Accurate transmission performance evaluation of servo-mechanisms for robots. (December 2022)

• Record Type: Journal Article
• Authors: Bilancia, Pietro; Monari, Luca; Raffaeli, Roberto; Peruzzini, Margherita; Pellicciari, Marcello
• Is Part Of: Robotics and computer-integrated manufacturing. Volume 78(2022)
• Publication Date: 2022-12
• Subjects: Test rig -- Experimental methods -- Servo-mechanisms -- Robot reducers -- Torque ripples -- Transmission error -- Lubricant temperature; Robots, Industrial -- Periodicals; Computer integrated manufacturing systems -- Periodicals; Robotics -- Periodicals; Robots industriels -- Périodiques; Productique -- Périodiques; Robotique -- Périodiques; 670.285
• DOI: 10.1016/j.rcim.2022.102400
• Languages: English
• ISSNs: 0736-5845

Abstract

Abstract: The Servo-Mechanisms (SMs) mounted in industrial robots joints are a major source of positioning accuracy errors. To improve robots precision performance, researchers have been focusing on the development of novel SMs design and control strategies, which need extensive experimental analyses to tune their parameters. In this context, the scope of this paper is double: first, to present the novel experimental apparatus and methods designed to improve the accuracy of the transmission performance evaluation of high dynamics SMs and, secondly, to report and discuss the achieved experimental results. In the first part, a description of the test rig tuning operations is given, primarily focusing on the signals synchronization and on the elimination of the measuring errors caused by the mechanical transmission elasticity and the servomotor torque ripples. Then, control strategies for compensating the torque ripples and input speed errors are defined. It is shown that speed oscillations can be reduced of ≈ 70 % when rotating the servomotor up to 2000 rpm, improving the measurement quality of the reducer performance. In the second part, a set of experiments is carried out to assess the combined effect of input speed and lubricant temperature on the reducer behavior. The system sensitivity to the variation of the input parameters is confirmed by the dynamic lost motion curves, whose mean value equals 16 . 8 ″ and 35 . 4 ″ when the reducer is operated at its minimum and maximum friction load respectively. At last, the extrapolated harmonic content is used to build a simple mathematical model of the reducer transmission error. Highlights: Methods employed to assess the performance of modern servo-mechanisms are reported. Practical guidelines for improving the measurements quality are proposed. The effect of oil temperature and input speed on the reducer is assessed. A model of the reducer transmission error is derived from the measured data.