<p>Multi-robot systems have important applications, such as space explorations, underwater missions, and surveillance operations. In most of these cases robots need to exchange data through communication. Limitations in the communication system however impose constraints on the design of coordination strategies. In this thesis we present three papers on cooperative control problems in which different communication constraints are considered. The first paper describes a rendezvous problem for a team of robots that exchanges position information through communication. A local control law for each robot should steer the team to a common meeting point when communicated data are quantized. The robots are not equipped with any sensors so the positions of other teammates are not measured. Two different types of quantized communication are considered: uniform and logarithmic. Logarithmic quantization is often preferable since it requires that fewer bits are communicated compared to when uniform quantization is used. For a class of feasible communication topologies, control laws that solve the rendezvous problem are derived. A hierarchical control structure is proposed in the second paper, for modelling autonomous underwater vehicles employed in finding a minimum of a scalar field. The controller is composed of two layers. The upper layer is the team controller, which is modeled as discrete-event system. It generates waypoints based on the simplex search optimization algorithm. The waypoints are used as target points by the lower control layer, which continuously steers each vehicle from the current to the next waypoint. It is shown that the communication of measurements is needed at each step for the team controller to generate unique waypoints. A protocol is proposed to reduce the amount of data to be exchanged, motivated by that underwater communication is costly in terms of energy. In the third paper, a probabilistic pursuit{evasion game is considered as an example to study constrained communication in multi-robot systems. This system can be used to model search-and-rescue operations and multi-robot exploration. Communication protocols based on time-triggered and event-triggered synchronization schemes are considered. It is shown that by limiting the communication to events when the probabilistic map updated by the individual pursuer contains new information, as measured by a map entropy, the utilization of the communication link can be considerably improved compared to conventional time-triggered communication.</p>

Den här rapporten presenterar ett examensarbete där ett mätdatainsamlingssystem för dynamiska signaler har skapats. Arbetet har utförts på Siemens Industrial Turbomachinery AB. Problemet är av sådan natur att tre olika typer av signaler analyseras. Dessa signaler är dels dynamiska signaler med ett intressant frekvensinnehåll mellan 10 och 10 000 Hz, dels likspänningssignaler och dels varvtalssignaler. Dessa signaler datasamplas och analyseras med avseende på både tids- och frekvensinnehåll. Resultatet skickas vidare till en server med en uppdateringsfrekvens kring 1 Hz. Arbetet har inneburit att en kravanalys av systemet har tagits fram utifrån ett redan existerande system och från intervjuer med tänkta användare av systemet. Utifrån den skapade kravprofilen valdes lämplig hårdvara och mjukvara implementerades med hjälp av LabVIEW. Resultatet blev ett system som lever väl upp till förväntningarna.

Diss. Uppsala : Uppsala universitet, 2007.

Licentiatavhandling Ronneby : Blekinge tekniska högskola, 2008.

Diss. (sammanfattning) Stockholm : Kungliga Tekniska högskolan, 2008.

Diss. Linköping : Univ., 2005.

Diss. Ronneby : Blekinge tekniska högskola, 2005.

Diss. Uppsala : Univ., 2002.

Diss. Uppsala : Univ., 2003.

Diss. Uppsala : Univ., 2005.