http://hdl.handle.net/2117/3426 Sun, 19 May 2013 17:01:07 GMT 2013-05-19T17:01:07Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/14474 Title: Lowering traffic without sacrificing performance in networked control systems Authors: Martí Colom, Pau; Velasco García, Manel; Yépez Castillo, José Gregorio; Martín Rull, Enric Xavier Abstract: In Networked Control Systems (NCS), the amount of control data exchanged between sensors, controllers and actuators nodes highly depends on the control performance specifications given to each networked control loop. The periodic execution of each loop helps meeting the control specifications while imposing a static network traffic. This paper presents an alternative execution mechanism for each networked control loop that permits to dynamically lower the traffic while ensuring the same or better control performance than the achieved by the periodic case. Simulation results illustrate the theoretical analysis. Wed, 11 Jan 2012 15:23:48 GMT http://hdl.handle.net/2117/14474 2012-01-11T15:23:48Z Martí Colom, Pau; Velasco García, Manel; Yépez Castillo, José Gregorio; Martín Rull, Enric Xavier no In Networked Control Systems (NCS), the amount of control data exchanged between sensors, controllers and actuators nodes highly depends on the control performance specifications given to each networked control loop. The periodic execution of each loop helps meeting the control specifications while imposing a static network traffic. This paper presents an alternative execution mechanism for each networked control loop that permits to dynamically lower the traffic while ensuring the same or better control performance than the achieved by the periodic case. Simulation results illustrate the theoretical analysis. http://hdl.handle.net/2117/14473 Title: Networked sliding mode control of the double integrator system using the event-driven self-triggered approach Authors: Martí Colom, Pau; Velasco García, Manel; Camacho Santiago, Antonio; Martín Rull, Enric Xavier; Fuertes Armengol, José Mª Abstract: Sliding mode control (SMC) methods rely on applying a high-frequency switching control. In networked control systems (NCS), high-frequency operations/transactions are not desirable because communication bandwidth consumption increases dramatically. This paper studies the application of event-driven self-triggered techniques to sliding mode control over networks as a means for reducing the bandwidth utilization. To this end, sliding mode control with hysteresis is adopted and control updates are forced to only occur at the hysteresis band boundary. This paper elaborates on the conditions that must be fulfilled in order to ensure such operation for the case of the double integrator system. Simulation results illustrate the presented concepts. Wed, 11 Jan 2012 13:27:51 GMT http://hdl.handle.net/2117/14473 2012-01-11T13:27:51Z Martí Colom, Pau; Velasco García, Manel; Camacho Santiago, Antonio; Martín Rull, Enric Xavier; Fuertes Armengol, José Mª no Sliding mode control (SMC) methods rely on applying a high-frequency switching control. In networked control systems (NCS), high-frequency operations/transactions are not desirable because communication bandwidth consumption increases dramatically. This paper studies the application of event-driven self-triggered techniques to sliding mode control over networks as a means for reducing the bandwidth utilization. To this end, sliding mode control with hysteresis is adopted and control updates are forced to only occur at the hysteresis band boundary. This paper elaborates on the conditions that must be fulfilled in order to ensure such operation for the case of the double integrator system. Simulation results illustrate the presented concepts. http://hdl.handle.net/2117/13038 Title: Photogrammetry based error analysis of indoor mobile robot localization Authors: Escoda, Josep; Martínez Velasco, Antonio Benito; Benedico, Antonio; Font Llagunes, Josep Maria Abstract: The presented work is a low cost “off-line” method that is able to evaluate the precision of mobile robot localization, which is a difficult task. A reference path is yielded by a drawing pen attached to indoor mobile robot, which also adds timestamps to the trace on the floor. The method is based on comparing the reference path obtained using photogrammetry, with the results of several localization algorithms on board of mobile robots. At the moment, different techniques exist that deal with that problem, but these are either expensive or too rigid. Mon, 25 Jul 2011 11:45:45 GMT http://hdl.handle.net/2117/13038 2011-07-25T11:45:45Z Escoda, Josep; Martínez Velasco, Antonio Benito; Benedico, Antonio; Font Llagunes, Josep Maria no The presented work is a low cost “off-line” method that is able to evaluate the precision of mobile robot localization, which is a difficult task. A reference path is yielded by a drawing pen attached to indoor mobile robot, which also adds timestamps to the trace on the floor. The method is based on comparing the reference path obtained using photogrammetry, with the results of several localization algorithms on board of mobile robots. At the moment, different techniques exist that deal with that problem, but these are either expensive or too rigid. http://hdl.handle.net/2117/12183 Title: Analisis de la señal del centro de presiones mediante auto-informacion mutua: Test con ojos abiertos Authors: Galicia, Berenice; Vallverdú Ferrer, Montserrat; Peydro, Francisca; Casals Gelpi, Alicia Thu, 31 Mar 2011 09:20:55 GMT http://hdl.handle.net/2117/12183 2011-03-31T09:20:55Z Galicia, Berenice; Vallverdú Ferrer, Montserrat; Peydro, Francisca; Casals Gelpi, Alicia no http://hdl.handle.net/2117/9693 Title: Optimization criterion for safety task transfer in cooperative robotics Authors: Hernansanz Prats, Alberto; Amat Girbau, Josep; Casals Gelpi, Alicia Abstract: This paper presents a strategy for a cooperative multirobot system, constituting a Virtual Robot. The Virtual Robot is composed of a set of robotic arms acting as only one, transferring the execution of a teleoperated task from one to another when necessary. To decide which of the robots is the most suitable to execute the task at every instant, a multiparametric decision function has been defined. This function is based on a set of intrinsic and extrinsic evaluation indexes of the robot. Since the internal operation of the Virtual Robot must be transparent to the user, a control architecture has been developed. Thu, 14 Oct 2010 11:50:13 GMT http://hdl.handle.net/2117/9693 2010-10-14T11:50:13Z Hernansanz Prats, Alberto; Amat Girbau, Josep; Casals Gelpi, Alicia no This paper presents a strategy for a cooperative multirobot system, constituting a Virtual Robot. The Virtual Robot is composed of a set of robotic arms acting as only one, transferring the execution of a teleoperated task from one to another when necessary. To decide which of the robots is the most suitable to execute the task at every instant, a multiparametric decision function has been defined. This function is based on a set of intrinsic and extrinsic evaluation indexes of the robot. Since the internal operation of the Virtual Robot must be transparent to the user, a control architecture has been developed. http://hdl.handle.net/2117/9260 Title: Preliminary approach to Lyapunov sampling in CAN-based networked control systems Authors: Yépez Castillo, José Gregorio; Lozoya, Camilo; Velasco García, Manel; Martí Colom, Pau; Fuertes Armengol, José Mª Abstract: This paper presents a preliminary approach to networked control systems (NCS) that relies on an event-driven control method based on Lyapunov sampling. The goal is to study and develop approaches for NCS capable of offering controllers with low bandwidth demands. The paper starts by presenting the theoretical framework required for applying Lyapunov sampling to a set of closed-loop systems that share a serial bus line. The discussion permits identifying which requirements must be fulfilled in order to guarantee overall stability. In addition, the feasibility of the theoretical framework in terms of implementation requires to address problems caused by the implicit distributed architecture of the NCS. In particular, an efficient implementation approach is described for the CAN network. Simulation results illustrate the operation and benefits of the presented approach. Mon, 04 Oct 2010 07:44:50 GMT http://hdl.handle.net/2117/9260 2010-10-04T07:44:50Z Yépez Castillo, José Gregorio; Lozoya, Camilo; Velasco García, Manel; Martí Colom, Pau; Fuertes Armengol, José Mª no This paper presents a preliminary approach to networked control systems (NCS) that relies on an event-driven control method based on Lyapunov sampling. The goal is to study and develop approaches for NCS capable of offering controllers with low bandwidth demands. The paper starts by presenting the theoretical framework required for applying Lyapunov sampling to a set of closed-loop systems that share a serial bus line. The discussion permits identifying which requirements must be fulfilled in order to guarantee overall stability. In addition, the feasibility of the theoretical framework in terms of implementation requires to address problems caused by the implicit distributed architecture of the NCS. In particular, an efficient implementation approach is described for the CAN network. Simulation results illustrate the operation and benefits of the presented approach. http://hdl.handle.net/2117/9158 Title: Equilibrium sampling interval sequences for event-driven controllers Authors: Velasco García, Manel; Martí Colom, Pau; Bini, Enrico Abstract: Standard discrete-time control laws consider periodic execution of control jobs. Although this assumption simplifies the control design and the resource utilization analysis for later implementation, it leads to a conservative usage of computing resources. On the contrary, event-driven control offers controllers with a tighter resource utilization. However, job executions are no longer periodic, and predicting their computing requirements is crucial for efficient implementation in severely limited computing systems. Sampling intervals for event-driven control systems show different patterns, ranging from chaotic behaviors to periodic oscillatory patterns, named equilibrium sampling interval sequences (ESIS). Focusing on resource demands predictability, in this paper we identify the conditions for event-driven controllers to exhibit ESIS, and provide methods to characterize and compute them. Finally, we study the transitions from ESIS to chaotic sampling. Simulated experiments illustrate the paper contributions. Wed, 29 Sep 2010 12:17:45 GMT http://hdl.handle.net/2117/9158 2010-09-29T12:17:45Z Velasco García, Manel; Martí Colom, Pau; Bini, Enrico no Standard discrete-time control laws consider periodic execution of control jobs. Although this assumption simplifies the control design and the resource utilization analysis for later implementation, it leads to a conservative usage of computing resources. On the contrary, event-driven control offers controllers with a tighter resource utilization. However, job executions are no longer periodic, and predicting their computing requirements is crucial for efficient implementation in severely limited computing systems. Sampling intervals for event-driven control systems show different patterns, ranging from chaotic behaviors to periodic oscillatory patterns, named equilibrium sampling interval sequences (ESIS). Focusing on resource demands predictability, in this paper we identify the conditions for event-driven controllers to exhibit ESIS, and provide methods to characterize and compute them. Finally, we study the transitions from ESIS to chaotic sampling. Simulated experiments illustrate the paper contributions. http://hdl.handle.net/2117/9151 Title: On Lyapunov sampling for event-driven controllers Authors: Velasco García, Manel; Martí Colom, Pau; Bini, Enrico Abstract: This paper investigates an event condition for event-driven controllers based on Lyapunov functions. Considering that constant values of a Lyapunov function define contour curves that form closed regions around the equilibrium point, in this paper we present a sampling mechanism that enforces job executions (sampling, control algorithm computation and actuation) each time the system trajectory reaches a given contour curve. By construction, the sequence of generated samples is stable in the discrete Lyapunov sense. However, in order to ensure that the system trajectory will tend to zero as time tends to infinity, it must be ensured that the sequence of samples is infinite. We provide conditions to ensure this property. The approach is illustrated by simulated examples. Wed, 29 Sep 2010 10:22:47 GMT http://hdl.handle.net/2117/9151 2010-09-29T10:22:47Z Velasco García, Manel; Martí Colom, Pau; Bini, Enrico no This paper investigates an event condition for event-driven controllers based on Lyapunov functions. Considering that constant values of a Lyapunov function define contour curves that form closed regions around the equilibrium point, in this paper we present a sampling mechanism that enforces job executions (sampling, control algorithm computation and actuation) each time the system trajectory reaches a given contour curve. By construction, the sequence of generated samples is stable in the discrete Lyapunov sense. However, in order to ensure that the system trajectory will tend to zero as time tends to infinity, it must be ensured that the sequence of samples is infinite. We provide conditions to ensure this property. The approach is illustrated by simulated examples. http://hdl.handle.net/2117/9147 Title: Schedulability Analysis for CAN-based Networked Control Systems with Dynamic Bandwidth Management Authors: Velasco García, Manel; Martí Colom, Pau; Yépez Castillo, José Gregorio; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª Abstract: This paper presents the schedulability analysis for control messages when networked control loops, built on top of the controller area network (CAN), are dynamically allocating bandwidth in terms of their controlled plants' dynamics. The bandwidth allocation policy is theoretically described by an optimization problem and practically solved by the distributed bitwise arbitration of CAN messages when message identifiers, i.e., priorities, reflect control applications demands. This poses the problem of assessing whether the set of real-time messages will meet their deadlines regardless of run-time priority changes. This is solved by a schedulability analysis based on recent results on worst-case response time techniques for real-time CAN applications. The analysis ends up with the schedulability test for this type of applications. Wed, 29 Sep 2010 09:47:08 GMT http://hdl.handle.net/2117/9147 2010-09-29T09:47:08Z Velasco García, Manel; Martí Colom, Pau; Yépez Castillo, José Gregorio; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª no This paper presents the schedulability analysis for control messages when networked control loops, built on top of the controller area network (CAN), are dynamically allocating bandwidth in terms of their controlled plants' dynamics. The bandwidth allocation policy is theoretically described by an optimization problem and practically solved by the distributed bitwise arbitration of CAN messages when message identifiers, i.e., priorities, reflect control applications demands. This poses the problem of assessing whether the set of real-time messages will meet their deadlines regardless of run-time priority changes. This is solved by a schedulability analysis based on recent results on worst-case response time techniques for real-time CAN applications. The analysis ends up with the schedulability test for this type of applications. http://hdl.handle.net/2117/8942 Title: Intuitive graphic interface for assisted teleoperation in surgical applications Authors: Casals Gelpi, Alicia; Campos Querol, Jordi; Giralt Ludevid, Xavier; Amat Girbau, Josep Abstract: Human-Machine interfaces constitute a key factor to guarantee the effective use of technological equipment. In the field of image guided surgery and surgical robots, the availability of an adequate interaction means determines the suitability or not of a given technological aid. This work focuses on the problems surgeons find in planning and executing a robot assisted intervention. Analyzing the potential of computer graphics, together with the surgeons needs during, first, the planning and later on the development of a surgical intervention, the specifications and the implementation of an interface is described. In the design of this interface, special attention has been put on the gesture and attention capabilities that surgeons can devote to the interface. Fri, 17 Sep 2010 08:56:33 GMT http://hdl.handle.net/2117/8942 2010-09-17T08:56:33Z Casals Gelpi, Alicia; Campos Querol, Jordi; Giralt Ludevid, Xavier; Amat Girbau, Josep no Human-Machine interfaces constitute a key factor to guarantee the effective use of technological equipment. In the field of image guided surgery and surgical robots, the availability of an adequate interaction means determines the suitability or not of a given technological aid. This work focuses on the problems surgeons find in planning and executing a robot assisted intervention. Analyzing the potential of computer graphics, together with the surgeons needs during, first, the planning and later on the development of a surgical intervention, the specifications and the implementation of an interface is described. In the design of this interface, special attention has been put on the gesture and attention capabilities that surgeons can devote to the interface. http://hdl.handle.net/2117/8428 Title: An algorithm to design prescribed length codes for single-tracked shaft encoders Authors: Balle Pigem, Borja de; Ventura Capell, Enric; Fuertes Armengol, José Mª Abstract: Abstract-Maximal-length binary shift register sequences have been known for a long time. They have many interesting properties, one of them is that when taken in blocks of n consecutive positions they form 2n - 1 different codes in a closed circular sequence. This property can be used for measuring absolute angular positions as the circle can be divided in as many parts as different codes can be retrieved. This paper describes how a closed binary sequence with arbitrary length can be effectively designed with the minimal possible block-length, using linear feedback shift registers (LFSR). Such sequences can be used for measuring a specified exact number of angular positions, using the minimal possible number of detectors allowed by linear methods. Tue, 27 Jul 2010 12:04:47 GMT http://hdl.handle.net/2117/8428 2010-07-27T12:04:47Z Balle Pigem, Borja de; Ventura Capell, Enric; Fuertes Armengol, José Mª no Abstract-Maximal-length binary shift register sequences have been known for a long time. They have many interesting properties, one of them is that when taken in blocks of n consecutive positions they form 2n - 1 different codes in a closed circular sequence. This property can be used for measuring absolute angular positions as the circle can be divided in as many parts as different codes can be retrieved. This paper describes how a closed binary sequence with arbitrary length can be effectively designed with the minimal possible block-length, using linear feedback shift registers (LFSR). Such sequences can be used for measuring a specified exact number of angular positions, using the minimal possible number of detectors allowed by linear methods.