Design and analysis of a new symmetrical linear actuator for hydraulic andpneumatic systems

In this paper, the performance of hydraulic actuation systems is analyzed a nd, it is observed that the performance of symmetrical (rotary) actuators i s significantly better than their linear asymmetrical counterpart. The defi ciency of linear actuators, resulting from their asymmetry, manifests itsel f as an undesirable dynamic effect related to the pressure characteristics of the actuator chambers. Subsequently, a new symmetrical design for linear actuators is proposed. In this design, the active areas of the two pressur e chambers are made equal without the need for a dead-space on the fixed en d of the piston as required by commercial double rod pistons. The paper dis cusses the benefits of this new design and demonstrates the advantages of i ts flow characteristics and its command input/force relationship. The theor etical observations are supported by experiments conducted on a large hydra ulic robot. The Workmaster, formerly manufactured by Thorn EMI Robotics.