Pedal and sensor assembly

[bishonnomahmud]

Hello Guys.

I am an Electrical Engineering student who is a member of FSAE team of Texas A&M University Qatar. We are building an electric car and I have been given the responsibility to build the throttle of car and take care of the motor and battery. I am planning to design the throttle system like this:

Acceleration pedal -> sensor -> Micro-controller -> PWM signals -> Motor Controller

It will be an electronic throttle control. This is the first year we took this initiative and to be honest we are not so hopeful about building a car, but the professor has said that we will have to build at least a sub-system that properly functions to be able to graduate.

As for the electronic throttle control, I am not getting the full picture. A computer engineering professor who is supervising me, told me to buy a pedal and then a sensor that can send an analog signal to the micro-controller. This is where the problem begins. I find many pedals and sensors in the internet, but how do I know if two randomly chosen pedal and sensor will be compatible and could be connected together? Plus how can I feed the analog signal generated by the sensor into the micro-controller?

I might sound very stupid but I am not trolling here. I immensely appreciate any help.

[Mikey Antonakakis]

I don't know that much about computers, but I do know that you can't use throttle-by-wire for FSAE.

Edit:
oops, missed where it said "electric" in the first post, sorry

[bishonnomahmud]

For 2010 competition, electronic throttle is allowed.

[Tilman]

For the 2010 Formula Student Germany ELECTRIC competition electronic throttle control is allowed... (and I do not know how to throttle an electric motor by limiting the mass of air it can suck in)

[jd74914]

Look into some OEM pedal assemblies. For example, newer Subaru's (among dozens of other manufacturers) have throttle by wire. I believe they use a potentiometer connected to the throttle pedal (much like a TPS for a throttle body). The varying resistance is then read and calibrated to a petal position. You will most likely have to fabricate some linkage or other means of connecting the pot to the pedal, there probably isn't much out there in an FSAE-sized package. You'll have to do that development.

For feeding the signal look at what is done with a TPS. There are 3 wires, one is supply voltage, the other return (which is affected by resistance) and the third is a reference (I'm not quite sure about this, but that is how many industrial sensors work).

You'll also have to put in some safeties in case the sensor fails, you don't want it to fail and the computer to think you have the pedal pushed all of the way down.

[Drew Price]

You might try to see if you can get info on Solar Car team's construction. I think our Solar Car team used a similar system setup that you used, and I think they got pedal potentiometer and motor controller (and even the motor) from a company who supplies parts specifically for hobby level electric cars.

The didn't do much design for it, they just bought the bits and gave it like 380 VDC, and it sorta worked alright..... kind.... I guess....

Electric or hybrid car builder's forums would be your friend at this point, I'm afraid that's about the limit of help you'll be able to get here. Unless you can get hold of some Formula Hybrid designers - like at T A&M in Texas, Dartmouth, Cal Poly SLO, etc.

Best,
Drew

[Falcon™]

Well the use of potentiometer or any other displacement sensor to detect how far the pedal has been pushed should work....as far as the throttle control is concerned in case of a normal engine i had noticed the use of a stepper motor to control a flap covering the air intake somewhere...but i guess this wont be helpful in case of the electric engine(for smaller motors pwm is used to control speed maybe u can implement this on larger scale :P )...

[TMichaels]

Think about using a sensor similar to this: http://www.parker.com/literatu...s/RS70_datasheet.pdf (http://www.parker.com/literature/Electronic%20Controls%20Division/Literature%20files/RS70_datasheet.pdf)

You get redundancy for free which is strongly recommended for electronic throttle systems and and the sensor may be easily connected to an existing pedal assembly. Use both signals of the sensor and check that the signals are close to each other to avoid a self-driving vehicle.

Regards,

Tobias

[bishonnomahmud]

Thanks to all for those who have replied http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Rellis]

When I was on solar car I found a POT with a really long shaft and used it for the pivot just glued the pedal over the shaft and added a return spring