|The Intelligent HYBRID operating strategy manages the state of charge of the battery to exploit the potential for energy recuperation. Click to enlarge.|
Mercedes-Benz has developed an intelligent energy management system for hybrid vehicles that assesses the road ahead and takes it into account. The objectives of the “Intelligent HYBRID” system are to maximize the benefit of recuperation energy and to provide driving pleasure through the boost effect of the electric motor. (Earlier post.)
The Intelligent HYBRID operating strategy, which Mercedes-Benz has employed in the S-Class since summer 2013 and now also uses in the new C-Class, ensures that the high-voltage battery is always charged only enough to take advantage of all opportunities for recuperation provided by the route and the terrain.
To achieve this, the system constantly monitors the topography ahead of the vehicle. This works not only when route guidance by the navigation system is active, but also when that system is not in use.
Many hybrid vehicles waste energy when driving downhill, Mercedes says, because frequently the high-voltage battery has too high a charge at the wrong time to be able to store the additional recuperation energy thereby generated.
With the Mercedes system, if the state of charge of the battery is too high, the electric motor automatically boosts the combustion engine to discharge the battery enough to be able to store fully the expected recuperation energy. At the same time, thanks to the boost from the electric motor, the vehicle uses less fuel and thus produces fewer emissions during this phase.
The system uses data from the COMAND Online navigation system to calculate the recuperation potential of the road ahead. For example, the data provides forward-looking information about the route profile and speed limits in a one-meter grid for up to seven kilometers (4.3 miles) in advance.
This information is processed by the Central Powertrain Controller (CPC), which then initiates the anticipatory measures. It not only lowers the battery charge in line with the situation before a downhill stretch by expanding the all-electric or boost periods, but also controls the potentially necessary recharging of the battery by the combustion engine with foresight in order to benefit from the most favorable battery state of charge.
Further adaptive control algorithms additionally take the current vehicle weight, the driving behavior (including vehicle speed and braking behavior) and the load of the ancillary consumers into account for predicting the recuperation potential.
Intelligent HYBRID also functions when route guidance is inactive. In this case the system calculates the probability of the driver making a turn dependent on the category of the road. For example, if the hybrid vehicle is travelling on a motorway, it assumes that the vehicle will probably continue on the motorway for the next seven kilometers.
Intelligent HYBRID keeps the driver informed about an upcoming elevated recuperation potential by highlighting the road ahead of the vehicle in green on the energy flow display.
How much fuel is being saved depends on the topography. This has been demonstrated by experience from many thousands of test kilometers. The more mountains there are, the higher the fuel savings will be; i.e., the effect will be more noticeable in the mountains than on plains.
In developing new hybrid models, Mercedes-Benz says it has benefited immensely from cooperating with its Formula 1 racing team, which also makes use of advanced hybrid engines to achieve fuel savings. This can result in synergistic effects both for series production vehicles as well as racing cars.