niallcaldwell

Hi there

I am trying to retrofit a full-size car with a drive-by-wire throttle system for a research project (Suzuki Grand Vitara 2.0 petrol)

I am considering the option of using a hobby servo and wondered if anyone out there can give me some advice.

I have looked at fitting a production electronic throttle as made by SiemensVDO and Bosch for VW cars. But these rely on the ECU to close the throttle position loop which complicates my system.

The alternative is to drive the existing throttle butterfly with a digital hobby servo which would be easier from a control point of view because the position loop is taken care of. I think I need about 1Nm = 130 oz-in (if I remove the return spring) and I want to achieve <100ms response.

some questions I would really appreciate some answers to:

1. what accuracy could I expect in terms of bits of resolution? I guess I need 9 or 10 bits.
2. do digital servos have an integral term in their feedback loop to take care of steady-state error? if not what is the typical proportional gain in terms of degrees of error or pulse width for full torque?
3. my local hobby shop has a Futaba 9451 in stock. Is this a good example of state-of-the-art in terms of deadband, accuracy and speed? (I realise some other makers offer PC tuning)
4. my plan would be to replace the servo internal feedback pot signal with the the throttle position sensor pot signal. Is this a common and sensible mod?

Thanks a lot in advance for any help!

Niall Caldwell