Hi there. I'm West Wigglesworth with TMC, and I'm here at our headquarters in Peabody, Massachusetts, just north of Boston. And today, I will be talking about vibration control, and the key differences related as compared to passive vibration control. So first, I thought I'd start off by talking about some of the key elements that are required to really call something active vibration control. So, really, the three key components are an inertial sensor that actually measures the vibration, a control system with a feedback loop. And an actuator. Alright. So one of the things about active vibration control and passive vibration control is that The terms can be interchanged and sometimes confused. So I wanted to just back up and give some examples about both types of systems. And I was going to start with something that the industry as a whole really agrees on, and that is that a simple spring is a passive isolator. So something like steel spring between two two steel plates, a rubber mount, and something like an air chamber that simply gets pumped up with air and you put your payload on top of these type these isolators, four of them typically. And it supports the payload, and it attenuates vibration but only a very high frequencies, and it's very dependent on the resonant frequency of the spring. So rubber springs could be an eight hertz isolator, ten hertz, even hertz isolator, and a steel spring could be something like four hertz or seven hertz. And, of course, an air spring is typically a little bit lower frequency, and that's important because anything below any vibration that is below that frequency coming from the floor will not get attenuated. So these simple simple rubber mount steel springs, they're easy to set up. There's no height control and their promote performance again, mainly because they're only attenuating for vibration that is above that resonant frequency. So very high frequencies are attenuated. Now typical applications for simple passive rubber mounts are things like simple optical microscopes, low power, low magnification, machinery in a factory if you're trying to reduce the impact of that machinery on the rest of the factory. These would be simple rubber mounts that are used in applications that. Very very low low low magnification type of instruments things that are not highly sensitive to to floor vibration. Now the next step up would be something known as pneumatic isolation. And one of the first differences is that it's a little bit more difficult to set up. So with a pneumatic isolation system, the vibration isolation performance is much better than a simple rubber mount or steel spring. Because it's a softer isolator. It has a resonant frequency of around two hertz, maybe a little bit less than that, maybe a little bit more, But it's attenuating floor vibration starting at around four or five hertz compared to a simple rubber spring that amplifying at that frequency or even amplifying at a higher frequency. So pneumatic system, little bit more difficult to set up than a passive spring but well worth it. And typically includes a mechanical self leveling system, which is a high control valve and a mechanical linkage to the payload, and that senses, you know, a deflection in the payload and re levels that payload. It does require continuous supply of air or nitrogen. And an option for the height control is electronic non contacting height control. And another option in combination with a pneumatic spring is an active damping system. Now some will consider pneumatic isolator with self leveling height control to be an active vibration control system, but it's really not. It is passively attenuating the floor vibration. Yes. There's a sensor, but it's a mechanical linkage to the payload. That is reacting to the deflection of the payload and then controlling the air in and out of the isolated to re level. The the isolator and the payload, but it's not active vibration control. There's no inertial sensor, and there's no active feedback loop or feed forward loop. With these other options, electronic height control. Again, some might consider that active vibration control, but it really is just to improve the precision of the height repeatability system and the the height control system. With active damping, we would add a sensor to the payload So it'd be, you know, a sensor mounted to the payload, and a signal back to the controller, which then activates the air going in and out of the isolator to really only reduce the amplification at the resonance of the air isolator. So that is an active control system, but it's not improving the overall performance of the vibration isolation system. It's only attenuating the amplification of the resonance of the the air isolator. Typical little applications for pneumatic isolation are things like high magnification optical microscopes, atomic force, and confocal microscopy applications like electrophysiology and other other techniques used in life science research. And a good example of that is TMC's clean bench table and micro g isolators. So this is a a pneumatic isolator. It's about a one and a half to two hertz resonant frequency, and the table is supported by these springs and is fairly soft. If there was a moving stage on top of the payload, the the payload would deflect. And it would it would bounce around a little bit before it settles down. So taking some of these advanced features that are coupled with a pneumatic system and taking that to the next step would be something known as a parallel type active vibration control system. And in this system, we start with a pneumatic isolator. We have non contacting electro pneumatic pipe control. We include the active damping of the payload, but we also add linear motors as an actuator. And when this is combined in a feedback system, it is very good at canceling stage motion. So it's a very high performance system. It's a bit complex. Certainly more more involved in in the setup and initial tuning, but it's very, very good for supporting payloads that have a moving stage. When the stage moves, a pneumatic spring would normally deflect pretty easily. But by adding the linear motor, in parallel with the with the pneumatic spring as part of a feedback system, it is setting a force to payload to cancel the deflection of that payload. It can also one of the other nice things about this type of system is that it can be connected to the to the stage of of the tool, and information from that stage can be used in a feed forward manner to even more aggressively cancel that stage motion. Now is this an active vibration control system? It sure is. No doubt. But in terms of vibration isolation of the floor, it's really defined by the the spring that's being used. So if it's a pneumatic ice layer, which is common, could also be a steel spring or even a rubber mount, but this different the spring, the less impact the the the the motor has. But in terms of floor vibration isolation, it's really defined by that that that spring. So in this design, these these add ons such as the linear motor, the act of damping, It's all working to either cancel the stage motion or reduce the amplification at the resonant frequency of the air spring. So the attenuation of floor vibration is not necessarily improved. Slightly, particularly, again, at the amplification or, excuse me, at the resonant frequency of the isolator, but not beyond that. So it's a very it's very limited in terms of bandwidth for floor vibration. TMC's electro dam is an excellent example of a parallel type active vibration control system. And while these systems are limited, in terms of their active bandwidth for for floor vibration control, something like electric damp is really well suited for being designed into semiconductor manufacturing tools, like with from metrology instruments that use an electron beam, and moving stage to position the the the wafer to inspect and move on. So canceling that stage motion is critical in improving the throughput and maximizing yield and throughput in semiconductor manufacturing. The max type of active vibration control is a serial type active vibration cancellation And with this system, it's actually a little bit easier to set up than an electro damped parallel type system. It's in comparison, quite simple yet advanced in its technology. It utilizes rubber spring elastomer inside the isolator, so provides a very stiff and stable support of the payload. The the active control system is decoupled from the payload because it is in series with a rubber spring. So the high frequency rubber spring actually decouples the active control system from the payload, the control system is downward looking, so it's looking at the floor. It's measuring the vibration coming up from the floor not the payload. And as a result, it has the largest bandwidth available for active vibration control. Down to below one hertz and up to over a hundred hertz. So this system is quite unique TMC's stasis system is a is a prime example of this technology, and it is the most advanced commercially available system using piezoelectric actuators, inertia sensors to to measure for vibration down to variable frequency, and a very special rubber mouth that has a frequency in the fifteen to twenty hertz both twenty hertz, both vertically and horizontally. So common applications for this are actually supporting tools that have something like a bacterium built into them or pneumatic isolators, simple nomadic isolators built into them like electron microscopes, SEMs, and TEMs are commonly supported by something like this because those tools are being installed in environments that have that have very low frequency vibration coming from the floor, which will limit the performance of the tools because they have pneumatic isolators built into them and they're very sensitive to flow vibration at low frequencies. So again, know, there's an inertial sensor, there's a control system, an actuator, is this an active system? Absolutely, it is. And it's one of the not only the most advanced, but often the only choice for supporting tools in a harsh environment when low frequency is the problem. So in summary, when you are looking for a vibration isolation system and you hear the word active or or you think you might need active vibration control you definitely wanna ask the question, does it have an inertial sensor? Is there a feedback or a feed forward control loop? And is there an actuator to react to the signal coming from the inertial sensor in the control system to cancel that vibration? So that's it for today. Again, I'm West Wigglesworth with TMC. See you next time.
