Patent ID: 8191456

Claim:
A method of driving a hydraulic actuator comprising: at least one actuation chamber; a mobile piston which slides inside an actuation chamber; and a pressure-controlled proportioning solenoid valve for connecting the actuation chamber to a hydraulic accumulator containing a pressurized control oil and to a tank containing a control oil at atmospheric pressure; the method comprising the steps of: determining a force which must be developed by the hydraulic actuator; determining a desired load pressure (P load ) inside the actuation chamber according to the force which must be developed by the hydraulic actuator; determining a desired electric current driving value (I TOT ) of the proportioning solenoid valve according to the desired load pressure (P load ) inside the actuation chamber; and supplying the proportioning solenoid valve with an electric driving current having the desired value (I TOT ); estimating a pressurized oil flow rate (Q FF ) which crosses the proportioning solenoid valve; determining a first open-loop contribution (I P ) according to the pressurized oil flow rate (Q FF ) which crosses the proportioning solenoid valve and according to the desired load pressure (P load ) inside the actuation chamber; estimating a pressure drop (DltP EV ) through the proportioning solenoid valve; estimating a desired position (X SpoolRef ) of the spool of the proportioning solenoid valve according to the pressure drop (DltP EV ) through the proportioning solenoid valve and according to the pressurized oil flow rate (Q FF ) which crosses the proportioning solenoid valve; determining a second open-loop contribution (I QFF ) according to the desired position (X SpoolRef ) of the spool of the proportioning solenoid valve; determining a third closed-loop contribution (I QCL ) according to the difference (ε X ) between a desired value (X REF ) of the position of the mobile piston and a real value (X) of the position of the mobile piston; and calculating the desired electric driving current value (I TOT ) by means of an algebraic sum of the three contributions (I P , I QFF , I QCL ).