Help Needed for building an electric (HIP) car from scratch

Hello All:

This may sound very stupid, but I am posting it here anyways:

We six engineers (three EEs and 3 MEs) form an university X (let's keep it secret for now) have decided to make Formula Hybrid Vehicle to participate in the FH 2010 competition. The professor at the beginning seemed very enthusiastic , but is not helping us at all. We are left to work ourselves and figure out everything. So, we have decided that we will make the simplest possible electric vehicle and we are not participating in the 2010 contest. But the car that we will build will comply the rules of SAE.

The problem that we are facing in building the car is decomposing the whole project. The mechanicals have said they will build the chassis, the steering, and the brake. We decided that we will build the electronic throttle control. We will build this system like the following:

Accelerator -> pressure sensor -> micro controller ->PWM output -> power regulator -> Motor

Another input to the power regulator will come from battery.

My question is about the transmission. Will we need any gear for this car? The throttle system will control the flow of required current and voltage in the motor.

I will remain forever grateful if someone just gives me an overall idea of building a simplest possible formula sae electric car. All the books that i have found so far talks about conversion. But we are building from scratch.

People can say that we should buy a controller instead of designing it. But this is our senior year design project and our professor has said whatever we do, our project must have substantial amount of software part and hardware part. That's why we are not buying any controller.

The answer to your question is : Maybe

What motor are you using?
Is it PMDC, BLDC, induction, PMSM, series wound, SepEx?
What is its rated speed? What is its maximum speed?
What is its rated torque and maximum torque?
How fast do you want to go? How fast do you want to accelerate?
Are you building the car for competition in FH or Formula Student Electric or is it just an experiment?
Are you planning to eventually build a hybrid? If yes, what configuration are you planning on using for your drivetrain?

Without the answers to these questions you cannot decide if you need a transmission or not. And the answers to the above questions can only be found in the goals that you set and the analysis and engineering compromises that you have to do.
The simplest electric car that you can build is one with a PMDC as your drive motor, coupled with a chain to your rear differential/axle with proper gear reduction to achieve your max speed at the rated speed of your motor. It will use a simple one quadrant chopper drive as an interface between your motor and your lead acid batteries.

Yes, we are building a simple electric car, and at the moment we are not worrying about future conversion to hybrid configuration. And I have decided that I will use a brushless permanent magnet DC motor and lead acid batteries. About the maximum speed and rpm and the rated torque of the motor, I am doing some simulation activities from the book "Electric Vehicle technology explained by James Larmine". That book has some good Matlab programs, depending on the input parameters to those programs, it gives me different acceleration and range performances. Now, I don't know what is the minimal acceleration and range performance required to enter the SAE competition. If you can give me some idea on it, I think I can finally decide on the motor and the batteries. The information that the rule book gives is "The car should be able to complete 75 meters in less than 10 seconds".

The drivetrain will be very simple. There will be no clutch and it will have a fixed gearing. The electric motor, the fixed gearing and the differential will be integrated into a single assembly and the whole drive train will be very simple.

Now, the EEs are also give the responsibility to take care of the throttle. Regarding it, we are planning to build the following system:

Pedal -> Throttle Position Sensor -> Micro-controller -> PWM signals

This PWM signals will be fed into the motor controller. The professor told us to figure out assembling the pedal and TPS such a way that it generates an analog signal for the micro-controller. I have read a lot about TPS but not so sure about the pedal. Do you know any websites that sell pedal? Or any idea how to configure this?

I have been a straight A student. But now I find that I am a plain stupid when it comes to design. I sometimes feel that my engineering education has been a major fail. Any help will be greatly appreciated.

The rules clearly state the range that the cars need to cover. Read the rules again.
If you are in a project this big I am going to assume that you have taken basic mechanics/physics. Use your knowledge to figure out the minimum average acceleration required for your car to cover

	Quote:
	75 meters in less than 10 seconds

. If you know that then you can figure out what your torque and power requirements are from your motor.

A TPS is a potentiometer, your EEs should be able to get an analog signal out of it. Get a TPS and see how it works and then figure out a way to adjust its motion to the motion of a pedal, it should be a simple enough design exercise.

There are lots of off the shelf analog throttle position sensors that work very well. Many motor controllers output a 5v reference single and take a 0-5v TPS signal, and that is very common among TPS sensors. antoant has a great point: there is a lot of information in the rules regarding the requirements for your car and how it will be scored. Do a good analysis and quantify as many things as you can, and there are even old scores up that will allow you to predict how many points your car will score once you predict it's performance.

_________________
2009 Crew Chief-Texas A&M Formula Hybrid

To answer your original question, if you want to run an internal combustion engine at a single, most efficient speed, to power a generator, you will not need a transmission. There may be a gearing change between the final output of the ICE and the generator, but adding a transmission will just add additional weight.

I'm still curious why anybody would decide to make a HIP?

To answer your question Ram, for the same reason that a lot of schools that do FSAE don't manage to take a car to the competition or if they do take a car they might not be able to compete or finish all the events. They don't have enough time, or resources to finish a car in the allotted time or their full designs are to complex for the time they have. A HIP gives a team the opportunity to develop a simpler car and still get to competition and compete and thus learn how the competition works and how they can improve on their current design. It is less time consuming, less expensive, and less complicated if you take the engine out of the equation. Plus it provides new teams with a backup plan in case they don't manage to get their engine subsytem working, which might be harder to do than their electrical subsystem. I have seen a few teams fall back to this easy plan B, including mine during the first year of the competition when we did not know what we were getting into.

I just re-read and realized they were building the whole thing from the ground up. That's going to be tough. Still, with registration being doubled this year Rolling Eyes

I'm not sure I'd want to put a hell of a lot of effort into something that wouldn't really be all that competitive.

That being said I'm not sure other schools have the same budget problems we do.

To the original poster: good luck to you. A FH car from the ground up with 6 guys is going to be an enormous challenge. Hope to see you guys in May!

I wouldn't be suprised if an HiP wins this year. The amount of energy you can efficiently extract from 16 kWh of battery is more than 20 kWh of gasoline per the competition rules. Along with the weight savings of not having an ICE + transmission + generator + more stuff to break.

HiP run in their own class so they cannot "win" the competition as the main class is the hybrid class.

[quote="bishonnomahmud"]

The drivetrain will be very simple. There will be no clutch and it will have a fixed gearing. The electric motor, the fixed gearing and the differential will be integrated into a single assembly and the whole drive train will be very simple.

Now, the EEs are also give the responsibility to take care of the throttle. Regarding it, we are planning to build the following system:

Pedal -> Throttle Position Sensor -> Micro-controller -> PWM signals

This PWM signals will be fed into the motor controller. The professor told us to figure out assembling the pedal and TPS such a way that it generates an analog signal for the micro-controller. I have read a lot about TPS but not so sure about the pedal. Do you know any websites that sell pedal? Or any idea how to configure this?

I have been a straight A student. But now I find that I am a plain stupid when it comes to design. I sometimes feel that my engineering education has been a major fail. Any help will be greatly appreciated.[/quote]

was the motor controller what the EEs were building? Have you decided on a microcontoller yet? or a pedal ?

I guess what i should ask is this:
Do you guys have figured out exactly what your designing and what you're buying?

Our hybrid team has 2 EEs and 4 MEs, basically we buy everything we can (controller, pedal, fuses, relays, contactor, lock out switch, motor, generator, ICE). The project is nonetheless a Nightmare (but it's not quite the power/toughness of all the swamps we control).

It's kind of ironic because our professors gave us the same sentiments about software & hardware design in the beginning but they apparently knew the car was going to be difficult for 6 clowns to build so they just forgot about that and let us go to work.

I'll share some of my experience about building a FH race car.

for 2008,
we started building our first car. Due to lack of FSAE experience, we did build the car ground up.
The spec was 220VAC 15kW PMAC with 250c.c. ICE.
We bought our controller, but we still have a lot of software and hardware design involved.
We made electric power-steering, electric rear-wheel steering, electric toe control, electronic hydrostatic transmission and throtle by wire. So there's a lot of software programming on DSP.
Our vehicle was not completed in time for the competition, but we did take our control system to TI's DSP design competition and got 3rd in Asia region.
We used servo (from RC car) to actuate the throttle body. And when we turn on the motor controller, first thing we see is the servo going nuts.
Big motor do generate considerable amount of interference to other stuff.

for 2009,
The 2008 vehicle was not really all that much rule complient, so we started all-over.
I found a sponsor that'll provide all the found that we need for the build.
But the condition was, we have to purchase everything thru their system. (Tax purpose I believe, so they can treat this sponsorship as a "cost")
Their system is extreamly slow, we waited for almost a month just for the 1020 tubes for our frame.
as a result, the car did not finish.
One major thing I've learned: get sponsorship in CASH or in PRODUCT, and nothing else.

for 2010,
we re-used the engine of the 2009 car and redesigned everything else.
So we pretty much start from the ground up for the third time.
My team members are 4 MEs, and I am in IE. (but I studied EE in UBC for a year)
Looks like we'll finish the car in time for race this year... (road test is scheduled within 2 weeks)
BUT (a very big BUT), I failed more then half of my credit this term. (so is another team member)
The cost to complete a race car with a small team is pretty great.

An advise for you, and anyone who wish to start with no experience:
Spend some time in the gallery, go through every photo. Learn from all the particepating teams.
They are great, and you'll learn a lot from looking at their cars.

And I do agree with Colon_McCommander, purchase everything you can to keep your cost down.
Once you have the first running car, you'll have a lot more resource and people.
A running race car do attract lots of attention.

	antoant wrote:
	HiP run in their own class so they cannot "win" the competition as the main class is the hybrid class.

The scores for the HiP cars are based on all cars times. The number one HiP Endurance car does not get 400 points, nor do they get 150 on the autocross, unless they were first among the entire competition.