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SINE/COSINE Encoder Support

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shaman
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SINE/COSINE Encoder Support

SINE/COSINE Encoders are seen in higher powered PMAC motors like the Motoenergy ME1304. These encoders take the place of hall effect sensors. This feature would be helpful in high power VESC designs like the BESC which would be very useful to drive such large PMAC motors.

paltatech
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Hi Shaman,

you can follow this pull request:
https://github.com/vedderb/bldc/pull/81

 

If you beat me to testing it with a motor let me know, maybe I can help setting up the bench. In my hardware both analog throttle inputs are protected and buffered, but I guess for very light testing its okay to run an ADC pin that close to the motor (its probably not okay).

 

Cheers
 

shaman
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I saw that too. I've been following marcos and team's controller development. I was really glad to see this!

Oliver
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I have an IPM Motor (Ashwoods IPM 200-33) which I want to run with the Vesc 75/300. As Ive seen Vesc supports Sin/Cos Encoders now but IPM benefits not yet offically? I want to run the motor in FOC with the implemented Sin/Cos Encoder. The Connectors of the Motor are described as VCC, GND, SINE, COSINE, PTTHERM. Where do I connect those wires on the Vesc? VCC, GND and PTTHERM is clear to me, but where do I connect SINE and COSINE? I was looking in the Github pull request but I didnt see the information, maybe because of I have no idea of reading coding :D 

district9prawn
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I don't think the 75/300 firmware has the adc ports for the sin cos encoder defined. The only spare adc ports you can repurpose are the two analog throttle inputs. 

There is a pull request from the Axiom guys with field weakening if you want to build the firmware and vesc tool. I gave it a try with a small outrunner but as soon as the controller tried to field weaken the motor halted and made a high pitched tone =( . I'm probably doing it wrong.

paltatech
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For sin/cos you need to use the accel/regen pins as inputs which forces you to provide torque commands over CANbus. This is natural for an Axiom board, not so much for a smaller vesc.

Some encoders provide sin+, sin-, cos+ and cos-, driven differentialy. Axiom supports that kind of differential signals unlike any other vesc variant. If your encoder provides single ended sin and cos signals, you need to make sure that signal is only lightly filtered, otherwise the waveforms will distort at high rpm. Its a though signal, every millivolt counts and you cant lowpass filter it too much.

 

The Field Weakening branch also includes Maximum Torque Per Amp control for IPM machines, but its not ready to merge, we had to steer our focus into the hardware side, but we will resume firmware dev asap.

Oliver
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Thank you both for your answers. So, I wont use the Vesc in this case.