Danitech, together with Fabercom, has developed a tracked harvester for harvesting flower bulbs. Since it is a tracked machine, the normal way to control this kind of machine is with two linear proportional levers, one lever for each track.
During harvesting, the customer often requires a cruise control function, to free his hands to be able to control the rest of the machine. In this cruise control mode, the speed of both tracks is regulated with one potentiometer. Both hydraulic valves are powered with the same current to send equal flows to both motors for the machine to go straight.
But also, during harvesting, the operator might want to make small curves or corrections.
Therefore, each pwm (pulse width modulation) output can be adjusted, from the cruise control potentiometer to each track, with an additional corrective value, from either the left or the right linear proportional lever.
On top of the potentiometer (cruise control) signal there is the possibility for a corrective signal from the left or right linear lever, either plus or minus, that enables the left or right track to go faster or slower. By doing so the operator can slow down or increase the speed of the individual tracks, making a curve, while the cruise control mode is maintained.
The corrective signal is not only proportional to the linear lever proportional value, but also proportional to the actual value of the potentiometer controlling the speed. This ensures that during all speeds, fast or slow, corrections are proportional to both speed and the corrective value of the linear lever.
“We have put the machine into work this spring and after some small adjustments the operator is really happy with the control,” says Folkert Stegenga, Project engineer at Danitech.