Design, prototyping and test of a seven-degree-of-freedom humanoid pneumatic robotic arm

This thesis presents design, kinematic analysis, prototyping and performance evaluation of a novel seven degree-of-freedom pneumatically-actuated robotic arm. The developed arm is similar, in size and performance, to a human arm.; The seven degree-of-freedom robotic arm consists of upperarm, forearm and hand that are linked serially. The upperarm has a parallel link configuration. To actuate the arm, pneumatic cylinders are used. Compliance of pneumatic cylinders is an asset but control of them is challenging. For supporting the two degrees of freedom of upperarm in shoulder, three parallel links of the upperarm are connected to the fixed frame of the shoulder by three universal joints, which are designed to create a large workspace. These universal joints form a right angle coordinate system. Two parallel links of the upperarm have revolute-prismatic-revolute configuration, and the third link has revolute-revolute-revolute configuration. A one degree of freedom cylindrical joint is supporting one more degree of freedom for the upperarm to duplicate the radial movement of the human upperarm. A low friction and light weight transmission is designed to add to a pneumatic cylinder and create a revolute-revolute-revolute link for central link of the upperarm. The forearm has parallel link configuration with two parallel links. One of the forearm links to copy the radial movement of the human forearm has revolute-prismatic-revolute configuration and the second one same as central link of the upperarm has a revolute-revolute-revolute configuration to copy the rotational movement of the human forearm. The hand has the same pattern of upperarm, except the central link of the hand is just a solid link. The kinematic of the seven degree-of-freedom robotic arm is analyzed. Analytical relation between angles of major revolute joints to the orientation and position of the tip of the hand as the end effector position are calculated. Jacobean matrix of the design is calculated to show an analytical relation between the rate of changes of joint angles to time and six speed elements of the end effector. Prototype of the arm has been built in order to show the functionality of the arm.; The robot is powered by pneumatic cylinders and operated by servovalves, encoders, amplifier boards, and was interfaced to a computer by a data acquisition board. A potentiometer voltage controller unit is built to demonstrate the functionality of the robot. The response of every actuator to a unique control signal is traced, by encoders, and curves are saved.