فهرست نشریات علمی دسترسی آزاد ایران

Position control of pneumatic actuators as an infinite impedance control is always used in rehabilitation devices, teleoperation, and tactile interfaces. Along with tracking accuracy, the control bandwidth of the system has always been one of the concerns of researchers, and the level of open-loop stiffness of the actuator determines its stability range. The use of a model-free control method is desirable for the reasons of reducing system costs, increasing tracking accuracy, and the possibility of increasing the sampling rate, which increases the control bandwidth. Because the use of model-free control methods eliminates the need to use some additional sensors, multi-stage derivation processes, and reduces the volume of controller calculations. Hence, in this paper a model-free control of the fuzzy-pulse width modulation type is introduced, which improves the tracking accuracy in the initial and final ranges of the piston stroke through direct feedback of the piston position and can perform the tracking process at three levels of low, medium, and high stiffness. Comparison of experimental results between two conventional and modified pulse width modulation fuzzy controllers shows a reduction in the root mean square and variance of the tracking error for harmonic reference input at low and medium stiffness levels and in the initial and final ranges of the piston stroke.