The strength of a haptic display may be assessed from its range of stable impedances. This paper presents a novel passive haptic display (PARM) capable of simulating a broad range of impedances. It comprises a passive constraint that can simulate both uninhibited motion through free-space and collision into a rigid obstacle. In free-space, the user feels the natural impedance of the end-effector without the added inertia and friction from a transmission or actuator. In a collision with a rigid object, haptic stiffness can be much greater than a traditional impedance haptic display. An experimental study with a 2 DoF planar manipulator illustrates the minimum and maximum impedances that are attainable for this haptic display. The inertial mass and friction in free-space are less than 0.2 kg and 12.3 Ns/m, and the stiffness against a haptic boundary is 465 N/mm. In addition, collision with a haptic object produces a more authentic experience, since there are naturally-occurring high frequency oscillations that result from the physical collision between two objects. This novel haptic display has both the minimum impedance benefits of impedance haptic displays and the maximum impedance benefits of admittance haptic displays.

Accurate determination of robot geometric and flexibility parameters permits significant reduction of systematic errors and improved end-effector positioning accuracy. We apply a 30-parameter flexible geometric model to the Mitsubishi PA10-6CE robot and reduce mean/peak positional errors from 1.80/2.45 mm to 0.33/0.71 mm while loaded at 44 N.

This paper discusses a method to identify dynamic parameters in a rigid-link flexible-joint robot model using motion capture. The procedure is divided into two parts. First, the robot dynamics are parameterized in a new form to exclude the stiffness torque, and are solved with a rich set of data. The stiffness torque is then reconstructed from the new parameter set, and a torsional spring model is fit to the measured data. This method offers a better conditioned system of equations for weakly-flexible systems, and more flexibility in the choice of torsional spring model. The two-step identification method is experimentally evaluated on a Mitsubishi PA10-6CE.