Experiment on the Control of a Flexible Parallel Manipulator

The modeling and controlling of a flexible parallel manipulator are investigated. Although the energy consumption of light weight robots is less than of other robots, they have also disadvantages such as a significant flexibility yielding vibration and elastic deformation. Therefore, a motion compensator for increasing the accuracy of a flexible link position should be designed. The robot modeling is the first step for designing a controller. Hence, the structure of the flexible link is modeled using model reduction. Second, electrical and mechanical components are considered. Finally, an appropriate controller is designed for trajectory tracking while the flexible links are underactuated. The flexible robot in Lambda configuration has a highly flexible link as a long link and a short modestly flexible link. The end of short link is jointed to the middle of long link with a rigid body. The robot has two prismatic actuators connecting the links to the ground. Model reduction is utilized in order to model the robot and the best model is chosen. Then, the controller based on the best model is designed. The controller is separated into two parts, one offline and one online. All constraints of the system are considered in the offline part of the controller. Then, the offline part is used for designing the online part of controller. The online part of the controller includes feedforward and feedback. The feedforward controller is used for overcoming undesired movement and stabilizing the systems. The feedback controller is used for trajectory tracking. A Kalman filter for decreasing the disturbances is applied. Finally, the trajectory tracking of the flexible robot based on an elastic model and a rigid model are compared. The results show that the trajectory tracking of the flexible robot based on the elastic model is more accurate than that of the rigid model.