Design and control strategy of humanoid lower limb exoskeleton driven by pneumatic artificial muscles

This paper firstly introduces a humanoid lower limb exoskeleton (HLLE) actuated by pneumatic artificial muscles. It is almost anthropomorphic and retains six degrees of freedom (DOFs) for each lower limb. Pneumatic artificial muscle (PAM) is designed and manufactured according to McKibben principle which has already been examined to acquire the basic static performance. Then, the fuzzy self-tuning PID (FSPID) control based on pulse-width modulation (PWM) is purposed to control the motion of HLLE and it is an effective strategy which does not rely on the kinetic model of the lower limb. Besides, inertial measurement units (IMUs) are installed on certain components to receive precise motion parameters timely, which aim to be able to get helpful feedback results. As the control center of the system, microcontroller unit (MCU) is mainly responsible for communicating with sensors and PC, generating PWM signals to regulate valves and dealing with data. In the application of the HLLE, an effective intelligent control strategy for lower limbs with PAMs is expected to acquire; and the research result is to be applied to the human body which is wearing HLLE in the future. As a consequence, what we have researched contributes much to the application of pneumatic artificial muscles in several fields, such as intelligent prosthesis device, medical rehabilitation exoskeleton and power-assisted exoskeleton. In the end, this paper gives an outline of the prospected work for later experimental research.