Zero motion detection system for improved vehicle navigation system

A vehicle navigation system having an improved zero motion detection system comprising:

• a motion detection sensor which provides motion signals with an offset, wherein said motion detection sensor is an orthogonal axes accelerometer which provides motion signals with an offset for each axis of said accelerometer;
• said zero motion detection system compares at least one sample of said motion signals with a threshold to determine a zero motion state, and if in said zero motion state, said detection system determines said offset;
• and
• said navigation system propagates a previous position to a current position based upon a non-zero velocity signal when said zero motion state is not determined, said navigation system ignoring said non-zero velocity signal and locking a previously determined position based upon said determination of said zero motion state, said zero motion detection system compares at least two samples of said motion signals with a threshold to determine said zero motion state, and if in said zero motion state, said detection system determines a zero offset for each axis of said accelerometer by averaging samples of said motion signals for each axis, and said zero motion detection system provides a zero motion signal to lock heading changes and calibrate velocity information.

A method of detecting a zero motion state, said method comprising the steps of:

• providing a motion sensor signal having an offset,
• determining a zero motion state by comparing at least one sample of said motion sensor signal with a threshold;
• using at least one of said samples to determine said offset if said zero motion state is detected;
• and
• locking a previously determined position based upon said determining of said zero motion state.

A method of detecting a zero motion state, said method including the steps of:

• providing a motion sensor signal having an offset;
• determining a zero motion state by comparing at least one sample of said motion sensor signal with a threshold;
• using at least one of said samples to determine said offset if said zero motion state is detected;
• and
• locking a previously determined position based upon said determining of said zero motion state;
• providing said motion sensor signal and said offset for at least one axis of an orthogonal axes accelerometer;
• determining said zero motion state by comparing at least two samples of said motion sensor signal with said threshold;
• providing a zero motion signal based upon said determining said zero motion state;
• locking heading changes and calibrating velocity information in response to said zero motion signal;
• and
• averaging said samples to determine said offset if said zero motion state is detected.