Preliminary experiments on robotic assembly using a hybrid-type variable stiffness actuator

Precision robotic assembly requires compliant motion to avoid jamming or wedging. To achieve compliant motion, impedance control and a passive compliance device, such as a RCC (remote center compliance) device, have been used in robotic assembly. However, impedance control cannot provide low impedance for the high-frequency range, and load capacity and allowable misalignment of the RCC device are limited. To cope with these problems, we propose to use a variable stiffness actuator in robotic assembly. The 3-DOF manipulator including two HVSAs was developed, and the experiments on robotic assembly were carried out. Two HVSAs provide low impedance to compensate for the lateral and angular errors between the assembly parts. To show the advantages of the HVSA-actuated manipulator over the force-controlled manipulator, we conducted comparison experiments on robotic assembly with the 6-DOF robot manipulator which was controlled by an impedance controller. A series of experiments show that the HVSA-actuated manipulator is more beneficial to execute the tasks requiring both fast motion for high efficiency and low impedance for operational safety.