A master thesis from Aalborg University
Removal of Audible Resonance from Turf Tank Line Marking Robot & Design of All-Wheel Drive Robotic Lawn Mower
[Fjernelse af hørbar resonans fra Turf Tank linjemarkeringsrobot og design af firehjulstrukket robotplæneklipper]
Author(s)
Term
4. term
Education
Publication year
2025
Submitted on
2025-05-28
Pages
128 pages
Abstract
The project is written in collaboration with Turf Tank, which is a company specialising in line marking robots. They are looking to branch out into industrial-grade robotic lawn mowers. Turf tanks current in development mower is large and designed for cutting large open areas quickly. It is not designed for very rough terrain, such as sometimes found in the semi-rough or rough on a golf course, or for tighter areas in between trees and the like. Therefore, a smaller all-terrain mower is developed in this project, which aims to fulfil tasks which the large mower is not designed to handle. However, their line marking robot has certain issues, which sometimes cause significant audible noise or terrain damage. These problems are to be solved first, so the issues are not transferred over to Turf Tanks in development lawn mower or the prototype to be designed in this project. The audible noise problem is investigated and found to come from resonance in the chassis excited by the motor control. Due to costs, it is not desired to alter the mechanical system, so a software solution is wanted. Several things are implemented, the velocity estimate is improved, the control is tuned for a first-order response where possible, and filtering is applied to the velocity estimate to filter out the resonant frequencies. Removal of the audible noise is successful, and the controller bandwidth is increased in the process. The line marking robot's performance is marginally improved. The terrain damage is found to stem from wheel slip, and as such this is to be avoided in the design of the mower. The learnings from the line marking robot are carried over to Turf Tank's mower design and the prototype in this project, ensuring they will not have the same issues. The small mower focuses on off-road capabilities and maintaining good cutting quality. For this all wheel drive and suspension is added. An articulated steering configuration is chosen which enables zero turning and low mechanical complexity. To be able to control this, a model of the system is created, and non-linear state-dependent control is developed afterwards. Furthermore, a suspension model is created to determine the performance effects of adding suspension, and eventually for tuning the suspension for the mower. Ultimately, the mower is tested at Aalborg golf course. Here, satisfactory cutting quality is achieved. The mower fulfils the majority of the requirements set. Several things have been learned from the mower concept developed in this project, which can be utilised in further development as described in the future work chapter.
Documents
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