Radio Controlled Robot Lawnmower

This paper presents an engineering technology senior project: radio-controlled robot lawnmower. The lawnmower can go forward and reverse. It can also turn around. The speed of the lawnmower is comparable to a push lawnmower. This project involved use of the student’s knowledge acquired from many major courses, which included Computer Assisted Drafting and Design (CADD), machine shop, strength and materials, electrical circuit analysis, electronics, electrical machines, and instrumentation and controls. Introduction At Middle Tennessee State University (MTSU), engineering technology students must take a project course in their senior year. In this course, engineering situations are solved by experimental means. Student must have experimental approach, gather data, interpret results, and prepare a formal technical written report and an oral presentation. For the electro-mechanical engineering technology students at MTSU, most of their senior projects involve both electrical/electronics work and mechanical work. In the past years, many excellent projects were completed. Some of the projects were presented at professional conferences [1] [2]. Recently, developing a remote controlled robot lawnmower was selected as an electro-mechanical senior project. In this project, a radio-controlled lawnmower was designed, built, and tested. Figure 1 is the picture of the lawnmower. Mowing lawn is less than fun for many people, especially if they have allergies or physical limitations. A ride mower requires a driver to ride on the mower. To operate a push mower, a person must walk and push behind the machine. Cutting grass is a good exercise, but not a lot of people like to do it in hot humid summer. It has been many people’s dream that they can stay in shadow or sit on a porch to operate a lawnmower. The remote controlled lawnmower developed in this project made the wish almost true. P ge 9.036.1 Proceedings of the 2004American Society for Engineering Education Annual Conference & Exposition Copyright©2004, American Society for Engineering Education Figure 1. Remote Controlled Lawnmower The Lawnmower and Its Major Components The major components of the remote controlled lawnmower include one push mower body, four wheels, two 24-volt DC scooter motors with belt drives for driving the rear wheels, one remote controller and two speed control boards, one 20” blade, one 24 –volt DC motor for driving the blade, and two batteries. The body of the remote controlled lawnmower is a 20” Murray push mower frame, which is that of currently sold retail units. The remote controlled lawnmower has four wheels, which are standard push mower wheels. Each of the two rear wheels is driven by a 24-volt DC scooter motor through a belt, as shown in Figure 2. The maximum speed of the lawnmower is 6 miles per hour, which is the standard of many self-propelled push mowers on the market and the limit for a good quality of grass cut. The two front wheels are casters, which are connected to the mower’s body through two brackets, as shown in Figure 3. The two motors, which drive the two rear wheels, control the lawnmower’s speed and direction. When these two motors run at the same speed, the lawnmower goes straightly forward or reverse, depending on the motor’s rotating direction. When the left motor spins forward slower than the right motor does, the lawnmower turns left, and vice versa. Figure 4 shows a rear wheel driving system.