Development of Spool Position Measurable Rotary Servovalve

In this instruction, we propose an electric motor-driven hydraulic rotary servovalve to compensate for the friction, internal leakage effect, and modeling uncertainties. The proposed rotary servovalve is directly attached to the electric motor and absolute encoder to operate and measure the control input (e.g., spool position), respectively. Therefore, the proposed hydraulic servovalve controlled system can be changed from a non-collocated system to a collocated system, which is easy to guarantee interaction stability2