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Gently Pulsating Accelerator Better than Warning Lights or Audible Alerts

Feb 23, 2010

Continental's Accelerator Force Feedback Pedal can signal the ideal gearshift point for maximum fuel economy and also warn of upcoming hazards. Drivers prove far more receptive than to visual or audible alerts.

Babenhausen/Germany. The Accelerator Force Feedback Pedal (AFFP®) from international automotive supplier Continental is the world's first mass-produced active accelerator pedal. It provides a new way to warn drivers of potential hazards or help them adopt a more fuel-efficient style of driving. "If the existing technical means of boosting road safety, cutting fuel consumption and thereby reducing CO2 emissions are to take full effect, communication between vehicle and driver needs to be improved," Dr. Peter Laier told the press. Laier heads up the Chassis Components Business Unit at Continental's Chassis & Safety Division. "Because ultimately it's the driver who determines whether the vehicle's full technological potential is actually realized. The AFFP® intelligent accelerator developed by Continental uses haptic feedback signals – such as a discreet double 'ticking' interval or a counterforce in the accelerator pedal – to assist the driver." Trials have shown that drivers are far more responsive to such signals than to warning lights or audible alerts. In addition, by signaling the optimal gearshift point, this Human Machine Interface (HMI) can lead to fuel savings of up to seven percent, depending on the type of vehicle.

Drivers register haptic feedback faster than visual or audible signals

AFFP® can signal the ideal gearshift point and also warn for upcoming hazards Click here to download this image

Drivers are bombarded with information, particularly in heavy urban traffic. So the potential for using lights or displays to warn them of hazards or help them save fuel is very limited. With so much of their attention devoted to the surrounding traffic, dashboard displays or the navigation system, drivers simply do not have the capacity to register even more visual information. The same applies to audible alerts, which often have to compete with the radio, navigation instructions, or the telephone for example, so that the driver's response will likely be delayed, if indeed the warning is heard at all.

The Accelerator Force Feedback Pedal makes it possible to communicate directly with the driver and provide information in such a way that it can be intuitively understood, and acted upon with no additional stress. These are the findings of a joint study carried out by Continental and Munich Technical University in 2009. The study was based on a test vehicle with manual transmission, fitted as standard with a visual gearshift indicator and additionally equipped with AFFP®. The information these systems use to indicate the optimal gearshift point was in both cases supplied by the engine control unit, via the vehicle's CAN databus.

A double "ticking" interval of the accelerator was used to tell the driver when to shift up or down. If the driver failed to respond, the cycle was repeated two more times, in each case after a brief pause, but it was not repeated a third time. The study participants were asked to complete three 50-kilometer runs along a ring road in Munich: once without a gearshift indicator; once with just the visual gearshift indicator; and once with the visual gearshift indicator plus the AFFP® haptic alert system.

The findings were clear: Drivers paid little attention to the visual gearshift indicator, which led to a reduction in CO2 emissions of just half a gram/km, whereas the AFFP® signals prompted far more gearshifts. With AFFP®, the average fuel consumption for all study participants fell from 8.8 to 8.1 liters/100km, or by 15.8 grams of CO2/km – a reduction of 7.7 percent. And when, as part of the study, the drivers were asked how they felt about the haptic pedal, their responses were very positive.

Similarly positive results were obtained in a study carried out with the Institute for Product Development (IPEK) at the University of Karlsruhe, which looked at typical driving situations in a vehicle with automatic transmission. Here too, AFFP® can assist drivers in a wide range of everyday driving situations:

• Wherever a speed limit applies, AFFP® can interact with a traffic-sign recognition camera to increase pedal resistance and thereby optimize the phase in which the driver lifts off the accelerator and the car goes into overrun. The resulting increase in overrun fuel cut-off leads to a dramatic reduction in fuel consumption.

• When the time comes to accelerate again, prompting by AFFP® not only shortens the acceleration maneuver but also achieves better fuel economy, by making best use of the peak efficiency range of the engine and powertrain.

Active accelerator scalable for any type of vehicle

Click here to download this image The central mechanical feature of the AFFP® is an electric motor which is linked to the accelerator and which can generate a haptic signal

The central mechanical feature of the Accelerator Force Feedback Pedal is an electric motor which is linked to the accelerator and which can generate a haptic signal in the form of a counterforce in the pedal. The pedal's active and passive functions are designed in such a way that it is not possible for the active function to counteract – let alone negate – the effect of the return springs of the passive pedal. This means that the actuator cannot cause the vehicle to accelerate and the required passive pedal return force is maintained at all times.

Broadly speaking, vehicle manufacturers are free to choose for themselves exactly how they implement the AFFP® functions in their vehicles and what type or intensity of signal they use for the pedal feedback. For example, the pedal can vibrate twice to indicate the ideal gearshift point; increased counterforce can prompt the driver to lift the foot off the accelerator; or distinct vibration can warn of hazards, such as when a safe distance to the vehicle in front is no longer maintained.

AFFP® is therefore an adaptable interface that allows vehicle manufacturers to choose the configuration of features – increased safety, greater comfort through reduced driver stress, or lower fuel consumption – that they wish to implement. Such is the adaptability of the AFFP® system that a driver's personal preferences for a particular type of signal can be entered into the system memory. These settings are then automatically recalled as soon as the driver's personal ignition key is identified. AFFP® can be fitted in any vehicle, and is available in both suspended pedal and floor-mounted pedal versions. This means the active accelerator can also be fitted in small vans or heavy trucks – categories of vehicle in which inadequate following distances and driver fatigue have been identified as the most frequent causes of accidents.

The active accelerator can be used as a stand-alone solution or as a haptic interface between the driver and other driver assistance systems. If AFFP® is integrated into an electronic horizon system that also incorporates GPS and navigation data, the pedal can alert the driver in good time to situations that are not even in sight – such as a tailback or a red light around the next bend. In urban motoring, the system can also issue discreet prompts that help the driver catch a series of traffic lights on green.

When, in the future, cars are networked via car-to-car or car-to-infrastructure communication, the lines between the safety and fuel-efficiency benefits of AFFP® will merge and become even more obvious. Vehicles will be able to inform one another when they are approaching intersections, so that drivers are alerted to other road users with right of way and receive a timely prompt to lift the foot off the accelerator.

AFFP® also offers potential for hybrid and electric vehicles. For example, feedback to the driver of a hybrid car could indicate that the chosen throttle position will activate the internal combustion engine, while in an electric vehicle the active accelerator could be used to indicate how the style of driving is influencing the vehicle's remaining range.


Nicole Geissler

External Communication


Division Chassis & Safety

Guerickestraße 7

60488 Frankfurt am Main

Phone:   +49 69 7603-8492

Fax:      +49 69 7603-3945

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