Contents

List of Figures ………………………………………………………………………………………………………………… 4
Notation and symbols ……………………………………………………………………………………………………… 8
1. Introduction …………………………………………………………………………………………………………… 11
2. Seat with adjustable pressure profile ………………………………………………………………………… 13
2.1. Mechanical subsystem………………………………………………………………………………………. 14
2.2. Electro-pneumatic control subsystem …………………………………………………………………. 14
3. Mathematical model……………………………………………………………………………………………….. 18
3.1. Mathematical model of the original system …………………………………………………………. 18
3.1.1. Model of the electro-pneumatic control subsystem ………………………………………… 18
3.1.1.1. Mathematical model of the valves …………………………………………………………. 18
3.1.1.2. Mathematical model of the compressed air supply ………………………………….. 22
3.1.2. Model of the mechanical subsystem …………………………………………………………….. 24
3.1.2.1. Model of polyurethane foam ………………………………………………………………… 26
3.1.2.2. Model of the latex air spring…………………………………………………………………. 26
3.1.3. Numerical calculation ………………………………………………………………………………… 32
3.1.3.1. Calculation of the response of the original system …………………………………… 34
3.1.3.2. Calculation of transmission of acceleration …………………………………………….. 37
3.1.4. Summary ………………………………………………………………………………………………….. 41
3.2. Mathematical model of the improved system ………………………………………………………. 41
3.2.1. Introduction of the improved system ……………………………………………………………. 41
3.2.2. Mathematical model of the vacuum pump…………………………………………………….. 43
3.2.3. Mathematical model of the combination of the latex air spring and the additional
latex tube ………………………………………………………………………………………………………………. 45
3.3. The comparison between the original system and the improved system ………………….. 49
3.3.1. The comparison of calculated results ……………………………………………………………. 50
3.3.1.1. Under the static conditions …………………………………………………………………… 50
3.3.1.2. Under dynamic conditions ……………………………………………………………………. 50
3.3.2. The comparison of the experimental results ………………………………………………….. 52
3.3.2.1. Under static conditions ………………………………………………………………………… 52
3.3.2.2. Under dynamic conditions ……………………………………………………………………. 59
3.4. Conclusion ………………………………………………………………………………………………………. 64
4. Finite element analysis using MSC. Marc software ……………………………………………………. 65
4.1. Finite element model of latex tube ……………………………………………………………………… 65
4.1.1. Bulge test of latex membrane …………………………………………………………………….. 65
4.1.2. Constitutive model …………………………………………………………………………………….. 71
4.1.3. Simulation results………………………………………………………………………………………. 71
4.2. Finite element model of tape ……………………………………………………………………………… 72
4.2.1. Uniaxial tensile test of the tape ……………………………………………………………………. 72
4.2.2. Constitutive model …………………………………………………………………………………….. 75
4.2.3. Simulation result ……………………………………………………………………………………….. 75
4.3. Finite element model of foam ……………………………………………………………………………. 76
4.3.1. Uniaxial compression test of foam ………………………………………………………………. 76
4.3.2. Constitutive model …………………………………………………………………………………….. 77
4.3.3. Viscoelastic properties ……………………………………………………………………………….. 78
4.3.4. Comparison of experimental result and simulation result ……………………………….. 80
4.4. Finite element analysis of the models of compression test …………………………………….. 82
4.4.1. Models of compression test ………………………………………………………………………… 82
4.4.2. Contact friction problem …………………………………………………………………………….. 83
4.4.3. Simulation results and experimental results ………………………………………………….. 84
4.5. Finite element analysis of a seat cushion with a simplified human body …………………. 86
4.5.1. The complete model …………………………………………………………………………………… 87
4.5.1.1. Simulation results and experimental result ……………………………………………… 91
4.6. Conclusion ………………………………………………………………………………………………………. 95
5. Summary ………………………………………………………………………………………………………………. 96
6. References. ……………………………………………………………………………………………………………. 98
7. List of papers published by the author. ……………………………………………………………………. 101
Appendix A: Model of Polyurethane Foam for Uniaxial Dynamical Compression ………………. 102