Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Sankyo Seiki Absolute Encoder
#1
Does anyone have experience interfacing a Power Brick AC with a OTC Daihen Robot Manipulator.

This is just a project I am doing for fun to teach myself Kinematics. I have a manual and pinouts for the old (2000 era) manipulator and it states it uses Sankyo Seiki Servos with Absolute encoders utilizing a S+ S- encoder data connection.

I'm hoping to one day have my own "Rotating Forks Demo"

Thanks
John.
Reply
#2
I don't know anyone with experience with Sankyo Seiki robots/motors. It is possible that we can communicate with the encoder, but from looking online, I can't quickly find what serial protocol they use. There are certain protocols that would need a (factory programmed) Accessory 84B to read, and others that we simply can't read, but the Gate3 inside the Power Brick can be configured to read a handful of protocols via software.

The Power Brick AC manual does list how to interface with a number of serial encoders--if you know the number of bits of resolution, your best bet might just be looking at the pinout to see which signals are used, wiring them to the Brick, and then trying out various serial encoder protocols/configurations, only changing the number of bits. If you get the right protocol, turning the motor you should be able to see the data changing. However, without knowing exactly what protocol they use, the recommended clock speed, encoder resolution, etc., it's not something I'd be able to directly tell you how to do.
Reply
#3
Couldn't get it to work. I tried every protocol and a bunch of random message types.

I hooked up my scope and see the Brick sending the commands but the the Sankyo Seiki encoder wouldn't respond or do anything.

I was thinking about replacing it with a CUI AMT232B-V absolute encoder that supports SSI and would use the same number of pins so I can use the existing wiring harness.

I'll have to turn the encoder end of the rotor down on my lathe as the shaft is to big to support the AMT device. I just ordered one for now to see if it will even work.

When I pulled the motor apart I saw the pole configuration in my picture and got confused? I'm assuming they must have the stator wound in a way that the poles line up but from the looks of it there are 9 poles that don't line up. I had not even bothered to push a little holding current into the motor yet to check the pole count since I normally do that after I get the encoder working.

Talk about proprietary. I just wanted to share this.

Have a good weekend.
John.


Attached Files Image(s)
   
Reply
#4
That looks like a 6-pole motor to me.

A two-pole motor would have a single north pole and a single south pole on the rotor and one winding on the stator for each of the three phases.

A four-pole motor would have two north poles and two south poles on the rotor and two windings on the stator for each of the three phases.

A six-pole motor would have three north poles and three south poles on the rotor and three windings on the stator for each of the three phases.

This stator fits into that last category.
Reply
#5
I opted to go with the CUI AMT33 encoder because it provides the ability to zero the commutation angle along with hall outputs and programmable encoder. I turned the rotor end down to size. Reassembled the motor and fitted the replacement encoder.

I applied DC current to U and V and I'm seeing 4 defined magnetic positions. That should make this an 8 pole motor?

I locked it up with DC into U and V and configured the encoder to 8 pole / 2048 ppr / Zeroed the Commutation angle.

I stepped through the GUI setup for the motor and passed everything. I have a very soft / slow control with closed loop. If I try to issue open loop commands from the terminal it either locks in a position, runs away or makes some really odd sounds and trips the i2t. If I phase it again it will return so soft slow closed loop control. If I attempt to adjust the jog speed it will run away / lock in position / trip i2t. Pick any one.

I'm pretty sure the commutation angle is not set correctly. Is there a way to lock the motor into a zero angle using the delta tau controller so I can try to zero it there.

Thanks
John.
Reply
#6
I'm not sure if you have the Power Brick AC or Power Brick AC ARM, but for either one, the "Manual Force Phasing" on Page 182 of the Power Brick AC ARM Manual should do that. In short, the by writing an acceptable value to the B Phase Bias parameter (with nothing on the A Phase), the motor should lock into its zero angle for commutation.
Reply
#7
Thanks.

That worked like a charm. Motor is fully tuned and working great. Only 5 more to go.

Have a great Holiday weekend.
John.
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)