| The most important performance requirement of table servo systems can be summarized as"high frequency response, super-low velocity, wide–velocity regulation and high accuracy". Regarding to motor drive,"super-low velocity"is the guarantee of the smaller moment fluctuation with low velocity of the motor. However, as a result of the limitation of the manufacturing technological level, the main factors influencing the low velocity performance of the table are the friction moment and the fluctuation moment of the motor. At the same time, the quantization size of the angle-measured encoder of the position loop also affects the low-velocity performance of the table. Therefore, it is very important to analyze the low-velocity performance of the servo system and study the method of friction compensation for the improvement of the table system's performance of high accuracy and super-low velocity.Firstly, several evaluation means of the servo system's low-velocity performance have been put. Based on the thorough discussion of commonly used friction models, the math model of table servo systems with interference of friction moment has been constructed, and the influence of friction parameters to low velocities performance of servo systems has been analyzed.Secondly, the influence of the alveolus moment to the dithering of the systems has been analyzed. Then, the effect of the resolution in the position loop has been figured out. The simulation is conducted as well.At last, in view of the influence of friction to super low velocities performance, the two adaptive compensations based on Coulomb model and LuGre model have been thoroughly analyzed. In order to prove that the compensations satisfy the requirement of stability, the Lyapunov analysis has been made. Then, the two compensation methods have been put into application with the ET108B Table Servo System. It is proved by simulation that the low velocities performance has been improved.
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