Analysis and Visualisation of the Positioning Accuracy and Underlying Effects of Industrial Robots

Abstract

Industrial robots are usually not suitable for high-precision applications due to their limited absolute accuracy. This issue can be solved by calibrating the robot using an adequate model of its kinematic chain and physical behaviour. However, this presupposes a deep understanding of the effects that influence the absolute accuracy and repeatability of the robot. This paper outlines a set of experiments to gain this knowledge by analysing the effects that limit the precision and furthermore presents a way for the proper visualisation of the consequent errors. The investigation includes a range of robots with different characteristics to gather valid and preferably universal information for off-the-shelf industrial robots.

An Angle Error Compensation Method Based on Harmonic Analysis for Integrated Joint Modules

“…The amplitude-order diagram in Figure 6 directly shows that the harmonic orders having greater impacts on angle error in joint module a are orders 1, 8, 14 and 16. The harmonic orders having greater impacts on angle error in joint module b are orders 0, 1,4,8,14,16. Some controversial orders must be judged in conjunction with subsequent phase changes.…”

“…Combined with orders of large amplitude, it is finally determined that only orders 1,4,8,12,14,15,16 are retained in the error model. The phase variations of orders 1, 4, 6, 7, 8, 12, 14 and 16 of joint module b are also small; combined with orders of large amplitude, it is finally determined that orders 0, 1,4,7,8,12,14,16 are retained in the error model. Therefore, the harmonic expressions of the angle errors of joint modules a and b can be expressed as To reduce the impact of accidental error, after averaging the amplitude and phase of five groups of error data, the final error compensation models are as follows Theoretically, system errors such as eccentric error generally do not change with time and neither do the amplitudes and phases of the corresponding harmonic orders that they cause [36].…”

“…Among them, the phase variations of orders 4, 8, 12, 14, 15 and 16 of joint module a are small at approximately 10 • . Combined with orders of large amplitude, it is finally determined that only orders 1,4,8,12,14,15,16 are retained in the error model. The phase variations of orders 1, 4, 6, 7, 8, 12, 14 and 16 of joint module b are also small; combined with orders of large amplitude, it is finally determined that orders 0, 1,4,7,8,12,14,16 are retained in the error model.…”

“…The accuracy of the industrial manipulator can be divided into absolute positioning accuracy and repetitive positioning Sensors 2020, 20 accuracy. Most manipulators have excellent repetitive positioning accuracy, but still currently lack absolute positioning accuracy [8]. Existing research methods for improving the manipulator absolute positioning accuracy are divided into two types: off-line and on-line error compensation [9].…”

Analysis of non-geometric accuracy effects of articulated robots

“…The accuracy of robots can be classified in the repeatability accuracy and the pose accuracy defined in ISO 8373 (DIN ISO 8373, 2012/2013). Typical industrial robots have a high repeatability accuracy in the order of 10 μm (Ulrich et al , 2014). According to Wiest, this can be realised by a high-gear transmission and a high resolution of the resolvers (Wiest, 2001).…”