Application of Quaternion Interpolation (SLERP) to the Orientation Control of 6-Axis Articulated Robot using LabVIEW and RecurDyn

In general, the orientation interpolation of industrial robots has been done based on Euler angle system which can result in singular point (so-called Gimbal Lock). However, quaternion interpolation has the advantage of natural (specifically smooth) orientation interpolation without Gimbal Lock. This paper presents the application of quaternion interpolation, specifically Spherical Linear IntERPolation (in short, SLERP), to the orientation control of the 6-Axis articulated robot (RS2) using LabVIEW and RecurDyn. For the comparison of SLERP with linear Euler interpolation in view of smooth movement (profile) of joint angles (toqrues), the two methods are dynamically simulated on RS2 by using both LabVIEW and RecurDyn. Finally our original work, specifically the implementation of SLERP and linear Euler interpolation on the actual robot, i.e. RS2, is done using LabVIEW motion control tool kit. The SLERP orientation control is shown to be effective in terms of smooth joint motion and torque when compared to a conventional (linear) Euler interpolation.