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| Active vibration cancellation? - up to ~500Hz |
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| max_torque:
One of my customers has a motor test rig that has a bit of a vibration issue, because it's not stiff enough, and certain frequencies, the fundamental "once-per-rev" vibration sets up a bad ringing in the rig. There is the option of adding physical mass and stiffness, but i did wonder about whether an "active" cancellation scheme would be possible? The frequency is up to 500Hz, so not that fast in the grand scheme of things, and a large audio amp driving a "shaker" type subwoofer (probably need to be mass tuned) and somehow driven anti-phase to the main rotating assembly could work as the actuator. Anti-phase could be determined through the output of a vibration sensor, or i guess from a simple once-per-rev type sensor, with a calibratable offset as the position of the imbalance shouldn't' change once set up? Anyone done anything similar? |
| ruffy91:
What about doing the same as with a car motor? Make the mount softer so that the resonance is at much lower rpm. |
| OM222O:
instead of "active cancellation" easiest solution would be the one used in CNC milling operations: varying the spindle speed by +- let's say 10% so no one frequency has enough time to build up any significant oscillations due to resonance. what's the application (i.e: does it allow for variation in speed or not) and how is the motor speed controlled? (if it's controlled with a digital system, then it's easy to code the rpm change cycle) |
| ogden:
If you can find commercial active dampening system that meets the specs and customer is ready to hugely overspend (compared to passive system) - fine. Otherwise just consult noise & vibration analysis company/engineer. Those working in construction business most likely will be able to help or will point you in right direction. |
| soldar:
Why is this vibration happening? Unbalanced mass? Because maybe mechanical design could balance the rotationg masses. Passive measures like adding mass, rubber standoffs, dampers, etc. is going to be more practical, simpler and cheaper. My clothes washer weighs a ton and most of it is a large piece of concrete attached to the drum. Now, if you want to go all fancy you can approach this as a feedback design. Have three sensors in three axes which measure deviation and three actuators which can be solenoids or hydraulic. |
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