未來，高度自動駕駛汽車（SAE 4級）和全自動駕駛汽車（SAE 5級）將采用何種推進系統？考慮到自動駕駛汽車需要消耗大量電力進行數據處理，那么為了抵消這部分“自動駕駛開銷”，未來的自動駕駛汽車需要比當今車輛更高效的推進系統。根據博格華納（BorgWarner）副總裁、CTO Chris Thomas的說法，解決這個問題的成本不會低。
4月3日，在底特律舉行的SAE 2017年高效內燃發動機研討會（SAE 2017 High-Efficiency IC Engines Symposium）上，Thomas告訴在場觀眾，光是處理越來越多的傳入數據和車載數據（來自車載傳感器陣列、其他汽車、道路設施及云端），自動駕駛汽車就需要消耗1.5 kW至2.75 kW的功率。這，就是自動駕駛汽車“不為人知的小秘密”。
舉個例子，拿一輛典型的B級車來說，大約每消耗39W電力就相當于排放1g CO2。
Thomas指出，來自英特爾（Intel）和英偉達（Nvidia）的新型專用處理器可逐步減少最高90%的電力消耗。如果電力消耗水平真的可以下降90%，那么一輛常見車輛的數據處理功率需求應該在200 - 350 W左右。
“根據我們的計算，在最好的情況下，我們也僅能將每輛自動駕駛汽車的等效CO2排放水平降低至10g到20g克。”Thomas解釋說，這仍然將為車輛推進系統增加3到6%的電力負擔，嚴重影響車輛的能效表現。
“這意味著，未來自動駕駛汽車的推進系統必須比今天的好很多才行。”Thomas指出，“我們需要將BTE提升至50 - 51%。如果內燃系統的能效不能顯著提升，那么自動駕駛汽車將很難成為現實。”
盡管Thomas認為自動駕駛汽車并不會具體區分推進系統，但在未來20年中，從對冗余制動系統（及冗余電池）的需求考慮，插電式混合動力車可能是最實際的選擇。他大膽猜測，純電動汽車可能也不會在自動駕駛領域扮演重要角色。
“自動駕駛汽車的正常運行時間正在不斷增加，每天的累計行駛時間可能超過10小時，必須進行大量充電。”他解釋說，“在紐約城，出租車每天的行駛時間一般在18個小時，這同時意味著夏季每日要開18個小時的空調，冬季要開18個小時的暖氣，而只要開空調或是暖氣，純電動車的續航里程將立刻減少30到50%。因此，我覺得電動汽車可能不會出現在商用領域以外的自動駕駛汽車市場中，至少在短期內不會。”
如果城市中心地區能夠提供電池充電/更換站點等設施（類似于目前的加油站），這種情況可能會發生變化。Thomas指出，但大量電動車同時進行直流快充將導致電網壓力激增，這也是一個很實際的問題。
What type of propulsion system will power the highly automated (SAE Level 4) and fully autonomous (SAE Level 5) vehicles of the future? Such systems will need to be more efficient than those used in today’s human-driven vehicles, to offset the “autonomous overhead”—the significant amount of electrical power required for data processing alone. And they won’t be the lowest-cost solution, according to Chris Thomas, BorgWarner’s vice president and CTO.
The 1.5 kW to 2.75 kW needed just to process the increasing deluge of incoming and in-vehicle data—generated from on-board sensor arrays, from other vehicles, the infrastructure and the cloud—is “the dirty little secret” of autonomous vehicle engineering, Thomas told the audience at SAE’s 2017 High-Efficiency Engines Symposium in Detroit on April 3.
For a typical B-segment vehicle, for example, about 39 W of electricity consumed is equivalent to about one gram of CO2 emitted.
Thomas noted that new dedicated processors from Intel and Nvidia will inevitably help reduce electrical consumption by up to 90%. That means that with a 90% reduction in energy consumption, a typical vehicle’s processing power demand may be 200 to 350 W.
“By our calculations, the best case-scenario is that we’ll end up with about a 10-g to 20-g CO2 penalty per autonomous vehicle,” Thomas explained, translating into a 3-6% burden for the propulsion system and a significant “hit” to vehicle efficiency.
“That means the propulsion system has to be that much better than today’s,” he noted. “We need to get to a 50-51% BTE to make that happen. That’s not plausible without hybridization coupled with significantly more efficient combustion engines.”
While Thomas considers autonomous vehicles to be “propulsion agnostic,” the need for redundant braking systems (and redundant batteries) makes plug-in hybrids the practical prime-mover in this area for perhaps the next 20 years. He reckons battery-electric vehicles won’t play a major role in autonomous use during that period.
“The increased uptime of autonomous vehicles could mean more than 10 hours per day of operation, in which a significant amount of charging would be required,” he argues. “A typical New York cab runs 18 hours a day which means it needs 18 hours of air conditioning in the summer and 18 hours of heat in winter. In a BEV you lose 30-50% of the range when you turn the A/C or heat on. So I don’t think we’ll see BEVs used for autonomy outside of some commercial vehicles, at least in the short term.”
If battery exchanges/swapping at centralized locations were made accessible, that scenario could change if an infrastructure (similar to gas stations) were implemented, he said. DC fast charging of entire fleets of vehicles would create too great a spike in the electrical grid to be practical, Thomas noted.
Author: Lindsay Brooke
Source: SAE Automotive Engineering Magazine
在2017年高效內燃發動機研討會上，博格華納首席技術官Chris Thomas揭露了自動駕駛汽車“不為人知的小秘密”。
