Yasuhiro Morita

This paper deals with the post flight analysis on the attitude control problem of the M-3SII-8/EXPRESS flight, which occurred at the midcourse of its second stage powered phase. The results of the post-flight modal analysis, executed for the second stage entire vehicles of the M-3SII series, shows peculiarity of the EXPRESS flight in structure and control interactions of the vehicle. The loop gain from the control command to the first order bending oscillation of the vehicle, indicating the extent of the flexibility effect, is definitely enhanced compared with those of the previous flights, which combined with the instability of the mode to yield the dynamical coupling between the structural oscillation of the degree and the attitude control. An increase in the payload mass compared to the rest of the flights is considered a principal contribution to the difference in modal characteristics. The mechanism of the growth of the oscillation amplitude, even within the control dead band, is also mathematically disclosed, which is featured by the magnitude of the disturbance. A transition from the disturbance governed (dynamic) cycle into a static cycle triggered the resonance type phenomenon. The static limit cycle, which happened to be formed in the middle of the second stage flight, caused the frequent and long durational injections, resulting in the excess energy supply into the oscillating system. Thus the magnitude of the oscillation gradually increased to finally exceed the control dead band, leading to a divergence type response. The numerical simulation has been conducted under the system parameters evaluated through the flight data and given its endorsement to all the point. The paper also describes an effective measure to avoid the problem.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continua and their flexural deformations are represented by a series of admissible functions. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Application of the general formulation, illustrated through several typical MRMS configurations of practical importance, reveals complex interactions between vibrational and librational degrees of freedom, in the presence of MRMS maneuver, over a range of system parameters and initial conditions. Effectiveness of the formulation is also demonstrated through another illustrative example of the SCOLE configuration representing the Shuttle based flexible beam supporting a rigid reflector plate at its end.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continuum and their flexural deformations represented by a series of admissible functions. The highly nonlinear, nonautonomous and coupled equations of motion, being not amenable to any known closed-form solution, are solved numerically. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Next, effectiveness of the general formulation is illustrated by studying complex interactions between vibrational and librational degrees of freedom in the presence of MRMS maneuver over a range of system parameters and initial conditions. The problem is purposely approached in an increasing order of complexity to gain physical appreciation of the system response. To that end the MRMS is replaced by a single arm. To start with a parametric study of a rigid platform supporting a rigid arm is carried out followed by a progressive introduction of the platform and arm flexibility. Finally, the general case of the Eulerian beam type platform with a flexible slewing and translating arm lays a foundation for studying more complex configurations which the formulation is designed to tackle. Results suggest that the MRMS maneuver can affect librational and vibrational response substantially and under critical combinations of parameters the system can become unstable. The information is fundamental to the design of a control strategy which, for a flexible system in the presence of generalized forces, has received virtually no attention. The thesis ends with a set of recommendations for future course of study which is likely to be innovative, useful and satisfying.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continuum and their flexural deformations represented by a series of admissible functions. The highly nonlinear, nonautonomous and coupled equations of motion, being not amenable to any known closed-form solution, are solved numerically. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Next, effectiveness of the general formulation is illustrated by studying complex interactions between vibrational and librational degrees of freedom in the presence of MRMS maneuver over a range of system parameters and initial conditions. The problem is purposely approached in an increasing order of complexity to gain physical appreciation of the system response. To that end the MRMS is replaced by a single arm. To start with a parametric study of a rigid platform supporting a rigid arm is carried out followed by a progressive introduction of the platform and arm flexibility. Finally, the general case of the Eulerian beam type platform with a flexible slewing and translating arm lays a foundation for studying more complex configurations which the formulation is designed to tackle. Results suggest that the MRMS maneuver can affect librational and vibrational response substantially and under critical combinations of parameters the system can become unstable. The information is fundamental to the design of a control strategy which, for a flexible system in the presence of generalized forces, has received virtually no attention. The thesis ends with a set of recommendations for future course of study which is likely to be innovative, useful and satisfying.