and good robustness across different pig farm constructions, lighting conditions, age of the animals and skin colour.
Algorithms for climate control The machine vision technique was further used to develop al- gorithms for climate control within the pig barn. The adapted control strategy allows continuous measurement and cross- examination of process parameters by measuring the differ- ence between the real time data collected via non-invasive devices. Environmental sensors and cameras, and the refer- ence data known as the set points, have been used to further adjust and optimise the control mechanism. For instance, in a pig barn at a room temperature of 21°C, the visual sensors recognise that the pigs are lying far apart from each other even when the set point of 21°C is reached, indi- cating that the conditions are still too warm for the pigs. That information is passed to the controller, which then decides the action for the ventilator. As the controller has defined set- tings for the pigs’ lying pattern, it will prompt the ventilator to open further to allow air circulation. It will maintain this action until the visual sensors trigger the next signal that the lying pattern of the pigs is back to normal. This closed loop control strategy is also known as the model reference adaptive control system. In addition to the defined control settings, definition of fail-safes is also currently under development, for example, temperature over-riding the dy- namic control if the set limits are reached, air composition over-riding dynamic control and/or temperature if the concentration of noxious gases is too high.
Images, gases and climate sensors The control model is run through an open source single board computer (Raspberry Pi) based programmable logic controller (PLC) system as the core element of the described system. The input parameters (image recognition, sensors for noxious gases and barn climate sensors) are transferred to the PLC though mentioned input module extensions, where they are processed and then an output signal is generated which is further transferred to the ventilator via an output module extension. Visualisation of the current system condi- tions as well as the ability to change settings is realised through an industrial touch display built into the control cab- inet. Both the display and the control cabinet are suitable for use in agricultural environments, as they withstand dust and water penetration, meeting the IP65 standard. If needed, the system can also be extended with a wireless or ethernet network connection which provides the opportunity to supervise the current system state from a distance, not only directly at the control cabinet. The developed system can be used (with some modification) for other livestock farming climate control systems.
* Authors Sturm, Raut, Kirchhofer and Nasirahmadi are at- tached to the University of Kassel, Germany; authors Müller and Kirchhofer are attached to the Thuringian State Institute for Agriculture and Rural Development, Germany. Professor Sturm is also attached to the Leibniz Institute for Agricultural Engineering and Bioeconomy and the Humboldt University of Berlin.
▶PIG PROGRESS | Volume 36, No. 9, 2020 31
A camera – like the one used here in a dairy cow house – can be a great moni- toring tool for all types of livestock.
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