## 1 Introduction
### _Suspension Types of Vehicle Driver Seats_  
One of the fundamental methods of mitigating the adverse effects of vibrations on machine and vehicle operators is the construction of seat suspensions with vibration-isolating properties [3, 4]. These solutions can be classified as either passive or active vibration isolation. Passive vibration isolation utilises elements with linear elasticity (\(k\)) and non-linear damping (\(c\)), with constant characteristics (Figure 1).  
In this type of suspension, the damping and stiffness coefficients are selected to align with the prevailing working conditions. In numerous designs, the operator is permitted to alter the damping coefficient (c) and stiffness according to their assessment of their weight and working conditions (Figure 1a). Effective damping can be achieved automatically or manually by setting a constant pressure (pneumatic spring) or tension in the magneto damper. Semi-active systems, which permit the damping and stiffness values to be varied over time, represent an extension of this method (Figure 1b).  
The values of the damping coefficient \(c(t)\) and the stiffness \(k(t)\) vary continuously, allowing for measurement while the machine is exposed to vibrations caused by the condition of the road surface or by the vibrations themselves caused by its equipment. The active suspension system (Figure 1c) is equipped with an actuator that generates the force necessary to eliminate vibrations. A well-designed automatic control system for such a suspension continuously adapts to the current operating conditions of the working machine, as evidenced by the following references [5; 6; 7].  
The semi-active suspension systems of driver seats in vehicles involve different technologies that enable the adjustment of comfort and stability. Types of semi-active suspensions include:  
* Semi-active damping allows the adjustment of damping to driving conditions, thus acting faster than traditional passive systems while enhancing vehicle comfort and handling;
* An adaptive damping system that adjusts itself to changing road conditions for improved comfort and control--it can also respond to irregularities on the road surface;
* Semi-active load-levelling, which maintains stability and vehicle height adjustment, especially while carrying heavy loads;
* Semi-active suspension control that offers control over damping--improving ride comfort and road friendliness.  
The aforementioned systems encompass electromagnetic, hydraulic and pneumatic systems [8]. In electromagnetic systems, the damping and stiffness of the suspension are controlled by electrical current, whereas in hydraulic systems, the suspension is regulated by pressurised fluids [9]. In contrast, pneumatic systems provide compressed air support, thereby enabling the necessary springiness and damping. Each system has its own set  
Figure 1: Types of seat suspensions for work machines: (**a**) passive (adjustable) suspension, (**b**) semi-active suspension, (**c**) active suspension.  
of advantages and disadvantages, and therefore factors such as cost, performance and reliability must be considered when deciding which system to use.