Nonlinear dynamics and control of a spatial high speed composite material flexible robot arm

The focus of this research is to amend the end-effector positional accuracy of high-speed, lightweight, flexible robotic manipulators. The problem arises from the undesirable structural static and dynamic deflections. In previous works some improvements on reducing the residual vibration of the end-effector were obtained by concentrating either on an adequate structural design of the manipulator's links or implementing advanced control techniques. However, no effort has been made to take a more aggressive approach, which simultaneously improves the controller and the structural design and accommodates for the relationships with which they interact.; This study demonstrates the enhancement achieved by active and passive compensations of the end-effector static and dynamic deflections of the tip of a flexible robot arm. The passive compensation is accomplished by constructing the flexible link from advanced composite materials. The active compensation is done by using a nonlinear control technique whose control law includes the dynamics and flexibility of the manipulator.; Hamilton's principle is used to derive the equations of motion of a three-degree-of-freedom, revolute manipulator. The last link of the robotic manipulator is considered to be flexible and is constructed from either aluminum or graphite/epoxy. All the coupling terms between the rigid and flexible motions of the arms are maintained. The displacement field is based on Eluer-Bernoulli beam theory and a nonlinear strain field is considered. A displacement finite element is implemented to approximate the solutions. Material damping for the graphite/epoxy arm is included in the model. Linear controller as well as nonlinear controller (computed torque method) with PID compensators are implemented to control the vibration of the tip of the manipulator. To damp the excess vibration of the arm, two actuating forces are applied at the tip of the last link. These forces are implemented in the nonlinear control law.; Digital simulations are performed to investigate the dynamic behavior and control response of a fast, and lightweight manipulator. Comparisons are made between the dynamic behavior of robot arms fabricated from conventional metallic materials (e.g., aluminum) and advanced composite materials (e.g. graphite/epoxy) to demonstrate the excess accuracy gained by the use of composite materials. The results of implementation of different controllers and their effect on links constructed from either aluminum or graphite/epoxy are analyzed.; This research contributes an understanding of basic dynamic behavior and control of accurate, lightweight, and fast robotic manipulators constructed from advanced composite materials.