Change search
ReferencesLink to record
Permanent link

Direct link
Communication-Aware Motion Planning for Mobile Robots
KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
2012 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

Mobile robots have found numerous applications in recent years, in areas such as consumer robotics, environmental monitoring, security and transportation. For information dissemination, multi-robot cooperation or operator intervention, reliable communications are important. The combination of communication constraints with other requirements in robotics, such as navigation and obstacle avoidance is called communication-aware motion planning. To facilitate integration, communication-aware methods should fit into traditional layered architectures of motion planning. This thesis contains two main contributions, applicable to such an architecture.

The first contribution is to develop strategies for exploiting multipath fading while following a reference trajectory. By deviating from the reference, a robot can stop and communicate at positions with high signal strength, trading tracking performance for link quality. We formulate this problem in three different ways: First we maximize the link quality, subject to deterministic bounds on the tracking error. We control the velocity based on the position and channel quality. Second, we consider probabilistic tracking error bounds and develop a cascaded control architecture that performs time-triggered stopping while regulating the tracking error. Third, we formulate a hybrid optimal control problem, switching between standing still to communicate and driving to improve tracking. The resulting channel quality is analyzed and we perform extensive experiments to validate the communication model and compare the proposed methods to the nominal case of driving at constant velocity. The results show good agreement with the model and improvements of over 100% in the throughput when the channel quality is low.

The second contribution is to plan velocities for a group of N robots, moving along pre-determined paths through an obstacle field. Robots can only communicate if they have an unobstructed line of sight, and the problem is to maintain connectivity while traversing the paths. This is mapped to motion planning in an N-dimensional configuration space. We propose and investigate two solutions, using a rapidly exploring random tree (RRT) and an exact method inspired by cell decomposition. The RRT method scales better with the problem size than the exact method, which has a worst-case time complexity that is exponential in the number of obstacles. But the randomization in the RRT method makes it difficult to set a timeout for the solver, which runs forever if a problem instance is unsolvable. The exact method, on the other hand, detects unsolvable problem instances in finite time.

The thesis demonstrates, both in theory and experiments, that mobile robots can improve communications by planning trajectories that maintain visual connectivity, or by exploiting multipath fading when there is no line of sight. The proposed methods are well suited for integration in a layered motion planning architecture.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , vii, 137 p.
Trita-EE, ISSN 1653-5146 ; 2012:002
Keyword [en]
autonomous systems, robotics, wireless sensor networks, motion planning, multipath fading
National Category
URN: urn:nbn:se:kth:diva-58781ISBN: 978-91-7501-234-6OAI: diva2:474046
Public defence
2012-02-10, F3, Lindstedtsvägen 26, KTH, Stockholm, 10:15 (English)
QC 20120117Available from: 2012-01-17 Created: 2012-01-09 Last updated: 2012-01-17Bibliographically approved

Open Access in DiVA

Thesis Magnus Lindhe(3862 kB)240 downloads
File information
File name FULLTEXT01.pdfFile size 3862 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Minnema Lindhé, Magnus
By organisation
Automatic ControlACCESS Linnaeus Centre

Search outside of DiVA

GoogleGoogle Scholar
Total: 240 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 384 hits
ReferencesLink to record
Permanent link

Direct link