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1. Adaptive Control of a Two-Link Robot Using Batch Least-Square Identifier

   https://doi.org/10.1109/JAS.2020.1003459  

   Bagheri, Mostafa; Karafyllis, Iasson; Naseradinmousavi, Peiman; Krstic, Miroslav. (January 2021, IEEECAA journal of automatica sinica)

   Liu, Tengfei; Ou, Yan. (Ed.)

   We design a regulation-triggered adaptive controller for robot manipulators to efficiently estimate unknown parameters and to achieve asymptotic stability in the presence of coupled uncertainties. Robot manipulators are widely used in telemanipulation systems where they are subject to model and environmental uncertainties. Using conventional control algorithms on such systems can cause not only poor control performance, but also expensive computational costs and catastrophic instabilities. Therefore, system uncertainties need to be estimated through designing a computationally efficient adaptive control law. We focus on robot manipulators as an example of a highly nonlinear system. As a case study, a 2-DOF manipulator subject to four parametric uncertainties is investigated. First, the dynamic equations of the manipulator are derived, and the corresponding regressor matrix is constructed for the unknown parameters. For a general nonlinear system, a theorem is presented to guarantee the asymptotic stability of the system and the convergence of parameters’ estimations. Finally, simulation results are discussed for a two-link manipulator, and the performance of the proposed scheme is thoroughly evaluated. 

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2. A Haptic Interface for the Teleoperation of Extensible Continuum Manipulators

   https://doi.org/10.1109/LRA.2020.2970642  

   C.G. Frazelle, A.D. Kapadia (April 2020, IEEE robotics automation letters)

   We describe a novel haptic interface designed specifically for the teleoperation of extensible continuum manipulators. The proposed device is based off of, and extends to the haptic domain, a kinematically similar input device for continuum manipulators called the MiniOct. This letter describes the physical design of the new device, the method of creating impedance-type haptic feedback to users, and some of the requirements for implementing this device in a bilateral teleoperation scheme for continuum robots. We report a series of initial experiments to validate the operation of the system, including simulated and real-time conditions. The experimental results show that a user can identify the direction of planar obstacles from the feedback for both virtual and physical environments. Finally, we discuss the challenges for providing feedback to an operator about the state of a teleoperated continuum manipulator. 

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3. Homotopy Continuation for Feedback Linearization of Noncontact Magnetic Manipulators

   https://doi.org/10.23919/ACC45564.2020.9147681  

   Riahi, Nayereh; Tituana, Luis R.; Komaee, Arash (July 2020, 2020 American Control Conference (ACC))

   null (Ed.)

   Magnetic fields render a unique ability to control magnetic objects without a direct mechanical contact. To exploit this potential for a broad range of medical, microrobotics, and microfluidics applications, noncontact magnetic manipulators have been designed using both electromagnets and permanent magnets. By feedback control of these manipulators, magnetic objects can be precisely driven in the directions required by an application of interest. The feedback design process for these manipulators is normally complicated by their highly nonlinear nature, particularly for those utilizing permanent magnets. Yet, feedback linearization techniques can be applied to compensate for the nonlinear nature of most magnetic manipulators. This goal can be achieved by solving an underdetermined system of nonlinear algebraic equations. This paper adopts a homotopy continuation approach to solve this system of equations. It is shown by simulations that the proposed feedback linearization scheme drastically improves the control performance compared to the alternative control design methods used in prior work. 

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4. AFREEs: Active Fiber Reinforced Elastomeric Enclosures

   https://doi.org/10.1109/RoboSoft48309.2020.9115988  

   Yoshida, Kyle T.; Ren, Xinyi; Blumenschein, Laura H.; Okamura, Allison M.; Luo, Ming (May 2020, IEEE International Conference on Soft Robotics (RoboSoft))

   Soft continuum manipulators provide a safe alternative to traditional rigid manipulators, because their bodies can absorb and distribute contact forces. Soft manipulators have near infinite potential degrees of freedom, but a limited number of control inputs. This underactuation means soft continuum manipulators often lack either the controllability or the dexterity to achieve desired tasks. In this work, we present an extension of McKibben actuators, which have well-known models, that increases the controllable degrees of freedom using active reconfiguration of the constraining fibers. These Active Fiber Reinforced Elastomeric Enclosures (AFREEs) preform some combination of length change and twisting, depending on the fiber configuration. Experimental results shows that by changing the fiber angles within a range of -30 to 30 degrees and actuating the resulting configuration between 10.3 kPa and 24.1 kPa, we can achieve twists between ± 60 degrees and displacements between -2 and 4 mm. By additionally controlling the fiber lengths and pressure, we can modify the AFREE kinematics further, creating dynamic behaviors and trajectories of actuation. The presented actuator creates the possibility to reconFigure actuator kinematics to meet desired soft robot motions. 

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5. On-demand, remote and lossless manipulation of biofluid droplets

   https://doi.org/10.1039/D2MH00695B  

   Wang, Wei; Sun, Jiefeng; Vallabhuneni, Sravanthi; Pawlowski, Benjamin; Vahabi, Hamed; Nellenbach, Kimberly; Brown, Ashley C.; Scholle, Frank; Zhao, Jianguo; Kota, Arun K. (October 2022, Materials Horizons)

   The recent global outbreaks of epidemics and pandemics have shown us that we are severely under-prepared to cope with infectious agents. Exposure to infectious agents present in biofluids ( e.g. , blood, saliva, urine etc. ) poses a severe risk to clinical laboratory personnel and healthcare workers, resulting in hundreds of millions of hospital-acquired and laboratory-acquired infections annually. Novel technologies that can minimize human exposure through remote and automated handling of infectious biofluids will mitigate such risk. In this work, we present biofluid manipulators, which allow on-demand, remote and lossless manipulation of virtually any liquid droplet. Our manipulators are designed by integrating thermo-responsive soft actuators with superomniphobic surfaces. Utilizing our manipulators, we demonstrate on-demand, remote and lossless manipulation of biofluid droplets. We envision that our biofluid manipulators will not only reduce manual operations and minimize exposure to infectious agents, but also pave the way for developing inexpensive, simple and portable robotic systems, which can allow point-of-care operations, particularly in developing nations. 

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