vertical dynamics - ## 전산설계자동화 실험실 ## 방문해 주셔서...
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![Page 1: Vertical Dynamics - ## 전산설계자동화 실험실 ## 방문해 주셔서 ...dal.cnu.ac.kr/dal/lecture/vehicle_dynamics/2015/vehicle... · · 2015-11-263 Vehicle Ride Performance](https://reader033.vdocuments.net/reader033/viewer/2022051803/5b06a7217f8b9ad5548d2a8c/html5/thumbnails/1.jpg)
김성수
Vertical Dynamics
Vehicle Dynamics (Lecture 5)
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2
Vertical Vehicle Performance
Vertical Dynamics and its applications
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3
Vehicle Ride Performance Model
Vertical Dynamics and ride evaluation
승차감을 객관적 지수로 평가할 수 있는 방법 활용을 위한 수직 동역학 모델
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Vertical Vehicle Dynamics
Ride evaluation• ISO 2631 (인체 진동 노출 평가 기준, 1974년 제정)• 노출한계 범위: 안전이나 건강에 치명적인 영향을 줄 수 있는 범위• 피로 및 작업능률 저하 범위: 운전 등과 같은 작업능률 저하 범위• 안락감 감소 범위: 차안에서의 독서 식사 등의 행동에서 안락감이 감소되는
범위
• 앉은자세, 선 자세 4-8Hz z방향 가속도에 민감• 누운자세 1-2 Hz에서 민감
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5
Road roughness
Vertical Vehicle Dynamics
G: 거칠기 계수-거칠기 정도를 나타내는 거칠기 진폭W: 파동정도를 나타내는 파동계수 - 스펙트럼 밀도함수의 기울기
스펙트럼 밀도 함수
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6
Road roughness
Vertical Vehicle Dynamics
스펙트럼 밀도 함수는 일정속도 v 로 차량이주행할 때 주파수 f 의 식으로 표시 가능
동일한 도로면을 달릴때도 속도에 따라서 가진입력이 달라지는 것을 알수 있음.
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7
Road roughness
Vertical Vehicle Dynamics
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model Assumptions
- Single car body
- No wheel mass
- Tire stiffness is relatively small
compared with suspension stiffness
- Voigt-Kelvin model is used for
suspension spring and damper
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model
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Quarter Car Model
Vertical Vehicle Dynamics
• Single DOF model 현가 설계시 스프링 K 조건
• 구동력이 바퀴에 전달될 수 있도록 접지력 확보• 인체의 걷는 주파수 1-1.3 Hz 로 조정 (motion
sickness), 4-8Hz (유해한 주파수 (0.1-0.5Hz human fatigue)) 회피 설계
••
고려한 설계
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Vertical Vehicle Dynamics
• Single DOF model
Quarter Car Model
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Vertical Vehicle Dynamics
Quarter Car Model (1 DOF)
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Vertical Vehicle Dynamics
• Single DOF model
Quarter Car Model (1 DOF)
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Vertical Vehicle Dynamics
Quarter Car Model (1 DOF)
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Quarter Car Model (1 DOF)
Vertical Vehicle Dynamics
• Forced vibration – sinusoidal road input
assume
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Vertical Vehicle Dynamics
Quarter Car Model (1 DOF)• Forced vibration – sinusoidal road input
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Vertical Vehicle Dynamics
• 차체진동이 도로가진 보다 낮게 되기위해서는
고유진동수를 아래의 P점 이상 되는 방진구역에 위치
D 의 크기도 작게 (보통 D= 0.25-0.5)
•
을 높이기 위해서는 주어진 w 에 대해서 고유진동수 wo 값이
작을 수록, 일정 질량의 차량에 대해서는k 값이 작을 수록 유리 ( 3-5)
Quarter Car Model (1 DOF)• Forced vibration – sinusoidal road input
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Vertical Vehicle Dynamics
Car body acceleration vs road vibration도로 부가력
Quarter Car Model (1 DOF)• Forced vibration – sinusoidal road input
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Vertical Vehicle Dynamics
Quarter Car Model (1 DOF)
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Vertical Vehicle Dynamics
Quarter Car Model (1 DOF)
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Quarter Car Model (2 DOF model)
Vertical Vehicle Dynamics
Sprung mass
Un-sprung mass
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
Free vibration
assume
Characteristic equation
No damping case:
Undamped frequency vs. damped frequency = 5% difference
Un-sprung mass vs. sprung mass = 10% neglect un-sprung mass
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Vertical Vehicle Dynamics
No damping case:
Undamped frequency vs. dampled frequency = 5% difference
Un-sprung mass vs. sprung mass = 10% neglect un-sprung mass
Primary ride frequency for the sprung mass Damping ratio for the sprung mass
Quarter Car Model (2 DOF model)
Secondary ride frequency for the un-sprung mass Damping ratio for the un-sprung mass
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Vertical Vehicle Dynamics
Primary ride frequency for the sprung mass Damping ratio for the sprung mass
Quarter Car Model (2 DOF model)
Secondary ride frequency for the un-sprung mass Damping ratio for the un-sprung mass
Dynamic wheel force
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
Forced vibration - Sinusoidal road profile input
assume and
Frequency response function for the sprung mass
Frequency response function for the un-sprung mass
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
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Vertical Vehicle Dynamics
Frequency response function for the sprung mass Frequency response function for the un-sprung mass
Kb soft, ride comfort increase
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Vertical Vehicle Dynamics
Sprung mass FRF Un-sprung mass FRF
Cb hard, ride comfort increase
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
Forced vibration - Ramdom road profile input
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
Mb increase, ride comfort increase
Mb does not affect to dynamic axle force much
• Sprung mass variation simulation
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
• Mt does not affect to ride comfort and dynamic axle force in near the natural
frequency of the sprung mass
• Mt does affect to ride comfort and dynamic axle force in near the natural
frequency of the un-sprung mass
• Mt decrease, Ride comfort increase, dynamic force decrease
• Un-sprung mass variation simulation
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
• Suspension stiffness variation simulation
• Kb decrease, Ride comfort increase, But handling (Roll, pitch) problem
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
• Suspension damper variation simulation
• Cb hard, Accel decrease in near 1.25 Hz
• Cb soft, Accel decrease in near 1- 10 Hz
Need variable damper control according to frequency
• Cb hard, dynamic force decrease in near 10 Hz (natural
frequency of un-sprung mass) Wheel hop motion decrease
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Vertical Vehicle Dynamics
Quarter Car Model (2 DOF model)
• Tire stiffness variation simulation
• Softer tire Natural frequency of unsprung mass decrease,
• Softer tire amp. of unsprung mass decrease
Thus, Softer tire increase ride comfort and handling. However, softer tire increase
rolling resistance and tire deformation in high speed.
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Vertical Vehicle Dynamics
One track Half-Car Model (4 DOF model)
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Vertical Vehicle Dynamics
One track Half-Car Model (4 DOF model)• EQM for sprung mass for vertical motion
• EQM for sprung mass for pitch motion
• EQM for front un-sprung mass for vertical motion
• EQM for rear un-sprung mass for vertical motion