Discrete Controller Synthesis Research Articles

The Performance of Symbolic Limited Optimal Discrete Controller Synthesis in the Control and Path Planning of the Quadcopter

The Performance of Symbolic Limited Optimal Discrete Controller Synthesis in the Control and Path Planning of the Quadcopter

Incorporating Symbolic Discrete Controller Synthesis into a Virtual Robot Experimental Platform: An Implementation with Collaborative Unmanned Aerial Vehicle Robots

We introduce a modeling framework aimed at incorporating symbolic discrete controller synthesis (DCS) into a virtual robot experimental platform. This framework involves symbolically representing the behaviors of robotic systems along with their control objectives using synchronous programming techniques. We employed DCS algorithms through the reactive synchronous environment ReaX to generate controllers that fulfill specified objectives. These resulting controllers were subsequently deployed on the virtual robot experimental platform Simscape. To demonstrate and validate our approach, we provide an implementation example involving collaborative UAV robots.

Control of Discrete Event Systems by Using Symbolic Transition Model: An Application to Power Grids

AbstractIn this paper, a new symbolic modeling framework is proposed for the control of discrete event systems (discrete controller synthesis). Reactive infinite-state systems are generally dynamic systems with inputs and outputs. Modeling the outputs in existing symbolic modeling methods for reactive infinite-state systems has not been extensively discussed in the literature. It is crucial to realistically model the outputs and obtain reliable controllers. One of the main contributions and innovations in this study is the ability to symbolically model their output. In this direction, symbolic transition models are offered, where events are defined as guarded symbolic transitions. The framework considers input/output reactive infinite-state systems to satisfy safety and optimization objectives. Effective algorithms and safety control policies are offered to solve the safety control problem (i.e., satisfy the safety objective) for input/output infinite-state systems. Another contribution in this work provides optimization targets within a given cost function based on state transitions, without specifying the target states. The framework is then applied to power grids to demonstrate the effectiveness of the symbolic transition models and experimentally evaluate the new control algorithms. The results showed that the approach is very effective compared to other approaches found in the literature. The computation times required to achieve both safety and optimization objectives are obtained relatively quickly compared to other deterministic methods found in the literature.

Adaptation of Symbolic Discrete Control Synthesis for Energy-Efficient Multi-Pocket Milling

In engineering, cost minimization, especially in Computer Numerical Control (CNC) machining like pocket milling, is crucial. Existing tool path definition software often lacks optimization, particularly at critical starting and ending points. This study optimizes CNC machine tool paths for energy-efficient multi-pocket milling, utilizing the Symbolic Discrete Control Synthesis (SDCS) method for formal correctness. In our work, the tool path generation is formulated as a traveling salesman problem. We introduce a modeling framework to adapt SDCS to multi-pocket-milling processes, aiming to enhance precision and efficiency for potential cost savings, including energy and time, in engineering applications. This study reports experimental and comparative results, where comparative evaluations were made using metaheuristic algorithms. Our proposed approach improves CNC machining processes for multi-pocket milling. We experimentally evaluate our control algorithms and demonstrate and validate our approach through case studies.

Synthesis Methodology for Discrete MIMO PID Controller with Loop Shaping on LTV Plant Model via Iterated LMI Restrictions

This paper presents a methodology for synthesizing discrete MIMO PID controllers through iterative solutions of LMIs. It justifies the necessity of direct synthesis of discrete controllers in digital control systems. The proposed methodology allows for synthesizing an LTI controller for an LTV plant model, ensuring the robust stability of the synthesized system. Robustness is further ensured by the small-gain theorem and a novel approach to loop shaping, enabling the use of arbitrary shape functions. As a result, this methodology provides a broad statement of the problem with performance criteria necessary for practical application in control systems. Numerical examples are used to illustrate the methodology, which is implemented using the MATLAB toolbox, freely available for use.

Traffic Management System With Symbolic Discrete Controller Synthesis Technique

Traffic Management System With Symbolic Discrete Controller Synthesis Technique

Synthesis of Non-blocking Controllers for Linear Temporal Logic Tasks under Partial Observations⋆

In this paper, we investigate the formal synthesis of discrete controllers for linear temporal logic tasks under partial information. Existing works on this topic mainly focus on find sure winning or almost sure winning control strategies under some assumptions regarding the system's atomic propositions. In this work, we consider non-blockingness as the metric as the achievement of the task. Specifically, we require that at each instant, the controller maintains the possibility to achieve the LTL task under some environment's behavior. We first present an offline algorithm for the computation of the winning region over the belief state space. Then we present an online control algorithm that effective solves the control synthesis problem. The proposed control algorithm is also illustrated by a case study of robot task planning.

Discrete controller synthesis applied to smart greenhouse

The popularization of the Internet of Things allowed the emergence of different monitoring and control solutions in different economic sectors. For example, in agriculture, this type of technology has supported the monitoring of environmental variables essential in decision-making, defining when and how much water to use in a given crop. Besides, it made it possible to control various devices to meet each crop type's environmental requirements, increasing productivity. In this sense, there is a need for increasingly improved control strategies to meet crop requirements in real-time, ensuring sustainable production and reliable quality. This work presents Discrete Event System techniques to develop an agricultural greenhouse controller considering self-configuring mechanisms for adapting to dynamic environments and preventing conflicting rules from violating control objectives. The controller was validated through a simulator based on temperature balance equations, allowing the environment's temperature control. We used accurate climate data from actual Brazilian meteorological stations to evaluate different control scenarios in the year's four seasons, checking the controller's efficiency and the control strategy adopted, guaranteeing the crop's thermal comfort and minimizing water loss. Applying this control technique, we achieved the crop's thermal comfort under 87% of the time, influencing the absolute humidity and evapotranspiration rates over 31 days. Besides, we were also able to reach 66% more energy efficiency than other approaches.

Assured automatic dynamic reconfiguration of business processes

In order to manage evolving organisational practice and maintain compliance with changes in policies and regulations, businesses must be capable of dynamically reconfiguring their business processes. However, such dynamic reconfiguration is a complex, human-intensive and error prone task. Not only must new business process rules be devised but also, crucially, the transition between the old and new rules must be managed.In this paper we present a fully automated technique based on formal specifications and discrete event controller synthesis to produce correct-by-construction reconfiguration strategies. These strategies satisfy user-specified transition requirements, be they domain independent – such as delayed and immediate change – or domain specific. To achieve this, we provide a discrete-event control theoretic approach to operationalise declarative business process specifications, and show how this can be extended to resolve reconfiguration problems. In this way, given the old and the new business process rules described as Dynamic Condition Response Graphs, and given the transition requirements described with linear temporal logic, the technique produces a control strategy that guides the organisation through a business process reconfiguration ensuring that all transition requirements and process rules are satisfied. The technique outputs a reconfiguration DCR whose traces reproduce the controller’s reconfiguration strategy. We illustrate and validate the approach using realistic cases and examples from the BPM Academic Initiative.

Pendulum Accelerometer with Digital Control and New Functionality

In this paper, we consider a compensation-type quartz pendulum accelerometer, a feature of which is the use of a digital feedback amplifier in the control loop (for the implementation of a discrete controller and algorithmic compensation for errors from the pendulum unbalance and temperature dependences of the zero offset and scale factor). The problem is related to the construction of a digital control system for the considered accelerometer, which provides a high-precision measurement of the projection onto the sensitivity axis of the actual apparent acceleration of the object on which the accelerometer is installed. A solution to this problem, which allows finding digital control algorithms using various methods of synthesis of discrete controllers of the control loop, is provided. The obtained solutions in the time and frequency domains are analyzed, confirming the high quality of regulation. The results of experimental studies are presented.

Dynamic Update of Discrete Event Controllers

Discrete event controllers are at the heart of many software systems that require continuous operation. Changing these controllers at runtime to cope with changes in its execution environment or system requirements change is a challenging open problem. In this paper we address the problem of dynamic update of controllers in reactive systems. We present a general approach to specifying correctness criteria for dynamic update and a technique for automatically computing a controller that handles the transition from the old to the new specification, assuring that the system will reach a state in which such a transition can correctly occur and in which the underlying system architecture can reconfigure. Our solution uses discrete event controller synthesis to automatically build a controller that guarantees both progress towards update and safe update.

Synthesis of Discrete Modal SISO Controllers by Engineering Performance Indices

The linear discrete minimum-phase plant with one control input, one measured output and with an unmeasured external disturbance is considered. The problem is stated of the design of the discrete output controller that provides the preset engineering performance indices: control error, settling time, stability margins radius. Analytical formulas are obtained that allow to relate the engineering performance indices with the desired closed system characteristic polynomial roots in the modal control problem when choosing real non-negative roots. At the same time, the specified control error and the settling time lead to the constraints on the maximum absolute value of the desired roots, while the values of the desired roots, providing the given stability margins radius, may not satisfy these constraints, so the specified values of the performance indices should be revised. Examples are given showing the effectiveness of the approach proposed.

ALGORITHMS FOR SYNTHESIS OF DISCRETE CONTROLLERS IN NONLINEAR CONTROL SYSTEMS WITH DELAY

Algorithms for the synthesis of discrete controllers in nonlinear control systems, taking into account the delay, have been proposed. The synthesized vector controller provides a solution to the control problem, for example, the translation of the image point of a closed system from arbitrary initial conditions to the origin of the phase space coordinates. Built on the basis of a series-parallel set of invariant manifolds, the dynamic discrete controller ensures the fulfillment of the specified technological requirements, the asymptotic stability of a closed discrete-continuous system, and has the property of predicting the behavior of the system after sampling. These algorithms have made it possible to effectively solve the problems of synthesis of discrete controllers, taking into account the delay in process control systems.

A Case for Symbolic Limited Optimal Discrete Control: Energy Management in Reactive Data-flow Circuits

Abstract We present a framework for achieving efficient dynamic management of configurable reactive data-flow circuits subject to global design objectives such as mutual exclusion on shared resources and minimization of energy consumption. We propose a new symbolic controller synthesis algorithm that targets the optimization of a cost function summed over a sliding window of a given number of reactions of the system. We then present a technique for constructing symbolic models of configurable data-flow circuits that lends itself to the automatic computation of dynamic configuration controllers. We use these models to experimentally evaluate our control algorithm, and make the case for symbolic optimal discrete controller synthesis on such designs.

Symbolic Limited Lookahead Control for Best-effort Dynamic Computing Resource Management

We put forward a new modeling technique for Dynamic Resource Management (DRM) based on discrete events control for symbolic logico-numerical systems, especially Discrete Controller Synthesis (DCS). The resulting models involve state and input variables defined on an infinite domain (Integers), thereby no exact DCS algorithm exists for safety control. We thus formally define the notion of limited lookahead, and associated best-effort control objectives targeting safety and optimization on a sliding window for a number of steps ahead. We give symbolic algorithms, illustrate our approach on an example model for DRM, and report on performance results based on an implementation in our tool ReaX.

Exercising Symbolic Discrete Control for Designing Low-power Hardware Circuits: an Application to Clock-gating

We devise a tool-supported framework for achieving power-efficiency of hardware chips from high-level designs described using the popular hardware description language Verilog. We consider digital circuits as hierarchical compositions of sub-circuits, and achieve power-efficiency by switching-off the clock of each sub-circuit according to some clock-gating logic. We encode the computation of the latter as several small symbolic discrete controller synthesis problems, and use the resulting controllers to derive power-efficient versions from original circuit designs. We detail and illustrate our approach using a running example, and validate it experimentally by deriving a low-power version of an actual Reed-Solomon decoder.

A domain-specific language for the control of self-adaptive component-based architecture

Self-adaptive behaviors in the context of Component-based Architecture are generally designed based on past monitoring events, configurations (component assemblies) as well as behavioural programs defining the adaptation logics and invariant properties. Providing assurances on the navigation through the configuration space remains a challenge. That requires taking decisions on predictions on the possible futures of the system in order to avoid going into branches of the behavioural program leading to bad configurations. We propose the design of self-adaptive software components based on logical discrete control approaches, in which the self-adaptive behavioural models enrich component controllers with a knowledge not only on events, configurations and past history, but also with possible future configurations. This article provides the description, implementation and discussion of Ctrl-F, a Domain-specific Language whose objective is to provide high-level support for describing these control policies. Ctrl-F is formally defined by translation to Finite State Automata models, which allow for the exploration of behavioural programs by verification or Discrete Controller Synthesis, i.e., by automatically generating a controller to enforce correct self-adaptive behaviours. We integrate Ctrl-F with FraSCAti, a Service Component Architecture middleware platform and we illustrate the use of Ctrl-F by applying it to two case studies.

On the Design of Discrete Time Repetitive Controllers in Closed Loop Configuration

This paper deals with a discrete time repetitive control synthesis for non minimum phase plants. Two parts can be distinguished. The main design features of the repetitive controllers are discussed in the first part. More precisely one shows that one can realize two objectives; tracking with zero error and tracking with nonzero error. In the second part, a suitable plant model identification procedure for the repetitive control is proposed. An adequate input-output identification filter is designed such that the difference between the nominal and the actual repetitive control convergence conditions is minimized. Some illustrative examples are given to highlight the main features of the proposed approach.

Designing Autonomic Management Systems by Using Reactive Control Techniques

The ever growing complexity of software systems has led to the emergence of automated solutions for their management. The software assigned to this work is usually called an Autonomic Management System (AMS). It is ordinarily designed as a composition of several managers, which are pieces of software evaluating the dynamics of the system under management through measurements (e.g., workload, memory usage), taking decisions, and acting upon it so that it stays in a set of acceptable operating states. However, careless combination of managers may lead to inconsistencies in the taken decisions, and classical approaches dealing with these coordination problems often rely on intricate and ad hoc solutions. To tackle this problem, we take a global view and underscore that AMSs are intrinsically reactive, as they react to flows of monitoring data by emitting flows of reconfiguration actions. Therefore we propose a new approach for the design of AMSs, based on synchronous programming and discrete controller synthesis techniques. They provide us with high-level languages for modeling the system to manage, as well as means for statically guaranteeing the absence of logical coordination problems. Hence, they suit our main contribution, which is to obtain guarantees at design time about the absence of logical inconsistencies in the taken decisions. We detail our approach, illustrate it by designing an AMS for a realistic multi-tier application, and evaluate its practicality with an implementation.

Synthesizing safe control-command systems out of reusable components

This paper presents a safe design method for control-command embedded systems. It investigates the problem of building control-command systems out of Commercial off the shelf (COTS) components. The design method proposed uses in synergy the formal verification (FV) and the Discrete Controller Synthesis (DCS) techniques. COTS are formally specified using temporal logic and/or executable observers. New functions are built by assembling COTS together. As the COTS assembly operation is seldom error-free, behavioral incompatibilities may persist between COTS. For these reasons, COTS assemblies need to be formally verified and if errors are found, an automatic correction is attempted using DCS. The control-command code generated by DCS needs hardware specific post-processing: a structural decomposition, followed by a controllability assessment, followed by a dedicated formal verification step, ensuring that no spurious behavior is added by DCS. The resulting system is ready for hardware (e.g. FPGA) implementation.