Abstract: An attitude control module is described for providing propellant-free attitude control and momentum desaturation to a spacecraft. The attitude control module includes at least one solar sail comprising a reflective surface for reflecting solar photons; and at least one robotic arm coupled to the at least one solar sail, said at least one robotic arm comprising at least 4 degrees of freedom for positioning and orienting the at least one solar sail relative to the spacecraft. A corresponding method for operating the attitude control module to unload excess momentum from a spacecraft is also described.

Abstract: An attitude control module is described for providing propellant-free attitude control and momentum desaturation to a spacecraft. The attitude control module includes at least one solar sail comprising a reflective surface for reflecting solar photons; and at least one robotic arm coupled to the at least one solar sail, said at least one robotic arm comprising at least 4 degrees of freedom for positioning and orienting the at least one solar sail relative to the spacecraft. A corresponding method for operating the attitude control module to unload excess momentum from a spacecraft is also described.

Abstract: An energy-efficient and accurate torque control system and method for multiphase nonsinusoidal PMSM with or without open-circuited phase(s) under time-varying torque and speed conditions is based on orthogonally decomposing a phase voltage vector into two components, which become primary and secondary control inputs for torque control and energy minimizer control. The primary control system includes nonlinear feedback from measured phase currents, motor angle, motor speed, and instantaneous value of reference torque and a signature vector indicating which phase(s) is/are open-circuited to establish a first-order linear relationship between reference and generated torques.

Abstract: A technique for controlling drive currents to respective windings of a multi-winding brushless motor comprises monitoring an output of the motor and a demand of the motor, determining whether a failure mode has occurred, the failure mode being an instantaneous complete or partial failure to generate demanded output; and, upon detection of a failure mode on a first winding, distributing a demand contribution that is not being produced by the first winding to one or more of the windings that are not in a failure mode. The demand may be torque demand, and the failure modes may include winding failure, and voltage and/or current saturation. Improved torque output is generated by the redistribution of demand among phases in the event of a failure mode.

Abstract: A method and apparatus are provided for ripple suppression of brushless DC motors at any given velocity irrespective of the limited bandwidth of the driver/amplifier supplying the excitation currents to the stator. In a preferred embodiment, Fourier coefficients of the current waveform are calculated as a function of rotor velocity by taking into account the driver/amplifier's finite bandwidth dynamics. For a given velocity, Fourier coefficients of the series approximating the waveform (control signal) are calculated as a function of the rotor velocity and the amplifier dynamics, to generate a waveform that results in no torque or velocity pulsations. When changing the motor speed, the coefficients are updated (recalculated) based on the new desired velocity (and amplifier dynamics), resulting in generation of an updated waveform that results in no torque or velocity pulsations at the new motor speed.

Abstract: A technique for controlling drive currents to respective windings of a multi-winding brushless motor comprises monitoring an output of the motor and a demand of the motor, determining whether a failure mode has occurred, the failure mode being an instantaneous complete or partial failure to generate demanded output; and, upon detection of a failure mode on a first winding, distributing a demand contribution that is not being produced by the first winding to one or more of the windings that are not in a failure mode. The demand may be torque demand, and the failure modes may include winding failure, and voltage and/or current saturation. Improved torque output is generated by the redistribution of demand among phases in the event of a failure mode.

Abstract: A method and apparatus are provided for ripple suppression of brushless DC motors at any given velocity irrespective of the limited bandwidth of the driver/amplifier supplying the excitation currents to the stator. In a preferred embodiment, Fourier coefficients of the current waveform are calculated as a function of rotor velocity by taking into account the driver/amplifier's finite bandwidth dynamics. For a given velocity, Fourier coefficients of the series approximating the waveform (control signal) are calculated as a function of the rotor velocity and the amplifier dynamics, to generate a waveform that results in no torque or velocity pulsations. When changing the motor speed, the coefficients are updated (recalculated) based on the new desired velocity (and amplifier dynamics), resulting in generation of an updated waveform that results in no torque or velocity pulsations at the new motor speed.

Abstract: In order to determine positional information, about a mobile robot, Real Time Kinematic (RTK) Global Satellite Navigation System (GNSS) measurement data are obtained by at least two GNSS receivers mounted on the mobile robot. Estimates of the covariance matrices of the measurement data are computed. The RTK GNSS measurement data are combined according to the covariance matrices to obtain enhanced positional information. The results may be fused with data from an IMU to obtain driftless attitude and/or localization information.

Abstract: A system for replicating the behavior of a target robotic manipulator with respect to a payload and worksite, has a real-time simulator capturing the dynamics of the target robot manipulator; a mock-up of the payload and worksite; and an emulating robotic manipulator for interacting with said payload and worksite. The emulating robotic manipulator is controlled by the real-time simulator in a control loop to replicate the dynamical behavior of said target robotic manipulator in its environment by matching the impedance of the emulating robotic manipulator with that of the target robotic manipulator.

Abstract: A combined scheme of identification and torque control is provided for rotary hydraulic actuators. The composite controller consists of a dynamic feedback linearizing inner loop cascaded with a robust linear feedback outer loop. The proposed controller allows the actuator to generate desired torque irrespective of the actuator motion. In fact, the controller reduces significantly the impedance of the actuator as seen by its external load, making the system an ideal source of torque suitable for many robotics and automation applications. An identification method to extract the parameters of non-linear model of actuator dynamics and to estimate a bound for modeling uncertainty, used for synthesis of the outer optimal controller, is also presented. Results are illustrated experimentally on a pitch actuator of a Schilling industrial robot.

Abstract: A system for replicating the behavior of a target robotic manipulator with respect to a payload and worksite, has a real-time simulator capturing the dynamics of the target robot manipulator; a mock-up of the payload and worksite; and an emulating robotic manipulator for interacting with said payload and worksite. The emulating robotic manipulator is controlled by the real-time simulator in a control loop to replicate the dynamical behavior of said target robotic manipulator in its environment by matching the impedance of the emulating robotic manipulator with that of the target robotic manipulator.

Abstract: A combined scheme of identification and torque control is provided for rotary hydraulic actuators. The composite controller consists of a dynamic feedback linearizing inner loop cascaded with a robust linear feedback outer loop. The proposed controller allows the actuator to generate desired torque irrespective of the actuator motion. In fact, the controller reduces significantly the impedance of the actuator as seen by its external load, making the system an ideal source of torque suitable for many robotics and automation applications. An identification method to extract the parameters of non-linear model of actuator dynamics and to estimate a bound for modeling uncertainty, used for synthesis of the outer optimal controller, is also presented. Results are illustrated experimentally on a pitch actuator of a Schilling industrial robot.

Abstract: The present invention provides an emulation system having a control system that allows the testing of a satellite control system with all of its hardware in place, i.e. fully integrated. The emulation methodology is applicable to the case of either a rigid spacecraft or a flexible spacecraft, provided that the spacecraft's sensors and actuators are stowed to the rigid part of spacecraft in the case of a flexible spacecraft. Practically, the latter condition is not restrictive, as the actuators and sensors are usually placed rigidly in the satellite bus, while the satellite solar panels constitute the flexible elements. The control system is used to tune the mass properties and dynamic behaviour of a rigid ground-spacecraft in a 1-G environment to those of a flight-spacecraft in 0-G. A six-axis force/moment sensor is placed at an interface of the ground-spacecraft and a manipulator.