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Pulse Circuit for Electronic Power Steering

Discussion in 'General Electronics Discussion' started by thinmint, Nov 13, 2012.

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  1. thinmint


    Nov 13, 2012
    Hello everyone!

    I am a high school student in need of an idea for a circuit.
    In my spare time, I have been building an electric car out of a 2003 Honda S2000. Two DC motors, a 27kwh battery pack, 2000 amp / 345v controller. Needless to say, it will be fun!

    One of the coolest features (to me) of the car is its use of a stand alone electronic rack & pinion steering assembly. Most cars have pumps that run off of belts, entirely to power its non-electronic steering.

    Before I tore the car apart, you could put the key into the ignition, push the start button, and you would instantly have power steering. In the S2000, the amount of power steering supplied is inversly proportional to the RPM of the car. At as RPM increases, you get less power steering. I also believe that it monitors the speed of the car, so power steering is reduced once you exceed a certain speed.

    Heres my dilema!
    Because my electric motor will not idle at 800-1000 RPM, I need a circuit that turns on when the car is turned on and generates a signal until the RPM of my motors exceeds a set number.
    For example, turn the car on, car believes it is idling at 800 RPM. Drive around, once you hit 15mph or so, the rpm of the motors will be at 1000, at which point the circuit will quit generating a signal and supply the car's ecu with the actual RPM of the motors.

    I need help making the circuit!
    I have an +12v RPM signal that will be generated via an inductive sensor on the DC motor. This signal will then go to the circuit which will output a +12v signal to the ECU. I would like the circuit to be as adjustable as possible, like changing the RPM threshold that my motors must pass.

    Some helpful information:
    The stock rpm sensor on the gas engine was 4 pulse / revolution.
    Therefore, 800 rpm = 13.3 revolutions per minute. 4 pulses / revolution = 53.33 hz

    Any help would be appretiated! Can't wait to finish the car up
  2. CocaCola


    Apr 7, 2012
    You are probably looking at a micro solution, connected between the motor and the power steering, one that monitors the motors RPM and outputs the fake 800 RPM signal until it detects a faster signal that it then passes to the steering...

    But, there has to be more to the system then this as you suggest, because 1500 RPM in first gear is entirely different then 1500 RPM in 3rd gear... There has to be some addition compensation done to the signal and thus a 'corrected' RPM sent to the steering, or possibly the steering system does this compensation based on another sensor?

    I know this may sound like a paraphrase of what you said but once you determine what needs to be output to the steering system you can then write the code for the micro that will spit out that code based on multiple inputs, aka motors real RPM and speed/or gear...
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