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Suspension design

TTR9 懸吊系統設計方向

[name=撰寫人:吳汶桓/底盤組/7~9代][color=#d904ed] 以下內容根據TTR7、TTR8懸吊系統調整與TTR9懸吊系統設計經驗。 前情提要：這邊來說一下TTR9的設計理念 可以參考一下可悲專題(數值應該是錯的(因為後來有大聰明給我設計變更...)，如果有說到相同的東西以這邊為準)，主要會著重在補充後半段的設計，也就是專題沒寫到的

前言： 在進入具體設計流程前，需先釐清本年度設計變更的核心邏輯。本隊屬於成熟的持續開發型（Iterative Development）車隊，設計方向通常依據前代車輛的實測數據、賽道表現及調校反饋進行優化。然而，受限於過去幾年疫情導致的技術交接斷層，第 6 至 8 代的懸吊設計幾乎處於停滯狀態。 與此同時，隨著賽事趨勢從內燃機（IC）轉向電動車（EV），為了建構穩定的動力平台，車輛的整備重量與軸距均大幅增加，這使我們在車輛動態條件上處於先天劣勢。面對交接斷層與架構巨變的雙重挑戰，本年度的懸吊系統採取了「歸零重構」的策略，雖在各項參數上力求嚴謹，但仍不免有待完善之處，目標在於為新一代電車架構奠定穩固的基礎。

設計變更的原因與方向Design Changes: Motivation and Direction

去年車懸吊跟車輛動態系統的問題和問題的原因：Issues in Last Year's Suspension and Vehicle Dynamics System and Their Causes:

  • 在trail braking時，觀察到內側後輪產生離地現象。

    During trail braking, inside rear wheel lift was observed.

    • 重心在錯誤的位置(靠前)，所以在帶煞入彎時重心又向前且向外側輪轉移，因而導致內側後輪沒有正向力產生後輪離地現象The center of gravity (CG) was positioned incorrectly (too far forward), so during trail braking the load transferred forward and toward the outside wheel, resulting in insufficient normal force on the inside rear wheel and causing wheel lift.
  • 車輛動態的可預測性低

    Low predictability of vehicle dynamics

    • 懸吊系統的數據計算不完善，且車輛懸吊參數設定偏離典型值，且沒有其他資料證明參數的設定The suspension data calculations were not well established, and the suspension parameters deviated from typical values without supporting validation data.
    • 沿用於不同尺寸輪胎的懸吊幾何，而導致rollSuspension center在車輛側傾時rollgeometry designed for different tire sizes was reused, resulting in relatively large roll center movement略大，這樣可能導致rollmovement moment的建立不線性during vehicle roll, which may lead to non-linear roll moment generation.
  • 前翼在重煞時觸地

    Front wing ground contact under heavy braking

    • 對於我們的車的重心位置與車輛懸吊設定，重煞時車輛的重心轉移，會導致前懸下沉量大於前翼距地高Given our vehicle’s CG position and suspension setup, load transfer during heavy braking caused front suspension compression exceeding the front wing ground clearance.

今年的設計目標與設計變更的原因：Design Objectives and Rationale for This Year:

  • 調整車輛重心位置

    Adjusting the center of gravity (CG) position

    • 調整方向：將重心位置靠後且降低Design direction: shift the CG rearward and lower it
    • 最大化總抓地力：降低重心高度可直接減少負載轉移，利用輪胎非線性特性使四輪負荷更平均，提升彎道極限並解決重煞時後輪離地的問題Maximizing total grip: lowering CG height directly reduces load transfer, allowing more even load distribution across all four tires by utilizing tire nonlinearity, improving cornering limits and resolving rear wheel lift under heavy braking
    • 提升操控穩定性：低重心能減輕煞車點頭(Dive)與加速抬頭(Squat)，配合質量的集中化降低轉動慣量(RollImproving handling stability: a lower CG reduces brake dive and acceleration squat; combined with mass centralization, it reduces roll inertia &and Pitchpitch inertia)，讓車輛在極限邊緣的收復與指向更加敏捷inertia, allowing quicker recovery and more precise response near the handling limit
  • 更完善的懸吊數據計算流程

    Establishing a more complete suspension data calculation process

    • 扎實的理論基礎與車輛動態的可預測性來源自好的數據流程推導與計算A solid theoretical foundation and predictable vehicle dynamics come from a well-structured calculation and derivation process
    • 為避免8代懸吊的動態重蹈覆轍，我選擇重新建立一套懸吊數據計算流程To avoid repeating the dynamic issues of the 8th generation suspension, a new suspension data calculation workflow was developed from scratch
  • 合理的懸吊參數設定

    Reasonable suspension parameter selection

    • 在9代車的設計過程中，由於時間進程關係我並沒有進行而外模擬來對懸吊參數設定進行模擬分析，因此我選擇參考典型值來進行設定During the design of the 9th generation car, due to time constraints, no additional simulation was conducted for suspension parameter tuning; therefore, typical reference values were adopted for parameter setup
  • 優化懸吊幾何的作動曲線

    Optimization of suspension kinematic behavior

    • 好的車輛動態可預測性，除了要有好的懸吊數據計算流程與參數設定，良好的懸吊幾何也是不可或缺的

      Good vehicle dynamics predictability requires not only a solid calculation process and reasonable parameter selection, but also well-designed suspension geometry

    • 針對懸吊幾何的作動曲線我們關注的有以下幾個：

      The following aspects of suspension kinematics were specifically considered:

      • Roll center movement：在車輛運動的期間尤其Roll的時候，我們會特別關注懸吊RC垂直的位移量，位移量越小表示CGH到RC的的距離變化越小，這表示Rollmovement: moment的建立越線性越貼近理論數值during vehicle motion, especially during roll, the vertical displacement of the roll center is closely monitored. Smaller displacement indicates smaller variation in the distance between CG and RC, resulting in more linear roll moment generation and closer alignment with theoretical behavior
      • Camber recover：在車輛的各種行為中，我們會希望輪胎在任何時時刻有著最佳的抓地力條件，最佳的抓地力條件有很多包括：胎溫、濕度、接觸面積等，從幾何角度來說我們可以控制的就是接觸面積的部分，我們會希望最大Rollrecover: angle的時候外側輪的Camber接近0in deg，但輪胎並分剛體且為避免輪胎在最大側向力時有翻胎(Tireall Rollover)的問題，因此我在設計幾何時將最大Camber設定在-vehicle states, we aim to maintain optimal tire grip conditions. These conditions include temperature, humidity, and contact patch. From a geometric perspective, we can control the contact patch. Ideally, at maximum roll angle, the outer wheel camber should be close to 0 degrees. However, since the tire is not a rigid body and to avoid tire rollover under peak lateral force, the geometry is designed with a maximum camber of approximately -0.5 deg附近，最後剩下的細部調整須由實車測試觀察胎面的情況再做細微調整degrees. Final fine-tuning is carried out through real vehicle testing by observing tire wear conditions
      • Anti-geometry：這一部分主要攸關車輛在Pitch的行為模式，在進行縱向行為的重心轉移時，我們會因為其他因素(空力CoP、前翼觸地)而需要增加Anti-geometry來抑制車身的Pitchgeometry: this mainly affects vehicle pitch behavior. During longitudinal load transfer, additional anti-geometry is required to suppress pitch angle due to factors such as aerodynamic center of pressure (CoP) and front wing ground contact
      • Motion ratio (Installation ratio) curve：這一部分由於我們有空力套件而空力系統所產生的下壓力會隨車速增加，因此我在Heavecurve: due to the presence of aerodynamic components, downforce increases with speed. Therefore, the heave motion ratio curve的部分並不是將其設計為線性，而是漸進式，這樣有利於維持高速擁有較大下壓力時的車身高度與車輛動態穩定性；而Rollcurve is designed to be progressive rather than linear, which helps maintain ride height and vehicle stability at high speed. For the roll motion ratio curve的部分，為力求在左右彎的過程懸吊系統的動態相同，因此我們須關注在左右彎的時候curve是否對稱且線性curve, symmetry and linearity between left and right turns are emphasized to ensure consistent suspension behavior
  • 懸吊零組件的最佳化勁度重量比

    Optimization of stiffness-to-weight ratio of suspension components

    • 良好的零組件系統剛度將減少懸吊系統與轉向系統作動時與理論幾何作動的誤差，將有助於進一步提升車輛動態的可預測性

      A well-designed structural stiffness reduces deviation between actual suspension/steering behavior and theoretical kinematics, improving vehicle dynamics predictability

    • 減輕整車總質量(簧上+簧下)的優點：

      Benefits of reducing total vehicle mass (sprung + unsprung):

      • 提升功重比與加減速性能：減輕簧上質量即是減輕全車總重，能直接提升推重比，縮短直線加速時間與煞車距離。Improved power-to-weight ratio and acceleration/braking performance: reducing sprung mass reduces total vehicle weight, directly improving acceleration performance and shortening braking distance
      • 降低負載轉移量：總質量的減輕會降低過彎與前後俯仰時的動態負載轉移，使輪胎更均勻地分擔壓力，進而提高彎道的總極限抓地力。Reduced load transfer: lower total mass reduces dynamic load transfer during cornering and pitch motion, allowing more even tire loading and increasing total grip
    • 減輕簧上質量的優點：

      Benefits of reducing unsprung mass:

      • 最大化機械抓地力：減輕簧下質量可大幅降低往復慣性，使輪胎能更迅速反應路面起伏，確保持續穩定的接地正向力。Maximizing mechanical grip: reduced unsprung mass lowers inertia, allowing the tire to follow road surface variations more effectively and maintain stable normal force
      • 提升動態響應頻率：減少移動質量能提高懸吊系統的自然頻率，縮短避震器作動後的穩定時間，讓轉向與路感更為敏捷直接。Improved dynamic response frequency: reducing moving mass increases the natural frequency of the suspension system, shortens settling time, and provides more responsive steering feedback

懸吊系統的設計流程：Suspension System Design Process:

1.Vehicle parameter calculation and setup

I. Vehicle static parameter calculation and setup

  • Vehicle overall layout adjustment and center of gravity calculation

II. Vehicle dynamic parameter calculation and setup

  • Maximum G-forces and wheel loads during acceleration, braking, and cornering
  • Wheel loads, roll moment, and roll moment distribution during steady-state cornering at the limit

2. Suspension system parameter calculation and setup

I. Vehicle dynamic characteristics parameter

  • Total ground clearance
    • Heave motion
    • Roll motion
  • Ride rate
  • Wheel rate (Wheel center rate)
  • Sprung mass natural frequency
  • Unsprung mass natural frequency
  • Body roll angle
  • Roll gradient
  • Roll rate

II. Suspension parameter setup

  • Heave motion
    • Heave spring rate
    • Heave damping coefficient
    • Heave installation ratio (motion ratio)
  • Roll motion
    • Roll spring rate
    • Roll damping coefficient
    • Roll installation ratio (motion ratio)

3.Suspension geometry design and optimization

I. Front view

  • Scrub radius
  • King pin inclination
  • Roll camber recover
  • Roll center movement

II. Side view

  • Caster angle
  • Caster trail (mechanical trail)
  • Pitch angle
  • Pitch center height
  • Anti-geometry
    • Anti-dive
    • Anti-squat
    • Anti-lift

III. Rocker system

  • Heave installation ratio curve
  • Roll installation ratio curve

4.Suspension component design and optimization

I. FEA- Stress analysis & Fatigue analysis II. Topology- Optimized stiffness-to-weight ratio III. Component lightweighting

5.3D print functional check & prototype

I. Interference check during actuation

6.Vehicle fabrication

7.Vehicle testing and theory validation

I. Functional Check

  • Verified proper operation of steering, braking, and suspension systems
  • Checked for interference and abnormal actuation in all mechanisms

II. Static Inspection

  • Measured suspension geometry (camber, toe, ride height)
  • Verified vehicle weight and weight distribution
  • Inspected structural integrity and assembly quality

III. Dynamic Testing

  • Conducted straight-line acceleration and braking tests
  • Evaluated low-speed handling (skidpad / slalom)
  • Assessed high-speed stability and steering response

IV. Data Acquisition & Analysis

  • Collected data on vehicle speed, acceleration, steering angle, and damper travel
  • Analyzed discrepancies between vehicle behavior and design targets

V. Feedback & Iteration

  • Adjusted setup parameters (damping, weight distribution, tire pressure)
  • Performed design modifications when necessary
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