One of the first applications that springs to mind when speaking about precision agriculture or smart farming is navigating machines that drive on the fields for automation and efficiency. These can be harvesters, combines, fertilizers, ploughs and more. Most of these machines have an accurate GPS system, which allows the driver to know the location of the vehicle and to prevent double fertilization or missing a spot. However, there are several limiting factors to GPS that can be easily solved using IMUs or AHRSs. Xsens is one of the leading innovators in this technology, the MTi 1-series IMU/AHRS is designed with the precision agriculture developments in mind.
Compensation for antenna placement
The GPS antenna on agricultural vehicles is placed on top of the vehicle. With the height of the vehicle being more than several meters and the terrain being uneven, the discrepancy between the phase center of the antenna and the exact location of the vehicle on the ground can be tens of centimeters. Tilting or pitching 5 deg at a height of 4 meter yields a discrepancy of 35 cm. The GPS systems used in agriculture typically have accuracies of 1-5 cm, so determining the pitch and roll is a necessity.
Accurately steering a 180 deg turn
When going over the field, the machine drives a straight line up to the side of the field, then makes a 180 deg turn and drives a straight line back. Making the turn of 180 deg is something that cannot be determined with the GPS at the time of the actual turn. In order to determine heading with GPS, there must be a translating movement (a rotational movement on the spot is not sufficient). An IMU or AHRS, such as theMTi-1, is excellent for this purpose and can bring the vehicle on the new track.
Although not very likely as crops need sun, there is the change of foliage on or around fields. This will result in GPS outages. These GPS outages can be compensated for with an IMU or AHRS. A smooth transition between the GPS position and the position in the GPS-denied environment is crucial. The Xsens IMUs offer timing and synchronization options, so that data can easily be merged.
Another interesting field of interest are drones. Airplanes are used in various situations, though mainly for fertilization. Drones offer the possibility to fertilize the crops after examination of the individual plants. For example, size and color can be determined, so that the right amount of fertilizer can be applied. This will result in a lower use of fertilizer and healthier food production. The MTi 1-series is an excellent product for drones navigation and stabilization. When pointing the camera to the ground, it is necessary to know what the camera is filming. At a height of 10 meters, an error of 5 deg results in a 90 cm error. This can be the difference between the different rows.
Food dispensing Cattle in barns can receive their food in the paths between the areas for the animals. Sticking their heads through the fence, they can reach the hay that it is piled up against the fence. However, while eating, the hay will be pushed away from the fence so that the cattle can no longer reach it. A farmer will be needed to push back the hay towards the fence. In larger barns, this is more and more being automated, where an unmanned ground vehicle (UGV) with a rotating hood swipes the hay to the fence. For the navigation and the correct distance from the fence, the UGV carries an IMU amongst other sensor systems.
Barn cleaning On the other side of the fence, the cattle will defecate which will result in a slippery and dangerous floor. In order to remove this, a robot will sweep the barn and remove the excrements into the floor or drains. An IMU is essential to keep track.
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