Continuous wave mud pulse generator control using improved sliding mode reaching law

Conventional PID control is widely used in the permanent magnet synchronous motor (PMSM) speed control system because of it is simple to design, but it is difficult to meet the high precision control requirement for controlling the continuous wave mud pulse generator used in the circumstance of downhole. Therefore, an improved exponential reaching law based on the conventional sliding mode control (SMC) is proposed to achieve the purpose of tracking the velocity step signal quickly and accurately. In this law, fractional polynomials containing exponential terms in the coefficients of constant velocity terms is introduced. Simultaneously, to attenuate the influence of chattering phenomenon, saturation function is used to instead of switching function and integral-type sliding mode surface is applied to improve the convergence speed. The simulations show that the proposed improved sliding mode reaching law can effectively improve the performance of control and robustness compared with conventional PID control.