Re: What is Gain and type of gains in servo settings
- From: Kirk Gordon <kg1@xxxxxxxxxxxxxxx>
- Date: Tue, 29 Jan 2008 20:45:10 -0500
040380@xxxxxxxxx wrote:
What is Gain and type of gains in servo settings? Iam confused with
these words .please help me to understand better
Gain is the amount of amplification that's done with signals sent from a machine's feedback devices (like encoders or linear scales) to the machine's control. It's one of several variables used to tune a servo system, and to establish how quickly, precisely, and energetically a servo motor responds to feedback information.
If gain is set too low, the servo system can become sloppy, achieving intended position only approximately, and drifting easily from that position in response to forces like those caused by cutting.
If gain is set too high, the servo motors can literally cook themselves trying to adjust instantly to every little bit of change in the feedback signal, even if the actual change in position is insignificant. Motors can actually be made to vibrate in place, dancing back and forth at high frequencies across distances that might only be a micron or two, depending on the resolution of the feedback device. On small servo motors, this can produce a kind of whining or whistling sound. On big machines, it can shake the walls and floor.
The other variables involved in servo tuning usually include a velocity setting or other time-based parameter that determines how fast the servos should respond to feedback signals, current settings that tell the control how hard it can work the servos while trying to achieve or maintain position, tolerances for what constitues "in position", and various kinds of tracking error limits that allow the servo to lag behind it's intended position by certain distances that depend on speed and acceleration characteristics.
Well tuned servos can be accurate, efficient, and smooth. Badly tuned servos can be a nightmare, and can make an otherwise sound machine act like something Wal-Mart wouldn't sell. Proper tuning is a complex balance between all of the above factors, and more, and often requires a lot of experience with specific motors and controls.
If your machine is running well, don't mess with the settings. It's easy to cause yourself a lot of grief. If you're having problems that you suspect are related to servo tuning, then watch carefully while an experienced person tweaks the system properly. After that, you can try it on your own; but be sure you make a back up copy of where you started with every number you change. That way, you can at least get back to where you started, if things don't go the way you'd like.
KG
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