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The most efficient way to run a distance event is to maintain a consistent pace over the entire race, but this is difficult for runners to accomplish unaided. The Trinity University cross country team is seeking a visual training aid that can simultaneously help multiple runners running at the same pace build muscle memory in order to maintain a constant, specified pace over a specified distance, while also allowing a bystander (coach) to see how closely the runners are maintaining that pace.
The objectives of the project are to design, build, and test a pacing system for the Trinity University Cross Country and Track teams that can maintain a constant pace between 7.5 and 12 mph for at least 1600m within the $1200 budget. This report covers the overall design and success of the final prototype.
The overall design is a pacing robot that navigates the track by following one of the lane lines. The design was split into several main subsystems: motor/chassis, line-following, user interface, main controller, and power systems. The chassis is a prefabricated RC car chassis that includes a motor and gearbox that is used in our design. Motor control uses a tachometer built from a Hall effect sensor and magnet to determine motor speed in RPM. For line-following, an array of six IR sensors is used to detect the line. The user interface is a smartphone application that communicates wirelessly with the robot to allow the user to input a desired pace and distance, as well as start and stop the robot. All of this is controlled and communicated with by an FPGA.
The majority of subsystems performed as dictated in the determined criteria, however there were complications with the implementation of line following at high speeds. The robot is able to identify the line at any pace up to 12 mph, however it was successful in following the line for paces only up to 5 mph. This was because the servo motor on the remote control car that we purchased behaved in a non-linear manner, which made it difficult to control through a standard PD loop, even after we had managed to eliminate the noise from external light and rapid changes in distance from the ground. As a possible solution to this issue, we suggest the implementation of steering control motor, whether that be a higher quality metal geared servo or stepper motor. Additionally this would likely require a large front end chassis redesign in order to incorporate it into the system. Although the system does not meet the requirements for pace, we consider this a working prototype as it can follow the line at slower speeds.
Grimes, Dupri; Guenther, Brian; McCullough, Molly; McElvogue, William; Scranton, Luc; and Studebaker, Samuel, "Pace It: Final Design Report" (2019). Engineering Senior Design Reports. 36.