Internal force analysis and rejection of hydraulically driven redundant parallel mechanism

To analyze the internal force characteristics and reduce the internal force of hydraulically driven parallel mechanism, the internal force space and its basis were described firstly. The influence of different factors on internal force of the system was discussed under the freedom control framework. Then an internal force rejection strategy based on the error-based minimal control synthesis with integral action (Er-MCSI) algorithm was proposed for the HDRPM with high nonlinearity, time-varying parameters and external disturbance. Finally, taking a six degrees-of-freedom (DOF) HDRPM with two redundant DOF as an example, under the working conditions of equal displacement, equal velocity and equal acceleration, the influence of different factors on internal force of the system was investigated. The proposed internal force rejection strategy was implemented. The results show that the control method can online adjust the parameters adaptively online and reduce the internal force effectively.