Implementation of cable-driven waist rehabilitation robotic system using fractional-order controller

This paper presents the design and implementation of a fractional-order controller for a cable-driven waist rehabilitation robotic system (CDWRRS) based on an improved Oustaloup numerical approximation method. First, the mechanical structure and hardware design of the CDWRRS are established based on the demands of waist rehabilitation training. Next, a fractional-order controller is designed and implemented. The function of the proposed controller is realised using integer-order systems for approximation. Additionally, an improved numerical approximation method is proposed based on the Oustaloup numerical approximation method. In the Oustaloup method, the zeros and poles of the integer-order transfer functions are different, and the approximation errors near the endpoints of the frequency range are not considered. To address these problems, the proposed numerical approximation method improves the approximation accuracy and reduces the calculation cost. Finally, numerical examples and experimental results are presented to verify the feasibility and effectiveness of the improved Oustaloup numerical approximation method and the designed fractional-order controller for the developed CDWRRS.