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I have a question regarding the types of motors that were used on the Martian rovers, specifically the Mars Exploration Rovers and Curiosity.

I am wondering about the main 6 motors that turn the wheels, so the rover can move forward or backwards, and the 4 motors that turn the outer wheels around their axes, so the rover is maneuverable.

I am pretty sure they used DC motors for both types of motors, but did they use brushed or brushless motors, and what specifications did those motors have? How did they make the motors have such a low RPM, and can they control the speed and motion of every motor's torque, voltage, current, etc.?

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MER uses brushed motors, Curiosity brushless. They both have a gear box on each motor with a fixed, very high gear ratio (a few thousand) for low speed and very high torque. The current to each motor is independently controlled and monitored.

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    $\begingroup$ Yes, all of the brush motors have lasted much, much longer than their 90-sol required lifetime. The short lifetime requirement of the mission and the lower complexity of driving brushed motors is why we used them on MER. In fact, one drive motor on Spirit failed, and one steering motor on Opportunity has failed, probably both due to the brushes. $\endgroup$ – Mark Adler Dec 15 '15 at 5:42
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    $\begingroup$ On MER they were 34V motors. The MER bus runs at about 28V to 32V. I don't know the motor ratings for Curiosity. $\endgroup$ – Mark Adler Dec 15 '15 at 6:07
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    $\begingroup$ Add the follow-up Q&A to your answer please. Comments are not meant to live on forever. $\endgroup$ – hiergiltdiestfu Dec 15 '15 at 10:13
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    $\begingroup$ Money, time, and heritage are all always considerations in space missions. There was no existing space-qualified brushless motor controller available, and so it would have to be developed, add development risk, cost money, and take up rover resources (mass, power). Since the mission had a 90-sol lifetime requirement, brushed motors would easily support that lifetime, were far easier to control, and there was no development risk. If you can meet the requirements with a simpler system with less development risk, then that's what you do. $\endgroup$ – Mark Adler Jul 30 '17 at 16:35
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    $\begingroup$ Brushed motors can provide a bit more crash/impact resistance for the same torque, and MER delivery through "airbag" needed quite rugged devices able to survive the impact. Brushless motors require permanent magnets (which, if you want good field strength, happen to be brittle). Brushed motors can use electromagnets both for stator and rotor, and electromagnets are quite invulnerable against mechanical shock. $\endgroup$ – SF. Sep 16 '17 at 15:41

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