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

In this paper, the performance of hydraulic actuation systems is analyzed and, it is observed that the performance of symmetrical (rotary) actuators is significantly better than their linear asymmetrical counterpart. The deficiency of linear actuators, resulting from their asymmetry, manifests itself 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 pressure chambers are made equal without the need for a dead-space on the fixed end of the piston as required by commercial double rod pistons. The paper discusses the benefits of this new design and demonstrates the advantages of its flow characteristics and its command input/force relationship. The theoretical observations are supported by experiments conducted on a large hydraulic robot. The Workmaster, formerly manufactured by Thorn EMI Robotics.