Most motion simulators manufactured today benefit from the use of electric actuators. The common solution to a heavier payload is a larger actuator. However, this results in higher power consumption and expenses. Furthermore, the electric actuators continue to use power in stationary positions as well as low platform speeds. To overcome these drawbacks, a combination of passive pneumatic actuators may be supplemented with the electric actuators to allow the motion simulators to sustain equipment weight. However, it is challenging to design a weight compensation system so that it could be efficient throughout the entire workspace. In this paper, kinematics and dynamics of the six axis FUM Stewart robot with three passive redundant pneumatic actuators are investigated. Six independent trajectories using maximum allowed velocity and accelerations are defined and the trajectory containing maximum actuator force is selected. A genetic algorithm is used to optimize the power consumption for the worst-case trajectory. A cost function is defined to minimize the absolute value of average as well as maximum actuator forces by identifying a structural kinematics arrangement of the passive pneumatic actuators. Results indicate that the weight compensation implemented on the FUM Stewart successfully decreased actuator forces in static positions as well as dynamics trajectories by at least 29% and 37.1%, respectively. Furthermore, maximum actuators’ forces during both outstroke and instroke are mostly balanced which helps improve the life expectancy of the mechanical system. The procedures outlined in this paper are general and may be applied to any existing Stewart robot.

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