Project e-smart, part 1: Students convert Smart car into an EV

Nowadays, energy economy is one of the most important topics in all areas of technical research, especially in the automotive sector. Dwindling oil supplies and fossil fuels rising prices force automobile manufactures to develop less energy consuming vehicles. Furthermore, proceeding urbanization and a changing in young people's user behavior require new mobility concepts. Concepts such as car sharing, the smart grid, and advanced driver assistance systems or the interactive vehicle are being advanced. Independent of which trends will prevail, it is obvious that future mobility will become increasingly manifold, complex, and electric.

All this will bear huge challenges to automotive design engineers. Future vehicle complexity will demand for high interdisciplinary and enhanced teamwork in all stages of product development. To master these challenges university education plays a major role to teach relevant skills.

This report presents a student project at the Institute for Internal Combustion Engines and Automotive Engineering (IVK) at the University of Stuttgart in which a commercial compact car with combustion engine was converted to an electric vehicle. The whole process of conversion including planning and specifying the requirements onto to electric vehicle, electric components selection, E/E-architecture design, control software design as well as implementation of hardware and software was done by students of the University of Stuttgart under the supervision of the Research Institute of Automotive Engineering and Vehicle Engines Stuttgart (FKFS) which is in tight cooperation with the IVK.

E-mobility at the FKFS/IVK

The automotive mechatronics departments of the cooperating FKFS and IVK are concerned with the issues of e-mobility. In several government-funded and industry projects diverse research is carried out using a holistic approach to generate fast and sustainable solutions. The FKFS/IVK offers and uses several facilities for e-mobility research topics such as a fleet of different category electric vehicles equipped with measurement systems for power flow and vehicle dynamics, a test bench for electric and hybrid power trains as well as batteries and cells, a driving simulator for development of advanced driver assistance systems, and a research charging station capable of different kind of AC, DC, and inductive charging.

Project goals

This university funded project allows students of the University of Stuttgart to convert a commercial compact car vehicle with combustion engine to an electric vehicle. About 20 students with different subject background from mechanical engineering, automotive and motor engineering, electrical engineering, automation engineering, and cybernetics started planning the vehicle conversion at the end of 2010. It was aimed to bring students with different knowledge and skills together in order to handle the conversion process complexity. This was necessary since tasks were various. Students specialized in mechanics were required as well as those knowing about electronics and software. All students' works were supervised by postgraduate employees of the FKFS.

First of all, requirements onto the electric vehicle had to be specified. The main target was to create an open vehicle platform enabling for manifold research topics, especially for the three core research areas: Range prediction and optimization by means of intelligent power train control and advanced driver assistance systems; different charging techniques as fast DC charging and comfortable inductive charging besides the common AC charging standards as well as safety which is considered by a high voltage system monitoring; battery cells monitoring; and copious diagnosis functions.

Regarding the set requirements, it was soon clear that the converted vehicle had to be fully controllable by self-made software in all stages of driving and charging operation as well as booting up and shut down. Based on the considered control functions the students started to specify required measured variables, the related sensors, the rapid control prototyping systems, the control and communication interfaces to the power train, and the on-board and off-board chargers. All necessary hardware components were determined and the E/E-architecture including communication lines and power lines designed. Meanwhile control software was developed, tested in a simulation environment, and implemented on the rapid control prototyping hardware.

Finally, the converted vehicle was ready for a first drive with electric propulsion in August 2011. In the meantime, the software was refined and new functions were implemented. Also, the vehicle could show its operational capability when it was driven by about 50 test drivers on a 60 km driving cycle in the course of a huge FKFS test driver study with wintry conditions on the subject of energy consumption in real-life vehicle operation.

In the future, further sensors and functions will be implemented by new employed students in order to achieve the set targets. The new functions have to tested and evaluated by the students using simulation but also in experiments on public roads.

To read the complete article, which details the Smart ForTwo vehicle conversion, click here, courtesy of EE Times Europe Automotive.

Part 2 of this article describes in detail the vehicle control system; measurements, modeling and simulation of the vehicle; and an outlook on future e-car issues.