unit 52. The pitch rate correction units 84 and 85 are each composed of a subtractor. The pitch rate correction units 84 and 85 calculate the difference between the target pitch moment and the estimated pitch moment. The gain multiplication unit 86 multiplies the difference value output from the pitch rate correction unit 84 by the pitch moment FB control gain Kf and converts it into a current control command correction value for the front wheels 2. The gain multiplication unit 87 multiplies the difference value output from the pitch rate correction unit 85 by the pitch moment FB control gain Kr and converts it into a current control command correction value for the rear wheels 3.

Next, the current command correction value based on the front downward pitch moment is allocated to each wheel. For the front wheels 2, the damping force of the wheel on the inside of the turn (rebound side) is increased (+) and that of the wheel on the outside (compression side) is decreased (-). Conversely, for the rear wheels 3, the damping force of the wheel on the outside of the turn (compression side) is increased (+) and that of the wheel on the inside (rebound side) is decreased (-). In this way, the controller 61 achieves a front downward roll.

For this reason, the right turn current command calculation unit 90 multiplies the current command correction values for the left front wheel 2 and right rear wheel 3 by "-1" using the sign inversion units 90A and 90B. The gain multiplication units 90C and 90D multiply the current command correction values for the right front wheel 2 and right rear wheel 3, which are on the extension side, by gains Kif and Kir in order to match the compression/expansion ratio of the damping force. This absorbs the difference in damping force due to expansion and contraction relative to the current value.

Similarly, the left turn current command calculation unit 91 multiplies the current command correction value for the right front wheel 2 and the left rear wheel 3 by "-1" using the sign inversion units 91A and 91B. The gain multiplication units 91C and 91D multiply the current command correction value for the left front wheel 2 and the left rear wheel 3, which are on the extension side, by the gains Kif and Kir in order to match the compression/expansion ratio of the damping force. This absorbs the difference in damping force due to expansion and contraction relative to the current value.

The turning direction determination unit 93 determines the turning direction (left or right) based on the lateral acceleration (roll angle) that has passed through the vehicle filter 92, and outputs a turning direction signal. The command value switching unit 94 switches the current command for turning left or right based on the turning direction signal, and calculates the front-downward pitch control command value for each wheel. At this time, the front-downward pitch control command value becomes the current correction value.

Adders 66, 67, 68, and 69 add the front-down pitch control command value (current correction value) of each wheel to the current command value for roll control. Saturation processors 70, 71, 72, and 73 perform saturation processing on this current command value, and then output it to the damping force variable dampers 6 and 9 as a current command value.

Thus, in the second embodiment configured as described above, as in the first embodiment, appropriate pitch control can be performed even when roll control is being performed. Also, in the second embodiment, a command current based on a target damping force for roll control is supplied to the damping force variable dampers 6, 9, and the pitch moment prediction unit 83 (pitch moment prediction means) predicts the pitch moment generated in the vehicle body 1 based on the current command FB value of the command current. Therefore, since the pitch moment prediction unit 83 predicts the pitch moment based on the actual current value supplied to the damping force variable dampers 6, 9, it is possible to estimate a pitch that is more in line with the actual behavior of the vehicle than in the first embodiment. Therefore, in the second embodiment, it is possible to perform more appropriate front-down control than in the first embodiment.

Next, Figures 1 and 7 show a third embodiment of the present invention. The third embodiment is characterized in that, instead of using a vehicle model, the roll rate, roll angle, pitch rate, and relative velocity are detected by sensors or the like. In the third embodiment, the same components as those in the second embodiment described above are given the same reference numerals, and their explanation will be omitted.

The controller 101 is a control means constituted by a microcomputer or the like. The input side of the controller 101 is connected to the steering angle sensor 10, the vehicle speed sensor 11, etc., and is also connected to various sensors (not shown) capable of detecting the roll rate, roll angle, pitch rate, and relative speed. The output side of the controller 101 is connected to actuators (not shown) of the FR damper (variable damping force damper 6 for the right front wheel), FL damper (variable damping force damper 6 for the left front wheel), RR damper (variable damping force damper 9 for the right rear wheel), and RL damper (variable damping force damper 9 for the left rear wheel), etc.

The controller 101 obtains a target damping force for roll suppression by inputting the roll rate detected by, for example, a roll rate sensor to the target damping force calculation units 25, 26. In addition, the controller 101 includes a gain multiplication unit 102, a discrimination unit 103, a multiplication unit 104, an FF control unit 105, a subtraction unit 106, an FB control unit 107, an addition unit 108, etc., in order to calculate the target pitch moment.

The gain multiplication unit 102 of the controller 101 multiplies the roll rate signal detected by, for example, a roll rate sensor by a gain that is determined in advance for each vehicle, and calculates a target pitch rate that corresponds to the roll rate at that time. The gain multiplication unit 102 constitutes a target pitch rate calculation means that calculates a target pitch rate so that the degree to which the vehicle body 1 dives increases according to the magnitude of the roll rate of the vehicle body 1.

The discrimination unit 103 discriminates whether the roll angle signal is a positive or negative value. The roll angle is detected, for example, using a signal from the vehicle's lateral acceleration sensor. The multiplication unit 104 multiplies the sign of the roll angle by the signal (target pitch rate) from the gain multiplication unit 102, thereby determining the target pitch rate as a correction value so that the vehicle is in a dive state (head-down pitch).

When the correction value for the target pitch rate is input, the FF control unit 105 performs calculations using the following equations 2 to 4 to calculate the target pitch moment through feedforward control. The subtraction unit 106 calculates the difference between the actual pitch rate signal detected by a pitch rate sensor, for example, and the correction value for the target pitch rate as the error with respect to the target value.

The FB control unit 107 calculates the target pitch moment through feedback control according to the signal (error from the target value) from the subtraction unit 106. The FB control unit 107, as a PID controller, outputs the target pitch moment according to the error.

The FF control unit 105 is a controller that models the characteristics from the pitch moment to the pitch rate as a second-order vibration model, calculates a transfer function, and uses the inverse characteristics. The equation of motion for pitch motion is given by the following formula 2. Here, Q: pitch angle, Ix: pitch inertia, Kx: pitch stiffness, Cx: pitch damping coefficient, and Mx: pitch moment. Note that the dot in the formula indicates the first-order derivative with respect to time. Two dots indicates the second-order derivative.

From Equation 2, the transfer function from the pitch moment to the pitch rate is given by Equation 3 below. As a result, the transfer function from the pitch moment to the pitch rate can be calculated by Equation 4 below.

The adder 108 adds the target pitch moment calculated by the FF control unit 105 and the target pitch moment calculated by the FB control unit 107, and outputs the result as the final target pitch moment to the downstream current correction value calculation unit 81. The current correction value calculation unit 81 also receives the relative speed of each wheel calculated from a vertical acceleration sensor, a vehicle height sensor, etc. In addition, the current correction value calculation unit 81 receives the roll angle instead of the lateral acceleration, and the current command value (current command FB value) of each wheel from the delay unit 74. The current correction value calculation unit 81 calculates the current correction value based on the target pitch moment, the relative speed of each wheel, and the current command value (current command FB value) of each wheel.

Thus, in the third embodiment configured as described above, as in the first embodiment, appropriate pitch control can be performed even when roll control is being performed. Furthermore, in the third embodiment, compared to the first embodiment, it is possible to estimate a pitch that is more in line with the actual behavior of the vehicle. Therefore, in the third embodiment, as in the second embodiment, appropriate front-down control can be performed.

In the first to third embodiments, the target damping force calculation units 25, 26 (roll command value calculation means) calculate a roll command value for controlling the roll state of the vehicle body 1 from the lateral jerk (roll rate) as a road surface condition. The present invention is not limited to this. The road surface condition is not limited to the lateral jerk estimated by the vehicle model unit 22 or the like from the steering angle and vehicle speed, but may be an estimated value estimated based on a signal from an external environment recognition means such as a camera, or may be a detection value of a sensor (lateral acceleration sensor, roll rate sensor, etc.) that the vehicle has.

The relative velocity used in the first and second embodiments may be the differential value of the vehicle height sensor, or may be calculated by, for example, calculating the relative acceleration from the detection values of the unsprung acceleration sensor and the sprung acceleration sensor, and integrating this value. If the road surface is flat, the movement of the unsprung mass can be considered to be almost zero, so the relative velocity may be the sprung mass velocity obtained by integrating the detection value of the sprung mass acceleration sensor.

1: Vehicle body, 2: Front wheels (wheels), 3: Rear wheels (wheels), 4, 7: Suspension device, 6, 9: Variable damping force damper (damping force adjustable shock absorber, force generating mechanism), 21, 61, 101: Controller (control means), 25, 26: Target damping force calculation unit (roll command value calculation means), 29: Absolute value calculation unit, 30: Target pitch moment calculation unit (target pitch rate calculation means), 51: Correction target pitch moment calculation unit, 52: Pitch moment prediction unit (pitch moment prediction means), 53: Pitch rate correction unit (pitch rate correction means), 82: Front and rear wheel distribution unit, 83: Pitch moment prediction unit (pitch moment prediction means), 84, 85: Pitch rate correction unit (pitch rate correction means), 102: Gain multiplication unit (target pitch rate calculation means)

Claims (3)

1. A vehicle body attitude control device that controls an attitude of a vehicle body by controlling a generated force of a force generating mechanism provided between a wheel and a vehicle body of a vehicle,
a roll command value calculation means for calculating a roll command value for controlling a roll state of the vehicle body based on a road surface condition;
a pitch moment prediction means for predicting a pitch moment generated in the vehicle body based on the roll command value calculated by the roll command value calculation means;
a target pitch rate calculation means for calculating a target pitch rate so that a degree of diving of the vehicle body increases in accordance with a magnitude of a roll rate of the vehicle body;
and a pitch rate correcting means for correcting the value calculated by the target pitch rate calculating means, taking into consideration the value predicted by the pitch moment predicting means. The roll command value calculation means calculates a roll control target damping force as the roll command value,
2. A vehicle body attitude control device according to claim 1, wherein the pitch moment prediction means predicts the pitch moment generated in the vehicle body based on the roll control target damping force. The roll command value calculation means calculates a roll control target damping force as the roll command value,
a command current based on the roll control target damping force is supplied to the force generating mechanism,
2. The vehicle body attitude control device according to claim 1, wherein the pitch moment prediction means predicts the pitch moment generated in the vehicle body based on the command current.

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