data sampling motor

AmazingNoob · Aug 27, 2016

Hi there, i am looking for a method to sample 600 points on a motor that is running at 800 rpm or sometimes at 1000rpm. Then, i would like to calculate the average speed for every cycle.

The scan time of the plc is about 2 ms.

I have tried various ways, but the position of my 1st index is always starting at different angles.
I would like the 1st data position array to start collecting close to when the motor is at 0° and the last data position array to be close to 359/360°.

Could somebody help me with a pseudocode?

robertmee · Aug 27, 2016

What are you trying to 'sample'? The position of the motor? Or the instantaneous speed? If speed, I guess you are wanting to start at position 0 and end at 360, collecting speed points along the way? If so, what are you calling zero? A particular position of the motor shaft? It's not clear what you are really after.

AmazingNoob · Aug 27, 2016

robertmee said:
What are you trying to 'sample'? The position of the motor? Or the instantaneous speed? If speed, I guess you are wanting to start at position 0 and end at 360, collecting speed points along the way? If so, what are you calling zero? A particular position of the motor shaft? It's not clear what you are really after.

I am looking to find the average torque, and speed of a motor for every cycle.
My motor perform with different torque at different angles.
I am looking to collect it in a cycle so I can calculate the average torque per cycle, rather than per 1.25 cycle, or 1.5 cycle.

i would preferably sample it this way:
data.position[0] = 0.0
data.speed[0] = 100.0
data.torque[0] = 900.0

data.position[1] = 0.0
data.speed[1] = 100.0
data.torque[1] = 850.0
....
data.position[600] = 359.9
data.speed[600] = 100.0
data.torque[600] = 500.0

Geoff White · Aug 27, 2016

Are you calculating speed or reading it?
Are all the points from a single cycle? You sample has two points at the same position with different torque.

Your scan time does not allow much resolution. At 1000RPM a cycle takes 60ms.

You really need to define your problem better.

Mickey · Aug 27, 2016

Just curious, what PLC do you have that has a scan time of 2 ms?

AmazingNoob · Aug 28, 2016

Geoff, yup looks like I can only collect 30 points. Which means if I have 600 points, that would be 20 cycles.

Sorry for confusions.
The goal:
1. Get multiple plots on torque vs speeds curves for every cycle.
2. Calculate average speed, torque, current consumed.

Couple of ideas. Came up I guess.
I guess I can just let the scan colllect all the 600 points, then calculate average at 20 strokes to get more accurate.

Whereas for the plot, I'll have to live with 30 points if it is actually running at 1000 rpm.
1000Rpm was the worst case explain, typically the speed range 200-700rpm.

Mickey,
Am using a beckoff controller.

shooter · Aug 29, 2016

at 600 rpm it takes 100 ms/rev so only 50 samples max in one cycle.
A real time system will be needed, or a NOT PLC type like an arduino, a lot faster, and easy to program, and cheap.
please be aware that the sensor also needs to be fast, to get reliable measurements.
a scope would be a good choice here with a trigger sensor.
also be aware of forces related to position and the accuracy of the electric motor.

osmanjdt · Aug 29, 2016

GOOGLE

www unipulse com/en/products/TM500.html

shooter · Aug 31, 2016

you will have a problem anyway as the position sensor is very fast, so your sampling point is always different, so not correct way, check my other reply.

AGill · Aug 31, 2016

Curious about the application. Academic?

michev · Aug 31, 2016

If your using an encoder with a Z pulse, that can be used as your 0 reference and then use the pulses to find your locations around the cycle.

kamenges · Aug 31, 2016

Is your cycle a single motor revolution or is there gearing involved? Does the drive have an an EtherCat interface? If so, does it have internal data capture capability? Beckhoff also has high speed analog input modules but you still have the issue of triggering a data capture base on position.

Keith

Peter Nachtwey · Aug 31, 2016

This should be done by the motion controller. Motion controllers can sample at regular intervals of 1 ms or less. The data would be collected as a function of time but it is easy to interpolate to get data as a function of position.

data sampling motor

AmazingNoob

Member

robertmee

Lifetime Supporting Member

AmazingNoob

Member

Geoff White

Member

Mickey

Lifetime Supporting Member

AmazingNoob

Member

shooter

Member

osmanjdt

Member

shooter

Member

AGill

Member

michev

Member

kamenges

Member

Peter Nachtwey

Member

Similar Topics