ABSTRACT
The linear PID control is a classical control method, which is very easy to be understood. The PID controller is designed in frequency domain based on the linear model of the electro-hydraulic system. Servo valve is the control element. It receives a voltage signal given by the controller and be converted to the spool position to control the oil flow in the hydraulic cylinder. The system performance should be considered due to the selected motor and the pump. The maximal allowable speed of the pump is 3000 rpm. The pressure of the cylinder with load is a dynamic value, which depends on the mass of the load, joint rotational movement, angular velocity, and angular acceleration. The actual angles of two joints are measured by encoders. The errors between actual angles and command angles are as input of control system. The controller inputs the control voltage into proportional valves and the spool dynamic positions are regulated to drive the cylinder motion.
