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A Study on Suspension-level Vibro-acoustic Performance Evaluation Method for Road Induced Noise : 노면 가진 소음 개선을 위한 서스펜션 단위의 음향 및 진동 성능 평가법에 대한 연구

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dc.contributor.advisor강연준-
dc.contributor.author송현진-
dc.date.accessioned2018-05-28T16:05:58Z-
dc.date.available2018-05-28T16:05:58Z-
dc.date.issued2018-02-
dc.identifier.other000000149371-
dc.identifier.urihttps://hdl.handle.net/10371/140545-
dc.description학위논문 (박사)-- 서울대학교 대학원 : 공과대학 기계항공공학부, 2018. 2. 강연준.-
dc.description.abstract기존 전달 경로 분석 법을 이용한 로드 노이즈 성능 평가에서는 주행 중 차체 전달 힘을 주파수 응답 함수와 주행 중 가속도 값을 이용하여 계산하게 된다. 또한, 로드 노이즈 성능에 차체와 서스펜션 각각이 미치는 영향을 파악하기 어렵다. 본 논문에서는 직접적으로 서스펜션으로부터 차체로 전달되는 포스를 측정함으로써 구조기인 로드노이즈 성능을 평가할 수 있는 리그를 제작하여 새로운 평가 및 개선 방안 도출 방법을 연구하였다. 마운팅 체결부의 강성평가 및 ODS 분석, 절연 성능 평가 및 무게와 댐핑 영향을 평가하여 리그를 검증하였고, 동강성 법과 역 행렬 법을 이용하여 계산된 포스와의 비교를 통해 차체의 이펙트와 계산으로부터 야기 될 수 있는 오차를 확인하였다. 실 도로 노면 가진을 재현하기 위한 다이노 롤러를 이용한 가진 방법 및 신호 처리 방법이 연구되었고 서스펜션 벤치마킹 분석법을 적립하였다. 또한, 임피던스 모델링 방법과 역 부분 구조 합성법을 이용하여 절연 고무의 개선인자 선정 방법 및 정량적인 동특성 제안 방법론을 적립하였다. 제안된 방법을 실 차량 개발에서의 부시 변경 시나리오에 적용함으로써 연구의 유효성과 신뢰성을 확인하였다.-
dc.description.abstractNumerous previous studies have been conducted on quantifying road noise through transfer path analysis (TPA) using the matrix inversion and the dynamic stiffness methods. However, the matrix inversion method is a calculation that always contains error, even when treated with the best condition number found by trial and error iteration to match the calculation SPL (Sound Pressure Level) to measured SPL. Furthermore, the caveat of the dynamic stiffness method is that it requires accurate dynamic stiffness value up to the frequency range of interest, which, in reality, is rarely available and is challenging to seize. For the sake of cost and time reduction, circumventing these limitations is crucial within the vehicle production period. In this regard, a special suspension rig is devleoped to directly obtain the operational forces at the suspension mounting points neglecting the effect of the vehicle body.
To best utilize this developed rig, a dyno excitation method using precision CNC-milled detachable shell is proposed and its proper operational condition for road noise evaluation is investigated as well. In order to investigate which component plays the biggest role and which component to be prioritized to be tackled, the influence of suspension and body stiffness has on operational force change due to softening the connecting elastomer is studied using the impedance modeling method. Using this method, rig measured dynamic force change which is potentially misleading due to large deviation in dynamic stiffness between the rig and an actual vehicle is also investigated under varying suspension and bushs stiffness combination.		-
dc.description.tableofcontentsCHAPTER 1. INTRODUCTION 1
CHAPTER 2. A METHODOLOGY FOR EVALUATING THE STRUCTURE-BORNE ROAD NOISE PRIOR TO A PROTOTYPE VEHICLE USING DIRECT FORCE MEASURED ON A SUSPENSION RIG 12
2.1. Introduction 12
2.2. Structure-borne road noise transfer path analysis 13
2.2.1 Operational force calculation 14
2.2.1.1 Full matrix inversion method 14
2.2.1.2 Dynamic stiffness method 16
2.2.2 Road noise transfer path diagram 16
2.3. Direct operational force measurement on suspension rig 18
2.3.1 Suspension force rig properties 18
2.3.2 Experimental Setup 19
2.4. Knuckle acceleration spectrum comparison between the baseline vehicle and suspension rig measurements 25
2.5. Operational force comparison acquired by the three methods 28
2.6. Estimation of structure-borne road noise 31
2.7. Benchmarking technique: suspension level dynamic stiffness extraction 34
2.8. Summary 37
CHAPTER 3. A VALIDATION STUDY OF THE DETACHABLE SHELL DYNO EXCITATION METHOD FOR STRUCTURE-BORNE ROAD NOISE EVALUATION 39
3.1. Introduction 39
3.2. Road excitation: structure-borne road noise evaluation 41
3.3. Dyno excitation method: precision CNC-milled detachable replicated road shell 46
3.4. Experimental setup 51
3.4.1 Measurement equipment and sensor locations 51
3.4.2 Operational condition for dyno measurement 54
3.4.3 Operational condition for proving ground measurement 58
3.5. Influence of dyno roller size 59
3.6. Knuckle signal comparison between proving ground excitation and dyno excitation 66
3.6.1 Rough and standard surface 66
3.6.2 Smooth surface 71
3.7. Coherence study 76
3.8. Road noise evaluation examples using proposed dyno excitation: detachable TPA approach and direct force rig approach 80
3.9. Summary 82
CHAPTER 4. ESTIMATION OF BODY INPUT FORCE TRANSMISSION CHANGE DUE TO PARTS MODIFICATION USING THE IMPEDANCE METHOD UNDER ROLLING EXCITATION 84
4.1. Introduction 84
4.2. Transmission force characterization and estimation of changing force due to parts modification using the impedance modeling method 88
4.3. Numerical study: force change (reduction) estimation due to part modification 95
4.3.1 Softening the dynamic stiffness of the connecting bush by 50 % 97
4.3.2 Studying the relation of the suspension rig to vehicle: reducing the stiffness of the body attachment point 102
4.4. Validation for road excitation 105
4.4.1 Experimental setup 105
4.4.1.1 Operational measurement 106
4.4.1.2 Dynamic stiffness measurement for link and body 109
4.4.2 Obtained input values for force change estimation 111
4.5. Validation results 117
4.6. Application scenario: bush change on the lateral arm within an actual vehicle 123
4.7. Summary 129
CHAPTER 5. DERIVATION OF ROAD NOISE IMPROVEMENT FACTOR WITHIN A SUSPENSION SYSTEM USING THE INVERSE SUBSTRUCTURING METHOD 132
5.1. Introduction 132
5.2. Theoretical background 133
5.2.1 Frequency response function based sub-structuring modeling 133
5.2.1.1 Modeling of single degree of freedom single path system 133
5.2.1.2 Modeling of a multi-path system 136
5.2.2 Input force estimation 138
5.2.3 Inverse sub-structuring method 140
5.3 Cross member mount points modeling 142
5.4. Experimental validation 149
5.4.1 Test setup 149
5.4.2 Bushing property extraction 153
5.5. Validation results 157
5.6. Summary 160
CHAPTER 6. CONCLUSIONS 161
REFERENCES 166
APPENDIX 172
국 문 초 록 178		-
dc.formatapplication/pdf-
dc.format.extent6220556 bytes-
dc.format.mediumapplication/pdf-
dc.language.isoen-
dc.publisher서울대학교 대학원-
dc.subjectSturcture-borne road noise-
dc.subjectSuspension rig-
dc.subjectDirect operational force transfer path analysis-
dc.subjectMechanical impedance method-
dc.subjectDyno excitation method-
dc.subjectFRF-based sub-structuring-
dc.subjectand Inverse formulation method-
dc.subject.ddc621-
dc.titleA Study on Suspension-level Vibro-acoustic Performance Evaluation Method for Road Induced Noise-
dc.title.alternative노면 가진 소음 개선을 위한 서스펜션 단위의 음향 및 진동 성능 평가법에 대한 연구-
dc.typeThesis-
dc.contributor.AlternativeAuthorDavid P. Song-
dc.description.degreeDoctor-
dc.contributor.affiliation공과대학 기계항공공학부-
dc.date.awarded2018-02-
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