Towards variable impedance assembly: The VSA peg-in-hole

This paper shows how an accurate peg-in-hole assembly task can be easily achieved with nothing but cheap position sensors when resourcing to Variable Impedance Actuators (VIA). We present the use of a low-cost Variable Stiffness Torso platform, that consists of two 4-DOF non-planar VSA manipulators, for a peg-in-hole assembly task using both arms. One arm holds the peg and the other holds the hole. The task is accomplished without any force measurement and without calling for parallel-manipulator control techniques, exploiting the intrinsic mechanical elasticity of the actuator units. Indeed, a simple position control scheme is required. Simulations and experimental results are reported.