Cable Driven Rehabilitation Robots: Comparison of Applications and Control Strategies

Abstract

Significant attention has been paid to robotic rehabilitation using various types of actuator and power transmission. Amongst those, cable driven rehabilitation robots (CDRRs) are relatively newer and their control strategies have been evolving in recent years. CDRRs offer several promising features, such as low inertia, lightweight, high payload-to-weight ratio, large work-space and configurability. In this paper, we categorize and review the cable driven rehabilitation robots in three main groups concerning their applications for upper limb, lower limb, and waist rehabilitation. For each group, target movements are identified, and promising designs of CDRRs are analyzed in terms of types of actuators, controllers and their interactions with human. Particular attention has been given to robots with verified clinical performance in actual rehabilitation settings. A large part of this paper is dedicated to comparing the control strategies and techniques of CDRRs under five main categories of: Impedance-based, PID-based, Admittance-based, Assist-as-needed (AAN) and Adaptive controllers. We have carefully contrasted the advantages and disadvantages of those methods with the aim of assisting the design of future CDRRs.

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

“…The label (8) indicates the reducer for driving the spur gear (11) and the internal gear (12). The label (9) indicates the mounting base of the reducer, and the label (10) indicates the ring for bearing positioning. The ( 15) is driven by the internal gear (14), and the ( 16) is driven by the internal gear (12).…”

“…As shown in Figure 17(a), two planet gears ( 9) are installed on the planet carrier (8) and can rotate around their respective axes. A lever pivot (10) is processed or installed at the position of the pitch circle of the planetary gear. When there is relative movement between the planet carrier ( 8) and the internal gear (11), the planet gear (9) will rotate, and the distance between the two lever pivots will change.…”

“…The component structure and transmission relationship of the designed parallel driven VSA based on Archimedes spiral cam disc mechanism are shown in Figure 18. As shown in Figure 18(a), the ( 1) is fixedly connected with the linear guide groove base (4) through the bolts, and the ( 2) is fixedly connected with the Archimedes spiral cam disc (5) through the bolts, and the lever pivot ( 7) is placed in the spiral groove of the Archimedes spiral cam disc and can move in the guide groove of the lever (10). When the (1) drives the (5) to generate rotary motion relative to the (4), under the thrust of the cam groove contour, the lever pivot (7) will move in the lever guide groove, thereby changing the ratio of the lever arm.…”

“…When the (1) drives the (5) to generate rotary motion relative to the (4), under the thrust of the cam groove contour, the lever pivot (7) will move in the lever guide groove, thereby changing the ratio of the lever arm. The components of the elastic output module with independent assembly structure designed include the pin shafts ( 6) and ( 9), the lever mounting base ( 8), the lever (10), the lower end cover of the elastic output module (11), the spring guide shaft ( 12), the sliding block (13), the spring deformation limit sleeve ( 14), the linear compression spring (15) and the upper end cover of spring (16). The overall assembly structure of the elastic output module is shown in Figure 18 (f).…”

“…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.…”