摘要:
An spacecraft control system is provided that includes a tube and a plurality of microwheels. The plurality of microwheels is disposed within the tube. Each microwheel has a first stator wafer, a second stator wafer, and a rotor wafer disposed therebetween. The first and second stator wafers are configured to spin the rotor wafer.
摘要:
A momentum-control system comprising a plurality of momentum actuators and a platform upon which the plurality of momentum actuators are mounted. The momentum control system further comprises a plurality of active struts mounted on the bottom side of the platform. The active struts are configured to produce a force to steer the plurality of momentum actuators and the platform to produce forces and moments for spacecraft attitude control and disturbance suppression.
摘要:
A disturbance-cancellation system and method is provided that facilitates the adaptive cancellation of periodic disturbances. The disturbance-cancellation system and method includes a pair of control moment gyroscopes (CMGs) arranged together as a scissored pair. The scissored pair of CMGs is used to create a periodic torque with a controllable amplitude and frequency. The periodic torque created by the CMGs is adaptively controlled to cancel out periodic disturbances in the system. The system and method creates a periodic torque with a controllable amplitude and frequency by rotating the inner-gimbal assemblies of the CMGs in opposite directions at substantially equal phase and angular velocity. Amplitude matching can be achieved by adjusting the rotor spin rate. The steady-state constant motion results in a periodic torque along the output axis of the scissored pair, while components of torque along axes orthogonal to this one cancel out.
摘要:
Methods and apparatus are provided for reorienting control moment gyros (CMGs) to compensate for CMG failure or change in spacecraft (S/C) mass properties or mission. An improved CMG comprises a drive means for rotating the CMG around an axis not parallel to the CMG gimbal axis. Releasable clamps lock the CMG to the spacecraft except during CMG array reorientation. CMGs arrays are combined with attitude sensors, a command module, memory for storing data and programs, CMG drivers and sensors (preferably for each CMG axis), and a controller coupling these elements. The method comprises determining whether a CMG has failed or the S/C properties or mission changed, identifying the working CMGs of the array, determining a new array reorientation for improved spacecraft control, unlocking, reorienting and relocking the CMGs in the array and updating the S/C control parameters for the new array orientation.
摘要:
A momentum actuator for steering a spacecraft is disclosed. The momentum actuator comprises a rotor, a gimbal upon which the rotor is mounted, and a stepper motor coupled to the gimbal and operable to rotate the rotor about the gimbal in a series of steps. In one embodiment of the present invention the spin rate of the rotor can be varied to provide torque.
摘要:
The present method provides a method for avoiding singularities in the movement of CMGs in an array of CMGs in a spacecraft. In a first step, a torque command representing a desired torque to produce an attitude adjustment for the spacecraft is received. Next, a range-space gimbal rate required to produce the desired torque based on the desired torque and a Jacobian matrix is calculated. Then, a null-space gimbal rate that assists in the avoidance of singularities is calculated. The total gimbal rate command is determined by summing the range-space gimbal rate and the null-space gimbal rate. Then, the total gimbal rate command is provided to the CMGs to produce the total gimbal rate.
摘要:
A control system of a spacecraft for controlling two or more sets of collinear control moment gyroscopes (CMGs) comprises an attitude control system. The attitude control system is configured to receive a command to adjust an orientation of the spacecraft, determine an offset for a momentum disk for each of the two or more sets of CMGs that maximizes torque, determine a momentum needed from the two or more sets of CMGs to adjust the orientation of the spacecraft, and calculate a total torque needed by taking the derivative of the momentum. The control system further comprises a momentum actuator control processor coupled to the attitude control system, the momentum actuator control processor configured to calculate a required gimbal movement for each of the CMGs in each of the two or more sets of collinear CMGs from total torque.
摘要:
A process for determining an attitude measurement of a spacecraft is provided. The process employs a Horizon-Crossing Indicator (HCI) sensor 108. The process uses three time tagged crossings of the earth circle 104 to provide sufficient HCI data to determine the earth center 106. Since these observations may be infrequent, the relative attitude of the spacecraft 100 changes for each observation time. Therefore, once the integrated angular rate data, and thus the attitude relative to some reference, for the first, second and third horizon crossings is obtained, the sensor bore-sight data for each of these observations is transformed back to a known reference time. In one example, the integrated angular rate data from the third and second horizon crossings is transformed back to first horizon crossing time T1. Then, existing techniques can be applied to compute the transformation from the axes of the satellite 100 at the reference time T1 to some other axes at that time, resulting in an attitude estimate for the satellite 100.
摘要:
Methods and apparatus are provided for reaction wheel (RW) assemblies for spacecraft. The apparatus comprises a M/G coupled to an inertia wheel and a controller coupled to the M/G that, in response to commands it receives, couples power to or from an M/G of another RW assembly over a shared transfer connection (VXFR), so that one M/G acts as a generator powering another M/G acting as a motor. The controller compares generator voltage VGEN to the BEMF of the motor on VXFR and reconfigures a multi-winding M/G or steps-up the generated voltage to maintain VGEN>VXFR to maximize direct energy transfer from one RW to the other as long as possible. When VGEN declines sufficiently, the controller can couple the motor to the spacecraft power bus and/or the generator to a power dump so as to continue to provide the commanded torque if needed. Operation is automatic.
摘要:
A method for avoiding singularities in the movement of CMGs in an array of CMGs in a spacecraft includes a first step where a maneuver command to rotate a spacecraft orientation is received. Then, the torque needed to rotate the spacecraft's orientation is determined. Then, the torque is integrated to determine a momentum path. The momentum path is decomposed into a sequence of straight line segments. For each line segment, a unit vector along the straight line segments is determined. Then, it is determined if there is a continuous path connecting a start point and an end point of the line segment in a plane perpendicular to the unit vector. For each point along the path in the plane perpendicular to the unit vector, a set of gimbal angles is determined.