Study And Application On The Vertical Vibration Model Of Seated Human Bodies

Vehicle ride comfort has become an important index to evaluate the performance of an automobile. However, the human body model is ignored or only considered to be a rigid mass in the vehicle pre-development, which resulted in that the design of automotive damping elements are not reasonable, and the occupants do not reach the most comfortable ride feel. In the automotive ride tests, when the real person is used as automobile seat load, the difference of test results is very large due to differences in subjects’ s age, size, occupation and so on. For a same subject, the repeated error is also large because of the different postures and physical state. When the sand bag or water human is used as automobile seat load, automotive ride evaluation index can not be measured objectively because the load can not simulate vibration characteristics of the human body.Foreign scholars have done a lot of research about European and American vertical vibration characteristics of seated human body. ISO5982-2001 standard has also been established and there is a perfect vertical vibration model of seated human body. However, one of the characteristics of apparent mass(AM), driving point mechanical impedance(DPM) and seat to head transfer function(STH) is studied alone by Chinese scholars, which can not fully reflect the vertical vibration characteristics of Chinese seated human body. At the same time, physical models of seated human body are studied by a few domestic and foreign scholars in the early years, and now it is not applied to the automotive ride test widely. Therefore, the comprehensive vertical vibration characteristics of Chinese seated human body should be researched and can be applied to automotive ride pre-design, which can help to match damping elements. The physical model of the Chinese seated human body should be also developed as seat load in the automotive ride tests, and automotive ride evaluation index can be measured accurately and objectively.In view of the above analysis, the following research work has been carried out in this paper.Firstly, the vertical vibration characteristics of seated human body under the standard test conditions are studied. With the vibration test bench, the vibration characteristics of 30 volunteers are tested under the standard test conditions and the three indicators of seated human body are obtained: AM, DPM and STH. By comparison, the vertical vibration characteristics of Chinese seated human body in this test are very different from the ISO5982-2001 standard.Secondly, the vertical vibration characteristics of seated human body under the different conditions are studied. The human body vibration tests under different test conditions are carried out, and the characteristic data of the vertical vibration of the seated human body are obtained. Under the test conditions of larger vibration intensity, hand on the armrest and ottoman height from low to high, research results show that the vertical vibration characteristics of the seated human body change regularly compared to the standard test conditions. There are some linear relationships between the vertical vibration characteristics of the seated human body and weight, height, body mass index.Furthermore, the vertical vibration model and its physical model of seated human body are studied. Based on the vertical vibration characteristics of seated human body, the two degree of freedom, three degrees of freedom and a new type of four degree of freedom seated human body model are established, and they all can express the characteristics of the AM and DPM of the Chinese seated human body approximately. The four degrees of freedom model can also simulate the characteristics of STH, and it can more fully express the vibration characteristics of the seated human body. According to parameters of the two degree of freedom human body model, the physical model of seated human body is developed. The physical model can approximately simulate the characteristics of the AM and DPM of the Chinese seated human body and it can be used as seat load of automotive ride comfort tests.At last, the model and its physical model of seated human body are applied to the development of vehicle ride comfort. The dynamic model of human-vehicle-road system is established, and the simulation results show that the weighted acceleration r.m.s. value on the cushion of chinese two degrees of freedom seated human body model is about 17% less than that of sandbag model and about 9% more than that of ISO5982-2001 seated human body model. Hardware in the loop tests are carried out separately using the physical model of the Chinese seated human body and sandbags, and the test results show that the weighted acceleration r.m.s. value on the cushion of the physical model of the Chinese seated human body is about 10% less than that of sandbag; Different seated human body models are applied to optimize vehicle shock absorber damping, and the results show that the optimized shock absorber damping with the two degree of freedom Chinese seated human body model is about 27% more than that with sandbag and about 7% less than that with ISO5982-2001 seated human body model. The Chinese seated human body model and its physical model can simulate the vertical vibration characteristics of the Chinese seated human body, and can be better applied to the design and development of Chinese vehicles.