Experiental Robustness Evaluation of PID Controller for Position Control of a Cartesian Robot

Proportional-integral-derivative (PID) controller is one of the most efficient schemes to control the position in robotics. In this paper, the design, manufacture, and control of a Cartesian robot with three prismatic joints are investigated. At first, the design of the robot is considered, which is divided into conceptual and detailed steps. In conceptual design, for horizontal axes, considering precision and cost, belt and pulley are chosen as an appropriate means to transfer rotational movement into linear. For the vertical axis, which needs more precision and self-locking feature, nut and screw are utilized. In detailed design, material, dimensions and technical features of the robot are determined. Moreover, as stepper motors have the advantage of high precision, they are used as actuators. After manufacturing and assembling the parts of the robot, a PID controller is designed and experimentally implemented to control the position of the end-effector. In design process of the controller, the effect of PID coefficients is studied. The controller is experimentally implemented for the robot and its robustness is evaluated in the presence of disturbance, sensor noise and mass uncertainty.