Patent Description:
While such sensors and the information they provide have proven useful, IMU sensor drift and satellite signal availability can make it difficult or impossible to accurately determine the location or movement of the vehicle.

<CIT> discloses a pressure sensing probe. <CIT> discloses a recreational vehicle passing warning device. <CIT> discloses an apparatus to measure the power expended in propelling a vessel on water.

According to the invention, a vehicle sensor system includes a plurality of barometric pressure sensors including a first barometric pressure sensor situated on a first portion of the vehicle that faces at least partially in a first direction and a second barometric pressure sensor situated on a second portion of the vehicle that faces at least partially in a second direction that is different than the first direction. A processor is configured to make a determination regarding vehicle motion based on respective indications from the plurality of barometric pressure sensors.

In an embodiment having at least one of the features of the system of the previous paragraph, the processor is configured to make the determination regarding vehicle motion by determining at least one of whether the vehicle is stationary or moving, and whether vehicle motion resulted from movement of air near the vehicle.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the processor is configured to determine a direction of movement of air near the vehicle based on a relationship between the indication from the first barometric pressure sensor and the indication from the second barometric pressure sensor.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the plurality of barometric pressure sensors includes a third barometric pressure sensor and a fourth barometric pressure sensor, the third barometric pressure sensor is situated on a third portion of the vehicle that faces at least partially in a third direction, the fourth barometric pressure sensor is situated on a fourth portion of the vehicle that faces at least partially in a fourth direction, the first direction is generally opposite the second direction, the third direction is generally perpendicular to the first and second directions, the fourth direction is generally opposite the third direction, and the processor is configured to determine the direction based on a difference between the indication from the third barometric pressure sensor and the indication from the fourth barometric pressure sensor and a difference between the indication from the first barometric pressure sensor and the indication from the second barometric pressure sensor.

According to the invention, a vehicle motion sensor is supported on the vehicle, the vehicle motion sensor is configured to provide an indication of vehicle motion, and the processor is configured to use the determination based on the indications from the barometric pressure sensors to interpret the indication from the vehicle motion sensor.

The processor is configured to determine whether the indication from the vehicle motion sensor is a result of movement of air near the vehicle.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the processor determines a direction of movement of the vehicle from rest based on the vehicle motion sensor indication; the determination based on the indications from the barometric pressure sensors includes a direction of air movement; the processor determines that the movement of the vehicle is a result of air movement when the direction of air movement corresponds to the direction of movement of the vehicle; and the processor determines that the movement of the vehicle from rest is a result of a force different than movement of the air when the direction of air movement does not correspond to the direction of movement of the vehicle.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the processor interprets the indication from the vehicle motion sensor as a wake up signal to activate a vehicle alarm device based on determining that the movement of the vehicle is the result of the force different than the movement of the air; or the processor dismisses the indication from the vehicle motion sensor as a false alarm wake up signal based on determining that the movement of the vehicle is the result of the movement of the air.

According to the invention, the processor is configured to determine that the vehicle is in motion independent of movement of the air when the indications from the vehicle motion sensor and the plurality of barometric pressure sensors correspond to movement of the vehicle in a direction that is opposite to a direction of the movement of the air; and the processor is configured to determine that movement of the vehicle is a result of movement of the air when the indications from the vehicle motion sensor and the plurality of barometric pressure sensors correspond to movement of the vehicle in a direction that is the same as the direction of movement of the air.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the processor is configured to perform a calibration of the vehicle motion sensor when the determination regarding vehicle movement includes a determination that the vehicle is stationary.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the calibration includes removing static errors from the indication from the vehicle motion sensor while there is no movement of the vehicle.

In an example embodiment having at least one of the features of the system of any of the previous paragraphs, the vehicle motion sensor comprises an inertial measurement unit including at least an accelerometer and a gyroscope.

According to the invention, a method is provided for monitoring vehicle motion using a plurality of barometric pressure sensors including a first barometric pressure sensor situated on a first portion of the vehicle that faces at least partially in a first direction and a second barometric pressure sensor situated on a second portion of the vehicle that faces at least partially in a second direction that is different than the first direction. The method includes making a determination regarding vehicle motion based on respective indications from the plurality of barometric pressure sensors.

In an example embodiment having at least one of the features of the method of the previous paragraph, making the determination regarding vehicle motion comprises determining at least one of whether the vehicle is stationary or moving, and whether vehicle motion resulted from movement of air near the vehicle.

According to the invention, a vehicle motion sensor is supported on the vehicle and provides an indication of vehicle motion, and the method includes processing the indication from the vehicle motion sensor based on the determination regarding vehicle motion based on the indications from the plurality of barometric pressure sensors.

Processing the indication from the vehicle motion sensor comprises determining whether the indication from the vehicle motion sensor is a result of movement of air near the vehicle.

An example embodiment having at least one of the features of the method of any of the previous paragraphs includes determining a direction of movement of the vehicle from rest based on the vehicle motion sensor indication; determining a direction of air movement based on the indications from the plurality of barometric pressure sensors; determining that the movement of the vehicle is a result of air movement when the direction of air movement corresponds to the direction of movement of the vehicle; and determining that the movement of the vehicle from rest is a result of a force different than movement of the air when the direction of air movement does not correspond to the direction of movement of the vehicle.

An example embodiment having at least one of the features of the method of any of the previous paragraphs includes interpreting the indication from the vehicle motion sensor as a wake up signal to activate a vehicle alarm device based on determining that the movement of the vehicle is the result of the force different than the movement of the air; or dismissing the indication from the vehicle motion sensor as a false alarm wake up signal based on determining that the movement of the vehicle is the result of the movement of the air.

According to the invention, the method includes determining that the vehicle is in motion independent of movement of the air when the indications from the vehicle motion sensor and the plurality of barometric pressure sensors correspond to movement of the vehicle in a direction that is opposite to a direction of the movement of the air; and determining that movement of the vehicle is a result of movement of the air when the indications from the vehicle motion sensor and the plurality of barometric pressure sensors correspond to movement of the vehicle in a direction that is the same as the direction of movement of the air.

An example embodiment having at least one of the features of the method of any of the previous paragraphs includes calibrating the vehicle motion sensor based on the determination regarding vehicle movement corresponding to no movement of the vehicle.

Embodiments of this invention, such as that described below, include using information from barometric pressure sensors for making a determination regarding vehicle motion, such as whether air movement has caused vehicle motion. The barometric pressure sensor information is useful, for example, to determine whether conditions are appropriate for calibrating an inertial measurement unit or activating a vehicle alarm in response to an indication from an vehicle motion sensor.

<FIG> schematically illustrates a vehicle sensor system <NUM> that is supported on a vehicle <NUM>. The vehicle sensor system <NUM> includes a plurality of barometric pressure sensors (BPSs) <NUM>, <NUM>, <NUM> and <NUM>. The BPSs operate in a known manner to detect changes in atmospheric pressure and provide respective indications of the detected pressure. For example, the BPSs <NUM>-<NUM> provide an indication of relative movement between the vehicle <NUM> and air nearby the vehicle <NUM> as schematically represented by the lines <NUM>. Relative movement between the vehicle <NUM> and air nearby the vehicle <NUM> may be the result of vehicle motion along a driving surface, wind, or a combination of them.

A first BPS <NUM> is supported on a portion of the vehicle <NUM> that faces at least partially in a first direction. In the illustrated example, the first BPS <NUM> is supported on a front of the vehicle <NUM>. A second BPS <NUM> is supported on a second portion of the vehicle <NUM> that faces at least partially in a second direction that is different than the first direction. In the illustrated example, the second BPS <NUM> is supported on the rear or back of the vehicle <NUM>. A third BPS <NUM> and a fourth BPS <NUM> are supported on oppositely facing sides of the vehicle <NUM>.

A processor <NUM>, which includes a computing device, receives indications or the output of each of the BPSs <NUM>-<NUM>. The processor <NUM> uses the indications from the BPSs <NUM>-<NUM> to make a determination regarding vehicle movement, which may include a feature or characteristic of relative movement between the vehicle <NUM> and the air nearby the vehicle <NUM>.

The vehicle sensor system <NUM> also includes at least one vehicle motion sensor <NUM>. In the illustrated example embodiment, an inertial measurement unit (IMU) <NUM> provides an indication of vehicle motion. The IMU <NUM> includes an accelerometer and a gyroscope, both of which provide an indication of vehicle motion. The indication from the IMU <NUM> will be considered to be a result of the operation of either the gyroscope or accelerometer in this description except where noted below.

<FIG> is a flowchart diagram <NUM> summarizing how the processor <NUM> uses indications from the BPSs <NUM>-<NUM>. At <NUM>, the processor <NUM> receives an indication from the first BPS <NUM> corresponding to air pressure detected by the first BPS <NUM> at the front of the vehicle <NUM>. The detected air pressure may be the result of air movement or wind directed at the front of the vehicle <NUM> or movement of the vehicle <NUM> in a forward direction, for example. At <NUM>, the processor <NUM> receives an indication from the second BPS <NUM> corresponding to air pressure detected by the second BPS <NUM>. At <NUM>, the processor <NUM> makes a determination regarding vehicle motion based on the received indications.

The processor <NUM> makes the determination regarding vehicle motion in some instances by determining whether the vehicle <NUM> is stationary or in motion. In other words, the determination may be regarding a state of vehicle motion, which can be a state of no motion when the vehicle <NUM> is stationary or a state of motion when the vehicle is moving.

Another example determination made by the processor <NUM> in at least some circumstances is a cause of vehicle motion when there is movement of the vehicle <NUM>. For example, even though the vehicle <NUM> is not being driven, a wind gust may shake or push the vehicle <NUM> in a way that causes temporary movement of at least the vehicle body. The processor <NUM> is programmed or otherwise configured to determine when wind is a cause of such vehicle motion based on at least the indications from the BPSs.

One example way in which the processor <NUM> determines whether wind or air movement is a cause of vehicle motion is by determining a relationship between the indications from the BPSs <NUM>-<NUM>. For example, when there is a difference in the pressure detected by BPSs on oppositely facing sides of the vehicle <NUM> that exceeds a predetermined threshold, the processor <NUM> interprets such a difference as an indicator that wind near the vehicle <NUM> is strong enough to at least potentially be the cause of vehicle motion. The processor <NUM> may use additional information, such as an indication from the IMU <NUM>, to determine whether vehicle motion was the result of wind.

Another example determination made by the processor <NUM> in at least some circumstances is a direction of air movement relative to the vehicle <NUM>. For example, when the vehicle <NUM> is traveling forward, there will be wind resistance in a front-to-rear direction. Similarly, when a wind gust blows toward the front of the vehicle, even if the vehicle is stationary, the direction of air movement relative to the vehicle <NUM> is in a front-to-rear direction.

The processor <NUM> determines the direction of air movement relative to the vehicle <NUM> based on a relationship between the indications from at least two of the BPSs <NUM>-<NUM>. For example, when the indication from the first BPS <NUM> indicates a larger change in pressure than the indication from the second BPS <NUM>, the processor <NUM> determines that air movement relative to the vehicle <NUM> is from the front of the vehicle <NUM> toward the rear.

With the BPSs <NUM>-<NUM> in the illustrated arrangement on the example vehicle <NUM>, the processor <NUM> may determine a direction of air movement with more precision than simply front-to-rear or side-to-side. For example, when the pressure indication from the first BPS <NUM> is greater than the pressure indication from the second BPS <NUM> and the pressure indication from the third BPS <NUM> is greater than the pressure indication from the fourth BPS <NUM>, the processor <NUM> determines that the wind is approaching the vehicle from the left-front of the vehicle <NUM>, which corresponds to the top-right in the drawing.

In some embodiments, the processor <NUM> determines an angle at which the wind approaches the vehicle <NUM>. The processor <NUM> in some example embodiments is programmed or otherwise configured to determine the angle of the wind from the following relationship: Tan-<NUM>((BPS28-BPS30)/BPS24-BPS26)), where BPSi represents the pressure indicated by the BPS having the reference number i in <FIG>. This provides a clockwise positive angle (according to the illustration) of wind direction relative to the vehicle <NUM>.

The determination regarding vehicle motion made by the processor <NUM> is useful for a variety of purposes. One example use is to interpret or enhance the processing of information provided by a vehicle motion sensor, such as the IMU <NUM>. Another example use is to determine when conditions are appropriate to calibrate a vehicle motion sensor.

One example use of the determination regarding vehicle motion based on the BPS indications for interpreting the output from the IMU <NUM> is summarized in the flowchart <NUM> of <FIG>. At <NUM>, the processor <NUM> determines the direction of air movement relative to the vehicle <NUM> based on the indications from at least two of the BPSs. In this example, at least three BPS indications are used to determine the direction of air movement. The processor <NUM> uses a relationship between the respective BPS indications, such as one of the relationships mentioned above, to determine the direction of air movement.

At <NUM>, the vehicle motion sensor <NUM> detects vehicle motion and provides an indication of the detected vehicle motion to the processor <NUM>. In this example, the processor <NUM> determines a direction of vehicle movement based on the indication from the IMU <NUM>. At <NUM>, the processor <NUM> determines how to interpret the indication from the vehicle motion sensor based on a relationship between the direction of air movement and the determined direction of vehicle movement. Interpreting the output of the IMU <NUM> may include verifying or corroborating the determined direction of vehicle movement. Another interpretation includes determining whether the vehicle movement resulted from air movement relative to the vehicle <NUM> or another force, such as the engine of the vehicle being used to drive the vehicle.

For example, the relationship between the directions of air movement and vehicle movement may indicate that the vehicle is in motion and, in that case, relative movement between the vehicle <NUM> and the nearby air is at least partially due to the vehicle traveling along a driving surface. The BSPs will detect the pressure associated with natural wind resistance as the vehicle is in motion.

When the vehicle <NUM> begins to move from rest, the processor <NUM> determines that the difference in the BPS indications from the first BPS <NUM> and the second BPS <NUM> corresponds to air movement in a front-to-rear direction relative to the vehicle <NUM>. At the same time, the output from the gyroscope of the IMU <NUM> will initially indicate a tilt backward. A short time after the initial acceleration from rest, the accelerometer of the IMU <NUM> will indicate forward movement of the vehicle <NUM>. Under such conditions, the processor <NUM> determines that the direction of air movement and the direction of vehicle movement are consistent with each other and both correspond to forward movement of the vehicle <NUM>. The processor <NUM> interprets the indication from the IMU <NUM> in this instance based on the indications from the BPSs to confirm that the IMU indication is a result of movement of the vehicle <NUM> in a forward direction.

Sometimes an indication from the IMU <NUM> may result from movement of the vehicle that was caused by wind. The processor <NUM> interprets the indication from the IMU <NUM> based on the relationship between the determined directions at <NUM> in <FIG> to recognize such a situation. For example, when the direction of air movement determined at <NUM> is in a front-to-rear direction and the direction of vehicle movement determined at <NUM> is rearward, the processor <NUM> determines that such vehicle movement is a result of wind against the vehicle <NUM>.

When wind approaches the vehicle <NUM> from the front, the wind may push the vehicle body and rock it backward enough to cause the IMU <NUM> to indicate rearward movement of the vehicle <NUM>. The gyroscope tilt at that time will be backward and the accelerometer will indicate a rearward acceleration. The processor <NUM> interprets such an output from the IMU <NUM> based on the indications of the BPSs and, in particular in this example, based on the determined direction of air movement. When the indication from the IMU <NUM> is consistent with vehicle movement that corresponds to or is consistent with the direction of air movement, the processor <NUM> interprets the indication from the IMU and determines that the indication was the result of wind moving the vehicle <NUM>.

Windy conditions may cause some vehicle movement while the vehicle <NUM> is otherwise stationary or in motion. Wind against the side of the vehicle <NUM>, if strong enough, could cause a lateral acceleration. The processor <NUM> is able to interpret the indication of such a a lateral acceleration as a result of the wind based on corresponding wind direction information from the BPSs <NUM> and <NUM>, for example.

One way in which the output or indication of the IMU <NUM> is used in the illustrated example embodiment of <FIG> is to control activation of a vehicle alarm <NUM>. The processor <NUM> uses an indication of vehicle movement from rest from the IMU <NUM> as a wake up signal to trigger the alarm <NUM>. If a potential vehicle thief or intruder causes movement of the vehicle <NUM>, the alarm <NUM> will be triggered based on the corresponding indication of the IMU <NUM>.

There are situations in which the IMU <NUM> indicates vehicle movement resulting from wind and, in those situations, it would be beneficial to not activate the alarm <NUM>. The processor <NUM> uses the determinations in <FIG> to interpret an indication from the IMU <NUM> to determine if it should be treated as a wake-up, alarm-triggering signal or if it can be dismissed as the result of wind. When the direction of detected wind and the direction of detected vehicle movement correspond sufficiently, the processor interprets the IMU indication as a result of wind. When the directions of the detected wind and the detected vehicle movement do not correspond, the processor <NUM> interprets the IMU indication as an alarm triggering signal and activates the alarm <NUM>. Similarly, if the BPSs do not indicate any wind at a time corresponding to an IMU indication of vehicle movement from rest, the processor <NUM> interprets the IMU indication as wake up signal to activate the alarm.

Another example use of the information regarding vehicle movement determined by the processor <NUM> based on indications from the BPSs is calibrating or confirming operation of a vehicle motion sensor such as the IMU <NUM>. For example, commercially available IMUs are prone to gyroscopic and accelerometer drift that renders the devices unreliable for untethered dead reckoning. Using the indications from the BPSs allows for confirming that the vehicle <NUM> is stationary, which is useful when performing a zero velocity update of the IMU gyroscope to strip off static errors.

In an example embodiment, the processor <NUM> determines that the vehicle is stationary as a prerequisite to performing a gyroscope update. The indications from the BPSs have to correspond to the vehicle being at rest before the processor <NUM> will perform the update and remove accumulated drift error from the gyroscope output. The determination that the vehicle <NUM> is stationary is based on the processor <NUM> determining that any difference between the pressures indicated by the BPSs on opposite sides of the vehicle is within a predetermined range or zero. When such conditions exist, the vehicle <NUM> is not moving because movement of the vehicle results in pressure differentials as the vehicle pushes through the air.

In some embodiments, the processor <NUM> can accept some limited movement of the vehicle during a sensor calibration or update when such movement is consistent with wind moving the vehicle. For example, when the wind direction and the limited vehicle movement are in the same direction, it may be possible to properly perform a calibration or sensor update.

In some embodiments, the processor <NUM> will only perform a process, such as a zero velocity update of an IMU or activate a vehicle alarm, when the processor <NUM> determines that there is no wind. If the processor <NUM> determines that it is windy based on the indications from the BPSs, the processor in some embodiments will not perform a vehicle motion sensor calibration or update and will not activate the alarm <NUM>.

Wheel tick sensors are another type of vehicle motion sensor that can be calibrated or verified using indications from the BPSs. Some wheel tick sensors may have a dead zone in which the sensor indicates no movement at a low speed. By determining that the vehicle is stationary based on the indications from the BPSs, the processor <NUM> can determine whether a wheel tick sensor is providing an accurate output. If necessary, the sensor can be updated or calibrated.

Since the BPSs in some embodiments are sensitive to changes in atmospheric pressure associated with weather conditions, the processor <NUM> in at least some embodiments monitors pressure changes indicated by the BPSs over time. When a change occurs at a rate that corresponds more closely to a local change in atmospheric pressure than vehicle movement or wind, the change in pressure is ignored or filtered out by the processor <NUM>. A range for the rate of change that is suitable to discern between atmospheric pressure indications and relative movement between the vehicle <NUM> and the air can be determined to meet the needs of a particular implementation.

Another way that the processor <NUM> in this example embodiment determines whether a change in pressure indicated by the BPSs is based on the local atmospheric pressure conditions is by comparing the differences between the indications from the BPSs. When oppositely facing BPSs indicate the same change in pressure, that corresponds to an atmospheric pressure change. On the other hand, a significant enough difference between oppositely facing BPSs corresponds to wind or vehicle movement.

Using BPS indications in a manner like those described above facilitates making determinations regarding vehicle motion and is useful for more accurately interpreting vehicle motion sensor information. Additionally, the BPS indications allow for improved vehicle motion sensor calibration.

While a variety of features are described separately from each other, those features are not necessarily separate in embodiments consistent with this disclosure. Various combinations of such features are possible to realize other embodiments or additional functions of the vehicle sensor system <NUM> or processor <NUM>.

Claim 1:
A vehicle sensor system (<NUM>), comprising:
a plurality of barometric pressure sensors (<NUM>, <NUM>, <NUM>, <NUM>) including a first barometric pressure sensor (<NUM>) situated on a first portion of the vehicle (<NUM>) that faces at least partially in a first direction and a second barometric pressure sensor (<NUM>) situated on a second portion of the vehicle (<NUM>) that faces at least partially in a second direction that is different than the first direction; and
a vehicle motion sensor (<NUM>) supported on the vehicle (<NUM>) and configured to provide an indication of vehicle motion;
the vehicle sensor system (<NUM>) comprising: a processor (<NUM>) configured to:
make a determination regarding the vehicle motion based on respective indications from the plurality of barometric pressure sensors (<NUM>, <NUM>, <NUM>, <NUM>),
the processor being characterized in that it is further configured to:
use the determination based on the indications from the barometric pressure sensors (<NUM>, <NUM>, <NUM>, <NUM>) to interpret the indication from the vehicle motion sensor (<NUM>),
determine whether the indication from the vehicle motion sensor (<NUM>) is a result of movement of air near the vehicle (<NUM>),
determine that the vehicle (<NUM>) is in motion independent of movement of the air when the indications from the vehicle motion sensor (<NUM>) and the plurality of barometric pressure sensors (<NUM>, <NUM>, <NUM><NUM>) correspond to movement of the vehicle (<NUM>) in a direction that is opposite to a direction of the movement of the air, and
determine that movement of the vehicle (<NUM>) is a result of movement of the air when the indications from the vehicle motion sensor (<NUM>) and the plurality of barometric pressure sensors (<NUM>, <NUM>, <NUM><NUM>) correspond to movement of the vehicle (<NUM>) in a direction that is the same as the direction of movement of the air.