A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

The preset invention aims to improve the assembly accuracy and rotation accuracy of a fluid bearing device, and to further reduce the cost thereof. A bearing sleeve is fixed on the inner periphery of a housing. An axial member is supported in a non-contact manner in a radial direction by an oil film formed in a radial bearing gap. The housing made of resin is injection molded with the use of a substrate as an insert part. On the substrate, a control circuit for controlling a polygon scanner motor is mounted.

Fluid bearing device

A method of identifying the rotor position of a brushless DC (BLDC) motor and driving a motor smoothly from standstill without any position sensors is presented. This is done by monitoring the current responses to the inductance variation on the rotor position. The rotor position at standstill is detected by comparing the first and second differences of six current pulses injected into every two phases of the motor. Once the motor starts up, a pulse train, composed of long and short pulses, is injected into the commutation phases corresponding to the maximum torque production and the next commutation phases in alternating fashion. It provides not only the torque, but also information about the next commutation timing when the current responses of the long and short pulses cross each other in the same time delay. A controller for a BLDC motor is developed using a PC, digital signal processor (DSP), inverter and communication circuits in order to verify the proposed algorithm experimentally. It shows that the proposed algorithm can drive a BLDC motor smoothly without any vibration or time delay up to medium speed compared with the conventional back-EMF algorithm. Beyond this medium speed, a sensorless algorithm for rotor-position detection is switched to the back-EMF method to drive a BLDC motor at high speed.

Position detection and start-up algorithm of a rotor in a sensorless BLDC motor utilising inductance variation

A control system (100) for a five-phase brushless DC motor (102) including a stator having five windings and a rotor (116) mounted for rotation relative to the windings (114). The windings (114) are adapted to be electronically commutated in response to the rotary position of the rotor (116). The control system (100) includes a sensing circuit (106) to sense the rotary position of the rotor (116) using an optical or magnetic sensor or the back electromotive force voltages in the windings (114). Electronic switches (112) control the flow of current through the windings (114) in response to control signals generated by a control circuit (110) in response to the rotary position of the rotor (116). The control circuit (110) includes start-up logic to start the motor (102). If the rotor (116) is rotating in a wrong direction upon start-up, the control circuit (110) energizes preselected windings (114) and waits for the movement of the rotor (116) to come substantially to a stop and then energizes the windings (114) in a start-up sequence to cause the rotor (116) to rotate in a correct direction. Once the rotor (116) is rotating in the correct direction, the control circuit (110) electronically commutates the windings (114) in response to the rotary position of the rotor (116).

Control circuit for five-phase brushless dc motor

A control system for an electric motor having a stator and rotor including an inverter for providing power to the electric motor, a controller for controlling the inverter, a low speed control block to estimate the rotor angular position using stator current components operating in the controller, a high speed control block to estimate the rotor angular position using stator current components and stator flux position operating in the controller, a transition switch in the controller to vary operation between the low speed control block and the high speed control block, and where the inverter is controlled by six step operation.

Position sensorless control algorithm for ac machine

The present method and apparatus detects the rotor position of a brushless DC motor with an accuracy of π/m electrical radians (where m = the number of motor phases) within one electrical period, and provides enough information to enable starting the motor in the correct direction with certainty. After starting the motor in an open loop mode of one or two steps, a closed loop mode may be switched on, using a dynamic indirect position detection as is already well known in the technology. More specifically, the position at start is determined by the injection of short current pulses in different motor phases, each phase or pair of phases being energized first by a pulse of one polarity and of the opposite polarity. The sign of the time difference between the decay times of the induced voltages in the un-energized phase is detected. By performing a succession of these tests on different phases or pairs of phases of the standing motor, a table of results is established which clearly defines the position of the rotor relative to the motor phases. The same table then defines what polarity currents should be applied to each phase to reliably and certainly start the motor in the proper direction.

Position detection for a brushless DC motor without Hall effect devices using a mutual inductance detection method

An apparatus for rotatably journaling a rotor of a spindle motor about a shaft comprising a plurality of annular ring multi-pole magnets, each ring comprised of a plurality of axially aligned magnets whose polarity is alternated along the radius of the ring. The annular ring multi-pole magnets are disposed on both the rotor and stator of a spindle motor in opposition in attraction mode, or a complete offset repulsion mode with like poles facing one another with an full offset, thereby forming a radially stable magnetic bearing for maintaining rotor displacement about a shaft in conjunction with a conventional axial pivot.

Passive magnetic bearings for a spindle motor

An actuator arm assembly is provided in a disc drive. The disc drive includes a disc with a surface for storing information and a first actuator for moving the actuator arm assembly relative to the surface of the disc. The actuator arm assembly includes an actuator arm coupled to the first actuator, a load beam coupled to the actuator arm, a suspension coupled to the load beam and an air bearing coupled to the suspension. A transducer is mounted on the air bearing and positioned to access the surface of the disc. A second actuator is coupled to the air bearing and the load beam and is controllable to move the air bearing relative to the surface of the disc and relative to the load beam.

Microactuator for fine positioning in a disc drive

A disc drive data storage system according to the present invention comprises a housing, a central axis, a stationary member which is fixed with respect to the housing and coaxial with the central axis, and a rotatable member which is rotatable about the central axis with respect to the stationary member. At least one data storage disc is attached to and is coaxial with the rotatable member. Upper and lower ball bearing assemblies interconnect the stationary member and the rotatable member. At least one rotor magnet is attached to the rotatable member. A back-iron is supported by the stationary member. A stator winding is attached to the back-iron and has a slotless structure. The rotor magnet, back-iron and stator winding have a common axial position along the central axis and the stator winding is magnetically coupled to the rotor magnet such that the stator winding and the rotor magnet cooperate to reduce excitation of pure tone vibrations in the disc drive data storage system and to reduce transfer of the vibrations to the housing through the ball bearing assemblies.

Ironless spindle motor for disc drive

A disc drive spindle motor for rotating at least one disc in a data storage device includes a base, a shaft, a rotor and a stator. A bearing interconnects the rotor with the shaft and allows the rotor to rotate about the shaft. An overmold encapsulates at least a portion of the stator and provides the stator with a smooth external surface. The overmold mechanically isolates the stator from the base and damps sympathetic vibrations in the stator structure to reduce the generation of acoustic noise in the storage device.

Gunter K. Heine

Papers

Position detection for a brushless DC motor without Hall effect devices using a mutual inductance detection method

Passive magnetic bearings for a spindle motor

Microactuator for fine positioning in a disc drive

Ironless spindle motor for disc drive

Spindle motor having overmolded stator