One of the big problems about encouraging students into engineering is the perception that it is dull and boring. This has led to a dramatic fall off in the number who want to take it up as a profession. One of the solutions, says a recent report developed by Ricardo and Skills4Auto called “Vision for the UK Automotive Industry in 2020,” is making engineering and manufacturing interesting and sought-after careers built around the demands of new technologies.
London’s Imperial College has set out to address these issues with its EnVision 2010 project. This is a new initiative that is designed to develop and train engineers of the future in leading-edge environmentally responsible technologies, and to inspire new generations to pursue an exciting and inspiring career in engineering. As part of this program, the Faculty of Engineering has established Imperial Racing Green, a flagship initiative that is the test-bed for the most cutting-edge advances in technology being developed at Imperial. With up to 60 undergraduate students each year working in partnership with business and design students, the aim is to accelerate the trickle-down effect of new technologies from motorsport and universities to the automotive industry.
One such project is the development of an electric-hybrid fuel cell vehicle. In its development, undergraduates have undertaken new research in areas such as designing supervisory and component control systems to manage the complex power flow between the fuel cell, supercapacitors, batteries and motors, and the development of software tools to simulate and optimize integrated systems, such as the mechanical and regenerative braking systems. They are also investigating green polymer composites to make the chassis, and developing a drive/brake system using highly efficient brushless permanent-magnet motor/generators both to power it and to provide regenerative braking. They are also looking at testing and optimizing the hydrogen fuel cell system.
Now into its second year, they have built their first vehicle, a beautifully crafted go-kart that made its first public appearance at the Formula Student, the British equivalent of Formula SAE, in mid-July. Despite being well presented, it is very much in its early prototype stages, weighing around 50 lb more than a conventional kart. “We are still playing around with the packaging. The active control of the power and the braking is going to be crucial to maintaining the kart’s stability,” says Dr. Offer, project manager of Imperial College’s Imperial Racing Green. “It’s going to be an electronic development as well as a chassis one, but at the moment we will be going down the traditional route of designing a spaceframe chassis and basing our electronics around that. We’ll try and stay as conventional as possible. However, we are not looking at steer-by-wire although we currently employ drive-by-wire. The throttle cable has been replaced by a potentiometer so by its very nature it has to be drive-by-wire.”
The heart of the kart is a 1.2-kW Ballard fuel cell supplying the charge to a lithium polymer battery with a very high discharge capacity of up to 1,000 amps which, with the 48-volt system, gives 48 kW on tap. The two motors on the vehicle are rated at a nominal 9 kW each for continuous operation, but they can be overloaded for up to a minute by 300% or 400% providing 27 kW per motor. Offering 50 Nm at a 10-minute rating but able to go up to 90 Nm, the three-to-one gear ratio sees each motor develop 270 Nm for up to 10 minutes. In effect, this means that the kart can accelerate for 10 minutes with 540 Nm of torque at its disposal. “You can really see the potential of the electric motors in getting you off the line,” says Dr. Offer. “The car is fitted with a small hydrogen cylinder that allows it to run for 15 minutes but doubles up quite easily for endurance events, depending on the speed.”
Safety has been very much to the fore in the design of the vehicle, Dr. Offer explains: “We have been very conscious of the safety systems and have multiple redundancy and trip systems so that in the event of any malfunction, the kart will automatically shut down but we also have a manual shutdown if all else fails.”
The brake system is a combined hydraulic-electric system—when the throttle pedal is lifted it automatically goes into regenerative braking mode meaning that there is effectively an engine drag. Hydraulic brakes can then be applied traditionally with the brake pedal. “Optimizing this system is crucial to maximizing recoverable energy,” says Dr. Offer.
The brain of the car is a CompactRIO real-time embedded controller from National Instruments, the same as is used on many Formula SAE/Student cars, that is initially being used for data acquisition. “However, we have many projects running in the electrical engineering department at Imperial to develop modules in LabVIEW for many different areas including active differentials, torque steer and regenerative braking control,” says Dr. Offer. “We are currently using axial flux motors with thermo-magnets in them and 4QD controllers for regenerative braking.”
“The plan for the next couple of years is to develop this kart into a Formula Student Design competition entry next year. To do that we are going to have to work with the chief judges and the organizers to develop the regulations and see how we can integrate electrical machinery into the current Formula SAE/Student car set up. We intend to have an electric hybrid fuel cell car-powered car ready for the competition in 2009 that will feature in-wheel traction, incorporating the motors into the uprights and having contained units in the wheels. This will eliminate the problems associated with chain drives.”
Dr. Offer expects there to be a spin-off to motorsport and road vehicle technologies particularly with the in-wheel traction and with the algorithms that are being developed for vehicle control. “Learning how to deal with electric drive systems is very important for the future for the motor industry, as well giving the students something refreshingly different that is both exciting and motivating.”