Transient characteristics of a wheeled machine with a vibration-protective seat

BACKGROUND: Shock and vibration loads caused by the microrelief of the supporting surface negatively affect both the health of operators of ground transportation and technological machines and the quality of work performed due to the deterioration of reactions and attentiveness. Vibration-protective seat systems are an effective means of mitigating dynamic effects on operators. Development of vibration-protective systems of operators' seats is an urgent task.

AIMS: Develop a mathematical model of a machine with a vibration-protective seat system, taking into account a given force response and damping coefficients, which will make it possible to study the response of the system to a typical impact when the chassis wheels collide with the step. The model should determine the transient characteristics of a wheeled vehicle with a vibration-protective seat, have a high speed of calculation of the dynamic process, which will optimize more parameters at the same time.

MATERIALS AND METHODS: To develop the model used, we consider a flat design scheme of collision of two wheels of the front axle simultaneously on a step of a given height.  The car hits the step with the front axle only, the step height is small relative to the wheelbase.  The vertical oscillations of the center of mass were approximated by a linearized mass oscillation model with one translational degree of freedom.  The differential equation of motion of the chassis mass is used to model the vertical coordinate of motion of the seat base.  The assumptions of rigid fixation of the operator's cabin on the chassis and smallness of the mass of the seat with the operator relative to the chassis mass are adopted.  The calculation scheme for modeling vertical oscillations of the mass of the seat with the operator relative to the chassis is similar to the scheme of oscillations for the chassis relative to the ground.  Two schemes are used simultaneously in one simulation model. Modeling of vertical oscillations of the chassis and the seat with the operator when the chassis wheels collide with the step is carried out using a simulation mathematical model in the Russian simulation environment SimInTech.

RESULTS: As an example of the use of the developed simulation model, the results of modeling of a separate transient process of collision with the wheels of the front axle of the machine on a step with a height of 0.1 m at a speed of 1 m/s are given.  The results are presented in the form of time dependencies of vertical coordinates of the support surface, base chassis, deformation of the vibration protection mechanism of the seat and corresponding time dependencies of absolute velocity and acceleration of the seat with the operator. The maximum value of the absolute acceleration of the seat with the operator was determined.

CONCLUSIONS: The simulation model of the stage collision developed using the Russian software SimInTech takes into account elastic and viscous properties of tires, interaction geometry and nonlinearity of the force response of the vibration protection system. The model allows rapid simulation of the transient process, which opens up the possibility of analyzing multiple variants and optimizing parameters.