Command Governor Strategy Research Articles

Ellipsoidal Set-Based Extended Command Governor for Constrained Linear Systems With Bounded Disturbances

The purposes of this paper are twofold. The first is to derive a convex formulation for optimizing the fictitious dynamics of the extended command governor strategy recently proposed in [1]. The second purpose is to provide an efficient procedure to solve online the optimization problem of the ellipsoidal set based command governor or the extended command governor. Two numerical examples with comparison to earlier solutions from the literature illustrate the effectiveness of the proposed algorithm.

ROTEC: Robust to early termination command governor for systems with limited computing capacity

A Command Governor (CG) is an optimization-based add-on scheme to a nominal closed-loop system. It is used to enforce state and control constraints by modifying reference commands. This paper considers the implementation of a CG on embedded processors that have limited computing resources and must execute multiple control and diagnostics functions; consequently, the time available for CG computations is limited and may vary over time. To address this issue, a robust to early termination command governor is developed which embeds the solution of a CG problem into the internal states of a virtual continuous-time dynamical system which runs in parallel to the process. This virtual system is built so that its trajectory converges to the optimal solution (with a tunable convergence rate), and provides a sub-optimal but feasible solution whenever its evolution is terminated. This allows the designer to implement a CG strategy with a small sampling period (and consequently with a minimum degradation in its performance), while maintaining its constraint-handling capabilities. Simulations are carried out to assess the effectiveness of the developed scheme in satisfying performance requirements and real-time schedulability conditions for a practical vehicle rollover example.

Command Governor Strategy Based on Region of Attraction

Command Governor Strategy Based on Region of Attraction

Turn-Based Supervision Architectures for Dynamic Networks involving Plug-and-Play Operations

Abstract In this note, we consider a novel supervision algorithm for the distributed management of interconnected linear systems sharing coupling coordination constraints. The proposed supervision approach is based on the recently developed Turn-Based Command Governor strategy (Casavola et al. (2018)) where the agents in the networks follow a particular round-robin policy in updating their commands. Such a strategy is here extended to deal with so called Plug-and-Play (PnP) operations. Such a problem has been faced in a formal way by providing the conditions that allow PnP operations without violating existing constraints. In this respect, the notation of Pluggability of systems that aim at joining the same network is introduced as a structural property. A final example is presented to illustrate the effectiveness of the proposed strategy.

A distributed command governor based on graph colorability theory

SummaryIn this paper, a distributed command governor (CG) strategy is introduced that, by the use of graph colorability theory, improves the scalability property and the performance of recently introduced distributed noncooperative sequential CG strategies. The latter are characterized by the fact that only 1 agent at a decision time is allowed to update its command, whereas all the others keep applying their previously computed commands. The scalability of these early CG distributed schemes and their performance are limited because the structure of the constraints is not taken into account in their implementation. Here, by exploiting the idea that agents that are not directly coupled by the constraints can simultaneously update their control actions, the agents in the network are grouped into particular subsets (turns). At each time instant, on the basis of a round‐robin policy, all agents belonging to a turn are allowed to update simultaneously their commands, whereas agents in other turns keep applying their previous commands. Then, a turn‐based distributed CG strategy is proposed and its main properties are analyzed. Graph colorability theory is used to determine the minimal number of turns and to distribute each agent in at least a turn. A novel graph colorability problem that allows one to maximize the frequency at which agents can update their commands is proposed and discussed. A final example is presented to illustrate the effectiveness of the proposed strategy.

Command Governor Strategies for the Online Management of Reactive Power in Smart Grids With Distributed Generation

High penetration of distributed generation (DG) in medium voltage (MV) power grids may easily lead to abrupt voltage raises in the presence of either low demand conditions or high power production from renewable sources. In order to cope with the possibly occurring voltage limit violation, the active power injected by the distributed generators is typically curtailed, being, however, such an approach suboptimal from an economical point of view and presenting several other disadvantages. To address this issue, the online management and coordination of the reactive power injected/absorbed by the distributed generators acting on the grid are proposed here. The approach is based on command governor ideas that are used here to optimally solve constrained voltage control problems in both centralized and distributed ways. The approach foresees an active coordination between some controllable devices of the grid, e.g., distributed generators and MV/high voltage transformers, in order to maintain relevant system variables within prescribed operative constraints in response to unexpected adverse conditions. Simulation results show that the proposed approach is more effective than approaches suggested by the current Italian norms on DGs connection.

A Distributed Multi-Agent Command Governor Strategy for the Coordination of Networked Interconnected Systems

A novel distributed coordination strategy is presented for networked, locally regulated and possibly dynamically coupled, interconnected systems. Such systems are assumed to be connected via data links and subject to pointwise-in-time global constraints on some relevant variables of them, to be enforced as a coordination goal along the overall system evolutions. Such a coordination-by-constraint paradigm is accomplished by resorting to a novel distributed multi-agent Command Governor (CG) approach where each agent is in charge to locally modify, whenever necessary and on the basis of a reduced amount of data exchanged with the other agents, the prescribed set-points to the regulated subsystems so that the coordination constraints are always satisfied. The strategy is described and its main properties analyzed, especially for what it concerns the stability, feasibility and Pareto optimality of the solution. A liveness analysis concerning the possible presence of undesirable Nash equilibria and/or deadlock situations is presented and a discussion on the scalability of the solution with the problem dimension is reported as well. The constrained coordination of a network of interconnected water tanks is presented as a final example in order to show the effectiveness of the proposed strategy.

Improved Feed-Forward Command Governor Strategies for Constrained Discrete-Time Linear Systems

This technical note presents an improved version of the Feed-Forward Command Governor (FF-CG) strategy recently proposed in for the supervision of input/state constrained discrete-time linear systems subject to bounded disturbances, whose main feature is not to require any explicit on-line measure (or estimation) of the state for its implementation. Although effective also in the case of bounded disturbances, the performance of earlier FF-CG schemes was mainly limited by the fact that such strategies were required to maintain constant their actions for a prescribed number of sampling steps. Here such a restriction is removed and the proposed FF-CG solution is allowed to update its action at each sampling step. Numerical simulations on a physical plant have been undertaken and comparisons with other strategies have been reported in order to show the effectiveness of the proposed approach.

Scalability and Performance Improvement of Distributed Sequential Command Governor Strategies via Graph Colorability Theory

Graph colorability theory is shown here to be instrumental for the improvement of scalability and performance of recently introduced distributed non-cooperative sequential Command Governor (CG) strategies. Such properties were limited in earlier distributed CG schemes because the structure of constraints was not taken into account in their implementation. Here, by exploiting the idea that agents that are not jointly involved in any coupling constraint can simultaneously update their control actions, this is done by grouping all agents in the network into particular subsets (Turns) and allowing all agents belonging to a single turn to update simultaneously their commands while agents in other turns are instructed to keep applying their current commands. Graph colorability concepts and results are used to determine the minimum number of independent turns and distribute exclusively agents into them. A Turn-Based distributed CG strategy is therefore proposed and its main properties analyzed. A final example is also presented to illustrate the effectiveness of the proposed strategy by comparisons.

A Distributed Parallel Command Governor Strategy for the Coordination of Multi-agent Networked Systems

A novel distributed Parallel Feedback Command Governor (FB-CG) supervision strategy is presented for multi-agent interconnected networked systems subject to pointwise-in-time constraints which need to be enforced during the overall system operations for coordination purposes. The paper extends some recent results related to this coordination-by-constraint approach by resorting to and extending Sequential Distributed Command Governor ideas. This novel Parallel distributed strategy is fully described and analyzed and it is compared with earlier Parallel Feed-Forward Command Governor (FF-CG) strategies in the final example.

A FeedForward Command Governor Strategy for Constrained Linear Systems

This paper proposes a novel class of Command Governor (CG) strategies for input/state constrained linear systems subject to bounded disturbances in the absence of explicit state measurement or its estimation. While in traditional CG schemes, the setpoint manipulation is undertaken on the basis of either the actual measure of the state or of its suitable estimation, it is shown here that the CG design problem can be solved with limited performance degradation and with similar properties also in the case that such an explicit measure is not available, by forcing the state evolutions to stay “not too far” from the manifold of feasible steady-states. This approach, which will be referred to as Feed Forward CG (FF-CG), may be a convenient alternative CG solution in all situations whereby the cost of measuring the state may be a severe limitation, e.g. in distributed or decentralized applications. In order to evaluate the method here proposed, numerical simulations on a physical plant have been performed and comparisons with the standard state-feedback CG solution reported.

Distributed collision avoidance for interacting vehicles: a command governor approach

This paper deals with a distributed coordination problem including collision avoidance. The problem is solved by using a Command Governor strategy based on mixed integer optimization. First, we present an algorithm to find an appropriate command in the centralized case, then a distributed sequential procedure is described. Simulations are reported for comparisons.

A command governor approach for voltage regulation of medium voltage distribution networks

In this paper a Command Governor strategy is used for voltage regulation in Medium and Low Voltage (MV/LV) distribution networks subject to load voltage drops. The voltage regulation is formulated as a constrained tracking problem by imposing that the voltages at the LV customer loads have minimum deviation from their nominal values, each other compatible with prescribed bounds on their maximum deviations. Simulations studies show the effectiveness of the proposed approach.