This master thesis contains modeling and nonlinear automatic control of an autonomous lawn mower. The vehicle shall be able to follow a magnetic field loop buried in the lawn on an arbitrary distance, including straddling. A unicycle model of the lawn mower has been derived based on previous work. The model holds for the assumption of non slip environment. Two diff erent control strategies have been implemented and evaluated in this thesis. One is based on feedback linearization  and with the feedback gain estimated using an LQ-controller. The other strategy is based on linearization at an equilibrium point  and also with the use of an LQ-controller. The only state that can be measured is the distance to the magnetic loop. In order to estimate the other states, an observer has been implemented using the linearized in an equilibrium point  model and a Kalman filter. The navigation of the autonomous lawn mower is performed using a magnetic loop buried in the lawn. The non-linearity of the magnetic field causes diffi culties when estimating the distance to the loop. One magnetic field strength corresponds to two distances to the magnetic loop. The nature of the magnetic field and the measurement noise causes the precision of the controller to be limited. The conclusion of this master thesis is that it is possible to navigate and follow the magnetic loop at a distance greater than 0.3 [m], but with overshoots during sharp turns. If the reference distance is smaller than that, the behavior of the robot will be oscillating when following the loop. The limitations of the controller performance is due to the lack of information which can be extracted from the measurements of the magnetic field.

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2 pp. / Describes how to select the appropriate lawn mower to properly mow the species of grass at the correct height for high, medium, or low maintenance levels.

SammanfattningExamensarbetet har syftat till att undersöka möjligheten att utrusta Husqvarnas autonomagräsklippare med avståndssensorer. Dessa ska hindra gräsklipparen från att kollidera med hinder i sinomgivning. Gräsklipparen arbetar i en miljö där väder, temperatur, ljusförhållanden och underlagvarierar kraftigt. Detta innebär att kravet på sensorerna är högt.Av de sensorer som undersökts har det visat sig att ultraljud och ”structured light” är de system sombäst skulle kunna uppfylla all dessa krav till ett rimligt pris.I examensarbetet undersöks därför ultraljudssensorer från företaget Maxbotix närmare ochimplementeras i en prototyp. Fyra stycken sensorer placeras på gräsklipparens kaross. Dessakommunicera med en mikrokontroller som i sin tur förmedlar mätdata till en dator. På datorn körsen sökalgoritm som tolkar och sammanfogar sensorernas mätdata.Efter ett antal tester visar det sig att de sensorer som valts inte uppfyller de krav som ställts. Dockbör den metod och algoritm som används kunna uppfylla kraven om en annan typ av sensor används. / AbstractThis master thesis is aiming to investigate the possibility of adding distance sensors to Husqvarna’sautonomic lawnmower. The goal is to prevent the lawnmower from colliding with obstacles in itssurroundings. The environment where the lawnmower is working is very dynamic in sense ofweather, temperature, ambient lightning and terrain. This gives high requirements on the sensors.Of all the sensors that were examined, ultrasonic and structured lightning came out as the ones bestfit to fill these requirements to a reasonable cost.In this thesis ultrasonic sensors from Maxbotix were implemented on a prototype. Four sensors wereplaced on the lawnmower body and connected to a microcontroller. The microcontroller then passesalong the sensor data to a computer that is running a search algorithm. The algorithm is used tointerpret the data and merge the different measurements.After certain amount of testing it was shown that the chosen sensor did not meet all therequirements. However the method and the chosen algorithm should suffice with another type ofsensor.

Husqvarna AB is one of the leading producers of outdoor products such as autonomous lawn mowers. One important feature of these products is the ability toquickly respond to environmental factors such as slippy areas. A reliable slip detector is needed for this mission and many different technologies exists for detectingslip events. A common technique is to check the wheel motor current, which clearlydeviates when the lawn mower is subjected to slipping. The on-board sensors opensup for an alternative solution which utilizes the loop sensors as the main slip detector. This thesis covers the construction of a slip detection prototype which is basedon the loop sensors. In the end, Husqvarna AB was provided with a new alternativesolution, which was successfully compared to the exiting solution. It proved to bea reliable slip detector for manually induced slipping indoors, outdoor performancewere not investigated. Ultimately, the implemented prototype outperformed the existing solution in the intended environment of indoor testing.

The objective of this study was to evaluate the practical limits of EPA's NONROAD 2005 to accurately simulate Central Florida conditions, especially with regard to lawn and garden equipment. In particular we investigated a NONROAD emission inventory using default inputs and then created a locally specific emission inventory. These emission inventories were prepared for Orange, Osceola, and Seminole county and focused only on the VOC and NOx emissions caused by lawn and garden equipment. The model was manipulated to assess its ability to represent this specific category of nonroad equipment for a given airshed first by running a base case scenario using default data and then by developing a locally-specific scenario through administration of a survey. The primary purpose of the survey was to evaluate local values for equipment population, equipment characteristics, activity estimates, and other relevant information. To develop these local input estimates, data were collected concerning population and usage statistics in the Central Florida area and were combined with emission factors, load factors, allocation factors, and other needed values that have been previously established by the U.S. EPA. The results of the NONROAD model were compared with the resulting emission estimates calculated from locally derived inputs, and as a result of the analysis an accurate emission estimate was calculated. In addition, several possible air quality action steps were further assessed according to feasibility, cost, and predicted emission benefit. These potential management projects were further investigated by assessing the success of other similar projects in other cities in an effort to establish specific costs and emission benefits as they relate to the tri-county area.

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This master's thesis project investigates the impact of hydrophobicity and topology on dry and wet macroscopic particle accumulation on surfaces. The report begins by outlining the challenges associated with this phenomenon and the existing theories and methods used to study it, including adhesion, surface engineering, the Lotus effect, and humidity. The method chapter presents the case study of grass accumulation for robotic lawn mowing application and describes experiments conducted to simulate the accumulation of grass during robotic lawn mowing. These experiments explore two different phenomena: the accumulation of grass that is already stuck to a surface and the process by which grass initially sticks to a surface. Experiments have been done to change the hydrophobicity level of certain specimens and investigate how hydrophobicity and humidity affect the stickiness of grass when already accumulated on a surface. In addition, experiments are conducted by throwing grass towards surfaces with different hydrophobicity and topology to determine the influence of these variables on accumulation. Finally, a physical field test is conducted. The findings indicate that hydrophobicity up to 108,2° water contact angle has a low impact on both static and dynamic grass accumulation. Increased hydrophobicity does not tend to decrease grass accumulation, even showing increased accumulation in some experiments. Humidity and the wetness of the grass are more important factors. Experiments have shown that a textured surface can decrease the accumulation, showing significant results in a controlled environment. However, these results did not transfer over in a significant way to a real robotic lawn mowing situation.