Supervisory Control Approach Research Articles

A hybrid approach for supervisory control of furnace temperature

The temperature control of the reheat furnace is very difficult due to its complex characteristics. Based on expert knowledge and pyrology mechanism, a hybrid supervisory control system (an optimal setting model) has been developed innovatively to control its temperature. With the help of a statistical process controller, this hybrid supervisory control system can replace the human operator for most of operations in the process. Since an expert compensator is designed to suppress the external disturbance, the proposed model can automatically update the optimal set-point value for the furnace temperature of each zone under the varying boundary conditions. Both simulation and industrial experiment show the viability and effectiveness of the suggested model and its bright application foreground in thermal process.

Supervisory control of reconfigurable flexible-manufacturing workcells - temporary addition of resources

Traditionally, the function of a supervisory controller has been to coordinate the various resources comprising the 'physical' workcell for the production of an a priori set family of parts. That is, the supervisor-synthesis methodologies have assumed that the set of resources comprising the workcell remains constant. In recent practice, however, workcells are assumed to be (temporarily) reconfigurable to form virtual workcells by the introduction of new machines. Virtual workcells may be used, for example, in order to increase throughput. The workcell supervisory-control approach proposed in this paper advocates the use of a pair of independent supervisors, working in concert, to achieve effective control of the expanded workcell including the (a priori unknown) new machines that are temporarily added into the workcell. The nominal supervisor is responsible for controlling the flow of parts when the parts follow any one of their nominal routes, while the complementary supervisor is responsible for controlling the flow of parts when they follow any one of the new processing routes that were added to the parts' processing routes due to the introduction of new machines. Each supervisor is synthesized individually.

Supervisory Control of Functionally-Expandable Manufacturing Systems

Supervisory controllers have traditionally coordinated the various resources of manufacturing systems, such as flexible manufacturing workcells, for the production of a priori set families of part types. This paper expands on this capability by allowing the control of the production of new part types side by side with previously defined and planned for nominal part types. The proposed basic workcell supervisory-control approach advocates the use of a pair of non-communicating independent supervisors, synthesized individually but working in concert, to achieve the production of existing and new part types: nominal and complementary supervisors, respectively. The nominal supervisor is responsible for controlling the behavior of the nominal system, producing the set of a priori planned-for part types, whereas the complementary supervisor controls the flow of the a priori unplanned-for new part types.

A fuzzy logic approach to accommodate thermal stress and improve the start-up phase in combined cycle power plants

Use of combined cycle power generation plant has increased dramatically over the last decade. A supervisory control approach based on a dynamic model is developed, which makes use of proportional-integral-derivative (PID), fuzzy logic and fuzzy PID schemes. The aim is to minimize the steam turbine plant start-up time, without violating maximum thermal stress limits. An existing start-up schedule provides the benchmark by which the performance of candidate controllers is assessed. Improvements regarding possible reduced start-up times and satisfaction of maximum thermal stress restrictions have been realized using the proposed control scheme.

Hybrid Supervisory Control in Intelligent Autonomous Systems

It is shown that the quest for autonomy in engineering systems leads to intelligent control and to approaches that combine methodologies from the control, computing and communication networks areas and to hybrid system methodologies. The area of hybrid dynamical systems is of particular importance to intelligent control and several approaches to modeling and control of such systems are briefly discussed, with emphasis on supervisory control approaches that are based on discrete abstractions.

Nonlinear state and parameter estimation in batch biological wastewater treatment

Wastewater treatment is an active research area from both the technological and the control points of view. Various types of supervisory and low-level control approaches can be applied in this field. However, the inaccessibility of sensors which should provide the data needed for control is one of the major obstacles in current development. Estimation is therefore a prerequisite for performing those control tasks that rely on important process variables which cannot be measured directly. In this paper an estimation algorithm for simultaneous state and parameter estimation of a nonlinear process is derived for a batch biological wastewater treatment process. The aim is to estimate two important process variables related to dissolved oxygen dynamics during the aerobic phase of a batch cycle: the oxygen transfer function and biomass respiration rate. The main contributions of the work presented are providing on-line information about these variables for improved process control and diagnosis, and the applica...

Nonlinear state and parameter estimation in batch biological wastewater treatment

Wastewater treatment is an active research area from both the technological and the control points of view. Various types of supervisory and low-level control approaches can be applied in this field. However, the inaccessibility of sensors which should provide the data needed for control is one of the major obstacles in current development. Estimation is therefore a prerequisite for performing those control tasks that rely on important process variables which cannot be measured directly. In this paper an estimation algorithm for simultaneous state and parameter estimation of a nonlinear process is derived for a batch biological wastewater treatment process. The aim is to estimate two important process variables related to dissolved oxygen dynamics during the aerobic phase of a batch cycle: the oxygen transfer function and biomass respiration rate. The main contributions of the work presented are providing on-line information about these variables for improved process control and diagnosis, and the application of the chosen nonlinear estimation algorithms for simultaneous state and parameter estimation in process control.

A Supervisory Control Approach for Execution Control of an FMC

This paper presents a generic methodology based on formal language theory for the modeling and control of flexible manufacturing cell (FMC) systems. The motivating idea behind the overall approach stems from the supervisory control theory under the framework of Ramadge and Wonham. Essentially, we characterize the asynchronous and dynamic behavior of an FMC as a regular language and formulate the control logic generation problem as a sublanguage calculation problem, which requires the resulting language to satisfy at least two properties: maximal permissiveness and controllability. Then an algorithm for resolving the problem is presented. Based on the solution of the problem called supervisor, we propose a controller architecture that guarantees coordinated operation of an FMC through the regulation of occurrences of events. An adaptive control policy that regenerates supervisors on changes in task configurations is presented and a dynamic equation that describes the evolution of the control logic along time is derived. Then, we show that the proposed maximally permissive adaptive control policy has a number of preferred properties, including computational efficiency and consistency between the successive supervisors. Finally, a controller for an example FMC is implemented, using the object-oriented software modules. Our procedure has the merit of mathematical soundness, modular design, and systematic implementation.

A novel supervisory control approach to switching operations for hybrid wind/diesel/battery/mains energy systems

Hybrid energy systems, integrating renewable energy technologies with diesel generators, batteries and inverters, can provide 24 h grid quality power to remote communities. Work in the Centre for Renewable Energy Systems Technology Australia (CRESTA) has been carried out to develop a new hybrid/wind/diesel/battery/mains energy system. In the system, the switching operations of different modes play an important role in the proper running of the system. From the view of discrete event dynamic systems, a novel supervisory control approach for the switching operations of modes has been explored, in which the switching actions are defined as events, switching modes as states and events take the system from one state to another. The supervisory controller for a prototype of the hybrid wind/diesel/battery/mains energy system has been designed and it has been simulated in PSCAD/EMTDC. The results reveal that this technique could facilitate the analysis and design of supervisory controllers for switching operations, particularly in the complicated hybrid energy systems.

Supervisory adaptive control for the structural vibration of a coordinate-measuring machine

A supervisory adaptive control approach has been developed for a structural vibration control of a coordinate measuring machine, which is a dynamic system with time varying system model order and parameters. An on-line dynamic data system modelling algorithm is used to identify the system model order and parameters simultaneously. Based on the identified model, a predictive control algorithm is applied to generate control commands. A supervisory strategy with several monitoring indices and decision-making rules is proposed to supervise the modelling and control processes. The developed supervisory adaptive control approach has been implemented in a digital signal processor board for structural vibration control. Experimental results indicate a 75% reduction in the peak-to-peak vibration and an 80% reduction in the settling time.