With the 'Photoheyler' hoeing system, Planungsbüro Heinrich has established a new 'hoeing order' in the mechanical weed removal market: With an area output of more than one hectare per hour, crops can be hoed from the two-leaf stage to the beginning of row closure. The hydraulically driven rotors, which remove the weeds from the plant row, compensate for the driving speed of the agricultural machine in such a way that the crops - for example sugar beet - are not damaged or buried by soil moving in the direction of travel during vertical plant cutting.

Absolute encoders from Sick's 'AFS60 Ethercat' product family support the dynamic position detection and speed recording of the twelve individually path-controlled hoeing rotors on the attachment. For this purpose, the encoder was adapted from its original industrial purpose to the agricultural application of the photoheller.

Prepared for field work

Inox encoders from the AFS60 Ethercat product family with IP67 protection are perfectly designed for agricultural applications.

© Sick

In order to consistently design the sensor for field work on the photoheyler and possible other applications in the agricultural environment or other heavy-duty applications, Sick redesigned the sensor together with the customer: The aluminum housing gave way to a stainless steel housing. The socket/plug connection was also modified to achieve better sealing efficiency. The protection class of the flange side of the housing was also changed to IP67 to prevent moisture from penetrating via the encoder's ball bearings. This is how the 'Agrar-AFS60' was created.

Weeding made to measure

Depending on the version, the Photoheyler can hoe more than a dozen rows of plants simultaneously and thus remove weeds. In order to distinguish between the two, a traveling image processing system was developed which, according to the Heinrich planning office, achieves detection rates of over 98%. At the same time, the cameras measure the distance between the crop plants for each planting row, as different planting distances can occur during the course of growth, even with uniform mechanical sowing.

To ensure that the weeds can be removed accurately, each individual rotor must be controlled in an individual path curve. This in turn requires a separate encoder for each hydraulic drive on the attachment, which provides fast and precise position and speed measurement values for controlling the hoeing rotors. With a singleturn resolution of 18 bits, the space-efficient absolute encoders from Sick provide the accuracy required for 360° position detection and precise control. In the Ethercat version, they also enable cycle times of 4 ms in order to achieve the necessary control dynamics for the individual braking and acceleration of the rotors.

The author: Martin Hummel is Product Manager Encoder / Motion Control Sensors at Sick in Donaueschingen.

© Sick

The example of this encoder shows that products and systems from the existing portfolio can be modified for a wide range of new applications through customizing. This means that encoders are available for the technology and automation of agricultural machinery that can measure the rotational speed and speed of moving, mostly rotating parts of agricultural machinery. They can also detect the position of movable components and attachments and thus optimize soil cultivation or harvesting processes, for example, and are able to support the control of autonomous steering and driving systems.