Hall effect sensors sense the direction of requested shift, and this input, together with a sensor in the gear box which senses the current speed and gear selected, feeds into a central processing unit. This unit then determines the optimal timing and torque required for a smooth clutch engagement, based on input from these two sensors as well as other factors, such as engine rotation, the Electronic Stability Control, air conditioner and dashboard instruments.
The central processing unit powers a hydro-mechanical unit to either engage or disengage the clutch, which is kept in close synchronization with the gear-shifting action the driver has started. The hydro-mechanical unit contains a servomotor coupled to a gear arrangement for a linear actuator, which uses brake fluid from the braking system to impel a hydraulic cylinder to move the main clutch actuator.
The power of the system lies in the fact that electronic equipment can react much faster and more precisely than a human, and takes advantage of the precision of electronic signals to allow a complete clutch operation without the intervention of the driver.
For the needs of parking, reversing and neutralizing the transmission, the driver must engage both paddles at once, after this has been accomplished the car will prompt for one of the three options.
The clutch is really only needed to start the car. For a quicker upshift, the engine power can be cut, and the collar disengaged until the engine drops to the correct speed for the next gear. For the teeth of the collar to slide into the teeth of the rings not only the speed, but also the position must match. This needs sensors to measure not only the speed, but the positions of the teeth, and the throttle may need to opened softer or harder. The even faster shifting techniques like powershifting require a heavier gearbox or clutch or even a twin-clutch gearbox.
According to the Car Crazy episode "Le Mans Museum of the Automobile", the paddle shifter interface could be found as early as in a 1912 Le Mans race car. The system used an inner steering wheel to select a gear level.
In Formula One, the first attempt at clutch-less gear changing was in the early 1970s, with the system being tested by the Lotus team. However, it would be a lot longer until the concept would be brought back to attention; in 1989, John Barnard and Harvey Postlethwaite, then-Ferrari engineers and designers, created a semi-automatic gearbox for use in the Ferrari 640 single-seater. Despite serious problems in testing, the car won its first race at the hands of Nigel Mansell. By 1994, the semi-automatic transmission was dominant in terms of gearbox technology, and the last F1 car fitted with a manual gearbox raced in 1995.
In 2008 the IndyCar Series adopted mandatory paddle shifters for the first time.
In normal driving, the clutch was not used. The transmission itself was a fully synchronised manual type, with four forward gears, one reverse, where the shifting was done 'automatically' by either vacuum cylinders (early, M4, Vacamatic), or hydraulic cylinders (late, M6, Presto-Matic).
Earlier, and by many manufacturers, an arrangement to disengage the clutch during coasting was tried to ease shifting. Called "freewheeling", it was bedeviled by the absence of adequate brakes.
In the UK though, semi-automatic transmission has been very popular on buses for some time, from the 1950s right through to the 1980s, an example being the well known London Routemaster, although the latter could also be driven as a fully automatic in the 3 highest gears. Most heavy-duty bus manufacturers offered this option, using a gearbox from Self-Change Gears Ltd of Coventry, and on urban single- and double-deck buses it was the norm by the 1970s. This coincided with the development of city buses with engines and transmissions at the rear rather than the front, which was beyond the capability of a manual gearchange/clutch linkage from the driver's position. Leyland manufactured many buses with semi-automatic transmission, including its Leopard and Tiger coaches. Fully automatic transmission became popular with increasing numbers of continental buses being bought in the UK, and more and more British manufacturers began offering automatic options, mostly using imported gearboxes, and semi-automatic transmission lost favour. These days, very few buses with semi-automatic transmission remain in service, although many are still on the roads with private owners. Modern types of semi-automatic transmission though is becoming more common, mostly replacing manual gearboxes in coaches and small buses.
The Self-Change Gears semi-automatic gearbox was also fitted to the several thousand diesel railcars built for the British railway system in the late 1950s-early 1960s, which lasted in service until the 1990s-2000s. Their whole engine-transmission system was based on that from the main bus manufacturers of the period such as Leyland and AEC. Gear selection was by the train driver with a hand-held lever as the train accelerated. Such trains were formed of a number of such railcars coupled together and each power car had two engine/semi-automatic gearbox units mounted under the floor. Synchronising controls by control cables connected through the train ensured all the gearboxes under all coaches of the train changed gear together.
Patent Issued for Method for Operating an Automatic or Semi-Automatic Transmission of a Heavy Vehicle When in Idle-Driving Mode
Sep 12, 2012; From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Lauri, Erik (Molndal, SE); Karpenman,...
WIPO ASSIGNS PATENT TO PEUGEOT CITROEN AUTOMOBILES FOR "METHOD FOR SHIFTING GEARS IN A SEMI-AUTOMATIC TRANSMISSION" (FRENCH INVENTORS)
Apr 28, 2011; GENEVA, April 28 -- Publication No. WO/2011/045545 was published on April 21. Title of the invention: "METHOD FOR SHIFTING GEARS...