Characteristic modeling and attitude control for small satellite via variable inertial reaction wheel
With the functional diversification of modern small satellite, new requirements that large range maneuver, high precision control are proposed. Variable inertia reaction wheel (VIRW) is expected to become the mainstream e actuator for attitude control of a new generation small satellite because of the characteristics of high-resolution and large range of torque. First of all, based on the traditional reaction wheel kinetic model, the kinetic model of small satellite control system via the three-axis orthogonal VIRW is deduced, where, the moment of inertia is treated as the variable. Secondly, the change rate of rotational inertia and the angular acceleration of rotational speed of the VIRW are chosen as state variables. And the attitude angles of the satellite are chose as output. And then the feature model of the control system is established. On this basis, the nonlinear golden section control law is designed and the control system of the small satellite with the three-axis orthogonal VIRW is simulated using Matlab. The simulation results show that the control system is stable with good transition, great anti-interference performance, and without stead-error. And it can meet the requirements of the large range attitude mobility and tracking maneuvering target.
An Introduction to the Variable Inertia Flywheel (VIF)
A flywheel with variable moment of inertia, combining the functions of energy storage and power control is introduced. Potential designs are presented and the basic physical governing equations developed. Examples of the flywheel system powering a constant angular rate, frictional load, and an accelerating automobile are presented. Limitations of and potential for future development which become evident in the examples are discussed.
Thermal stability of reconstituted collagen fibrils. Shrinkage characteristics upon in vitro maturation
Thermal stability measured as area shrinkage without tension during heating was determined for membranes of collagen fibrils reconstituted from solutions of highly purified rat skin collagens. Shrinkage in per cent of area at 25 degrees C and shrinkage temperature were quantitated in a standardized way and determined as a function of in vitro maturation time for 11 to 104 days after aggregation for the collagen membranes. Similar to reports on intact rat skin, shrinkage temperature remained constant and shrinkage per cent declined with a rate decreasing with time during maturation. Solubility in water at 80 degrees C for 2 hours was 95-96% and remained unchanged for the maturation time (about 2 months) studied. The decreased shrinkage reflecting a lower degree of collapse is ascribed to an increasing thermal stability of the membranes during maturation. Development of heat-stable bonds in the reconstituted collagen fibrils is taken up to be amenable to this increased stability. Similarity in changes of shrinkage characteristics during in vivo and in vitro maturation indicates that maturation changes in reconstituted collagen fibrils reflect those occurring in intact collagen during in vivo aging.