Stability Analysis And Anti-rollover Research For A Six Wheel-legged Forestry Machinery Chassis

With the domestic forestry output value increased year by year, mechanized automated and intelligent afforestation is the development trend in the future. The wheel-axle type and track type traditional forestry chassis without adaptive control function are more easily rolled over on the bumpy road. In this paper, an improved six wheel-legged forestry machinery chassis is advanced, and the chassis can optimize the pose and position according to the road surface features through changing the angle of the pendulum arm to improve the stability. The main research work and conclusions are listed as the following:1. Virtual and experimental prototype models of the six wheel-legged forestry machinery chassis are designed and developed. The prototype consists of 14 moving parts:front frame, rear frame, left up arm, right up arm, left Y shaped arm, right Y shaped arm, left back arm, right back arm and 6 wheels. Based on the prototype model, parameters such as size, mass and range of the pendulum arm angle are determined. Base coordinate system is established at the midpoint between the arm joints in the front frame, and the kinematic model of the chassis is established by the screw theory.2. Based on Kane equation, the rollover dynamic model is established with the Fiala wheel model.12 generalized coordinates are designed for the general dynamic model. Considering the relationship between the rollover angular speed and the generalized velocity and angular velocity in the pure rollover condition, general dynamic model of the chassis is simplified. The rollover dynamic model is established.3. Based on the mechanism of the static instability, kinematic model and stability pyramid method, static stability influences of the pendulum angle are researched in the paper. The conclusion is that lowering the center of gravity when the chassis is with vertical instability and leveling the frame when the chassis is with side instability can improve the stability of the chassis. A static stability control strategy is developed according to the analysis.4. Based on the mechanism of the dynamic instability, dynamic model and TTR warning algorithm, dynamic stability influences of the chassis speed and pendulum angular acceleration are achieved in the paper. The conclusion is that increasing angular acceleration of the rollover axle pendulum arm during the rollover process can reduce the rollover angular speed of the chassis. Based on the analysis, a dynamic stability control strategy is achieved and an intelligent obstacle-surmounting method is developed to keep the frame stable.5. Based on co-simulation of ADAMS and Simulink, three conditions include vertical slope, side slope straight driving and dynamic obstacle crashing of the chassis are simulated. Through the comparison, the stabilities of the chassis are improved with different levels by the stability control strategy. Tests of intelligent obstacle surmounting method is conductor, and the experimental result shows that the roll angle and trim angle are heavily decreased by the intelligent obstacle surmounting system from 4.5° and 2.5° to 0.75° and 0.4° compared with the passive method.