Use of the Belleville spring package in the vibration protection mechanism of the operator's seat

Reducing the vibration effects on the operator of a construction, road and other machines is a relevant objective, since its accomplishing improves the efficiency and accuracy of the work performed by machines and reduces the risk of operators' occupational diseases. Vibration protection systems with the effect of quasi-zero stiffness are promising. To produce this effect, Belleville springs packages can be used. They are a way to create a simple, reliable and inexpensive passive mechanism of the vibration protection system of the operator's seat. The influence of the static characteristic center slope of two Belleville springs packages on the maximum acceleration of the load under the sinusoidal kinematic excitation of the seat base movements is investigated. The static characteristic center slope of the spring packages was characterized by the coefficient that affects the type of the static characteristic according to the known analytical expressions for the separate spring force. To obtain the chair acceleration values in a fixed coordinate system, we used a simulation mathematical model developed in the Simscape Multibody package for modeling mechanical systems of the MATLAB mathematical system. The model used blocks of a fixed coordinate system, a sliding joint and a rigid body forming a chain. The maximum acceleration of the chair in a fixed coordinate system was defined during a predetermined period of time at the end of the transition process under the steady state oscillations. When conducting the computational experiment, the specified oscillations amplitude of the chair base and the angular frequency of these oscillations varied. For a proper comparison of the experimental results in the form of graphical dependencies of the maximum acceleration on the amplitude and frequency, the ranges of acceptable and unacceptable arguments combinations were selected for the two spring packages. The combinations of amplitude and frequency were considered unacceptable when the maximum deformation of the spring package went beyond the static characteristic maximum. For the two packages of springs, the acceptable regions were different, therefore their intersection used for the comparative analysis, was obtained. The springs package with a relatively high stiffness in the center of the static characteristic is found out to generally provide better vibration protection of the chair in the entire acceptable range of arguments. Simultaneously, a package with lower stiffness in the center of the characteristic dampens vibrations better in the small amplitudes area, i.e. when operating in the quasi-zero stiffness area.