This paper proposes an experienced self-tuning PID control method to the position control of slider-crank mechanism. The mathematical model of a slider crank mechanism coupled with PM actuator is described, firstly. By the Hamilton principle and Lagrange multiplier method, the mathematical formula is derived. Secondly, according to the experience of engineers, the initial PID parameters under normal operating condition can be found out. By the same way, the best parameters of PID controller under full load condition can be found, too. The proposed self-tuning PID controller will automatically tune its parameters under these ranges according to the position error and error derivation. Moreover, the PC-based controller is implemented to control the position of the motor mechanism coupling system. The simulation and experimental results will show the potential of the proposed controller