Engineering topics

Bergmann, Edward V.

Publications and source records attributed to Bergmann, Edward V..

5 records

NASA NTRS1991

Collision detection for spacecraft proximity operations

A new collision detection algorithm has been developed for use when two spacecraft are operating in the same vicinity. The two spacecraft are modeled as unions of convex polyhedra, where the resulting polyhedron many be either convex or nonconvex. The relative motion of the two spacecraft is assumed to be such that one vehicle is moving with constant linear and angular velocity with respect to the other. Contacts between the vertices, faces, and edges of the polyhedra representing the two spacecraft are shown to occur when the value of one or more of a set of functions is zero. The collision detection algorithm is then formulated as a search for the zeros (roots) of these functions. Special properties of the functions for the assumed relative trajectory are exploited to expedite the zero search. The new algorithm is the first algorithm that can solve the collision detection problem exactly for relative motion with constant angular velocity. This is a significant improvement over models of rotational motion used in previous collision detection algorithms.

Vaughan, Robin M.↗

NASA NTRS1990

Steering law design for redundant single-gimbal control moment gyroscopes

Two steering laws are presented for single-gimbal control moment gyroscopes. An approach using the Moore-Penrose pseudoinverse with a nondirectional null-motion algorithm is shown by example to avoid internal singularities for unidirectional torque commands, for which existing algorithms fail. Because this is still a tangent-based approach, however, singularity avoidance cannot be guaranteed. The singularity robust inverse is introduced as an alternative to the pseudoinverse for computing torque-producing gimbal rates near singular states. This approach, coupled with the nondirectional null algorithm, is shown by example to provide better steering law performance by allowing torque errors to be produced in the vicinity of singular states.

Bedrossian, Nazareth S.↗

NASA NTRS1990

Redundant single gimbal control moment gyroscope singularity analysis

The robotic manipulator is proposed as the mechanical analog to single gimbal control moment gyroscope systems, and it is shown that both systems share similar difficulties with singular configurations. This analogy is used to group gimbal angles corresponding to any momentum state into different families. The singularity problem associated with these systems is examined in detail. In particular, a method is presented to test for the possibility of nontorque-producing gimbal motion at a singular configuration, as well as to determine the admissible motions in the case when this is possible. Sufficient conditions are derived for instances where the singular system can be reconfigured into a nonsingular state by these nontorque-producing motions.

Bedrossian, Nazareth S.↗

NASA NTRS1989

In flight demonstration of mass property identification and jet plume interaction on the AeroAssist Flight Experiment

Algorithms have been developed for in-flight demonstration of spacecraft mass, center of mass, and inertia matrix which autonomously measure mass properties as they change in-flight due to consumable expenditures, payload deployment/retrieval, and docking. The testing of these algorithms can be conducted by means of a mass-properties estimator, which is a second-order nonlinear filter resembling an extended Kalman filter. The AeroAssist Flight Experiment, which will demonstrate the use of the earth's atmosphere to assist orbital changes, will carry the Rarefied-flow Aerodynamic Measurement Experiment (RAME); data taken by RAME will be used by the mass-properties estimator to ascertain spacecraft mass properties, and estimates from this filter will be compared to predicted values of the mass properties to validate the estimator.

Bergmann, Edward V.↗

NASA NTRS1988

Interaction of the Space Shuttle on-orbit autopilot with tether dynamics

The effect of Orbiter flight control on tether dynamics is studied by simulation. Open-loop effects of Orbiter jet firing on tether dynamics are shown, and the potential for closed-loop interaction between tether dynamics and Orbiter flight control is determined. The significance of these effects on Orbiter flight control and tether control is assessed.

Bergmann, Edward V.↗