In evaluating the performance of the ambulance, ride comfort is more critical indicator of the quality of evaluation directly affects the victim's condition and comfort. At present, China's production of ambulances were refitted with a light truck chassis or off-road vehicle chassis. Its leaf spring is not specifically designed for the ambulance, smooth performance generally poor. According to emergency medical personnel reflected wounded in transit, vehicle bumps often makes the patient unbearable, some diseases (such as cardiovascular disease, etc.) often appear en route deterioration. Therefore, to improve ambulance ride, to aid the cause of great significance.

Many factors correlated with the ambulance ride, apparently designed wheelbase, low center of gravity, a special ambulance equipped with independent suspension chassis, enabling vibration and hear the patient load has reduced significantly, from a fundamental improve ambulance ride, but the development of the domestic long chassis this period, it is difficult to implement manufacturers. To this end, in addition stretcher provided damping means decreases from the ground, drive systems, energy transmission pass up, after all, an effective way.

To rely on a stretcher vibration, the country has done some work. In 1975, the Ministry of Health specifically formulated fold vibration standard WS 2-189-75 ambulance stretcher manufacturers in the development work also explored some experience. Due to the lack of theoretical basis, only a general with experience in design, but also from the test situation, and not much damping effect. Furthermore, ISO2631 / 1 seat horizontal vibration used, X direction vibration evaluation criteria are not taken into account by the head of the vibration input. For these conditions, we analyze the body's vibration response and evaluation criteria, the choice of a more ergonomic recumbent X direction vibration standards. Starting from the standard then, through the vehicle's analysis, a mathematical model, derived its stretcher output damping stiffness, damping relationship. Then rigidity damping parameter optimization, and design appropriate damping device so that the stretcher ride comfort is improved. Text to XB425 car as an example calculation.

Evaluation criteria Selection

Currently on the human body vibration evaluation it is widely adopted IS02631 / 1 evaluation. The standard coordinate system is established in that vibration on the human body, and the heart as the origin of coordinates. For supine X direction vibration evaluation, generally follow the IS02631 / 1 in sitting or standing by the X-direction vibration evaluation criteria. In fact, the human organism itself is a multi-joint between the joint when subjected to vibration can play a cushioning effect on skeletal muscle is a viscoelastic material, vibration having a large mechanical damping. This feature determines the human body structure to withstand vibration in the Z direction is greater than the capacity of the X and Y directions. For standing and sitting position of the subject by the support surface vibration input X direction. In this case, the elastic body, the vibration has its own regulation. In this case, the data obtained directly applied supine X direction vibration (vibration input from the head and back) is not appropriate. In addition, the head is very sensitive parts of the skull structure is part of a small damping shell structure, relative to other parts of the body vibration filtering ability is poor. In the standard ISO2631 / 1 explicitly mentioned in the vibration input directly from the head of the case, which may be reduced Ren Xing, noting that in some cases, use of the strict limit is inappropriate. But due to the lack of vibration data supine, it can not be inferred supine X direction evaluate evaluation curve and seat curve X direction in the end there is much difference. Human Vibration Evaluation Criteria of the Federal Association of German Engineers involved in the evaluation VDI2057 supine vibration, which is used by the body lying on his back. Back and head by the vibration input frequency range is 1-80Hz. In the range of approximately 50-70Hz Quarters, with particular attention to the input of the head, and more than 80Hz or more is generally believed that the vibration is absorbed by clothing and upholstered, low-frequency region is 0.1-0.63Hz sickness flu zone, and the standing and sitting phase ratio. supine body's sense of motion sickness are rare. Overall VDI believe the low frequency region (less than 1Hz) study is not sufficient, not yet included in VDI2057. Given the above, we use VDI2057 as a supine body vibration evaluation.

Within the scope of the body's response to 1-80Hz vibration, ISO2631 / 1 gives the feeling of three boundaries, or "exposure limits", "fatigue - reduced efficiency of bounds" and "reduce the boundaries of comfort."