Modeling and Control of Four-bar Mechanism with Series Elastic Actuators

  • Felipe R. Lopes Pontifícia Universidade Católica do Rio de Janeiro
  • Marco A. Meggiolaro Pontifícia Universidade Católica do Rio de Janeiro
Keywords: Robot control, Human-robot interaction, Series elastic actuator, Four-bar mechanism, Linear control


A new generation of robots that work in cooperation with humans (called collaborative robots) needs some flexibility to adapt to the environment and activities with people. That is why the Series Elastic Actuator (SEA) has been a breakthrough in actuator technologies. The idea of inserting an elastic element in series with a motor allows a lower output impedance, consequently a flexible behavior in the manipulator, in addition to providing torque feedback to better compensate disturbances caused e.g. by friction losses. This article presents a four-bar mechanism with SEA for the purpose of robotic manipulation. Its kinematics and dynamics
are studied, as well as its regulation and trajectory control. The behavior of the decoupled four-bar mechanism and the characteristics of the SEA are also analyzed. Then the regulation control of the complete system is carried out using LQR control. Finally, a circular trajectory is controlled in a simulation to validate the proposed control strategy. The simulation results show the effectiveness of the proposed controller for the mechanism in the presence of SEAs estimating torque and providing the desired compliance for human interaction.