Look at the specification: 0.001 Degree = one part in 360x 1000=360000, or maybe 36000. Not simple to achieve with a 2000PPR encoder.
Did I miss the part of the app note where each encoder pulse is divided into 100 counts?

 

One more observation relates to the stated accuracy requirement: .Indexing accuracy needed for rotary table 0.001 deg it does not seem that you can get that with a 2000PPR encoder. on the turn table. And if you put the encoder on the motor, the 50:1 reduction box needs to have zero backlash. So there will need to be some sort of compromise. It is not clear to me where the "precision trimpots" come in to play, perhaps for setting the position? But neither the resolution nor the accuracy are within the capabilities of the encode/mechanical pieces. In addition I saw no reference to the required positioning speed. Often times with servo systems, speed is important.

Trimpots are used for opamp gain setting.some field oriented control arithmetic are performed with opamp as preprocessing step instead of doing all arithemtics digitally

 

OK, I see. Perfectly stable trim-pots and very stable op-amps. IS the position control system going to utilize the BLDC motor drive signal to read position??? Or is the 2000PPR encoder going to be reading motor position??\
2000PPRx50:1 =10, 0000 is closer to 360,000, but still not close to 0.001 degree accuracy. And my numbers are based on a gear reduction with no backlash at all. Of course, given that we have no hint as to the size of that turntable. The fixed steps turntable I was referencing was 15 feet in diameter and weighed several tons.
So the big question is about just how is the actual position of the TS turn table to be sensed???
It is fairly standard that every feedback control system will have at least one sensor providing the feedback information.

 

The OP can spend some money on something like a used Model M35 encoder for 360,000 PPR if that sort of high resolution is needed in a direct drive application.
https://www.celeramotion.com/wp-content/uploads/2019/05/LP-Data_Sheet-Packaged_DRC-M35.pdf

On the bottom of the LCD display you see the encoder position error slowly counting down from an offset of 135 to zero of the encoder shaft rotation.
8.33ns resolution using 32 bit PWM for sinusoidal commutation.
https://www.motioncontroltips.com/what-is-sinusoidal-commutation-for-dc-motors/

https://forum.allaboutcircuits.com/threads/pic32mk-mc-qei-example.150351/post-1531704

 

One more observation relates to the stated accuracy requirement: .Indexing accuracy needed for rotary table 0.001 deg it does not seem that you can get that with a 2000PPR encoder. on the turn table. And if you put the encoder on the motor, the 50:1 reduction box needs to have zero backlash. So there will need to be some sort of compromise. It is not clear to me where the "precision trimpots" come in to play, perhaps for setting the position? But neither the resolution nor the accuracy are within the capabilities of the encode/mechanical pieces. In addition I saw no reference to the required positioning speed. Often times with servo systems, speed is important.

A 2000 pulse/rev quadrature encoder is is capable of 4x that resolution by counting all four edges .

 

A 2000 pulse/rev quadrature encoder is is capable of 4x that resolution by counting all four edges .

OK, so 4x2000PPR=8000 PPR. 8000 x 50=40,000 PPR if the encoder is on the motor side of the ZERO BACKLASH gearbox. and 40,000 is closer to 360,000, but still not close to 0.001 degree accuracy. And what is a 50:1 ZERO backlash gearbox going to cost???

 

OK, so 4x2000PPR=8000 PPR. 8000 x 50=40,000 PPR if the encoder is on the motor side of the ZERO BACKLASH gearbox. and 40,000 is closer to 360,000, but still not close to 0.001 degree accuracy. And what is a 50:1 ZERO backlash gearbox going to cost???

8000*50=400000

 

OK, I see. Perfectly stable trim-pots and very stable op-amps. IS the position control system going to utilize the BLDC motor drive signal to read position??? Or is the 2000PPR encoder going to be reading motor position??\
2000PPRx50:1 =10, 0000 is closer to 360,000, but still not close to 0.001 degree accuracy. And my numbers are based on a gear reduction with no backlash at all. Of course, given that we have no hint as to the size of that turntable. The fixed steps turntable I was referencing was 15 feet in diameter and weighed several tons.
So the big question is about just how is the actual position of the TS turn table to be sensed???
It is fairly standard that every feedback control system will have at least one sensor providing the feedback information.

Motor encoder used as a position feedback.motor is blac/industrial servo,not bldc.turntable dia is 350mm

 

Motor encoder used as a position feedback.motor is blac/industrial servo,not bldc.turntable dia is 350mm

OK, a much smaller turntable, much simpler to move. And the motor is much more suited to the task, so that is a benefit. But certainly the specified position accuracy of within 0.001 degree is a real challenge.