Design of a robust controller for a rotary motion control system: disturbance compensation approach
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TECHNICAL PAPER
Design of a robust controller for a rotary motion control system: disturbance compensation approach Ho Seong Lee1
•
Seonghyun Ryu1
Received: 28 October 2020 / Accepted: 3 November 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper proposes a design of a robust controller for a rotary motion control system that includes a PID controller, a disturbance observer, and a friction compensator. Friction force versus angular velocity has been measured, and viscous, Coulomb friction and stiction components have been identified. With nominal PID (proportional- integral-derivative) controller, we have observed adverse effects due to friction such as excessive steady-state errors, oscillations, and limitcycles. By adding a friction model as an augmented nonlinear dynamics of a plant, we are able to conduct a simulation study of a motion control system that matches very well with experimental results. The disturbance observer (DOB) based on simple and effective robust control theory has been implemented to make the rotary motion control system ‘‘robust’’ against inertia/load variations, external torque disturbances, and some of friction forces. Further performance enhancement of the DOB-based robust motion control system has been achieved by adding the friction compensator and experimentally verified.
1 Introduction A high performance motion controller is a key element of manufacturing equipment such as machine tools, robots, semiconductor processing tools, data storage devices and autonomous vehicles. Figure 1 shows a block diagram of a typical motion control system with four exogenous inputs that includes three external disturbances. They are external force/torque disturbances, w(t), external position disturbances, d(t), and electrical noises, n(t). In order to cancel or minimize the adverse effect of these disturbances, either a purpose-driven controller can be added, or controller optimization based on the loop-shaping can be implemented (Lee 2001; Shim et al. 2004). However, even with these specialized control efforts, the motion control system exhibits undesirable behavior such as stick–slip limit cycles, quadrant glitches, hysteresis, and/ or tracking errors due to non-linear friction components. Armstrong-Helouvry et al. (1994) did comprehensive study
& Ho Seong Lee [email protected] 1
Department of Mechanical Convergence Engineering, Gyeongsang National University, GNU Changwon Campus #303, Uichang-gu Charyong-ro 54-48, Changwon-si, Gyeongnam 51391, South Korea
on the analysis, modeling and compensation of friction. A typical friction model includes viscous and Coulomb friction. For high precision motion control with low velocity and multiple zero-velocity crossings, more elaborate friction model and compensation is required (Canudas de Wit et al. 1995; Dupont and Dunlap 1995). In order to mitigate adverse effect of friction, various control algorithms have been proposed and implemented such as dither, impulsive con
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