Design And Control Of Dextrous PMA-driven Upper Limb Exoskeleton

In daily life,workers and peasants often carry out some repetitive and boring labor,and military personnel often carry heavy objects such as shells,guns,and supplies.People in the above occupations often work under a certain amount of labor for a long time,which is easy to cause physical fatigue and serious physical damage.Therefore,people need a wearable robot to assist in work to improve work efficiency and quality of life.Exoskeleton robots provide the wearer with functions such as protection,body support,etc.,and can perform certain functions and tasks under the control of the operator.Exoskeleton robots can combine robot support,protection,movement and other characteristics with human intelligence to achieve higher work efficiency.Therefore,it has great application value in the fields of power assisting mechanism,auxiliary medical equipment,and individual military operations.This paper presents a PMA(Pneumatic Muscle Actuator)driven smart upper limb exoskeleton robot.Its structure and the structure of the upper limbs of the human body have a high degree of similarity.The shoulder joint uses a parallel structure based on a universal joint and a bearing.This design achieves a three-degree-of-freedom movement of the shoulder joint and a high degree of similarity to the spherical joint of the human body.The driving muscles of the shoulder joint are located on the back bracket,making it more compact.The elbow joint is mainly driven by two PMAs in series to achieve single-degree-of-freedom driving.This design overcomes the shortcomings of the PMA.installation space.The elbow joint is equipped with fixed wheels(fan-shaped and with guide rails),which makes sure the PMA can still supply sufficient torque at extreme angles.Based on the work of predecessors,this paper improves the method of making PMAs.And the micro force sensor is integrated on the plugs of the PMA,which can detect the force of the PMA in real time,and it is convenient to control the PMA more accurately.In order to study the static characteristics of PMA,this paper builds an automated experimental platform for testing PMA performance.Based on the test data,a mathematical model between the air pressure,force and contraction of the PMA was established.Based on the geometry of the shoulder joint,this paper uses the quaternion method to establish the geometric model of the shoulder joint,and uses the mechanical equilibrium equation to establish the equation between the three PMAs forces and the external moment of the parallel shoulder joint.Finally,the inverse dynamics model of the upper extremity exoskeleton was established by using the Lagrangian equation.In order to reduce the difficulty of control experiment and improve the research efficiency of control algorithm,this paper builds a semi-physical simulation platform for the upper extremity exoskeleton.The physical platform construction part includes pneumatic circuit design,sensing system design,selection and testing of various components,while the upper limb exoskeleton controller is realized in MATLAB/Simulink software in PC.In this paper,a feedforward closed-loop control method based on PMA model is proposed,and the feasibility and effectiveness of the control algorithm are verified in single joint experiments and joint experiments of upper limbs.