Dear everyone,

I was wondering, if I am desiging a survey vehicle where I need to scan an area and need to plot positions of certain points, is it better to use stepper motors for the wheels? Or DC motors good enough.

I am used to using DC motors and have not used stepper motors before, but what I gather from research is that stepper motors may allow more precise knowledge of the location of the vehicle/robot. Or is the DC motor good enough using knowledge of the Pulse Widths used to control these motors?

I am looking at a chassis that comes with 4 DC motors for each of its wheels. But I am just considering this issue before I commit to buying it.

Any background information for me is greatly appreciated. Thanks in advance.

Regards.

 

It is not. You would need feedback to determine how many turns the wheels or motors have made.

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Check out:
Implementing Dead Reckoning by Odometry on R/C Servo Robot

Thing is, DC motor + feedback gives you pretty much same info as stepper motor, even more precise as for stepper motor you cannot be sure motor actually turned if you do not have any feedback from the wheels. The problem in both cases (stepper vs dc) is that wheel slippage is not "detected" so if you need "100% accuracy" you have to go few steps further.

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Thanks very much!!

Thanks for the link arhi...

Does anyone know any place who sell robot chassis of this form factor:
Active Robots - Mobile Robot Platforms - Lynxmotion 4 Weel Drive Rover Chassis - UK

(ie. this type of body, bit like a tractor and not like a micromouse)

with Stepping motors instead of DC motors? Ive done some google searching, but stepping motor with chassis of the form Im looking for is proving toush to find.

Im prefering Stepper motors at this stage, Encoder + DC Motor next. I am not going to worry about wheel slippage at this stage.

Thanks again.

 

You should... Steppers are great devices, but relying on their operation alone for accurate position doesn't work unless you massively over rate the steppers and the current needed to drive them. Slippage is life, you have to account for it. With a stepper, you're stuck with whatever the stepper limitations are, the degrees per step and any slop in the gear train itself along with it's torque limitations

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Fortunately, as steppers are such low speed devices, you don't need any gears - you can drive the wheel directly. So the only 'slip' is between the wheel and the ground.

I don't know if you've ever played with 'roamer', I helped assist kids at my local primary school with him a number of years back - the older roamer back them used stepper motors, and maintained a remarkable degree of 'straightness'. I presume the newer ones still use steppers?.

Valiant Technology

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