Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B64—AIRCRAFT; AVIATION; COSMONAUTICS
  • B64G—COSMONAUTICS; VEHICLES OR EQUIPMENT THEREFOR
  • B64G1/00—Cosmonautic vehicles
  • B64G1/22—Parts of, or equipment specially adapted for fitting in or to, cosmonautic vehicles
  • B64G1/24—Guiding or controlling apparatus, e.g. for attitude control
  • B64G1/244—Spacecraft control systems

Definitions

• the present invention relates to methods and devices for controlling the attitude of a satellite by controlling the orientation of the direction of the axis of rotation of the router of gyroscopic actuators, or gyrodynes, of a cluster of gyroscopic actuators. mounted in the satellite.
• Gyrodynes or gyroscopic actuators (often designated by the acronym cmg) have a wheel or top mounted on a support, called cardan, orientable on the platform of the satellite by a motor around at least one axis orthogonal to the axis of rotation of the router.
• cmg a support
• An example of a control moment gyro is given in French patent application No. 98 00556 c to which reference may be made.
• a gyrodyne cluster includes at least three gyrodynes to allow bringing a reference trihedron linked to the satellite in all attitudes and at least two gyrodynes for 2-axis control. In general, at least four gyrodynes are used to provide redundancy.
• the gyrodyne cluster constitutes an inertial actuator whose control makes it possible to apply a torque giving the satellite platform a profile of angular velocities which is specified by downloading from the ground or by a calculation carried out on board.
• a control system determines the torque to be applied and deduces a speed to apply to the gimbals of the gyrodynes.
• the capacity to supply the total torque C is therefore non-stationary and non-linear. It can be written, in matrix form:
• a classic method of guidance consists, knowing the torque C to be supplied, to invert relation (1) to obtain the set speeds ⁇ c to be given to the gyrodynes. The principle of such control is for example given in the document FR already mentioned or the patent US-A-6,131,056.
• the architecture described in patent application No. 98 14548 for this includes a cluster of at least four gyrodynes having respective routers mounted on gimbals rotatably mounted on a platform of the satellite, around axes of orientation of all different gimbals.
• This configuration has the advantage of principle of having a maximum isotropy when the four cardan axes are directed along the diagonals of a cube.
• the pyramidal architecture has various disadvantages.
• the capacity envelope has concativities; it is not possible, in the case of a flattened pyramid, to adjust the capacities independently along the two axes of the base of the pyramid.
• a satellite having a cluster of at least four gyroscopic actuators having respective rotors mounted on universal joints orientable around axes parallel to one or the other of only two different directions and fixed with respect to the satellite, and to adopt an original piloting process to avoid coming in singular configurations when piloting attitude.
• the invention proposes a method for controlling the attitude of such a satellite, according to which: the attitude of the satellite is measured using sensors on board the satellite,
• a local linearization calculation is carried out based on the pseudo- inversion of the Jacobian matrix of the function linking the orientations of the cardan shafts of the actuators to the total kinetic moment of the cluster in order to determine a new orientation of the cardan shafts, and
• Precession speeds are controlled from at least one of the cardan shafts of the actuators supplying the control torque to arrive at the desired configuration, characterized in that the calculation is carried out by applying a search constraint for remote cluster configuration singular configurations by distribution, between the two groups of actuators, of the component of the total angular momentum of the cluster which is perpendicular both to one and to the other of the two said directions.
• the criterion of distance from a configuration of cardanic angles in the cluster relative to a singular configuration is adopted, the product of two simpler criteria applying separately to each of the two groups. actuators.
• the criterion of distance between a configuration of angles of cardan and a singular configuration be a criterion chosen as: canceling out when the angle between the two angular momentum vectors carried by the two actuators is zero or flat, and - reaching a maximum when the angle between the two angular momentum vectors carried by the two actuators is close to 90 °.
• the search for a final configuration far from the singularities can make it possible to establish a tabulation of the correspondences between the different kinetic moments of cluster necessary for the different maneuvers of the satellite and the respective optimal cluster configurations associated.
• the search for a final configuration far from the singularities provides directly and analytically an optimal cluster configuration fulfilling the request for the kinetic moment of cluster necessary for the maneuver of the satellite.
• the criterion of distance between a configuration of cardan angles and a singular configuration can be defined so as to cancel out when one angles formed each time by two of the three angular momentum vectors carried by the three actuators is zero and so as to reach its maximum when these angles are close to 120 °.
• a search is made for a final configuration distant from the singularities as soon as it is detected that the distance between the current configuration and the associated singularity becomes less than a predetermined threshold.
• the search for a final configuration distant from the singularities can be implemented in advance, starting from the prior knowledge of the trajectory of kinetic moment of cluster necessary for the change of orientation of the satellite and the trajectory obtained is then used as preferred trajectory, sent in open loop as part of an attitude control method associating a open-loop control to closed-loop control of the FR request already mentioned.
• the invention also makes it possible to carry out guidance according to a memorized law.
• the method is implemented in advance from the prior knowledge of the maneuver to be performed and the maneuver d attitude of the satellite using the trajectory obtained in open loop in an attitude control associating an open loop command with a closed loop command ensuring the arrival of the satellite in the desired final attitude.
• the invention also provides an attitude control device for implementing the above method, comprising: a cluster of at least four gyroscopic actuators having respective routers mounted on universal joints orientable around axes parallel to the one or the other of only two different directions and fixed with respect to the satellite, thus forming two groups of actuators, one of which at least two actuators each,
• - calculation means for calculating the need for control torque to fill a satellite attitude setpoint, and for determining means for controlling the precession speeds of the gimbals producing the control torque through a local linearization method based on the pseudo-inversion of the Jacobian matrix of the function binding the orientations.
• FIG. 1 is a perspective diagram showing a possible arrangement of four 1-axis gyroscopic actuators of a cluster using an advantageous architecture, the actuators being shown with identical gimbal orientations;
• FIG. 2 is a diagram showing the parameters involved in the analytical calculation of the possible correspondences between the desired angular momentum H and the angular positions ⁇ of the cardan joints;
• FIG. 3 is a diagram showing the parameters involved in the analytical calculation in the event of loss of redundancy due to the failure of an actuator.
• Figure 1 shows a cluster of four gyroscopic actuators 10a, 10b, 10c, 10d identical, each having a router 12 mounted on a gimbal 14 so as to be able to rotate around a respective axis 16.
• a motor not shown keeps the router in rotation, usually at constant speed.
• Each gimbal is mounted on the satellite platform (not shown) so as to be able to rotate around an axis 18 orthogonal to the axis 16.
• Each of the gimbals is provided with a motor 22 making it possible to rotate the dial around of the respective axis 18.
• An angular sensor such as 23 gives information on the orientation of the gimbal and therefore of the plan of the router 12. Maintaining the satellite in a set attitude in an inertial frame is ensured by an attitude control system having a constitution general which may be of a known type.
• the system comprises a calculation and control unit 26 which stores orientation instructions received by a ground transceiver 28 and receives signals 30 from orientation sensors, such as star sensors and of terrestrial horizon.
• This member 26 controls the power circuits 32 supplying the motors 22.
• This system generally has a relatively long time constant, from a few seconds to several tens of seconds.
• the axes 18 have one or the other of only two different orientations.
• the axes of the gimbals of the actuators 10a and 10b are arranged perpendicularly to the same plane PI.
• the axes of the cardan shafts of the actuators 10c and lOd are also parallel to each other and arranged perpendicularly to a plane P2 which intercepts the plane PI along the x axis.
• the planes Pi and P2 both make an angle ⁇ with the axis y.
• the global angular momentum of the cluster of actuators will be designated subsequently by H and the components of H in the planes PI and P2 respectively by Hl and H2 ul and u2 denote the axes perpendicular to x contained respectively in the planes PI and P2 .
• the configuration of actuators shown in FIG. 1 (as well as any other configuration of actuators in which the axes of the universal joints are two to two parallel), has the advantage of making it possible to express analytically the correspondence between the angular momentum H and the angular positions 1, 2, 3 and 4 of the universal joints, for example expressed with respect to the arrangement shown in FIG. 1.
• the architecture adopted makes it possible to share the Hx component between the two pairs of actuators lOa-lOb and lOc-lOd with a degree of freedom, except on the surface of kinetic moment, where it presents a singularity.
• the two universal joints of the plane PI are arranged symmetrically on either side of the direction of the angular momentum Hl, making an angle 1 with this direction, such that:
• Hx2 [(1- ⁇ ) (Hx)] ⁇ being a weighting coefficient chosen at will.
• the choice is made by looking for the cluster configuration which is distant from the singular configurations, by adopting as criterion one of those indicated above.
• An additional advantage of the configuration is that the geometry remains simple in the event of a failure of one of the actuators, which makes it possible to maintain an attitude control capacity and only slightly degrade the agility (by 25% around the 'x axis).
• the healthy actuator in the PI plane has an angular orientation which is imposed by the moment demand Hul, the decomposition of H along the axes ul and u2 being unique.
• the loss of agility on the x axis whose capacity is maximum, amounts to going from 4h to 3h. According to one of the u axes, the maximum loss of agility is 50%. But, very often, the axis along which the agility requirements are strongest is the x axis, where the degradation is the weakest.
• the criterion of distance from a configuration of cardan angles with respect to a singular configuration can be determined using one of the following parameters: - vector product standard the two angular momentum vectors carried by the two actuators; - absolute value of the sine of the angle formed by the two angular momentum vectors carried by the two actuators, - area of a triangle, two sides of which are the angular momentum vectors carried by the two actuators, their origins being in coincidence; and -difference between the unit and the absolute value of the scalar product of the two angular momentum vectors carried by the two actuators.
• the distance between a configuration of cardan angles and a singular configuration can in particular be determined using one of the following parameters: sum of the three products vectorial two by two of the angular momentum vectors carried by the three actuators and area of the triangle whose vertices coincide with the vertices of the angular momentum vectors carried by the three actuators, their origins being in coincidence.

Landscapes

• Engineering & Computer Science (AREA)
• Remote Sensing (AREA)
• Automation & Control Theory (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Radar, Positioning & Navigation (AREA)
• Aviation & Aerospace Engineering (AREA)
• Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)
• Variable-Direction Aerials And Aerial Arrays (AREA)
• Radio Relay Systems (AREA)

Priority Applications (7)

Applications Claiming Priority (2)

Publications (1)

Family

ID=8864776

Family Applications (1)

Country Status (10)

Cited By (22)

Families Citing this family (33)

Citations (2)

Family Cites Families (3)

• 2001
  • 2001-06-26 FR FR0108409A patent/FR2826470B1/fr not_active Expired - Fee Related
• 2002
  • 2002-06-24 DE DE60215174T patent/DE60215174T2/de not_active Expired - Lifetime
  • 2002-06-24 US US10/482,031 patent/US7171290B2/en not_active Expired - Lifetime
  • 2002-06-24 AT AT02764926T patent/ATE341783T1/de not_active IP Right Cessation
  • 2002-06-24 IL IL15957302A patent/IL159573A0/xx unknown
  • 2002-06-24 EP EP02764926A patent/EP1407335B1/fr not_active Expired - Lifetime
  • 2002-06-24 CA CA2452250A patent/CA2452250C/fr not_active Expired - Lifetime
  • 2002-06-24 JP JP2003507644A patent/JP4307247B2/ja not_active Expired - Lifetime
  • 2002-06-24 WO PCT/FR2002/002181 patent/WO2003001311A1/fr not_active Ceased
  • 2002-06-24 ES ES02764926T patent/ES2274088T3/es not_active Expired - Lifetime
• 2003
  • 2003-12-25 IL IL159573A patent/IL159573A/en active IP Right Grant

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events