Abstract: An exemplary piezoelectric actuator includes a piezoelectric transducer that exhibits displacements when energized with corresponding voltages. A control system is electrically connected to the piezoelectric transducer so as to provide the transducer with the voltages. The control system includes feedback of displacements of the transducer as functions of respective voltage commands and feed-forward of electrical currents passing through the transducer as functions of the respective voltages applied to the transducer. The control system further has a feedback controller connected to receive transducer-displacement data corresponding to the voltages applied to the transducer. The control system further can include a current-feed-forward amplifier connected to receive transducer-current data corresponding to the voltages applied to the transducer. Such a control system facilitates reduction of hysteresis in controlled actuation of the actuator.

Abstract: An exemplary piezoelectric actuator includes a piezoelectric transducer that exhibits displacements when energized with corresponding voltages. A control system is electrically connected to the piezoelectric transducer so as to provide the transducer with the voltages. The control system includes feedback of displacements of the transducer as functions of respective voltage commands and feed-forward of electrical currents passing through the transducer as functions of the respective voltages applied to the transducer. The control system further has a feedback controller connected to receive transducer-displacement data corresponding to the voltages applied to the transducer. The control system further can include a current-feed-forward amplifier connected to receive transducer-current data corresponding to the voltages applied to the transducer. Such a control system facilitates reduction of hysteresis in controlled actuation of the actuator.

Abstract: Methods and apparatus for providing vibration compensation using position measurements are disclosed. According to one aspect of the present invention, a method of compensating for vibrations of an object includes obtaining a plurality of position measurements associated with the object. The method also includes processing the plurality of position measurements to determine a derivative acceleration, and determining a compensatory force to counteract the vibrations of the object. Determining the compensatory force includes using the derivative acceleration. Finally, the method includes applying the compensatory force to the object.

Abstract: An optical isolation assembly (30) for reducing the transmission of vibration from an optical barrel (25) to an optical element assembly (28) includes an optical mover assembly (256), a first measurement system (258), a second measurement system (260), and a control system (24). The optical mover assembly (256) moves, positions and supports the optical element assembly (28) relative to the optical barrel (25). The first measurement system (258) generates one or more first measurement signals that relate to the relative position between the optical element assembly (28) and the optical barrel (25). The second measurement system (260) generates one or more second measurement signals that relate to the absolute movement of the optical element assembly (28) along the first axis. The control system (24) controls the optical mover assembly (256) utilizing the first measurement signals and the second measurement signals.

Abstract: Methods and apparatus for providing vibration compensation using position measurements are disclosed. According to one aspect of the present invention, a method of compensating for vibrations of an object includes obtaining a plurality of position measurements associated with the object. The method also includes processing the plurality of position measurements to determine a derivative acceleration, and determining a compensatory force to counteract the vibrations of the object. Determining the compensatory force includes using the derivative acceleration. Finally, the method includes applying the compensatory force to the object.

Abstract: Disclosed are, inter alia, optical components that include an optical element (e.g., mirror) and at least three active-isolation mounts mounting the optical element to a frame (e.g., optical barrel or optical frame). An active-isolation mount has a non-contacting actuator connecting a respective location on the optical element to the frame and provides movability of the respective location relative to the frame in at least one direction. At least one displacement sensor is associated with each respective location on the optical element. The displacement sensors are sensitive to displacements of the respective locations in at least one respective direction and reference the displacements to an absolute reference. The actuators and sensors are connected to a servo control loop to provide feedback control.

Abstract: Disclosed are, inter alia, optical components that include an optical element (e.g., mirror) and at least three active-isolation mounts mounting the optical element to a frame (e.g., optical barrel or optical frame). An active-isolation mount has a non-contacting actuator connecting a respective location on the optical element to the frame and provides movability of the respective location relative to the frame in at least one direction. At least one displacement sensor is associated with each respective location on the optical element. The displacement sensors are sensitive to displacements of the respective locations in at least one respective direction and reference the displacements to an absolute reference. The actuators and sensors are connected to a servo control loop to provide feedback control.

Abstract: A precision assembly (210) for positioning a device (226) includes a stage (260) that retains the device (226), a dual mover assembly (228) that moves the stage (260), and the device (226) along a movement axis (266), a measurement system (222) and a control system (224). The dual mover assembly (228) includes a first mover (262) that moves the stage (260) along the movement axis (266) and a second mover (264) that moves the device (226) along the movement axis (266). The second mover (264) is rigidly coupled to the first mover (262) so that movement of the first mover (262) results in movement of the second mover (264). Further, the total output of the dual mover assembly (228) along the movement axis (266) is equal to the sum of the movement of the first mover (262) and the movement of the second mover (264). The measurement system (222) measures a movement position along the movement axis (266). The control system (224) controls the dual mover assembly (228) utilizing the movement position.

Abstract: Embodiments of the invention relate to a cable force feedforward approach that takes into account the cable force in the counter-mass trajectory computation to reduce or eliminate vibration of the lens body caused by the cable force disturbance and corrective force exerted by the trim motors. In one embodiment, a method provides cable force feedforward control for a counter-mass of a stage with a cable connected to the counter-mass and using the cable force feedforward control to control one or more trim motors to produce a trim motor output force to be applied to the counter-mass, the counter-mass moving in response to a reaction force from movement of the stage.

Abstract: “Hexapod” mountings are disclosed for use with optical elements. An exemplary mounting includes a base, a platform that is movable relative to the base, and six legs having nominally identical length. Three pairs of legs, having substantially equal stiffness, extend between the base and platform and support the platform relative to the base. In each pair of legs, respective first ends are coupled together in a ?-shaped manner forming a respective apex. Respective second ends are splayed relative to the apex, desirably forming an angle of substantially 109.5° at the apex. The apices are mounted equidistantly from each other on a circle on the platform. The respective second ends of the pairs of legs are mounted at respective locations on a circle on the base. The axes of each pair of legs define a respective leg plane substantially perpendicular to the base plane. Each leg has an actuator that, when energized, changes a length of the respective leg.

Abstract: A precision assembly (210) for positioning a device (226) includes a stage (260) that retains the device (226), a dual mover assembly (228) that moves the stage (260), and the device (226) along a movement axis (266), a measurement system (222) and a control system (224). The dual mover assembly (228) includes a first mover (262) that moves the stage (260) along the movement axis (266) and a second mover (264) that moves the device (226) along the movement axis (266). The second mover (264) is rigidly coupled to the first mover (262) so that movement of the first mover (262) results in movement of the second mover (264). Further, the total output of the dual mover assembly (228) along the movement axis (266) is equal to the sum of the movement of the first mover (262) and the movement of the second mover (264). The measurement system (222) measures a movement position along the movement axis (266). The control system (224) controls the dual mover assembly (228) utilizing the movement position.

Abstract: Embodiments of the invention relate to a cable force feedforward approach that takes into account the cable force in the counter-mass trajectory computation to reduce or eliminate vibration of the lens body caused by the cable force disturbance and corrective force exerted by the trim motors. In one embodiment, a method provides cable force feedforward control for a counter-mass of a stage with a cable connected to the counter-mass and using the cable force feedforward control to control one or more trim motors to produce a trim motor output force to be applied to the counter-mass, the counter-mass moving in response to a reaction force from movement of the stage.

Abstract: A control system for the adjustment and calibration of electromagnetic devices, such as E-I core electromagnetic devices, using adaptive gain adjustment. A controller is provided with an input current and an output force and provides an output signal indicative of a force gain estimate, wherein the force gain estimate is the ratio of the output force to the input current.

Abstract: An equalization filter for counteracting the effects of unwanted resonance modes and noise in the VCM plant. The filter comprises a transfer function derived from a function of the actual VCM plant response and an ideal response, for which the servo controller is designed. The response of the combined equalization filter and the actual VCM plant response substantially adheres to the ideal response. The disc drive includes firmware operable to generate one or more equalization filters for each of one or more heads.

Abstract: Methods and apparatus for applying a uniform polishing pressure on a wafer are disclosed. According to one aspect of the present invention, a chemical mechanical planarization polishing apparatus includes a polishing pad, a wafer holder, and a force control system. The wafer holder supports a wafer to be polished using the polishing pad. The polishing pad is arranged to move relative to the wafer holder such that an area of contact between the wafer holder and the polishing pad varies. The force control system including a controller and a plurality of actuators that apply forces to the polishing pad. The controller controls the forces as the area of contact varies to substantially maintain a first polishing pressure on the wafer arranged to be supported by the wafer holder.

Abstract: A repeatable runout (RRO) identification device for use with a disc drive having a rotatable disc is provided. The RRO identification device determines RRO values for servo fields of a first track of the disc as a function of received position error signal (PES) values for the servo fields independent of averaging the PES values for each servo field. The RRO identification device compares, in real-time, each determined RRO value for each servo field with a threshold repeatable runout value.

Abstract: A control system for the adjustment and calibration of electromagnetic devices, such as E-I core electromagnetic devices, using adaptive gain adjustment. A controller is provided with an input current and an output force and provides an output signal indicative of a force gain estimate, wherein the force gain estimate is the ratio of the output force to the input current.

Abstract: An apparatus and method of correcting for written-in repeatable run-out in a disc drive having a servo loop for positioning a head over a rotating disc is provided. The rotating disc has at least one data track and servo information recorded in a plurality of servo fields along the data track. An initial written-in repeatable run-out compensation value for each servo field is computed as a function of a position error signal generated for each servo field during a first revolution of the disc. The initial written-in repeatable run-out compensation value for each servo field is then injected into the servo loop during another revolution of the disc. A compensated position error signal for each servo field is computed as a function of the initial written-in repeatable run-out compensation value for each servo field. A refined written-in repeatable run-out compensation value for each servo field is then computed as a function of the compensated position error signal for each servo field.

Abstract: A method and system for providing plant variation compensation for a microactuator in a dual-stage servomechanism of a disc drive. The method includes performing indirect adaptive filtering to identify plant variation in the microactuator, and tuning a compensator for the microactuator based on the plant variation. The indirect adaptive filtering can be performed using a two-stage process, including a first stage of adaptive modeling for the dual-stage servomechanism and a second stage of generating an indirect mode-reference inverse for the microactuator. A combined process can alternatively be employed. The microactuator can be a piezoelectric microactuator which forms a PZT system. The dual-stage servomechanism also includes a coarse actuator such as a voice coil motor.

Abstract: A repeatable runout (RRO) identification device for use with a disc drive having a rotatable disc is provided. The RRO identification device determines RRO values for servo fields of a first track of the disc as a function of received position error signal (PES) values for the servo fields independent of averaging the PES values for each servo field. The RRO identification device compares, in real-time, each determined RRO value for each servo field with a threshold repeatable runout value.