Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A method for adjusting the orientation and for compensating interfering torques via solar pressure torques for a satellite moving on an orbit around the earth. The satellite has two solar generators arranged symmetrically on opposite sides of a main body of the satellite. The two solar generators are rotatable independently of one another via servomotors about a first axis of rotation orthogonal to an orbiting plane of the satellite when the position of the satellite is correct. The method comprises the step of: optionally generating solar pressure torques about at least one of three space axes oriented orthogonally with respect to one another, as a result of an adjustment of the solar generators by a targeted rotation about second axes of rotation orthogonal to the first axis of rotation or about the first axis and the second axes of rotation, with respect to a nominal orientation in which the solar generator's normals to surfaces are precisely aligned in the direction of the sun.

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.

Abstract: A measurement arrangement is useful for controlling the attitude of a three-axis stabilized satellite equipped with sun-sensors for determining the orientation of the sun (sun vector) with respect to a satellite-fixed coordinate system, as well as with speed gyroscopes for detecting components of the satellite speed of rotation vector .omega.. It is necessary that the measurement range of the sun-sensors cover the round angle in a preselectable plane (for example XY plane) and perpendicularly thereto a limited angular range of maximum .+-..alpha..sub.2max on both sides of the plane. In addition, only an integrating speed gyroscope carrying out measurements in a single measurement axis that encloses with the plane an angle of at least (.pi./2)-.alpha..sub.2max should be provided.

Abstract: A three-axis stabilized, earth-oriented satellite has an attitude control system with regulators, actuators, an earth sensor that carries out measurements along two axes and a sun-sensor arrangement that also carries out measurements along two axes. The field of view of the sun-sensor arrangement covers the round angle on a plane of the satellite-fixed coordinate system. Only the sun-sensor arrangement and the earth sensor act as measurement transducers. A sun and earth acquisition process for such a satellite has the following steps: seeking the sun; setting the sun vector in a first direction of reference; setting the speed of rotation of the satellite around the sun vector at a constant value; setting the sun vector in a second direction of reference, so that by rotating the satellite around the latter the optical axis of the earth sensor sweeps over the earth; and picking up the earth. Special regulating rules are disclosed.

Abstract: This device is used for controlling the attitude of a spacecraft to be rotated about a body's axis of rotation. Actuators generate torques about the axis of rotation and two lateral axes. Angular velocity signals .omega..sub.X, .omega..sub.Y with respect to the lateral axes are in each case fed to first and second signal paths. The latter contain an integrator. Modulators, which each comprise a variable dead zone, supply control signals for the actuators. In order to limit the nutation amplitude to a constant value in a reliable manner, multiplication elements are provided in the first and second signal paths. The lateral-axis angular velocity signals .omega..sub.X, .omega..sub.Y or the angular position signals .PHI., .theta. are acted upon by factors which are proportional to the rotation axis angular velocity signal .omega..sub.Z or its square in the multiplication elements. Furthermore, the thresholds of the dead zones of the modulators are varied proportionally to .omega..sub.Z.sup.2.

Abstract: A device is disclosed for regulating a set value and/or for stabilizing elastic objects subject to spin and free to move around their axis of rotation, in particular aircraft and spacecraft. For that purpose, the regulating signals required to regulate the set value or to stabilize the freely moving objects can be obtained by means of a regulator having a transfer function with a denominator degree about three orders higher than the numerator.

Abstract: 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.

Abstract: A control system having a main loop comprising a deadband section having iable thresholds. An adaptive network derives from a deviation signal, in one or more selected frequency ranges, by averaging, an adaptive signal which when injected into the deadband section allows its thresholds to be continuously or discretely adjusted in accordance with a desired function to increase the accuracy and reduce the corrective energy consumption of the control system.

Abstract: 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.

Abstract: The air gap between the rail or rails and an electromagnetically levitated ehicle is optimally controlled with regard to the power or energy consumption. This result is achieved by a control employing two control channels. One control channel is constructed as a non-linear support or guide controller for regulating or contolling the air gap width in response to disturbances of short duration. The other control channel is constructed to cause a reduction of the air gap width or rather of the rated air gap width for adapting of the air gap width to the spectrum and amplitude distribution of the disturbances to which the levitated vehicle is exposed. This type of control may be employed for the regulating of the air gap between the support magnets and the respective rail and also for controlling the air gap between the guide magnet and the respective rail to reduce the energy required for maintaining these air gaps at an optimally efficient width.