TMS320F28379D: Position control with Absolute encoder

Kaarthi,

We're working to get this assigned to the correct person within the C2000 team, right now our expert is out of the office.  Right now he should be back in by Thursday of this week worst case. I'll see if there are some others in the team who can help out to get an answer sooner.

Best,

Matthew

Hello Kaarthi,

You may find this Application Note helpful.  It uses an absolute encoder.  The encoder protocol is different (t-format instead of BiSS) but the idea should be the same.  The source is in the MotorControl SDK (https://www.ti.com/tool/C2000WARE-MOTORCONTROL-SDK)

Application note: Quick Response Control of PMSM Using Fast Current Loop

Lori

Hi,

Sorry for late reply, I am using single turn BISS-C absolute encoder. I want to calculate the revolution counts and the direction of rotation. I have tried calculating the revolution counts by increamenting count every time position value goes above threshold but it does not seem to be accurate one. Is there any formal way to do this?

Regards,

Kaarthi

Hello - the position is encoded as part of the BiSS-C communication frame that is sent from the encoder.  If the encoder supports multi-turn then part of the position will be the turn number.  

The BiSS-C specification is available here for download: https://biss-interface.com/c/downloads/

Best regards

Lori

Hi,

I understand that the position is encoded in communication. I am able to read the data and run in position control but Since I am having single turn encoder, the count information is not available there and position control is not that much accurate now. So I want know how to properly count the number revolution in software. If there is any method please suggest me, it would be very helpful.

- kaarthi

Kaarthi,

If the application requires the number of turns, then a single turn encoder is not the best choice.  A single-turn encoder can be used for speed tracking or position within a single rotation (for example, with respect to a pivot point like a door).  The software can try to keep track of the rotations by the position transitioning from a "high number" --> "low number" or from a " low number" --> "high number"  (reverse direction) but as you mention there will always be some error to this approach.  Whether this is acceptable will be dependent on your application requirements. 

Regards

Lori