2024 ASEE Annual Conference & Exposition

Mechanical engineering students at ______________ University were tasked with designing and fabricating a single-axis tilt sensor to meet a detailed specification. The device was intended to be used in a system to alert an operator or automatically intervene to prevent an impending rollover condition of yard maintenance equipment such as a riding lawnmower. The project was part of a third-year instrumentation and measurement theory course and was implemented to provide the students with exposure to mechanical and electrical design, fabrication, test, and documentation techniques and methods. Students worked in teams of two or three members. The device specification provided detailed electrical, mechanical, and physical requirements for the tilt sensor. A major requirement was the limit of tilt angle that must trigger the device and the range that must not cause the device to trigger. The device must also ignore short duration tilt transients to avoid nuisance alerts. A tilt angle greater than 25° and less than 90° in either direction for a duration of 1s or longer must cause the device to trigger. A tilt angle less than 15° in either direction for any duration must be ignored by the sensor. The required sensor output for tilt profiles outside of these conditions is not defined. The sensor output is a simple ground closure connection when triggered. Otherwise, the output of the sensor should be an open circuit. The output must return to the open circuit state when the triggering tilt condition is removed. Another important requirement of the sensor is that it must fit inside a prescribed enclosure (3.1” x 2.1” x 1.2”). The enclosure is mounted to a rotating fixture for testing. The fixture is driven by a stepper motor to produce the required static and transient tilt angles. The teams must develop a detailed test procedure to document the compliance of their design with the specification. Faculty and staff developed the custom test fixture for the project. Dynamic test data was captured with a USB data acquisition unit and LabVIEW software. This paper describes the lessons learned by the students and faculty during the project. Examples of tilt sensors designed by the students are presented. The custom test hardware and software are also presented and discussed.