19,584 research outputs found
System Level Synthesis
This article surveys the System Level Synthesis framework, which presents a
novel perspective on constrained robust and optimal controller synthesis for
linear systems. We show how SLS shifts the controller synthesis task from the
design of a controller to the design of the entire closed loop system, and
highlight the benefits of this approach in terms of scalability and
transparency. We emphasize two particular applications of SLS, namely
large-scale distributed optimal control and robust control. In the case of
distributed control, we show how SLS allows for localized controllers to be
computed, extending robust and optimal control methods to large-scale systems
under practical and realistic assumptions. In the case of robust control, we
show how SLS allows for novel design methodologies that, for the first time,
quantify the degradation in performance of a robust controller due to model
uncertainty -- such transparency is key in allowing robust control methods to
interact, in a principled way, with modern techniques from machine learning and
statistical inference. Throughout, we emphasize practical and efficient
computational solutions, and demonstrate our methods on easy to understand case
studies.Comment: To appear in Annual Reviews in Contro
Optimal Distributed Controller Synthesis for Chain Structures: Applications to Vehicle Formations
We consider optimal distributed controller synthesis for an interconnected
system subject to communication constraints, in linear quadratic settings.
Motivated by the problem of finite heavy duty vehicle platooning, we study
systems composed of interconnected subsystems over a chain graph. By
decomposing the system into orthogonal modes, the cost function can be
separated into individual components. Thereby, derivation of the optimal
controllers in state-space follows immediately. The optimal controllers are
evaluated under the practical setting of heavy duty vehicle platooning with
communication constraints. It is shown that the performance can be
significantly improved by adding a few communication links. The results show
that the proposed optimal distributed controller performs almost as well as the
centralized linear quadratic Gaussian controller and outperforms a suboptimal
controller in terms of control input. Furthermore, the control input energy can
be reduced significantly with the proposed controller compared to the
suboptimal controller, depending on the vehicle position in the platoon. Thus,
the importance of considering preceding vehicles as well as the following
vehicles in a platoon for fuel optimality is concluded
Localized LQR Optimal Control
This paper introduces a receding horizon like control scheme for localizable
distributed systems, in which the effect of each local disturbance is limited
spatially and temporally. We characterize such systems by a set of linear
equality constraints, and show that the resulting feasibility test can be
solved in a localized and distributed way. We also show that the solution of
the local feasibility tests can be used to synthesize a receding horizon like
controller that achieves the desired closed loop response in a localized manner
as well. Finally, we formulate the Localized LQR (LLQR) optimal control problem
and derive an analytic solution for the optimal controller. Through a numerical
example, we show that the LLQR optimal controller, with its constraints on
locality, settling time, and communication delay, can achieve similar
performance as an unconstrained H2 optimal controller, but can be designed and
implemented in a localized and distributed way.Comment: Extended version for 2014 CDC submissio
Distributed Control with Low-Rank Coordination
A common approach to distributed control design is to impose sparsity
constraints on the controller structure. Such constraints, however, may greatly
complicate the control design procedure. This paper puts forward an alternative
structure, which is not sparse yet might nevertheless be well suited for
distributed control purposes. The structure appears as the optimal solution to
a class of coordination problems arising in multi-agent applications. The
controller comprises a diagonal (decentralized) part, complemented by a
rank-one coordination term. Although this term relies on information about all
subsystems, its implementation only requires a simple averaging operation
Provably safe cruise control of vehicular platoons
We synthesize performance-aware safe cruise control policies for longitudinal motion of platoons of autonomous vehicles. Using set-invariance theories, we guarantee infinite-time collision avoidance in the presence of bounded additive disturbances, while ensuring that the length and the cruise speed of the platoon are bounded within specified ranges. We propose: 1) a centralized control policy and 2) a distributed control policy, where each vehicle's control decision depends solely on its relative kinematics with respect to the platoon leader. Numerical examples are included.NSF; CPS-1446151; CMMI-1400167; FA 9550-15-1-0186 - AFOSR; Schlumberger Foundation Faculty for the Future Fellowship; FA 9550-15-1-0186 - AFOSR; NSF; ECCS-1550016; CNS 123922
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