Abstract
Due to the advantages of its compact structure and high operation accuracy, the six degrees of freedom (6-DOF) parallel platform has been widely used as a carrier of medical rehabilitation devices. Fuzzy adaptive algorithm does not depend on the mathematical model of controlled object, which possesses good nonlinear characteristics. Those entire features make it an effective method to control such complex and coupling platforms. To facilitate the application of robotics in lower limb rehabilitation fields, a robotic system in practical environment was established based on kinematics modeling of the 6-DOF Stewart-based platform. In order to improve the velocity tracking accuracy, this paper proposed a closed-loop control strategy based on fuzzy adaptive algorithm. The velocity feedback information was utilized to modify the PID parameters adaptively in realtime through fuzzy inference units. Several experiments in practical environment were conducted, and the results demonstrated that the proposed algorithm could effectively reduce the speed jitter, enhance the position and velocity tracking precision of the robot, and the reliability and robustness of the system could also be ensured.
Highlights
With the tendency of aging society, there is a considerable increase in the needs of health care and rehabilitation, especially among elderly and disabled people, which are supposed to recover or compensate patients’ functional capabilities, enable them to be independent, and improve their living qualities [1, 2]
During the motion control of the rehabilitation robot, the system may become unstable due to the uncertain variations of the system loads and dynamic parameters, which would lead to the secondary injury of the patients
It is of great significance to maintain the trajectory and velocity tracking accuracy and stability for medical purpose [18]
Summary
With the tendency of aging society, there is a considerable increase in the needs of health care and rehabilitation, especially among elderly and disabled people, which are supposed to recover or compensate patients’ functional capabilities, enable them to be independent, and improve their living qualities [1, 2]. There exists a wide variety of medical robots that differ in mechanical structures, control strategies, or even the target users. In terms of lower limb rehabilitation, the HAL in Japan is a typical lower limb rehabilitation robot that implements active control for patients, making people able to move the actuators by mapping the EMG signals to the joint angles of lower extremity [4]. The mechanical design is the basis of robot-assisted rehabilitation system, which should comply with the disciplines of being simple, lightweight, and to control [6]. The 6DOF parallel robot is probably a feasible solution in the lower limb rehabilitation fields, for its simple structure and superior adaptability, enabling the robot’s movement of range, and the rehabilitation parameters can be adaptable to different patients
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