Showing papers on "Yaw published in 1969"

Dampened railway car truck

Abstract: This invention relates to a railway vehicle suspension in which the vehicle is supported on wheelsets or double axle bogies by way of a yaw suspension which allows relative yawing movements between the vehicle and the wheelsets or bogies. This yaw suspension includes a resilient arrangement, such as a seriesconnected damper and spring, whose dynamic stiffness increases with increase in the yaw velocity. In this way any high frequency yawing movements, such as are caused by track irregularities, are quickly damped out.

Bounds on the librations of parametrically resonant satellites.

Abstract: The objective of this study is the determination and portrayal of the bounds of rotational motion of satellites previously shown to exhibit parametric resonance when performing small librations in the orbital plane. Attention is restricted to the behavior of rigid satellites in circular orbit in an inverse square field, ignoring translation/rotation coupling and truncating the gravitational potential expansion in terms of the ratio (satellite dimension/orbital radius) to retain only first-approximation torque expressions. Generalized coordinates are defined to describe the deviation of the satellite principal axes from the orbital-frame axes. The dynamic potential energy is constructed as that portion of the resulting Hamiltonian free of the generalized velocities, and its equipotential surfaces are noted for corresponding initial conditions to constitute zero angular velocity surfaces for motion relative to the orbiting frame. Bounds on libration so constructed are portrayed as families of curves on a unit sphere in the orbiting frame. The results display clearly that the resonance and instability described in previous publications will in most circumstances be quite innocuous, and may even be desirable. Instability is manifested almost entirely in "yaw," resulting in little deviation from nominal orientation of the satellite earth-pointing axis, so that cameras, antennas, and such earth-pointing equipment can continue to function. Furthermore, it appears to be feasible to exploit the parametric resonance with a damping device responsive to yaw rotation, and in this manner to accelerate satellite libration attenuation.