We formulate a predictor-based controller for a high-DOF manipulator to compensate a time-invariant input delay during a pick-and-place task. Robot manipulators are widely used in tele-manipulation systems on the account of their reliable, fast, and precise motions while they are subject to large delays. Using common control algorithms on such delay systems can cause not only poor control performance, but also catastrophic instability in engineering applications. Therefore, delays need to be compensated in designing robust control laws. As a case study, we focus on a 7-DOF Baxter manipulator subject to three different input delays. First, delay-free dynamic equations of the Baxter manipulator are derived using the Lagrangian method. Then, we formulate a predictor-based controller, in the presence of input delay, in order to track desired trajectories. Finally, the effects of input delays in the absence of a robust predictor are investigated, and then the performance of the predictor-based controller is experimentally evaluated to reveal robustness of the algorithm formulated. Simulation and experimental results demonstrate that the predictor-based controller effectively compensates input delays and achieves closed-loop stability.
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Modeling and Control of 2-DOF Dielectric Elastomer Diaphragm Actuator
In optical systems, reflectors are commonly used for directing light beams to desired directions. In this paper, a dielectric elastomer (DE) based optical manipulator is developed for two degrees-of-freedom (2-DOF) manipulation. The DE manipulator consists of a diaphragm with four segments that are controlled in two pairs, thus generating 2-DOF tilting motions. Due to its soft and gear-less moving structure, the DE manipulator is lightweight and naturally resistant to mechanical vibrations. Moreover, its nonelectromagnetic-driven mechanism allows it to work under the environments that are exposed to strong magnetic fields. To design a robust control strategy for the actuator, a physics-based and control-oriented nonlinear model is then developed and linearized around the equilibrium point. A feedback control system, which consists of two H-infinity controls, is developed to track two tilting angles along two axes. Experimental results have shown that this manipulator is able to track 0.3° 2-DOF tilting angle with 0.03° accuracy.
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- Award ID(s):
- 1747855
- NSF-PAR ID:
- 10087410
- Date Published:
- Journal Name:
- IEEE/ASME Transactions on Mechatronics
- Volume:
- 24
- Issue:
- 1
- ISSN:
- 1083-4435
- Page Range / eLocation ID:
- 1 to 1
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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