Automatic stop-start systems reduce fuel consumption by stopping the internal combustion engine while the vehicle is at a standstill instead of idling the engine. In addition to detecting when the vehicle is stopped, inertial sensing is used to hold the vehicle in place using the brakes while the engine is restarted. The application requirements are similar to electronic parking brakes, and in most cases the measurement functionality is integrated with the ESC system. Integrating inertial sensors with the ABS system or using them as a standalone system is also feasible.
Although automatic stop-start systems are not new, until recently the systems were used to stop the engine only when the vehicle was at a standstill. In the latest developments, the engine is stopped already when the vehicle's speed drops below a certain limit. The objective is to maximize fuel savings and minimize vehicle emissions.
Automatic stop-start systems are able to provide fuel savings up to 10% in urban driving environments without requiring a substantial redesign of the vehicle architecture compared to hybrid technology, for example. Since these systems offer one of most effective means of conserving fuel, both economically and technically, the adoption rate among OEMs is picking up rapidly.
Murata's high accuracy MEMS inclinometers provide a robust means of measuring vehicle inclination in a wide range of environmental conditions. The internal mechanical gas damping of Murata's MEMS sensors prevents them from picking up external signals that can cause errors to the inclination measurement, and the HW realization of the system is easier. High accuracy versions of the SCA8X0 and SCA21X0 sensor series are widely used in automatic stop-start applications, as well as the gyro-combo sensor SCC1300 when integrated with the ESC system.