SDC1130 sudden stop at reaching desired position

5 years 1 month ago - 5 years 1 month ago #29531075 by davidk
Hi,

I have one SDC1130 and one SDC2130s controllers.
I've set both in Closed Loop Count Position and I have the following issue with the SDC1130 driver:
I send !P 200000 command.

Driver accelerates the motor, reaching desired speed (e.g1000rpm) but does not deccelerate until reaching position; then it sudden stops the motor.
I tried with:
Max speed: 1000rpm
Acc: 200 to 500rpm/s
Dec: 200 to 500rpm/s.

Please note the 2130S controller works nice, it ramps down correctly before reaching the final position, following a trapezoidal motion shape. This issue is only in the 1130 driver.

The SDC1130 is v1.4b 03/31/2015

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5 years 1 month ago #29531076 by roboteq
This is most likely due to your desired speed be higher than your motor's maximum physical speed.

Look at the Motor Power, Tracking and Loop Error in the chart.

The Tracking shows the counter value the motor is expected to be at this precise instant. Loop Error is the difference between tracking and the actual counter position. If the loop error is greater than a few hundred counts while motor power is at 1000 (ie 100%), this means that the motor is running as fast as it can, but can't keep up with the Tracking. If that is the case, you will need to reduce the desired speed.

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5 years 1 month ago #29531077 by davidk
I used the same motor test setup with both controllers and they had the same setup values (I guess). The motor can reach 1500rpm in open loop 100% power and I set 1000rpm in my closed loop test. As I said, on the SDC2130 it works perfectly. I also lowered the Position Mode Velocity to 500rpm and still stops suddenly. You can see the attached picture.
Attachments:

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5 years 1 month ago #29531078 by TechSupport
Please try this firmware. It's the last validated release.
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5 years 1 month ago - 5 years 1 month ago #29531079 by davidk
The issue is the same, I tried this older firmware.

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5 years 1 month ago #29531089 by TechSupport
We will investigate.

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5 years 1 month ago #29531090 by TechSupport
Unfortunately I have a digital encoder so I can't replicate the problem as I need to get an absolute or optical encoder for position mode.

The SDC1130 has a different MCU which is a little slower(clock) than the mcu used in the SDC21xx controllers which may be the cause of the problem.

Is this something you are looking to use in production use?

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5 years 1 month ago - 5 years 1 month ago #29531091 by davidk
I use an incremental encoder on the motor shaft. It has 500ppr and I never exceeded 1000rpm in my tests. I can send you the config I used. Or the log of a motion with the wrong stop ramp.

Of course, I could use a lower ppr encoder, but I've noticed sudden stops even at lower maximum speeds -e.g.200rpm max so I guess it will do the same even at lower pulse speeds.

I will use this driver to control motion of a TV track dolly. I found that the other closed loop position modes aren't suitable for this application, since positioning is not that accurate. This system has high inertia for the 300W motors I use so I really need reliable ramping.

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5 years 1 month ago #29531099 by TechSupport
Incremental encoders are for speed. Absolute and optical encoders are for position.

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5 years 1 month ago #29531109 by davidk
My encoder is a quadrature optical encoder, not a tacho. Shouldn't it work in this setup? I really can't see the error. This identical setup works with the other driver, as I said.

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