Study On Automatic Reversing System Of Tractor-Trailer Combination Along Rectilinear Path

In this paper, the backing problem of tractors with twin-axis trailer which are widely used in production and transportation was studied. A control system was designed and realized this type of vehicle automatic backing motion along rectilinear path. This research for agricultural vehicle achieving automated and unmanned provide technical support. The main contents are as follows:(1) Part of the thesis analyzed and studied the detection system of agricultural vehicles'state parameters. State variable has been calibrated and detected using digital compass and Gyroscope and displacement sensor respectively. The experiment results indicate that, detection method developed can satisfy the requirement of speed data sampling,sensors was proven to be capable the accuracy demand of agricultural vehicles state parameters.(2) Tracking control system of tractors with twin-axis trailer was introduced in detail. The system can be divided into two parts: angle feedback control strategy and tractor steering control system.(3) A two-wheel model is built, and a nonlinear kinematics equation of the system is established according to its kinematics relations. The paper linearized the nonlinear system in equilibrium state. A multi-input multi-output angle tracking feedback controller was designed depending on the linearization of the weak linear system. According to the system stability analysis by Lyapunov first method, the system was found to be an unstable system under any conditions. The result of simulation showed that the system could be controlled while the input variables meet the condition of constraint.(4) This study built system of real vehicle test hardware platform, designed the system control software, separately carried on the tractor steering control test and linear backing test, and achieved satisfactory results.The result of the real vehicle test show that the controller may make the tracking angle converged within the range of±6°when the input variables meet the condition of constraint. The maximum absolute value of output control is 9.01°. The maximum absolute value of tractor yawθis 5.47°with a standard deviation (SD) of 1.85°. The maximum absolute value of the included angleβbetween trailer rear-axle frame and the tractor is 5.46°with SD of 2.75°. The maximum absolute value of the included angle ? between trailer rear-axle frame and front-axle frame is 5.41°with SD of 1.86°. Thus it may be seen that the maximum SD of the tracking angle is 2.75°, indicating the designed controller may track and controlθ,βand ?, and the changes of the control output ?αof front-wheel steering angle.