Hybrid vehicle design ready for Olympic duties

Edited by the Engineeringtalk editorial team Aug 7, 2008

Ricardo was a natural choice of engineering partner for Chery when the Chinese automaker decided to develop its first hybrid products.

As a part of the transportation arrangements for the Beijing Olympics, a 50-unit fleet of hybrid vehicles codeveloped with Ricardo is being provided by Chery Automobile Company.

Known as the "Olympics Green Messengers", these vehicles are some of China's first hybrid vehicles and will go into full production in the months following the games.

With its expertise in hybrid electric vehicles and its wide-ranging skills in systems integration and vehicle control and electronics, Ricardo was a natural choice of engineering partner for Chery when the Chinese automaker decided to develop its first hybrid products.

Two new vehicles, both based on its existing A5 sedan model, were identified by Chery.

The first is a stop-start hybrid based on a 12V belt starter-generator (BSG) linked to 1.6 litre petrol engine, itself linked to a five-speed manual transmission.

The second is a more comprehensive mild-hybrid based on the same baseline vehicle but instead equipped with a 1.3 litre gasoline engine and a 12kW crankshaft-mounted 151V integrated starter-generator (ISG).

These technologies have been configured to be capable of providing significant fuel savings through the use of advanced powertrain control and energy management strategies.

In addition to developing these two new hybrid products, an important objective of the programme for Chery was technology transfer through integration of the joint programmes with its own engineering processes.

For this reason a dedicated on-site engineering office was established at the Ricardo Cambridge Technical Centre.

Here, Chery engineers were able to work alongside colleagues from Ricardo as well as with selected component and subsystem suppliers, and could undertake key aspects of the project.

Key Ricardo responsibilities for the BSG programme included full architecture, subsystem and components requirements definition, hybrid control unit design, vehicle and communications interface development, system design - including detailed thermal analysis - and powertrain control strategy for safety and efficient operation.

The focus of the engineering programme and the efficiency of the development programme were such that the first prototype vehicle was run with production-intent hardware and complete with hybrid strategy and application software, just ten months from programme start.

The final fuel economy results are no less impressive: in tests over the ECE Urban drive cycle, the BSG vehicle achieves approximately a 7% improvement in fuel consumption over the baseline product, and it is expected that the improvement will be greater than 10% in real-world urban driving.

For the more complex ISG product, Ricardo carried full system design authority including specification and integration of the ISG system, high-voltage battery pack and battery management system, and developed an integrated hybrid control unit that incorporates the motor drive power electronics, DC/DC convertor and hybrid supervisory and safety functions into one compact package.

The safety-critical application strategies and software were defined, engineered and validated including extensive vehicle and hardware-in-the-loop testing.

With its comprehensive mild-hybrid functionality, the ISG-equipped sedan provides a significant increase in performance over the equivalent baseline A5 vehicle fitted with a 1.3 litre engine; peak power and torque of the ISG-equipped vehicle are comparable with that of a larger 1.6 litre engine.

Final production calibration and testing of the vehicle systems are still taking place, but the fuel consumption improvement over the NEDC cycle is expected to approach 15% compared with the 1.6 litre benchmark vehicle.

In addition, the system enables engine restart within 200ms, thus allowing stop-start functionality to be included in the hybrid control strategy.

The new BSG and ISG powertrain equipped A5 models from Chery Automobile underscore the position of this fast-growing Chinese automaker as one of China's automotive technology leaders.

Engineered to exacting European emissions requirements, these new vehicles are due to enter full production shortly and will be available for both domestic Chinese and export markets.