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Galiana I.,Center for Automation and Robotics | Hammond F.L.,Harvard University | Howe R.D.,Harvard University | Popovic M.B.,Worcester Polytechnic Institute
IEEE International Conference on Intelligent Robots and Systems | Year: 2012

Stroke is the leading cause of long-term disability in the United States, affecting over 795,000 people annually. In order to regain motor function of the upper body, patients are usually treated by regular sessions with a dedicated physical therapist. A cost-effective wearable upper body orthotics system that can be used at home to empower both the patients and physical therapists is described. The system is composed of a thin, compliant, lightweight, cost-effective soft orthotic device with an integrated cable actuation system that is worn over the upper body, an embedded limb position sensing system, an electric actuator package and controller. The proposed device is robust to misalignments that may occur during actuation of the compliant brace or when putting on the system. Through simulations and experimental evaluation, it was demonstrated i) that the soft orthotic cable-driven shoulder brace can be successfully actuated without the production of off-axis torques in the presence of misalignments and ii) that the proposed model can identify linear and angular misalignments online. © 2012 IEEE.

Villagra J.,Center for Automation and Robotics | Herrero-Perez D.,Technical University of Cartagena
IEEE Transactions on Control Systems Technology | Year: 2012

This work addresses the path tracking problem of industrial guidance systems used by automated guided vehicles (AGVs) in load transfer operations. We focus on the control law that permits to AGVs to operate tracking a predefined route with industrial grade of accuracy, repeatability and reliability. One of the main issues of this problem is related to the important weight variation of AGVs when transporting a load, which induces slipping and skidding effects. Besides, localization error of the guidance system should be taken into account because position estimation is typically performed at a low sample rate. Other key point is that control law oscillations can knock down the load, which gives rise to safety and performance problems. Three control techniquesfuzzy, vector pursuit and flatness-based controlare compared in order to evaluate how they can deal with these problems and satisfy the robustness requirements of such an industrial application. © 2011 IEEE.

Gajate A.,Center for Automation and Robotics | Bustillo A.,University of Burgos | Haber R.E.,Center for Automation and Robotics
International Journal of Innovative Computing, Information and Control | Year: 2012

This paper presents the design and implementation of an intelligent control system based on local neurofuzzy models of the milling process relayed through an Ethernet-based application. Its purpose is to control the spindle torque of a milling process by using an internal model control paradigm to modify the feed rate in real time. The stabilization of cutting torque is especially necessary in milling processes such as high-speed roughing of steel moulds and dies that present minor geometric uncertainties. Thus, maintenance of the cutting torque increases the material removal rate and reduces the risk of damage due to excessive spindle vibration, a very sensitive and expensive component in all high-speed milling machines. Torque control is therefore an interesting challenge from an industrial point of view. Direct and inverse local neurofuzzy models used in the internal model control paradigm are obtained through an identification process which uses representative input-output data from the system under study. These local neurofuzzy models are dynamically created online (for each new datum to be processed). Once obtained, the models that describe the dynamic process form the basis of the networked control system,. This methodology is successfully applied in a production environment, in order to demonstrate improvements in both performance and effectiveness. Two different industrial tasks are tested: roughing of slots and roughing of surfaces with sudden, unexpected height steps. In both cases the control system demonstrated its capability to avoid torque peaks that could lead to spindle damage while maintaining high productivity. © 2012 ICIC International.

Arevalo J.C.,Center for Automation and Robotics | Garcia E.,Center for Automation and Robotics
IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews | Year: 2012

The application of impedance control strategies to modern legged locomotion is analyzed, paying special attention to the concepts behind its implementation which is not straightforward. In order to implement a functional impedance controller for a walking mechanism, the concepts of contact, impact, friction, and impedance have to be merged together. A literature review and a comprehensive analysis are presented compiling all these concepts along with a discussion on position-based versus force-based impedance control approaches, and a theoretical model of a robotic leg in contact with its environment is introduced. A theoretical control scheme for the legs of a general legged robot is also introduced, and some simulations results are presented. © 1998-2012 IEEE.

Tejado I.,University of Extremadura | Milanes V.,Center for Automation and Robotics | Villagra J.,Center for Automation and Robotics | Vinagre B.M.,University of Extremadura
IEEE Transactions on Control Systems Technology | Year: 2013

This paper addresses the problem of e-safety driving in urban areas, where the principal limiting factor is vehicle-to-vehicle or vehicle-to-infrastructure communications. Time-varying network-induced delays constitute the main concern of networked control systems since they may negatively affect the velocity control of a vehicle at low speeds and consequently cause an accident. A system to adapt the vehicle's speed to avoid or mitigate possible accidents has been developed. In particular, gain scheduling is used in a local fractional-order proportional integral controller to compensate the effects of delay. Experimental results on a prototype Citroën vehicle in a real environment are presented, which demonstrate the effectiveness of the proposed system. © 1993-2012 IEEE.

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