Weighing and classification of poultry
Improving reliability in a process with speeds close to 2 chickens per second has challenges when the original equipment limits are reached. Learn how we do it increasing our client’s confidence on its classification process.
A client of the poultry industry asked VIDAL & ASTUDILLO for a solution to adapt a sorting line to process birds in 12 different ranges, establishing the weight of 2 birds every second, requiring a reliability greater than 95% with an accuracy of ± 12 grams in each unit. For cost considerations, the machine should retain its original structure, including its weighing system. The original electronic control was replaced by several companies, until implementing a control based on Siemens Simatic S7-200 PLC with an OPC interface to PC for the recording of operation and supervision data.
However, the machine did not present a uniform behavior in its results. VIDAL & ASTUDILLO was able to establish that this was mainly due to the fact that the events associated with the control of the machine were not predictable and that the current system was not designed to deal with them in those circumstances. Examples of this type of event involve the reading of an analogous load cell which must be carried out at the precise moment in which the bird passes through an exact point on the weighing platform, and the actuation of the 12 pneumatic actuators in charge of unloading. each chicken according to its weight range. All associated elements present non-uniform operating conditions due to the circumstances of the process (size of the birds, speed of the process) and the wear of the machine (elongation of the chain that transports the birds, physical distribution of the discharge points, electrical fluctuations).
VIDAL & ASTUDILLO decided to delegate the PLC exclusively as a bridge between each of the components of the machine and an application developed entirely in LabVIEW that is in charge of controlling the machine.
In this way, the PLC is dedicated to informing the control application about events such as the weight registered by the analog load cell at the precise moment in which it should be taken and the signals of photo switches distributed along the weighing line that identify the precise location of the passage of birds. In the same way, the PLC receives the commands from the control application when it is required to actuate the unloading mechanisms of the birds.
This operating model, based on the ability of LabVIEW to process parallel cycles, allows the machine to manage the associated events as they occur, while still sharing common data between the cycles and ensuring that collisions are avoided in the manipulation of the data (or “Race conditions”), for which the control-based model previously implemented in the PLC was not designed.
Value for the customer
Apart from achieving a definitive and reliable solution to his classification need, our client found an opportunity to obtain information that allows him to accurately monitor - for each bird - the weight distribution of the different product batches that are finally related. with their production farms. This is made possible by an implementation in which LabVIEW records the pertinent information in a PostgreSQL database.
On the other hand, motivated by the reliability of the solution, it led our client to expand the classification ranges from 12 to 15 , with which he can deliver birds with the appropriate size to their needs.
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