Process and a device for controlling the attitude of a three-axis stabilized spinning spacecraft
First Claim
1. A process for controlling the attitude of a three-axis stabilized, spacecraft having a stored spin to maintain a spin direction of the spacecraft in inertial space and limit a nutation amplitude of the spacecraft while using at least one dead zone element, comprising:
- continuously checking to determine if predetermined threshold values for deviation of the spin direction from a desired orientation and for nutation amplitude are exceeded using separate dead zone elements to define each of the predetermined threshold value; and
triggering control interventions, only for reduction of nutation, even when the spinning direction is within a range limited by the predetermined threshold values.
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Accused Products
Abstract
The invention provides an improved process and apparatus for controlling the attitude of a three-axis stabilized spacecraft. Separate dead zone elements are used to define threshold values for limiting nutation amplitude and deviation of the spin direction of the spacecraft from a desired orientation, and a continuous check is performed to determine whether the nutation amplitude and deviation of the spacecraft exceed the threshold values. A control intervention is initiated to reduce the nutation, even when the spin direction is within the range limited by the applicable threshold value.
11 Citations
4 Claims
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1. A process for controlling the attitude of a three-axis stabilized, spacecraft having a stored spin to maintain a spin direction of the spacecraft in inertial space and limit a nutation amplitude of the spacecraft while using at least one dead zone element, comprising:
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continuously checking to determine if predetermined threshold values for deviation of the spin direction from a desired orientation and for nutation amplitude are exceeded using separate dead zone elements to define each of the predetermined threshold value; and triggering control interventions, only for reduction of nutation, even when the spinning direction is within a range limited by the predetermined threshold values.
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2. A process for controlling the attitude of a spacecraft having a stored spin which is three-axis stabilized with respect to a presettable desired attitude and is equipped with actuators for generating controlling torques about two lateral axes which are orthogonal with respect to the direction of the stored spin as well as with respect to one another, comprising:
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obtaining by at least one attitude sensor, an angular deviation signal which represents an angular deviation of the spacecraft about one of the two lateral axes with respect to the desired attitude; forming a first and second signal fractions from the angular deviation signal, the first signal fraction being representative of an orbital movement of the spacecraft, the second signal fraction being representative of a nutation movement of the spacecraft; obtaining from the first signal fraction an input signal for a first dead zone element, the first dead zone element having an output signal; obtaining from the second signal fraction signals which represent the nutation amplitude and the nutation phase of the spacecraft; providing the signals representing the nutation amplitude and the nutation phase, and the output signal of the first dead zone element, as inputs to a nutation controller which determines points in time for triggering control interventions by the actuators; additionally providing the signal representing the nutation amplitude to a second dead zone element that has a threshold value selected according to a presettable highest permissible value for the nutation amplitude, the second dead zone element having an output signal received by the nutation controller and taken into account by the nutation controller for determining a necessity of an additional control intervention.
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3. A device for controlling the attitude of a spacecraft having a stored spin which is three-axis stabilized with respect to a presettable desired position, comprising:
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at least one attitude sensor for measuring an angular deviation from a desired attitude of the spacecraft about at least one of two lateral axes of the spacecraft that are orthogonal with respect to a direction of the stored spin as well as with respect to one another, the attitude sensor producing an angular deviation signal; actuators for generating control torques about the two lateral axes; a controller network coupled to the attitude sensor, the controller network receiving the angular deviation signal and generating therefrom a first signal fraction which represents orbital movement of the spacecraft; a first device coupled to the attitude sensor and which produces from the angular deviation signal a second signal fraction which represents nutation movement of the spacecraft; a spin controller coupled to the controller network and which receives the first signal fraction; a first dead zone element connected to an output of the spin controller; a second device coupled to the first device, the second device producing from the second signal fraction a signal that represents a nutation amplitude and a signal that represents a nutation phase of the spacecraft; a nutation controller connected to an output of the second device, an output of the first dead zone element, and the actuators, the nutation controller determining points in time for triggering generation of the control torques; and a second dead zone element coupled to the nutation controller and to an output of the second device, the second dead zone element receiving the signal representing the nutation amplitude and emitting an output signal to the nutation controller.
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4. A process for controlling attitude of a three axis stabilized spacecraft, to maintain a spin direction of said spacecraft, said process comprising the steps of:
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defining a first threshold value for limiting deviation of a spin direction of said spacecraft from a desired orientation, by means of a first dead zone element; defining a second threshold value for limiting nutation amplitude for said spacecraft, by means of a second dead zone element, detecting magnitudes of said deviation and of said mutation; continuously checking to determine if detected magnitude of said deviation and detected nutation amplitude exceed said first and second threshold values, respectively; and triggering a control intervention to reduce said nutation based on a result of said checking step, even when the spin direction is within a range limited by said first threshold value.
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Specification