Abstract
This study determines the practicality and feasibility of the application of pneumatic artificial muscles (PAMs) in a pneumatic therapy robotic system. The novel mechanism consists of a single actuated pneumatic artificial muscle (single-PAM) robotic lower limb that is driven by only one PAM combined with a torsion spring. Unlike most of previous studies, which used dual-actuated pneumatic artificial muscles (dual-PAMs) to drive joints, this design aims to develop a novel single-PAM for a one degree-of-freedom (1-DOF) robotic lower-limb system with the advantage of a mechanism for developing a multi-axial therapy robotic system. The lower limb robotic assisting system uses the stretching/contraction characteristics of a single-PAM and the torsion spring designed by the mechanism to realize joint position control. The joint is driven by a single-PAM controlled by a proportional pressure valve, a designed 1-DOF lower-limb robotic system, and an experimental prototype system similar to human lower limbs are established. However, the non-linear behavior, high hysteresis, low damping and time-variant characteristics for a PAM with a torsion spring still limits its controllability. In order to control the system, a fuzzy sliding mode controller (FSMC) is used to control the path tracking for the PAM for the first time. This control method prevents approximation errors, disturbances, un-modeled dynamics and ensures positioning performance for the whole system. Consequently, from the various experimental results, the control response designed by the joint torsion spring mechanism can also obtain the control response like the design of the double-PAMs mechanism, which proves that the innovative single-PAM with torsion spring mechanism design in this study can reduce the size of the overall aid mechanism and reduce the manufacturing cost, can also improve the portability and convenience required for the wearable accessory, and is more suitable for the portable rehabilitation aid system architecture.
Highlights
Rehabilitation robots have increasingly become popular in the field of robotics, since they can provide a support for patients with impaired limbs or elders facing difficulties doing activities of daily living on their own, and augment the power of able-bodied people
This study proposes a 1-DOF robotic lower limb system that is driven by a novel single-pneumatic artificial muscles (PAMs) joint mechanism combined a single-PAM with a torsion spring
In order to drive a joint, this study proposes an innovative single-PAM with a torsion spring mechanism design, the stretching and contraction actuation of the PAM drives the torsion spring parallel to the joint to simulate the flexion and extension of the human joint antagonist muscle
Summary
Rehabilitation robots have increasingly become popular in the field of robotics, since they can provide a support for patients with impaired limbs or elders facing difficulties doing activities of daily living on their own, and augment the power of able-bodied people. Pneumatic artificial muscles (PAMs) may be the most promising due to their inherent compliance, which guarantees safe interactions between the operator and the device. High power-to-weight ratio and lightness are ideal features for the applications of human-friendly devices. The non-linearity is the drawback that is required to mitigate for accurate control. Many countries have studied a new type of PAM actuator for industrial applications and robotics. In the 1960s, this was invented by an American doctor, Joseph L.
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