Abstract
Keywords- Hybrid vehicle, Fuel economy, Situational awareness, Air conditioning, Telematics, Electronic horizon
The Sentience program has created a variant of the Ford Escape hybrid with significantly reduced CO2 emissions by using current and predicted future geographical and situational awareness to optimise the efficiency of vehicle systems.
This work was undertaken with participation from innovITS, Ricardo UK, Jaguar/Land Rover (with support from Ford North America), Transport Research Laboratory, Ordnance Survey and Orange.
The vehicle powertrain is unchanged from a current (USA) production Ford Escape hybrid (this vehicle is not available in Europe). To this vehicle is added GPS so it knows its current location, a wireless (GSM & 3G) link to provide the vehicle with real-time data (e.g. congestion, weather), as well as a supervisory controller and human-machine interface (HMI).
The control system was developed by using a validated vehicle model and dynamic programming to find the optimum way to use the gasoline engine, two electric machines and battery that make up the vehicle's powertrain. This knowledge was then embedded into the supervisory controller on the vehicle.
The paper briefly describes the vehicle model used and its validation. It lists the various data sources used and situations where the use of this data can reduce the vehicle's CO2 emissions. This will lead onto a discussion about the amount of forward knowledge required and the impacts of its accuracy. For example if congestion can be accurately predicted ahead it may be appropriate to ensure the battery is almost fully charged before this is met. If the battery is fully charged then it cannot capture the regenerative energy that is available when the vehicle is slowed down. Conversely, if the battery is almost discharged then the ability to drive the vehicle at slow speed in EV mode for any significant period of time, as may well occur in the case of heavy congestion, will be extremely limited.
The impact of air-conditioning within the hybrid system is also considered where occupant comfort needs to be balanced against CO2 emissions. This is important as air conditioning is a significant additional energy sink and hence indirectly it is a significant producer of CO2. It will be shown that it is possible to optimise the control strategy so that overall CO2 emissions are minimised while keeping an acceptable level of occupant comfort. Further it will be shown that by using current and predicted future geographical and situational awareness this process is made even more effective.
The conference presentation will compare the predicted improvements in CO2 emissions with those measured on the prototype vehicle over a number of representative test drives on public roads.