Abstract
Repetitive and intensive physiotherapy is indispensable to patients with ankle disabilities. Increasingly robot-assisted technology has been employed in the treatment to reduce the burden of the therapists and the related costs of the patients. This paper proposes a configuration of a wearable parallel mechanism to supplement the equipment selection for ankle rehabilitation. The kinematic analysis, i.e., the inverse position solution and Jacobian matrices, is elaborated. Several performance indices, including the reachable workspace index, motion isotropy index, force transfer index, and maximum torque index, are developed based on the derived kinematic solution. Moreover, according to the proposed kinematic configuration and wearable design concept, the mechanical structure that contains a basic machine-drive system and a multi-model position/force data collection system is designed in detail. Finally, the results of the performance evaluation indicate that the wearable parallel robot possesses sufficient motion isotropy, high force transfer performance, and large maximum torque performance within a large workspace that can cover all possible range of motion of human ankle complex, and is suitable for ankle rehabilitation.
Highlights
As the population ages, increasingly more individuals experience ankle disabilities caused by stroke and cerebral palsy, which may lead to lack of mobilization, irregular pain of body, insufficient capacity to support weight, and chronic joint instability
An adjustable lowerlimb binding mechanism is established between the supporting column to maintain the stability of the lower-limb during rehabilitation and accommodate patients with different body sizes (Figure 5), double linear guide rails with double-slider, single-connection platform and locking function are employed to fix the thigh and adjust the up/down position of the patient, while the calf is fixed by a special leg holder and its forward/backward position can be fine-tuned by single linear guide rail with singleslider and locking function
Two linear actuators (CAHB-10, SKF, Sweden) are employed as joint P1 and P2 to adjust the lengths of the kinematic branches from 413 to 713 mm
Summary
Increasingly more individuals experience ankle disabilities caused by stroke and cerebral palsy, which may lead to lack of mobilization, irregular pain of body, insufficient capacity to support weight, and chronic joint instability. During the conventional manually physiotherapy, human ankle complex (HAC) is moved by a physical therapist with its range of motion (ROM) It possesses many limitations such as, the duration inconsistency and frequency indetermination of the treatment procedures, the physical demand, and experience requirement of the therapist, and the subjective evaluation of the therapeutic results (Meng et al, 2015; Hussain et al, 2017). In view of this situation, to provide high-quality rehabilitation treatment with repetitive sessions, quantitative measurements, scientifical therapy, and systematic operation, robot-assisted rehabilitation has become a field that receives more, and more research attention. Directly aligning several types of actuators, including rotating actuator assembly (Ren et al, 2017), servo motor (Yoshizawa, 2010; Yao et al, 2018) and bidirectional pneumatic actuator (Shorter et al, 2011), to the joint axis is another option for researchers
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