Magnetic rotary sensors bringing in the harvest

November 17, 2014 //By Stefan Sester, Novotechnik
Magnetic rotary sensors bringing in the harvest
The demands placed on sensor technology are ever increasing - not only for industrial automation, but also for mobile applications, such as mobile agricultural machinery. Consequently, the demand for non-contacting rotary sensors is increasing. And frequently, magnetic processes are favored. They are reliable even under tough environmental conditions, they yield absolute measurements over the entire 360° range, and they can easily be adapted to the desired application. Their relatively low cost in comparison to other measurement technologies makes them suitable not only for countless applications in machine engineering and plant design but also for mobile applications, such as the one described here.

The Big Bale Transtacker is a piece of agricultural machinery that can be utilized to efficiently collect and stack in the field different sized bales of straw or hay. This machine is pulled and driven by a tractor, and also operator-controlled from the tractor.

Fig.1: The Transtacker simplifies the collection and stacking of bales of straw and hay in the field, as well as their transport and storage on the farm.

When the driver uses the joystick to activate the loading mode, for example, the bales of hay are grabbed by the lateral forks of the Transtacker. They are then stacked onto a swiveling turntable, where they can also be tied for better cohesion. This feature, as well, is activated by the operator with the push of a button on the control panel.

Once the table is full, the bales are pushed onto the load bed. While driving, the table is placed into the vertical position, where it secures the load. In order to switch to “Road Mode“, the operator just needs to move the forks into their road position; which - of course - happens with another push of a control panel button. Upon arriving at the storage facility, the load bed can be tilted. The turntable is utilized to off-load and place the bales. It can also be used to help pick up and reload them. The driver does not need to leave the tractor's cabin for any of these tasks.

For a smooth, reliable, and safe workflow, the positions of the rotational joints of pickup fork and turntable mechanism need to be sensed, and the positional data have to be sent to a control unit, so that it can initialize the subsequent steps of the task. “For this reason, the Transtacker’s design features several rotary sensors explains Alex Baylis of Big Bale Transtacker. However, it took some time to arrive at the proper choice."

Fig. 2: Central features of the Big Bale Transtacker are the pickup forks and the turntable

“Unfortunately, following the 2012 harvest season, we experienced some reliability issues with our Transtacker,” Alex Baylis continues. One reason was the choice of Hall Effect-based sensors. The were not up to the tough conditions at the point of use. There were issues with water resistance, for instance. “Furthermore, we were not happy with the accuracy, and on top of it, we found the solution too expensive as well,” adds Alex Baylis. “During the optimization stage, we then discovered the magnetic rotary sensors of the RFC 4800 series by Novotechnik.

Fig. 3: For a smooth, reliable, and safe workflow, the position of the rotational joints of pickup forks and turntable mechanism needs to be sensed, and the positional data have to be sent to a control unit. For this reason, the Transtacker's design features several rotary sensors.

Not only did their high precision and the standard IP69K degree of protection convince us, but also the favorable cost-benefit ratio as well as the dual-component design, which was very helpful when it came to retrofitting.”

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