Vehicle attitude control device

Abstract

To provide a vehicle body attitude control device which can perform proper pitch control even when roll control is executed.SOLUTION: A controller 21 controls the attitude of a vehicle body by controlling the generation force of attenuation force variable dampers 6, 9 provided between front wheels 2, rear wheels 3 and a vehicle body 1 of a vehicle. The controller 21 comprises: target attenuation force calculation units 25, 26 which calculate a roll command value for controlling the roll state of a vehicle body 1 from the road surface state; a pitch moment prediction unit 52 which predicts a pitch moment generated in the vehicle body 1 on the basis of the roll command value; an absolute value calculation unit 29 and a target pitch moment calculation unit 30 which calculate a target pitch moment such that a degree of diving of the vehicle body 1 increases according to the magnitude of a roll rate of the vehicle body 1; and a pitch rate correction unit 53 which corrects the calculation value by the target pitch moment calculation unit 30 in consideration of the prediction value by the pitch moment prediction unit 52.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a vehicle body attitude control device that is preferably used in vehicles such as four-wheeled automobiles. [Background technology]

[0002] Patent Document 1 discloses that a target pitch rate is determined so that the vehicle body tilts downward in front in accordance with the roll rate, and the damping force of a suspension device is controlled in accordance with the target pitch rate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-46172 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, Patent Document 1 discloses a vehicle body attitude control device capable of roll control in addition to pitch control for a front downward tilt. Here, a pitch moment may be generated 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 consideration the variable range of the damping force. For this reason, there is a risk that the pitch control may not necessarily be appropriate for the vehicle.

[0005] An object of one embodiment of the present invention is to provide a vehicle body attitude control device that is capable of performing appropriate pitch control even when roll control is being executed. [Means for solving the problem]

[0006] One embodiment of the present invention is a vehicle body attitude control device that controls the attitude of the vehicle body by controlling forces generated by force generating mechanisms provided between wheels and a vehicle body of a vehicle, and is characterized by having roll command value calculation means for calculating a roll command value for controlling the roll state of the vehicle body from road surface conditions, 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, 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 the roll rate of the vehicle body, and pitch rate correction means for correcting the value calculated by the target pitch rate calculation means in consideration of the value predicted by the pitch moment prediction means. Effect of the Invention

[0007] According to one embodiment of the present invention, appropriate pitch control can be executed even when roll control is being executed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view showing a four-wheeled automobile to which a vehicle body attitude control device according to first to third embodiments of the present invention is applied. [Diagram 2] 1 is a control block diagram showing a vehicle body posture control device according to a first embodiment. [Diagram 3] FIG. 3 is a control block diagram showing a corrective target pitch moment calculation unit in FIG. 2. [Figure 4] 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. [Diagram 5] FIG. 5 is a control block diagram showing a vehicle body attitude control device according to a second embodiment. [Figure 6] 6 is a control block diagram showing a current correction value calculation unit in FIG. 5. [Figure 7] FIG. 11 is a control block diagram showing a vehicle body attitude control device according to a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle body attitude control device according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings, taking as an example a case in which the vehicle body attitude control device is applied to a four-wheeled automobile.

[0010] Here, Figures 1 to 4 show a first embodiment of the present invention. As shown in Figure 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.

[0011] The front-wheel suspension device 4 is provided 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 ​​(hereinafter referred to as springs 5) and left and right damping force adjustable shock absorbers 6 (hereinafter referred to as variable damping dampers 6) provided in parallel with each spring 5 between the left and right front wheels 2 and the vehicle body 1.

[0012] The rear-wheel suspension device 7 is provided 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 (hereinafter referred to as springs 8) and left and right damping force adjustable shock absorbers 9 (hereinafter referred to as variable damping dampers 9) provided in parallel with each spring 8 between the left and right rear wheels 3 and the vehicle body 1.

[0013] Here, the variable damping force dampers 6, 9 of each suspension device 4, 7 are configured using hydraulic shock absorbers of a damping force adjustment type. 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., in order to continuously adjust the damping force characteristics from hard characteristics (hard characteristics) to soft characteristics (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 more stages. Furthermore, the variable damping force dampers 6, 9 may be pneumatic dampers or electromagnetic dampers as long as they can switch the damping force.

[0014] The steering angle sensor 10 is provided on the vehicle body 1. The steering angle sensor 10 detects a steering angle (corresponding to a front wheel steering angle δf described later) when a driver of the vehicle steers the steering wheel during cornering or the like, and outputs a detection signal to a controller 21.

[0015] The vehicle speed sensor 11 is provided on the vehicle body 1. The vehicle speed sensor 11 detects, for example, the traveling speed of the vehicle (corresponding to a vehicle speed V described later) and outputs a detection signal thereof to the controller 21.

[0016] The controller 21 is a control means constituted by a microcomputer, etc. 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), the FL damper (variable damping force damper 6 for the left front wheel), the RR damper (variable damping force damper 9 for the right rear wheel), and the RL damper (variable damping force damper 9 for the left rear wheel), etc.

[0017] As shown in FIG. 2, controller 21 includes vehicle model unit 22, target damping force calculation units 25 and 26 for roll suppression, absolute value calculation unit 29, target pitch moment calculation unit 30, damper command value calculation units 40, 41, 42 and 43 for each wheel, and correction target pitch moment calculation unit 51.

[0018] 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 a 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 in accordance with the target pitch moment. In this way, the controller 21 is able to realize an improvement in the roll feeling.

[0019] The vehicle model unit 22 estimates the lateral acceleration αy using the 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. Here, V is the vehicle speed [m / s], A is the stability factor [S 2 / m 2 ], δf is the front wheel steering angle [rad], and L is the wheelbase [m].

[0020]

number

[0021] The phase adjustment filter 23 compensates for 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 next stage target damping force calculation units 25, 26 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, 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, 26 corresponds to the roll command value.

[0022] The sign reversal units 27, 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.

[0023] The absolute value calculation unit 29 obtains 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 a 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. 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 adopted 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 that the target pitch moment Ma0 only needs 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 only needs to be proportional to the lateral acceleration.

[0024] The desired pitch moment Ma0 is corrected by a corrective target pitch moment calculation unit 51, which will be described later. The corrective target pitch moment calculation unit 51 outputs a corrective target pitch moment Ma1 obtained by correcting the desired pitch moment Ma0.

[0025] When the correction target pitch moment Ma1 is input, the equal distribution calculation unit 31 divides the correction target pitch moment Ma1 into four 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 forces of the right front wheel 2 and left front wheel 2, which are the pitch generation parts, 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 forces of the right rear wheel 3 and 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.

[0026] Adder 36 adds the target damping force serving as the roll suppression portion from target damping force calculation unit 25 to the target damping force serving as the pitch generation portion from 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. Adder 37 adds the target damping force serving as the roll suppression portion from target damping force calculation unit 25 to the target damping force serving as the pitch generation portion from 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.

[0027] Furthermore, the pitch components are reversed between the front wheels 2 and the rear wheels 3. For this reason, subtraction unit 38 subtracts the target damping force serving as the roll suppression portion from target damping force calculation unit 26 from the target damping force serving as the pitch generation portion from 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. Subtraction unit 39 subtracts the target damping force serving as the roll suppression portion from target damping force calculation unit 26 from the target damping force serving as the pitch generation portion from 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.

[0028] After calculating the target damping force of each wheel by adding or subtracting the target damping force calculated based on the roll suppression amount and the pitch generation amount in this way, damper command value calculation units 40, 41, 42, 43 output a required current value according to a pre-stored damper characteristic map based on this target damping force and the relative speed estimated by relative speed estimation unit 44. That is, damper command value calculation units 40, 41, 42, 43 calculate damper command values ​​to be output as current values ​​(current command values) to actuators (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).

[0029] The variable damping force dampers 6, 9 on each wheel (left and right front wheels 2, rear wheels 3) have their damping force characteristics variably controlled continuously or in multiple stages between hard and soft in accordance with the current value (damper command value) supplied to the actuator.

[0030] Next, correction target pitch moment calculation unit 51 will be described in detail with reference to Fig. 3. Target pitch moment Ma0 from target pitch moment calculation unit 30 and the target damping forces from target damping force calculation units 25, 26 are input to correction target pitch moment calculation unit 51. Correction target pitch moment calculation unit 51 corrects target pitch moment Ma0 in consideration of the moment generated by roll control, and outputs correction target pitch moment Ma1. As shown in Fig. 3, correction target pitch moment calculation unit 51 includes a pitch moment prediction unit 52 and a pitch rate correction unit 53.

[0031] 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 damping forces for two wheels from the target damping forces for the front and rear wheels that may 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.

[0032] Moment calculation unit 52C multiplies the damping force output from doubling calculation unit 52A by the distance lf from the center of gravity to the front axle (front wheel 2). Moment calculation unit 52D multiplies the damping force output from doubling calculation unit 52B by the distance lr from the center of gravity to the rear axle (rear wheel 3). In this way, moment calculation units 52C and 52D calculate the moments of the front wheels 2 and rear wheels 3. Subtraction unit 52E subtracts the moment of the rear wheels 3 from the moment of the front wheels 2, and calculates a moment MaR generated by roll control from the difference between these.

[0033] Pitch rate correction unit 53 constitutes pitch rate correction means that corrects the value calculated by target pitch moment calculation unit 30 (target pitch moment Ma0) in consideration of the value predicted by pitch moment prediction unit 52 (moment MaR). Pitch rate correction unit 53 is constituted by a subtractor. Pitch rate correction unit 53 subtracts moment MaR generated by roll control from target pitch moment Ma0. That is, pitch rate correction unit 53 calculates the difference between target pitch moment Ma0 and moment MaR, and calculates corrective target pitch moment Ma1 from these differences.

[0034] The vehicle body attitude control device according to this embodiment has the configuration as 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 downward 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.

[0035] When a vehicle approaches a corner on a road and begins to turn, the steering operation is performed in the following order, for example: going straight → transitional turning → steady turning → transitional turning → going straight. At this time, the driver of the vehicle operates the steering wheel so as to change the steering angle along the road.

[0036] 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 the vehicle is in 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 the vehicle returns to traveling straight, the steering angle is nearly zero and kept neutral.

[0037] The lateral acceleration generated on the vehicle body 1 side changes in accordance with the steering angle, increasing or decreasing in a manner almost proportional to the steering angle. The roll angle on the vehicle body 1 side also changes in accordance with the steering angle, increasing or decreasing in a manner almost proportional to the steering angle.

[0038] In this embodiment and the comparative example, for example, the pitch angle is controlled to be low during steady turning, and 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.

[0039] In this way, by making the pitch rate and roll rate proportional to each other when the vehicle is cornering, no shaking occurs in the rotation axis of the vehicle body 1, and the steering feeling can be improved. 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 to each other, and further, 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.

[0040] In the comparative example, the target pitch moment, which is the front-downward pitch correction amount, is calculated without considering the pitch moment due to the roll control. Therefore, as shown by the dashed line in FIG. 4, the front-downward pitch correction amount is added to the control amount of the roll control, and as a result, the command value may exceed the upper or lower limit of the damping force variable range generated by the damping force variable dampers 6 and 9. In this case, in the comparative example, it may not be possible to generate a damping force that exceeds the upper or lower limit of the damping force variable range. Also, in the comparative example, since the pitch moment due to the roll control is not considered, even if the command value is within the range of the damping force variable range, it may not be possible to execute appropriate pitch angle control according to the vehicle state. Therefore, in the comparative example, there is a problem that it may not be possible to control to the intended front-downward pitch angle.

[0041] 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 in consideration of 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. Furthermore, in this embodiment, since the pitch moment due to roll control is taken into consideration, even when the direction of the pitch moment due to roll control and the direction of the target pitch moment are different, 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.

[0042] 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 state, 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) in consideration of 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.

[0043] Furthermore, the target damping force calculation units 25, 26 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 a 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.

[0044] Next, Fig. 1, Fig. 5 and Fig. 6 show a second embodiment of the present invention. The second embodiment is characterized in that a pitch moment prediction unit predicts the pitch moment generated in the vehicle body based on a 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 denoted by the same reference numerals, and their description will be omitted.

[0045] The controller 61 is a control means constituted by a microcomputer, etc. 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), the FL damper (variable damping force damper 6 for the left front wheel), the RR damper (variable damping force damper 9 for the right rear wheel), and the RL damper (variable damping force damper 9 for the left rear wheel), etc.

[0046] As shown in Fig. 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 a required current value from a prestored damper characteristic map 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 a damper command value for roll suppression to be output to an actuator (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, in order 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 inversion units 27, 28 is input to the damper command value calculation units 63, 65.

[0047] The adders 66, 67 calculate a total current command value by adding the current value for roll suppression from the damper command value calculators 62, 63 and a current correction value from a current correction value calculator 81, which will be described later. That is, the adders 66, 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, 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 saturation processors 70, 71. When the current command value exceeds a 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, 71 limit the current command value to the limit value.

[0048] The adders 68 and 69 calculate a total current command value by adding the current value for roll suppression from the damper command value calculators 64 and 65 and a current correction value from a current correction value calculator 81, which will be described later. That is, the adders 68 and 69 add the current correction value from the current correction value calculator 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 variable damping force damper 9 for the right rear wheel 3) and the RL damper (the variable damping force damper 9 for the left rear wheel 3) via saturation processors 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 variable damping force damper 9, the saturation processors 72 and 73 limit the current command value to the limit value. In addition, the current command values ​​output from the saturation processors 70, 71, 72, and 73 are input to the current correction value calculator 81 via a 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.

[0049] 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, 85.

[0050] 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.

[0051] 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.

[0052] The pitch moment prediction unit 83 includes a map 83A, a phase adjustment filter 83B, a lever ratio multiplication unit 83C, a sign inversion unit 83D, and estimated pitch moment calculation units 83E and 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 variable dampers 6 and 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 inversion 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 an estimated pitch moment of the rear wheel 3.

[0053] Pitch rate correction units 84 and 85 constitute pitch rate correction means for correcting the calculated value (target pitch moment) by target pitch moment calculation units 82B and 82C in consideration of the predicted value (estimated pitch moment) by pitch moment prediction unit 52. Pitch rate correction units 84 and 85 are each constituted by a subtractor. Pitch rate correction units 84 and 85 calculate the difference between the target pitch moment and the estimated pitch moment. Gain multiplication unit 86 multiplies the difference value output from pitch rate correction unit 84 by pitch moment FB control gain Kf and converts it into a current control command correction value for the front wheels 2. Gain multiplication unit 87 multiplies the difference value output from pitch rate correction unit 85 by pitch moment FB control gain Kr and converts it into a current control command correction value for the rear wheels 3.

[0054] Next, a 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 the damping force of the wheel on the outside of the turn (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 the damping force of the wheel on the inside of the turn (rebound side) is decreased (-). In this way, the controller 61 realizes a front downward roll.

[0055] 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 sign inversion units 90A and 90B. 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 / extension ratio of the damping force. This absorbs the damping force difference due to the extension and contraction relative to the current value.

[0056] Similarly, the left turning current command calculation unit 91 multiplies the current command correction values ​​for the right front wheel 2 and the left rear wheel 3 by "-1" using sign inversion units 91A and 91B. Gain multiplication units 91C and 91D multiply the current command correction values ​​for the left front wheel 2 and the left rear wheel 3, which are on the extension side, by gains Kif and Kir in order to match the compression / extension ratio of the damping force. This absorbs the damping force difference due to the extension and contraction relative to the current value.

[0057] A turning direction determination unit 93 determines the turning direction (left or right) based on the lateral acceleration (roll angle) passed through the vehicle filter 92, and outputs a turning direction signal. A command value switching unit 94 switches the current command for turning left or right based on the turning direction signal, and calculates a front-down pitch control command value for each wheel. At this time, the front-down pitch control command value becomes a current correction value.

[0058] 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 the current command value, and then output it to the damping-force variable dampers 6 and 9 as a current command value.

[0059] Thus, in the second embodiment configured as described above, similarly to the first embodiment, appropriate pitch control can be executed even when roll control is being executed. 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 execute an appropriate front downward control compared to the first embodiment.

[0060] 1 and 7 show a third embodiment of the present invention. The third embodiment is characterized in that, instead of a vehicle model, a roll rate, a roll angle, a pitch rate, and a 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 denoted by the same reference numerals, and the description thereof will be omitted.

[0061] The controller 101 is a control means constituted by a microcomputer, etc. An 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 a roll rate, a roll angle, a pitch rate, and a relative speed. An 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), the FL damper (variable damping force damper 6 for the left front wheel), the RR damper (variable damping force damper 9 for the right rear wheel), and the RL damper (variable damping force damper 9 for the left rear wheel), etc.

[0062] The controller 101 obtains a target damping force for suppressing roll by inputting a roll rate detected by, for example, a roll rate sensor to target damping force calculation units 25, 26. The controller 101 also 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 a target pitch moment.

[0063] A gain multiplication unit 102 of the controller 101 multiplies a roll rate signal detected by, for example, a roll rate sensor by a gain predetermined for each vehicle, and calculates a target pitch rate corresponding 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.

[0064] A discrimination unit 103 discriminates whether the sign of the roll angle signal is positive or negative. The roll angle is detected using, for example, a signal from a lateral acceleration sensor of the vehicle. A multiplication unit 104 multiplies the sign of the roll angle by the signal (target pitch rate) from the gain multiplication unit 102, thereby obtaining a target pitch rate as a correction value so that the vehicle is in a dive state (head-down pitch).

[0065] When the correction value of the target pitch rate is input, FF control unit 105 performs calculations according to the following formulas 2 to 4 to calculate a target pitch moment by feedforward control. Subtraction unit 106 calculates the difference between the signal of the actual pitch rate detected by, for example, a pitch rate sensor and the correction value of the target pitch rate as an error with respect to the target value.

[0066] FB control unit 107 calculates a target pitch moment by feedback control according to the signal (error from the target value) from subtraction unit 106. FB control unit 107, as a PID controller, outputs a target pitch moment according to the error.

[0067] Here, 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 the pitch motion is found from the following formula 2. Here, Q is the pitch angle, Ix is the pitch inertia, Kx is the pitch stiffness, Cx is the pitch damping coefficient, and Mx is the pitch moment. Note that the dot in the formula indicates the first-order differentiation with respect to time. Two dots indicate the second-order differentiation.

[0068]

number

[0069] 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 obtained by Equation 4 below.

[0070]

number

[0071]

number

[0072] Adder 108 adds the target pitch moment calculated by FF control unit 105 and the target pitch moment calculated by FB control unit 107, and outputs the value as a final target pitch moment to a current correction value calculation unit 81 at the subsequent stage. 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, or the like. In addition, the current correction value calculation unit 81 receives the roll angle instead of the lateral acceleration, and also receives the current command value (current command FB value) of each wheel from delay unit 74. The current correction value calculation unit 81 calculates a 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.

[0073] Thus, in the third embodiment configured as described above, similar to the first embodiment, appropriate pitch control can be executed even when roll control is being executed. Moreover, in the third embodiment, 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 third embodiment, similar to the second embodiment, appropriate front downward control can be executed.

[0074] 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.

[0075] The relative velocity used in the first and second embodiments may be a differential value of the vehicle height sensor, or may be calculated by calculating the relative acceleration from the detection values ​​of the unsprung side acceleration sensor and the sprung side acceleration sensor and integrating this value. If the road surface is flat, the movement of the unsprung part can be considered to be almost zero, so the sprung speed obtained by integrating the detection value of the sprung side acceleration sensor may be used as the relative velocity. [Explanation of symbols]

[0076] 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

1. 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.

2. 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.

3. 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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