Model-Based Engineering of Supervisory Controllers using CIF

In the Model-Based Engineering (MBE) paradigm, models are the core elements in the design process of a system from its requirements to the actual implementation of the system. By means of Supervisory Control Theory (SCT), supervisory controllers (supervisors) can be synthesized instead of designingthem manually. In this paper, a framework based on the Compositional Interchange Format for hybrid systems (CIF) has been developed that integrates the MBE andthe SCT paradigms. To illustrate the framework, an industrial-size case study has been performed: 'synthesis of a supervisory controller for the patientsupport system of an MRI scanner'. In this case study, we address 1) modelling of the components and the control requirements; 2) synthesis of the supervisor;3) simulation of the synthesized supervisor and a hybrid model of the plant; and 4) real-time, simulation based control of the supervisor and the actual patient support system of the MRI scanner

Supervisory control synthesis for a patient support system

The increasing complexity of systems and the increasing market pressure necessitate the need for methods to maximize reuse and to minimize the effort to develop new systems. Modelbased engineering is one of these methods. It uses models and model-based techniques in the development process to analyze and synthesize systems and components. In this report, Supervisory Control Synthesis is used to design a supervisory controller for a patient support system. This system is used to position a patient in a Magnetic Resonance Imaging (MRI) scanner. To improve the evolvability of the design, the uncontrolled system and the control requirements are modeled independently, using small loosely coupled minimal restrictive automata. An implementation of the synthesized supervisor is realized by means of a transformation to an automaton in the Compositional Interchange Format (CIF). The supervisor is validated by means of hardware-in-the-loop simulation, using the real patient support system

Application of supervisory control synthesis to MRI scannes : improving evolvability

This paper presents an application of Ramadge-Wonham supervisory control theory to a patient support system for MRI scanners. The obtained controller was implemented and tested on real hardware. A distinguishing feature of the proposed application is that the evolvability of the controller is an essential requirement. By evolvability is the ability to adapt the controller to meet modified control objectives. The experiments conducted in the course of the case-study indicate that the use of supervisory control theory improves the evolvability of the controller

Supervisory control synthesis for a patient support system

Supervisory control theory (SCT) provides a formal approach to supervisory controller synthesis. In this paper, SCT is used to design a supervisory controller for a patient support system. This system is used to position a patient in a Magnetic Resonance Imaging (MRI) scanner. To improve the evolvability of the design, the uncontrolled system and the control requirements are modeled independently, using small, loosely coupled and minimally restrictive automata. An implementation of the synthesized supervisor is realized by means of a transformation to an automaton in the Compositional Interchange Format (CIF). The supervisor is validated by means of hardware-in-the-loop simulation, using the real patient support table

Supervisory control synthesis in the medical domain

By means of Ramadge-Wonham supervisory control theory, supervisorycontrollers (supervisors) can be synthesized instead of designing themmanually. This chapter presents an application of supervisory control to apatient support system for MRI scanners. The design process of the controllerfrom its requirements to its actual implementation on real hardware has beendone according to the synthesis-based engineering paradigm. This paradigmintegrates the model-based engineering and supervisory control paradigms. Thedesign process is supported by a tool framework that is based on theCompositional Interchange Format for hybrid systems (CIF). An experimentconducted in the course of the case-study indicates that this design processimproves the evolvability of the controller significantly

Computational effort of BDD-based supervisor synthesis of extended finite automata

We consider supervisor synthesis of Extended Finite Automata that are represented using Binary Decision Diagrams (BDDs). Peak used BDD nodes and BDD operation count are introduced as platform independent and deterministic metrics that quantitatively indicate the computational effort needed to synthesize a supervisor. The use of BDD operation count is novel with respect to expressing supervisor synthesis effort. The (dis-)advantages of using these metrics to state of practice metrics such as wall clock time and worst case state space size are analyzed. The supervisor synthesis algorithm is initiated with a certain event- and variable order. It is already known from literature that variable order influences synthesis performance. We show that the event order is also relevant to consider. We discuss how these orders influence the synthesis effort and, by performing an experiment on a set of models, we show the extent of this influence

Application of supervisory control synthesis to a patient support table of a magnetic resonance imaging scanner

In this paper, we present a case-study on application of Ramadge-Wonham supervisory control theory (abbreviated by SCT in the sequel) to a patient support system of a magnetic resonance imaging (MRI) scanner. We discuss the whole developmental cycle, starting from the mathematical models of the uncontrolled system and of the control requirements, and ending with the implementation of the obtained controller on the actual hardware. The obtained controller was tested on the physical system. In this case study, we attempted to build the models in a modular way, in order to decrease the computational complexity of the controller synthesis and to improve the adaptability of the models. An important advantage of SCT is that it allows automatic generation of the controller, and that it can thus improve adaptability of the control software. We also briefly discuss our experience on the adaptability of the control software, obtained in the course of this case study. Note to Practitioners-Current industrial practice of supervisory controller design is based on a separation between informal specification of behavioral requirements by domain experts, and encoding of these requirements in control software by software specialists, leading to code and requirements that are difficult to develop, debug, maintain, and adapt. We propose a supervisory controller design process that instead relies on modeling the behavioral requirements and uncontrolled system, and generating the controller by means of supervisory control synthesis. Where supervisory control synthesis provides technology to develop the controller right, we employ simulation-based validation to ensure that the right controller is built. This can be done by means of execution of user-defined scenarios, and generation of graphs showing the evolution of the model variables as a function of time. The simulator also supports real-time, interactive, simulation and animation, based on user supplied images of the system in the standardized Scalable Vector Graphics (SVG) format. The discussed new development process of supervisory controllers has been demonstrated to be highly effective for generation of code, that has been used for real-time control of an actual patient support table of an MRI system. The enormous potential for reduction of development time of new controller functionality is illustrated by means of an actual user modification request case. The new supervisory controller development process is currently under investigation by several high tech industries in Eindhoven. A new project has been defined together with several high tech companies, including an innovative software company, to further develop the methods, techniques and tools to a level that is suited for commercial application