Reaching for redundant arms with human-like motion and compliance properties

• Novel controller for target reaching of redundant arms without trajectory planning.
• The model-free control scheme guarantees desired completion time and accuracy.
• Smooth natural reaching and configuration consistency in return motions.
• Active compliance via admittance control for physical human–robot interaction.
• Simulation and experimental results demonstrate human-like motion and compliance.

This work proposes a redundant arm torque controller for reaching, guaranteeing desired completion time and accuracy requirements without the need for trajectory planning and prior knowledge of robot dynamics. The proposed controller is designed based on the prescribed performance control methodology and it is a reaching regulator in which the target pose for the hand acts as an attractor for the arm. It provides configuration consistency in return motions and hand and joint velocity smoothness. Its use in an admittance control scheme given measurements or estimates of external forces is also proposed providing active compliance capabilities in robot–environment interactions. Simulation studies for a 5dof human arm-like robot and experiments with a 7dof arm are performed to verify the approach and demonstrate the proposed controller’s performance.