Minus K Technology

Laser Interferometer Vibration Isolation Interview with David Platus, President and Founder of Minus K Technology, Inc. and principal inventor of Negative-Stiffness Mechanism vibration isolation systems.


PSD: Tell us about Minus K Technology.

DP: Minus K Technology was founded in 1993 to develop, manufacture and market state-of-the-art vibration isolation products based on the company's patented Negative-Stiffness Mechanism
(NSM) technology. The company's products are used in a broad spectrum of applications including photonics, nanotechnology, biological sciences, semiconductors, materials research, zero-g simulation of spacecraft and high-end audio.

PSD: What is Negative-Stiffness vibration isolation?

DP: Negative-Stiffness isolators employ a completely mechanical concept in low-frequency
vibration isolation. It is really quite unique to the field of laser/optical systems. In particular, the transmissibility ? that is the vibrations that transmit through the isolator relative to the input vibrations ? is substantially improved over air systems and active isolation systems.

PSD: How does Negative-Stiffness vibration isolation work?

DP: Negative-Stiffness isolators typically use three isolators stacked in series: a tilt-motion isolator on top of a horizontal motion isolator on top of a vertical motion isolator. Vertical motion isolation is provided by a stiff spring that supports a weight load, combined with a Negative-Stiffness mechanism. The net vertical stiffness is made very low without affecting the static
load-supporting capability of the spring. Beam columns connected in series with the vertical-motion isolator provide horizontal-motion isolation.

PSD: What specific performance results does Negative-Stiffness vibration isolation deliver?

DP: The isolators adjusted to 0.5 Hz achieve 93 percent isolation efficiency at 2 Hz, 99 percent at 5 Hz, and 99.7 percent at 10 Hz.

PSD: What advantage do Negative-Stiffness systems have over air tables?

DP: Negative-stiffness systems provide substantially lower natural frequencies vertically and horizontally enabling them to isolate lower frequency vibrations and provide improved isolation over the entire range of building and floor frequencies. Further, the need for pneumatics and electric power is eliminated with Negative-Stiffness systems.

PSD: How does Negative-Stiffness compare to active isolation systems?

DP: Active isolation systems start isolating as low as 0.7 Hz. But, because active systems run on electricity, (NSM does not require electricity) they can be negatively influenced by problems of electronic dysfunction and power modulation, which can interrupt scanning. Active systems also have a limited dynamic range which is easy to exceed, causing the isolator to go into positive feedback and generate noise underneath the equipment. Although active systems have fundamentally no resonance, their transmissibility does not roll off as fast as NSM isolators.

PSD: Has the photonics industry embraced Negative-Stiffness Systems?

DP: Negative-Stiffness vibration isolation has become a growing choice for laser and optical applications. Not only is it a highly workable vibration solution, its cost is significantly less ? up to one third the price compared to active and traditional passive systems ? making it an economical solution to cost-conscious administrators.

PSD: What three Minus K achievements are you most proud of?

DP:1. Being selected to provide the isolation system for ground testing of the James Webb Space Telescope (JWST) and other major NASA and DOD programs. 2. Solving a customer's vibration problem with a TEM on the fifth floor out of spec between 1.5 and 2.5 Hz. 3. Getting rave reviews from audiophiles who are "blown away" by the improved sounds from their audio systems and passing jump tests on wood frame floors. 

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