P-PI and super twisting sliding mode control schemes comparison for high-precision CNC machining

Multi-axis high precision machining uses linear motors actuators in order to deal with robustness and stability in the broad range of cutting conditions. Currently, Computer Numerical Controls (CNCs) integrate PID type controllers in order to deal with tracking errors and disturbances. Moreover, CNCs introduce feed-forward control loop to cope with model variations. However, to overcome the influences of disturbances and model uncertainties natural control approach is adopted by sliding mode controller (SMC). This paper proposes a supertwisting sliding mode control algorithm to cope with the switching control for keeping the dynamics of the system within the designed requirements. Furthermore, the paper compares the behaviour of P-PI position-velocity control approach and supertwisting SMC. The implementation and evaluation of the algorithms in Matlab shows that super-twisting SMC is able to track the reference signal more accurate and robustness against the estimated processing parameters and disturbances. The main source of instability in sliding mode controller knowing as chattering is minimized when applied the super-twisting control algorithm.