CAN Newsletter magazine
A working group, in cooperation with a company has developed a special lightweight stilts tractor with hybrid drive for biological pest control on corn fields. For controlling the machine, a CAN-based unit is used.
This article originally appeared in the March issue of the CAN Newsletter magazine 2019. This is just an excerpt.
Agricultural machinery must be optimally adapted to the conditions of use. Since no suitable machine was available for biological pest control on corn fields, a working group of the Institute for Mobile Systems of the Otto von Guericke University, Magdeburg in cooperation with the company Biocare has developed a special lightweight stilts tug. When controlling the machine, the machine builders rely on a control and operating unit from Graf-Syteco. The European corn borer is a small butterfly that is feared as one of the most important pests in maize farming by farmers. It is estimated that every year it destroys up to 4 % of the corn crop. An environmentally friendly biological method of combating the European corn borer by the parasitic wasp Trichogramma brassicae has proven itself as an alternative to the use of insecticides for many years. The parasitic wasps are parasites that lay their eggs in those of the European corn borer and prevent their development to the caterpillar so effectively.
The company Biocare offers so-called Trichosafe balls for application in the maize field, in which eggs parasitized by the parasitic wasps are contained in different stages of development. After application on the field, the beneficial parasitic wasps that fight the European corn borer develop over a period of up to three weeks. However, the effect of biological pest control depends on the balls being deployed at the right time. And at that time, the corn has already reached a height of about 1,80 m - the application of the balls with a conventional farm tractor is therefore no longer possible without damaging the plants. Since the effective amount of the biological agent is only about 100 global hectare, drones can be used to deploy the balls. For larger acreage Biocare has developed a pneumatic ball-thrower as an attachment that can be mounted on a high-leg self-propelled sprayer. However, these are clearly oversized for the small quantities and therefore too expensive for this application.
The working group of Prof. Stephan Schmidt from the Institute of Mobile Systems of the Otto von Guericke University, Magdeburg, is working on a practicable and cost-effective solution. The machine builders have developed a lightweight vehicle that optimally meets the requirements of the application and at the same time is very cost-effective. Since the required payload of the so-called stilt tractor and thus the required driving performance are very low, instead of a hydraulic an electromechanical drive can be used. Since a purely electric drive cannot cover the requirement for operation of 16 hours per day, a variable concept of backup battery and an internal combustion engine is used as a range extender. The internal combustion engine used in this serial hybrid drive has only a small power, which means an additional weight reduction. "The powertrain is comparatively easy. Overall, we were able to realize a very efficient special machine, " Prof. Schmidt explained.
The geometric requirements on the stilts tractor result from the use in the cornfield with a height of the plants of up to 2 m. The vehicle body with the driver's seat and the other components, such as the pneumatic ball thrower, must be located above the corn rows. The track width of the narrow stilts with the wheels and the drives must be adjustable so that it can be adapted to different row spacing of the maize rows. In order to prevent the stilts tractor from tipping over hilly terrain, a minimum track width of 4 m is necessary. On the other hand, the vehicle has to collapse to transport dimensions of 3,5 m x 2 m x 3 m. "That's how we make sure," Prof. Schmidt explained, "that the user can easily transport it from one corn field to another on a standard vehicle trailer." The backup battery and the range extender can be removed from the vehicle for transport. With a travel speed of 12 km per hour and a working width of the pneumatic ball thrower of 30 m, the stilt tractor has an area capacity of up to 30 hectare per hour.
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