http://hdl.handle.net/2117/7278 Sun, 19 May 2013 23:41:06 GMT 2013-05-19T23:41:06Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/18161 Title: Designing a practical course in networked control systems Authors: Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Marès Martí, Pere; Martí Colom, Pau; Velasco García, Manel; Yépez Castillo, José Gregorio; Torres Guerrero, Gina; Perelló, Miquel Abstract: This paper presents a hands-on course in networked control systems (NCS) to be integrated in the education of embedded control systems engineers. The course activities have a strong practical component and most of them are applied exercises to be implemented in a NCS setup. The paper describes the experimental setup and then proposes several activities that can be shaped into a course program according to the needs and diverse background of the targeted audience. Mon, 11 Mar 2013 07:52:51 GMT http://hdl.handle.net/2117/18161 2013-03-11T07:52:51Z Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Marès Martí, Pere; Martí Colom, Pau; Velasco García, Manel; Yépez Castillo, José Gregorio; Torres Guerrero, Gina; Perelló, Miquel no This paper presents a hands-on course in networked control systems (NCS) to be integrated in the education of embedded control systems engineers. The course activities have a strong practical component and most of them are applied exercises to be implemented in a NCS setup. The paper describes the experimental setup and then proposes several activities that can be shaped into a course program according to the needs and diverse background of the targeted audience. http://hdl.handle.net/2117/17581 Title: Hands-on course in networked control systems Authors: Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Marès Martí, Pere; Martí Colom, Pau; Velasco García, Manel; Yepez, J.; Torres Guerrero, Gina; Perello, M. Abstract: In many industrial robotic applications there is a need to track periodic reference signals and/or reject periodic disturbances. This paper presents a novel repetitive control design for systems with constant time-delays in both forward and feedback control channels. An additional delay is introduced together with plant delays to construct an internal model for periodic signals, and a simple proportional control is utilized to stabilize the closed-loop system. Sufficient stability conditions of the closed-loop system and the robustness analysis under modeling uncertainties are studied. Experimental results are included to evaluate the validity and effectiveness of the proposed method. Tue, 05 Feb 2013 12:45:53 GMT http://hdl.handle.net/2117/17581 2013-02-05T12:45:53Z Fuertes Armengol, José Mª; Villa Millaruelo, Ricardo; Ayza Graells, Jordi; Marès Martí, Pere; Martí Colom, Pau; Velasco García, Manel; Yepez, J.; Torres Guerrero, Gina; Perello, M. no In many industrial robotic applications there is a need to track periodic reference signals and/or reject periodic disturbances. This paper presents a novel repetitive control design for systems with constant time-delays in both forward and feedback control channels. An additional delay is introduced together with plant delays to construct an internal model for periodic signals, and a simple proportional control is utilized to stabilize the closed-loop system. Sufficient stability conditions of the closed-loop system and the robustness analysis under modeling uncertainties are studied. Experimental results are included to evaluate the validity and effectiveness of the proposed method. http://hdl.handle.net/2117/14476 Title: Qualitative analysis of a one-step finite-horizon boundary for event-driven controllers Authors: Velasco García, Manel; Martí Colom, Pau; Yépez Castillo, José Gregorio; Ruiz Vegas, Francisco Javier; Fuertes Armengol, José Mª; Bini, Enrico Abstract: Performance optimization for networked and embedded control systems refers to the ability of minimizing controllers’ resource utilization and/or improving control performance. Event-driven control has been shown to be a promising technique for minimizing controllers’ computational demands. However, optimization of control performance for event-driven control has not been fully addressed. For LTI plants, this paper presents a boundary for event-driven controllers that determines at each job execution when the next job execution should occur in order to minimize a continuous-time quadratic cost function while minimizing controllers’ computational demand. Simulation results illustrate the qualitative shape of this boundary. Wed, 11 Jan 2012 16:16:36 GMT http://hdl.handle.net/2117/14476 2012-01-11T16:16:36Z Velasco García, Manel; Martí Colom, Pau; Yépez Castillo, José Gregorio; Ruiz Vegas, Francisco Javier; Fuertes Armengol, José Mª; Bini, Enrico no Performance optimization for networked and embedded control systems refers to the ability of minimizing controllers’ resource utilization and/or improving control performance. Event-driven control has been shown to be a promising technique for minimizing controllers’ computational demands. However, optimization of control performance for event-driven control has not been fully addressed. For LTI plants, this paper presents a boundary for event-driven controllers that determines at each job execution when the next job execution should occur in order to minimize a continuous-time quadratic cost function while minimizing controllers’ computational demand. Simulation results illustrate the qualitative shape of this boundary. 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/2117/14053 Title: Efficient utilization of bus idle times in CAN-based networked control systems Authors: Martí Colom, Pau; Camacho Santiago, Antonio; Velasco García, Manel; El Mongi Ben Gaid, Mohamed Abstract: This paper presents a novel approach to networked control systems (NCS) analysis and design that provides increased control performance for a set of control loops that exchange control data over the Controller Area Network (CAN). This is achieved by enabling the following functionality for each control loop: first, standard periodic messaging is guaranteed to ensure stability, and second, non-periodic additional messaging is added whenever the bus is idle in such a way that the aggregated control performance for all control loops is improved. The proposed approach, named Maximum Difference (MD) policy, is computable in a distributed manner, and is practically feasible (computationally efficient and CAN-implementable). We theoretically prove that the MD policy behaves better than static strategies. Simulation results complement the theoretical derivations and show that the MD policy outperforms static, random and Largest Error First policies. Thu, 24 Nov 2011 10:52:13 GMT http://hdl.handle.net/2117/14053 2011-11-24T10:52:13Z Martí Colom, Pau; Camacho Santiago, Antonio; Velasco García, Manel; El Mongi Ben Gaid, Mohamed no This paper presents a novel approach to networked control systems (NCS) analysis and design that provides increased control performance for a set of control loops that exchange control data over the Controller Area Network (CAN). This is achieved by enabling the following functionality for each control loop: first, standard periodic messaging is guaranteed to ensure stability, and second, non-periodic additional messaging is added whenever the bus is idle in such a way that the aggregated control performance for all control loops is improved. The proposed approach, named Maximum Difference (MD) policy, is computable in a distributed manner, and is practically feasible (computationally efficient and CAN-implementable). We theoretically prove that the MD policy behaves better than static strategies. Simulation results complement the theoretical derivations and show that the MD policy outperforms static, random and Largest Error First policies. http://hdl.handle.net/2117/13963 Title: One-step finite horizon boundary with varying control gain for event-driven networked control systems Authors: Yépez Castillo, José Gregorio; Velasco García, Manel; Martí Colom, Pau; Martín, Enric Xavier; Fuertes Armengol, José Mª Abstract: Recent research has shown that event-driven control requires less samples than time-driven (periodic) control. Consequently, event-driven control applied to Networked Control Systems (NCS) is a good approach for alleviating controllers bandwidth demands and reducing overall network traffic. Following this trend, this paper presents an execution rule for event-driven networked controllers that at each job execution aims at postponing the next job execution while applying an appropriated controller gain considering each varying sampling interval that applies at run time. This method permits to dynamically lower the generated traffic for each networked control loop while ensuring the same or better control performance than the achieved by the periodic case. In addition, an implementation strategy capable of dealing with network induced time delays is also presented. Simulation results illustrate the operation and benefits of the presented approach. Fri, 18 Nov 2011 12:36:24 GMT http://hdl.handle.net/2117/13963 2011-11-18T12:36:24Z Yépez Castillo, José Gregorio; Velasco García, Manel; Martí Colom, Pau; Martín, Enric Xavier; Fuertes Armengol, José Mª no Recent research has shown that event-driven control requires less samples than time-driven (periodic) control. Consequently, event-driven control applied to Networked Control Systems (NCS) is a good approach for alleviating controllers bandwidth demands and reducing overall network traffic. Following this trend, this paper presents an execution rule for event-driven networked controllers that at each job execution aims at postponing the next job execution while applying an appropriated controller gain considering each varying sampling interval that applies at run time. This method permits to dynamically lower the generated traffic for each networked control loop while ensuring the same or better control performance than the achieved by the periodic case. In addition, an implementation strategy capable of dealing with network induced time delays is also presented. Simulation results illustrate the operation and benefits of the presented approach. http://hdl.handle.net/2117/12293 Title: Synchronizing sampling and actuation in the absence of global time in networked control systems Authors: Martí Colom, Pau; Camacho Santiago, Antonio; Velasco García, Manel; Marès Martí, Pere; Fuertes Armengol, José Mª Abstract: The successful operation of Networked Control Sys- tems (NCS) requires employing appropriate approaches for dealing with network induced time delays, i.e. time intervals elapsed from consecutive sampling and actua- tion operations. Effective approaches often require to im- pose periodic execution for the sampling and/or actuation operations, enforcing synchronized constant time delays. And considering that sampling and actuation is performed in different nodes, global time between nodes achieved by clock synchronization is the standard assumption or strat- egy that enables such synchronized operations. This pa- per presents a technique that permits to implement these synchronized operations in NCS in the absence of global time. Experimental results corroborate the effectiveness of the presented approach. Thu, 07 Apr 2011 10:17:40 GMT http://hdl.handle.net/2117/12293 2011-04-07T10:17:40Z Martí Colom, Pau; Camacho Santiago, Antonio; Velasco García, Manel; Marès Martí, Pere; Fuertes Armengol, José Mª no The successful operation of Networked Control Sys- tems (NCS) requires employing appropriate approaches for dealing with network induced time delays, i.e. time intervals elapsed from consecutive sampling and actua- tion operations. Effective approaches often require to im- pose periodic execution for the sampling and/or actuation operations, enforcing synchronized constant time delays. And considering that sampling and actuation is performed in different nodes, global time between nodes achieved by clock synchronization is the standard assumption or strat- egy that enables such synchronized operations. This pa- per presents a technique that permits to implement these synchronized operations in NCS in the absence of global time. Experimental results corroborate the effectiveness of the presented approach. http://hdl.handle.net/2117/10676 Title: Invariant manifolds as boundaries for event-driven control systems Authors: Velasco García, Manel; Martí Colom, Pau Abstract: In event-driven control approaches, control updates are triggered by event conditions that are often characterized by different types of boundaries defined in the state-space domain. In this paper we define an event-driven control approach where boundaries are manifolds characterized as invariant sets. With such a boundary, a control update will only be activated when the system trajectory intersects the boundary. And the system trajectory must intersect again the boundary to activate the next control update. For linear systems, we derive an scaling property for these boundaries that permit to regulate the accuracy of the control without altering the timing offered by the scaled boundary. Mon, 20 Dec 2010 10:14:58 GMT http://hdl.handle.net/2117/10676 2010-12-20T10:14:58Z Velasco García, Manel; Martí Colom, Pau no In event-driven control approaches, control updates are triggered by event conditions that are often characterized by different types of boundaries defined in the state-space domain. In this paper we define an event-driven control approach where boundaries are manifolds characterized as invariant sets. With such a boundary, a control update will only be activated when the system trajectory intersects the boundary. And the system trajectory must intersect again the boundary to activate the next control update. For linear systems, we derive an scaling property for these boundaries that permit to regulate the accuracy of the control without altering the timing offered by the scaled boundary. http://hdl.handle.net/2117/9966 Title: Self-triggered networked control systems: an experimental case study Authors: Camacho Santiago, Antonio; Martí Colom, Pau; Velasco García, Manel; Lozoya, Camilo; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª; Griful Ponsati, Eulàlia Abstract: A self-triggered controller is characterized, in general, by a non-periodic sequence of job activations. And each job execution, apart from performing sampling, control algorithm computation and actuation, calculates the next job activation time as a function of the plant state. This paper describes the implementation of self-triggered controllers in networked control systems (NCS). The implementation corroborates that self-triggered control can be used for minimizing bandwidth utilization while providing similar control performance than periodic controllers. Mon, 25 Oct 2010 12:06:15 GMT http://hdl.handle.net/2117/9966 2010-10-25T12:06:15Z Camacho Santiago, Antonio; Martí Colom, Pau; Velasco García, Manel; Lozoya, Camilo; Villa Millaruelo, Ricardo; Fuertes Armengol, José Mª; Griful Ponsati, Eulàlia no A self-triggered controller is characterized, in general, by a non-periodic sequence of job activations. And each job execution, apart from performing sampling, control algorithm computation and actuation, calculates the next job activation time as a function of the plant state. This paper describes the implementation of self-triggered controllers in networked control systems (NCS). The implementation corroborates that self-triggered control can be used for minimizing bandwidth utilization while providing similar control performance than periodic controllers. http://hdl.handle.net/2117/9965 Title: Embedding Kalman techniques in the one-shot task model when non-uniform samples are corrupted by noise Authors: Lozoya, Camilo; Romero, Julio; Martí Colom, Pau; Velasco García, Manel; Fuertes Armengol, José Mª Abstract: The performance of several closed-loop systems whose controllers concurrently execute in a multitasking realtime system may be deteriorated due to timing uncertainties in tasks´executions, problem known as scheduling jitters. Recently, the one-shot task model, that combines irregular sampling, a predictor observer, and strictly periodic actuation, was presented in order to remove the negative effects of jitters. However, its successful application required noise-free samples. In this paper we extend the one-shot task model to the case of noisy measurements. In particular, we embed a Kalman filter into the model taking into account that the available measurements are not periodic. This poses the problem of adapting the standard discrete-time Kalman filter to the case under study, and decide when to apply the prediction and the correction phase. Two different strategies are presented, and their control performance and computation demand are analyzed through real experiments. Mon, 25 Oct 2010 11:56:57 GMT http://hdl.handle.net/2117/9965 2010-10-25T11:56:57Z Lozoya, Camilo; Romero, Julio; Martí Colom, Pau; Velasco García, Manel; Fuertes Armengol, José Mª no The performance of several closed-loop systems whose controllers concurrently execute in a multitasking realtime system may be deteriorated due to timing uncertainties in tasks´executions, problem known as scheduling jitters. Recently, the one-shot task model, that combines irregular sampling, a predictor observer, and strictly periodic actuation, was presented in order to remove the negative effects of jitters. However, its successful application required noise-free samples. In this paper we extend the one-shot task model to the case of noisy measurements. In particular, we embed a Kalman filter into the model taking into account that the available measurements are not periodic. This poses the problem of adapting the standard discrete-time Kalman filter to the case under study, and decide when to apply the prediction and the correction phase. Two different strategies are presented, and their control performance and computation demand are analyzed through real experiments. http://hdl.handle.net/2117/9963 Title: Minimizing control cost in resource-constrained control systems: from Feedback scheduling to event-driven control Authors: Lozoya, Camilo; Martí Colom, Pau; Velasco García, Manel Abstract: This paper evaluates approaches aimed at minimizing aggregated control cost of a set of controllers that concurrently execute sharing limited computing resources. The evaluation focuses on feedback scheduling and event-driven control methods. The performance results drive the analysis to explore self-triggered controllers in the context of minimizing control cost when given a fixed amount of computing resources. This leads to the formulation of an optimization problem, that for given example, is numerically solved. The solution helps understanding the behavior of self-triggered controllers. Mon, 25 Oct 2010 11:45:14 GMT http://hdl.handle.net/2117/9963 2010-10-25T11:45:14Z Lozoya, Camilo; Martí Colom, Pau; Velasco García, Manel no This paper evaluates approaches aimed at minimizing aggregated control cost of a set of controllers that concurrently execute sharing limited computing resources. The evaluation focuses on feedback scheduling and event-driven control methods. The performance results drive the analysis to explore self-triggered controllers in the context of minimizing control cost when given a fixed amount of computing resources. This leads to the formulation of an optimization problem, that for given example, is numerically solved. The solution helps understanding the behavior of self-triggered controllers.