Signal Monitoring

Faulty Yaw Rate & Lateral G sensor

Open or short of Yaw Rate & Lateral G sensor

Continuous (during stable driving)

By building a reference lateral G from the yaw-rate sensor, wheel speed sensor and the SAS it is possible to test the lateral G Signal on plausibility. If during stable vehicle behavior an lateral G Failure larger than approximately 2.5 m/s2 occurs, the ESP controller will disregard the later G sensor information so that a false ESP intervention is prevented. A fault is recognized after 1.6 s during model validity.

The measured and offset compensated yaw rate signal is compared to the reference yaw rate signal calculated from yaw rate sensor, lateral G sensor, SAS and wheel speed sensor. If the measured yaw rate deviates more than 2.5 °/s plus a dynamic threshold from the reference yaw rate during model validity, a failure is recognized after 1.6 s. The dynamic threshold is between 2.5 °/s and more than 5°/s. A typical value is 3°/s.

- During the possibility to observe the recognition time depends on the amount of failure.

Continuous (during driving)

During normal driving conditions the long time filtered driving direction is straight ahead. The long time filtered lateral G value is equivalent to the offset. If the offset value exceeds a threshold of approximately 2.25 m/s2 an lateral G fault is determined.Failure detection time depends on the driving distance, vehicle speed and on the amount of failed lateral G signal. Within 30 km of symmetrical driving the calculated offset corresconds to the sensor offset.

Continuous (If no under voltage is detected)

A fault is detected If the lateral G is higher than 15 m/s2 for more than 800ms.

Continuous (during driving)

If the filtered value of lateral G is larger than 7 m/s2 for more than 400 m/s, a fault is set.

Continuous (dependent on driving situation)

Standstill compensation :

- The offset corresconds to the measured and filtered input value. Failure threshold 5.25 °/s.

Fast compensation (during driving if no standstill compensation could be completed):

- The offset corresconds to the slightly filtered deviation between measured yaw rate and the reference yaw rate calculated from SAS, lateral G sensor and wheel speed sensor. Failure threshold is 7.5 °/s.

Long-term ("normal") compensation (during driving after succeeded standstill or fast offset compensation):

- The offset corresconds to the strong filtered deviation between measured yaw rate and the reference yaw rate calculated from SAS, lateral G sensor and wheel speed sensor. Failure threshold is 7.5 °/s.

After every standstill.

Yaw-rate sensor sensitivity is estimated by comparison of the measured yaw rate and the yaw rates calculated from the wheel speed sensor and SAS during cornering. The fault criteria is approx. 25% sensitivity.

The measured yaw rate and the model yaw rates, calculated from the wheel speed sensor and SAS are compared. If the signals doesn't fit and forward driving is reconized, a fault is determined.

- Driving with a yaw rate of e.g. 10 °/s requires a time of 3s and additional time to reach a velocity 20 m/s to recognize forward driving.

Continuous (after initialization of the YRS(yaw rate sensor) and if no under voltage is detected)

The yaw rate sensor BITE logic evaluates the BITE-signal by extraction of the measured yaw rate of the vehicle. The allowed range for the BITE-signal is 25°/s ± 7°/s. If the BITE-signal is not in the allowed range, a suspected failure bit is set after 200ms.

After YRS(yaw rate sensor)-initialization, no under voltage

Depending on the driving conditions a signal gradient higher than 10 ~ 23 °/s / 40 ms sets a suspected failure bit after 280ms, unless a single signal peak is recognized by a peakfilter.

Continuous (except spinning, use of handbrake, unsteady driving conditions or a detected under voltage)

During standstill

- The allowed range of the yaw rate sensor signal is ±30°/s. Leaving this range for 5s sets a fault. In case of driving off after the failure was present for longer than 500ms during standstill, the fault is detected immediately.

While driving

- The allowed range of the yaw rate sensor signal is ±94.75°/s and a suspected failure bit is set, if the signal is out of this range for 500ms.

Once after power up and no low voltage.

A line fault is detected if 0.2V < VLG < 0.8V isn't continued for a time t >= 60ms during POS (POS : power on selftest)

Reduced controller function.

Inhibit the ESP control and allow the ABS/EBD control.

The ESP warning lamps are activated.