A novel redundantly actuated parallel machine tool was introduced. The inverse kinematic of 5-UPS/PRPU PMT with redundant actuation was analysed and the driven force of redundant actuation limb was planned. The force/position hybrid control strategy and dynamic differential calculation control strategy were proposed. Then the experiment of evaluating dynamics in the position control mode and in the force/position hybrid control was carried out respectively. The experiment shows that, the force/position hybrid control can improve driven torque of each limb better, balance the load of each limb and is of great help for enhance the dynamic performance of entire PMT.

The hardware control system of the 5-UPS/PRPU PMT (parallel machine tool) with redundant actuation was reconstructed to realize its hybrid force/position control, which was based on the primary “IPC+PMAC motion controller” system mode. Meanwhile, more perfect open type PMT control platform was constructed. Visual Basic language was used to realize the force servo control of the redundant limb and the relevant experiment was completed in the primary CNC system, combining with the PAMC motion controller library function. The results show that the force servo control strategy is exact and the newly designed hardware control system is effective, these results also provide feasible hardware basis and control method to realize the hybrid force/position control.

For the real-time pose adjustment of the sub-reflector of antenna to ensure its best condition, Stewart platform-based mechanism is adopted. This paper presents the configuration optimization of the adjusting parallel mechanism taking the minimum force acted on each limb as the target, and the basic structural parameters of the mechanism are obtained. Considering the weight of the moving platform, the external load, and the influence of the snow and the wind, the maximum force acted on the limbs of the mechanism in the required workspace is calculated, which established the foundation for the structural design of the mechanism. The contents of this paper possess theoretical significance and engineering value for the development of the adjusting mechanism for the sub-reflector of antenna.

Six-axis force sensors based on Stewart platform necessitate highly accurate, sensitivity and dynamic response. In response to this need, errors analysis and compensation of the force sensor are essential. In this paper, the measurement error generated by the upper platform deformation is discussed and evaluated. Furthermore, in order to improve the precision, a real-time compensation algorithm is proposed depending on the external force applied on the force sensor. Finally, a numerical simulation example is presented, which indicates that the precision is related to the stiffness of limbs directly and improved obviously by the compensation algorithm.

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