Low-speed friction and performance of new continuously rotating electro-hydraulic servomotor

Friction is an important factor to affect the super-low-speed property of the continuous rotary electro-hydraulic servomotor applied to simulators. The systematic analysis of the static frictional characteristic of a new continuously rotating electrohydraulic vane servomotor indicates that the frictional characteristics results in the periodic saltation with rotating angle, which is only theoretically controlled by the output pressure of reducing valve; the adjustable frictional characteristic is very favorable for the improvement of the motor performance. It has been demonstrated that the value of frictional torque and its saltation degree can be greatly reduced when the motor adopts odd vanes compared to even vanes. Some measures has been proposed to improve the frictional property. It is suggested to develop a novel nonlinear proportional-integral (NPI) controller and differential forward feedback. Experimental results have proved that this servomotor can be fitted into a simulator.