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from Turbo Pmac2 to Geo Brick
#1
hello,

I have a code that works fine in a rack with,

Turbo Pmac2, ACC-84E for BISS reading, and ACC24E2S to control stepper motors.

Since I'm only using 6 axis, I was thinking about buying a Geo Brick with 8 axis instead of buying the 32-axis TurboPmac 2.

Do you think there is going to be any problem with running the code I have for my last aplication?

Thanks
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#2
The answer to your question is not a simple Yes or No since Serial Encoder Input lines and Pulse&Direction output lines on Brick products, use the same pins on the connectors.
Please specify exactly what hardware you're using at the moment, specifically the quantity for each accessory and number of channels which are used on each accessory, before we can suggest a different form factor for your application.
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
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#3
(03-28-2014, 08:38 AM)Sina Wrote: The answer to your question is not a simple Yes or No since Serial Encoder Input lines and Pulse&Direction output lines on Brick products, use the same pins on the connectors.
Please specify exactly what hardware you're using at the moment, specifically the quantity for each accessory and number of channels which are used on each accessory, before we can suggest a different form factor for your application.

This is a list of the components I have:

1.-Turbo PMAC2 CPU
2.-ACC24E2A
3.-ACC24E2A
4.-ACC24E2A
5.-ACC51E
6.-ACC84E
7.-ACC84E
8.-ACC84E
9.-ACC84E
10.-ACC28E

but I'm only using two cards ACC84E to read encoders BISS and two cards ACC24E2S to move stepper motors.

All the wires can be redone. I'm only asking if the actual code can work on both platforms without having to make any syntax changes.
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#4
jxreyes181,

Your code can be ported without any modification to your logic, however, some addressing for registers, such as the address for serial encoder register will be changed since the addressing differs from one form factor to next.

Assuming you're using 2x ACC-24E2S (8 channels) to send pulse and direction commands to stepper motor drivers and use 2x ACC-84E (8 channels) to read BiSS C encoder feedbacks, then we can't support this combination in Brick form factor since all steppers pulse and direction outputs and serial encoder inputs are sharing the same pins on X1 through X8 connectors.
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
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#5
Sina,

Thanks for the answer.

What about combining Renishaw BISS/C abs. encoders with DC Servo motores. Is it posible to control 6 axis in a close loop with this two?

Thanks!
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#6
jxreyes181,

Have you considered whether you want to use a 3rd party amplifier for your stepper/DC Servo motors or you want to use Delta Tau's integrated Controller/Amplifier? If you choose Geo Brick LV or Power Brick LV, you can have up to 8 BiSS-C encoder feedbacks with integrated amplifier which is capable of controlling stepper, brush and brushless motors. This will simplify your design tremendously since all the connections from controller and amplifiers are internal to Geo Brick LV.

Please see the following page for more information on Geo Brick LV:
http://www.deltatau.com/DT_Products/Prod...BRICK%20LV
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
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#7
Sina,

I'm thinking about using the integrated Controller/Amplifier of Geo Brick LV. (Power Brick LV is coming soon, but not yet available on the web page).

Just one question:

I have a 3 fase DC-Servomotor with integrated Hall sensor.
This motor moves a axis that is monitored by a BISS-C absolute encoder.

Can I forget about the Hall Sensor, and still accurately move the axis? I mean just not plug in the Hall Sensor.

Pardon my ignorance.

Thanks,
Juan Xavier Reyes
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#8
(04-02-2014, 02:50 AM)jxreyes181 Wrote: Sina,

I'm thinking about using the integrated Controller/Amplifier of Geo Brick LV. (Power Brick LV is coming soon, but not yet available on the web page).

Just one question:

I have a 3 fase DC-Servomotor with integrated Hall sensor.
This motor moves a axis that is monitored by a BISS-C absolute encoder.

Can I forget about the Hall Sensor, and still accurately move the axis? I mean just not plug in the Hall Sensor.

Pardon my ignorance.

Thanks,
Juan Xavier Reyes

I think I found the solution.

I would not use the hall sensors on my motor, instead use the absolute encoder and the procedure "Absolute Power-On Phasing: EnDat | SSI | BiSS" on page 186 of the "Geo Brick LV User Manual" to move accurately. Right?
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#9
You are correct.

(04-02-2014, 06:25 AM)jxreyes181 Wrote:
(04-02-2014, 02:50 AM)jxreyes181 Wrote: Sina,

I'm thinking about using the integrated Controller/Amplifier of Geo Brick LV. (Power Brick LV is coming soon, but not yet available on the web page).

Just one question:

I have a 3 fase DC-Servomotor with integrated Hall sensor.
This motor moves a axis that is monitored by a BISS-C absolute encoder.

Can I forget about the Hall Sensor, and still accurately move the axis? I mean just not plug in the Hall Sensor.

Pardon my ignorance.

Thanks,
Juan Xavier Reyes

I think I found the solution.

I would not use the hall sensors on my motor, instead use the absolute encoder and the procedure "Absolute Power-On Phasing: EnDat | SSI | BiSS" on page 186 of the "Geo Brick LV User Manual" to move accurately. Right?
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
Reply
#10
Hey Sina :), I'm Back.

I have been making some calculating in regards to controlling my DC-servomotor with the Geo Brick LV.

I have a very small motor: Inductance (phase-phase)=35uH and Resistance (phase-phase)=2.3Ohm

According with what on page 156 of the Geo Brick LV User Manual, that gives a time constant of T=15.2uSec and a PWM freq. of 209.175 kHz. I don't think Geo Brick LV can go that fast.

So, I was thinking of using a inductance in series with the motor. The inductance is: 2.7 mH and 8.9 Ohm.

With this, the combine inductance is 2.735 mH and the resistance is 11.2 Ohm. So T=244uSec and PWM Freq. is 13.034 kHz. With this we can use a 20kHz PWM Freq. and solved.

Will this work? What other problems could I encounter with such small motor?

thanks,

Juan Xavier Reyes
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#11
This will work. The only downside is the performance of the motor will only be as good as 2.735mH motor.
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#12
(04-04-2014, 12:17 PM)steve.milici Wrote: This will work. The only downside is the performance of the motor will only be as good as 2.735mH motor.

With performance you mean.... ? (loss of energy?) ..
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#13
jxreyes181,

Adding additional inductance as close as possible to Geo Brick LV, will not only provide enough inductance for the current loop closure, but also it will act as an edge filter for the PWM output of the amplifier, generating less heat in the motor coils. However, as steve.milici noted, adding inductance will reduce the bandwidth achievable compared to the theoretical bandwidth you could achieve if you had a 207kHz PWM frequency and a 414 kHz Phase frequency! If you can reduce the external inductance to a value of 1mH, you can achieve the highest capability of Geo Brick LV.
Note that for lower inductance motors (combination of internal and any added external inductance) it is suggested to use higher PWM frequencies (as high as 40kHz). Please keep in mind that if you increase your Phase clock higher than 30KHz, you need to change your ADC Sample Clock from 2.4576MHz to 4.9152MHz. (Adjustable using I7m04) in order to allow sufficient time for ADC data to be strobed in within half a phase clock cycle.
Sina Sattari
Hardware Engineering Manager
Delta Tau Data Systems, Inc.
Reply
#14
The added inductance limits how fast the current in the motor can change (di/dt = V/L). Sometimes a low-inductance motor is selected to achieve very high rates of change of current, and therefore torque.
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#15
(04-09-2014, 08:24 AM)Sina Wrote: If you can reduce the external inductance to a value of 1mH, you can achieve the highest capability of Geo Brick LV.

Hi Sina,

I am facing the same problem with PWM amplifier + low-inductance motor.

Motor:
Inductance line-line = 1.7 mH
Resistance (25 deg Celsius) line-line = 4.4 ohms

tau_sec = 1.7e-3 / 4.4 = 386.36 usec => minimum_PWM_f ~ 8 kHz

The PWM frequency is set to 20 kHz (maximum recomended value for my amplifier), and the open-loop noise (#1out0) is too big.
We tried to supress the noise by adding 1 mH inductance in series, which attenuated it but didn't achieved our stability spec. Then we tried bigger inductance values, but it didn't work very well.

How did you calculate the optimum value of series inductance?
What would be the optimal value for my scenario?

Controller: Power Brick LV (5 A / 15 A amplifier)


Regards,
Marcelo Moraes
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