Conveyor Product Tracking

I'm a newbie to tracking concept. I have assigned a project to handle product tracking. Product should be delivered to destination without any lost.
Few parameters need to be considered Conveyor Length, Encoder(Using U sensor), Photo Electric Sensor(Only @ Head of Conveyor).
My questions how to generate ID, how to track product and how to transfer id to upstream conveyor.
AB PLC
Your inputs will be highly appreciated.

1. Use a barcode scanner. When product package is seen by Photo Electric Sensor @ Head of Conveyor, the barcode scanner device is triggered, and reads the character code to PLC memory. This barcode determines how product is routed.

2. To transfer the product ID code to an upstream conveyor, you could use a "First In FIrst Out" PLC memory stack. Many PLCs have an instruction that performs the FIFO operation. Another way is to use a Bit-Shift Register.

Is there a barcode? you don't mention one.

If not, how do you know whe difference between packages and where they should go?

Is there a divert system for routing?

A lot of information missing.


basic tracking using an ID.

1. Decide the tracking zone (usually starts and ends at a photoeye, other photoeyes maybe in between).

2. Every conveyor in the tracking zone (including the start photoeye conveyor) should have a pulsed signal (encoder or proximity on starwheel), each rising and falling edge would equate to a definitive movement. This would need to be calculated or tested by running an object between to sensors and counting the pulses.

3. Decide how many objects can be in the zone, the tracking ID range would need to be at least 1.5 times the number of objects.

4. An array or number of arrays (one for each conveyor) should be in the PLC, the number of positions should be 1 for each pulse expected on the conveyor.

4. When an object is detected at the first photoeye, assign the next tracking ID (if there are 100 ID's allocated then the ID would start at 1 and increment for each object until 100 is reached, then back to 1). Put that ID in the first position of the first array.

5. Each pulse shift the ID along 1 position.

6. If an object is detected at a sensor, check the array around where that sensor is expected to look for the id, normally allow a few up and downstream as a tolerance.

7. If an ID exists, re-position it at the expected position and continue moving.

8. When it reaches the end of the array, move it to the next (passing to next position).


Its up to you how you want to handle lost objects or unknown objects.


An ID would only be needed if you were holding information with the object, if you just wanted to know where an object is, you could follow a bit rather than an ID.

1. Use a barcode scanner. When product package is seen by Photo Electric Sensor @ Head of Conveyor, the barcode scanner device is triggered, and reads the character code to PLC memory. This barcode determines how product is routed.

Click to expand...

We already using Barcode scanner to read product and its destination

2. To transfer the product ID code to an upstream conveyor, you could use a "First In FIrst Out" PLC memory stack. Many PLCs have an instruction that performs the FIFO operation. Another way is to use a Bit-Shift Register.

Click to expand...

Let me try this
Thanks Lancie1

The FIFO instruction is NOT recommended, unless you include actions for missing and unexpected objects.

Is there a barcode? you don't mention one.

If not, how do you know whe difference between packages and where they should go?

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Sorry Peter, I forgot to mention that we are using bar-code scanner to read product and its destination.

Is there a divert system for routing?

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Yes, We are using divert system to reach different destination.

1. Decide the tracking zone (usually starts and ends at a photoeye, other photoeyes maybe in between).

We have Photoeye only @ end of the conveyor.
System cannot be modified.
Before entering tracking zone, feeding conveyor will pass generated ID tracking conveyor.

2. Every conveyor in the tracking zone (including the start photoeye conveyor) should have a pulsed signal (encoder or proximity on starwheel), each rising and falling edge would equate to a definitive movement. This would need to be calculated or tested by running an object between to sensors and counting the pulses.

Click to expand...

I'm calculating both rising and falling edge of encoder

3. Decide how many objects can be in the zone, the tracking ID range would need to be at least 1.5 times the number of objects.

Click to expand...

I'm going to test only so only one object

4. An array or number of arrays (one for each conveyor) should be in the PLC, the number of positions should be 1 for each pulse expected on the conveyor.

Click to expand...

Peter, I'm not familiar with Array and Pointer system, How to do simple program using this system. I know that Array is a table where you can input data but how this works. Searched google unable to find right resource for array system.

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Conveyor Package Tracking in RSLogix500

Let me try this. Thanks Lancie1

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I would use a Bit Shift Register, and because you are using Allen Bradley, use the BSL instruction for each diverted lane. Here is a copy of a RSLogix500 package-tracking and diverter program that has one main conveyor (actually a series-string of conveyors tied to the same encoder at the head) and 10 diversion conveyors (#10 is a reject line). The main conveyor has a photoeye and barcode scanner just before the head, with diverter gates at the take-off points for the 10 sorting lanes. Each barcode contains a number from 1 to 9. If a barcode cannot be read, or if a package does not get diverted for some reason, it ends up in Lane 10.

Lad 5 SORTATION contains the Bit Shift Left instuctions, and Lane 1 BSL is on Rung 0023 in the Lad 5 PDF file-print. The ZIPped file is the complete RSLogix500 program.

I'm trying to picture your system.

You have a bar code reader, at least 2 conveyors (as you ask how to pass the id between conveyors), at least one divert and only 1 photoeye.

Questions.

1. Does the barcode tell you the route (divert or not).

2. How?, is it the code (for example ends with a 1 = divert) or do you have another system that you send the read barcode to that tells you which way.

3. Is there any other info that is stored with the barcode that needs to be passed on with the id.

4. For testing you say there will only be one object, is this how it will be in real life or will multiple objects be within the zone?


Lancie's bit move will only be good for you if all you want to track is the timing for the divert.


An example of what I have seen and done at airports.

a. A bag approaches a divert, is seen at the first photoeye of the tracking zone. The next tracking ID is assigned (in this example I will say 20).

b. One UDT area in an a array of UDT's, offset to position 20 is set to default values.

c. 'x' pulses later the barcode reader is enabled.

d. The barcode reader reads the codes.

e. 'x' pulses later the PLC 'listens' for a barcode result. The PLC will only listen for a set amount of pulses, after which any response will be ignored.

e. A code is received within the 'window', the result is placed in the array of UDT's, offset to position 20.

f. The ID and barcode is sent to a high level system.

g. Before reaching the divert, the ID, and destination is sent to the PLC, the destination is placed in the array offset by 20

h. When the ID 20 reaches a position in the tracking zone the divert destination is read from the array. the divert will be commanded to assume the desired position.



In between there will be sensors at the end of every conveyor that re-syncs the position.

Software logic is included to ensure the bag is detected when expected within a tolerance, if not then the bag is lost, any bag seen outside the tolerance will be unknown and treated at the divert with a pre-determined response.


The software can be quite complicated, depends on how critical it is to be certain the object is the right object and how many checks you need to put in place to ensure this.


I don't have a picture in my mind of what you are tracking, how long the tracking zone is, how many objects in the zone, how many diverts, how many conveyors.

If more than 1 conveyor you will need more than 1 photoeye.

Peter, that's really great.
I'm also into BHS.
sorry about not giving enough information, Since this system is new to me.
So I find quite difficult for me to understand.
Barcode read manually as well as by ATR.

I'm going to test only so only one object

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Backtracking a little, if you only ever have one object or package or box, and have a conveyor encoder and barcode scanner but only one photo-switch, then you don't need any elaborate program.

1. Measure encoder distance to next upstream conveyor diverter point (or calculate encoder reading to transfer conveyor based on measured physical distance).
2. When photoswitch sees package, read barcode label and determine how far to the diverter point. Move the preset distance-to-transfer to a Counter Preset.
3. Trigger counter with encoder. When counter = preset value, trigger the diverter and move the barcode ID to the next upstream conveyor.

That is if you know for sure that there will never, ever in a hundred years be more than one object on the conveyor at a time (not the usual situation). If you do have more than one, then you will have to stack them in PLC memory in order and pull them off at the right places. That gets you back to some type of PLC memory stack.

Lancie1 said:

Backtracking a little, if you only ever have one object or package or box, and have a conveyor encoder and barcode scanner but only one photo-switch, then you don't need any elaborate program.

1. Measure encoder distance (or calculate encoder reading to each diverter based on measured physical distance).
2. Read barcode label and determine which diverter to trigger. Move the preset distance-to-diverter to a Counter Preset.
3. Trigger counter with encoder. When counter = preset value, trigger diverter to kick off object.

That is if you know for sure that there will never, ever in a hundred years be more than one object on the conveyor at a time (not the usual situation).

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BHS is an airport baggage handling system. I think he's saying he's going to test with one object, but from experience in a real BHS the travel distance would be at least 15 feet and multiple bags will be on the conveyor travelling at speed.