Under the microscope: the intelligent operating strategy: Better electric performance

Sep 14, 2019
Stuttgart/Frankfurt

The intelligent, route-based operating strategy activates the electric driving mode where this is most appropriate for the route. For example, it takes into account navigation data, topography, speed limits and the traffic conditions for the entire planned route. The ECO Assistant coaches the driver and helps to save fuel.

With the launch of MBUX (Mercedes-Benz User Experience) the previous plug-in operating modes of all EQ Power models have been converted to drive programs. That means that in every Mercedes-Benz plug-in hybrid the new drive programs "Electric" and "Battery Level" are available. Maximum e-performance can be experienced in "Electric". The combustion engine is only engaged if the driver uses kickdown on the accelerator pedal. In the "Electric" program the recuperation strength can also be selected via paddles behind the steering wheel. The paddles on the steering wheel enable the selection of five different recuperation levels (DAUTO, D+, D, D- and D--).

 Comfort, ECO and Sport modes are also available (as well as Offroad mode for SUV models). According to the given requirements, the driver is thus able to give priority to electric driving, place the emphasis on driving dynamics in combined drive mode or give preference to combustion mode in order to save electric range, for example.

Intelligent operating strategy: Supporting the driver

Third-generation hybrid technology supports the driver with further-improved, intelligent powertrain management. This covers all processes that access the onboard power supply and influence consumption,

  • including the hybrid operating strategy, i.e. interaction between the electric motor and the combustion engine,
  • the shift strategy of the transmission,
  • thermal management, i.e. energy-efficient control of the cooling circuit for the combustion engine and electric assemblies to maximise the all-electric range,
  • recuperation management and,
  • in the diesel hybrids, even regeneration of the particulate filter

Through the extended use of data from the navigation system and information from the camera and the radar sensors, third-generation hybrid vehicles can look ahead well beyond the driver's field of vision and adjust to the specific speed/route profile. Events such as negotiating towns on the way to the destination are taken into account when planning the available electrical energy, and during recuperation and thermal conditioning of the powertrain components. The ECO Assistant also helps to save energy.

ECO Assist: connected driving strategy for intelligent efficiency

Those who drive in an anticipatory manner save fuel and reduce CO2 emissions. In Mercedes-Benz vehicles intelligent assistants support the driver. ECO Assist coaches the driver with messages when the accelerator can be released, e.g. because a speed limit is approaching, and with functions such as gliding and specific control of recuperation. For this purpose, navigation data, traffic sign recognition and information from the intelligent safety assistants (radar and stereo camera) are linked and processed.

ECO Assist takes the following traffic situations and information into account in its driving recommendations and efficiency strategy:

  • Route profile (bends, junctions, roundabouts, gradients)
  • Speed limits
  • Distance from vehicles travelling ahead

ECO Assist continuously generates coasting simulations in the background: depending on the state of charge of the battery and the traffic situation, it computes whether the vehicle should ideally be allowed to coast with the lowest possible driving resistance with the driver's foot off the pedals, or whether it should be decelerated so that the battery can be efficiently charged (recuperation).

Within the limits of the system, ECO Assist controls the overrun according to the situation as soon as the driver's foot leaves the accelerator. The driver is also given a visual prompt to do this: by showing a "foot off the accelerator" symbol in the media display (or if available, in the head-up display). At the same time, a diagram gives the driver the reason for the recommendation (e.g. "Junction ahead" or "Gradient ahead").

ECO Assist predictively computes the driving situation when deciding whether to drive with the lowest resistance or whether to recuperate. Examples include dips, brows or speed limits ahead, which the system recognises from the map data.

  • Dip: The vehicle recognises that a downhill gradient is followed by a climb, and that a speed limit is shown. The driver receives the prompt "Foot off accelerator" in good time. As soon as the driver acts on this, the vehicle continues with the drive switched off. Recuperation takes place on the downhill stretch, but only enough to ensure that the maximum permitted speed is maintained. Recuperation ends just before the lowest point in the dip, and coasting commences to maintain as much impetus as possible for the uphill stretch in the interests of energy efficiency.
  • Brow: If ECO Assist recognises that "gliding" makes sense on account of the individual driving situation, the topography and the speed limits, the driver is told to "remove foot from accelerator" even before reaching the brow. The vehicle then drives over the brow in "gliding" mode, and subsequently uses the downhill stretch to reach the target speed.
  • Speed limit: When the system recognises a speed limit from the navigation data or via Traffic Sign Assist, the driver is once again prompted with "Foot off accelerator pedal". The vehicle is then gently decelerated (while recuperating) to the new speed, followed by coasting. In this way suitable speeds for junctions, roundabouts and bends are also supported.
  • Slow-moving traffic: When the radar sensors of the system recognise slow-moving vehicles ahead while coasting, gliding is automatically interrupted if necessary. Deceleration with recuperation takes place to the extent that braking action by the driver is often unnecessary. If the vehicle ahead accelerates, coasting is reactivated automatically so as to cease deceleration and maintain the current speed as much as possible. The driver operates the accelerator if needed.

Some of the hybrid and electric vehicles of Mercedes-Benz also have a haptic accelerator pedal. This generally helps the driver to achieve an economical and comfortable driving style. A pressure point in the pedal, for example, tells the driver that the maximum electric power is being delivered. If the driver moves the pedal beyond the pressure point, the combustion engine kicks in. A perceptible resistance in the haptic accelerator advises the driver to take their foot off the accelerator. If the driver follows this recommendation, the combustion engine is switched off and decoupled from the powertrain.

Another special feature of the hybrid models: The onboard computer records for how many kilometres/how much time the vehicle travelled without the combustion engine, and shows this in the media display. This motivates the driver to use electric mode: the reward not only takes the form of reduced fuel consumption, but also an increased electric range.

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