PTO Servo control

[Frosty]

Hey All,

First off congrats on new forum, very fancy I like it, disappointed I had to create my profile again but, its OK.

Now, my problem is this; I'm using the PTO on O0 of my v570 to drive a Yaskawa SGMAV-02ADA61 motor via a Yaskawa SGDV-1R6A01A servo drive. I have the drive set up for position control and it requires a pulse train to move it. While i was waiting for my v570 to be delivered I used an AB Micrologix to test the PTO driving the servo, it worked like it should which was great. When my v570 arrived I noticed a difference, which was: Monitoring the pps (Pulses Per Second) on the Yaskawa software I saw 32000 when I set my Output Frequency to 32000 on the Micrologix, but when I set my frequency to 32000 on my v570 the drive was only seeing 3200 pps. Now i'm not sure if this an issue with the v570 or the way I've programmed it or the Drive, but if any of you may have an idea what the issue is I'd appreciate the feedback. One more thing I'm using the code from the PTO example.

Regards,

[Damian]

Do you have the output setup as PNP or NPN?

Are you using a function block in the ladder to control the pulse or are you using the dedicated feature in the hardware setup?

[Emil]

Hi Frosty,

V570 in fact has no I/O. It needs to be some Snap In module. Which?

Are you set it in PNP or in NPN mode?

How you give the frequency?

Please note - HSO/PTO in Snap In modules of V570 runs with 0.1 Hz resoluiton. This means - if you want to output 100 Hz, you need ot give number 1000.

Attached is a simple demo, which links HSO to HSC and enables precise (0.01Hz) measurement of the frequency, outputted by HSO.

Frequency-precise meter.vlp

[Frosty]

Hey Guys,

Thanks for the reply, I'm using the v200-18-E4XB snap on module, output set to pnp using the PTO function in hardware setup.

The frequency is given by linearisation for acc/dec and then a constant value for max speed. Same method as in example.

Since I posted my question I have resolved the issue by setting up a pulse multiplier in the servo drive, this has given me the desired effect on the motor so this issue is resolved in my opinion.

Thanks.

[Damian]

Hey Guys,

Thanks for the reply, I'm using the v200-18-E4XB snap on module, output set to pnp using the PTO function in hardware setup.

The frequency is given by linearisation for acc/dec and then a constant value for max speed. Same method as in example.

Since I posted my question I have resolved the issue by setting up a pulse multiplier in the servo drive, this has given me the desired effect on the motor so this issue is resolved in my opinion.

Thanks.

Hi Frosty,

Glad to hear you found a workaround. For future reference, the value you were using with a PNP output was too big.

This is a snippet from the Uni documentation:

You can use certain outputs as High-speed Outputs (HSO) via PWM (Pulse Width Modulation). When you select a High Speed Output in the Hardware, the Select Operand and Address dialog box appears three successive times, allowing you to link operands for the following values:

Duty Cycle

The ratio of the "on" period of a cycle to the total cycle period. This value may be from 0-1000, and is expressed as a percentage.

If, for example, the constant 750 is stored into the Duty Cycle operand, the duty cycle is equal to 75.0% This means that the pulse will hold a positive state during 75.0% of the total cycle.

Frequency (F)

Note that F=1/T, where T is the duration time of a complete cycle. Frequency settings differ from npn to pnp output type.

npn: You can use a value of 0, or a value from 8-50000Hz ( 50kHz).

pnp: You can use a value of 0, or a value from 8-2000HZ.

Other frequency values are not supported.

[dahnuguy]

Hi Frosty,

V570 in fact has no I/O. It needs to be some Snap In module. Which?

Are you set it in PNP or in NPN mode?

How you give the frequency?

Please note - HSO/PTO in Snap In modules of V570 runs with 0.1 Hz resoluiton. This means - if you want to output 100 Hz, you need ot give number 1000.

Attached is a simple demo, which links HSO to HSC and enables precise (0.01Hz) measurement of the frequency, outputted by HSO.

V350-35-T38

What is the difference between PWM using a HSO and PTO? I am playing with a PWM output now.

Looks like it works fine. But PWM is different from a Pulse Train for a servo.

I see a different area in the hardware config for PTO out and PWM out, but what block does one use for PTO in the software? 

Do we set up the output for PTO in the hardware config and then just use the same block in software as the PWM?

Also, what is the easiest way to convert the PWM out to an analog voltage? I was thinking of adding a resistor and a capacitor to the output terminal on the V350. WIll this be a problem for the V350?

[Damian]

V350-35-T38

What is the difference between PWM using a HSO and PTO? I am playing with a PWM output now.

Looks like it works fine. But PWM is different from a Pulse Train for a servo.

I see a different area in the hardware config for PTO out and PWM out, but what block does one use for PTO in the software? 

Do we set up the output for PTO in the hardware config and then just use the same block in software as the PWM?

Also, what is the easiest way to convert the PWM out to an analog voltage? I was thinking of adding a resistor and a capacitor to the output terminal on the V350. WIll this be a problem for the V350?

On the later, when done in the hardare setup, you can generate a pulse without really having anything in the program. No function blocks necessary.

Easiest way of converting PWM to analog is in the software. Provided you have an available hardware analog output.

If you are trying to make a cheap and dirty analog output using a digital output, there are many pitfalls. It would kind of work provided you required very crude accuracy and the input inpedence of what you were feeding is very high, and the resistor used was sized large enough to keep the instantaneous current well within the range of the output transistor. Then you have to consider the "filtering" effects of the RC combination and what that does to the response time between when a change is made to the PWM signal and when that change settles out on the output.

Unless you are stranded on a desert island and have no other way, it probably isn't worth it.