Jserv's blog

揭露 Challenge X 設計

之前的 blog [Challenge X：Crossover to Sustainable Mobility] 提到這個為期三年、由美國能源部、GM、Freescale、National Instruments 等單位贊助的大型競賽 [Challenge X]，以降低油電混合車的能源使用量，今年已經是最後一年。Automotive DesignLine 日前張貼兩篇不錯的報導：

• [start:Student engineers develop and test a hybrid power train: Part 1 - the model ]
• [start:Student engineers develop and test a hybrid power train: Part 2 - the controller]

該文由 [Rose-Hulman Institute of Technology] 的 Matthew DeVries 所撰寫，揭露其團隊的設計，採用的能源分離架構圖如下： (click to enlarge)

整合了柴油 ICE (internal combustion engine) 與兩個電子機構，可透過三維 PGS (planetary gear-set) 以馬達或發電機為動力操作，而油電混合引擎的控制器充滿工程技術挑戰，文章提到一些細節，如：

Because this tool is event driven, we implemented a 100 Hz system clock for a rising-edge trigger.< br /> System information (including vehicle speed, battery SOC and current, throttle demand, diesel engine status, and motor/generator M1 and M2 operational parameters) was fed into the controller and state changes determined. For example, when the vehicle was initially turned on, the controller would use the SOC to decide whether to start the engine to charge the battery. After shifting into forward, throttle demand, vehicle speed, and SOC would be used to determine if and when to start the engine.
...
With the ability to plot and review every signal in our model, hazards and issues were easily identified and, usually, quickly resolved. For instance, a battery voltage or current spike was typically caused by, or resulted in, an electric motor oscillation. Implementation of proportional-integral (PI) control rather than just proportional (P) control smoothed the current flow, thus preventing damage to our battery and motors.

所引出的參考資料充斥著大量的機械與自動控制術語，對我來說有點難度，但可窺見技術挑戰：

With real-world limits in building the vehicle, our team had to rely upon simulations for all performance testing. The built-in optimization tools in Simulink minimized 0-60 mph and 50-70 mph acceleration times by adjusting the parameters that caused the engine to start and split the battery's power between M1 and M2. Although 0-60 mph time was poor at nearly 13 sec, we were able to reduce 50-70 mph time to around 4 sec, instead of the stock vehicle's 6.4 sec.

With fuel economy another important metric, a balance between economy and performance also had to be found. Just how important was it? Our pre-competition goal was an ambitious 40 mpgge (miles per gallon gasoline equivalent). During competition we achieved about 32 mpgge, compared to the stock vehicle's 24 mpgge.

The last big hurdle the vehicle had to overcome was being able to tow a 2,500 lb trailer on California's Baker Grade on Interstate 15 at 60 mph (7% grade for 15 miles). While we had been working hard to optimize our fuel efficiency, we never tested a trailer tow, as our engine had more than enough power to pull the trailer "up a wall." When we ran a simulation using our controller, however, we found that our vehicle wouldn't make it up to 60 mph on the grade.

善用 Simulink 一類的自動化建模與模擬工具，有效提昇該團隊的開發，同時也看到 [Challenge X] 即將對汽車工業帶來新的機會，期望不久的將來，得以藉此兼顧環保與交通的便利性。
由 jserv 發表於 April 17, 2007 04:02 PM