AEDB-9340-B-02-C中文资料(2)

Theory of Operation

The AEDB-9340 optical encoder is a emitter-detectormodule. Coupled with codewheel, these modules trans-late the rotary motion of a shaft into six-channel digitaloutput.

The modules contain a single Light Emitting Diode(LED) as light source. The light is collimated into aparallel beam by means polycarbonate lens locateddirectly over the LED. Opposite the emitter is a detectorIC. This IC consists of multiple sets of photo detectorsand signal processing circuitry necessary to producedigital waveforms output.

The codewheel rotates between the emitter and detec-tor, causing the light beam to be interrupted by patternof spaces and bars on the codewheel.

The Photodiodes that detect these interruptions arearranged in a pattern that corresponds to the radiusanddesign of the codewheel. These detectors are alsospacedin such away that light period on one pair ofdetectors corresponds to dark period on adjacent pairofdetectors.

The photodiode outputs are then fed through the signalComparators receive these signals and produce the finaloutputs for channels A and B. Due to this integratedphasing technique, the digital output of channel A isinquadrature with that of channel B (90 degrees out ofphase). The commutation feedback (U, V, W) signalsaregenerated based on the codewheel design.

Definitions

Cycles (N): The number of electrical cycles perrevolution(CPR). Note: CPR refers to the raw signal fromencoder, that is the cycles before 4x decode.One Cycle: 360 electrical degrees (°e).One Shaft Rotation: 360 mechanical degrees.

Cycle Error (DC): An indication of cycle uniformity. Thedifference between an observed shaft angle which givesrise to one electrical cycle, and the nominal angularincrement of 1/N of a revolution.

Pulse Width (P): The number of electrical degrees thatan output is high during 1 cycle. This value is nominally180°e or 1/2 cycle.

Pulse Width Error (DP): The deviation, in electricaldegrees, of the pulse width from its ideal value of 180°e.State Width (S): The numbers of electrical degreesbetween transitions in the output of channel A and theneighboring transition in the output of channel B. Thereare 4 states per cycle, each nominally 90°e.

State Width Error (DS): The deviation, in electricaldegrees, of each state width from its ideal value of 90°mutation Accuracy (DI): The deviation, inmechanical degrees, after shaft rotates passing thereference point (Index channel) to the first Channel-Upulse. The measurement from middle of Channel-I torising edge of Channel-U.

Phase (f): The numbers of electrical degrees betweenthe center of the high state of channel A and the centerof the high state of channel B. This value is nominally90°e for quadrature output.

This value is nominally 90°e for quadrature output.Phase Error (Df): The deviation of the phase from itsideal value of 90°e.

Direction of Rotation: When the codewheel rotates inthe clockwise direction viewing from top of themodule(direction from pin U to B), channel A will leadchannel B. If the codewheel rotates in the oppositedirection (direction from pin B to U), channel B willleadchannelA.

Optical Radius (Rop): The distance from thecodewheel’s center of rotation to the optical center(O.C.) of the encoder module.

Index Pulse Width (Po): The number of electricaldegrees that an index is high with reference to channelA or channel B during one full shaft rotation.

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