Research On The Power Assistive Exoskeleton System Driven By Pneumatic Muscles

The exoskeleton device is a kind of wearable equipment, which is a combination of human intelligence and mechanical energy of robot. It’s widely used to provide some help for the wearer in military, medical and disaster relief, etc. Compared to the motor and hydraulic actuator, pneumatic artificial muscle(PAM) is a new type of pneumatic actuator possessing high power-to-weight ratio, high power-to-volume ratio、fast response speed、low cost、safe and reliable、clean and significant similarities with our body muscle. Due to its excellent properties, more and more researchers have focused on it. Now, exoskeletons based on PAM are mostly body part recovery mechanisms and upper limb power assisted mechanisms at home and broad. In this paper, the first attempt is made to study the whole body power assistive exoskeleton system driven by pneumatic muscles, which further deepens the application of pneumatic muscle.In this paper, the PAM is used as the driver, and we have studied some key technologies of the exoskeleton, including mechanism design of the whole body exoskeleton device, establishment of mathematical model of the PAM, nonlinear control research of the PAM, kinematic and dynamic theoretical analysis, experiment of carrying capacity of upper limb and research of lower limb working control strategy,etc. The basic study of the whole body exoskeleton is completed. The main content of paper is as follows:First of all, a human body coordinate system is established, and the motion forms of each joint are analyzed. By using the method of personification design, the mechanism design of the whole body exoskeleton is completed.Secondly, mechanics characteristics of pneumatic muscle was investigated by building a test platform. According to the experimental data, the polynomial fitting model of pneumatic muscle was established. In view of the strong nonlinearity of the pneumatic muscle, a sliding mode controller based on the differentiator is designed to control the PAM to track the sinusoidal position signal in the case of different loads. And the experiment results verify the effectiveness of the proposed controller.Thirdly, the kinematic coordinate system of the upper limb and lower limb are established separately. On this basis, the forward and inverse solutions of kinematics of the upper limb and lower limb are solved. According to the Lagrange equation and the principle of virtual work, the dynamic equations of upper limb and lower limb was established.And the 3D simulation software (ADAMS) is used to carry out walking simulation.In the end, the experiment platform of the power assistive exoskeleton system is established. On this basis, we test load capacity of the upper arm. Then, in the course of flat walking, the change law of foot forces and joint angles are tested and analyzed. Then,we design the control strategy of man-machine cooperation of the power assistive exoskeleton system, and carry out the single leg gait control experiment successfully.