Daimler-benz Aerospace Ag

Deutsche Aerospace Ag

Messerschmitt-bolkow-blohm Gmbh

Messerschmitt-bolkow-blohm Gesellschaft MIT Beschrankter Haftung

Messerschmitt-boelkow-blohm Gesellschaft MIT Beschraenkter Haftung

Diamler-benz Aerospace Ag

Michael Surauer

Helmut Bittner

Walter Fichter

Horst-Dieter Fischer

Eveline Gottzein

Rolf Keeve

Ernst Bruederle

Joachim Chemnitz

Oliver Juckenhoefel

Nahit Ertongur

Francois Porte

Christian Roche

Peter Zentgraf

An attitude controller for a 3-axis stabilized, Earth oriented bias momentum spacecraft is described, where only 2-axis attitude measurements from the Earth sensor are available. In contrast to the classical spacecrafts that are controlled w.r.t. a fixed orbital Earth pointing reference frame, (possibly large angle) time varying reference signals are considered here, i.e. the control task consists of a tracking problem. The controller design consists of a decoupling controller and axis-related PID controllers based on yaw observer estimates.

Method for controlling the attitude of a three-axis stabilized, earth

A system for autonomous on-board determination of the position of an earth orbiting satellite consists of a biaxially measuring earth sensor which defines the z-axis (yaw axis) of the satellite and of several biaxially measuring sun sensor measuring heads which are arranged on the satellite structure such that, with the exception of earth shadow phases, they supply a direction vector measurement. Out-of-plane movement of the satellite is propagated by means of a precise model of the satellite dynamics including natural disturbance forces and thrusts during maneuvers on board. In order to compensate sensor uncertainties and the effects of thermal deformations, the satellite orbit is precisely measured at regular intervals (approximately 3 months), and by means of this information, a calibration function (time function for a day) for compensating measured values is determined. The in-plane movement of the satellite is not only propagated, but the propagation is supported by measured data (estimation), and the effects of out-of-plane movement and thermal deformations are taken into account, by means of the data of the calibration function (k(t) or of the propagation out-of-plane movement.

Method and system for the autonomous on-board determination of the

A low earth orbiting satellite control arrangement according to the invention has an earth sensor for measuring roll and pitch of the satellite relative to an earth oriented moving reference system, a spin wheel mounted along an axis perpendicular to the orbital plane of the satellite for measuring spin of the satellite, and two magnet coils for generating control. A first of the two magnet coils is aligned substantially in parallel to a roll axis of the satellite, and the second is aligned substantially parallel to the yaw axis. Alternative control algorithms are disclosed for controlling attitude, nutation and spin of the satellite based on information from the earth sensor, spin wheel and an observer which is also mounted on the satellite.

Earth oriented satellite and process for controlling the position,

In a process and apparatus for controlling the attitude of a spacecraft, drive signals for driving attitude control units of the spacecraft are generated based on control unit signals related to the three principle axes of a spacecraft oriented coordinate system, using the rule k=B.sup.I e+cu.sub.2. The drive matrix B.sup.I, a definite vector u.sub.2 and the constant c result from the application of a matrix decomposition according to the Singular Value Decomposition (SVD) method to a nozzle matrix B. The latter matrix contains as elements, the momentum and force vectors which can be generated by the attitude control units, and the drive matrix B.sup.I is multiplied directly with the vector e derived from the axis-related control unit signals.

Satellite positioning apparatus and process

An arrangement for attitude control and stabilization of a three-axis stabilized, bias momentum spacecraft which is equipped with a spin wheel arrangement that is capable of generating an angular momentum vector in a predeterminable direction, as well as control torques about all three axes of a spacecraft fixed system of coordinates, independently of one another. The control arrangement is equipped with an attitude sensor, which measures the attitude deviation about a first lateral axis (roll axis) oriented perpendicularly to the predetermined direction, with actuators for generating external control torques. A decoupling controller uses the deviations signal (roll angle phi) and takes into account the magnitude of the angular momentum generated by the spin wheel momentum arrangement, to provide a control signal which causes unidirectional decoupling of the roll dynamics from the yaw dynamics, for the spin wheel arrangement for generating a control torque about a second lateral axis (yaw axis) which is orthogonal to the predeterminable direction and to the first lateral axis.

Arrangement for attitude control and stabilization of a three axes

The sun search method for a satellite stabilized in three axes according to the invention uses a sun sensor device with a visual field possibly containing gaps, and a rotational speed gyro which measures in a measuring axis that is oriented arbitrarily. A regulating law with the form .tau.=-kGG.sup.T .omega. is used (.tau.=regulating torque, k=amplification factor, G=directional vector of measuring axis of rotational speed gyro, .omega.=rotational speed vector of the satellite). A rotational wheel momentum H which is not parallel to the measuring axis, is generated with the aid of an additional flywheel device.

Sun search method and apparatus for a satellite stabilized in three axes

Method of adjusting the position of satellites by means of solar

Process and a device for controlling the attitude of a three-axis

Measuring arrangement useful for controlling the attitude of a

Three-axis stabilized, earth-oriented satellite and a corresponding sun

Attitude control process and device for a spacecraft to be rotated

Apparatus for controlling the attitude of and stabilizing an elastic body

A nonlinear frequency domain filter serving for the suppression of unwanted signals which are superposed on a wanted signal variable in a given frequency range. The frequency domain filter comprises linear transmission members and a dead-zone member. With the filter, the zero point of the dead-zone member, to which the input signal to be filtered is supplied, follows proportionally the output signal of a pass-band filter connected in parallel with the dead-zone member. Further, the output signal of the pass-band filter is added to the output signal of the dead-zone member.

Adaptive nonlinear frequency domain filter with low phase loss

Adaptive control system of high accuracy and low corrective energy

An arrangement for the attitude stabilization of flexible vehicles, such as ircraft and spacecraft. Such vehicles, due to their lightweight construction and/or large spatial extension or high degree of slenderness, have structurally weakly-dampened bending vibrations and/or torsional vibrations. For generating the forces and moments required for stabilizing such vehicle, discontinuously operating units are used. In one embodiment, for each vehicle axis, an observer or Kalman filter is employed for obtaining estimated values of the state variables of the vehicle system to be controlled. The observer has a first transfer function of at most third order. A state controller device is responsive to the observer for controlling the state variables. A modulator network is responsive to the state controller device wherein the modulator network has a relay characteristic. In this embodiment, a feedback path is arranged from the output of the modulator network to the observer which eliminates the need for a special modulator network having a second transfer function and also eliminates internal modulator feedback. In another form of the invention, the feedback is arranged from the input of the modulator to the observer and a low pass filter is included between the state controller device and the modulator network. The filter has either at least two low pass filter sections of first order or a single low pass filter section of at least second order. The break-point frequencies of the filter section or sections lies between the natural frequency of the rigid body and the lower structural resident frequency of the respective vehicle axis. Equivalent circuits are disclosed for replacing the observer and state controller device as described above. Adaptive techniques as well as digital realizations of the various embodiments are also disclosed.

Arrangement for the attitude stabilization of flexible vehicles with

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Chieming, Germany

Michael Surauer