| 摘要 |
A towed scraper control system automatically lowers the scraper blade to a working position at the start of a scraping operation according to a certain method. The method includes sensing a ground speed of the vehicle and sensing a draft force applied by the scraper to the vehicle. With the vehicle pulling the scraper at or near a target ground speed over terrain with the blade positioned above a surface of the ground, the blade is automatically lowered with respect to the scraper frame at a first rate until the blade begins to engage the surface of the ground. Thereafter, while the vehicle continues to move forward at or near the target ground speed, the blade is lowered with respect to the frame at a second rate and for a duration related to the sensed ground speed so that lowering of the blade stops when the scraper wheel begins to enter a cut produced by the blade. With the blade fixed with respect to the scraper frame, the scraper is moved forward at the target ground speed for a distance determined as a function of the sensed draft force. Thereafter, the blade is raised with respect to the frame at a rate which matches a lowering rate of the wheels as they descend along the cut, and the blade is raised at this matching rate until the position of the blade matches the position of the blade after the first lowering step. Preferably, the second rate is slower than the first rate.
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