Torque Vectoring Technology

Torque vectoring is the next step in AWD, its contribution being that it can get power to any wheel nearly instantly without having to use the brakes or cut power. Most current AWD control wheelspin by braking a spinning wheel or cutting the power from the engine. Torque vectoring is achieved by using redesigned differentials that can distribute power to the wheel or wheels that have traction. That means that wheels don't need to be stopped, and even better, you won't suffer from a sudden loss of power as you're negotiating an unexpected loss in traction. Some systems in use now or being developed work on FWD, RWD, and AWD cars, and can get power to any wheel or combination of wheels.

Lateral Torque Vectoring Control

IMG Ref: http://torque-vectoring.belisso.com/

The lateral torque vectoring control transfers the torque from the left wheel to the right wheel, and vice versa, to generate an amount of braking torque on one wheel while generating the same amount of driving torque on the other wheel. The control of this type, therefore, can generate the yaw moment at any time regardless of the engine torque. Another advantage is that it does not affect the total driving and braking forces acting on the vehicle: no conflict with acceleration and deceleration operations. Although this control affects the steering reaction force when applied to the front wheels, it does not produce any adverse effects when applied to the rear wheels.

Torque transfer is up to 100%.

Reference:
http://torque-vectoring.belisso.com/

Regenerative Braking

In Traditional braking systems, brake pads produce friction with the brake rotors to slow or stop the vehicle. Additional friction is produced between the slowed wheels and the surface of the road. This friction is what turns the car's kinetic energy into heat.

With regenerative brakes, on the other hand, the system that drives the vehicle does the majority of the braking. When the driver steps on the brake pedal of an electric or hybrid vehicle, these types of brakes put the vehicle's electric motor into reverse mode, causing it to run backwards, thus slowing the car's wheels. While running backwards, the motor also acts as an electric generator, producing electricity that's then fed into the vehicle's batteries.

The regenerative braking effect drops off at lower speeds; therefore the friction brake is still required in order to bring the vehicle to a complete halt. Physical locking of the rotor is also required to prevent vehicles from rolling down hills. The friction brake is a necessary back-up in the event of failure of the regenerative brake.

The GM EV-1 was the first commercial car to do this. Engineers Abraham Farag and Loren Majersik were issued two patents for this brake-by-wire technology.

IMG Ref: http://auto.howstuffworks.com/auto-parts/

Reference:

http://en.wikipedia.org/wiki/Regenerative_brake
http://auto.howstuffworks.com/auto-parts
GM patent 5775467 – Floating electromagnetic brake system.
GM patent 5603217 – Compliant master cylinder.

MPFI (Multi Point Fuel Injection)

MPFI Petrol Injectors with the fuel lines
IMG Ref: http://dieselpumpservice.com/services

MPFI means Multi Point Fuel Injection system. In this system each cylinder has number of injectors to supply/spray fuel in the cylinders as compared to one injector located centrally to supply/spray fuel in case of single point injection system. MPFI system injects fuel into individual cylinders after receiving command from the on board engine management system computer or Engine Control Unit (ECU).

Advantage of M. P. F. I.

1. More uniform A/F mixture will be supplied to each cylinder, hence the difference in power developed in each cylinder is minimum. Vibration from the engine equipped with this system is less, due to this the life of engine components is improved.
2. No need to crank the engine twice or thrice in case of cold starting as happens in the carburetor system.
3. Immediate response, in case of sudden acceleration / deceleration.
4. Since the engine is controlled by ECM* (Engine Control Module), more accurate amount of A/F mixture will be supplied and as a result complete combustion will take place. This leads to effective utilization of fuel supplied and hence low emission level.
5. The mileage of the vehicle will be improved.
   

ECM (Engine Control Module) and its function

The function of ECM is to receive signal from various sensors, manipulate the signals and send control signals to the actuators. Sensors; Sensing different parameters (Temperature, Pressure, Engine Speed etc.) of the engine and send signal to ECM. Actuators; Receives control signal from ECM and does function accordingly (ISCA, PCSV, Injectors, Power Transistor etc.)

Reference:

http://www.automobileindia.com/consumer-guide/automobile-technology.html

Dual Clutch/Direct Shift Gearbox (DSG)

Dual Clutch Transmission (DCT) was invented by Frenchman Adolphe Kégresse just prior to World War II, but he never developed a working model. The first actual DCTs arrived from Porsche in-house development, for Porsche racing cars in the 1980s. The first series production road car to be fitted with a DCT was the Direct-Shift Gearbox (DSG) in the 2003 Volkswagen Golf Mk4 R32.

Sectional view of the Volkswagen Group dual clutch Direct-Shift Gearbox (DSG) transmission
IMG Ref: http://en.wikipedia.org/wiki/File:VW_DSG_transmission_DTMB.jpg

The revolutionary direct shift gearbox (DSG) combines the advantages of a conventional six-speed manual-shift gearbox with the qualities possessed by a modern automatic transmission. The driver enjoys immense agility and driving pleasure with, at the same time, smooth, dynamic acceleration with no interruption to the power flow.

The technical basis of the direct shift gearbox (DSG) is a double clutch. This consists of two wet plate-type clutches with hydraulically regulated contact pressure. One of the two clutches engages the odd-numbered, the other the even-numbered gears. This principle enables gear shifts to be made without interrupting the power flow and keeps the shift times extremely short. While the first clutch is transmitting the power, the second clutch is ready to engage the next gear, which is preselected. When the driver makes the gear shift, the first clutch is released and the second engages, so that the gear shift takes place in a fraction of a second.

A dual clutch transmission eliminates the torque converter as used in conventional epicyclic-geared automatic transmissions. Instead, dual clutch transmissions that are currently on the market primarily use two oil-bathed wet multi-plate clutches, similar to the clutches used in most motorcycles, though dry clutch versions are also available.

Clutch Types

There are TWO fundamental types of clutches utilised in dual clutch transmissions: either two wet multi-plate clutches which are bathed in oil (for cooling), or two dry single-plate clutches. The wet clutch design is generally used for higher torque engines which can generate 350 newton metres (258 ft·lbf) and more (the wet multi-plate clutch DCT in the Bugatti Veyron is designed to cope with 1,250 N·m (922 ft·lbf)), whereas the dry clutch design is generally suitable for smaller vehicles with lower torque outputs up to 250 N·m (184 ft·lbf). However, whilst the dry clutch variants may be limited in torque compared to their wet clutch counterparts, the dry clutch variants offer an increase in fuel efficiency, due to the lack of pumping losses of the transmission fluid in the clutch housing.

Clutch Installation

There are now three variations of clutch installation. The original design used a concentric arrangement, where both clutches shared the same plane when viewed perpendicularly from the transmission input shaft, along the same centre line as the engine crankshaft; when viewed head-on along the length of the input shaft, this makes one clutch noticeably larger than the other.

The second implementation utilized two single-plate dry clutches which are side-by-side from the perpendicular view, but again sharing the centre line of the crankshaft.

A latest variation uses two separate but identical sized clutches; these are arranged side-by-side when viewed head-on (along the length of the input shaft and crankshaft centre line), and also share the same plane when viewed perpendicularly. This latter clutch arrangement (unlike the other two variations) is driven via a gear from the engine crankshaft.

***

The driver can operate the DSG manually or allow changes to take place automatically. In the automatic mode there is a choice between the well-balanced, comfortable standard shift settings and a program with greater sports emphasis. Manual shifts are made either at the gear lever or at shift paddles behind the steering wheel.

Reference:
http://en.wikipedia.org
Audi Glossary

Adaptive Air Suspension

Adaptive air suspension is an electronically controlled air suspension system at all four wheels with a continuously adaptive damping system. It unites sporty handling and a high level of ride comfort. In addition, the air suspension allows the speed-dependent lowering of the body – this change in ride height means a low centre of gravity and significantly increased directional stability as a result. The vehicle’s aerodynamics are improved at the same time.

The vehicle has air suspension struts on all four wheels. The data from sensors on the axles and acceleration sensors on the body is evaluated in the adaptive air suspension's central control unit. This computer controls the adjustment of the individual shock absorbers in milliseconds depending on driving situation. Provided no higher damping forces are required – for instance when driving straight ahead on good roads – the damper settings remain comfortably soft.

Controlled changes to the damping force at individual wheels help to eliminate body movements at any time which could reduce occupant comfort. The adaptive damping system automatically reduces rolling or pitching movements when cornering, braking or driving off. Adaptive air suspension moreover offers the advantages of a traditional self-levelling suspension system. The vehicle's suspension height remains constant irrespective of the load it is carrying.

The adaptive air suspension generally also allows the driver to influence the suspension characteristic – and thus the operating dynamics – as individually preferred. The damping characteristics and ride height can be adjusted in a single process via the MMI "CAR" menu system. Adaptive air suspension (sport), which is available as an option in the Audi A8, is the first Audi sports suspension system to be based on the principle of air suspension.

Adaptive Air Suspension Basic Principle

Adaptive air suspension operation

IMG Ref: http://moodle.student.cnwl.ac.uk/

When the ignition is switched on, or when the vehicle’s door is opened before ignition, the control system is activated. The height sensor uses the induction principle to constantly monitor the distance between the vehicle’s axle and its chassis.

When the vehicle is being loaded, unloaded, or lowered due to driver command or vehicle speed, the electronic readings from the height sensor monitor the change. This is picked up by the electronic control unit and compared to the stored reference values.

The ECU either activates the electric motor of the compressor, or the exhaust solenoid valve. This also requires the solenoid valve block to be actuated, in order to maintain the required level. The corner solenoid valves are subject to stringent leakage requirements to maintain the vehicle’s height even without system operation.

When the vehicle is being loaded, the compressor delivers air into the four air suspension bellows, until the normal level has once again been reached. For additional air delivery or rapid response, the reservoir solenoid valve is opened and air flows directly from the reservoir.

When the vehicle is being unloaded, the solenoid valve block is activated. This results in airflow from the air suspension bellows being removed via the air dryer solenoid valve in the compressor, then via the relay valve. The air is then exhausted into the atmosphere.

Reference:
http://moodle.student.cnwl.ac.uk/
Audi Glossary

Locking Differential

A locked differential forces both left and right wheels on the same axle to rotate at the same speed under nearly all circumstances, without regard to tractional differences seen at either wheel. Therefore, each wheel can apply as much rotational force as the traction under it will allow, and the torques on each side-shaft will be unequal. (Unequal torque, equal rotational speeds).

Locking Differential
Image courtesy Eaton Automotive Group's Torque Control Products Division

A locked differential can provide a significant traction advantage over an open differential, but only when the traction under each wheel differs significantly.

All the above apply to central differentials as well as to those in each axle: full-time four-wheel-drive vehicles have three differentials, one in each axle, and a central one between the front and rear axles.

There are two main types of lockers: automatic and selectable.

Automatic lockers lock and unlock automatically with no direct input from the driver. Some automatic locking differential designs ensure that engine power is always transmitted to both wheels, regardless of traction conditions, and will "unlock" only when one wheel is required to spin faster than the other during cornering.

• Pros: Automatic action, no driver interaction necessary, no stopping for (dis-) engagement necessary
• Cons: Intensified tire wear, noticeable impact on driving behaviour (most people often tend to understeer)
  

A "selectable" locker allows the driver to lock and unlock the differential at will from the driver's seat. This can be accomplished via compressed air (pneumatics) like ARB's "Air Locker" or vacuum, electronic solenoids (electromagnetics) like Eaton's "ELocker" and Nissan Corporations electric locker found as optional equipment on the Frontier (Navarra) & Xterra, or some type of cable operated mechanism as is employed on the "Ox Locker."

• Pros: Allows the differential to perform as an "open" differential for improved driveability, maneuverability, provides full locking capability when it is desirable or needed
• Cons: Mechanically complex with more parts to fail. Some lockers require vehicle to stop for engagement. Needs human interaction and forward-thinking regarding upcoming terrain. Un-skilled drivers often put massive stress on driveline components when leaving the differential in locked operation on terrain not requiring a locker.

HUMMER H3 Electronic Locking Rear Differential
IMG Ref: http://www.2405.com/press-library/Hummer-H3-2006/HUMMER-H3-Electronic-Locking-Rear-Differential.asp

GMC_09 Canyon automatic locking differential
IMG Ref: http://www.gmc.com/canyon/canyon/index.jsp

Applications

• Race cars often use locking differentials in order to maintain traction during high speed maneuvers or when accelerating at extreme rates.
• Some utility vehicles such as tow trucks, forklifts, tractors, and heavy equipment use locking differentials to maintain traction, especially when driving on soft, muddy, or uneven surfaces.
• Lockers are common in agricultural equipment and military trucks.
• Locking differentials are considered essential equipment for serious off-road driving Four-wheel drive vehicles.
• Differential locks are also used on some non-utility four-wheel-drive vehicles to compensate for a relative lack of axle articulation (vertical wheel movement).
• Used in the sport of drifting as an alternative to a limited slip differential.

Reference:
http://en.wikipedia.org

Electronic Differential Lock (EDL)

Limited slip differentials are considered a compromise between a standard differential and a locking differential because they operate more smoothly, and they do direct some extra torque to the wheel with the most traction compared to a standard differential, but they are not capable of 100% lockup.

Traction control systems are also used in many modern vehicles either in addition or as a replacement of locking differentials. One example is that offered by Volkswagen under the name of electronic differential lock (EDL).

This Electronic Differential Lock is a limited slip differential imitation which is an electronic system that detects wheel spin via ABS sensors and applies brakes to spinning wheels. This results in the torque being transferred via open differentials to another wheel that has more traction.

For example, the system brakes the wheel that is raised in the air and spinning freely, and engine power goes to another wheel that is on the ground.

Reference:
www.awdwiki.com