“CWRU Cutter,” Case Western’s team for the ION “RoboMow” autonomous lawnmower competition, competed in its fifth season from May 31 – June 2, 2012, in Dayton, OH, placing third in the advanced category. Replacing Andrew Smith as the team’s lead mechanical engineer, I was responsible for hardware development on the mower. In addition to designing and fabricating a new modular chassis, I also supervised development of the robot’s refined bump sensor. Originally I was to be involved with some controls programming, but due to time considerations and other commitments, I had to relinquish these responsibilities back to the software lead. CWRU Cutter Cinco is built around a commercial-off-the-shelf electric mower deck with a 19-inch blade driven by a 24V permanent magnet DC motor. Though it requires a larger battery bank than a gas-powered mower deck would, the electric deck provides many other benefits, including reduced vibration and noise, the elimination of a fuel system, and integral blade monitoring capabilities.
The CWRU Cutter Cinco includes a standalone drive hardware unit – my primary contribution for the 2012 season – which is intended to provide a semi-permanent, highly-modular platform for future development. It consists of the battery rack, motor mounts, integral hard mounts for sensors, and a “standardized” bolt-on mounting pattern for the main robot chassis. This modularity drastically improves the serviceability, upgradability, and flexibility of the CWRU Cutter Cinco. The balance point of the drive platform is just below and forward of the drive axles, providing a highly-stable platform with very little tendency to roll during braking or acceleration.
Mounted on the side of the CWRU Cutter Cinco is a string trimmer, which allows the unit to edge more effectively, increasing the final quality of cut. The COTS trimmer head is hard-mounted to the adjustable-height deck to provide a consistent cut height. The CWRU Cutter Cinco’s drive motors, sourced from electric wheelchair manufacturer Invacare, allow the robot to negotiate severe terrain grades and navigate safely over ruts and other obstacles without significantly decreasing speed, even in heavy grass conditions. The robot’s drive wheels have a wide, aggressive dirt tread to facilitate movement over difficult terrain.