Work vehicles such as a bulldozer and a motor grader include a blade for excavating soil.
PTD 1 discloses a work vehicle including a pair of lift cylinders for moving a blade upward and downward and a pair of pitch/tilt cylinders for tilting the blade forward and backward.
In a work vehicle, it is possible to tilt a blade forward, backward, leftward, and rightward by driving both or one of a pair of pitch/tilt cylinders. However, it is necessary to control a position of the blade to perform excavation efficiently.
For example, even when a blade is lifted to a reference height, if the blade tilts forward significantly, an edge of the blade digs into a ground surface, so that excessive excavation is performed. On the other hand, if the blade tilts backward significantly, the edge of the blade is separated apart from the ground surface significantly, so that sufficient excavation cannot be performed.
On this point, four stroke sensors provided respectively to a pair of lift cylinders and a pair of pitch/tilt cylinders can detect stroke amounts to identify a position of the blade.
On the other hand, since stroke sensors are generally expensive, it is preferable that the position of the blade can be identified with use of only two stroke sensors for detecting stroke amounts of the pair of lift cylinders.
According to the work vehicle of PTD 1, a method of automatically controlling a position of the blade based on stroke amounts of a pair of lift cylinders is disclosed.