Quote:
Originally Posted by thingstodo
Not sure if it would be undriveable, but it would certainly be different to accelerate or decelerate at a maximum programmed rate each time you change the throttle more than 1% or 2%, until the car is at the 'new' setpoint speed.
I might like to try it, just to see how different it is.
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My first inverter was open loop and worked exactly as you say. One had to adjust the throttle in 1 or 2% setpoints, but even that was not enough to avoid huge currents or the motor to loose sync during field weakening. Plus if one released the throttle the motor would act as a huge brake.
In practice to make it useful I used a speed ramp to ramp the speed up and down slowly and absorb any peaks, for example if one goes over a bump the throttle is going to jump a bit as well. The problem with the speed ramp is that if you are not able to have separate settings for acceleration and deceleration a ramp which is good for acceleration is too slow for the deceleration required and one ends up slamming the brakes against the motor during a fast stop.
In practice is never going to be nice to drive and requires the car to be undrivable by anyone but you.
Many industrial drives use current (amps) feedback to achieve a crude speed ramp closed loop, but this only works below nameplate speed.