Interview with Ann Scanlan
Active Vs. Passive Vibration Isolation Technology
Interview conducted by Will Soutter
Please can you give a brief introduction to Herzan and your products?
For over two decades, Herzan’s mission has been to help researchers maximize the quality of data collected by their instrumentation. To achieve this goal, Herzan has designed industry-leading environmental solutions to isolate acoustic, vibration, and EMI noise under any ambient lab conditions.
Herzan’s catalogue of environmental solutions focuses on three critical areas: research-grade isolation performance, application-tailored design, and premium production quality. These three areas drive product design at Herzan and are represented in all acoustic, vibration, and EMI isolation solutions we offer.
How was the company founded, and how has it grown since then?
I founded the company in 1992 as an American subsidiary of Herz Company Ltd., a Japanese company specializing in vibration control. We began operations supporting customers in North and South America for the various vibration and acoustic control solutions they offered. The name Herzan was inspired by this partnership and became an amalgamation of the two words ‘Herz’ and ‘Ann’.
We later included active vibration isolation platforms from Table Stable to offer a more comprehensive solution for customers being affected by low-frequency vibration noise. After the success of adopting active vibration isolation platforms, we expanded into addressing another source of noise commonly affecting customers: acoustics. Our acoustic enclosures were originally designed in collaboration with Herz to produce the precision research industry’s quietest operating environment. Over time, the needs of our customers shifted towards smaller, more customized acoustic and vibration isolation solutions, which is why we complemented our range of products to include desktop and modular isolation solutions, capable of scaling to fit specific instrument sizes and form factors.
Herzan offers both active and passive vibration isolation solutions – can you quickly outline the differences between the two technologies?
Passive vibration isolation systems are a simple form of vibration isolation that can be very effective as long as building vibrations are not near the natural resonant frequency of the isolators. A passive vibration isolation system can be considered a spring, either mechanical or pneumatic, passing vibrations through the structure at frequencies lower than the resonance. At the natural frequency resonance of the passive isolator, the energy entering the system is amplified into the payload (i.e. system being supported). Conversely, frequencies greater than the natural frequency resonance of the passive isolator, the energy entering the system is reduced. Passive isolators are often tuned to have a low frequency resonance, thereby isolating as much of the frequency spectrum as possible. The low frequency resonance correlates to a very “soft” system.
Active vibration isolation systems are considered passive systems that have an active component, dampening the resonance out of the system isolation system itself. The most common configuration for an active vibration isolation system is to have a sensor and actuator to help dampen the low frequency resonance of the system. An active isolation system with a feedback loop will sense the vibration noise and counteract them with an equal, opposite, and out of phase force.
What are the main applications where active isolation is required to achieve good results?
Active vibration isolation systems are of great importance where low frequency vibration isolation is needed. This is common in environments where the building has a low resonance and/or the supported system itself is sensitive to low frequency energy. With multiple designs and form factors available to suit instruments large and small, active vibration isolation platforms are able to solve most vibration problems affecting the research industry’s most demanding applications (SEMs, AFMs, and more).
In addition to isolating low-frequency vibration noise, active vibration isolation systems are significantly more stiff than passive systems (up to 500x stiffer). The additional stiffness offers users an easier operating surface to work on, making them more efficient in their research.
How does the technology behind Herzan’s active isolation systems work?
There are two types primary technologies employed for active vibration isolation platforms—feedback and feedforward systems. The feedback system constantly and dynamically senses noise entering the system and sends an equal, inverse out of phase force to cancel the vibration. With feedback systems, there is some lag time in this dynamic response, which is typically less than 20 milliseconds.
Feed forward systems are used for ultra-low frequencies or when the incoming vibrations are known, such as a payload on a stage, where the control system anticipates incoming vibrations and provides a signal to counter the vibration noise as they enter the system. If a feedforward system does not properly characterize and the incoming vibration levels, it can be difficult to ensure ideal performance. Tuning to the vibration signature of the room is often required to optimize performance.
Herzan’s AVI and TS Series active vibration isolation platforms are a feedback control system, offering reliable and dynamic vibration isolation performance in any environment. Herzan also offers a feed forward add-on for the AVI Series (called the LFS System), which addresses ultra-low frequency isolation.
Are the are situations where active vibration isolation detracts from performance?
Not really. A properly designed active vibration isolation system will only enhance performance at the lower frequency range of vibrations. Since active vibration isolation systems have sensors and actuators, they use energy that can cause heat to generate, which may be an issue for heat sensitive applications in an enclosed environment (i.e. acoustic enclosure). Heat issues, however, can be easily managed by moving the power supply away from the tool or outside of the enclosed environment. The actuators and sensors used in the AVI and TS Series consume very little power, typically less than 10W, meaning thermal drift caused by heat generation is not typically an issue.
What are the benefits of using passive vibration isolation in research applications?
Passive vibration isolation systems offer very good performance as long as the environment is not susceptible to low frequency vibration noise (i.e. less than 10-15 Hz). Passive vibration isolation systems are also very affordable compared to active vibration isolation systems, making it a more widely applicable solution to resolve vibration noise.
How does the technology behind Herzan’s passive vibration isolation systems work?
Herzan’s passive vibration isolation systems use a series of springs, surge tanks, and damping orifices. The damping orifice serves to reduce the amplitude response at its natural frequency resonance, where the energy is amplified. Additional features relating to levelling, drilled and tapped holes, cleanroom compatibly, and workstation integration are also available for customers with unique research requirements.
What does the future hold for Herzan and vibration isolation technology?
Herzan continues to invest in the technological development of its products, driving innovation that falls in line with the company’s overall strategy: improving product performance, enhancing the user-experience, and offering solutions uniquely relevant to the needs of the researcher. Additionally, we continue to research ways in which we can offer solutions that range in terms of price and performance, offering improved overall value to our customers.
Ann founded Herzan in 1992 in Orange County, California. She received her B.S. in Mechanical Engineering from the University of Missouri and her MBA from the Merage School of Business at UC Irvine. Ann has over 25 years experience in the field of vibration control, including leading the Melles Griot vibration control division and working at Herz Co. LTD. Ann oversees Herzan’s engineering and new product development activities.