System for controlling active suspensions of a vehicle

• US 5,113,345 A
• Filed: 05/22/1990
• Issued: 05/12/1992
• Est. Priority Date: 05/29/1989
• Status: Expired due to Fees

• Current Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Hiwatashi, Yutaka, Mine, Atsushi, Kamimura, Katsuyoshi
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): TRANS, VINCENT N
• Application Number:
  US07/526,908
• Time in Patent Office: 721 Days
• Field of Search: 364/424.05, 280/707, 280/DIG. 2, 280/840, 280/6.1
• US Class Current: 701/38
• CPC Class Codes: B60G 17/0155 pneumatic unit
• CPC Class Codes: B60G 17/016 characterised by their responsiveness, when the vehicle is travelling, to specific motion, a specific condition, or driver input B60G17/017 takes precedence
• CPC Class Codes: B60G 2202/154 with an accumulator
• CPC Class Codes: B60G 2202/413 Hydraulic actuator
• CPC Class Codes: B60G 2400/104 lateral or transversal with regard to vehicle
• CPC Class Codes: B60G 2400/106 longitudinal with regard to vehicle, e.g. braking
• CPC Class Codes: B60G 2400/204 Vehicle speed
• CPC Class Codes: B60G 2400/252 vertical
• CPC Class Codes: B60G 2400/41 Steering angle
• CPC Class Codes: B60G 2400/51 in suspension unit
• CPC Class Codes: B60G 2400/82 Ground surface
• CPC Class Codes: B60G 2600/02 Retarders, delaying means, dead zones, threshold values, cut-off frequency, timer interruption
• CPC Class Codes: B60G 2600/04 Means for informing, instructing or displaying
• CPC Class Codes: B60G 2600/12 Sampling or average detecting; Addition or substraction
• CPC Class Codes: B60G 2600/14 Differentiating means, i.e. differential control
• CPC Class Codes: B60G 2600/18 Automatic control means
• CPC Class Codes: B60G 2600/26 Electromagnets; Solenoids
• CPC Class Codes: B60G 2800/012 Rolling condition
• CPC Class Codes: B60G 2800/24 Steering, cornering
• CPC Class Codes: B60G 2800/244 Oversteer
• CPC Class Codes: B60G 2800/246 : Understeer
• CPC Class Codes: Y10S 280/01 : Load responsive, leveling of vehicle

Abstract

In a system for controlling active suspensions of a motor vehicle, having fluid suspensions for the respective wheels, a longitudinal acceleration sensor, a lateral acceleration sensor, control valves for the respective suspensions, and a controller for producing a control quantity to adjust the control valves to charge and discharge fluid into and out of the fluid suspensions so as to control the vehicle attitude, the reaction force of each suspension is detected and a mean value of the suspension reaction force is calculated to determine the loading condition of the vehicle while the vehicle is driven straight ahead at a constant speed. The control quantity is corrected by a correcting circuit so as to match the loading condition of the vehicle whereby the vehicle attitude is precisely controlled so as to match the vehicle weight even in such a transient state as acceleration, deceleration and turning. The internal pressure of each suspension may be detected as the reaction force.

Claims

1. An active suspension control system for a motor vehicle having a plurality of wheels and having a fluid suspension provided between a body of said motor vehicle and each wheel for supporting said body, control means for charging and discharging a fluid into and out of said fluid suspension in order to extend and contract said suspension respectively, a plurality of sensors for sensing behavior of the motor vehicle and for producing sensor signals indicative thereof, said sensors including G-sensor means mounted on said motor vehicle for detecting acceleration of the vehicle and for generating an acceleration signal indicative thereof and a vehicle speed sensor for detecting vehicle speed and for generating a vehicle speed signal indicative thereof, and a controller for calculating a control quantity based on said acceleration signal and a standard vehicle weight and for producing a control quantity signal to the control means to adjust an amount of the fluid so as to maintain an attitude of the motor vehicle, the system comprising:

suspension reaction force detection means for detecting reaction force applied to each suspension;

determining means responsive to said sensor signals for determining a constant-speed and straight-ahead driving state of the motor vehicle and for generating a driving state signal indicating said state when said vehicle is at constant speed and straight-ahead driving state;

first calculating means for calculating a mean value, as the load on the motor vehicle, of said reaction force on each suspension during a predetermined time period when said driving state signal is generated by said determining means and for producing a mean value signal for each suspension indicative thereof;

correcting means responsive to each of said mean value signals for correcting said control quantity for each suspension so as to maintain the attitude of the motor vehicle under a transitional condition in an optimum state even when the vehicle weight changes from said standard vehicle weight;

said correcting means including second calculating means responsive to the magnitude of each of said mean value signals for calculating a corrected gain to be applied to the control quantity for correction thereof, first computing means responsive to a signal from said G-sensor means and said corrected gain for calculating a load shift quantity corresponding to the change of the load applying to the suspension due to the acceleration or deceleration of the vehicle and second computing means responsive to said load shift quantity for calculating the control quantity.

2. The system according to claim 1, wherein said first calculating means is adapted to respond to said predetermined time which is longer than a pitching period of the motor vehicle.

3. The system according to claim 2, wherein said first calculating means is adapted to respond in approximately two seconds.

4. The system according to claim 1, wherein said G-sensor means comprises a longitudinal G-sensor for sensing a longitudinal acceleration of the motor vehicle and a lateral G-sensor for sensing a lateral acceleration of the motor vehicle, and said determining means is responsive to said longitudinal and lateral G-sensors for determining the constant-speed and straight-ahead driving state when the magnitudes of said longitudinal and lateral accelerations are both zero.

5. The system according to claim 1, wherein said plurality of sensors include a steering angle sensor for sensing a steering angle of the motor vehicle, and said determining means is responsive to said vehicle speed sensor and said steering angle sensor for determining the constant-speed and straight-ahead driving state when the vehicle speed is constant and the steering angle is zero angle.

6. The system according to claim 1, wherein said controller is adapted to produce a control quantity corresponding to the flow rate of the fluid to be charged or discharged into or out of each suspension.

7. The system according to claim 6, wherein said suspension reaction force detection means is a sensor for sensing the internal pressure of the suspension as the reaction force.

8. The system according to claim 1, wherein said controller is adapted to produce a control quantity corresponding to internal pressure of the suspension.

9. The system according to claim 8, wherein said detection means is adapted for introducing the control quantity to be applied to each suspension to said calculating means as the reaction force

10. An active suspension control system for a motor vehicle having a plurality of wheels and having a fluid suspension provided between a body of said motor vehicle and each wheel for supporting said body, control means for charging and discharging a fluid into and out of said fluid suspension in order to extend and contract said suspension respectively, a plurality of sensors for sensing behavior of the motor vehicle and for producing sensor signals indicative thereof, said sensors including G-sensor means mounted on said motor vehicle for detecting acceleration of the vehicle and for generating an acceleration signal indicative thereof and a vehicle speed sensor for detecting vehicle speed and for generating a vehicle speed signal indicative thereof, and a controller for calculating a control quantity based on said acceleration signal and a standard vehicle weight and for producing a control quantity signal to the control means to adjust an amount of the fluid so as to maintain an attitude of the motor vehicle, the system comprising:

suspension reaction force detection means for detecting reaction fore applied to each suspension;

determining means responsive to said sensor signals for determining a constant-speed and straight-ahead driving state of the motor vehicle and for generating a driving sate signal indicating said state when said vehicle is at constant-speed and straight-ahead driving state;

first calculating means for calculating a mean value, as the load on the motor vehicle, of said reaction force on each suspension during a predetermined time period when said driving state signal is generated by said determining means and for producing a mean value signal for each suspension indicative thereof;

correcting means responsive to each of said mean value signals for correcting said control quantity for each suspension so as to maintain the attitude of the motor vehicle under a transitional condition in an optimum state even when the vehicle weight changes form said standard vehicle weight; and

said correcting mean including second calculating means responsive to the magnitude of each of said mean value signals for calculating a rate between said mean value and a reference reaction force defined at the standard vehicle weight, said rate to be applied to the control quantity for correcting thereof.

11. The system according to claim 10, wherein said controller is adapted to preset to said standard vehicle weight the weight of the motor vehicle with one passenger in the vent that the motor vehicle is driven straight ahead at a constant speed.

12. An active suspension control system for a motor vehicle having a plurality of wheels and having a fluid suspension provided between a body of said motor vehicle and each wheel for supporting said body, control means for charging and discharging a fluid into and out of said fluid suspension in order to extent and contract said suspension respectively, a plurality of sensors for sensing behavior of the motor vehicle and for producing sensor signals indicative thereof, said sensors including G-sensor means mounted on said motor vehicle for detecting acceleration of the vehicle and for generating an acceleration signal indicative thereof and a vehicle speed sensor for detecting vehicle speed and for generating a vehicle speed signal indicative thereof, and a controller for calculating a control quantity based on said acceleration signal and a standard vehicle weight and for producing a control quantity signal to the control means to adjust an amount of the fluid so as to maintain an attitude of the motor vehicle, the system comprising:

suspension reaction force detection means for detecting reaction force applied to each suspension;

determining means responsive to said sensor signals for determining a constant-speed and straight-ahead driving state of the motor vehicle and for generating a driving state signal indicating said state when said vehicle is at constant-speed and straight-ahead driving state;

first calculating means for calculating a mean value, as the load on the motor vehicle, of said reaction force on each suspension during a predetermined time period when said driving state signal is generated by said determining means and for producing a mean value signal for each suspension indicative thereof;

correcting means responsive to each of said mean value signals for correcting said control quantity for each suspension so as to maintaining the attitude of the motor vehicle under a transitional condition in an optimum state even when the vehicle weight changes form said standard vehicle wight;

said G-sensor means comprising a longitudinal G-sensor for sensing a longitudinal acceleration of the motor vehicle and a lateral G-sensor for sensing a lateral acceleration of the motor vehicle;

said determining means being responsive to said longitudinal and lateral G-sensors for determining the constant-speed an straight-ahead driving sate when the magnitude of said longitudinal and lateral accelerations are both zero; and

said correcting means including a corrected gain calculating device responsive to each of said mean value signal for calculating a corrected gain, a longitudinal load shift calculation device responsive to said longitudinal acceleration and said corrected gain for calculating a load shift quantity of said body in the longitudinal direction due to the acceleration or deceleration of the vehicle and for producing a longitudinal load shift quantity signal, a first suspension reaction force variation calculating device responsive to said longitudinal load shift quantity signal for calculating a reaction force variation in the suspension and for producing a first variation signal, a rolling moment calculating device responsive to said lateral acceleration for calculating a rolling moment exerted on said body and for producing a rolling moment signal, a lateral load shift quantity calculating device responsive to said rolling moment signal and said corrected gain for calculating a load shift quantity of said body in the lateral direction due to the rolling of the vehicle and for producing a lateral load shift quantity signal, a second suspension reaction force variation calculating device responsive to said lateral load shift quantity signal for calculating a reaction force variation in the suspension and for producing a second variation signal and a control quantity calculating device responsive to said first and second variation signals for calculating said control quantity to be supplied to said control means.