United Technologies Corporation

Max A Schaffer

Mario T Lopiccolo

Donald H Isakson

George A Jachyra

Joseph P Hu

In a fluidic angular rate sensor in which a pair of temperature sensitive resistive elements are differentially cooled by a jet of fluid, the direction of which lags the position of the resistive elements when the rate sensor is rotated in the plane of sensitivity, undesired, long term errors that result in the lack of a zero null (when the unit is not undergoing any angular rate) are compensated for by introducing a voltage equal to the zero-rate null offset, determined with the velocity of the fluid jet reduced to a point below which it has any appreciable effect on the sensing bridge (simulating static conditions), together with an input to the bridge to offset its output so that the static null offset to be usable to compensate the dynamic null offset (that is, the offset in the null determined with the fluid jet in full operation). In one embodiment, the bridge is offset during the static null error determination, thereby to offset the stored, null error; in another embodiment, the bridge is offset during operation, but not during the static null determination, so the offset and the static null error together compensate for the dynamic null error. The fluid jet may simply be reduced, and not completely stopped, thereby to avoid static laminar conditions and pressure differentials in the static fluid resulting from accelerations; or, the fluid jet may be completely eliminated during the compensating null voltage generation procedure.

Fluidic angular rate sensor null error compensation

The measurement bridge of a fluidic angular rate sensor in which a pair of temperature sensitive resistive elements are differentially cooled by a jet of fluid, the direction of which lags the position of the resistive elements when the rate sensor is rotated in the plane of sensitivity, is driven by a constant voltage source through resistances substantially equal to the rate sensing resistive elements so that as the resistive elements increase in resistance with temperature, the voltage also increases, so the power consumption and therefore the heat generated in the resistive elements remains constant, thereby tending to maintain a constant temperature differential of the resistive elements above the ambient, and in turn reducing changes in thermally-induced mechanical stress and resulting motion; further, lack of tracking between the two resistive sensing elements over wide temperature ranges is compensated by coupling some of the resultant temperature-dependent voltage to a bridge node to compensate for the temperature-dependent mismatch, said voltage being nulled at normal temperature by coupling of fixed voltage of opposite polarity to the same node.

Temperature stabilized fluidic angular rate sensor

The nozzle of an angular rate sensor which directs a stream of fluid toward a pair of temperature-dependent sensing resistor elements is formed in a major block which defines the chamber within which the sensing elements are also mounted, thereby to mitigate problems of aligning the jet with respect to the chamber and of aligning the sensing elements with respect to the nozzle. Within the casing, only the nozzle block, a diaphragm pump assembly, and an anvil need be mounted; these are secured by a lock nut, the pressure thereof being applied through a conical Belleville spring. A fine weld is used to hermetically seal the element, but the weld can be cut off without damage to the unit; so that by loosening the lock nut, the entire apparatus can be disassembled without destruction. Reference resistors, for a bridge to measure changes in the sensing elements, are mounted directly within the unit, to avoid bridge misbalances due to external connections.

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Fairfield, CT, United States of America

Max A Schaffer