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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Issues Observed in Last Year's Suspension and Vehicle Dynamics

去年車懸吊跟車輛動態系統的問題和問題的原因：1. Inside Rear Wheel Lift During Trail Braking

  • 在trail braking時，觀察到內側後輪產生離地現象。

    The inside rear wheel was observed to lift off the ground during trail braking.

Root cause:

  • 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 too far forward. 車輛動態的可預測性低During
    trail 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braking, load transfers forward and laterally to the outside wheel. 沿用於不同尺寸輪胎的懸吊幾何，而導致rollThis center在車輛側傾時rollresulted centerin movement略大，這樣可能導致rollinsufficient moment的建立不線性normal force on 前翼在重煞時觸地the
      inside 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rear wheel, causing wheel lift.

      今年的設計目標與設計變更的原因：2. Poor Vehicle Dynamics Predictability

      • 調整車輛重心位置

        Root causes:

        • 調整方向：將重心位置靠後且降低
        • 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

        Suspension

      • 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(Rolldata inertiacalculations &were Pitchincomplete inertia)，讓車輛在極限邊緣的收復與指向更加敏捷
      and lacked a solid analytical foundation. 更完善的懸吊數據計算流程

      Suspension parameters deviated from typical ranges without supporting validation data.

      Suspension geometry designed for a different tire size was reused.

      • 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This caused excessive roll center (RC) movement during body roll.
      • 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
      Leading to nonlinear 合理的懸吊參數設定roll moment 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generation, reducing 優化懸吊幾何的作動曲線
        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 針對懸吊幾何的作動曲線我們關注的有以下幾個：
          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Roll moment的建立越線性越貼近理論數值 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Roll angle的時候外側輪的Camber接近0 deg，但輪胎並分剛體且為避免輪胎在最大側向力時有翻胎(Tire Rollover)的問題，因此我在設計幾何時將最大Camber設定在-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 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Pitch angle 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 懸吊零組件的最佳化勁度重量比
            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 減輕整車總質量(簧上+簧下)的優點：
              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。 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。 減輕簧上質量的優點：
                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。 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。predictability.

                3. Front Wing Ground Contact Under Heavy Braking

                  Under heavy braking, the front wing made contact with the ground.

                  Root cause:

                    Significant forward load transfer caused excessive front suspension compression. The resulting ride height dropped below the front wing clearance.

                    Design Objectives and Rationale for This Year

                    懸吊系統的設計流程：1. Optimization of Center of Gravity (CG)

                    Design Direction

                      Shift CG rearward and lower

                      Objectives

                      Maximize Total Tire Grip

                        Lower CG reduces load transfer:

                          Allows more even load distribution across all four tires Utilizes the nonlinear tire load sensitivity more effectively

                          Helps eliminate rear wheel lift during braking

                          Improve Stability and Control

                            Lower CG reduces:

                              Brake dive Acceleration squat

                              Mass centralization reduces:

                                Roll inertia Pitch inertia

                                Result:

                                  More responsive handling Improved recovery near the limit

                                  2. Establish a Robust Suspension Data Calculation Process

                                    Predictable vehicle dynamics must be built on:

                                      A solid theoretical foundation A systematic calculation workflow

                                      To avoid repeating previous design issues:

                                        A new suspension calculation methodology was developed from scratch

                                        3. Reasonable Suspension Parameter Selection

                                          Due to time constraints, advanced simulations were not conducted for the 9th generation car

                                          Therefore:

                                            Suspension parameters were selected based on typical benchmark values Ensuring baseline reliability and feasibility

                                            4. Optimization of Suspension Kinematic Behavior

                                            A predictable vehicle requires not only good parameter selection but also well-designed suspension kinematics.

                                            Key Focus Areas

                                            (1) Roll Center Movement

                                              Vertical RC movement during roll should be minimized

                                              Smaller RC displacement → smaller variation in CG–RC distance

                                              Result:

                                                More linear roll moment generation Better alignment with theoretical behavior

                                                (2) Camber Recovery

                                                  Objective: Maintain optimal tire contact conditions under all dynamic states

                                                  Key considerations:

                                                    Ideal: Outer wheel camber ≈ 0° at maximum roll

                                                    However:

                                                      Tires are not rigid bodies To prevent tire rollover, slight negative camber is required

                                                      Design target:

                                                        Maximum camber ≈ -0.5°

                                                        Final tuning:

                                                          Based on real-world tire wear and contact patch observations

                                                          (3) Anti-Geometry (Anti-Dive / Anti-Squat)

                                                            Governs vehicle behavior in pitch dynamics

                                                            Purpose:

                                                              Control longitudinal load transfer effects

                                                              Reduce excessive pitch angle caused by:

                                                                Aerodynamic center of pressure (CoP) Front wing ground contact

                                                                (4) Motion Ratio (Installation Ratio) Curve

                                                                Heave Motion Ratio

                                                                  Designed as progressive (non-linear) rather than linear

                                                                  Reason:

                                                                    Aerodynamic downforce increases with speed

                                                                    Benefit:

                                                                      Maintains ride height at high speeds Improves stability under high downforce
                                                                      Roll Motion Ratio

                                                                        Must be:

                                                                          Symmetrical Linear

                                                                          Ensures:

                                                                            Consistent suspension behavior in left and right turns

                                                                            5. Optimization of Stiffness-to-Weight Ratio of Suspension Components

                                                                            Importance of Structural Stiffness

                                                                              Higher stiffness reduces deviation between:

                                                                                Actual suspension behavior Theoretical kinematics

                                                                                Improves:

                                                                                  Vehicle dynamics predictability

                                                                                  Benefits of Reducing Total Vehicle Mass (Sprung + Unsprung)

                                                                                  Improved Power-to-Weight Ratio

                                                                                    Better acceleration and braking performance

                                                                                    Reduced Load Transfer

                                                                                      More even tire loading Increased cornering grip

                                                                                      Benefits of Reducing Sprung Mass

                                                                                        Direct reduction of total vehicle weight Improves overall vehicle performance

                                                                                        Benefits of Reducing Unsprung Mass

                                                                                        Improved Mechanical Grip

                                                                                          Lower inertia allows wheels to follow road surface more effectively Maintains consistent normal force

                                                                                          Faster Dynamic Response

                                                                                            Higher natural frequency of suspension system Quicker settling after disturbances More responsive steering feedback

                                                                                            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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