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.