Optimal Impedance Control of A 2R Planar Robot Manipulator

In this study, the energy consumptions of input trajectory functions on an impedance controlled 2R planar robot manipulator were compared. Industrial applications of robot manipulators often relate to manipulation tasks such as painting that only require arm position control. However, in the presence of elements that may come between the robot and the environment during these operations, the robot must not harm itself and the other entities in contact. There are also robotic tasks that require interaction between the robot manipulator and a contact surface or environment, such as pushing, polishing, cleaning and grinding. This fact makes it imperative to control the interaction between the robot and the environment. The impedance controller aims to control the dynamic relationship between the robot and the environment. The force applied by the robot to the environment depends on the position of the robot manipulator endpoint and the corresponding impedance. The impedance controller forces the robot manipulator endpoint to follow the desired reference or target impedance. The input trajectory function in impedance control has a direct effect on the interaction distance of the impedance force and thus on the interaction force. Impedance forces also affect the torques in the joints. Therefore, the input trajectory function directly affects the energy consumed by the robot. In this study, The Bees Algorithm was used to optimize the impedance controller parameters to reduce the positioning error below a certain level for each input trajectory function, including step, ramp, polynomial, sinusoidal and sigmoid input functions. As a result of the optimization, the energy consumptions of the input trajectory functions were compared. Obtained results are presented numerically and graphically. The advantages and disadvantages of the input trajectory functions were discussed.