A new kind of hydraulic proportional loading method for actuator testing based on the relief valve controlled cylinder

A new kind of hydraulic proportional loading method based on the relief valve-controlled cylinder has been researched. The math model for the loading torque and the rotation angle has been deduced according to the loading principle, which proves their relationship is approximately linear within a certain rotation scale; the direction of the loading torque has also been analysed under different states of change valve. In order to reduce the rotary inertia and improve the dynamic performance, a connecting rod mechanism has also been designed to optimize the connection structure between the cylinder and the swing arm, accompanied with comparative analysis and simulation. Based on theory research, two sets of actual loading devices have been developed, which were certified by the loading experiments of a kind of electro-hydraulic actuator. Research and experiment results have proved that this hydraulic proportional loading method, with a simple control principle and easy engineering constructability, can supply approximately linear loading torque for actuator experiments within a ±90° scale, and the structure optimization by the connecting rod mechanism can eliminated overshoot and oscillation successfully.