Many world governments have a long-standing target for car manufacturers to reduce average CO2 emissions for their vehicles. The European Union target is 120g/km by 2012 and longer term to 80g/km by 2020. The view of the industry has been that this is very challenging and unlikely to be met via conventional approaches alone. Indeed, the 2012 target already represents a slip from an original 2005 target date. As most manufacturers will not be able to meet the 2012 target, further slippages (possibly to 2015) and concessions (exclusions for heavier vehicles) are already on the table.
So what has all this got to do with GPS? The answer is that GPS is one technology that might be able to help reduce vehicle emissions. How might this work? Let’s assume that your vehicle is a hybrid, running on batteries part of the time to help meet the 120g/km and certainly the 80g/km target. The more the batteries are used, the lower the emissions. Hybrid car systems have limits set on the depth of discharge that the battery systems can be taken to before the engine kicks in. Often these limits include quite large margins.
Imagine for a minute, though, that your car also has a GPS system. This means that the vehicle can benefit from knowing not only where it is, but also from where it is going. Specifically, if the car systems know what’s coming up ahead, this information particularly related to inclines, could be used to optimize the performance of the hybrid system. In a simplistic example, if the car is going up hill, the batteries can be used more if the vehicle system knows that a down gradient is coming where a predictable level of recharging will be possible. It doesn’t take much of a leap to wonder, could this process be maximized by taking the decisions out of the hands of the driver? Automatic transmission coupled to knowledge of the road coming up (from the GPS system) could provide an answer. By knowing the nature of the road ahead, for example corner radius, duration and gradient, the transmission system could be optimised for economy.
Initially, at least, the driver would need an option to override such a system and optimise for sporty performance, fast response etc. There has been talk of “vehicle trains” for some time, whereby on higher classes of road the vehicle systems would take over and maintain optimum speed and distance from other vehicles. The barriers to these systems becoming a reality are rapidly being removed.
From a satellite navigation perspective, two key elements required are position accuracy to the lane level and high integrity, or trustworthiness, of the data. Lane level accuracy ideally requires dual frequency satellite navigation capability. This enables the atmospheric ambiguity to be backed out of the position calculation, providing sub metre accuracy.
Integrity is more challenging, particularly when autonomous vehicles travelling at high speed and in close proximity are concerned. This is likely to be the limiting factor in vehicle trains becoming a reality. In practice, a variety of approaches will be necessary to ensure the safety guarantees that will be expected. These will include augmentation systems like proximity radar and inertial sensors. Also likely, are roadside re-calibration systems that act as reference stations for the mobile satellite navigation systems in the moving vehicles.
Spirent has wide experience of helping companies in this sector understand their test issues and the best approach to testing. Spirent can help, contact gnss-solutions@spirent.com for more information.
