In-Flight Estimation of Satellite Mass Properties and Calibration Parameters for Actuators
Michael Rososhansky and Philip Ferguson, Department of Mechanical Engineering, University of Manitoba, MB, Canada.
Location: Pavilion Ballroom East
Alternate Number 1
A common cost driver for many satellites missions is the cost associated with calibrating and characterising the onboard actuators and the cost associated with on-ground mass properties measurements. Typically, the actuator torque errors are indistinguishable from the inertia errors about the wheel axis and all applied torque errors will be interpreted as inertia errors. Therefore, actuator torque errors will be compensated by adjusting the inertia tensor as opposed to being compensated by actuator alignment. The purpose of the research is to develop an algorithm that may reduce or eliminate the tedious and time consuming on-ground mass properties measurements and actuator calibration procedures. The estimation parameters of interest include the torque scale factors and the moment-of-inertia (MOI) tensor. The mass properties estimations require a rudimentary initial estimates of the moment-of-inertia tensor to be provided to the control algorithm for initial coarse navigation, while a sequential estimate of the MOI will be available to the controller for fine navigation in-orbit flight. The contribution of this research is the capacity to estimate concurrently the reaction wheel scale-factors and MOI tensor by exploiting the null space provided by a redundant actuator. The proposed algorithm is applied to a satellite with a cluster of four reaction wheels for actuation activities, four gyroscopes for computing angular rate, and at least one star-tracker for attitude.