Electronic Transmission Control by Frank Owen (last revised 2 August 2008) Introduction
Figure 2 - Today’s mechatronic gearshift
Download 0.82 Mb.
|
- Navigate this page:
- Figure 3 – Smart car
- Different Types of Transmissions
| Figure 2 - Today’s mechatronic gearshift
Note also that this device is manufactured not by BMW, Audi, Mercedes, but rather by a third-party manufacturer. These third party developers and manufactures work very closely with the large auto manufacturers to produce almost everything in the car except the body and the engine. Additionally this company, Kostal, produces a steering column module, a roof module, a network control unit, a door control unit, a seat control unit, and control panels and switches. Note that more than one manufacturer may use Kostal products in their cars. Example My wife recently purchased a Smart Passion. This is a little two-seat, economical car, popular in Europe and now being imported into the U.S. (see Figure 3). The car has an automated manual transmission. It has a manual stickshift but no clutch. It has two shifting modes—manual and automatic. In manual mode, the driver decides when to shift and inputs this wish by deflecting the gearshift lever forward (up-shift) or backward (downshift). In automatic mode, the driver puts the transmission into “D” and simply drives, as if the transmission were an automatic, instead of an automated manual transmission. 
Figure 3 – Smart car At first the shifting was a little hard to get used to. Actually the transmission control did a pretty good job of shifting into the next gear. But, being used to an automatic transmission, the shifting seemed slow. But when the driver thought of what it would be like to operate the shifting manually, the sluggish shifting actually wasn’t sluggish but was comparable with how the shifting would be if done manually. So at first both my wife and I used the manual shifting, because of the perceived clumsiness and slowness of the automated shifting. After further reading of the owner’s manual, however, my wife saw that the automated shifting was optimized for economy. So she switched to “D” and got used to the automated shifting. One other problem we had was that in “D”, when the car was shifting, we each naturally let off on the gas pedal. She read further and informed me that we are not supposed to do that. This can be confusing to the micro-controller. It could be interpreted as a desire to stop accelerating. So the proper procedure is simply to express the desire to accelerate as a steady position of the accelerator pedal (i.e. don’t let off on the pedal while the car is shifting). With these adaptations, we are becoming acclimated to an automated car. Different Types of Transmissions Manual transmissions are still very common in Europe. Today they have five, now often six, and sometimes even seven forward gears. Manual transmissions have the highest drive efficiency because the engine is mechanically linked to the drive wheels. There is no inefficiency due to the hydraulic link in a hydraulic automatic transmission. Manual transmissions are not as comfortable to the passengers in the car. Ride comfort is a weakness. The automated manual transmission (AMT), manual transmissions under the control of a microprocessor have been introduced in the last few years into such cars as the Opel Corsa, the Ford Fiesta, and the Smart. They are also used in some sporty models such as the BMW M3 & M5 and the Ferrari. The automatic control of the manual transmission compensates somewhat for ride comfort. The controller also prevents shifting mistakes. In stop and go traffic, with automatic control the transmission will be in the correct gear more often than it would be under manual control. Thus the automatic control also leads to better fuel efficiency and thus reduced emissions output. Large trucks often have 12 to 16 gears. It is very complicated to shift these trucks manually. So automated shifting has been applied in such vehicles for some time now. At first the AMT was built as an add-on. A normal manual transmission was simply fitted with actuators to actuate the clutch and the gear shift. Since then manual transmissions have been redesigned with integral actuators. This led to room and weight savings. Automatic transmissions are oil driven. Early on, however, these transmission were outfitted with governing electronics. For example electrical components were employed to manage the bypass clutch, a device that locks the transmission mechanically once the car has reached highway speeds. Thus for long-distance trips at highway speeds, the internal hydraulic losses of the transmission are avoided. The double clutch transmission is a relatively new development (see Figure 4). This transmission was developed by Volkswagen in 2003. It has a single input shaft and two output shafts. The output shafts have respectively gears 1, 3, and 5 and gears 2, 4, and 6. This enables the load to be transferred from one output shaft to the other gradually. Thus the gears may be shifted without removing the load. So, for example, in shifting from first into second gear, the load is gradually removed from first gear while it is being gradually applied to the second gear. 
Directory: ~fowen -> AutoMech AutoMech -> Gasoline (Otto) Engine Control Hochschule München International Summer School Download 0.82 Mb. Share with your friends:
|