IEEE 528:2019 pdf free download – IEEE Standard for Inertial Sensor Terminology
anisoinertia: (A) (accelerometer) A relationship among the principal axis moments of inertia of anaccelerometer pendulum in which the moment of inertia about the output axis differs from the difference ofthe moments of inertia about the other two principal axes. This inequality causes the effective centers ofmass for angular velocity and for angular acceleration to be physically separated. In a system in which theaccelerometer is modeled as though it were located at the effective center of mass for angular acceleration,there will be an offset in accelerometer output proportional to the product of the angular rates about theinput and pendulous axes.Anisoinertia may be expressed as the magnitude of the actual separation in unitsof length, or as a compensation term expressed as (m/s*)(rad/s) in Sl units.’ Anisoinertia, in this usage,differs from standard physical definitions, but it describes a real effect that is closely analogous to the effectof the same name in gyros. The effect is most easily described in a pendulous accelerometer, but it can alsobe seen in a nominally translational proof mass accelerometer that has sufficient angular elastic complianceto emulate a pendulous axis. (B)(mechanical gyro) The inequality of the moments of inertia about thegimbal principal axes. When the gyro is subjected to angular rates about the input and spin axes, and themoments of inertia about these axes are unequal, a torque is developed about the output axis that isproportional to the difference of the inertias about the input and spin axes multiplied by the product of therates about these two axes.
dynamic time constant: (A)(accelerometer) The delay time between an input ramp and the output aftersteady state is reached. For a second-order system it has a value of twice the damping ratio divided by thenatural frequency in radians/second.(B)(dynamically tuned gyro) The time required for the rotor to movethrough an angle equal to 63% of its final value following a step change in case angular position about anaxis normal to the spin axis with the gyro operating open loop. The value depends on the gimbal and rotordamping and drag forces, and is inversely proportional to quadrature spring rate.
dynamic tuning (dynamically tuned gyro): The adjustment of the gimbal inertia, flexure spring rate, orthe spin rate of a rotor suspension system to achieve a condition in which the dynamically induced(negative) spring rate cancels the spring rate of the flexure suspension.
earth rate: The angular velocity of the earth with respect to inertial space. The WGS-84 magnitude is7.292 115 × 10-5 rad/s (15.041 07°/h).This vector quantity is usually expressed as two components in locallevel coordinates, north (or horizontal) and up (or vertical).
Earth’s rate correction (gyro): A command rate applied to a gyro to compensate for the rotation of theearth with respect to the gyro input axis.
effective center-of-mass for angular acceleration (accelerometer): That point defined by the intersectionof the pendulous axis and an axis parallel to the output axis, about which angular acceleration results in aminimum accelerometer output.
effective center-of-mass for angular velocity (accelerometer): That point defined by the intersection ofthe pendulous axis and an axis of constant angular rate approximately parallel to the input axis, for whichthe offset due to spin becomes independent of orientation. See: spin-offset coefficient.
elastic-restraint coefficient (mechanical gyro): The ratio of gimbal restraining torque about an outputaxis to the output angle.
elastic-restraint drift rate(mechanical gyro): The component of systematic drift rate that is proportionalto the angular displacement of a gyro gimbal about an output axis. The relationship of this component ofdrift ratc to gimbal angle can be stated by means of a coefficient having dimensions of angulardisplacement per unit time per unit angle. This coefficient is equal to the elastic-restraint coefficientdivided by angular momentum.