For reliability tests of machine tools

a load simulator based on a 3P-(4S) parallel mechanism is proposed. An explicit force control system is designed based on a proportional-integral (PI) controller. A fuzzy logic is introduced to adapt various following errors of output forces. A force feedforward is integrated to the system to develop its dynamic performance and decrease the hysteresis of the output forces. Meanwhile

a position feedforward that predicted the position of the spindle is designed to eliminate the disturbance caused by the unknown feeding motions of the spindle. Loading experiments is conducted on a stationary and a moving spindle

respectively

to validate the feasibility of the proposed control system.