Study of the turn kinematics of a wheeled vehicle with a variable track

BACKGROUND: The trapezoidal lever mechanism used in the steering linkage for turning steerable wheels to change the motion direction of a wheeled vehicle does not fully meet the conditions for ensuring pure wheels rolling and corresponding to the correct turn kinematics, which is especially evident when adjusting the track. AIM: Assessment of the degree of discrepancy between the actual turn kinematics and the correct turn kinematics when changing the track of the tractor. METHODS: Analytical methods were used in the study, which made it possible to obtain some computational dependencies, to perform a numerical analysis of the curvilinear motion of a tractor with a variable track for different parameters of the steering linkage, and on this basis to establish patterns between the geometric characteristics of the steering linkage and the kinematic parameters. RESULTS: Reasonable geometric characteristics of the steering linkage, which ensure the turn kinematic parameters closest to the required ones, are set for the most commonly used value of the width of the kingpin track. For the Belarus-80.1 tractor, it corresponds to 1.02 m. At the same time, for example, at a steer angle of the inner steerable wheel of 25°, the minimum turning radius ensured by the steering linkage differs by 0.6521 m (10.44%) and at the steer angle of 40° by 0.2829 m (9.27%) from their values obtained from the pure rolling condition. When changing the track width of the machine, there is a violation of the initial geometric characteristics of the linkage and the corresponding mismatch of the turn kinematic parameters ensured with the steering linkage and the correct turn kinematics increases. A comparison of the minimum turning radii at an angle of 25° and a kingpin track of 1.42 m showed an increase by 3.2340 m (35.83%), and at 40° — by 0.8956 m (20.21%). CONCLUSION: To ensure the correct turn, it is necessary to conduct a thorough theoretical analysis of the steering linkage and to improve its design on this basis.