Design And Analysis Of The Novel Forestry Chassis With 3 Degrees Of Freedom And Installed Luffing Wheel-legs

Most of the forest areas in China are mountainous and hilly terrain.It is difficult for conventional vehicles to adapt to complex road conditions.Therefore,it’s important to develop a chassis that is well-adapted to the complex terrain conditions in the forest.According to the principle of adapting to terrain with multi-degrees of freedom,a novel forestry chassis with an articulated body with three degrees of freedom and installed luffing wheel-legs(FC-3DOF&LW)is proposed.FC-3DOF&LW adapts to terrain well and provided contact between wheels and ground at all times,which contributes to successful driving in rough terrain.FC-3DOF&LW has good ability to climb slopes,traverse obstacles compared with conventional six-wheeled chassis.In addition,the structure of luffing wheel-legs can make the chassis with an articulated body with three degrees of freedom adapt to terrain passively and adjust position actively,which contributes to driving in forestry rough terrain.The research content and results of this paper are as follows:1.A novel forestry chassis with an articulated body with three degrees of freedom and installed luffing wheel-legs(FC-3DOF&LW)is proposed.The chassis with an articulated body with three degrees of freedom adapts to terrain well,which contributes to successful driving in rough terrain.In addition,the luffing wheel-legs can adjust position actively,which enhance the capacity of traversing smoothly for chassis.As a result,FC-3DOF&LW is able to drive in forestry rough terrain.2.The wheel size of luffing wheel-leg is optimized.A multi-variable non-linear equation is established involves the driving force Ft,the depth of the wheel into the road Z and the diameter D.The Matlab Optimization Toolbox is used for multi-objective nonlinear constrained optimization.The optimization goal is to take maximum Ft and minimum Z.As a result,the wheel diameter D of luffing wheel-leg is 460mm,and the wheel width B is 210mm,which also provides a guide for the wheel size of front frame.3.The ANSYS simulations of the improved front and rear frame are carried out,which analyze the static performance of the frame included two typical conditions of full-load bending and full-load torsion.The results show that the structures of frames can reach the requirements to load the chassis body.4.The position relationships between dropping and lifting hydraulic cylinder and wheel-legs are constructed in coordinate system.The Jacobian matrix that involves the velocity between dropping and lifting hydraulic cylinder and wheel-legs is acquired.Kinematics of the luffing wheel-leg is established,which contribute to control the velocity of dropping and lifting hydraulic cylinder when FC-3DOF&LW surmounts obstacles.In addition,Dynamics of the luffing wheel-leg is based on the Euler-Lagrange method,and the relationship between the force of hydraulic and the angular velocity and the angular acceleration of luffing wheel-legs are constructed.5.Three simplified terrain conditions for surmounting are constructed,and the strategy of climbing slopes and surmounting obstacles for FC-3DOF&LW is proposed.To verify the analysis exactly,simulations that surmount simplified terrain are established in ADAMS.Simulation results validate the effectiveness of the proposed the strategy.In addition,a method based on multi-body dynamics simulation experiment is proposed,which contributes to predicting the height of obstacle for surmounting.The research results of this paper provide basic development for the mechanization,automation and intelligentization of forestry equipment,and enhance the theoretical and technical foundation for special chassis applied in forest.