The invariant control of the vehicle descent into the atmosphere
Abstract
The problem of the nonlinear control synthesis of vehicle descent is formulated as the task of finding a law for attack and bank angle modulation to correct perturbations occurring during descent. A control algorithm which solves the terminal control problem for 3-d descent is synthesized with the help of the invariancy theory, taking altitude and crossrange at a given down range as motion invariants. The invariancy conditions allow expression of the relationship between control and state coordinates and the measured G-factor components in analytical form, and permit compensation for the effects of variations in aerodynamic and weight characteristics, atmospheric density, and wind, and for deviations in initial descent conditions without knowledge of their statistical properties. Testing of the algorithm by computer simulation of vehicle descent (hypersonic lift drag ratio:2.5) shows that the control law is highly accurate over a broad range of initial states, and can be used with an on-board computer having a 200 word working memory, 2000 word permanent memory, and a running speed of 4000 single address operations/sec.
- Publication:
-
Lisbon International Astronautical Federation Congress
- Pub Date:
- September 1975
- Bibcode:
- 1975lisb.iafcQ....K
- Keywords:
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- Algorithms;
- Atmospheric Entry;
- Computerized Simulation;
- Control Simulation;
- Descent Trajectories;
- Spacecraft Control;
- Aerodynamic Characteristics;
- Airborne/Spaceborne Computers;
- Gravitational Effects;
- Invariance;
- Meteorological Parameters;
- Trajectory Control;
- Astrodynamics