Abstract
This paper developed a cable-driven three-degree-of-freedom (DOF) wrist rehabilitation exoskeleton actuated by the distributed active semi-active (DASA) system. Compared with the conventional cable-driven robots, the workspace of this robot is increased greatly by adding the rotating compensation mechanism and by optimizing the distribution of the cable attachment points. In the meanwhile, the efficiency of the cable tension is improved, and the parasitic force (the force acting on the joint along the limb) is reduced. Besides, in order to reduce the effects of compliant elements (e.g., cables or Bowden cables) between the actuators and output, and to improve the force bandwidth, we designed the DASA system composed of one geared DC motor and four magnetorheological (MR) clutches, which has low output inertia. A fast unbinding strategy is presented to ensure safety in abnormal conditions. A passive training algorithm and an assist-as-needed (AAN) algorithm were implemented to control the exoskeleton. Several experiments were conducted on both healthy and impaired subjects to test the performance and effectiveness of the proposed system for rehabilitation. The results show that the system can meet the needs of rehabilitation training for workspace and force-feedback, and provide efficient active and passive training.
Highlights
Many people suffer from movement disorders and reduced muscle strength, which are resulted in neural diseases (Stroke Center)
Many related clinical trials based on these robots have been carried out, and the results verified the effectiveness of robot-assisted rehabilitation (Reinkensmeyer et al, 2000; Lum et al, 2002; Kwakkel et al, 2008)
This paper proposed a dynamic change strategy of the cable configuration, that is, by adding a rotating compensation mechanism, the inner and outer rings of the forearm module can be relatively rotated, and the fixed cable attachments can be dynamically adjusted according to the current wrist posture
Summary
Many people suffer from movement disorders and reduced muscle strength, which are resulted in neural diseases (Stroke Center). The inertia is pretty low in all three DOFs. To improve the first two disadvantages, the rotating compensation mechanism on the forearm module is designed, and the distribution of the cable attachments can be adaptively changed, optimizing the workspace of the cable-driven robot and the tension efficiency of the cable. It is due to that the rotating compensation mechanism is used, dynamically changing the cable attachments distribution and greatly increasing the workspace and tension efficiency This is very important for rehabilitation training.
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