J.H. Sandee

Bio: J.H. Sandee is an academic researcher from Eindhoven University of Technology. The author has contributed to research in topics: Control system & Control theory. The author has an hindex of 6, co-authored 10 publications receiving 833 citations.

Analysis of event-driven controllers for linear systems

Abstract: Most research in control engineering considers periodic or time-triggered control systems with equidistant sample intervals. However, practical cases abound in which it is of interest to consider event-driven control in which the sampling is event-triggered. Although there are various benefits of using event-driven control like reducing resource utilization (e.g., processor and communication load), their application in practice is hampered by the lack of a system theory for event-driven control systems. To provide a first step in developing an event-driven system theory, this paper considers an event-driven control scheme for perturbed linear systems. The event-driven control scheme triggers the control update only when the (tracking or stabilization) error is large. In this manner, the average processor and/or communication load can be reduced significantly. The analysis in this paper is aimed at the control performance in terms of practical stability (ultimate boundedness). Several examples illustrate t...

Event-driven control as an opportunity in the multidisciplinary development of embedded controllers

Abstract: Severe requirements on embedded controllers ask for new approaches that can effectively bridge the existing gap between the disciplines software and control engineering. Event-driven control is presented as an opportunity to create a negotiable environment for the sample frequency, control performance and the usage of processing power. Simulations show that event-driven control can reduce the average processor load without influencing the control performance too much. Some first ideas for analysis and synthesis techniques look promising and future research is focus on the extension of these techniques.

Case studies in event-driven control

Abstract: The majority of research in control engineering considers periodic or time-triggered control systems with equidistant sample intervals. However, practical cases abound in which it is of interest to consider event-driven control systems, where the sampling is event-triggered. Although there are various benefits of using event-driven control like reducing resource usage (e.g. processor and communication load), their application in practice is hampered by the lack of a system theory for event-driven control systems. In this paper we present two types of event-driven controllers and show their potential via industrially relevant case studies and indicate initial theoretical results.

Analysis and experimental validation of processor load for event-driven controllers

Abstract: Event-driven controllers differ from the standard digital controllers as their sample times are generally not periodic (time equidistant). In literature several proposals for event-driven controllers are made in order to reduce the number of control updates and consequently the processor load needed for its implementation. This is possible without deteriorating the control performance significantly. However, experimental validation has not been presented in literature. This paper aims at filling this gap. Simulations, as well as experiments on a copier paper path test setup, show that a reduction in the number of control updates indeed results in a considerable reduction of the processor load, with only a small decrease of control performance. Furthermore, we present a method to predict the processor load very accurately, without having to implement the controller on a test setup.

Analysis and experimental validation of a sensor-based event-driven controller

Abstract: We present an event-driven servo controller that is based on an (extremely) low resolution encoder. The control value is updated at each moment that an encoder pulse is detected, yielding zero measurement error. However, as the time between two control updates is varying now, conventional controller design methods do not apply as they normally assume a constant sample time. To deal with this problem, the controller design is performed by transforming the system equations from the time domain to the position (spatial) domain, in which the encoder pulses, and therefore the controller triggering, are equidistant. In this way, the control problem is rewritten as a synchronous problem for a non-linear plant. A gain scheduled controller is designed and analyzed in the spatial domain. This event-driven controller is experimentally validated on a prototype printer where a 1 pulse per revolution encoder is used to accurately control the motion of images through the printer.

Distributed Event-Triggered Control for Multi-Agent Systems

Abstract: Event-driven strategies for multi-agent systems are motivated by the future use of embedded microprocessors with limited resources that will gather information and actuate the individual agent controller updates. The controller updates considered here are event-driven, depending on the ratio of a certain measurement error with respect to the norm of a function of the state, and are applied to a first order agreement problem. A centralized formulation is considered first and then its distributed counterpart, in which agents require knowledge only of their neighbors' states for the controller implementation. The results are then extended to a self-triggered setup, where each agent computes its next update time at the previous one, without having to keep track of the state error that triggers the actuation between two consecutive update instants. The results are illustrated through simulation examples.

An introduction to event-triggered and self-triggered control

Abstract: Recent developments in computer and communication technologies have led to a new type of large-scale resource-constrained wireless embedded control systems. It is desirable in these systems to limit the sensor and control computation and/or communication to instances when the system needs attention. However, classical sampled-data control is based on performing sensing and actuation periodically rather than when the system needs attention. This paper provides an introduction to event- and self-triggered control systems where sensing and actuation is performed when needed. Event-triggered control is reactive and generates sensor sampling and control actuation when, for instance, the plant state deviates more than a certain threshold from a desired value. Self-triggered control, on the other hand, is proactive and computes the next sampling or actuation instance ahead of time. The basics of these control strategies are introduced together with a discussion on the differences between state feedback and output feedback for event-triggered control. It is also shown how event- and self-triggered control can be implemented using existing wireless communication technology. Some applications to wireless control in process industry are discussed as well.

Periodic event-triggered control for nonlinear systems

Abstract: Event-triggered control (ETC) is a control strategy that is especially suited for applications where communication resources are scarce. By updating and communicating sensor and actuator data only when needed for stability or performance purposes, ETC is capable of reducing the amount of communications, while still retaining a satisfactory closed-loop performance. In this paper, an ETC strategy is proposed by striking a balance between conventional periodic sampled-data control and ETC, leading to so-called periodic event-triggered control (PETC). In PETC, the event-triggering condition is verified periodically and at every sampling time it is decided whether or not to compute and to transmit new measurements and new control signals. The periodic character of the triggering conditions leads to various implementation benefits, including a minimum inter-event time of (at least) the sampling interval of the event-triggering condition. The PETC strategies developed in this paper apply to both static state-feedback and dynamical output-based controllers, as well as to both centralized and decentralized (periodic) event-triggering conditions. To analyze the stability and the L2-gain properties of the resulting PETC systems, three different approaches will be presented based on 1) impulsive systems, 2) piecewise linear systems, and 3) perturbed linear systems. Moreover, the advantages and disadvantages of each of the three approaches will be discussed and the developed theory will be illustrated using a numerical example.