A Non-Uniform Predictor-Observer for a Networked Control System

Abstract

Cuenca Lacruz, ÁM.; García Gil, PJ.; Albertos Pérez, P.; Salt Llobregat, JJ. (2011). A nonuniform predictor-observer for a networked control system. International Journal of Control, Automation and Systems. 9(6):1194-1202. doi:10.1007/s12555-011-0621-5.International Journal of Control, Automation, and Systems, vol. , no. , pp. 1 A Non-Uniform Predictor-Observer for a Networked Control SystemA. Cuenca, P. García, P. Albertos, and J. Salt Abstract: This paper presents a Non-Uniform Predictor-Observer (NUPO) based control approach in order to deal with two of the main problems related to Networked Control Systems (NCS) or Sensor Networks (SN): time-varying delays and packet loss. In addition, if these delays are longer than the sampling period, the packet disordering phenomenon can appear. Due to these issues, a (scarce) nonuniform, delayed measurement signal could be received by the controller. But including the NUPO proposal in the control system, the delay will be compensated by the prediction stage, and the nonavailable data will be reconstructed by the observer stage. So, a delay-free, uniformly sampled controller design can be adopted. To ensure stability, the predictor must satisfy a feasibility problem based on a time-varying delay-dependent condition expressed in terms of Linear Matrix Inequalities (LMI). Some aspects like the relation between network delay and robustness/performance trade-off are empirically studied. A simulation example shows the benefits (robustness and control performance improvement) of the NUPO approach by comparison to another similar proposal.

Event-triggered predictor-based control with gain-Scheduling and extended state observer for networked control systems

“…Packet disorder can be detected by simply comparing the timestamps corresponding to the last received data packet with the stored one, before updating the local buffer: if the timestamp of the most recently received data packet is older than the timestamp of the stored one, we have a packet disorder. In this case, data packets containing older information are replaced by the newer ones, and hence discarded [5]. Thus, packet disorders can be treated as packet dropouts, and therefore as time-varying delays.…”

“…For instance, the effect of time-varying delays has been tackled under different control schemes: via state-feedback control [4], multi-rate control [33], state estimators [26], [30], and reset-based control in [2], [31]. Packet dropouts have been faced using predictive control [20], predictor-observer methods [5,8], gain scheduling [9], etc. Packet disordering has also been investigated in [22,23,37] by introducing different packet reordering mechanisms, and in [33,7,6] by using dual-rate control.…”

Aproximación de robot a un punto basada en eventos con posicionamiento mediante PSD

“…Ejemplos claros son el control remoto de un robot para alcanzar un punto de la trayectoria a partir de una pose inicial, o el seguimiento de la misma, utilizando sensores ubicados en la infraestructura y conectados al centro remoto. En este contexto, la posibilidad de conectar de forma inalámbrica nodos de sensado, de control y de actuación supone una gran ventaja pero no está exenta de problemas: retardos variables [3,10], pérdida de paquetes [2,4], limitaciones de ancho de banda [11,12], etc. Para potenciar las ventajas de flexibilidad y mantenimiento de las redes inalámbricas reduciendo su efecto negativo en la estabilidad de la planta controlada, se viene trabajando en técnicas de control, sensado y estimación basada en eventos [12,13].…”

Event-Based Sensing and Control for Remote Robot Guidance: An Experimental Case

“…In these contexts, wireless networks are part of the solution and the problem alike [ 5 ]. The drawbacks sharing a common link: time-varying delays [ 6 , 7 ], packet dropouts [ 8 , 9 ], packet disorder [ 8 , 10 ], and network bandwidth constraints [ 11 , 12 ].…”