Five-suspensions Vibration Theory Of Seat-cab Coupled System For Trucks

The seat-cab coupled system is one of the most important parts of trucks.Its suspension system determines ride comfort.However,the vibration mechanism is not yet fully clear and its suspension system lacks reliable forward matching theory.They restrict the comfort improvement and lead to a series of prominent problems,such as drving fatigue,public safety,and so on.To solve the above problems,a "Five-suspensions" idea is proposed.The vibration mechanism and the suspension matching theory of the coupled system are analyzed and validated by test.The main innovation results are as follows:1?According to the viewpoint of system engineering,the driver,seat,and cab are regarded as a complete system.Instead of the traditional space perspective of up and down,the seat suspension is deemed as the fifth suspension of the cab,thus,the new idea of "Five-suspensions" is put forward.The multidimensional coupling characteristics of the system are revealed from the kinematic point of view.The nonlinear dynamic model and the equations of the seat-cab coupled system are created for the first time,which can reflect the dynamic interaction of its various parts.In the model,the nonlinear factors of the shock absorber,the spring,the stable rod,the rubber bushings,and the guiding mechanism are considered,and the corresponding subsystem model is established.A shear type low frequency vibration isolation seat system is proposed,the analytical expression of the nonlinear elastic force for the seat suspension is established based on the virtual work principle,and the seat system dynamic equation is created.2?Based on the established dynamic model and the equations,through the vibration characteristics analysis,the coupling mechanism between the driver's seat and the cab is ascertained,the influence laws of the Five-suspensions parameters on the vibration characteristics and ride comfort are revealed,which provides a theoretical basis and technical support for suspension parameters matching.Through the analysis of the natural frequency and the vibration mode,the results show that the specific direction stiffness parameters of the cab slewing bushing,the swinging arm bushing and the lock cylinder bushing have great influences on the system natural frequency.Through the study of the system decoupling rate,the results show that the coupling between the cab yaw mode and other modes is weak and the severe coupling exists among other modes;compared with the condition of the conventional seat suspension,the vertical mode decoupling rate under the condition of the low frequency seat is reduced by 4.08%and the pitch mode decoupling rate is reduced by 3.12%.Through the vibration transfer characteristics analysis of the system,the results illustrate that the larger damping of the seat damper can reduce the resonance peak of the acceleration isolation rate for the low frequency vibration isolation seat,but cause a significant increase in the non resonance area with the excitation frequency larger than 0.5 Hz.Moreover,the medium damping of the cab suspension dampers is beneficial to improve the vibration transmission characteristics.Through the effect analysis of the Five-suspensions parameters on the weighted RMS acceleration,the results show that:?the proper reduction of the Five-suspensions spring stiffness can improve ride comfort;?it is beneficial to increase the y-direction stiffness and to reduce the ry-direction stiffness of the swinging bushing and the overturn bushing;?too large torsion stiffness of the stable rod is not conducive to the comfort improvement;?under the random conditions,the damper damping coefficient of the nonlinear section has little influence on the comfort,while the linear damping coefficient has great effect on the comfort and the best value exists.3?A forward matching method of the Five-suspensions parameters for the seat-cab coupled system is created,which solves a series of key problems that perplex the matching and design of the suspension system.Focusing on the issue that the mode requirement is hard to satisfy by the stiffness parameters design of the seat suspension,the cab suspension spring,the rubber bushings of guide mechanism,and the stabilizer bar,using existing methods,a stiffness parameters matching method of the Five-suspensions based on the optimal approximation of inverse nonholonomic spectrum under the local mode constraint is proposed.Through the parameters influence analysis of the negative stiffness isolation mechanism and the main and auxiliary springs in the low frequency vibration isolation seat,a parameters matching method of the seat mechanism and the springs is established.In view of the problem that the matching range and the optimal damping parameters of the seat suspension and the cab suspension dampers are difficult to be determined,an analytical method for determining the feasible design area of the cab suspension system damping ratio is proposed,and a cooperative matching method of the Five-suspensions nonlinear damping parameters is established.Aimming at the problem that the traditional equal thickness throttle slices are hard to meet both the slice opening and the slice stress strength,the deformation formula and the stress formula at arbitrary radius position of the unequal thickness throttle slices are deduced,respectively.Based on the theory,a parameters matching method of the valve system for suspension hydraulic shock absorbers is created.4?According to the parameters matching method of the Five-suspensions for the seat-cab coupled system,a prototype is designed.The shock absorber test,the seat bench test,and the running test of the truck ride comfort are carried out,respectively.Through the comparison of the test and the simulation,it can be seen that the dynamic model can effectively reappear the real dynamic responses under the random condition and impact conditions,respectively.Moreover,the accuracy of the proposed model is higher than that of the comparison models.The results show the correctness of the created nonlinear dynamic model and the equations of the seat-cab coupled system.The designed suspension system effectively attenuates the truck vibration caused by the road excitation and impact,and meets the national standard requirements.They indicates the effectiveness and the reliability of the parameters matching method of the Five-suspensions for the seat-cab coupled system.