外文翻譯--汽車變速器控制面臨的機(jī)遇和挑戰(zhàn)

Appendix Challenges and Opportunities in Automotive Transmission Control Zongxuan Sun and Kumar Hebbale Research and Development Center General Motors Corporation Warren, MI 48090 Abstract: Automotive transmission is a key element in the powertrain that connects the power source to the wheels of a vehicle. To improve fuel economy, reduce emission and enhance driving performance, many new technologies have been introduced in the transmission area in recent years. This paper first reviews different types of automotive transmissions and explains their unique control characteristics. We then address the challenges facing automotive transmission control from three aspects: calibration, shift scheduling, and sensing, actuation and electronics. Along the way, research opportunists to further improve system performance are discussed. 1. Introduction to the Latest Automotive Transmission Technologies To improve fuel economy, reduce emission and enhance performance, automotive manufacturers have been developing new technologies for powertrain systems. In the transmission area, emerging technologies 1 such as continuously variable transmission (CVT), dual clutch transmission (DCT), automated manual transmission (AMT) and electrically variable transmission (EVT) have appeared in the market, which is traditionally dominated by step gear automatic transmission (AT) and manual transmission (MT). Among many different technical challenges for developing these new transmissions, system dynamics and control are crucial to realizing the fuel economy and emission benefits while providing superior performance. The basic function of any type of automotive transmission is to transfer the engine torque to the vehicle with the desired ratio smoothly and efficiently. The most common control devices inside the transmission are clutches and hydraulic pistons. Such clutches could be hydraulic actuated, motor driven or actuated using other means (see Figure 1). Therefore clutch/piston control is essential for transmission operation. In both DCT and AMT, clutch control is the key to ensure smooth torque transfer. In CVT, hydraulic piston control is crucial for not only system performance but also device durability. In many of the new automatic transmissions (AT), clutch-to-clutch shift is adopted to reduce the cost and improve packaging. This involves electronic control of both the oncoming and off going clutches and the timing and coordination between them. In addition to eliminating the shift valves, accumulators, etc., clutch-to-clutch control eliminates the coasting clutches and freewheelers, greatly simplifying the transmission mechanical content. The absence of these devices makes the robust control of clutch-to-clutch shifts a challenge. Figure 1. Schematic Diagram of a Clutch With the traditional control system in an automatic transmission with clutch-to-clutch shifts, the oncoming clutch fill process is a major source of uncertainty and it makes the clutch coordination during the shift a difficult task. The fill time of the oncoming clutch varies due to many factors, such as, fluid temperature, solenoid valve characteristics, line pressure variations, and time elapsed between shifts. The commanded fill pressure and the commanded fill time are critical to achieving a good fill and a smooth start to the shift process. Even small errors in calculating these two parameters could lead to an overfill or an under fill, as shown schematically in Figure 2. Some algorithms have been developed to detect the end of fill using speed signals, but none of them has proven reliable and fast enough to prevent overfill spikes. An example of an oncoming clutch overfill during an upshift is shown in Figure 3. The oncoming clutch pressure shows a slight overfill, which results in shift tie-up, causing engine pull down and a big drop in the output torque. A more robust off going clutch control was necessary in this example to avoid a tie-up. While the overfill can be corrected using adaptive schemes for future shifts, the real challenge is in preventing it from happening in the first place. Figure 2. Variations in Clutch Fill Process Figure 3. Effect of Clutch Overfill on an Upshift Currently in most clutch-to-clutch shift production transmissions, the clutch coordination is accomplished by a combination of open-loop, event-driven, and feedback control schemes. Transmission input and output speeds are the primary measured variables used in this control. An adaptive system is used to compensate for shift-to-shift variations and build-to-build variations 2. Recently, an integrated torque based approach using both engine and transmission handles has been proposed. The main difficulty with the torque approach has been in the area of clutch coordination and consequently, consistent shift quality. The automated manual transmissions (AMT) have become popular in Europe. In North America, their potential use is limited because of the torque interruption during shifts that is inherent to their designs. An offshoot of the AMT is the dual input clutch transmissions (DCT), which use two input clutches one for odd gears and one for even gears. DCTs can transmit torque continuously through the shift. All the control issues and challenges during launch and shifts confronting the friction launch transmissions (FL) are also inherent to DCTs. A DCT requires much more calibration work than conventional torque-converter automatics and would be expected to be less refined in drive ability, even in production. On the other hand, because DCTs have more calibration handles, they can be varied to fit different vehicle specifications and different driving conditions. One of the control challenges with torque-converter-less transmissions such as DCT and FL is highlighted in Figure 4. With an undamped driveline, a transient such as a shift event could trigger undesirable oscillations in the driveline, as indicated by the output torque trace. In a friction launch (starting clutch) transmission, the absence of the torque converter leaves the driveline with no hydraulic damping, and consequently, poses many control challenges including vehicle launch feel, undamped behavior during shifts and tip-in / tip-out maneuvers. Without using expensive torque or pressure sensors, the control of a clutch emulating a torque converter is a major challenge. Both hydraulic clutch 3 and magneto rheological fluid clutch implementations have been investigated by researchers. Continuously variable transmissions (CVT) enable the engine to operate in a wide range of speed and load conditions independently from the speed and load requests of the vehicle 4. This feature allows the engine to operate in the optimal region virtually independent of the vehicle speed to maximize the fuel efficiency. Different types of CVT have appeared in the market. The belt and chain drive CVTs use the hydraulic piston to control the sheave position and thus the input-output ratio. The major control challenge is to maintain optimal clamping force to prevent slipping while providing fast ratio control to maximize the fuel economy benefit. Toroidal traction drive transmissions (TCVT) have been examined by many manufacturers as promising alternatives to chain or belt CVTs. TCVTs offer a larger torque capacity and a quicker ratio change capability. A half-toroidal CVT system is unstable under open-loop operation and hence a speed ratio control system is necessary 5. In addition, when a CVT incorporates the geared neutral concept, it eliminates the need for launching devices, such as torque converters and slipping clutches. At the geared neutral point, speed ratio control becomes inadequate and output torque control is required. The control challenges in a TCVT are highlighted in 6-7. Figure 4. Effect of Controlled Damping after an Upshift Electrically variable transmissions (EVT) have appeared in the market recently. The advantages of using electric machines, namely motors/generators, with planetary gear sets include flexibility, controllability, and better performance. Great efforts have been made to extend speed ratio coverage by exploring various planetary gear train arrangements and by exploring regime shift similar to that used in step transmissions. These designs, in general, are quite complex in construction as they involve a number of planetary gear sets and clutches. Elaborate control schemes are required to ensure synchronized regime shift and avoid abrupt torque changes at the output during shifting 8-9. The control algorithms will ultimately determine how drivers perceive hybrid vehicle performance, particularly whether they notice when the vehicle switches back and forth between the electric motor and the engine. Hybrid vehicles may just be a stop-gap technology before conventional internal combustion engines are replaced by fuel-cell propulsion systems. In fuel-cell vehicles, electric motors inside the wheels may completely eliminate the need for transmissions and change the dominant technology in the future 10. 2. Transmission Control Algorithms and Hardware Development Look-up tables with calibrated variables are widely used in automotive transmission control. With the increased functionalities and electronic components, system calibration complexity goes up quickly. This is caused not only by the electronic control of the transmission, but also the coordination with engine and other components in the driveline. For example, with the increasing number of gear ratios in automatic transmissions, the number of variables to be calibrated to realize smooth shifts under all driving conditions goes up quickly. To greatly reduce the development time and improve performance, an automated and systematic approach is required for the calibration process. First, automated tuning process was investigated to calibrate the transmission automatically with little or no human interference. An automated tool set was developed to calibrate automotive powertrain without human-in-the-loop 11. An adaptive online design of experiments (DOE) approach was developed for GDI engine calibration 12. This approach enables the efficient experimental design for nonlinear systems with irregularly shaped operating regions. The same principle can be applied to the automotive transmission calibration. Second, model based control was proposed as an enabler to reduce the number of calibration variables and consequently, the calibration effort and time. However, the uncertain environment and wide operation range present a major challenge to system robustness. The transmission temperature can vary from 40 degree C to 150 degree C, which in turn affects the automatic transmission fluid (ATF) properties. The wide range of operation from completely stopped to rotating at high speed with high load demands precise models and high bandwidth controls. Reference 13 described procedures for determining a set of linearized models and the associated unmolded dynamics for the torque converter clutch in the automatic transmission and applied robust control design to achieve desired performance. Detailed procedures for the development of transmission models for controlling the inertia phase during a shift were presented in 14. Based on these models, robust control can be designed to achieve desirable shift performance regardless of the engine load, ATF viscosity, etc. Variable structure control (VSC) was also investigated for clutch control in an automated manual transmission 15. Results show that VSC control is able to maintain system robustness within the uncertain environment. Third, adaptive learning control was developed to accommodate the uncertain environment and different driving patterns. Artificial neural network (ANN) was employed to model the automotive powertrain using the black-box approach 16. Input and output data are used to train the ANN to emulate the functions of the transmission and its subsystems. A distinctive feature of this approach is that it can emulate not only the steady state operation but also the dynamic/transient operation of the system. The key advantages of this approach include online training using real-time vehicle data and adaptive calibration or control capability. As more number of speeds is added to the transmissions, shift schedule gets more complicated. Since traditional shift schedule only considers vehicle speed and throttle angle to determine shift points, shift busyness has become a concern under certain road conditions, such as hilly terrains. For example, during a winding uphill driving, the driver releases the gas pedal before entering the curve to reduce vehicle speed, and traditional shift schedule may perform an upshift in response to the throttle change. But right after the curve, the driver needs to step into the gas pedal to increase vehicle speed and a down shift may then be executed. Similarly during a downhill driving, an upshift is performed by the traditional shift schedule when throttle angle is decreased, thus unpleasantly reducing the engine brake. By including factors such as road grade, steering angle, vehicle acceleration, etc., flexible shift schedule that is pleasing to the customers and favorable for fuel economy must be developed. Shift busyness avoidance control using fuzzy sets and neural networks have been investigated in the past 17-18. Most of the adaptive shift point algorithms presented in the literature require some knowledge of the mass of the vehicle and the gradient of the road on which the vehicle is travelling. A reliable mass estimation algorithm is lacking in the literature. With good mass information, the estimation of the road grade is straight forward. Recently vehicle navigation system was used to provide some preview information on the road shape and conditions during the shift scheduling process 19. Recent work 20 on shift scheduling also added feedback learning to the fuzzy logic system to update the membership function in real-time to better accommodate different driving patterns. They also extended the work to include not only the AT, but also the AMT, DCT and CVT. A block diagram summarizing the general structure used in gear shift scheduling is shown in Figure 5. Figure 5. Block Diagram of the Gear Shift Scheduling Algorithm To accommodate the ever-increasing demand for computational power, sensing and actuation capabilities, transmission control hardware has been undergoing many changes. Those changes involve all three levels of complexities: the sensing level, the actuation level, and the system level. At the sensing level, new sensing technologies have been pursued to either improve the performance and efficiency of current hardware or enable new actuation technologies. Pressure switches and temperature sensors are used in current production transmissions. To optimize transmission operation, pressure sensor and torque sensor are desirable. The main challenges for introducing these sensors into production units are cost and durability. A piezoresistive semiconductor pressure sensor was evaluated for automotive applications 21. It claims to measure pressures up to 3.5Mpa within +/- 1% of the full scale. Early work on torque sensors can be traced back to early 80s when researchers 22 investigated a non-contact miniature torque sensor for automotive transmissions. Recently magneto elastic torque sensors have been investigated by a number of researchers 23-24. The phenomenon of inverse-magnetostriction that converts material strain into magnetic property changes was exploited to measure transmitted torque. To overcome the harsh environment inside the transmission, special coating technologies were developed to protect the sensing element. A clutch disk integrated torque sensor was also proposed for automotive applications 25. The sensing elements are integrated in the clutch plate to achieve precise and robust measurement. At the actuation level, solenoid valve control technologies were investigated to improve controllability and flexibility of the hydraulic system. For clutch actuation, variable bleed solenoid (VBS) valves are widely used now in place of the pulse width modulation (PWM) valves for better controllability. However, VBS valves suffer from hysteresis and variations due to temperature. Analytical modeling of proportional control solenoid valves was conducted using system identification theory 26. It concludes that the valve bandwidth was limited by the bandwidth of the electromagnetic portion the solenoid. To further enhance system performance, fast and precise valve actuation devices are needed. A new concept 27 for an on/off valve with rotary actuator was proposed to handle flow rate greater than 10lpm with less than 5ms response time. A key feature of this concept is that the valve has a single stage construction, but performs as a two-stage valve. Alternative clutch actuation technologies were also pursued to replace the electro-hydraulic actuators in automatic transmissions to improve fuel economy and performance. Motor driven clutch actuation has been investigated by a number of researchers 28. The major challenges for the electromechanical actuators are the low power density and available electrical power inside the vehicle. Usually some kind of gearing is required to amplify the torque capacity of the motor. Smart material based clutch actuation devices were also developed by a number of researchers. Feasibility of using electro rheological (ER) fluid clutch inside automotive transmission was investigated and desirable properties of ER fluid were proposed for future research 29. Magnetic powder clutch was used as a starting clutch for a CVT equipped vehicle 30. Potential applications of magneto rheological (MR) fluid clutch were discussed in 31. At the system level, there is a new trend of migrating the control electronics from passenger compartment to the transmission case or even integrate the electronics inside the gear box to reduce cost and improve performance and quality 32-33. A new terminology called mechatronic transmission 34 was coined recently to illustrate the integration of control electronics with the transmission device itself. Besides cost and quality benefits, this approach will enable the testing and calibration of the transmission devices right on the assembly line. To enable the gearbox-integrated electronics, new electronic integration and packaging technologies were also investigated to overcome the harsh environment inside the gearbox 35. 3. Conclusions In order to realize maximum fuel economy benefit and provide superior performance, research and development in both control software/algorithm and hardware are required for the automotive transmissions. With the enhanced functionality and increased complexity in both software and hardware, system integration is the key for successful transmission development. References: 1. Wagner, G., “Application of Transmission Systems for Different Driveline Configurations in Passenger Cars”, SAE Technical Paper 2001-01-0882. 2. Hebbale, K.V. and Kao, C.-K., Adaptive Control of Shifts in Automatic Transmissions, Proceedings of the 1995 ASME International Mechanical Engineering Congress and Exposition, San Francisco, CA, 1995. 3. Kao, C. K., Smith, A. L. and Usoro, P. B., “Fuel Economy and Performance Potential of a Five-Speed 4T60-E Starting Clutch Automatic Transmission Vehicle”, SAE Technical Paper 2003-01-0246. 4. Kluger, M. and Fussner, D., “An Overview of Current CVT Mechanisms, Forces and Efficiencies”, SAE Technical Paper 970688. 5. 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Nagur, N. and Takemura, S., “Development of Small, High Performance Electronics Control Units with Metal Based Printed Circuit Board”, SAE Technical Paper 961023. 附錄 1 汽車變速器控制面臨的機(jī)遇和挑戰(zhàn) Zongxuan Sun and Kumar Hebbale Research and Development Center General Motors Corporation Warren, MI 48090 摘要：在動(dòng)力系統(tǒng)中，汽車變速器是連接動(dòng)力源和車輪的關(guān)鍵部位。為了提高燃油經(jīng)濟(jì)性、降低排放及增強(qiáng)驅(qū)動(dòng)性能，近幾年來(lái)，許多新的技術(shù)已經(jīng)在變速器領(lǐng)域出現(xiàn)了。本文首先介紹了不同類型的汽車變速器，并闡述了它們各自獨(dú)特的控制特點(diǎn)。接著，我們又討論了在汽車變速器控制上來(lái)自三個(gè)方面的挑戰(zhàn)：校準(zhǔn)、轉(zhuǎn)換調(diào)度，傳感、驅(qū)動(dòng)和電子技術(shù)。同時(shí)，我們研究了如何進(jìn)一步改善傳動(dòng)系統(tǒng)性能。 1.介紹先進(jìn)的汽車變速器技術(shù) 為了提高燃油經(jīng)濟(jì)性，減少?gòu)U氣排放及提高性能，汽車制造商一直都在開(kāi)發(fā)新的動(dòng)力傳動(dòng)技術(shù)。在變速器領(lǐng)域，新興的技術(shù)，如傳動(dòng)比連續(xù)變化的無(wú)級(jí)變速器（ CVT），雙離合器變速箱（ DCT），自動(dòng)手動(dòng)的綜合變速器（ AMT）和電動(dòng)無(wú)級(jí)變速器（ EVT）已經(jīng)在由齒輪自動(dòng)變速器（ AT）和手動(dòng)變速器（ MT） 居于主導(dǎo)地位的市場(chǎng)上出現(xiàn)了。在眾多不同的開(kāi)發(fā)這些新型變速器的技術(shù)挑戰(zhàn)中，系統(tǒng)動(dòng)力和控制在提供優(yōu)越的性能的同時(shí)，對(duì)實(shí)現(xiàn)燃油經(jīng)濟(jì)性及排放優(yōu)勢(shì)也起到了關(guān)鍵的作用。 任何形式的自動(dòng)變速器的基本功能就是將發(fā)動(dòng)機(jī)的轉(zhuǎn)矩平穩(wěn)有效地傳遞到具有要求的傳動(dòng)比的汽車上。最常見(jiàn)的變速器控制裝置是離合器和液壓活塞。這些離合器由液力驅(qū)動(dòng)，馬達(dá)驅(qū)動(dòng)或由其他方式驅(qū)動(dòng)（見(jiàn)圖 1）。因此，離合器 /活塞控制對(duì)傳動(dòng)操作是必不可少的。在 DCT 和 AMT 中，離合器是確保轉(zhuǎn)矩平穩(wěn)傳遞的關(guān)鍵。在 CVT 中，液壓活塞控制對(duì)系統(tǒng)性能和設(shè)備的耐用性都很重要。在許多新 型自動(dòng)變速器（ AT）中，采用離合器對(duì)離合器轉(zhuǎn)換降低了成本、改進(jìn)了包裝。這不僅涉及到即將到來(lái)的和就要過(guò)時(shí)的離合器，而且涉及到它們之間正時(shí)和協(xié)調(diào)的電子控制。除了淘汰這種轉(zhuǎn)變閥門和蓄電池等，離合器對(duì)離合器控制也減少了滑行離合器和自由輪，大大簡(jiǎn)化了機(jī)械傳動(dòng)的內(nèi)容。取消這些裝置使對(duì)離合器到離合器轉(zhuǎn)換的控制成為一種挑戰(zhàn)。 伴隨著具有離合器對(duì)離合器轉(zhuǎn)換的自動(dòng)變速器的傳統(tǒng)控制系統(tǒng)，這種即將到來(lái)的離合器填充過(guò)程是一個(gè)不確定性的主要來(lái)源，它使在轉(zhuǎn)變過(guò)程中協(xié)調(diào)離合器成為一項(xiàng)艱巨 的任務(wù)。即將到來(lái)的離合器填充時(shí)間會(huì)受許多因素的影響 而發(fā)生變化，如液體的溫度， Return Spring 回位彈簧 Piston 活塞 Hydraulic Fluid Inlet 液壓流體入口 Clutch Pack 離合器踏板 圖 1 離合器示意圖 電磁閥的特點(diǎn)，線壓力變化和轉(zhuǎn)變過(guò)程中流逝的時(shí)間。要求的填充壓力和填充時(shí)間對(duì)于在轉(zhuǎn)變過(guò)程中實(shí)現(xiàn)良好的填充和平穩(wěn)的開(kāi)始過(guò)程是至關(guān)重要的。即使在計(jì)算這兩個(gè)參數(shù)的過(guò)程中發(fā)生的微小錯(cuò)誤也可能導(dǎo)致過(guò)滿或底部填充，就像圖 2示意的那樣。有些算法已發(fā)展到能夠探測(cè)出使用高速信號(hào)填沖的終端，但是它們中沒(méi)有一個(gè)被證明是可靠的及足夠快 去防止尖峰過(guò)滿。圖 3 顯示了在掛高速擋的過(guò)程中即將發(fā)生的離合器過(guò)滿的例子。那個(gè)即將來(lái)臨的離合器壓有輕微的溢流現(xiàn)象，這會(huì)產(chǎn)生轉(zhuǎn)換過(guò)程中的連鎖反應(yīng)，導(dǎo)致引擎下拉和輸出轉(zhuǎn)矩的大幅度下降。在這個(gè)例子中為了避免這些連鎖反應(yīng)需要更強(qiáng)大的離合器控制。盡管在未來(lái)的調(diào)整中可以使用適應(yīng)性計(jì)劃去更正過(guò)滿現(xiàn)象，但是真正的挑戰(zhàn)是如何在第一地點(diǎn)阻止它發(fā)生。 圖 2 離合器 充滿 過(guò)程中的變化 在目前大多數(shù)離合器對(duì)離合器轉(zhuǎn)變的變速器中，由于開(kāi)環(huán)控制、驅(qū)動(dòng)控制和反饋控制方法的結(jié)合，離合器的協(xié)調(diào)配合得以實(shí)現(xiàn)。在這種控制中，變速 器的輸入輸出轉(zhuǎn)速是主要的測(cè)量對(duì)象。一個(gè)自適應(yīng)系統(tǒng)主要用于補(bǔ)償轉(zhuǎn)換和開(kāi)發(fā)過(guò)程中的變化 2。近來(lái)，已經(jīng)有人提出同時(shí)使用發(fā)動(dòng)機(jī)和變速器產(chǎn)生混合扭矩的想法。這種產(chǎn)生扭矩的方法所面臨的主要難題在于如何保證離合器協(xié)調(diào)和持續(xù)的轉(zhuǎn)換質(zhì)量。 自動(dòng)手動(dòng)變速器（ AMT）在歐洲已經(jīng)開(kāi)始受到歡迎。由于自身的設(shè)計(jì)使得在轉(zhuǎn)換過(guò)程中扭矩中斷，造成這種變速器在北美潛在的發(fā)展空間變得有限。 AMT 的一個(gè)分支是雙輸入離合器變速箱（ DCT），它使用兩個(gè)輸入離合器 一個(gè)適用于具有單數(shù)齒輪的變速箱，一個(gè)適用于具有雙數(shù)齒輪的變速箱。 DCT 可以在轉(zhuǎn)換過(guò) 程中持續(xù)傳輸扭矩。在面臨摩擦啟動(dòng) (FL)的啟動(dòng)和轉(zhuǎn)換過(guò)程中， DCT 遇到的所有控制方面的問(wèn)題和挑戰(zhàn)也在于它自身的設(shè)計(jì)。一臺(tái) DCT 比傳統(tǒng)的液力變矩器自動(dòng)變速器需要更多的校核工作，同時(shí)人們也希望 DCT 能夠在生產(chǎn)和操控方面所需要的完善工作更少。另一方面，因?yàn)?DCT 需要更多的校準(zhǔn)處理，所以它們可以不斷變化以適用于不同規(guī)格和不同行駛條件的汽車。在 DCT 和 FL 中，較少的變矩器傳輸在控制方面面臨的一個(gè)挑戰(zhàn)顯示在圖 4 中。具有阻尼傳動(dòng)系統(tǒng)的短暫變化，比如說(shuō)轉(zhuǎn)換過(guò)程，能夠觸發(fā)傳動(dòng)系統(tǒng)不良震蕩，正如明顯的輸出轉(zhuǎn)矩跟蹤。 圖 3 離合器溢流 對(duì)升擋 的影響 在摩擦啟動(dòng)（單向離合器）的傳輸中，沒(méi)有液力變矩器使得液壓傳動(dòng)系統(tǒng)沒(méi)有阻尼，由此帶來(lái)許多控制方面的挑戰(zhàn)，包括汽車啟動(dòng)時(shí)駕駛員的感覺(jué)，以及在轉(zhuǎn)換和模擬過(guò)程中的阻尼情形。不使用昂貴的扭矩或壓力傳感器，操控一臺(tái)具有模擬變矩器的離合器是一個(gè)重大挑戰(zhàn)。而對(duì)于液壓離合器和磁流變液離合器實(shí)現(xiàn)的可能性，研究人員已經(jīng)進(jìn)行了調(diào)查研究。 傳動(dòng)比連續(xù)變化的無(wú)級(jí)變速器（ CVT）使得發(fā)動(dòng)機(jī)能夠在很大的速度和承載范圍內(nèi)運(yùn)轉(zhuǎn)，而不受車輛的速度和承載要求的限制 4。此功能允許發(fā)動(dòng)機(jī)能夠不受車輛速度的影響 ，而在最佳的范圍內(nèi)運(yùn)轉(zhuǎn)以實(shí)現(xiàn)最大限度地提高燃油利用率。市場(chǎng)上已經(jīng)出現(xiàn)了不同種類的無(wú)級(jí)變速器。皮帶和鏈傳動(dòng)的無(wú)級(jí)變速器使用液壓活塞來(lái)保證繩輪在變速器中的地位和投入產(chǎn)出比。主要的控制挑戰(zhàn)是在力求用快速的比例控制實(shí)現(xiàn)最大限度地提高燃油經(jīng)濟(jì)性的同時(shí)，如何保持最佳的加緊力去防止打滑。環(huán)形牽引驅(qū)動(dòng)變速器（ TCVT）已經(jīng)被許多制造商視為鏈或帶式無(wú)級(jí)變速器的理想的替代品。環(huán)形牽引驅(qū)動(dòng)變速器能夠提供更大的扭矩和更快的比例變化能力。一個(gè)半環(huán)形的無(wú)級(jí)變速器在開(kāi)環(huán)運(yùn)作的情況下 圖 4 受控 阻尼上 移后 的 效果 是不穩(wěn)定的，從而需要一個(gè)速比控制系統(tǒng) 5。此外，當(dāng)無(wú)級(jí)變速器采用齒輪傳動(dòng)中性的概念時(shí)，它就不再需要啟動(dòng)裝置，例如液力變矩器和打滑離合器。在齒輪中性傳動(dòng)時(shí)，速比控制變得不足，從而需要對(duì)輸出力矩進(jìn)行控制。在環(huán)形牽引驅(qū)動(dòng)變速器中，控制方面的挑戰(zhàn)凸顯在 6-7。 電動(dòng)無(wú)級(jí)變速器（ EVT）最近在市場(chǎng)上已經(jīng)出現(xiàn)了。使用具有行星齒輪裝置的電動(dòng)機(jī)械，即電動(dòng)機(jī) /發(fā)電機(jī)，它的優(yōu)點(diǎn)包括靈活性，可控性和更好的性能。通過(guò)探索行星齒輪傳動(dòng)方式和與在步傳輸中類似的轉(zhuǎn)變?cè)瓌t盡最大的努力來(lái)擴(kuò)大速比范圍。這些設(shè)計(jì)，一般來(lái)說(shuō)， 是相當(dāng)復(fù)雜的工程，因?yàn)樗鼈円婕霸S多的行星齒輪裝置和離合器。精心的控制計(jì)劃必須確保相應(yīng)的轉(zhuǎn)換原則和避免在轉(zhuǎn)換期間輸出端扭矩的突然變化 8-9。這種控制算法將最終決定司機(jī)感知混合動(dòng)力汽車的性能如何，特別是當(dāng)車輛在電動(dòng)機(jī)和發(fā)動(dòng)機(jī)之間來(lái)回切換時(shí)他們是否能準(zhǔn)確感覺(jué)到。在傳統(tǒng)的內(nèi)燃機(jī)逐漸被燃料電池推進(jìn)系統(tǒng)取代之前，混合動(dòng)力汽車可能只是一個(gè)權(quán)宜之計(jì)。在燃料電池汽車中，電輪轂電機(jī)內(nèi)可完全消除對(duì)變速器的需要和改變未來(lái)的主導(dǎo)技術(shù) 10。 2.傳輸控制算法和硬件發(fā)展 具有矯正變量的查詢表廣泛應(yīng)用于汽車變速器控制中。隨著功 能和電子部件的增加，系統(tǒng)校準(zhǔn)的復(fù)雜性上升很快。這不僅是由傳輸中的電子控制造成的，而且與發(fā)動(dòng)機(jī)和其它部件在動(dòng)力傳動(dòng)系統(tǒng)中的協(xié)調(diào)性也有關(guān)系。例如，隨著自動(dòng)變速器中齒輪傳動(dòng)比數(shù)的增加，實(shí)現(xiàn)在任何行駛條件下平穩(wěn)轉(zhuǎn)換的校正變量的數(shù)量就會(huì)迅速上升。為了大大降低開(kāi)發(fā)時(shí)間，提高性能，在校正過(guò)程中，自動(dòng)化和系統(tǒng)化的方法是必需要的。首先，對(duì)自動(dòng)調(diào)節(jié)過(guò)程進(jìn)行研究使其在很少或沒(méi)有人為干擾的條件下能夠自動(dòng)校正變速器。研究人員開(kāi)發(fā)了一套自動(dòng)化的工具裝備用來(lái)校正在無(wú)人干涉條件下的汽車動(dòng)力總成 11。為了標(biāo)定 GDI 發(fā)動(dòng)機(jī)，研究人員開(kāi)發(fā)了 一種自適應(yīng)網(wǎng)絡(luò)設(shè)計(jì)實(shí)驗(yàn)（ DOE）方法 12。這種方法能為具有不規(guī)則形狀的操作區(qū)域的非線性系統(tǒng)進(jìn)行高效的實(shí)驗(yàn)設(shè)計(jì)。同樣的方法也可以應(yīng)用于汽車傳輸校準(zhǔn)。其次，人們提出了將控制模型視為一個(gè)推動(dòng)者的想法，目的在于減少校準(zhǔn)變量數(shù)，以及校準(zhǔn)的時(shí)間和精力。然而，環(huán)境的不確定性和操作范圍的廣泛是系統(tǒng)穩(wěn)定性方面的一個(gè)主要挑戰(zhàn)。傳輸溫度可以在 40 攝氏度到 150 攝氏度之間變化，這反過(guò)來(lái)又影響到自動(dòng)變速器流體的屬性。從車輛完全停下來(lái)到高速大負(fù)荷的運(yùn)轉(zhuǎn)，這種大范圍變化的操作需要精確的模型和高寬帶控制。參考文獻(xiàn) 13介紹了確定一套 線性模型的步驟和相關(guān)的自動(dòng)變速器液力變矩器的非建模動(dòng)力學(xué)，及應(yīng)用穩(wěn)勁的控制設(shè)計(jì)以達(dá)到預(yù)期的性能。詳細(xì)的對(duì)于控制轉(zhuǎn)換階段變速器模型慣性的開(kāi)發(fā)步驟呈現(xiàn)在文獻(xiàn) 14中?；谶@些模型，可以對(duì)穩(wěn)健的控制進(jìn)行設(shè)計(jì)，使其不用考慮發(fā)動(dòng)機(jī)負(fù)荷、自動(dòng)傳動(dòng)流體的粘度，以達(dá)到理想的轉(zhuǎn)向性能。為了實(shí)現(xiàn)自動(dòng)手動(dòng)變速器中離合器的控制，研究人員對(duì)變結(jié)構(gòu)控制（ VSC）進(jìn)行了研究 15。結(jié)果表明，變結(jié)構(gòu)控制能夠在未知的環(huán)境下保持系統(tǒng)的穩(wěn)定。第三，自適應(yīng)學(xué)習(xí)控制的開(kāi)發(fā)是為了滿足不確定的環(huán)境和不同的駕駛模式的要求。人工神經(jīng)網(wǎng)絡(luò)（ ANN）的使用 是用來(lái)模擬采用黑盒技術(shù)的汽車動(dòng)力總成 16。輸入和輸出數(shù)據(jù)是用來(lái)訓(xùn)練神經(jīng)網(wǎng)絡(luò)，使其能仿效變速器及它的子系統(tǒng)的功能。這種方法的特點(diǎn)是它不僅可以模擬穩(wěn)態(tài)運(yùn)作，還可以模擬動(dòng)態(tài) /瞬態(tài)系統(tǒng)的運(yùn)作。這種方法的主要優(yōu)點(diǎn)包括使用實(shí)時(shí)車輛數(shù)據(jù)的在線培訓(xùn)、自適應(yīng)校正或控制能力。 隨著變速器速比數(shù)的增加，換擋規(guī)律也變得更加復(fù)雜了。由于傳統(tǒng)的換擋規(guī)律只考慮到用汽車的速度和節(jié)氣門開(kāi)度來(lái)確定換擋位置，所以換擋復(fù)雜已經(jīng)成為在某些情況下，如丘陵地形條件，的關(guān)注焦點(diǎn)。例如，在蜿蜒上坡的道路上行駛時(shí)，駕駛員在進(jìn)入曲線行駛之前要釋放加速踏板來(lái) 降低車速，而傳統(tǒng)的換擋規(guī)律為了響應(yīng)油門的變化可能會(huì)換高速擋。但蜿蜒路段過(guò)后，司機(jī)需要踩加速踏板提高車速和執(zhí)行換低擋操作。同樣在下坡行駛時(shí)，一旦節(jié)氣門開(kāi)度減小，傳統(tǒng)的換擋系統(tǒng)會(huì)掛高擋，結(jié)果降低了發(fā)動(dòng)機(jī)制動(dòng)性能。由于一些因素，如道路等級(jí)、轉(zhuǎn)向角度、汽車加速等，既能滿足客戶要求，又有良好的燃油經(jīng)濟(jì)性的靈活的換擋系統(tǒng)必須得到開(kāi)發(fā)研究。采用模糊集和神經(jīng)網(wǎng)絡(luò)技術(shù)來(lái)避免換擋繁雜已經(jīng)在以往的文獻(xiàn) 17-18中得到了探討。大多數(shù)呈現(xiàn)在文獻(xiàn)中的自適應(yīng)換擋點(diǎn)算法需要搜集大量車輛的信息和車輛行駛的道路坡度。這些文獻(xiàn)很少提供可靠的 質(zhì)量估計(jì)算法。如果有大量適用的信息，那么道路等級(jí)的估計(jì)直截了當(dāng)。近來(lái)，汽車導(dǎo)航系統(tǒng)用于提供一些在換擋過(guò)程中關(guān)于道路形狀和條件的預(yù)覽信息 19。針對(duì)換擋系統(tǒng)的近期工作增加了模糊邏輯系統(tǒng)的反饋研究，實(shí)時(shí)更新隸屬函數(shù)以更好地滿足不同的駕駛模式。它們也拓展了一些功能，不僅僅包括 AT 也包括 AMT、 DCT 和CVT?？偨Y(jié)一般結(jié)構(gòu)換擋規(guī)律的框圖方法如圖 5 所示。 為了滿足對(duì)計(jì)算能力、遙感和驅(qū)動(dòng)能力不斷增加的需求，變速器控制硬件已經(jīng)發(fā)生了許多變化。這些變化包括三個(gè)方面的復(fù)雜性：遙感水平、驅(qū)動(dòng)水平和系統(tǒng)水平。在遙感水平方面，新 的遙感技術(shù)用于要么提高目前硬件的性能和效率，要么用于啟動(dòng)新的驅(qū)動(dòng)技術(shù)。壓力調(diào)節(jié)器和溫度傳感器在目前生產(chǎn)的變速器上比較適用。為了提高變速器的性能，壓力傳感器和扭矩傳感器是必不可少的。將這些傳感器引用到生產(chǎn)單元的主要挑 戰(zhàn)是生產(chǎn)成本和耐用性。圧阻式半導(dǎo)體壓力傳感器是汽車應(yīng)用水平的評(píng)價(jià)標(biāo)準(zhǔn)21。它 圖 5 齒輪移位調(diào)度算法 框圖 宣稱測(cè)量可達(dá)到 3.5 兆帕，在滿刻度的百分之一范圍左右。早期的扭矩傳感器的研究可以追溯到八十年代初期，那時(shí)研究人員 22為自動(dòng)變速器研究了一種非接觸式微型扭矩傳感器 。最近許多研究人員對(duì)磁扭矩傳感器進(jìn)行了研究 23-24。把材料應(yīng)力轉(zhuǎn)化成磁性能的變化的反磁現(xiàn)象用于測(cè)量傳輸?shù)呐ぞ?。為了克服變速器中的惡劣環(huán)境，特種涂料技術(shù)已經(jīng)得到開(kāi)發(fā)以保護(hù)傳感器部件。帶有扭矩傳感器的離合器盤被提議用在汽車上 25。安裝在離合器盤上的傳感器元件用于實(shí)現(xiàn)精確可靠的測(cè)量。在驅(qū)動(dòng)級(jí)中，電磁閥控制技術(shù)的研究在于改善液壓系統(tǒng)的可控性和靈活性。對(duì)于離合器驅(qū)動(dòng)而言，為了獲得更好的可控性，變分壓螺線管（ VBS）電磁閥現(xiàn)在普遍取代了脈沖寬度調(diào)制（ PWM）閥。然而， VBS 的閥門會(huì)因?yàn)闇囟茸兓霈F(xiàn)滯后和變化的 問(wèn)題。系統(tǒng)辨識(shí)理論 26用于對(duì)比例控制電磁閥進(jìn)行分析建模。報(bào)告的結(jié)論是該閥的帶寬受到螺線管電磁部分帶寬的限制。為了進(jìn)一步提高系統(tǒng)性能，快速、精確的氣門驅(qū)動(dòng)裝置是必不可少的。一種關(guān)于開(kāi)關(guān)閥 /執(zhí)行器旋轉(zhuǎn)的新概念建議處理在不到 5 毫秒的響應(yīng)時(shí)間里大于 10 行 /毫米的流量。這種概念的主要特點(diǎn)是這種閥有一個(gè)單級(jí)結(jié)構(gòu)，卻有兩級(jí)功能?？蛇x的離合器傳動(dòng)技術(shù)也被提倡去取代電動(dòng)液壓執(zhí)行器自動(dòng)變速器，以改善燃油經(jīng)濟(jì)性和性能。許多研究人員 28已經(jīng)對(duì)電動(dòng)驅(qū)動(dòng)離合器進(jìn)行了研究。這種機(jī)電執(zhí)行器的主要挑戰(zhàn)是車內(nèi)的低功率密度和合適的電力。 通常擴(kuò)大電機(jī)的轉(zhuǎn)矩能力需要某種齒輪傳動(dòng)。研究人員已經(jīng)開(kāi)發(fā)了一些用于離合器驅(qū)動(dòng)裝置的智能材料。在自動(dòng)變速器中使用電流（ ER）流體傳動(dòng)離合器的可行性已經(jīng)得到了證實(shí)，電流流體的理想性能的提出也是為了以后的研究 29。磁粉離合器作為一種啟動(dòng)離合器被用在 CVT上 30。文獻(xiàn) 31討論了磁流 MR液壓離合器的潛在用途。在系統(tǒng)級(jí)中，有一種將電子控制從乘客車廂轉(zhuǎn)移到傳動(dòng)箱，甚至整合齒輪箱內(nèi)部的電子控制以減少成本和提高性能和質(zhì)量 32-33。最近創(chuàng)造出了一種叫機(jī)電一體化傳輸?shù)男滦g(shù)語(yǔ)，用來(lái)解釋本身具有傳輸裝置的電子控 制的整合。除了成本和質(zhì)量效益之外，這一方法將使裝配線上傳輸裝置的測(cè)試和校準(zhǔn)成為可能。為啟用變速箱集成電子產(chǎn)品，新型的電子集成和封裝技術(shù)也得到了研究，以克服變速箱內(nèi)的惡劣環(huán)境 35。 3.結(jié)論 為了實(shí)現(xiàn)最大的燃油經(jīng)濟(jì)性并提高優(yōu)越的性能，在控制軟件 /算法和硬件方面的研究和開(kāi)發(fā)對(duì)于自動(dòng)變速器來(lái)說(shuō)都是必不可少的。隨著增強(qiáng)的功能和軟件、硬件日益增加的復(fù)雜性，系統(tǒng)整合是變速器成功發(fā)展的關(guān)鍵。 參考文獻(xiàn) 1 Wagner, G., “Application of Transmission Systems for Different Driveline Configurations in Passenger Cars”, SAE Technical Paper 2001-01-0882. 2 Hebbale, K.V. and Kao, C.-K., Adaptive Controlof Shifts in Automatic Transmissions, Proceedings of the 1995 ASME International Mechanical Eng ineering Congress and Exposition, San Francisco, CA, 1995. 3 Kao, C. K., Smith, A. L. and Usoro, P. B., “Fuel Economy and Performance Potential of a Five-Speed 4T60-E Starting Clutch Automatic Transmission Vehicle”, SAE Technical Paper 2003-01-0246. 4 Kluger, M. and Fussner, D., “An Overview of Current CVT Mechanisms, Forces and Efficiencies”, SAE Technical Paper 970688. 5 Raghavan, M. and Raghavan, S., Kinematic and dynamic analysis of the half-toroidal traction drive variator, Proceedings of the 2002 Global Powertrain Congress, Detroit, MI, September 24-27, 2002. 6 Tanaka, H. and Eguchi, M., “ Stability of a Speed Ratio Control Servo-Mechanism for a Half-Toroidal Traction Drive CVT,” JSME International Journal, Series C, Vol. 36, No. 1, 1993. 7 Hebbale, K.V., and Carpenter, M.E., Control of the Geared Neutral Point in a Traction Drive CVT, Proceedings of the 2003 American Control Conference, Denver, CO, 2003. 8 Tsai, L. W., Schultz, G., A Motor-Integrated Parallel Hybrid Transmission, Journal of Mechanical Design, Transactions of the ASME, Vol. 126, September 2004. 9 Ai, X., Mohr, T., and Anderson, S., An Electro-Mechanical Infinitely Variable Speed Transmission, SAE Technical Paper 2004-01-0354. 10Burns, L., McCormick, B., and Borroni-Bird, C., Vehicle of Change How fuel-cell cars could be the catalyst for a cleaner tomorrow, Scientific American, October 2002. 11Furry, S. and Kainz, J., “Rapid Algorithm Development Tools Applied to Engine Management Systems”, SAE Technical Paper 980799. 12Stuhler, H., Kruse, T., Stuber, A., Gschweitl, Piock, W., Pfluegl, H. and Lick, P., “Automated Model Based GDI Engine Calibration Adap