Increasing stepper motor speed given a fixed power source

Hey all,

I am currently using my Arduino in conjunction with an Adafruit Motor Shield to control two NEMA-17 Stepper Motors. The motors are being powered by a 7.2 V, 3000 mAh NiMH battery pack. This set-up is being used for an electric vehicle, which must travel as fast as possible and come to a stop at a specific distance.

While the precision of the stepper motors allows the vehicle to stop at specific distances, it is currently moving very slowly. I was wondering if there is any way to significantly increase the speed of the vehicle using my current power source? The vehicle only needs to move quickly for a short period of time - would it be possible to use capacitors to provide the necessary surge of power?

Links to parts:
Adafruit Motor Shield
Battery Pack
Stepper Motors
Stepper Motors Datasheet

  1. Stepper motors are a poor choice for traction - slower, much much less energy efficient. DC motor with encoder is the normal approach.

  2. H-bridge shields are not the way to drive a stepper, a stepper-motor chopper-drive is the way to drive
    a stepper, such as DRV8825 etc.

  3. Higher voltage supply will give you higher top speed for a chopper-driven stepper. That's inescapable.

[ and I just noticed you have a high-impedance stepper, so no chance of any speed at all at 7V, you might get 120 rpm if lucky... ]

That motor is particularly unsuitable for a 7.2v supply. It is intended for a minimum of 12v and I have something similar that I power at 19v.

I think your choices are either to increase the voltage or change the motor. A motor designed for a much lower minimum voltage (say 2v or 3v) will consume a lot more amps and if you want to run on battery power the better solution might be to increase the voltage and stay with the low current motor. Maybe put in a second battery pack connected in parallel to give 14.4v.

I guess you could try gearing UP the motor output. But I doubt if that would work work because it would reduce the torque at the wheels. If you already have some convenient gears or pulleys it might be worth trying. But I don't think I would waste time and money buying gears.

...R
PS. Plus what @MarkT said.

Stepper Motor Basics
Simple Stepper Code