Research On Bidirectional Bending Active Pneumatic Flexible Joints And Its Application In Robot Hand

Active joint is the key component of the biomimetic robot, and its structure characteristic, movements, mechanics, drive capability and control method determine the functions and application of the machine product. With the development of robotics, especially spread to fabricating industry, logistics, service and military affairs with unprecedented speed, people put forward higher request to the performance of the robot and propel a challenge for the structural flexibility, compliance, gentle drive and soft control. It is an urgent task to develop the biomimetic joints with integration flexibility, which can adapt to the change of environment and operational objectives.Many researchers have yielded important information on the problems of flexible joints. The joints in existence with portion flexibility are mainly driven by motor, hydraulic cylinder or functional materials, in which the motor driven and the hydraulic driven have widely used in machinery and robots, but its large bulk and rigidity greatly reduce the flexibility of joints. In order to improve the flexibility and compliance of the robot hand, many researchers have developed five types of PAM (Pneumatic Artificial Muscle). The McKibben muscle is more successful to drive the flexible joint of robot than the other artificial muscles. Yet this type of joint self is still rigid, the joint with integration flexibility is not formed so far, the mechanical properties of pneumatic elastic bodies with large deformation still is to be learned.In this thesis, a new type of flexible joint was carried out base on the elongation type of pneumatic artificial muscle we developed, the structure of joint break through the traditional pattern of active joint; four PAMs in parallel compose the bidirectional active flexible joint. The drive device and the joint itself compound as one which has good flexibility, the stiffness of the joint is distributed to the spring of the PAM. The joint can bend, anti-stretch, abduce, adduct and axial elongate. The bending capability in two orthogonal principal directions which let it has good adaptability to the changes in shape.In this thesis, we creatively put forward the elongation pneumatic artificial muscle. The structure of combined the constraint spring and the rubber tube, makes it easy to adjust the parameters of spring to change the stiffness of joint for suitability. Furthermore, we discussed the operating range of the artificial muscle and restrict stability; then put forward the experimental method to judge the instability destruction in radial of the artificial muscle. To solve the torsion of PAM, we put forward the SS type cylindrical spiral spring and artificial muscle with two bodies. It indicates that the axial and bending deformation of SS type cylindrical spiral spring is linear through the finite element analysis.This thesis has theoretical and experimental analysis on its mechanical properties; studied its work principle as the variation parameter cylinder. We have analysis on the static characteristics of PAM and establish the mathematical model using deformation energy function and the classical theory of elastic deformation to solve the large and non-linear deformation problem; established the variable dynamic model of PAM applying the equivalent method of translational kinetic energy and get the natural frequency interval; studied the axial and bending deformation of the new type of flexible joint. We also did the experiments on the PAM applying the non-contact measurement.In this thesis, we built the static and dynamic model with variable parameter of the joint based on the exploration of large deformation of compound elastic body; studied the relationship between the PAM and joint; discussed the relationship between the air pressure and the bending deformation; then get its mathematical model which is verified by the experiments. In addition, we established the variation parameter dynamic model of flexible joint, and get natural frequency regularity of joint. Furthermore, we investigated on the factors to influence to grasp force, such as the drive function and the contact position of joint, air pressure, the size of joint, etc.Then we decided the control system configuration of joint, where five mode of deformation are controlled.Based on the bidirectional bending active pneumatic flexible joints, we developed the five-fingered robot hand which has a brand new structure and function. The middle finger is in middle and the other four fingers are opposite to each other, which form the grasp mode with dual-thumb and ensure the stability of grasp. We adopted the wedge plate as the connection part, and combined the anti-stretch function of the hand to improve the flexibility and the grasp range of robot hand. We introduced the large deformation non-linear variables of flexible joints to the transformation matrix using the parametric translational coordinates; get the homogeneous transformation matrix of four patterns of the finger; get the trajectory and the pose of finger when it is bending, anti-stretch, abducent and adducent using matlab; and the experiments prove the validity of the theoretical model.We did experimental analysis on the relationship between grasp force as well as the grasp position and the air pressure; moreover, we discussed the influence of flexibility to grasp force. Then we did the experiments about robot hand to grasp the object, which verified the manipulation function of robot hand. We discussed on the control requirements and its characteristic, and then form the scheme of control system, which combined the computer, controller and pneumatic control system. We propose the control method to the four type grasp mode which including twelve moments of fingers; designed the pneumatic control system and built the pneumatic table; formed the electrical control system scheme. Then we determined the details of control method of fingers and robot hand as well as the flow chart of control program.The research of this thesis provided a new solution to solve the insufficiency of flexibility of joint as so far. The results show that the bidirectional active flexible bending joint we developed has good flexibility and compliance to meet the special requirements of the biomimetic joints; and the flexible robot hand composed by this joint can complete the action and function as human being, and it has high theoretical value and broad application prospects.