Accurate force reflection method for a multi-d.o.f. haptic interface using instantaneous restriction space without a force sensor in an unstructured environment

Abstract

This paper proposes an accurate force reflection method for a multi-d.o.f. haptic interface without a force sensor. Sensorless force reflection is possible using position–position (p–p) architecture. However, the conventional p–p architecture in the literature has limitations representing constraint space when it is applied to a multi-d.o.f. haptic interface in that it gives an inaccurate force direction. This paper demonstrates the limitation of the conventional p–p architecture through an example and proposes a novel force reflection method using the instantaneous restriction space (IRS) concept. The IRS can be calculated using the Jacobian and joint angle error of a slave manipulator. Since the proposed method has the form of an impedance two-port architecture in the sense of data flow, it can be easily combined with previous well-known results of two-port haptic display frameworks. The proposed method is especially useful when the slave manipulator collides with unexpected obstacles during motion, even though the slave does not have a force sensor. The performance of the proposed method is evaluated through experiments.