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Author

Z. Wang

Other affiliations: Mercedes-Benz
Bio: Z. Wang is an academic researcher from University of Central Florida. The author has contributed to research in topics: Robust control & Lyapunov function. The author has an hindex of 11, co-authored 19 publications receiving 578 citations. Previous affiliations of Z. Wang include Mercedes-Benz.

Papers
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Journal ArticleDOI
01 Jan 2012
TL;DR: A small dual cohort pilot study with traumatic spinal cord injured subjects designed to investigate the utility of a wheelchair-mounted robotic arm for these subjects finds possible directions for system design presented to concurrently achieve better performance and satisfaction outcomes.
Abstract: We report a small dual cohort pilot study with traumatic spinal cord injured (SCI) subjects designed to investigate the utility of a wheelchair-mounted robotic arm for these subjects The UCF-MANUS, a vision-based 6DOF assistive robotic arm, has been designed to aid individuals with upper limb extremities to complete tasks of daily living that they would otherwise be unable to complete themselves Pick-and-place IADL tasks were designed and ten (10) users post-SCI were selected under IRB guidelines to be trained and tested with the system for 1 to 2 h weekly over a period of three weeks During this time, they controlled the robot either through a manual or an autonomous (supervised) mode of operation Baseline characteristics (pre-study), quantitative performance metrics (during study), and psychometrics (post-study) were obtained and statistically analyzed to test a set of hypotheses related to performance and satisfaction with the two control modes At the end of the study, both the autonomous and the manual mode had comparable task completion times while user effort required for operating the robot in autonomous mode was significantly less than that for the manual mode However, the autonomous mode failed to commensurately raise the user's level of satisfaction Over the three-week study, the manual mode users showed a pronounced learning effect in terms of reducing mean task completion time and number of commands while the auto mode users showed improvement in terms of reduction of variability Based on qualitative feedback and quantitative results, possible directions for system design are presented to concurrently achieve better performance and satisfaction outcomes

145 citations

Journal ArticleDOI
TL;DR: In this paper, a full-state feed-forward/feedback controller is designed to suppress the aeroelastic vibrations of a nonlinear wing section subject to external disturbance.
Abstract: In this paper, a class of aeroelastic systems with an unmodeled nonlinearity and external disturbance is considered. By using leading- and trailing-edge control surface actuations, a full-state feedforward/feedback controller is designed to suppress the aeroelastic vibrations of a nonlinear wing section subject to external disturbance. The fullstate feedback control yields a uniformly ultimately bounded result for two-axis vibration suppression. With the restriction that only pitching and plunging displacements are measurable while their rates are not, a high-gain observer is used to modify the full-state feedback control design to an output feedback design. Simulation results demonstrate the efficacy of the multi-input multi-output control toward suppressing aeroelastic vibration and limit cycle oscillations occurring in pre and postflutter velocity regimes when the system is subjected to a variety of external disturbance signals. Comparisons are drawn with a previously designed adaptive multi-input multi-output controller.

72 citations

Journal ArticleDOI
TL;DR: Progress is reported in the empowerment of the UCF-MANUS system with a suite of sensory, computational, and multimodal interface capabilities so that its autonomy can be made accessible to users with a wide range of disabilities.
Abstract: This paper reports on the system design for integrating the various processes needed for end-to-end implementation of a smart assistive robotic manipulator Specifically, progress is reported in the empowerment of the UCF-MANUS system with a suite of sensory, computational, and multimodal interface capabilities so that its autonomy can be made accessible to users with a wide range of disabilities Laboratory experiments are reported to demonstrate the ability of the system prototype to successfully and efficiently complete object retrieval tasks Benchmarking of the impact of the various interface modalities on user performance is performed via empirical studies with healthy subjects operating the robot in a simulated instrumental activities of daily living tasks setup It is seen through a analysis of the collected quantitative data that the prototype is interface neutral and shows robustness to variations in the tasks and the environment It is also seen that the prototype autonomous system is quantitatively superior to Cartesian control for all tested tasks under a “number of commands” metric, however, under a “time to task completion” metric, the system is seen to be superior for “hard” tasks but not for “easy” tasks

34 citations

Journal ArticleDOI
TL;DR: An anthropomorphic-like approach was found to be the most suitable for reliable and speedy object retrieval and gross reaching/docking motions of the robot arm using proprioception are followed by fine alignment of the hand through visual feedback and eventually grasping based on haptic feedback.
Abstract: In this paper, we document the progress in the design of a motion segmentation and control strategy for a smart assistive robot arm that can provide assistance during activities of daily living to the elderly and/or users with disabilities. Interaction with the environment is made challenging by the kinematic uncertainty in the robot, imperfect sensor calibration as well as the fact that most activities of daily living are generally required to be performed in unstructured environments. The motion control strategy exploits visual and force feedback from sensors in the robot’s hand to provide the basis for efficient interaction with the unstructured environment. Through experimental studies with a variety of objects of daily life in natural environments, an anthropomorphic-like approach was found to be the most suitable for reliable and speedy object retrieval. Specifically, gross reaching/docking motions of the robot arm using proprioception are followed by fine alignment of the hand through visual feedback and eventually grasping based on haptic feedback. Experimental results using a wheelchair mounted robotic arm are presented to demonstrate the efficacy of the proposed algorithms.

34 citations


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TL;DR: In this paper, the authors reviewed some main results and progress in distributed multi-agent coordination, focusing on papers published in major control systems and robotics journals since 2006, and proposed several promising research directions along with some open problems that are deemed important for further investigations.
Abstract: This article reviews some main results and progress in distributed multi-agent coordination, focusing on papers published in major control systems and robotics journals since 2006. Distributed coordination of multiple vehicles, including unmanned aerial vehicles, unmanned ground vehicles and unmanned underwater vehicles, has been a very active research subject studied extensively by the systems and control community. The recent results in this area are categorized into several directions, such as consensus, formation control, optimization, task assignment, and estimation. After the review, a short discussion section is included to summarize the existing research and to propose several promising research directions along with some open problems that are deemed important for further investigations.

1,655 citations

Journal ArticleDOI
TL;DR: This work proposes an intuitive formalism that captures assistance as policy blending, illustrates how some of the existing techniques for shared control instantiate it, and provides a principled analysis of its main components: prediction of user intent and its arbitration with the user input.
Abstract: In shared control teleoperation, the robot assists the user in accomplishing the desired task, making teleoperation easier and more seamless. Rather than simply executing the user's input, which is hindered by the inadequacies of the interface, the robot attempts to predict the user's intent, and assists in accomplishing it. In this work, we are interested in the scientific underpinnings of assistance: we propose an intuitive formalism that captures assistance as policy blending, illustrate how some of the existing techniques for shared control instantiate it, and provide a principled analysis of its main components: prediction of user intent and its arbitration with the user input. We define the prediction problem, with foundations in inverse reinforcement learning, discuss simplifying assumptions that make it tractable, and test these on data from users teleoperating a robotic manipulator. We define the arbitration problem from a control-theoretic perspective, and turn our attention to what users consider good arbitration. We conduct a user study that analyzes the effect of different factors on the performance of assistance, indicating that arbitration should be contextual: it should depend on the robot's confidence in itself and in the user, and even the particulars of the user. Based on the study, we discuss challenges and opportunities that a robot sharing the control with the user might face: adaptation to the context and the user, legibility of behavior, and the closed loop between prediction and user behavior.

331 citations

Journal ArticleDOI
TL;DR: The glider coordinated control system (GCCS) uses a detailed glider model for prediction and a simple particle model for planning to steer a fleet of underwater gliders to a set of coordinated trajectories.
Abstract: The glider coordinated control system (GCCS) uses a detailed glider model for prediction and a simple particle model for planning to steer a fleet of underwater gliders to a set of coordinated trajectories. The GCCS also serves as a simulation testbed for the design and evaluation of multivehicle control laws. In this brief, we describe the GCCS and present experimental results for a virtual deployment in Monterey Bay, CA and a real deployment in Buzzards Bay, MA.

236 citations

01 Jul 1989
TL;DR: The primary thrust of the research was to conduct fundamental research in the theories and methodologies for designing complex high-performance multivariable feedback control systems; and to conduct feasibiltiy studies in application areas of interest to NASA sponsors that point out advantages and shortcomings of available control system design methodologies as discussed by the authors.
Abstract: The primary thrust of the research was to conduct fundamental research in the theories and methodologies for designing complex high-performance multivariable feedback control systems; and to conduct feasibiltiy studies in application areas of interest to NASA sponsors that point out advantages and shortcomings of available control system design methodologies.

194 citations

Journal ArticleDOI
TL;DR: A control design approach which stabilizes a haptic interface when coupled to a broad class of human operators and virtual environments is outlined, including structural flexibility and noncollocation of sensors and actuators.
Abstract: The goal of control law design for haptic displays is to provide a safe and stable user interface while maximizing the operator's sense of kinesthetic immersion in a virtual environment. This paper outlines a control design approach which stabilizes a haptic interface when coupled to a broad class of human operators and virtual environments. Two-port absolute stability criteria are used to develop explicit control law design bounds for two different haptic display implementations: the impedance display and admittance display. The strengths and weaknesses of each approach are illustrated through numerical and experimental results for a three degree-of-freedom device. The example highlights the ability of the proposed design procedure to handle some of the more difficult problems in control law synthesis for haptics, including structural flexibility and noncollocation of sensors and actuators.

183 citations