Re: Quite worked out
dreamproject said:
hi,
thanks to every one for their input . I am planning to use a joystick to control the steering. Since I have geared the motor (7 kg-cm) with a 2:1 reduction ratio, I should get about double the torque . The motor (with gears) connects directly to the steering column . With a centre to centre distance of about 3 cm (steering column centre to motor shaft centre) , i should be able to get atleast 2 - 3 kg force , which is more that what a 640 kg hatch-back with power steering would require. :wink: (hopefully). With built-in self locking (reduction gears) , I do not think the steering would turn by itself based on road variations . I have damped the input (pot in the joystick) sufficiently to compensate for hunting.
I thought the original question was how to make it faster?, yet you've now slowed it down by a factor of two?.
Presumably this is to give enough torque to move the wheel?, at the expense of speed of movement.
However, I'm somewhat dubious about the amount of torque this will give, it might give enough to move the wheel under minimum load conditions, but I suspect it will fail under some actual load conditions - you need a far higher safety margin than 'just enough'.
You have never stated that you have any kind of feedback arrangement?, so there's nothing to keep the wheel where it is, and it's VERY likely to turn itself under varying road conditions. It's essential to have some feedback mechanism, so you know at all times EXACTLY where the wheel is.
I've only just noticed, you are using a ULN2003 to feed the stepper!, this is a fairly puny IC, perhaps suitable for moving a printhead in an inkjet printer, but not for steering a car!.
It looks to me like the entire scheme is misconceived, a small underpowered stepper isn't a suitable device for this role! - you really do need a servo motor system (and I don't mean the little ones in R/C models). It will give you masses more power, faster response times, and accurate feedback about it's position.