Imbalance Estimation and Compensation in a Rotating Rigid Body

Paper number

IAC-07-C1.2.06

Author

Dr. Takeya Shima, Mitsubishi Electric Corporation, Japan

Coauthor

Dr. Katsuhiko Yamada, Nagoya University, Japan

Coauthor

Dr. Shoji Yoshikawa, Mitsubishi Electric Corporation, Japan

Year

2007

Abstract

Key instruments on the Advanced Earth Observing Satellite-II (ADEOS-II) and the Aqua satellite launched in 2002 include an Advanced Microwave Scanning Radiometer (AMSR) and an Advanced Microwave Scanning Radiometer-EOS (AMSR-E). These instruments continuously rotate around an axis parallel to the satellite at a constant speed and observe the Earth’s surface by conical scanning. Disturbance torque due to an imbalance in the instrument will cause undesirable vibration in the satellite attitude. 

This paper presents an approach for on-orbit imbalance estimation and compensation in such a rotating rigid body on a satellite. It estimates the static and dynamic imbalance parameters from flight data and drives counterweights on the rotating body to minimize the effects of imbalance. We present two imbalance estimators based on the least squares approach. One utilizes the relation of the total angular momentum conservation, and the other utilizes the frequency response of the satellite angular velocity to the disturbance torque. By using estimates of the imbalance parameters the positions of the counterweights are calculated and commanded. 

Analysis and simulation results are presented to verify this approach. An angular momentum based estimator is applicable to cases where the satellite is regarded as a rigid system. However, this method is not applicable to satellites with large flexible appendages such as a solar array paddle, because the effect of disturbance torque due to imbalance is transferred to the flexible appendages, complicating utilization of the relation of the total angular momentum conservation. In this case, a frequency response based estimator is applicable. The influence on flexibility depends on the rotational speed of the body because the magnitude of the disturbance torque is proportional to the square of that speed. Simulation results show that a frequency response based estimator produces accurate estimates of imbalance parameters regardless of the body’s rotational speed. 

In summary, this paper presents a new approach for on-orbit imbalance estimation and compensation in a rotating rigid body on a satellite. It enables us to effectively correct static and dynamic imbalance and to minimize the effects of imbalance. Consequently, it will be useful in future satellite missions when highly stable pointing is required.

Abstract document

IAC-07-C1.2.06.pdf

Manuscript document

IAC-07-C1.2.06.pdf (🔒 authorized access only).

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