Abstract: A Stationkeeping Mode for a spacecraft having a gimballed momentum wheel for attitude control in which the stationkeeping is divided into short duration open-loop stationkeeping maneuvers to correct orbital errors, and interlaced with closed-loop momentum management operations to manage momentum stored in the momentum wheel. The sequence of open-loop pulses are spaced to deadbeat a given dominant flexible motion of the spacecraft. Between and during the thruster pulses, the gimbaled momentum wheel is maintained in the closed-loop feedback control using gyro sensor or other inertial reference measurements. Limitations on the range of the momentum storage device and its torque capability are minimized by combining the maneuver thruster pulses with pulses from other thrusters, or by reducing the fire time of one of the maneuver thrusters, to minimize momentum buildup.

Abstract: A method of damping nutation and removing wobble of a spacecraft provided with first and second momentum sources having linearly independent momentum components in the plane transverse to the given axis. The method includes sensing angular velocities of the spacecraft along orthogonal first and second axes in the transverse plane, and generating velocity signals representative of the angular velocities. The velocity signals are processed to form control signals representative of desired torques for driving the momentum sources. The desired torques have a first additive component proportional to the angular velocities for removing the wobble and a second additive component proportional to the first derivatives of the angular velocities for damping the nutation.

Abstract: A robot gripper control system is disclosed which uses PVDF piezoelectric sensors to actively damp exerted force. Instead of charge amplifying the output of the piezoelectric transducer, the output voltage is measured as the charge drains across a path of low resistance. Thus, the sensor output is proportional to the rate-of-force exerted by the gripper. The PVDF sensor and a strain gauge are arranged in a proportional and derivative (PD) control system for the control of force of a robot manipulator hand. Experimental results for the particular disclosed gripper indicate that as much as 900% improvement in force step response rise time and a 300% reduction in overshoot are possible through the use of the PVDF sensor.

Abstract: A robot gripper control system is disclosed which uses PVDF piezoelectric sensors to actively damp exerted force. Instead of charge amplifying the output of the piezoelectric transducer, the output voltage is measured as the charge drains across a path of low resistance. Thus, the sensor output is proportional to the rate-of-force exerted by the gripper. The PVDF sensor and a strain gauge are arranged in a proportional and derivative (PD) control system for the control of force of a robot manipulator hand. Experimental results for the particular disclosed gripper indicate that as much as a 900% improvement in force step response rise time and a 300% reduction in overshoot are possible through the use of the PVDF sensor.