Design and Hierarchical Force-Position Control of Redundant Pneumatic Muscles-Cable-Driven Ankle Rehabilitation Robot

Abstract

Ankle dysfunction is common in the public following injuries, especially for stroke patients. Most of the current robotic ankle rehabilitation devices are driven by rigid actuators and have problems such as limited degrees of freedom, lack of safety and compliance, and poor flexibility. In this paper, we design a new type of compliant ankle rehabilitation robot redundantly driven by pneumatic muscles (PMs) and cables to provide full range of motion and torque ability for the human ankle with enhanced safety and adaptability, attributing to the PM's high power/mass ratio, good flexibility and lightweight advantages. The ankle joint can be compliantly driven by the robot with full three degrees of freedom to perform the dorsiflexion/plantarflexion, inversion/ eversion, and adduction/abduction training. In order to keep all PMs and cables in tension which is essential to ensure the robot's controllability and patient's safety, Karush-Kuhn-Tucker (KKT) theorem and analytic-iterative algorithm are utilized to realize a hierarchical force-position control (HFPC) scheme with optimal force distribution for the redundant compliant robot. Experiment results demonstrate that all PMs are kept in tension during the control while the position tracking accuracy of the robot is acceptable, which ensures controllability and stability throughout the compliant robot-assisted rehabilitation training.

Event-Triggered Adaptive Hybrid Torque-Position Control (ET-AHTPC) for Robot-Assisted Ankle Rehabilitation

“…PM 1 and PM 2 are responsible for the rotation around Y-axis, PM 3 and PM 4 achieve the rotation around Z-axis; PM 5, together with PM 1 and PM 2, enables rotation around X-axis. More details of the developed robot have been described in our previous work [24].The stage III/IV/V of Brunnstrom are mapped to Level-A/B/C in the robotic rehabilitation system, and define a robotassisted rehabilitation index 𝜔 𝑅𝐼 . As presented in the previous research [24], the dynamic model of the robot is 𝑀(𝑞)𝑞̈+ 𝐶(𝑞, 𝑞̇)𝑞̇+ 𝐺(𝑞) = 𝜏 + 𝜏 𝑖𝑛𝑡 (1) where 𝑞̇ and 𝑞̈ respectively represent the first and the second derivatives of the robot's 3-DOF rotation angle vectors (X/Y/Zaxis) with respect to time.…”

“…More details of the developed robot have been described in our previous work [24].The stage III/IV/V of Brunnstrom are mapped to Level-A/B/C in the robotic rehabilitation system, and define a robotassisted rehabilitation index 𝜔 𝑅𝐼 . As presented in the previous research [24], the dynamic model of the robot is 𝑀(𝑞)𝑞̈+ 𝐶(𝑞, 𝑞̇)𝑞̇+ 𝐺(𝑞) = 𝜏 + 𝜏 𝑖𝑛𝑡 (1) where 𝑞̇ and 𝑞̈ respectively represent the first and the second derivatives of the robot's 3-DOF rotation angle vectors (X/Y/Zaxis) with respect to time. 𝜏 describes the robot's output torque, and 𝜏 𝑖𝑛𝑡 is the human-robot interaction torque, both are 3×1 vectors.…”

Mechanical Structure Design and Actuation Characteristics Analysis of the Parallel Driven Variable Stiffness Actuator With Unrestricted Rotation Range of the Output Shaft

“…The mechanical structure design of the parallel driven VSA based on the symmetrical Archimedes spiral cam groove plate is shown in Figure 21 4), and the label (5) indicates the spring deformation limit sleeve, which is installed on the spring guide shaft. The (6) indicates the linear compression spring, and the ( 7) is a slider that can slide on the spring guide shaft to compress the spring, and the ( 8) is the upper end cover of the spring guide shaft, and the ( 9) is an auxiliary lever with a guide groove, and the (10) is the pin shaft, and the (11) represents the output shaft of the actuator. The (1), ( 2), ( 3), ( 8), ( 9) and ( 11) are all connected by the pin shaft (10).…”

“…In the flexible actuation technology of robot, there are several common implementation methods. For example, the active compliance control of the rigid robot joints based on algorithms and sensors [1][2], the compliance control based on magnetorheological fluid damper [3], the series elastic actuators [4][5], the flexible pneumatic actuator [6][7][8][9], the cable-driven flexible actuator [10][11][12], the flexible actuator based on magnetic spring [13], and the variable impedance actuator with other structural forms [14][15], etc. Among the above flexible actuation, the active compliance control and the variable impedance control technologies are the most studied and applied.…”

Control Design for CABLEankle, a Cable Driven Manipulator for Ankle Motion Assistance

“…Most of the past robotic designs are based on a static platform design, where a non-portable device requires the patient to keep his foot on a grounded platform (usually while sitting down) to perform rehabilitation [12][13][14][15][16][17][18][19][20][21]. A similar design involves a mechanism driven by pneumatic muscles to help exercise a single leg [22,23]. Most of such designs are not only bulky, but also fixed to the ground.…”