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science projects buddy
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Joined: Dec 2010
07-01-2011, 09:44 PM

Introduction to ATC
An automatic transmission system used in automobiles which adapts to:
The Difference
Electronically Controlled Automatic Transmission
Adaptive Transmission Control
Recognition Elements
Driver-Type Recognition
Environmental Recognition
Driving-Situation Recognition

Driver-Type Recognition
Tracks how the driver has been “behaving” over the past few seconds
Environmental Recognition
Detects any increase in driving resistance like climbing or descending a mountain or decrease in traction
Driving-Situation Recognition
Monitors the throttle openings, road speeds and “g” level

Principal Components
Microprocessor and CAN
Torque Converter
Planetary Gear set
Hydraulic System
WSS (Wheel Speed Sensor)
CTS (Coolant Temperature Sensor)
TPS (Throttle Position Sensor)
Gravity Sensor
Microprocessor and CAN
Controller Area Network

High speed data bus

1 million bits/second

Analog to Digital Converter

Torque Converter
Is a type of fluid coupling

Allows the engine to spin somewhat independently of the transmission

Situated between the engine and the transmission

Compound Planetary Gearsets

Attached Files
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07-01-2011, 09:47 PM

The Adaptive Transmission Control is an automatic transmission system used in automobiles, which recognizes individual styles of driving (e.g., aggressive vs. relaxed) and driving conditions and adapts transmission shift parameters accordingly. It combines maximum safety with the kind of brilliant technical concept that adds even more pleasure to driving an automatic transmission.

.doc   Adaptive Transmission Control.doc (Size: 609 KB / Downloads: 83)

Instead of the driver selecting one or the other shift mode via a console switch, ATC employs a new electronic logic that recognizes the driver's present driving style, certain environmental conditions (such as hills or reduced traction) and driving conditions (such as vigorous cornering or stop-and-go traffic), and selects the optimum shift mode and gear(s) for that set of circumstances.

A true adaptive system, it registers accelerator position and speed of movement before selecting one of the shift programs, from ultra-economical to super-sporting. The electronics also monitor wheel spin at the driven wheels and the amount of engine torque reaching them, and decide whether road conditions qualify as "normal", "winter" or "hill-climbing/starting". In this way, transmission shifts are adapted to suit even the most extreme driving conditions, for example to ensure greater traction and directional stability on slippery surfaces and to avoid too-frequent shifts when cornering.

The driver also has the opportunity to select the basic M (Manual) or A (adaptive) settings.


Conventional automatic transmissions have been limited in their ability to meet the varying performance expectations of all drivers of a particular vehicle type. This factor has driven automobile manufacturers to identify solutions that allow drivers the freedom to select a performance style using shifters, buttons or rockers to choose gears themselves.

Electronically controlled automatic transmissions have offered the driver several choices of "shift modes," or programs for some years now. Typically, an Economy mode, aimed at everyday driving and always engaged when the driver put the selector lever in "D," provides upshifts at relatively low vehicle speeds with an eye to best fuel economy, quietness and smoothness. A Sport mode causes upshifts and downshifts to occur at higher engine speeds, enhancing response. There has also been either a Manual mode to give the driver full control over shifts, or a Winter mode to help reduce wheelspin when starting up on snow or ice. ATC goes two fascinating steps further by:

Increasing the number of modes from three to nine.
Making the mode selections automatically.

The technological basis for the adaptive transmission is a system of fuzzy rules. A rule is "fuzzy" when it can distinguish not only between "true" and "false", but also between "mostly true" and "mostly false". The task of fuzzy rules is to translate physical sensor input data into subjective variables like "sporty driving". A driver won't necessarily be classified as "sporty" or "comfort oriented," but could fall somewhere between the two extremes because of a relatively sporty driving style. Though the process might sound simple, its execution requires considerable effort when implemented in software equations that specify the minimum and maximum value for each influencing variable as well as the relation between the two. The result of these calculations is an adaptive transmission control system that produces greater comfort and driving satisfaction, while achieving lower fuel consumption.

ATC employs highly sophisticated electronic logic to recognize what is going on with the driver, the environment and traffic, and does a remarkable job of making the transmission respond ideally in view of all that. It improves driver choice, in that it relieves the driver of having to think about selecting a mode and frees him or her to concentrate on traffic and the road. At the same time, ATC eliminates some minor operational drawbacks that have been present in automatic transmissions mainly to the irritation of particularly skilled or sensitive drivers.

To accomplish these remarkable results, ATC employs the following "recognition" elements, and controls the transmission accordingly:

 Driver-Type Recognition
 Environmental Recognition
 Driving-Situation Recognition.

Driver Type Recognition

Utilizing the remarkable capabilities of microprocessors, this logic is able to track how the driver has been "behaving" over the past few seconds. If, for example, the driver has been stepping hard on the accelerator, the logic concludes that he or she is in a sporty mood, and selects and holds either of the two available Sport modes. This causes upshifts and downshifts to take place at higher engine speeds, and one of these modes will be held for a period of time (generally 5-10 seconds) after the system has made its decision.

Likewise, quick accelerator-pedal movements cause selection of one of the Sport modes. If there are no abrupt accelerator movements for a certain length of time, one of two economy-oriented shift modes is selected; upshifts and downshifts take place at lower engine speeds and fuel economy is optimized.

In another recognition of accelerator-pedal movements, whenever the driver releases the accelerator quickly and the transmission is in a lower gear (say 1st through 4th), ATC will not allow an upshift. Thus the engine braking of the lower gear remains in effect -- surely a bonus in this situation, when the driver wants to slow down anyway -- and (as smoothly as this transmission shifts) the lack of an unwanted shift is bound to be a subtle plus as well.

Environmental Recognition

The logic detects any increase in driving resistance, such as when the car is carrying an above-average load or is climbing or descending a grade; or a decrease in traction, such as on ice or snow. In the former case, it selects one of two available Mountain modes and prevents unwanted upshifts, or even causes a downshift if the driver applies the brakes on a downhill run. In the latter, it selects a Winter mode; moving off from rest, for example, the transmission will select a higher gear rather than 1st.

Driving-Situation Recognition

In stop-and-go traffic, the logic detects that throttle openings and road speeds have remained below certain limits for a period of time. The transmission then rules out 1st gear, reducing unwanted "shift activity" that can make this bothersome kind of driving even more so. This is referred to as a Stop-and-Go mode. For driving

on a winding road, the logic detects when the car is cornering above a certain "g" level; if the driver releases the accelerator and the transmission is in a lower gear, that gear will be held, eliminating unwanted or awkward downshifts under this circumstance.

ATC responds to driver interaction by analyzing all available sensor data evaluated several seconds before and after the driver's action. If the calculation indicates that the driver prefers to up shift later on the characteristic curve, for example, when crossing a mountain pass, the fuzzy equations are modified accordingly. Shifting procedures that fall outside extreme values, which could result in mechanical damage of the motor and transmission, are not carried out.


Microprocessor and CAN
Torque Converter
Planetary Gear set
Hydraulic System


The "A" position denotes Adaptive, with operation as described. In the "M" mode, the driver can select any gear from 1st through 4th manually via the shift lever. So this particular driver choice, which seems the only one ATC might not be able to make effectively, remains to give the driver pure manual operation when desired. “P” denotes parking and “R” denotes reverse.


speed sensor

Various sensors are used to obtain various input parameters like position of the accelerator pedal actuated by the driver of the vehicle, vehicle straight-line speed (that is, the speed in the forward direction of movement),”g” level, coolant temperature, transmission output rpm or engine rpm etc. For example, the clutch is supposed to disengage whenever the car is accelerating or decelerating at a particular rate, and the computer gets this info from the Throttle Position Sensor.

WSS (Wheel Speed Sensor)
CTS (Coolant Temperature Sensor)
TPS (Throttle Position Sensor)
Gravity Sensor

Microprocessor and CAN

This unit is the brain of ATC. The microprocessor does all the calculations and Controller Area Network transfers the data.

As in other automatics, shifts are smoothed by automatic engine ignition retard during shifts; this engine-transmission interaction is controlled by Controller Area Network, a high-speed data bus that utilizes multiplex technology to transfer up to 1 million bits of data per second.
There is an analog-to-digital converter which converts analog voltage into a 10 bit digital number. This is necessary because the processor only understands digital numbers; 0?s and 1?s, like normal computer.
In top gear, a smoother-acting torque-converter lockup clutch helps improve fuel efficiency. The best time to lock up the clutch is determined by the processor on the basis of data it receives from various sensors and switches.

Torque Converter

The torque converter is situated between the engine
and the transmission.
A torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. If the engine is turning slowly, such as when the car is idling at a stoplight, the amount of torque passed through the torque converter is very small, so keeping the car still requires only a light pressure on the brake pedal.
If the accelerator pedal is pressed while the car is stopped, we should press harder on the brake to keep the car from moving. This is because when you step on the gas, the engine speeds up and pumps more fluid into the torque converter, causing more torque to be transmitted to the wheels. The main advantage of a torque converter is its damping characteristic, which enables engine torque pulsations to be attenuated before being transmitted to the driveline. A torque converter also offers the ability to amplify the driving force when needed, namely, at low speeds.
Four components inside the very strong housing of the torque converter are:
• Pump
• Turbine
• Stator
• Transmission fluid

The parts of a torque converter (left to right): turbine, stator, pump

The housing of the torque converter is bolted to the flywheel of the engine, so it turns at whatever speed the engine is running at. The fins that make up the pump of the torque converter are attached to the housing, so they also turn at the same speed as the engine. The cutaway below shows how everything is connected inside the torque converter.

How the parts of the torque converter connect to the transmission and engine
The pump inside a torque converter is a type of centrifugal pump. As it spins, fluid is flung to the outside, much as the spin cycle of a washing machine flings water and clothes to the outside of the wash tub. As fluid is flung to the outside, a vacuum is created that draws more fluid in at the center.

The pump section of the torque converter
The fluid then enters the blades of the turbine, which is connected to the transmission. The turbine causes the transmission to spin, which basically moves the car. The blades of the turbine are curved. This means that the fluid, which enters the turbine from the outside, has to change direction before it exits the center of the turbine. It is this directional change that causes the turbine to spin.

The torque converter turbine
In order to change the direction of a moving object, you must apply a force to that object -- it doesn't matter if the object is a car or a drop of fluid. And whatever applies the force that causes the object to turn must also feel that force, but in the opposite direction. So as the turbine causes the fluid to change direction, the fluid causes the turbine to spin.
The fluid exits the turbine at the center, moving in a different direction than when it entered. If you look at the arrows in the figure above, you can see that the fluid exits the turbine moving opposite the direction that the pump (and engine) are turning. If the fluid were allowed to hit the pump, it would slow the engine down, wasting power. This is why a torque converter has a stator.
The stator resides in the very center of the torque converter. Its job is to redirect the fluid returning from the turbine before it hits the pump again. This dramatically increases the efficiency of the torque converter.
Torque Converter Lockup Clutch: When the two halves of the torque converter get up to speed, this clutch locks them together, eliminating the slippage and improving efficiency. The microprocessor determines the best time to lock up the clutch on the basis of data it receives from various sensors and switches.
Compound Planetary Gearsets
The transmission uses a set of gears, called a compound planetary gearset, that looks like a single planetary gearset but actually behaves like two planetary gearsets combined. It has one ring gear that is always the output of the transmission, but it has two sun gears and two sets of planets.

Left to right: the ring gear, planet carrier, and two sun gears
The figure below shows the planets in the planet carrier. The planet on the right sits lower than the planet on the left. The planet on the right does not engage the ring gear -- it engages the other planet. Only the planet on the left engages the ring gear. The shorter gears are engaged only by the smaller sun gear. The longer planets are engaged by the bigger sun gear and by the smaller planets.

Planet carrier

First Gear

In first gear, the smaller sun gear is driven clockwise by the turbine in the torque converter. The planet carrier tries to spin counterclockwise, but is held still by the one-way clutch (which only allows rotation in the clockwise direction). The first set of planets engages the second set, and the second set turns the ring gear. This would also cause the bigger sun gear to spin; but because that clutch is released, the bigger sun gear is free to spin in the opposite direction of the turbine (counterclockwise). The gear ratio is 2.4:1.

Second Gear

The gear ratio for the second gear can be analyzed as two stages. The first stage uses the larger sun gear as the ring gear. So the first stage consists of the sun (the smaller sun gear), the planet carrier, and the ring (the larger sun gear). The input is the small sun gear; the ring gear (large sun gear) is held stationary by the band, and the output is the planet carrier. For this stage, with the sun as input, planet carrier as output, and the ring gear fixed, the gear ratio is 2.2:1.
The planet carrier turns 2.2 times for each rotation of the small sun gear. At the second stage, the planet carrier acts as the input for the second planetary gear set, the larger sun gear (which is held stationary) acts as the sun, and the ring gear acts as the output, so the gear ratio is 0.67:1.
To get the overall reduction for second gear, multiply the first stage by the second, 2.2 x 0.67, to get a 1.47:1 reduction.

Third Gear

Most automatic transmissions have a 1:1 ratio in third gear. To get a 1:1 output, we have to lock together any two of the three parts of the planetary gear. With the arrangement in this gearset it is even easier -- all we have to do is engage the clutches that lock each of the sun gears to the turbine.
If both sun gears turn in the same direction, the planet gears lockup because they can only spin in opposite directions. This locks the ring gear to the planets and causes everything to spin as a unit, producing a 1:1 ratio.


An overdrive has a faster output speed than input speed. It's a speed increase -- the opposite of a reduction. In order to improve efficiency, the transmission has a mechanism that locks up the torque converter so that the output of the engine goes straight to the transmission.

In this transmission, when overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. The small sun gear freewheels, and the larger sun gear is held by the overdrive band. Nothing is connected to the turbine; the only input comes from the converter housing. With the planet carrier for input, the sun gear fixed and the ring gear for output, the gear ratio is 0.67:1.
So the output spins once for every two-thirds of a rotation of the engine. If the engine is turning at 2000 rotations per minute (RPM), the output speed is 3000 RPM. This allows cars to drive at freeway speed while the engine speed stays nice and slow.


Reverse is very similar to first gear, except that instead of the small sun gear being driven by the torque converter turbine, the bigger sun gear is driven, and the small one freewheels in the opposite direction. The planet carrier is held by the reverse band to the housing. So the gear ratio is -2.0:1.
So the ratio in reverse is a little less than first gear in this transmission.


The parking-brake mechanism engages the square notches on the outer surface of the ring gear to hold the car still. This is the output of the -- so if this part can't spin, the car can't move.

Gear Ratios

This transmission has four forward gears and one reverse gear. Let's summarize the gear ratios, inputs and outputs:

Gear Input Output Fixed Gear Ratio
1st 30-tooth sun 72-tooth ring Planet carrier 2.4:1
2nd 30-tooth sun 72-tooth ring 36-tooth sun 1.47:1
3rd 30- and 36-tooth suns 72-tooth ring 1.0:1
OD Planet carrier 72-tooth ring 36-tooth sun 0.67:1
Reverse 36-tooth sun 72-tooth ring Planet carrier -2.0:1

Hydraulic System

The hydraulic system plays a major role in the operation of ATC. The function of the hydraulic system is to cooperate with the electronic controls to make the transmission fully automatic. In particular, one of its main functions is to generate the pressurized fluid and maintain/vary the fluid pressure to perform needed tasks satisfactorily under various operating conditions. It initiates the gear shifting process by increasing and decreasing fluid pressures in the clutches involved in the gearshift at appropriate times and to appropriate levels. Therefore, shift quality depends largely on the operation of the hydraulic system.

Hydraulic Actuators Gear Pump

The main components are:

Gear pump: It draws fluid from a sump in the bottom of the transmission and feeds it to the hydraulic system. It also feeds the transmission cooler and the torque converter.

Regulator valve: It regulates the fluid pressure from pump.
Manual Valve: It directs the fluid flow in response to a manually selected mode of operation. Depending on which gear is selected, the manual valve feeds hydraulic circuits that inhibit certain gears. For instance, if the shift lever is in third gear, it feeds a circuit that prevents overdrive from engaging.
Shift Valves: The valve body of the transmission contains several shift valves.
Magnetic Shift Valve Solenoids: The ATC controls gear position/shifting through the control of magnetic shift valve solenoids (MV). These are on/off valves (they can be normally closed or normally open). The electric signal is an off/on signal. The pressure applied to shift components is controlled by pressure regulating solenoids. These are controlled electrically by a pulse-width modulated signal moving a piston varying amounts to change pressure up and down.


An automobile equipped with a four speed adaptive transmission control was driven by a number of test drivers on an experimental basis and the engineers recorded all manual shifts as well as the corresponding calculations. The results showed that especially drivers who interacted with the specified system sparingly and for specific purposes achieved a high learning effect on the transmission: more than 40 % of the shifts they performed resulted in a permanent change of shifting strategy.

Adaptive Transmission Control is a remarkable step forward. In a sense, it makes an automatic transmission as responsive to the driver's wishes as a good manual transmission, yet without requiring any additional manual control. It improves shift consistency and transmission durability and allows for shifting that is better suited to specific driver styles or operating conditions.


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