Autonomous Weeding Robot for Home Garden

Tay, Andrew Jun Feng (2018) Autonomous Weeding Robot for Home Garden. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

In 2016, the average amount spent per household on gardening was $407. More than 70 hours per year, per person have been spent mowing their lawns. Injuries also tend to occur when mowing the lawns. Current autonomous weed removal technologies only exist for large scale farm industry. The purpose of this project is to design an autonomous weeding robot for home garden applications. The main mechanism used in this project is the String Trimmer, which is a piece of plastic filament attached to a rotating head, trimming the grass with high angular velocities. The detection of the grass is done using capacitive sensor. A capacitive sensor was chosen for its durability and robust performance. The robot will overall be controlled using an Arduino UNO R3 microcontroller. The robot will utilize a touch sensor at the body of the robot to detect obstacles, where it will then change direction following a zig-zag pattern to cover as much ground as possible. Three DC motors will be used, two for the locomotion of the robot, and one for the string trimmer mechanism. The robot will continue moving until it detects weeds that entered the lower body of the machine, where it will then stop, and activate the string trimmer mechanism for the removal of the grass. The robot is then tested for its coverage capabilities by putting it in different shaped closed space, Triangle, Square, Parallelogram, and Hexagon. The robot performs better when placed in an environment with edges 90 degrees to each other and when the robot is placed parallel or perpendicular to the shape of the garden. The zigzag pattern covers most of the area of an angled border. To improve the coverage, more advanced algorithms have to be implemented. The robot has some flaws. The microcontroller barely hits the minimum requirement, causing some performance compromises to accommodate its lower capabilities. The rotary encoder chosen was of insufficient quality for the task, causing interference. The wheel size limits the robot to operate on smoother surfaces, as operating on rough terrain cause it to get stuck and change its angle. The cutting height of the robot is also fixed. An adjustable cutting height may be desired.