System for controlling active suspensions of a vehicle

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.

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.