针对轮式联合收获机自动导航中需要对电控液压转向特性进行测试与分析等问题，设计了转向轮转角测量装置，构建了电控液压转向测试系统，通过电液转向控制器实现了转向轮转角的实时控制与同步测量，对电控液压转向过程中的稳态转向速率、瞬态响应过程等线性与非线性特征开展了分析与测试。由路面静态试验验证得到收获机转向轮转向中位左右15°范围内，转向轮转角对应转向液压缸活塞杆伸缩量关系线性拟合决定系数R2＞0.99，均方根误差RMSE=0.25。田间动态试验显示：电控液压转向存在的非对称死区电压区间占控制电压范围的32%；转向轮稳态动作时的转向轮转向速率与转向控制电压线性度显著；在不同方波信号激励下，转向轮瞬态响应过程平均滞后时间90 ms、调整时间150~200 ms、调整转角0.21°~2.77°、滞留时间25~77 ms、滞留转角0.10°~1.24°。
The automatic navigation of the combine harvester can reduce intensity of drivers and improve the quality and efficiency of harvester operation. Converting the traditional hydraulic steering system of existing combine harvester into electronic control hydraulic steering system is the prerequisite to realize the automatic navigation of combine harvester. However,after the refit of electronic control hydraulic circuit. It has the characteristic of complex structure of steering system,time delay of electronic control dynamic response and nonlinearity of control system,which is not conducive to the accurate design of followup navigation controller. In order to realize automatic navigation control and steering characteristic test of the wheeled combine harvester,an electrically controlled hydraulic steering test system has been set up in this thesis. The abovementioned system is mainly composed of electrically controlled hydraulic steering valve set,industrial control computer,control box and steering angle measuring equipment. To further obtain the steering characteristic test of the wheeled combine harvester,the static test on the concrete and curve fitting are carried out for the relation between the expansion of hydraulic cylinder and the angle of steering wheel which determined the steering control voltage range of electrically controlled hydraulic steering.The different control voltages correspond to the steering velocity of wheel and the dynamic response process of square wave control signal. The relationship between input signal amplitude and retardation time,steadystate response time,residence time is analyzed. After the combined harvesting electromechanical control hydraulic steering characteristic test,the modified combine harvester realized fast and stable electrohydraulic steering control. The electrohydraulic steering control system has an asymmetric control voltage dead zone. When the proportional valve opening amount is equal,that is,the control voltage is the same,the steering wheel has different steering speeds,and the oneway rotation speed is approximately linear with the valve opening increment. The transient response process of the electronically controlled hydraulic steering consists of a delay link,an integral link and a secondorder oscillating link. It is mainly affected by the internal friction damping of the valve core,the spool return spring and the response delay of the electrical signal,and its transient response characteristics and power. The control hydraulic steering speed relationship basically conforms to the characteristics of the electrohydraulic proportional valvecontrolled asymmetric hydraulic cylinder system. Static test on the concrete revealed：the steering angle of the steering wheel is approximately linear with the expansion of hydraulic cylinder,the regression determination coefficient is greater than 0.99 and the root mean square error is 0.25. The steering angle of the steering wheel is from -29.76 ° to 30.23°. Dynamic test in the field revealed:the dead zone voltage range accounts for 32% of the control voltage range;When the steering wheel is in steady motion,the steering rate of steering wheel is approximately linear with steering control voltage; the system has a transient state response process,and the average retardation time is 90 ms,steadystate response time is from 150 ms to 200 ms,steadystate response angle is from 0.21° to 2.77°,the residence time is from 25 ms to 77 ms,the stagnant angle is from 0.10 ° to 1.24 °. The design of the subsequent navigation controller is usually carried out by establishing the transfer function or dynamic model of the steering system. However,due to the combined operation of the combine harvester in the field,the hydraulic cylinder load force is affected by the total weight of the harvester and the relationship between the tire and the soil. The influence of spring stiffness variation and different viscous damping forces,the establishment of complex and unique system models often can not meet the actual needs,so the approximate linearization of the combined harvesting electromechanical hydraulic steering system and the test of the transient response time distribution in each period can provides practical parameter support and adaptability research basis for the design of the combine harvester navigation controller.