|OpEneR partners have developed driving strategies and driver assistance systems to improve the efficiency and safety of electric vehicles. Click to enlarge.|
At its final review, the European research project OpEneR (“optimal energy consumption and recovery based on a system network”) presented collaboratively developed driving strategies and driver assistance systems to improve significantly the efficiency (and hence range) and safety of electric vehicles by optimizing energy management. (Earlier post.)
In comparison to a typical sporty driver, the OpEneR operation strategies resulted in a reduced energy consumption of 27 to 36%, with the trade-off of an increase in travel time of between 8 to 21%—depending on the driver’s willingness to follow the recommendations. Approximately 5 percentage points of the energy consumption reduction were due to intelligent torque distribution between front and rear electric motors in the demonstrators, which had no influence on travel time at all.
Engineers and researchers worked to improve the electrical powertrain, the regenerative braking system, the navigation system, and the surround sensors, as well as on functions that connect these elements with each other. The project partners built two fully operational electric vehicles that have already demonstrated potential for making driving in real conditions more economical.
OpEneR was launched in May 2011. The project partners were the Austrian powertrain development company AVL List GmbH; the Spanish research institute Centro Tecnológico de Automoción de Galicia (CTAG); the German research institute Forschungszentrum Informatik Karlsruhe (FZI); the second-largest carmaker in Europe PSA Peugeot Citroën; and the German companies Robert Bosch GmbH and Robert Bosch Car Multimedia GmbH.
The project was a European research project under the Seventh Framework Program, co-funded by the European Commission – Directorate Communications Networks, Content and Technology. The total budget was €7.74 million (US$10.5 million), €4.4 million (US$6 million) of this sum in the form of subsidies. The project was led by Bosch.
A central goal of OpEneR was the investigation of an innovative and highly efficient overall energy manager that uses information from underlying subsystems to generate optimal driving and operation strategies. The strategies vary from time-optimized to range-maximized.
One task was the development of “eco routing”. This considers the specific needs of an electric vehicle when calculating the best route. The navigation system now continuously factors in the car’s real energy consumption behavior. Test drives demonstrated energy consumption savings of up to 30% in return for a longer travel time of just 14%. Shortcuts in inner-city traffic proved to be a particularly effective way of increasing efficiency.
Various solutions increase driving efficiency. It has long been widely accepted that a proactive driving style is a very effective way to reduce fuel consumption. The partners thus adapted the behavior of the adaptive cruise control (ACC) to an economical driving style. Additionally, enhanced map data also included information on inclines, declines, and speed limits, while car-to-infrastructure communication provided information about traffic lights.
These data created an electronic horizon used to further optimize both the ACC function and the coasting function. This feature tells drivers when to lift the accelerator pedal as they approach city boundaries or speed limits. The transmission then switches to idle, making the most of the car’s momentum.
The partners also designed an intuitive HMI concept and an attractive cockpit based on a freely programmable TFT display to make all the relevant information easy to read. In addition, the enhanced map data made the calculation of the remaining mileage significantly more accurate and transparent to the driver.
A further major task was to find the ideal interaction between the electrical powertrain and the regenerative braking system. For the best possible recuperation, engineers equipped the two Peugeot 3008 e-4WD demo cars with the Bosch iBooster, an electromechanical brake booster, and an ESP brake control system specifically adapted for electric vehicles.
The powertrain concept comprised two electric motors—one per axle—that can both drive as well as recuperate. On that technical basis, the partners developed innovative recuperation strategies, including a regenerative brake force distribution between front and rear, optimizing recuperation rates as well as vehicle stability.
To support the development process, the team used advanced co-simulation techniques, including realistic vehicle and environment interaction. A seamless approach was employed to enable fast migration of the developed functions and their simulated test cases for further development and validation on the AVL InMotion powertrain testbed.
As these features were incorporated into the two prototypes, numerous test drives were performed. To evaluate the efficiency gain, the simulation tools and testbeds developed by AVL, Bosch, and FZI were used, as well as the private test tracks belonging to Bosch and CTAG, and CTAG’s intelligent public road corridor.