Haptics Symposium 2014 Recap

In October 2013 we submitted a paper on A Simplified Approach to Admittance-type Haptic Device Impedance Evaluation for the IEEE Haptics Symposium to be held in March 2013. To address the challenges in evaluating the transparency, or output impedance more generally, of admittance-type haptic devices due to their inherently non-back-drivable mechanical characteristics, we have described a new, simplified evaluation approach that eliminates the need for external test fixtures.  This simplified approach relies on the easily obtainable closed-loop position control response of the device in combination with a device/system dynamic model.  In addition to evaluating output impedance, the approach can be used of evaluate the overall stable rendering range of the device. Finally, we have also discussed the limitations of the approach.


Lumped-parameter model of admittance-type haptic device, including coupling to human impedance model


Block Diagram

Block diagram representation of admittance-type haptic device


Experimental frequency response of the human impedance model used

Overlaid plot of the experimental frequency response of the human impedance and the fitted model response for two different human subjects

Frequency response of the open-loop transfer function of the simplified system model , tuned to the parameters of the experimental system used.  The gain of the transfer function was adjusted by varying the virtual admittance inertia, m, such that the system was on the boundary of stability.

Output Impedance

Output impedance of example admittance-type haptic device



Comments are closed.