State sensor systems and methods

Sensor systems comprising a magnetic circuit comprising a coil, a magnet, at least one of a ferromagnetic armature plate and a conductive armature plate, wherein the at least one of the ferromagnetic armature plate and the conductive armature plate is configured to move axially in response to at least one of the magnet and the coil, and a controller configured to apply a known first voltage across the coil and monitor a current through the coil are provided. Methods are also provided.

FIELD

The present disclosure relates to state sensor systems and methods for detecting a change in a property of a magnetic circuit, such as a bi-stable park brake in an electromechanical braking system.

BACKGROUND

Bi-stable electromechanical actuators may take one of two stable states and, thus, when subject to severe vibration or shock, may alter states when power is not supplied to the bi-stable brakes. In that regard, systems and methods for state determination may be beneficial.

SUMMARY

Sensor systems are provided comprising a magnetic circuit comprising a coil, a magnet, at least one of a ferromagnetic armature plate and a conductive armature plate, wherein the at least one of the ferromagnetic armature plate and the conductive armature plate is configured to move axially in response to at least one of the magnet and the coil, and a controller configured to apply a known first voltage across the coil and monitor a current through the coil.

Methods are also provided comprising applying a known first voltage via a controller coupled to a coil forming part of a magnetic circuit, wherein the magnetic circuit comprises a magnet and at least one of a ferromagnetic armature plate and a conductive armature plate configured to move axially, monitoring the known first voltage across the coil, monitoring a first current response through the coil, and determining a phase lag between the known first voltage and the first current response.

DETAILED DESCRIPTION

In various embodiments, a brake system may comprise an actuator, such as an electromechanical actuator (“EMA”). The EMA may be coupled to or otherwise operate a pressure generating device, such as, for example, a ball screw, a ram, and/or the like. In operation, the EMA may cause the pressure generating device to move and/or exert a force on other brake system structures, such as a brake disk or pad to exert a stopping force on a wheel or other suitable moving structure.

For example, with reference toFIG. 1, a perspective view of an EMA100is shown. The EMA may extend along the axis marked A-A′. The EMA100may, as described above, be involved in the application of a braking force to an aircraft wheel. The EMA100assembly may comprise an EMA housing102, which may extend along the axis A-A′. The EMA housing102may house a variety of components, including, for example, a ball nut104, a ball screw106, and a motor drive unit. Generally, the motor drive unit may drive the ball screw106through a plurality of rotations. As the ball screw106rotates, the ball nut104may translate distally and/or proximally along the axis A-A′ (depending upon the direction of rotation of the ball screw106). The ball nut104may be coupled to a disc or “puck,” at a distal end thereof. The puck may exert a pressure against a brake stack coupled to an aircraft wheel to impede or halt a rolling motion of the wheel. The EMA may include a bi-stable brake.

A brake may be used to prevent an EMA from rotating the ball screw in one state, while permitting rotation of the ball screw in a second state. For example, in a bi-stable brake, prevention of ball screw rotation may be advantageous in a parking brake mode. A bi-stable brake may be switched from one state to another vis-à-vis a friction brake assembly. The friction brake assembly may take a first configuration that prevents ball screw rotation (i.e., a “locked state”) and a second configuration that allows ball screw rotation (i.e., an “unlocked state”).

For example, with reference toFIG. 2,FIG. 2illustrates friction brake assembly200that forms part of a park brake feature of an EMA. In various embodiments, friction brake assembly200may be internal to an actuator, such as EMA100shown inFIG. 1. Friction brake assembly200may comprise a friction brake base110, a magnetic body120, pressure plate140, and an armature plate130configured to move axially along the A-A′ axis around motor shaft161contained within motor shaft housing160. In various embodiments, armature plate130may have various characteristics and functions, such as for example, armature plate130may be at least one of a ferromagnetic plate or a conductive plate. The friction brake assembly may be held together by screws150.

With reference toFIGS. 3A and 3B,FIG. 3Aillustrates the friction brake assembly200in the engaged state (the locked state) andFIG. 3Billustrates the friction brake assembly200in the disengaged (the unlocked state) in various embodiments. As demonstrated inFIG. 3A, when the brake assembly is in the engaged state, the armature plate130and the friction disk135may be held away from the magnetic body120coupled to friction brake base110, and may be retained against the pressure plate140by the force of springs155. Due to the clamping force at the pressure plate140, the motor shaft161, is prevented from rotating around the axis marked A-A′.

For example, to change the friction brake assembly from the engaged state to the disengaged state (e.g., fromFIG. 3AtoFIG. 3B), the magnetic body120may be polarized to overcome the spring force from springs155. In various embodiments, the spring may be the dominant force in the disengaged state and the magnets may be the dominant force in the engaged state. In various embodiments, the polarization of magnetic body120may draw the armature plate130and the friction disk135axially (e.g., along axis A-A′) to the magnetic body120coupled to friction brake base110, as illustrated inFIG. 3B. In various embodiments, the release of pressure between the pressure plate140and the friction disk135may allow the motor shaft161to rotate unrestricted about the axis marked A-A′.

With reference toFIG. 4,FIG. 4illustrates a cross-sectional view of an engaged bi-stable friction brake assembly in various embodiments.FIG. 4illustrates friction brake assembly200, with magnetic body120illustrated in further detail. In various embodiments, magnetic body120may comprise an inner pole390, an outer pole370, a coil pack380, and magnets121positioned concentrically around motor shaft161. Coil385may form part of a coil pack380in various embodiments. In various embodiments, the armature plate130may be configured to move axially (e.g., along axis A-A′) in response to at least one of the magnets121or the coil385. At times when the coil pack380does not polarize the magnetic body120, the armature plate130may force the friction disk135and the friction pads137along motor shaft housing160into contact with the pressure plate140due to the force of the springs155(illustrated above inFIG. 3A) and held together by screws150. In various embodiments, the relative positioning of the inner pole390, the outer pole370, the coil pack380, the magnets121, and the armature plate130may form a magnetic circuit, as described below.

Bi-stable brakes may transition or switch from one state to another, for example, when subject to large vibrations or shock, such as may occur during high levels of inflight turbulence. In various embodiments, sensor systems provided herein may be able to determine the state of a friction brake assembly by, for example, determining the axial position of armature plate130and, thus, determine the state of the friction brake assembly200. In various embodiments, the determination of the axial position of the armature plate130may be accomplished without changing the state of the friction brake assembly200.

FIG. 5illustrates a sensor system500comprising magnetic circuit450, magnets121, armature plate130, controller520, and coil385in various embodiments. In various embodiments, magnets121may be disposed between a first portion391of the inner pole390(e.g., forming second fixed air gap411) and a first portion371of the outer pole370(forming first fixed air gap410). Armature plate130may be disposed in axial proximity to a second portion392of the inner pole390and a second portion372of the outer pole370, forming part of the magnetic circuit450. In various embodiments, coil385may be configured to induce a magnetic field in magnetic circuit450. As illustrated inFIG. 5, in various embodiments, coil385may surround at least a part of inner pole390(e.g., coil385may surround second portion392of inner pole390). In various embodiments, coil385may be coupled to a controller520configured to apply a known first voltage across the coil385and monitor a current through the coil385.

In various embodiments, controller520may be configured to monitor a current through the coil385, for example by being coupled to sensor511. Moreover, in various embodiments, the controller520may be configured to detect a change in a current. For example, the controller520may be configured to detect a change in an eddy current. In various embodiments, sensor511may be configured to sense a change in a property of the magnetic circuit450(e.g., an inductive reactance). In various embodiments, sensor511may also be a current sensor configured to measure a current provided to the coil385according various embodiments.

For example, the sensor511may be configured to measure the phase lag of the circuit. As used herein, the term “phase lag” may include the delay between the time a voltage signal rises and the time a current signal rises. Thus, in various embodiments, the phase lag may be used to derive the inductive reactance of the magnetic circuit450. In various embodiments, it has been found that the phase lag may be used to determine the axial position of armature plate130of sensor system500. In various embodiments, the phase lag may be used to determine the axial height of dynamic gap430.

Signal generator510may be configured to provide a known first voltage at a first frequency to coil385in various embodiments. In various embodiments, signal generator510may also be configured to cause a known second voltage, wherein the known second voltage is at a frequency that is different from the known first voltage.

In various embodiments, a controller520may receive a signal from the sensor511and determine an axial position (e.g., the axial height of dynamic gap430) of the armature plate130. In various embodiments, the controller520may be configured to apply a known first voltage and/or a known second voltage, for example, controller520may be in electrical communication with the signal generator510. Moreover, in various embodiments, the sensor511and the signal generator510may comprise part of the controller520. In various embodiments, the controller520may form part of an actuator, such as EMA100illustrated inFIG. 1. Thus, in various embodiments, the controller520may be part of an electromechanical actuator controller (“EMAC”).

FIG. 6illustrates a method in accordance with various embodiments. Method600may comprise applying a known first voltage via a controller520coupled to a coil385forming part of a magnetic circuit450, as shown inFIG. 5(step610). In various embodiments, the nature of the known first voltage is not particularly limited. Further, in various embodiments, the methods of generating the known first voltage are not particularly limited and may, for example, include generating the known first voltage via a pulse-width modulator. The particular type of waveforms are not particularly limited and may include square, triangular, sinusoidal, trapezoidal, half-sine, exponential or other periodic waveforms. The frequency of the waveforms is not particularly limited and may vary, for example due to the inductance and resistance of the magnetic circuit. Exemplary frequencies, in various embodiments, include frequencies between about 500 Hz and about 15 kHz, about 1 kHz and about 15 kHz, and about 1 kHz to about 10 kHz, where the term “about” in this context only may include±ten percent of the stated value (e.g., about 1 kHz may include 0.9 kHz).

As described above, in various embodiments the coil385may form part of a magnetic circuit450. In various embodiments, the magnetic circuit450may comprise an inner pole390, an outer pole370, magnets121, and an armature plate130configured to move axially. In various embodiments, the magnetic circuit450may also comprise a controller520configured to apply a known first voltage across the coil385and monitor a current through the coil385. In various embodiments, the controller520may be configured to sense a change in a property of the magnetic circuit450(e.g., an inductive reactance), wherein the coil385is configured to induce a magnetic field in the magnetic circuit450.

After the known first voltage is applied (step610), the known first voltage may be monitored across the coil385shown inFIG. 5(step615). In various embodiments, a current response may be monitored (step620). The phase lag between the known first voltage and the first current response may then be determined in various embodiments (step630). In various embodiments, the determination of the phase lag between the known first voltage and the first current response (step630) may comprise detecting a change in an eddy current (Foucault current) induced by the moving parts (e.g., the armature plate of a brake assembly). In various embodiments, the armature plate may be at least one of a ferromagnetic armature plate or a conductive armature plate. In various embodiments, the change in eddy currents may be monitored by applying a known voltage to the coil385(shown inFIG. 5) of at least one of insufficient duration and intensity to cause a state change in a brake assembly (e.g., from locked to unlocked).

In various embodiments, applying a known voltage to the coil385may not be of sufficient duration and intensity to cause a brake assembly in an unstable equilibrium (e.g., a partially-engaged state) to change to a stable state (e.g., to a disengaged state or to an engaged state). In that regard, determination of state may still achieved without effecting a change in state. In various embodiments, however, applying a known voltage to the coil385may be of sufficient duration and intensity to cause a brake assembly in an unstable equilibrium (e.g., a partially-engaged state) to change to a stable state (e.g., to a disengaged state or to an engaged state). In various embodiments, this may help to ensure that the reported state of a brake assembly is accurate (e.g., prevent a partially-engaged state from being reported as disengaged). Thus, in various embodiments, applying a known voltage to the coil385may be of insufficient duration and intensity to cause a brake assembly to change from one stable state to another stable state (e.g., from unlocked to locked), but may be of sufficient duration and intensity to cause a brake assembly to change from an unstable equilibrium to change to a stable state (e.g., from a partially-engaged state to an engaged state).

With reference toFIG. 7,FIG. 7illustrates a method for determining an inductive reactance based on a phase lag in accordance with various embodiments. Method700may comprise applying a known first voltage via a controller520coupled to a coil385forming part of a magnetic circuit450, as shown inFIG. 5(step610). In various embodiments, the known first voltage may then be monitored (step615) and the first current response may then be measured (step620). In various embodiments, the phase lag between the known first voltage and the first current response may then be determined (step630). Then, in various embodiments, an inductive reactance based on the phase lag may be determined (step740).

With reference toFIG. 8,FIG. 8illustrates a method for determining the state of friction brake assembly200in various embodiments. Method800may comprise applying a known first voltage via a controller520to a coil385forming part of a magnetic circuit450, as shown inFIG. 5(step610). In various embodiments, the known first voltage across the coil385may be monitored (step615) and a first current response may then be monitored (step620), for example, with sensor511(shown inFIG. 5). In various embodiments, a phase lag between the known first voltage and the first current response may then be determined (step630). In various embodiments, a state of friction brake assembly200may then be determined (step840) (e.g., based on the determined phase lag, inductance, etc.). In various embodiments, the state of friction brake assembly200(shown inFIG. 2) may then be sent to a controller520(shown inFIG. 5), such as an EMAC.

For example, Table 1 below contains exemplary data in various embodiments. The exemplary data was obtained from exemplary friction brake assemblies to illustrate the change in inductive reactance between two different frequencies in various embodiments.

First, a 1 kHz sinusoidal excitation frequency signal (e.g., a known first voltage) was sent by a signal generator. Using a sensor configured to sense a change in a property of the magnetic circuit of the brake assembly, the friction brake inductance was then determined for both brake assemblies A and B, in both the engaged and disengaged state.

Then a 10 kHz sinusoidal excitation frequency signal (e.g., a known second voltage) was sent by a signal generator. Using the sensor configured to sense a change in a property of the magnetic circuit of the brake assembly, the friction brake inductance was then determined for both brake assemblies A and B, in both the engaged and disengaged state. The results observed and recorded are reflected in Table 1 below.

As evidenced by Table 1, the difference in inductance was greater than 20% for both the engaged and disengaged states for a 1 kHz sinusoidal excitation frequency signal. This was determined to be a detectable level, capable of indicating the state of the brake assembly to a controller, for example, to an EMAC.

Moreover, as also evidenced by Table 1, the difference in inductance was greater than 13% for both the engaged and disengaged states for a 10 kHz sinusoidal excitation frequency signal. This is also a detectable level, capable of indicating the state of the brake assembly to a controller, for example, to an EMAC.

Furthermore, in various embodiments, the inductive component of the reactance can be isolated by taking data at multiple significantly different frequencies (e.g., by an order of magnitude of about one). This may help eliminate the need for a temperature measurement of the circuit, because although resistance is temperature dependent, the inductive reactance may be isolated with the use of two different frequencies (e.g., a known first voltage and a known second voltage).