How the QUBIK Inertial Measurement Unit Senses Rate

Melvin Mark Morrison

Abstract:	The QUBIKtm IMU senses rate, proving it is possible to make a multi axis gyro using a cubic proofmass. The proofmass is magnetically levitated with an arrangement of three orthogonal sets of linear parallel arrays of permanent magnets embedded into the faces of the cube. There are three magnets per side totaling 18 per proofinass. The outer housing cavity likewise has a similar arrangement of electromagnets that come in face to face relationship with the permanent magnets on the proofmass. The larger center magnets are used for activeIy applying restoring forces for capturing linear accelerations and the smaller outer magnets are used for actively applying restoring forces to capture angular accelerations. The inside cavity of the outer housing has an arrangement of 36 variable capacitance pins (six per side) used for detecting the position of the proofinass within a XYZ Cartesian coordinate system This basic concept of levitating a cubic proofmass, without using any mechanical attachments, provides three independent orthogonal linear accelerometers and three independent orthogonal angular accelerometers. With the proofmass levitated, momentum is generated by injecting an AC reference signal into one of the angular accelerometer channels to set up an oscillation of the proofinass about an initial first axis. When the entire system is rotated about a second axis, a gyroscopic oscillation precession is detected about a third axis. The gyroscopic oscillation precession amplitude is proportional to the magnitude of the applied angular rate and is either in phase or 180 degrees out of phase with the reference signal, depending on the system rotational direction. Systems have been built and tested to thoroughly verity this concept. The development emphasis of this product is directed toward the automotive, active robotics, and Global Positioning System markets.
Published in:	Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996) June 19 - 21, 1996 Royal Sonesta Hotel Cambridge, MA
Pages:	621 - 630
Cite this article:	Morrison, Melvin Mark, "How the QUBIK Inertial Measurement Unit Senses Rate," Proceedings of the 52nd Annual Meeting of The Institute of Navigation (1996), Cambridge, MA, June 1996, pp. 621-630.
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