22,607 research outputs found
Gravitational Effects of Rotating Bodies
We study two type effects of gravitational field on mechanical gyroscopes
(i.e. rotating extended bodies). The first depends on special relativity and
equivalence principle. The second is related to the coupling (i.e. a new force)
between the spins of mechanical gyroscopes, which would violate the equivalent
principle. In order to give a theoretical prediction to the second we suggest a
spin-spin coupling model for two mechanical gyroscopes. An upper limit on the
coupling strength is then determined by using the observed perihelion
precession of the planet's orbits in solar system. We also give predictions
violating the equivalence principle for free-fall gyroscopes .Comment: LaTex, 6 page
Equilibrium properties of the Skylab CMG rotation law
The equilibrium properties of the control moment gyroscopes of the Skylab are discussed. A rotation law is developed to produce gimbal rates which distribute the angular momentum contributions among the control moment gyroscopes to avoid gimbal stop encounters. The implications for gimbal angle management under various angular momentum situations are described. Conditions were obtained for the existence of equilibria and corresponding stability properties
Compensation of Magnetic Disturbances Improves Inertial and Magnetic Sensing of Human Body Segment Orientation
This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error, and magnetic disturbance error are estimated. The filter was tested under quasi-static and dynamic conditions with ferromagnetic materials close to the sensor module. The quasi-static experiments implied static positions and rotations around the three axes. In the dynamic experiments, three-dimensional rotations were performed near a metal tool case. The orientation estimated by the filter was compared with the orientation obtained with an optical reference system Vicon. Results show accurate and drift-free orientation estimates. The compensation results in a significant difference (p<0.01) between the orientation estimates with compensation of magnetic disturbances in comparison to no compensation or only gyroscopes. The average static error was 1.4/spl deg/ (standard deviation 0.4) in the magnetically disturbed experiments. The dynamic error was 2.6/spl deg/ root means square
Topological mechanics of gyroscopic metamaterials
Topological mechanical metamaterials are artificial structures whose unusual
properties are protected very much like their electronic and optical
counterparts. Here, we present an experimental and theoretical study of an
active metamaterial -- comprised of coupled gyroscopes on a lattice -- that
breaks time-reversal symmetry. The vibrational spectrum of these novel
structures displays a sonic gap populated by topologically protected edge modes
which propagate in only one direction and are unaffected by disorder. We
present a mathematical model that explains how the edge mode chirality can be
switched via controlled distortions of the underlying lattice. This effect
allows the direction of the edge current to be determined on demand. We
envision applications of these edges modes to the design of loss-free, one-way,
acoustic waveguides and demonstrate this functionality in experiment
New Upper Limit of Terrestrial Equivalence Principle Test for Rotating Extended Bodies
Improved terrestrial experiment to test the equivalence principle for
rotating extended bodies is presented, and a new upper limit for the violation
of the equivalence principle is obtained at the level of 1.6, which is limited by the friction of the rotating gyroscope. It
means the spin-gravity interaction between the extended bodies has not been
observed at this level.Comment: 4 page
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