17,163 research outputs found
Safety-Critical Control Synthesis for network systems with Control Barrier Functions and Assume-Guarantee Contracts
This paper presents a contract based framework for safety-critical control synthesis for network systems. To handle the large state dimension of such systems, an assume-guarantee contract is used to break the large synthesis problem into smaller subproblems. Parameterized signal temporal logic (pSTL) is used to formally describe the behaviors of the subsystems, which we use as the template for the contract. We show that robust control invariant sets (RCIs) for the subsystems can be composed to form a robust control invariant set for the whole network system under a valid assume-guarantee contract. An epigraph algorithm is proposed to solve for a contract that is valid, ---an approach that has linear complexity for a sparse network, which leads to a robust control invariant set for the whole network. Implemented with control barrier function (CBF), the state of each subsystem is guaranteed to stay within the safe set. Furthermore, we propose a contingency tube Model Predictive Control (MPC) approach based on the robust control invariant set, which is capable of handling severe contingencies, including topology changes of the network. A power grid example is used to demonstrate the proposed method. The simulation result includes both set point control and contingency recovery, and the safety constraint is always satisfied
Compositional Set Invariance in Network Systems with Assume-Guarantee Contracts
This paper presents an assume-guarantee reasoning approach to the computation
of robust invariant sets for network systems. Parameterized signal temporal
logic (pSTL) is used to formally describe the behaviors of the subsystems,
which we use as the template for the contract. We show that set invariance can
be proved with a valid assume-guarantee contract by reasoning about individual
subsystems. If a valid assume-guarantee contract with monotonic pSTL template
is known, it can be further refined by value iteration. When such a contract is
not known, an epigraph method is proposed to solve for a contract that is
valid, ---an approach that has linear complexity for a sparse network. A
microgrid example is used to demonstrate the proposed method. The simulation
result shows that together with control barrier functions, the states of all
the subsystems can be bounded inside the individual robust invariant sets.Comment: Submitted to 2019 American Control Conferenc
Compositional Set Invariance in Network Systems with Assume-Guarantee Contracts
This paper presents an assume-guarantee reasoning approach to the computation of robust invariant sets for network systems. Parameterized signal temporal logic (pSTL) is used to formally describe the behaviors of the subsystems, which we use as the template for the contract. We show that set invariance can be proved with a valid assume-guarantee contract by reasoning about individual subsystems. If a valid assume-guarantee contract with monotonic pSTL template is known, it can be further refined by value iteration. When such a contract is not known, an epigraph method is proposed to solve for a contract that is valid, -an approach that has linear complexity for a sparse network. A microgrid example is used to demonstrate the proposed method. The simulation result shows that together with control barrier functions, the states of all the subsystems can be bounded inside the individual robust invariant sets
Controller Synthesis of Collaborative Signal Temporal Logic Tasks for Multi-Agent Systems via Assume-Guarantee Contracts
This paper considers the problem of controller synthesis of signal temporal
logic (STL) specifications for large-scale multi-agent systems, where the
agents are dynamically coupled and subject to collaborative tasks. A
compositional framework based on continuous-time assume-guarantee contracts is
developed to break the complex and large synthesis problem into subproblems of
manageable sizes. We first show how to formulate the collaborative STL tasks as
assume-guarantee contracts by leveraging the idea of funnel-based control. The
concept of contracts is used to establish our compositionality result, which
allows us to guarantee the satisfaction of a global contract by the multi-agent
system when all agents satisfy their local contracts. Then, a closed-form
continuous-time feedback controller is designed to enforce local contracts over
the agents in a distributed manner, which further guarantees the global task
satisfaction based on the compositionality result. Finally, the effectiveness
of our results is demonstrated by two numerical examples.Comment: arXiv admin note: substantial text overlap with arXiv:2203.1004
Multi-Rate Control Design Leveraging Control Barrier Functions and Model Predictive Control Policies
In this letter we present a multi-rate control architecture for safety critical systems. We consider a high level planner and a low level controller which operate at different frequencies. This multi-rate behavior is described by a piecewise nonlinear model which evolves on a continuous and a discrete level. First, we present sufficient conditions which guarantee recursive constraint satisfaction for the closed-loop system. Afterwards, we propose a control design methodology which leverages Control Barrier Functions (CBFs) for low level control and Model Predictive Control (MPC) policies for high level planning. The control barrier function is designed using the full nonlinear dynamical model and the MPC is based on a simplified planning model. When the nonlinear system is control affine and the high level planning model is linear, the control actions are computed by solving convex optimization problems at each level of the hierarchy. Finally, we show the effectiveness of the proposed strategy on a simulation example, where the low level control action is updated at a higher frequency than the high level command
Multi-Rate Control Design Leveraging Control Barrier Functions and Model Predictive Control Policies
In this paper we present a multi-rate control architecture for safety
critical systems. We consider a high level planner and a low level controller
which operate at different frequencies. This multi-rate behavior is described
by a piecewise nonlinear model which evolves on a continuous and a discrete
level. First, we present sufficient conditions which guarantee recursive
constraint satisfaction for the closed-loop system. Afterwards, we propose a
control design methodology which leverages Control Barrier Functions (CBFs) for
low level control and Model Predictive Control (MPC) policies for high level
planning. The control barrier function is designed using the full nonlinear
dynamical model and the MPC is based on a simplified planning model. When the
nonlinear system is control affine and the high level planning model is linear,
the control actions are computed by solving convex optimization problems at
each level of the hierarchy. Finally, we show the effectiveness of the proposed
strategy on a simulation example, where the low level control action is updated
at a higher frequency than the high level command
- …