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MOTOR CONTROL & DRIVES Fig. 3: Results of a test drive on a gravel road. The measurement of the roll rate of SMI7 (upper graph) shows an excellent agreement with the output of an industrial reference sensor. The lower three graphs indicate the corresponding rough road conditions: Despite of nearly 1000 g peak to peak acceleration caused by stones, there is no significant signal distortion visible at angular rate signals. standard for automotive functional safety. In order to fulfill the requirements of ASIL D systems, Bosch relied on its system competence, its expertise in sensor integration as well as in semiconductor and MEMS design. System specialists shaped the hardware safety requirements of SMI7 components by deriving them from safety goals of car systems for airbag, vehicle dynamics, electronic parking brake, or active front steering. Semiconductor specialists designed SMI7 such that these demanding requirements can be fulfilled, by introducing able monitors into the signal path and by systematically evaluating the sensor performance by Fault Tree Analysis (FTA) and the Failure Modes Effects and Diagnostic (FMEDA) method. As a result, the applicability of SMI7 sensors in ASIL D vehicle dynamics systems was confirmed by a functional safety assessment according to ISO26262. SMI7 sensors are designed for use in integrated airbag ECUs (ABplus) or for sensor clusters (e.g. MM7), which allow to locate the sensor close to the center-of-gravity of the car. In order to achieve the necessary performance with respect to mission profile or vibration loads, engineers need to reflect corresponding requirements in each part of the sensor design. The choice of package, the design of MEMS elements and read-out ASICs need to mate in order to result in an excellent offset performance at hardest driving conditions. Figure 2 displays the offset stability of the low-g sensor output of the integrated accelerometers indicating the excellent performance of SMI7. The promising laboratory measurements were verified in a real-world scenario: A vehicle test-drive on a gravel road. Driving maneuvers under bad road conditions or on gravel roads constitute the hardest test for an inertial sensor in vehicle dynamics applications. Figure 3 shows an example of such a test drive: Despite high-frequency signals of up to 4000 m/s², the deviations between SMI7 in an MM7 sensor cluster and an industrial reference sensor were negligible. These measurements prove impressively, that SMI7 clearly fulfills the expectations for an automotive inertial sensor, such that you can trust the equilibrium sense of your car in every situation. www.electronics-eetimes.com innovation. reliability. power. Highly-integrated SCALE-2® ASIC chipset UL-certified IGBT driver cores 100% design flexibility focused on excellence www.IGBT-Driver.com Visit us at electronica Power Integrations Hall A5 Stand 507 Highly-integrated SCALE™-2 ASIC chipset UL-certified IGBT driver cores 100% design flexibility


EETE NOV 2014
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