The main objective of this study is to reduce the eccentric load’s influence on the dynamic characteristics of a horizontally installed rotary actuator. The solution is drilling a hole into the rotary shaft of a rotary cylinder. With the rotation of the rotary actuator the hole will open and connect the two working chambers within a certain angular range, the back pressure will increase and the torque introduced by the back pressure partly compensates for the torque of the eccentric load. The design procedure for the connecting hole is as follows: First, experiments that study the effect of eccentric loads on the dynamic characteristics of a rotary actuator were carried out, and a stability index v was proposed; Second, a mathematical model including the connecting hole was built; Third, a real–coded GA optimization design for the connecting hole whose object is to minimize v was conducted. Simulations and test results show that the method worked efficiently.  

Keywords: pneumatic rotary actuator, eccentric load, instability, real-coded genetic algorithm, optimization design