📚 Case Study in Action: Analysing an Electric Scooter | 案例分析实战：电动滑板车工程分析
This hands-on case study guides you through the engineering analysis of a portable, foldable electric scooter. You will apply key concepts from the CCEA GCSE Engineering specification, including materials selection, mechanical load analysis, electronic system design, sustainability, and quality testing. By breaking down a real-world product, you can strengthen your analytical skills and understand how theoretical knowledge is used in professional engineering practice.
本实战案例将带你完整分析一台便携可折叠电动滑板车的工程设计。你将运用 CCEA GCSE 工程学科的核心概念，包括材料选择、机械载荷分析、电子系统设计、可持续性和质量测试。通过拆解一个真实产品，你能提高分析能力，并理解理论知识在职业工程实践中的应用。
1. Introduction to the Case Study | 案例导入
Electric scooters have become a popular short-distance transport solution in cities worldwide. In this case study, we examine a lightweight, folding electric scooter designed for commuters. The product must balance strength, portability, battery life, cost, and environmental responsibility. You will step through the design process, from requirements capture to final testing, exactly as an engineering team would approach the project.
电动滑板车已成为全球城市短途出行的热门解决方案。本案例研究分析一款面向通勤者的轻量可折叠电动滑板车。产品需要在强度、便携性、续航能力、成本和环境责任之间取得平衡。你将经历从需求捕获到最终测试的整个设计过程，完全仿照工程团队推进项目的方式。
2. Understanding the Design Brief | 理解设计纲要
The client specifies a foldable scooter for adults weighing up to 100 kg, with a range of at least 15 km on a single charge. It must fold in under 10 seconds and fit inside a standard car boot. The target retail price is under £300, and the scooter should be made primarily from recyclable materials to meet EU end-of-life directives.
客户要求设计一款可折叠滑板车，适用最大体重 100 kg 的成人，单次充电续航不低于 15 km。折叠操作需在 10 秒内完成，并能放入标准家用车后备箱。目标零售价低于 300 英镑，车身主要材料需使用可回收材料，以符合欧盟报废指令。
A clear design brief transforms customer needs into measurable engineering specifications. This includes a maximum static load of 980 N (100 kg x 9.8 m/s²), a minimum motor power output to maintain 25 km/h on a 5% incline, and a safe stopping distance under 4 m from 25 km/h in dry conditions. Identifying these constraints at the beginning prevents costly redesign later.
清晰的设计纲要能将客户需求转化为可量化的工程规格。包括最大静态载荷 980 N（100 kg × 9.8 m/s²）、在 5% 坡度上保持 25 km/h 的最低电机输出功率，以及干燥路面下从 25 km/h 制动至停止距离小于 4 m。早期确定这些约束条件能避免后期昂贵的返工。
3. Materials Selection for the Frame | 车架材料选择
The scooter frame must be light yet rigid. Engineers evaluated aluminium alloy 6061-T6, mild steel, and carbon-fibre reinforced polymer (CFRP). The table below compares key properties. Aluminium 6061-T6 was chosen for its excellent strength-to-weight ratio, corrosion resistance, and affordable cost compared to CFRP.
车架必须轻量化且刚性强。工程团队评估了 6061-T6 铝合金、低碳钢和碳纤维增强聚合物 (CFRP)。下表对比了关键性能。最终选择 6061-T6 铝合金，因为其优异的强度重量比、耐腐蚀性，且成本远低于 CFRP。
| Material | Density (kg/m³) | Yield Strength (MPa) | Relative Cost |
|---|---|---|---|
| Mild Steel | 7850 | 250 | Low |
| Al 6061-T6 | 2700 | 276 | Medium |
| CFRP (woven) | 1600 | 600+ | High |
In addition, aluminium can be easily extruded into complex hollow sections for the folding neck, reducing part count. Its natural anodised surface eliminates the need for paint, which simplifies recycling at end-of-life. The material choice directly supports both performance and sustainability targets.
此外，铝合金可轻松挤压成型为复杂的空心型材，用于折叠颈部，减少零件数量。其天然阳极氧化表面无需涂装，简化了报废回收过程。材料选择直接支撑了性能与可持续目标。
4. Mechanical Load Analysis | 机械载荷分析
The main load-bearing member is the aluminium deck and stem. We modelled the deck as a simply supported beam with a central point load of 980 N, corresponding to a user standing on one foot during mounting. Using the formula for maximum bending moment, M = F × L ÷ 4, where L is the distance between supports (0.6 m). Thus M = 980 N × 0.6 m ÷ 4 = 147 N·m.
主要承载部件为铝合金踏板和立管。我们将踏板建模为简支梁，中心点载荷 980 N，模拟用户上车时单脚站立。使用最大弯矩公式 M = F × L ÷ 4，其中 L 为支撑间距（0.6 m）。计算得 M = 980 N × 0.6 m ÷ 4 = 147 N·m。
Bending stress σ = M × y / I, where y is the distance from neutral axis (12.5 mm for a 25 mm thick deck) and I is the second moment of area. For a rectangular cross-section (width 120 mm, height 25 mm), I = b × h³ / 12 = 120 × 25³ ÷ 12 = 156,250 mm⁴. Then σ = (147,000 N·mm × 12.5 mm) / 156,250 mm⁴ ≈ 11.76 MPa. The safety factor, using aluminium’s yield strength of 276 MPa, is 276 / 11.76 ≈ 23.5, which is well above the typical minimum of 2.5. This confirms the deck will not yield under static load.
弯曲应力 σ = M × y / I，其中 y 为到中性轴距离（25 mm 厚踏板取 12.5 mm），I 为截面二次矩。矩形截面（宽 120 mm，高 25 mm），I = b × h³ / 12 = 120 × 25³ ÷ 12 = 156,250 mm⁴。则 σ = (147,000 N·mm × 12.5 mm) / 156,250 mm⁴ ≈ 11.76 MPa。取铝合金屈服强度 276 MPa，安全系数为 276 / 11.76 ≈ 23.5，远高于通常要求的最小值 2.5。这证实踏板在静载荷下不会屈服。
Fatigue life was also checked for repeated loading from road vibrations, using a modified Goodman diagram. The chosen material showed infinite life for stress amplitudes below 90 MPa. The actual alternating stress was estimated at around 5 MPa, predicting a virtually unlimited service life for the deck.
还通过修正 Goodman 图校核了路面振动反复加载下的疲劳寿命。该材料在应力幅低于 90 MPa 时显示无限寿命，实际交变应力估算仅约 5 MPa，预示踏板使用寿命几乎无限。
5. Electronic Systems and Motor Selection | 电子系统与电机选型
The scooter uses a 24 V brushless DC (BLDC) hub motor integrated into the front wheel. Motor selection began by calculating the required tractive force. To climb a 5% gradient at 25 km/h (6.94 m/s) with a total vehicle mass of 115 kg (rider + scooter), the force F = m × g × sinθ + rolling resistance. For small angles sinθ ≈ tanθ = 0.05. F ≈ 115 × 9.8 × 0.05 + 115 × 9.8 × 0.01 = 56.35 + 11.27 = 67.62 N. Power P = F × v = 67.62 × 6.94 ≈ 470 W electrical input, assuming 80% motor efficiency.
滑板车采用集成在前轮的 24 V 直流无刷轮毂电机。选型先计算所需牵引力。在 5% 坡度上以 25 km/h（6.94 m/s）行驶，总质量 115 kg（骑手 + 车），力 F = m × g × sinθ + 滚动阻力。小角度下 sinθ ≈ tanθ = 0.05。F ≈ 115 × 9.8 × 0.05 + 115 × 9.8 × 0.01 = 56.35 + 11.27 = 67.62 N。功率 P = F × v = 67.62 × 6.94 ≈ 470 W 电功率输入，按 80% 电机效率计算。
The controller delivers a maximum phase current of 15 A, so at 24 V the peak electrical power is 360 W, which meets the climbing requirement with a calculated 470 W for short bursts. Continuous cruising on flat ground requires only 150–200 W. The motor’s torque constant Kt is 0.1 N·m/A, giving a peak torque of 1.5 N·m, sufficient for quick acceleration.
控制器输出最大相电流 15 A，24 V 下峰值电功率 360 W，可满足短时爬坡所需的 470 W。平坦路面巡航仅需 150–200 W。电机转矩常数 Kt 为 0.1 N·m/A，峰值扭矩 1.5 N·m，足以实现快速加速。
6. Battery Technology and Energy Efficiency | 电池技术与能效
The energy storage system uses a 24 V, 10 Ah lithium-ion battery pack (Li-NMC), providing a nominal energy of 240 Wh. The target range is 15 km. We can calculate energy consumption per kilometre: motor draws approximately 7 A at cruising speed, giving 24 V × 7 A = 168 W. At 25 km/h, that is 168 Wh per 25 km, or 6.72 Wh/km. Thus the theoretical range = 240 Wh / 6.72 Wh/km ≈ 35.7 km, significantly exceeding the requirement, which leaves margin for inclines and battery degradation.
储能系统采用 24 V、10 Ah 锂离子电池组（Li-NMC），额定能量 240 Wh。目标续航 15 km。可计算每公里能耗：巡航速度电机电流约 7 A，则 24 V × 7 A = 168 W。在 25 km/h 下，即每 25 km 消耗 168 Wh，或 6.72 Wh/km。理论续航 = 240 Wh / 6.72 Wh/km ≈ 35.7 km，远超过需求，为斜坡和电池衰减留出余量。
A battery management system (BMS) monitors cell voltages, temperature, and prevents over-discharge. Energy recovery during braking (regenerative braking) can feed about 10% back into the battery, improving overall efficiency. The battery casing is IP65-rated to protect against splashes and dust, ensuring safety and longevity.
电池管理系统 (BMS) 监控电芯电压、温度并防止过放。制动能量回收（再生制动）可将约 10% 的能量回充给电池，提升整体效率。电池外壳防护等级 IP65，防溅水防尘，确保安全与寿命。
7. Manufacturing Processes | 制造工艺
The scooter employs a mix of manufacturing processes suited to volume production. The aluminium deck is extruded, then cut to length and CNC-machined for mounting holes. The folding mechanism uses precision die-cast zinc alloy parts for high strength and slim profile. The plastic deck cover is injection-moulded from ABS (acrylonitrile butadiene styrene) for durability and weather resistance.
滑板车采用适合批量生产的多种制造工艺组合。铝合金踏板经挤压成型，再切割定长并 CNC 加工安装孔。折叠机构使用精密压铸锌合金件，强度高且外形纤薄。塑料踏板盖板采用 ABS（丙烯腈-丁二烯-苯乙烯共聚物）注塑成型，具有耐久性和耐候性。
Permanent assembly methods include robotic MIG welding for the stem-to-deck joint, and structural adhesives for bonding the grip tape. Fasteners are stainless steel to resist corrosion. The electronics are assembled on a FR-4 PCB with surface-mount components, then potted in epoxy to protect against vibration. This combination balances production speed, cost, and quality.
永久连接方法包括机器人 MIG 焊接立管与踏板接头，以及使用结构胶粘贴防滑砂纸。紧固件选用不锈钢以抗腐蚀。电子部分组装在 FR-4 印刷电路板上，使用表面贴装元件，然后用环氧树脂灌封以防震动。这种组合平衡了生产速度、成本与质量。
8. Sustainability and Environmental Impact | 可持续性与环境影响
A life cycle assessment (LCA) was performed from material extraction to end-of-life. Aluminium production is energy-intensive, but the lightweight frame reduces operational energy, providing a net carbon saving over the product’s life compared to a steel frame. The Li-ion battery accounts for the highest environmental impact due to cobalt mining; the design specifies a cobalt-reduced NMC chemistry (8-1-1) to mitigate this.
进行了从材料提取到报废的全生命周期评估 (LCA)。铝生产能耗高，但轻量化车架降低了使用阶段能耗，在全生命周期内与钢车架相比，实现了净碳减排。锂离子电池因钴开采而环境影响最大；设计选用低钴 NMC 化学体系（8-1-1 配比）以缓解该问题。
At end-of-life, over 85% of scooter mass can be recycled. The aluminium frame returns to the secondary aluminium loop with only 5% energy of primary production. The BMS allows individual cell replacement, extending battery life. Packaging uses moulded recycled cardboard, eliminating polystyrene foam. These decisions reflect circular economy principles.
在报废阶段，滑板车 85% 以上的质量可回收利用。铝合金车架返回再生铝循环，仅消耗原生铝生产 5% 的能源。BMS 允许单独更换电芯，延长电池寿命。包装使用模塑再生纸板，杜绝聚苯乙烯泡沫。这些决策体现了循环经济原则。
9. Quality Control and Testing | 质量控制和测试
Before mass production, the scooter underwent a sequence of tests. Tensile tests on aluminium samples verified yield strength at 278 MPa, closely matching the specification. Stair-drop and kerb-impact simulations proved the folding latch could withstand 2000 cycles without loosening. The motor was tested on a dynamometer to confirm power output and thermal stability after 30 minutes of continuous hill-climbing.
在批量生产前，滑板车经历了一系列测试。对铝试样进行拉伸测试，验证屈服强度为 278 MPa，与规格接近。台阶跌落和路缘冲击模拟证实折叠锁扣可承受 2000 次循环不松脱。电机在测功机上测试，确认连续爬坡 30 分钟后的功率输出与热稳定性。
In production, statistical process control (SPC) is applied to the extrusion wall thickness and welding quality. Each battery pack undergoes a 100% charge-discharge test to screen for early-life failures. A final assembly test measures braking distance and verifies all electrical safety requirements according to EN 17128:2020. These measures reduce warranty returns and ensure user safety.
在生产中，对挤压壁厚和焊接质量实施统计过程控制 (SPC)。每个电池组 100% 经历充放电测试，筛查早期失效。总装测试测量制动距离，并根据 EN 17128:2020 验证所有电气安全要求。这些措施减少了质保退货并确保用户安全。
10. Product Improvement and Iteration | 产品改进与迭代
User feedback from the pilot batch highlighted excessive vibration on cobblestone streets. Engineers addressed this by adding an elastomeric bushing in the front fork, which reduced high-frequency vibration by 30%. Furthermore, they switched the controller firmware to a sinusoidal (FOC) algorithm, reducing motor noise and improving efficiency by 5%. These iterative changes were validated through a second field trial before final release.
试产批次的用户反馈指出鹅卵石路面振动过大。工程师通过在前叉增加弹性橡胶衬套解决此问题，使高频振动降低 30%。此外，将控制器固件切换为正弦波 (FOC) 算法，降低了电机噪声并提升效率 5%。这些迭代更改在最终发布前通过第二次现场试验获得验证。
The case study demonstrates that engineering is not a linear process but a cycle of design, test, analyse, and improve. By critically evaluating each subsystem, a GCSE student learns to apply scientific principles systematically, preparing for both written examinations and practical coursework tasks in CCEA Engineering.
本案例表明，工程不是线性过程，而是设计、测试、分析、改进的循环。通过批判性地评估各子系统，GCSE 学生将学会系统化应用科学原理，从而为 CCEA 工程学科的笔试和实践课业任务做好准备。
Published by TutorHao | Engineering Revision Series | aleveler.com
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