Semi-active suspension system with control circuit having a direct control loop including an inverse model of the damper

A semi-active suspension system comprising:

• an actuator within a hydraulic circuit having relatively movable first and second ends, a damping cylinder, a solid piston slidably mounted in said cylinder and defining with said cylinder a first, compression chamber and a second, expansion chamber, a damping fluid in said cylinder and within said first and second chambers, flow actuating means in said hydraulic circuit for controlling replenishment and evacuation of damping fluid alternatively in said first and second chambers, and a control circuit connecting said flow actuating means to said first and second chambers of said actuator,
• the improvement comprising:
• a direct control loop in said control circuit comprising an inverse model of said semi-active damper, means for supplying a generated reference force signal Fc to said inverse model, a speed feedback loop for supplying a signal of measured relative speed y to said inverse model, said inverse model further comprising means responsive to said signals Fc and y for supplying a control signal i.sub.th to said flow actuating means as a function of measured relative speed y and as a function of the reference force Fc, thereby servo-controlling the damping force on the actuator which is in opposition to the measured relative speed y and to said generated reference force Fc, and wherein said semi-active suspension system further comprises a force feedback loop operatively connected between said actuator and said flow actuating means and including a force sensor to measure a force F exerted on said actuator, means for comparing said exerted force F with said reference force Fc and for generating an error signal .epsilon.F, means for applying said error signal .epsilon.F to said flow actuating means to thereby servo-control the exerted damping force F to said force reference signal Fc, a corrector interposed between said means for generating said force reference signal Fc and said flow actuating means, and wherein said direct control loop is connected at one end between said means for supplying said generated reference force signal Fc and said corrector, and another end of said direct control loop is connected between said corrector and said flow actuating means for delivering an additional correction .delta.i to an output at said other end of said direct control loop to create a control signal i applied directly to the flow actuating means.