Patent Description:
For example, some aircraft have airfoils equipped with differential-pressure sensors configured to measure a differential pressure on opposite sides of the airfoil. Such a differential-pressure sensor can generate a signal indicative of steady-state wind or gusts normal to the airfoil. Such information can be used for various flight control operations. Should such a differential-pressure sensor be compromised, the particular system to which the differential-pressure sensor pertains can also be compromised. Therefore, verification of correct operation of these and other physical-parameter sensors could be helpful. <CIT> relates to a differential pressure sensing bridge configuration.

Apparatus and associated methods relate to a system for sensing a physical parameter for verifying correct operation of the system. The system includes a sensing device, a biasing network and a verification module. The sensing device includes four resistive elements configured in a Wheatstone bridge configuration having two biasing nodes and two sensing nodes. At least one of the four resistive elements includes a sensing transducer having a resistance that varies in response to variations of a parameter value of the physical parameter. The biasing network is configured to selectively provide first and second biasing conditions to the sensing device via the first and second biasing nodes. The verification module is configured to verify correct operation of the system based on a consistency determination of first and second output electrical signals generated at the two sensing nodes of the Wheatstone bridge in response to the first and second biasing conditions, respectively, selectively provided to the sensing device. The first and second output electrical signals are indicative of the parameter value of the physical parameter.

Some embodiments relate to a method for sensing a physical parameter and for verifying correct operation of a system used for sensing the physical parameter. The method includes sensing a physical parameter via a sensing device including four resistive elements configured in a Wheatstone bridge configuration having two biasing nodes and two sensing nodes, at least one of the four resistive elements comprising a sensing transducer having a resistance that varies in response to variations of a parameter value of the physical parameter. The method includes selectively providing, via a biasing network, first and second biasing conditions to the sensing device via the first and second biasing nodes. The method includes determining consistency of first and second output electrical signals generated at the two sensing nodes of the Wheatstone bridge in response to the first and second biasing conditions, respectively, selectively provided to the sensing device, the first and second output electrical signals indicative of the parameter value of the physical parameter. The method also includes verifying, via a verification module, correct operation of the system based on the consistency determined.

Apparatus and associated methods relate to sensing a physical parameter and verifying correct operation of a system used to sense the physical parameter. A sensing device includes four resistive elements configured in a Wheatstone bridge configuration is configured to sense the physical parameter. A biasing network selectively provides first and second biasing conditions to the sensing device. First and second output electrical signals are generated by the sensing device in response to the first and second biasing conditions, respectively, selectively provided to the sensing device. The first and second output electrical signals are each indicative of the parameter value of the physical parameter, but not necessarily equal to one another. A verification module verifies correct operation of the system based on a consistency determination of first and second output electrical signals.

<FIG> are a perspective view of an aircraft that has a yaw-control system and a block diagram of the yaw control system, respectively. In <FIG>, aircraft <NUM> includes yaw-control system <NUM>, which is depicted in greater detail in <FIG>. Yaw-control system <NUM> controls yaw of aircraft <NUM> by controlling orientation of rudder <NUM>, based on a signal indicative of differential pressure on opposite sides of vertical stabilizer <NUM> and or rudder <NUM>. Vertical stabilizer <NUM> functions to provide directional stability to the aircraft. Rudder <NUM> helps accomplish this task by laterally deflecting the airflow so as to change yaw (i.e., rotation in the x-y plane) of the aircraft. Yaw-control system <NUM> includes controller <NUM>, yaw actuator <NUM>, and system <NUM> for sensing differential pressure. Yaw-control system <NUM> can either control rudder <NUM> or augment pilot-control of rudder <NUM> in response to signals generated by system <NUM> for sensing differential pressure. For example, in one embodiment, yaw-control system <NUM> can be configured to provide high-frequency control of rudder <NUM> in response to a non-steady-state component (e.g., a high-frequency component) of a signal indicative of differential pressure generated by system <NUM> for sensing differential pressure.

System <NUM> for sensing differential pressure includes sensing device <NUM>, biasing network <NUM> and verification module <NUM>. In the embodiment depicted in <FIG>, sensing device <NUM> is a differential-pressure sensor coupled to vertical stabilizer <NUM> in such a manner that permits sensing of differential pressure on opposite sides of vertical stabilizer <NUM> (and/or, e.g., rudder <NUM>). Biasing network <NUM> is configured to selectively provide two different biasing conditions - first and second biasing conditions - to sensing device <NUM>. Verification module <NUM> can verify correct operation by comparing first output electrical signal to second output electrical signal. The underlying idea is to use first and second biasing conditions that will cause first and second output electrical signals that are both different from one another, and indicative of correct operation by a simple relational test to one another. In some embodiments, verification module <NUM> can control biasing network <NUM>. In other embodiments, a separate controller can coordinate operations of biasing network <NUM> and verification module <NUM>, such that verification of correct operation of sensing device <NUM> can be determined.

<FIG> is a block diagram of a system for sensing a physical parameter that provides verification of correct operation. In <FIG>, system <NUM> for sensing a physical parameter includes sensing device <NUM>, biasing network <NUM> verification module <NUM> and parameter calculator <NUM>. Sensing device <NUM> is configured to generate an output electrical signal indicative of a sensed parameter, for example differential pressures as described above with reference to <FIG>. The sensed differential pressure can indicate a steady-state pressure difference and/or a non-steady-state pressure difference across vertical stabilizer <NUM>. Sensing device <NUM> includes four resistive elements 32A-32D configured in a Wheatstone bridge configuration having two biasing nodes <NUM>+ and <NUM>- and two sensing nodes <NUM>+ and <NUM>-. At least one of the four resistive elements 32A-32D include a sensing transducer - 32A in the depicted embodiment - having a resistance that varies in response to variations of a parameter value (i.e., differential pressure across vertical stabilizer <NUM> in the <FIG> embodiment) of the physical parameter. In some embodiments two, three, or all four of the four resistive elements 32A-32D can include a sensing transducer.

Sensing device <NUM> is selectively provided biasing signals corresponding to the first biasing condition or the second biasing condition from biasing network <NUM>. Sensing device <NUM> has two sensing nodes <NUM>+ and <NUM>-, upon which are generated the output electrical signal of sensing device <NUM>. Sensing device <NUM> is configured as a Wheatstone bridge, having four interconnected resistive legs 32A-32D. Sensing device <NUM> has two biasing nodes <NUM>+ and <NUM>-, which receive biasing signals corresponding to the first and second biasing conditions. At least one of the interconnected resistive legs 32A-32D has a resistance that is temperature dependent. Thus, resistance of sensing device <NUM>, as measured between biasing nodes <NUM>+ and <NUM>- varies in response to variations of temperature. Such temperature dependent resistance between biasing nodes <NUM>+ and <NUM>- can be used to generate a signal indicative of temperature. For example, voltage of biasing node <NUM>- can be indicative of temperature, when biasing node <NUM>+ and <NUM>- are connected to and provided a biasing signal from biasing network <NUM>.

Biasing network <NUM> is configured to selectively provide two different biasing conditions - first and second biasing conditions - to sensing device <NUM>. First and second biasing conditions are provided to sensing device <NUM> via the first and second biasing nodes <NUM>+ and <NUM>-. First and second output electrical signals are generated at sensing nodes <NUM>+ and <NUM>-. First and second output electrical signals are generated in response to first and second biasing conditions, respectively. First and second biasing conditions are configured to bias sensing device <NUM> such that first and second output electrical signals are related to one another in a manner that can be used to determine whether sensing device <NUM> is operating correctly. For example, in some embodiments, first and second biasing conditions are configured to result in first and second output electrical signals being with a predetermined offset range from one another. First output electrical signal might be <NUM> Volts higher than second output electrical signal +/- <NUM> Volts, for example. If first output electrical signal is within such an offset range - between <NUM> and <NUM> Volts - above second output electrical signal, then sensing device <NUM> is operating correctly. If, however, first and second output electrical signals are not related in such a fashion, then correct operation is not verified.

In some embodiments, first and second biasing conditions are first and second currents conditions. In other embodiments, first and second biasing conditions are first and second voltage conditions. In still other embodiments, first and second biasing conditions are first and second Thevenin series resistance conditions or first and second Norton parallel resistance conditions. For example, in a specific embodiment depicted in <FIG>, a voltage supply (e.g., <NUM> Volts DC) can be connected to first biasing node <NUM>+, and second biasing node <NUM>- can be connected to a ground reference via first and second biasing resistors 38A and 38B, thereby forming first and second Thevenin series resistance conditions.

Verification module <NUM> can verify correct operation by comparing first output electrical signal to second output electrical signal. The underlying idea is to use first and second biasing conditions that will cause first and second output electrical signals that are both different from one another, and indicative of correct operation by a simple relational test to one another. In some embodiments, verification module <NUM> can control biasing network <NUM>. In other embodiments, a separate controller can coordinate operations of biasing network <NUM> and verification module <NUM>, such that verification of correct operation of sensing device <NUM> can be determined.

In the depicted embodiment, verification module <NUM> is in electrical communication with sensing module <NUM> and/or biasing network <NUM> so as to receive output electrical signals and/or temperature signal therefrom. For example, verification module <NUM> can be electrically connected to sensing nodes <NUM>+ and <NUM>- so as to receive output electrical signals provided thereby. Verification module <NUM> can be connected to biasing node <NUM>- and/or biasing node <NUM>+, so as to receive a signal indicative of temperature provided thereby. To verify correct operation, verification module <NUM> can compare either output electrical signals indicative of sensed parameter values and/or temperature signals generated using two or more biasing conditions. In some embodiments, first and second output electrical signals corresponding to first and second biasing conditions, respectively, can be compared so as to verify correct operation of sensing device <NUM>. In some embodiments, first and second temperature signals corresponding to first and second biasing conditions, respectively, can be compared so as to verify correct operation of sensing device <NUM>.

Parameter calculator <NUM> is configured to receive output electrical signals from sensing nodes <NUM>+ and <NUM>-, as well as temperature signals from biasing node <NUM>-. Parameter calculator is configured to calculate a parameter value of the physical parameter based on the output electrical signals and the temperature signals. In some embodiments, parameter calculator will calculate the parameter value of the physical parameter by adding an offset factor to a product of the output electrical signal and a linear factor. In the depicted embodiment, the linear factor and the offset factor are retrieved from table <NUM>, which is indexed by temperature. Thus, temperature is first calculated based on the temperature signal. Then parameter calculator <NUM> retrieves the linear factor and the offset factor corresponding to the temperature calculated (or the temperature signal). Then, parameter calculator calculates the parameter value using the linear and offset factors retrieved. In other embodiments, other mathematical operations can be used to calculate the parameter value.

<FIG> is a graph demonstrating data collected during calibration of a system for sensing a physical parameter that provides verification of correct operation. In <FIG>, graph <NUM> depicts the data collection of the output electrical signal in response to varying temperature at a particular physical parameter (e.g., a pressure differential) that is incident on the sensing device. Graph <NUM> also depicts a measurement of the temperature signal of the sensing device. These data are plotted on the graph for both the first and second biasing conditions described above.

Such a graph can be used to collect data for determining the operating range of the sensing device. The output electrical signal, in this case a voltage differential, and temperature signal are determined as a function of temperature for each biasing condition. The values of these measurements in the graph can be used in a lookup table with or without correction, such as, for example, linear correction using linear gain factor and offset value coefficients. The same can be done for the second biasing condition to produce a corrected output. The result of the second biasing condition output should be within an expected offset range of the first biasing condition output if the sensing device is functioning correctly. If the second biasing condition output is not within the expected offset range of the first biasing condition output, then the sensing device is can be deemed as not functioning correctly. The verification of correct operation can be done via the verification module. Graph <NUM>, with all the temperature data available, can provide the operating range of the sensing device.

<FIG> is a flow chart detailing the steps of an exemplary method of verifying correct operation of a physical parameter sensor. Method <NUM> begins at step <NUM> where the physical parameter is sensed by the sensing device. Then, at step <NUM>, the first biasing condition is applied via the biasing network to the sensing device. Next, at step <NUM>, the output electrical signal measurements at the output sensing nodes of the sensing device are made while the first biasing condition is applied. A measurement is also made at the temperature sensing node. Then, at step <NUM>, the second biasing condition is applied to the sensing device via the biasing network. Next, at step <NUM>, output electrical signal measurements are again obtained at the output sensing nodes of the sensing device and at the temperature measurement node. Next, at step <NUM>, the measurement information obtained from both of the biasing conditions is sent to the verification module. The verification module makes a final determination about sensor operation based on a consistency determination between first and second output measurements. It either outputs valid condition <NUM> or invalid condition <NUM>.

The system of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:.

A further embodiment of the foregoing system, wherein the verification module can determine that the first and second output electrical signals are consistent with one another when a difference between the first and second output electrical signals is within a consistency range.

A further embodiment of any of the foregoing systems, wherein the consistency range can include a range of +/- a predetermined delta of a predetermined offset.

A further embodiment of any of the foregoing systems, wherein the verification can be further configured to determine incorrect operation based on an inconsistency determination of first and second output electrical signals generated at the two sensing nodes of the Wheatstone in response to the first and second biasing conditions, respectively, selectively provided to the sensing device.

A further embodiment of any of the foregoing systems, wherein the verification module can determine that the first and second output electrical signals are inconsistent with one another when a difference between the first and second output electrical signals is not within a consistency range.

A further embodiment of any of the foregoing systems can further include a parameter calculator configured to calculate the parameter value of the physical parameter by adding a first offset factor to a product of the first output electrical signal and a first linear factor.

A further embodiment of any of the foregoing systems, wherein the first linear factor and the first offset factor can be retrieved from a table indexed by temperature.

A further embodiment of any of the foregoing systems, wherein the parameter calculator can be further configured to calculate the parameter value of the physical parameter by adding a second offset factor to a product of the second output electrical signal and a second linear factor.

A further embodiment of any of the foregoing systems, wherein a device resistance of the sensing device, as measured between the two sensing nodes, can vary in response to variations in temperature.

A further embodiment of any of the foregoing systems, wherein the verification module can be further configured to generate first and second temperature signals indicative of temperature based on a voltage difference between either the two sensing nodes or across the biasing network in response to providing the sensing device with the first and second biasing conditions, respectively.

A further embodiment of any of the foregoing systems, wherein the physical parameter sensor can be configured to measure a differential pressure on opposite sides of an airfoil of an airplane.

A further embodiment of any of the foregoing systems, wherein the sensing transducer can be a piezoresistive strain gauge.

The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:.

A further embodiment of the foregoing method, wherein determining consistency can include comparing, via the verification module, a difference between the first and second output electrical signals with a consistency range.

A further embodiment of any of the foregoing methods, wherein the consistency range can include and range of +/- a predetermined delta of a predetermined offset.

A further embodiment of any of the foregoing methods can further include calculating, via a parameter calculator, the parameter value of the physical parameter by adding a first offset factor to a product of the first output electrical signal and a first linear factor.

A further embodiment of any of the foregoing methods can further include retrieving the first linear factor and the first offset factor from a table indexed by temperature.

A further embodiment of any of the foregoing methods can further include retrieving the second linear factor and the second offset factor from a table indexed by temperature.

A further embodiment of any of the foregoing methods, wherein the physical parameter sensor can be configured to measure a differential pressure on opposite sides of an airfoil of an airplane.

A further embodiment of any of the foregoing methods, wherein a device resistance of the sensing device, as measured between the two sensing nodes, can vary in response to variations in temperature. The method can further include generating, via the verification module, first and second temperature signals indicative of temperature based on a voltage difference between either the two sensing nodes or across the biasing network in response to providing the sensing device with the first and second biasing conditions, respectively.

Claim 1:
A system (<NUM>) for sensing a differential pressure and for verifying correct operation of the system, the system comprising:
a differential-pressure sensor (<NUM>) including four resistive elements (32A-32D) configured in a Wheatstone bridge configuration having two biasing nodes (<NUM>+, <NUM>-) and two sensing nodes (<NUM>+, <NUM>-), at least one of the four resistive elements comprising a sensing transducer having a resistance that varies in response to variations of a parameter value of the differential pressure; characterized by
a biasing network (<NUM>) configured to selectively provide first and second biasing conditions to the differential-pressure sensor via the first and second biasing nodes, so as to bias the differential-pressure sensor in two different biasing conditions; and
a verification module (<NUM>) configured to verify correct operation of the system based on a consistency determination of first and second output electrical signals generated at the two sensing nodes of the Wheatstone bridge in response to the first and second biasing conditions, respectively, selectively provided to the differential-pressure sensor, the first and second output electrical signals indicative of the parameter value of the differential pressure.