RPM and PPR resolution

7 years 10 months ago #29527961 by ejstrates
I am using three MDC2250Cs to control motors in closed loop position mode.

The PPR of the motor encoders is more on the range of 20,000 (PPR < 20,000), far beyond the max of 5000. This forces me to scale the PPR down to 5000 (or less, for nice conversion factors).

Scaling the PPR also scales the RPM, causing an issue of resolution; the motors I am controlling are used primarily in low RPMs, and resolution in the range less than 0.1 RPM is important. The scaling factor increases the RPM \'epsilon\' above 0.1 RPM.

Is there a solution to this resolution problem? Is there a reason for the PPR max of 5000? It\'s not a power of two, so it seemed odd. Also, is there a way to increase the resolution of the RPM commands (!S)?

Even with enabling the full range of my PPR, I would still desire more resolution for RPM commands.

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7 years 10 months ago #29527962 by ejstrates
Replied by ejstrates on topic Re:RPM and PPR resolution
I may have found the solution:

Setting the Max RPM and using the Speed Relative command

If this is the solution, sorry for the hasty post!

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7 years 10 months ago #29527963 by ejstrates
Replied by ejstrates on topic Re:RPM and PPR resolution
Nevermind; that is only a query.

It would be a very good solution the desired velocity could be set relative to the Max RPM.

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7 years 10 months ago #29527964 by Griffin Baker
Replied by Griffin Baker on topic Re:RPM and PPR resolution
Have you tried setting your max velocity RPM in the closed loop parameters?

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7 years 10 months ago #29527967 by ejstrates
Replied by ejstrates on topic Re:RPM and PPR resolution
Excellent! The user\'s manual said that !S was in absolute RPMs, as set by the PPR, but you are correct! The !S command is indeed relative to the max RPM, as per my simple test through the RoboRun+ PC utility.

In another part of the manual, it states that there are different types of closed loop position modes, and that !S has different effects in each; I must be misunderstanding the information about the different closed loop position modes.

Thanks for the help!

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