It has been discussed in numerous prior studies that in-neutral coasting, or sailing, can accomplish considerable amount of fuel saving when properly used. The driving maneuver basically makes the vehicle sail in neutral gear when propulsion is unnecessary. By disengaging a clutch or shifting the gear to neutral, the vehicle may better utilize its kinetic energy by avoiding dragging from the engine side. This strategy has been carried over to series production recently in some of the vehicles on the market and has become one of the eco-mode features available in current vehicles. However, the duration of coasting must be long enough to attain more fuel economy benefit than deceleration fuel cutoff (DFCO)-which exists in all current vehicle powertrain controllers-can bring. Also, the transients during shifting back to drive gear can result in a drivability concern. The in-neutral coasting system should automatically shift to drive in case of nearby traffic for safe operation capability.
To mitigate those issues, this article proposes an in-neutral coasting control algorithm that utilizes information from advanced driver assistance system (ADAS). By monitoring driving condition ahead, such as distance and relative velocity to preceding vehicle, the algorithm can identify the appropriate coasting opportunity. The developed logic has been implemented in a test vehicle for validation and showed promising performance. The on-road test results and fuel economy analysis are presented with the description of the coasting algorithm.
