Sensing and Control Electronics for a Benchtop Hybrid Powertrain

Abstract

Concept retention between courses is a recurring problem for engineering educators -one that is exacerbated by the disjointed nature of the engineering curriculum. One possible solution to the problem, a multi-year design/build/test project, is currently being studied by the authors. The project, a bench-scale hybrid powertrain, is completed by our students over the course of five semesters. The focus of this paper is the set of electronic circuitry needed to sense and control the powertrain. This is the latest installment in a series of papers discussing the project; see [2][3][4][5][6] for a fuller description.The "prime mover" in the benchtop hybrid is a small engine powered by compressed air, which is designed and fabricated by students during their Junior year. The goal of the powertrain is to convert the maximum amount of energy stored in the compressed air to motion at the output shaft of the powertrain. In order to accomplish this, the students need a means of sensing the speeds of each of the shafts in the powertrain, as well as monitoring the amount of compressed air being sent to the engine and the electrical power sent to/from the battery pack. In addition, the instructor needs to measure compressed air use and to provide a controlled load at the output of the powertrain. Some parts of the sensing/control circuitry (e.g. the tachometer) are built by the students, while other parts are fabricated by the faculty as part of the set of benchtop "workstations" used by the students. This paper will present and discuss each of the electronic circuits in the sensing/control/loading system. The circuits described in the paper (e.g. tachometer, motor driver, electrical load) have wide application in automotive engineering and robotics, and it is hoped that by presenting a thorough description of each circuit, instructors at other institutions can benefit from our successes and failures and adopt individual modules from the hybrid powertrain into their own laboratory instruction. IntroductionOne of the most exciting innovations in automotive technology is the development and realization of the hybrid-electric powertrain. The most commercially successful hybrid vehicle has been the Toyota Prius [1]. Students at Rowan University design and fabricate a bench-scale version of the Toyota Hybrid System over the course of five semesters, as a way of integrating the mechanical engineering curriculum. Parts of this project have been described in earlier papers [2], [3], [4], [5] and only a short background will be given here. A wealth of information about the project is available on the author's website www.benchtophybrid.com.