Internal variable feedback control in electro-hydraulic loading

The internal feedback control principle was proposed for force tracing control of electro-hydraulic loading servo-system. A measurable internal variable signal was feedbacked to compensate flow, so that the loading system tracked position system without delay. After feedback control, the transfer function of loading system was changed and the dynamic performance was improved, the extra force in system output was limited to small range. It is proved that the disturbance velocity, acceleration of position is eliminated through internal feedback of PID form. The conclusions are: internal feedback has superior performance to a conventional feedforward control in master-slave system force tracking electro-hydraulic loading to reduce disturbance force and improve the dynamic behavior.