Question
We found that when resolver is connected to a motor (motor is supplied with AC supply), it is giving the SIN/COS input clipping Error.
We like to convert the SIN/SINLO signals to single ended signal.
Do you have detailed information about the TYPE II TRACKING LOOP, it seems a digital tracking loop, I think the response time of it should be slowerthan analog tracking loop.
Is that correct? What is the advantage of our TYPE II TRACKING LOOP if customer can sample the inputs from resolver and then process it in DSP.
Answer
The AD2S1210 converter always looks at the input signals differentially. If Sine and Cosine inputs are converted to single ended signals it is stillacceptable unless the amplitudes are incorrect. Converter performs some trigonometric operation on the Sine and Cosine inputs so that it analyzecombination of the inputs rather than each signal separately. Because of ratio metric operation when both inputs are scaled equally chip will be ableto provide correct position/velocity indication. Type 2 Tracking Loop has some advantages like:
- The digital output continuously tracks the resolver inputs- There is no tracking error at constant velocity- Ratio metric operations- Noise immunity due to second order filtering
Of course it is possible to build similar system based on DSP, ADCs and DACs however the cost of this will be much higher than products we offer.Also when you use ADCs, system requires computation, it’s not tracking the inputs continuously and it’s also sensitive to noise. I don’t think youcan get attractive performance level from this implementation and please bear in mind that Analog Devices is working on RDCs for many years thereforewe have a knowledge and experience in building Resolver to Digital systems.
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