WOLFRAM SYSTEM MODELER
SinCosEncoderEvaluation of a sinusoidal encoder |
SystemModel["Modelica.Blocks.Examples.SinCosEncoder"]
This information is part of the Modelica Standard Library maintained by the Modelica Association.
This examples demonstrates robust evaluation of a sin-cos-encoder.
The sin-cos-encoder provides four tracks:
All four tracks have the same amplitude and the same offset > amplitude. Offset is used to detect loss of a track. To remove offset, (minus sine) is subtracted from (sine) and (minus cosine) from (cosine), resulting in a cosine and a sine signal with doubled amplitude but without offset.
Interpreting cosine and sine as real and imaginary part of a phasor, one could calculate the angle of the phasor (i.e. transform rectangular coordinates to polar coordinates). This is not very robust if the signals are superimposed with some noise. Therefore the phasor is rotated by an angle that is obtained by a controller. The controller aims at imaginary part equal to zero. The resulting angle is continuous, i.e. differentiating the angle results in 2*π*frequency. If desired, the angle can be wrapped to the interval [-π, +π].
ramp |
Type: Ramp Description: Generate ramp signal |
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cosB |
Type: CosineVariableFrequencyAndAmplitude Description: Generate cosine signal with variable frequency and amplitude |
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cosBminus |
Type: CosineVariableFrequencyAndAmplitude Description: Generate cosine signal with variable frequency and amplitude |
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sinA |
Type: SineVariableFrequencyAndAmplitude Description: Generate sine signal with variable frequency and amplitude |
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sinAminus |
Type: SineVariableFrequencyAndAmplitude Description: Generate sine signal with variable frequency and amplitude |
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feedbackCos |
Type: Feedback Description: Output difference between commanded and feedback input |
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feedbackSin |
Type: Feedback Description: Output difference between commanded and feedback input |
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rotator |
Type: Rotator Description: Rotates space phasor |
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integrator |
Type: Integrator Description: Output the integral of the input signal with optional reset |
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der1 |
Type: Der Description: Derivative of input (= analytic differentiations) |
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wrapAngle |
Type: WrapAngle Description: Wrap angle to interval ]-pi,pi] or [0,2*pi[ |
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toPolar |
Type: ToPolar Description: Converts a space phasor to polar coordinates |