References of "Thunberg, Johan 50003198"
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See detailOptimal output consensus control and outlier detection
Thunberg, Johan UL; Hu, X.

in Proceedings of the 19th International Symposium on Mathematical Theory of Networks and Systems (2010)

In this paper we study the output consensus problem for systems of agents with linear continuous time invariant dynamics, and derive control laws that minimize a conical combination of the energies of the ... [more ▼]

In this paper we study the output consensus problem for systems of agents with linear continuous time invariant dynamics, and derive control laws that minimize a conical combination of the energies of the agents control signals, while only using local information. We show that the optimal control requires the connectivity graph to be complete and in general requires measurements of the state errors. We identify the cases where the optimal control is only based on output errors, and show that in the infinite time horizon case, the optimal control can always be expressed as a dynamic control that is only based on the output errors. We also give a Lemma for the position of the equilibrium point for a large class of agent dynamics. As a second part of this paper we consider the problem of outlier detection, in which an agent wants to deduce if an other agent is using the consensus controller, or if it is an outlier that uses a different controller. We introduce the outlier detection equation. [less ▲]

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See detailA comparative study of task assignment and path planning methods for multi-UGV missions
Thunberg, Johan UL; Anisi, D.; Ögren, P.

in Optimization and Cooperative Control Strategies (2009)

Many important problems involving a group of unmanned ground vehicles (UGVs) are closely related to the multi traviling salesman problem (m-TSP). This paper comprises a comparative study of a number of ... [more ▼]

Many important problems involving a group of unmanned ground vehicles (UGVs) are closely related to the multi traviling salesman problem (m-TSP). This paper comprises a comparative study of a number of algorithms proposed in the litterature to solve m-TSPs occuring in robotics. The investigated algoritms include two mixed integer linear programming (MILP) formulations, a market based approach (MA), a Voronoi partition step (VP) combined with the local search used in MA, and a deterministic and a stocastic version of the granular tabu search (GTS). To evaluate the algoritms, an m-TSP is derived from a planar environment with polygonal obstacles and uniformly distributed targets and vehicle positions. The results of the comparison indicate that out of the decentralized approaches, the MA yield good solutions but requires long computation times, while VP is fast but not as good. The two MILP approaches suffer from long computation times, and poor results due to the decomposition of the assignment and path planning steps. Finally, the two GTS algorithms yield good results in short times with inputs from MA as well as the much faster VP. Thus the best performing centralized approach is the GTS in combination with the VP. [less ▲]

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See detailTowards optimal positioning of surveillance UGVs
Nilsson, U.; Ögren, P.; Thunberg, Johan UL

in Optimization and Cooperative Control Strategies (2009)

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full ... [more ▼]

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full advantage of the flexibility and speed offered by a group of UGV platforms, a fast way to compute desired camera locations to cover an area or a set of buildings, e.g., in response to an alarm, is needed. Building upon earlier results in terrain guarding and sensor placement we propose a way to find candidate guard positions that satisfy a large set of view angle and range constraints simulataneously. Since the original problem is NP-complete, we do not seek to find the true optimal set of guard positions. Instead, a near optimal subset of the candidate points is chosen using a scheme with a known approximation ratio of O(log(n)). A number of examples are presented to illustrate the approach. [less ▲]

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See detailBlock Backstepping, NDI and Related Cascade Designs for Efficient Development of Nonlinear Flight Control Laws
Thunberg, Johan UL; Robinson, J.W.C.

in Proceedings of the AIAA Guidance, Navigation and Control Conference and Exhibit 2008 (2008)

A common feature of many aircraft configurations is that the actuation mainly effects the moments, and thereby the angular accelerations, whereas the desired normal acceleration is achieved by adjusting ... [more ▼]

A common feature of many aircraft configurations is that the actuation mainly effects the moments, and thereby the angular accelerations, whereas the desired normal acceleration is achieved by adjusting the location of the velocity vector in body coordinates. Thus, the main desired effects of the actuators appear after one integration, and if the actuators have dynamics the effect of the primary control variable occurs after more than one integration. This inherent cascade structure of many aircraft control problems is exploited in e.g. nonlinear dynamic inversion via time scale separation (NDI-TSS) to yield a powerful nonlinear design method. In the present work we present a family of multivariable (three axis) nonlinear cascade design techniques for flight control law design which includes block backstepping and NDI-TSS as special cases and we show that this family can offer a large design flexibility and excellent performance as well as short design cycles. We show stability for the family of techniques and illustrate the theory using simulations based on the ADMIRE model which is a realistic nonlinear model of an agile fighter with delta-canard configuration. [less ▲]

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See detailOptimal positioning of surveillance UGVs
Nilsson, U.; Ögren, P.; Thunberg, Johan UL

in Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (2008)

Unmanned ground vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full ... [more ▼]

Unmanned ground vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full advantage of the flexibility and speed offered by a group of UGV platforms, a fast way to compute desired camera locations that cover or surround a set of buildings e.g., in response to an alarm, is needed. In this paper we focus on two problems. The first is how to create a line-of-sight perimeter around a given set of buildings with a minimal number of UGVs. The second problem is how to find UGV positions such that a given set of walls are covered by the cameras while taking constraints in terms of zoom, range, resolution and field of view into account. For the first problem we propose a polynomial time algorithm and for the second problem we extend our previous work to include zoom cameras and furthermore provide a theoretical analysis of the approach itself. A number of examples are presented to illustrate the two algorithms. [less ▲]

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