Navigation device for personnel on foot
AssigneePoint Research Corporation
InventorsRobert W. Levi, Robert R. Marshall
Life of this patent
Estimating the term…
Abstract
Performing dead reckoning navigation for persons on foot with improved accuracy. Accelerometers in a navigation device are used to deduce when abnormal steps are being taken and modify navigation calculations accordingly. Running and walking sideways or backwards are among the situations which can be detected and compensated. One embodiment of the invention is a pedometer which is attached to the user's waist or torso. Various correlations are used to distinguish between running versus walking, forward steps versus backward steps, left turn versus right turn, and the slope of the terrain being traveled. Various algorithms are used to distinguish between such motions and accurately track the distance and direction traveled.
Claims22
A device comprising:
- one or more acceleration measuring transducers to be positioned around a user's torso to detect the user's movement in one or more axes, at least one of the acceleration measuring transducers to provide an output signal corresponding to motion along one axis;
- an altimeter to detect changes in altitude and provide a corresponding output signal;
- and
- a processing unit communicatively coupled to the plurality of acceleration measuring transducers and the altimeter, the processing unit to receive one or more signals from the one or more acceleration measuring transducers and the altimeter and generate navigation information.
A method for navigating on foot comprising:
- monitoring one or more acceleration sensors arranged mounted at a user's torso to measure acceleration along different axes;
- and
- analyzing the acceleration changes over time to determine an approximate direction of movement with respect to a first direction.
A method comprising:
- monitoring one or more accelerometers aligned along one or more axis;
- generating a signal corresponding to the acceleration sensed along the corresponding axis;
- monitoring an altimeter for an elevation signal;
- deducing a type of step taken by a user, based on one or more of the acceleration signals;
- determining a stride scaling multiplier for the deduced type of step;
- and
- scaling the nominal stride length with the scaling multiplier to estimate the correct distance traveled.
A method to distinguish between a forward step and a sideways step comprising:
- monitoring a forward acceleration signal;
- monitoring a transverse acceleration signal, the transverse acceleration direction being perpendicular to the forward acceleration direction;
- calculating the square of the forward/backward acceleration signal to generate a variance;
- calculating the square of the transverse acceleration signal to generate a variance;
- calculating the product of the forward/backward acceleration and the vertical acceleration to generate a covariance;
- determining a frequency of the forward walking steps for a user;
- passing the variances and covariance through low-pass filters with a cut-off frequency approximately the frequency of forward walking steps for a user;
- comparing the filtered forward/backward variance and transverse variances at a moment of step detection;
- and
- assuming a sideways step if the transverse variance exceeds the forward/backward variance by a ratio.
A method for distinguishing between right and left directions of travel, comprising:
- monitoring a transverse acceleration signal, the transverse acceleration direction being perpendicular to the forward/backward acceleration direction;
- and
- distinguish the direction of a sideways step motion by monitoring characteristics of the transverse acceleration signal.
A method for estimating distance traveled on foot, comprising:
- identifying a running motion by
- monitoring vertical acceleration,
- determining a difference between a maximum and minimum instantaneous vertical acceleration values within a most recent one step cycle,
- dividing this difference by the time elapsed over the most recent one step cycle;
- and
- if the quotient is greater than a threshold, adjusting a nominal stride length to accurately account for distance traveled by multiplying the nominal stride length by a proportional scaling multiplier to accurately account for the distance traveled.
A method for distinguishing between forward steps and backward steps, comprising:
- monitoring a forward/backward axis accelerometer;
- monitoring a vertical axis accelerometer;
- calculating a variance by taking the square of a forward/backward acceleration signal;
- calculating a covariance by taking the product of the forward/backward acceleration signal and a vertical acceleration signal;
- determining the product of the forward/backward variance and the forward/backward-vertical covariance;
- assuming a backward step if, at the moment a step is detected, the product is smaller than a threshold;
- and
- otherwise, assuming a forward step.
Dependencies are inferred from the claim text.