ass日本风韵熟妇pics男人扒开女人屁屁桶到爽|扒开胸露出奶头亲吻视频|邻居少妇的诱惑|人人妻在线播放|日日摸夜夜摸狠狠摸婷婷|制服 丝袜 人妻|激情熟妇中文字幕|看黄色欧美特一级|日本av人妻系列|高潮对白av,丰满岳妇乱熟妇之荡,日本丰满熟妇乱又伦,日韩欧美一区二区三区在线

A tractor electro-hydraulic control system was designed and studied based on the plowing depth system's principle of tractor hydraulic hitch mechanism. An electro-hydraulic proportional valve was used as the master valve in this system. The mathematic model of the tractor electro-hydraulic control system was set up and then the characteristic of load control and position control was analyzed. Finally experimental research was performed. The experimental results showed that transient time of position regulation is 0.65 s, and its static error is 1.5 cm; the adjusting time of draft regulation is 7.5 s; the fluctuating scope is ±1 cm, when the plowing depth is 20 cm in draft and position regulation. This system could meet the challenge of plowing depth control system in formidable natural conditions, and the object of uniform plowing depth and work stability were achieved.