Modelling and Control of a Hybrid Robotic Arm with Mixed Rigid-Elastic Joints

Traditional rigid joints exhibit good accuracy in position control but come at the expense of high interaction forces. Elastic joints, on the other hand, can limit the interaction forces but have poor position control accuracy and slow response times. Thus, combining both rigid and elastic joints in a robot arm can leverage their respective strengths while mitigating their weaknesses. In this paper, a mathematical model for a three degrees of freedom (DOFs) hybrid robotic arm with mixed rigid-elastic joints is introduced in detail. The first two joints are rigid, while the last one is elastic. The last joint is chosen to be elastic because it is the one that directly interacts with the environment, potentially including interactions with humans. This can help limit the interaction forces. Furthermore, an inverse dynamics control approach for this hybrid robotic arm is proposed. Finally, a simulation is carried out to demonstrate the efficiency of the proposed control algorithm.