POST No. 2407342
How to limit the rotational velocity
2019-03-13 10:52:32 aussiesusan

I have a couple of XL430-W250-T servos that are used to drive a slightly heavy but off-centre load and I want to limit the speed the servos can rotate.

One servo is in position control mode and the other in extended position control mode.

If I want to set the maximum rotation speed to (say) 2 revolutions a minute, is this done purely through the 'velocity limit' EEPROM value?

(Sorry to ask if this is a basic question but I'm away from my for a couple of days and so I can't experiment.)


2019-03-13 10:52:32
2019-03-13 11:43:13 Will Son

Hi Susan,

Yes, you are correct.

You can control the RPM by setting the Velocity Limit(44).

However, if you set it in the EEPROM, you'll not be able to modify the value during the motion without turning the torque off.

So, if you need to change the value during the motion, I'd recommend using the Profile Velocity(112).

Please note that the updated Profile Velocity value will be applied only when a new Goal Position is written to the RAM area.

Thank you

2019-03-14 11:19:06 aussiesusan
Thanks Willson.
The velocity is a 'set and forget' value for this situation so Velocity Limit sounds like the way to go.
2019-03-14 11:19:06
2019-03-13 11:43:13
2019-03-28 11:12:45 Susan Mackay

For anyone else coming across this topic, the Velocity Limit setting works BUT only if Profile Velocity is set to a non-zero value - if it is the default of 0 then the 'Step' profile is used and the servo turns as fast as it can to the new position.

I ended up setting both the Profile Velocity and Profile Acceleration to non-zero values to get the trapezoidal profile and I not get a nice and smooth rotation at the speed I wanted.

All of this is in the data sheet but unless you read about the Profile Velocity parameter (where it talks about the various profiles) you would miss the need to look at other parameters as well.


2019-03-28 11:12:45
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