SBIR-STTR Award

The size of conventional split ring transducers is much smaller than a wavelength at operating frequency leading to a high Q resonance and limited operating bandwidth. The proposed work will investigate two different modifications to the split ring structure that allow its resonance frequency to be adjusted under active control so that it is always operated at or near its resonance. Because the transducer is always operated at resonance, the phase of its input impedance is approximately constant, vastly simplifying the design of the transmit power amplifier and reducing the size and weight of the system. A high Q system is desirable for an actively tuned system resulting in very high efficiency and allowing the use of less expensive shell materials. The first concept for a variable compliance transducer would replace a section of the shell near the hinge with a magnetostrictive portion; the compliance would be adjusted using the Delta E 0x9D effect which changes modulus of the active material with stress and magnetic state and thus shifts the transducer resonance. The second concept utilizes stiffening members located near the hinge of the ring; the stiffening members are selectively actuated to change the compliance of the ring and shift the transducer resonance. Both these concepts are broadband, efficient transducers that can reach source levels in excess of 210 dB, resonant frequency less than 1 kHz, and bandwidth greater than 200 Hz.

Benefit:
Anticipated benefits of the proposed research are efficient, broadband, low frequency transducer concepts that can be used to obtain the desired detection ranges against quiet threats in deep and littoral waters. These transducer concepts are targeted at frequency ranges below 1 kHz with source levels in excess of 210 dB and bandwidths greater than 200 Hz. Applications for these transducers include unmanned surface vehicles (USVs), unmanned underwater vehicles (UUVs), and sonobuoys. The transducer resulting from the proposed research is expected to be scalable and reconfigurable such that it can be adapted for both Navy and commercial applications. The oil and gas industry use compact, low frequency transducers for oil exploration and inspection of oil wells and would benefit from greater performance and reliability. Also, low cost, high power low frequency transducers may be useful as a deterrent to hostile swimmers/divers for harbor and ship defense.

Keywords:
Variable Compliance, Variable Compliance, Delta E effect, slotted cylinder transducer, magnetostriction

Etrema Products, Inc. and Applied Research Laboratory at The Pennsylvania State University demonstrated during Phase I that by utilizing the delta-E 0x9D effect in magnetostrictive materials, the resonant frequency of a split ring transducer can be shifted by over 200 Hz for a low frequency transducer. A variable reluctance driver helps achieve source levels in excess of 210 dB with a potential 80% cost reduction as compared with a similar PZT transducer. The Phase II effort will focus on building hardware and verifying the performance and cost, and scalability of the transducer. Objectives of the Phase Base II effort are: 1. Identify the most viable compliance hinge mechanism and controller algorithm, 2. Demonstrate feasibility of the variable reluctance driver, 3. Demonstrate technical feasibility of the transducer including the controller. The Phase II Option Objectives are: 4. Identify performance limits of the transducer by testing the first article transducers, 5. Demonstrate the transition potential of the technology by optimizing the transducer design. Successful completion of the Phase II and Phase II Option efforts will result in a low-cost, low-frequency transducer design that can be transitioned to Navy applications.

Benefit:
The proposed variable compliance Galfenol SCP technology addresses the Navys defined need of having comparable or improved sonar systems at lower cost. Performance predictions of the variable compliance concepts indicate that high source levels in excess of 210 dB with a 200+ Hz bandwidth are achievable in the frequency range of interest,

Keywords:
delta-E effect, transducer, split ring transducer, variable reluctance, Magnetostrictive