Library of Congress Cataloging-in-Publication Data Merhav, Shmuel.Aerospace sensor systems and applications / Shmuel Merhav. p. cm. Includes bibliographical references and index.

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This paper describes a concept of a low-cost gyroless inertial measurement unit. By means of an orthogonal triad of rotating or vibrating accelerometers, angular rates are measured along with specific forces. The precise separation of the two signals from the accelerometer readings is described. Apart from its simplicity, the special features of the separation method are that signal bandwidth is not sacrified, inertial angular rate measurements are essentially drift-free, and dynamical errors due to angular rate and specific force derivatives are reduced to negligible values. A detailed statistical analysis of the error sources, due to dynamical effects, sampling, nonlinearities, and vibration is given. The residual angular rate offset is due to the electronic processor which, with modern CMOS components, is shown to provide a performance level in the 1 n.mi./h class. The possibility of dispensing with the costly gyroscopes, which are essential in conventional designs, indicates a substantial saving in cost. Nomenclaturea = vector of accelerometer outputs a = bandwidth of random process b = index of body axes c = index of coherent terms F = vector of specific forces applied to vehicle g = gravity vector h (t) = impulse response / = index of coordinates x,y, z I = distance vector m = ratio of frequencies n = vector of measurement noise o = index of orthogonal terms p, q, r -components of angular rate R E -radius of Earth R = position error / = time T = period of cycle u = normalized distance function V = vibration amplitude X, Y, Z = rectangular coordinate system a = bandwidth normalized to Schuler frequency co 5 f = normalized time f=co 5 / \L = beat frequency v = vibration frequency T = time difference p = radius of rotation or amplitude of vibration a = standard deviation (•) = autocorrelation function $ (•)= power density spectrum $* (*) = power density spectrum of sampled signal co = frequency of revolution co 5 = Schuler frequency ft = angular rate vector of body axis system Q,.= component of angular rate error

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