Nonlinear biodynamic analysis of pilot suspension system under three-axis excitation loads

Vibratory energy in direct contact with different members of the body, in a certain frequency range, can be risky. On the other hand, the maneuvers that the pilot conducted during the flight and the sudden accelerations of g entering the plane on the head and neck, the spinal cord and other organs of the body have adverse effects and disrupt the physiological and psychological actions of the pilot. The first, in this research by choosing a suitable model of the human body and then by extracting the motion equations, using the MATLAB software, the displacement, velocity and acceleration equations for each member of the body are obtained. The new work in this research is putting on the model of seat with cushion made of  foam, cushion made of viscoelastic and with cushion made of viscoelastic despite the pilot's seat suspension system that has a non-linear springs and dampers. The results indicate that at high acceleration of g, the pilot's suspension system has the best performance in damping and absorbing the energy of the system. For small movements that at low frequencies in the range of 0 to 30 Hz are occurred, the seat suspension system is not responding and to check this state, we must examine the functions of biodynamics and plotting them in two states of the body in sitting position and body in sitting position on a foam pad. In this case, the results indicate that in the apparent mass diagram, the use of cushion made of foam caused peak shift in this chart from a frequency in the range of 5 Hz to a frequency in the range of 13 Hz. Therefore, the presence of cushion for health is absolutely necessary.