Switching controls in hydraulic drives

Researchers from Johannes Kepler University believe agricultural machinery can be improved by further advances in motion generation.

Proper adjustment of plow geometry is a challenging handling operation for the operator of plowing and hay-harvesting machines. The optimal values depend on the actual ground situation, which may vary. To adapt the parameters to the ground optimally, adjustment is necessary rather frequently, which realistically can be done only via remote control, or, even better, with automatic control. Current practice is to adjust manually by spindles and to use some complex kinematic mechanism to get an uncoupled relation between the position of the spindles and the relevant functional plow parameters. With full automatic control, easier operation and optimal results-both with respect to quality and performance-can be achieved.

The mechanical performance characteristics of modern hay harvesters and tractors allow operation speeds of about 30 km/h (18.6 mph). At such high speeds, the driver cannot do all the necessary control. The most endangered machine part is the harvester's pick-up device, which can be damaged if it crashes into obstacles such as big stones. The rollers or sledges from which distance to ground is adjusted introduce a further complication. Even at today's operating speeds, the winding of hay around the rollers sometimes disturbs operation or damages the sward. To eliminate problems, the pick-up should be guided at a certain distance above ground by some automatic level control without mechanical contact. For high speeds, this level of control has to assure that damaging contact with obstacles is avoided by lifting the pick-up right in time. Realization of this function needs an automatic detection of distance-to-ground and of obstacles in combination with some fast response positioning drive.