Steering Stability Analysis Of Six Wheel-legged Chassis For Forest

With the increasing annual output value of domestic forestry,the mechanization and automation of forestry has become an inevitable trend of China's forestry development.The traditional forest operation chassis is driven on rough woodland pavement,due to its lack of self-adaptive control function,it has a high probability of tipping when tipping over obstacles and turning,and poor stability.The six-wheel legged chassis for forest is used to control the height change of the center of gravity of the chassis when the steering operation has low stability and the steering is not stable,by adjusting the amount of expansion and contraction of the hydraulic cylinder,and to change the posture of the chassis to improve the overall stability of the chassis.The main research work and conclusions are listed as the following:1.The corresponding six-wheel legged chassis for forest virtual prototype model is improved.The electric push rod is replaced by a hydraulic cylinder.The turning angle of the wheel-leg and the folded-back steering angle are determined by the interference relationship between the frame and the wheel-leg and the interference relationship between the front and rear frames.The maximum speed of the six wheel-legged chassis is 30 km / h in this paper.2.Base coordinate system of the chassis is established at the midpoint of the front frame,and establish the kinematic model of the chassis through the spin theory.The position of the ground contact point of the chassis tire is obtained,mathematical models and kinematics models of the relationship between wheel-leg changes and swing wheel-leg angles,as well as frame positions are established by the Jacobian matrix.3.By analyzing the working conditions of the six wheel-legged chassis for forest when turning on the inclined plane,the chassis tilting axis is determined.The coordinates of the center of gravity and the mathematical model of the tilting axis are obtained.The mathematical model of chassis stability is obtained through the theory of secondary stability,combined with the chassis kinematics model and the judgment method of second-level stability.Through Adams simulation,the effects of forward speed,articulated steering angle,and steering speed on chassis stability are discussed separately in this paper.4.The stability changes during the complete steering of the chassis are discussed under no-load and full-load conditions.In this paper,the critical state and overturning state are stabilized and leveled.Based on co-simulation of Adams and Simulink,the three control methods of PID control,fuzzy control,and fuzzy PID control are used to level the stability of the chassis.Through simulation,comparing the output data,it can be obtained that after adopting different control strategies,the stability of the chassis has been improved to different degrees.Under the fuzzy PID control,when the articulated steering angle is 25 °,the minimum chassis stability is about 0.628,which is an overall increase of 20.92% compared to the case without control.When the articulated steering angle is 30 °,the minimum chassis stability is about 0.72,which is an increase of 24.5% compared with the case without control.