On methods for assistive mobile robots

This thesis makes a contribution to the field of autonomous vehicles, especially for use on assistive wheelchairs. Methods and technologies for topological signature maps, obstacle avoidance, door passing, localization, and navigation are presented. One method is called circle sector expansion (CSE), which can be used to generate a skeleton in given two-dimensional data. The method is useful for semi-autonomous driving in an unknown environment. The output can be used for path planning and map building. The thesis also presents a way to find fingerprints, called signatures, in the environment that surrounds a vehicle. The signatures are used to build a topological graph, and to detect when the vehicle re-enters a region. The topological map is a hybrid map since the edges store metric properties and represent locations where the vehicle is able to move. A way to model a doorway for a door passing algorithm is also presented. A MATLAB toolbox, used to interface sensors directly into the MATLAB environment, is also presented in the thesis. The toolbox is a useful tool for developing and testing new algorithms. It has support for logging and replaying of data. Most of the work was done on our experimental platform; the MICA wheelchair, the Mobile Internet Connected Assistant, which is equipped with different types of sensors and an embedded PC. The wheelchair is connected to the Internet via wireless LAN. The wheelchair can be controlled, and sensor readings can be requested from the onboard mounted sensors over the Internet.Godkänd; 2006; 20070314 (evan)</p

Developement of a INS/GPS navigation loop for an UAV

This master thesis report presents the developement of an INS/GPS navigation loop written in ANSI C++ using a standard matrix library. The filter have been tested on an Unmanned Aerial Vehicle (UAV) called Brumby. Here data have been logged from the Inertial Measurement Unit (IMU) and the Global Positioning System (GPS) receiver. This data have then been postprocessed and run through the navigation filter for estimation of position, attitude and velocity of the vehicle during the flights. The error feedback to the Inertial Navigation System (INS) is done with a complement filter implemented using a kalman filter written in information form.The resulting navigation filter estimates the attitude within two degrees with 95% confidence and the position within two meter using 95% confidence.Validerat; 20101217 (root)</p

Remote CAN operations in Matlab over the Internet

This paper describes the implementation of a CAN server that acts as a CAN tool to a client. It can be used to monitor, observe and send messages to a distant CAN network over IEEE802.11b (Wave-LAN). The CAN server is controlled by one or several clients that can connect to it by TCP/IP. It is possible to send and receive CAN messages over Internet from a MATLAB environment since the client software is written in Java. The CAN server collects CAN messages and stores them into a ring buffer. The messages in the ring buffer are classified by their identifier and stored into a database. The CAN tool has been used in a demonstrative application example that consist of a remotely controlled wheelchair. In the example the wheelchair was programmed to run in a square. The positions obtained by odometric CAN messages are compared with the position from the navigation system onboard the wheelchair.Godkänd; 2004; 20060929 (ysko)</p

snowBOTs: Gyro guided steering of a teleoperated tractor during winter conditions

This article describes the steering system implemented on the tractor IceMaker I. No direct position feedback is used for the steering angle of the front wheels. Instead, the steering angle is estimated by a motion model of the vehicle using gyro and odometer information. This estimated angle is used as feedback to a regulator that controls the steering system. The operator sets the requested steering angle and the regulator controls the hydraulic steering system to maintain the requested steering angle. Within certain limits, the tractor can be expected to behave according to the motion model irrespective of the surface conditions. The tractor can be teleoperated from a remote computer through a wireless network, WLAN. To enable teleoperation, the tractor has been equipped with a computer, some sensors, and other necessary equipment. During teleoperation, the operator controls the steering angle of the front wheels and the speed of the tractor using a joystick. The steering system has been tested both during winter conditions on a low friction surface and also on dry asphalt. The results indicates good performance when teleoperating the tractor. When driving carefully it is possible to operate the tractor up to full speed (25km/h). However, the steering regulator tends to exaggerate the real steering angle during sharp turns when driving on very slippery surface.Godkänd; 2008; 20080827 (hf)CASTT - Centre for Automotive Systems Technologies and Testin

Signature graphs for effective localization

We present a novel method for the localization of an autonomous vehicle in two dimensions. Instead of focussing on properties of obstacles, we emphasize the description of free-space. We introduce the concept of signature graphs which is a compact data structure describing available free-space of an environment. It therefore also represents a map of the environment. A signature is an edge in the graph and is defined by seven parameters. An edge indicates that it is possible for the vehicle to move between two graph nodes. The signature graph is flexible and can easily be updated as new information about the environment is collected. We have with an autonomous wheelchair implemented our methods and tests them with successful results.Godkänd; 2006; 20061228 (ysko)CASTT - Centre for Automotive Systems Technologies and Testin

Circle sector expansions for on-line exploration

A novel and effective method denoted circle sector expansion (CSE) is presented that can be used to generate reduced Voronoi diagrams. It is intuitive and can be used to efficiently compute possible paths for a vehicle. The idea is to model free space instead of the features in the environment. It is easy to implement and can be used while a vehicle moves and collects new data of its surrounding. The method is directly applicable and has properties for fast computations of safety margins while at the same time having low complexity. We have successfully implemented the algorithm and its methods and performed real-life tests using an autonomous wheelchair equipped with a range scanning laser, a rate gyro, and wheel-encoders. Tests showed good results for supporting the use of CSE. The results are applicable for example to improve assistive technology for wheelchair users.Godkänd; 2006; 20061228 (ysko)CASTT - Centre for Automotive Systems Technologies and Testin

Vedkaminen år 2020 - en del av boendemiljön

The Wood Stove year 2020 - a part of the living environment This project is a collaboration between Nibe AB / Contura and SP Technical Research Institute of Sweden. Based on earlier evaluations of six different technology tracks, three tracks were selected to further evaluate: CFD modeling, active control and catalyst technology, with the long term goals of particle emission, control of maximum output and long burning time. A literature review of available sensors for O2, CO and hydrocarbons have been conducted followed by a market research, focusing on developments during the last decade and experiences from biomass combustion. Sensors were long-term tested. The lambda probe works well and is affordable, while sensors for unburnt gases still need to be further optimized for accuracy and long-term stability and also become less expensive to be of practical use. Active control has been applied to a prototype and evaluated with good results. In further work with active control, emphasis should be on safety. A CFD method for stove combustion has led to an industrial application with significant cuts in time and resources. Advanced CFD simulation has been used to examine the impact of furnace temperature on wood conversion and how wood log size can be used to counteract an accelerating power output. Simulation results show that log size has good potential to contribute to an improved combustion, but should be combined with further design of the stove. A rig for evaluation of catalyst coatings has been built and experimental results are promising. CO was in principle eliminated from the flue gas and hydrocarbon concentration were reduced down to a level equivalent to 25-70% of the original content

snowBOTS: a mobile robot on snow covered ice

We introduce snowBOTs as a generic name for robots working in snow. This paper is a study on using scan ning range measuring lasers towards an autonomous snow cleaning robot, working in an environment consisting al most entirely of snow and ice. The problem addressed here is using lasers for detecting the edges generated by "the snow meeting the road". First the laser data were filtered using his togram/median to discriminate against falling snowflakes and small objects. Then the road surface was extracted us ing the range weighted Hough/Radon transform. Finally the left and right edges of the road was detected by thresh olding. Tests have been made with a laser on top of a car driven in an automobile test range just south of the Arctic Circle. Moreover, in the campus area, the algorithms were tested in closed loop with the laser on board a robotized wheelchair.Validerad; 2007; 20070910 (hf)CASTT - Centre for Automotive Systems Technologies and Testin

An autonomous vehicle for a RobotDay

This paper describes the autonomous car that is being built for the RobotDay competition, arranged by SICK GmbH. The basic rule is to let an autonomous vehicle drive a track as fast as possible, based on any sensor technology. For this race SICK donated one S300 professional proximity sensor to each team. Our vehicle will use the circle sector expansion (CSE) method to avoid obstacles and to find its way along the track. We show initial results where the CSE method was used to guide the vehicle through a test track defined by cones and other objects.Godkänd; 2007; 20071005 (kalevi)CASTT - Centre for Automotive Systems Technologies and Testin