Datta N. Godbole

Verified hybrid controllers for automated vehicles

The objective of an automated highway system (AHS) is to increase the safety and throughput of the existing highway infrastructure by introducing traffic automation. AHS is an example of a large scale, multiagent complex dynamical system and is ideally suited for a hierarchical hybrid controller. We discuss the design of safe and efficient hybrid controllers for regulation of vehicles on an AHS. We use game theoretic techniques to deal with the multiagent and multiobjective nature of the problem. The result is a hybrid controller that by design guarantees safety, without the need for further verification. The calculations also provide an upper bound on the performance that can be expected in terms of throughput at various levels of centralization.

Decentralized Receding Horizon Control and Coordination of Autonomous Vehicle Formations

This paper describes the application of a novel methodology for high-level control and coordination of autonomous vehicle teams and its demonstration on high-fidelity models of the organic air vehicle developed at Honeywell Laboratories. The scheme employs decentralized receding horizon controllers that reside on each vehicle to achieve coordination among team members. An appropriate graph structure describes the underlying communication topology between the vehicles. On each vehicle, information about neighbors is used to predict their behavior and plan conflict-free trajectories that maintain coordination and achieve team objectives. When feasibility of the decentralized control is lost, collision avoidance is ensured by invoking emergency maneuvers that are computed via invariant set theory.

Network-Centric Systems for Military Operations in Urban Terrain: The Role of UAVs

Military systems are the motivational driver for much of the technology development conducted at applied research laboratories around the world. As the needs of the worlds militaries change, so does the focus of this research and development. In this paper, we discuss how the fundamental characteristics of military operations in urban terrain (MOUT) impose requirements and constraints on sensing and reconnaissance. We highlight the importance of a new class of small unmanned aerial vehicles (UAVs) for network-centric military urban operations. We review some of the UAVs that have been developed in recent years, and that are under development, with particular attention to their endurance, portability, performance, payload, and communication capabilities. Selected university testbeds are also briefly noted. Over the last few years there has been considerable research focused on how these small UAVs, both individually and collectively, can operate autonomously in urban environments and help capture and communicate needed information. We discuss some of this research; specific topics covered include guidance and control for autonomous operation, multi-UAV coordination and route optimization, and ad-hoc networking with UAV nodes. A new concept of operations is described that relies on coordination and control of a heterogeneous suite of small UAVs for surveillance and reconnaissance operations in urban terrain

A game-theoretic approach to hybrid system design

We present a design and verification methodology for hybrid dynamical systems. Our approach is based on optimal control and game theory. The hybrid design is seen as a game between two players. One is the disturbances that enter the dynamics. The disturbances can encode the actions of other agents (in a multi-agent setting), the actions of high level controllers or unmodeled environmental disturbances. The second player is the control, which is to be chosen by the designer. The two players compete over cost functions that encode the properties that the closed loop hybrid system needs to satisfy (e.g. safety). The control “wins” the game if it can keep the system “safe” for any allowable disturbance. The solution to the game theory problem provides the designer with continuous controllers as well as sets of safe states where the control “wins” the game. These safe sets can be used to construct an interface that guarantees the safe operation of the combined hybrid system. Extensions of this approach can also be used for verification of hybrid systems as well as the generation of abstractions of the lower layer behavior (e.g. timed abstractions).

SAFETY AND CAPACITY ANALYSIS OF AUTOMATED AND MANUAL HIGHWAY SYSTEMS

This paper compares safety of automated and manual highway systems with respect to result- ing rear-end collision frequency and severity. The results show that automated driving is safer than the most alert manual drivers, at similar speeds and capacities. We also present a detailed safety-capacity tradeo study for four di erent Automated Highway System concepts that di er in their information structure and separation policy.

A fault tolerant control architecture for automated highway systems

A hierarchical controller for dealing with faults and adverse environmental conditions on an automated highway system is proposed. The controller extends a previous control hierarchy designed to work under normal conditions of operation. The faults are classified according to the capabilities remaining on the vehicle or roadside after the fault has occurred. Information about these capabilities is used by supervisors in each of the layers of the hierarchy to select appropriate fault handling strategies. We outline the strategies needed by the supervisors and give examples of their detailed operation.

Energy management for buildings and microgrids

Intelligent consumer energy management systems will become important elements at the delivery points of the smart grid inside homes, buildings, and industrial plants. The end users will be able to better monitor and manage their energy consumption, while utilities will gain more flexible mechanisms for management of peak demands that will extend beyond demand response initiatives as they are implemented today. With a broader use of distributed generation many buildings and campuses will become microgrids interconnecting multiple generation, storage, and consumption devices of one or several end users. We discuss how energy management and control for such facilities can be viewed as a large-scale optimization problem. Specific supply-side and demand-side aspects include on-site renewable generation, storage technologies, electric cars, dynamic pricing, and load management. Technical challenges related to the optimization formulation are noted - in general, mixed-integer, nonlinear, constrained optimization is needed. We also describe an implementation of optimization-based energy management solution for a hospital in the Netherlands, providing economic details and an analysis of the savings achieved.

Hybrid decentralized control of large scale systems

Motivated by three applications which are under investigation at the Honeywell Research Laboratory in Minneapolis, we introduce a class of large scale control problems. In particular we show that a formation flight problem, a paper machine control problem and the coordination of cameras in a monitoring network can be cast into this class. In the second part of the paper we propose a decentralized control scheme to tackle the complexity of the problem. The scheme makes use of logic rules which improve stability and feasibility of the decentralized method by enforcing coordination. The decentralized control laws which respect the rules are computed using hybrid control design.

Capacity Analysis of Traffic Flow Over a Single-Lane Automated Highway System⋆

The paper calculates bounds on per-lane Automated Highway System (AHS) capacity as a function of vehicle capabilities and control system information structure. It assumes that the AHS lane is dedicated for use by fully automated vehicles. Capacity is constrained by the minimum inter-vehicle separation necessary for safe operation. A methodology for deriving the safe minimum inter-vehicle separation for a particular safety criterion is presented. The inter-vehicle separation, which depends on the vehicle braking capability, control loop delays and operating speed, is then used to compute site-independent upper bounds on AHS capacity for a given mix of vehicle classes. The sensitivity of the capacity with respect to the degree of inter-vehicle cooperation, check-in policies (governing minimum acceptable vehicle braking capability), highway speed limits, and lane-use policies (governing the sharing of a lane by multiple vehicle classes) is also investigated.

A verified hybrid controller for automated vehicles

Considerable experimental and theoretical research has been carried out in an attempt to design an automated highway system that can provide more efficient utilization of the highways and at the same time be safer and more comfortable than the current highway system. Here we present a unified framework for carrying out safety calculations for the automated highway problem. We obtain sufficient conditions for a set of continuous controllers to be safe and use these conditions to design a discrete scheme that switches between them. Guarantees of safety for the closed loop hybrid system follow by design.