None.
The present invention relates generally to thin-line towed arrays, and more particularly to an apparatus that measures tension in a thin-line towed array.
Naval vessels use thin-line towed-array systems that are up to several miles in length and contain a network of delicate telemetry and sensor components. Each module of the thin-line array includes an outer sheath or hose that contains hydrophones and supporting electronics.
Referring to prior art of
Accordingly, substantive improvements in tension sensors are needed for towed arrays. However, developing a sensor for the thinline, towed array may be challenging because of the small diameter and other integration requirements.
The present invention uses a planar tab that facilitates a tension sensor function as well as the construction of the strength package in the towed array where the tension sensor is installed.
The tension sensor includes the planar tab having a first side and a second side, a first end section and a second end section, and an aperture or hole through each of the end sections. A first strain gage is positioned on the first side of the tab. The strain gage has a tension grid aligned with a longitudinal axis of the tab and a cross-tension grid perpendicular to the tension grid. A second strain gage attaches to the second side of the tab. The second strain gage has a tension grid aligned with the longitudinal axis of the tab and a cross-tension grid perpendicular to the tension grid.
The first strain gage and the second strain gage are wired in a Wheatstone bridge in which the tension grid and the cross-tension grid of the first strain gage form one side of the Wheatstone bridge and the tension grid and the cross-tension grid of the second strain gage form another side of the Wheatstone bridge. Voltage change across the Wheatstone bridge is measured as a function of strain on the tab.
An array hose is formed as part of the thin-line towed array with an internal strength member inside the hose. A clevis defines a termination point of a module of the array. The hose and the strength member connect to the clevis. The internal strength member includes a plurality of ropes that terminate on the clevis. Typically, there is a clevis or termination point on both ends of the towed array. The tension sensors attach to a portion of the plurality of ropes.
Other objects, features and advantages of the present invention will become apparent upon reference to the following description of the preferred embodiments and to the drawings, wherein corresponding reference characters indicate corresponding parts throughout the several views of the drawings and wherein:
Strain may be defined as deformation experienced by a body resulting from an application of force. According to an inventive apparatus described herein, a tension sensor fits within a small diameter array hose such as an array hose 108. That is, the outer diameter and rigid length of the tension sensor must be less than the maximum that the array hose 108 can accommodate. Larger diameters must have proportionally smaller rigid lengths.
A strain gage measures the amount of strain on a given object by converting a dimension change to a change in electrical resistance. Referring to
The planar tab 112 has a first end section 118 and a second end section 120. Apertures or holes 122 are provided through each of the end sections 118, 120. A first strain gage 124 attaches to the first side 114 of the tab 112. The strain gage 124 has a tension grid 126 aligned with a longitudinal axis of the tab 112 and a cross-tension grid 128 perpendicular to the tension grid 126.
Referring to
The cross-sectional area, “A” of the tab 112 is calculated in Equation (1) from the definition of Young's Modulus, where “F” is the maximum design tension, “E” is Young's Modulus, and “ϵ” is the strain when the maximum design tension is applied.
In this example, T-rosette strain gages are used. The cross sectional area of the tab 112, A=w*t, is set by choosing ϵ to be 2,000μϵ—per the specifications of the strain gage manufacturer. And F is set to match the breaking strength of the rope 104 that the tab 112 interrupts (1,200 pounds in this situation). Accordingly, the rope 104 will break before the tab 112 exceeds the region of elastic deformation for the rope. The stress concentration at the apertures 122 on each side 114, 116 determine the required thickness. In the described examples, Titanium Ti6A14V was used to keep thickness to a minimum while preserving strength, but unalloyed titanium, aluminum, or aluminum alloys could also meet strength requirements and fit in the towed array module 100.
As shown in
The tension-induced strain proportionally changes the voltage E0. “E” is the excitation voltage supplied to the Wheatstone bridge 136. The resistance of the tension grid 126, 132 parallel to the tension axis (the longitudinal axis of the tab 112) varies linearly with strain (ϵ) along the tension axis and the resistance of the cross-tension grid 128, 134 perpendicular to the tension axis varies linearly with perpendicular strain (−vϵ) where v is Poisson's ratio. The cross-tension grid 128, 134 leverages Poisson's effect to prevent thermal expansion and contraction in the tab 112 from affecting E0. In another embodiment, mounting cages can be used on each side of the tab 112 to prevent bending from affecting E0.
The response of the Wheatstone bridge 136 is calculated by Equation (2)
where “R” is the bridge output in mV/V, “G” is the gage factor provided by the manufacturer, and “v” is Poisson's ratio of the material on which the gage is mounted, 0.342 for Ti6A14V in this case. Equation (2) can be used with Young's modulus to calculate responses.
The tension sensor 110 interfaces with the telemetry of the thinline towed array. A sensor node relays a voltage measurement up the data stream of the towed array. Two voltage inputs are used by the sensor node and the node provides the voltage excitation for use in the resistive tension sensing element. As shown in
Each of the four tabs 112 has the strain gages 124, 130 arranged in a full-bridge output. The strain gages 124, 130 are not shown for clarity in
The tabs 112 are spliced into four of the ropes 104 in the ISM 102. For accuracy and stability, a tab 112 could be spliced into each of the ropes 104, but the sensor node in the towed array only uses two inputs. Data from the four tabs 112 is averaged in pairs in order to provide two outputs for input to the sensor node.
At step 142, a first strain gage is bonded to a first side of a tab with the tension grid of the first strain gage aligned with the longitudinal axis of the tab. At step 144, a second strain gage is bonded to a second side of the tab with the tension grid of the second strain gage aligned with the longitudinal axis of the tab. At step 146, the first strain gage and the second strain gage are wired in a Wheatstone bridge in which the tension grid and cross-tension grid of the first strain gage form one side of the Wheatstone bridge and the tension grid and cross-tension grid of the second strain gage form another side of the Wheatstone bridge.
At step 148, a first end of the tab is connected to an end of a module of the thin-line towed array. At step 150, a second end of the tab connects to the internal strength member inside the module of the thin-line towed array. At step 152, voltage change across the Wheatstone bridge is measured as a function of strain on the tab.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.
The invention described herein was made in the performance of official duties by employees of the U.S. Department of the Navy and may be manufactured, used, or licensed by or for the Government of the United States for any governmental purpose without payment of any royalties thereon.
Number | Name | Date | Kind |
---|---|---|---|
5855179 | Wood | Jan 1999 | A |
5948959 | Peloquin | Sep 1999 | A |
6253627 | Lee | Jul 2001 | B1 |
6378383 | Lee | Apr 2002 | B1 |
20040013036 | Fageras | Jan 2004 | A1 |