System for determining stack closing pressure of a brake stack

Abstract

System for determining a stack closing pressure of a brake stack. A brake system is disclosed. The brake system includes: a brake stack having a stack closing pressure; a force member positioned within a cylinder; a valve configured to control a fluid pressure of the brake system; and one or more pressure sensors that generate a proportional electrical signal representative of the fluid pressure within the cylinder. The brake system also includes one or more processors in electronic communication with the valve, the one or more pressure sensors, and a memory coupled to the one or more processors. The memory stores data including a database and program code that, when executed by the one or more processors, causes the brake system to determine the stack closing pressure of the brake stack.

Description

Technical Field

[0001] The present disclosure relates to a brake system and more particularly to a brake system that determines a stack closing pressure of a brake stack based on monitoring a fluid pressure of the brake system. Background Art

[0002] Aircraft brakes are used in a variety of situations. For example, aircraft brakes are used to slow an aircraft during landing along a runway. Aircraft brakes may also be used during ground handling operations such as taxiing, turning, and parking. Aircraft brakes typically include a brake stack having a series of rotating components (called rotors) that rotate with the wheels of the aircraft. The brake stack also includes a series of fixed components (called stators) that are interleaved with the rotors.

[0003] When the brake stack is compressed, friction is created between the rotor and the stator and a braking torque is generated. The braking torque causes the aircraft to slow down and eventually stop. It will be appreciated that the braking torque is only generated after the rotor and stator are compressed to a point where they are firmly in contact with each other, referred to as brake stack closure. Hydraulically actuated aircraft brakes require a minimum amount of hydraulic brake pressure to overcome the spring force applied to maintain the running clearance between the brake piston and the stator to generate the braking torque. The minimum amount of hydraulic brake pressure required to generate the braking torque is referred to as the stack closure pressure.

[0004] Sometimes, the hydraulic brake fluid of the aircraft brakes may be underfilled or overfilled. As a result, a rapid onset of braking torque causes an overshoot in aircraft deceleration. Conversely, underfilling results in an initial brake pressure that is too low. This results in a delay in the onset of braking, which is often accompanied by a pressure overshoot at the moment when the brake stack closure occurs. Summary of the invention

[0005] According to several aspects, a brake system having a brake stack having a stack closing pressure is disclosed. The brake system includes: a force member positioned within a cylinder; a valve configured to regulate fluid pressure in the brake system; and one or more pressure sensors that generate a proportional electrical signal representing the fluid pressure within the cylinder. The brake system also includes one or more processors in electronic communication with the valve and the one or more pressure sensors and a memory coupled to the one or more processors. The memory stores data including a database and program code, which when executed by the one or more processors causes the brake system to generate a valve command instructing the valve to increase the fluid pressure in the brake system, which causes the amount of brake fluid supplied to the cylinder to increase at a fixed rate. The brake system is also caused to monitor the output of the proportional electrical signal generated by the one or more pressure sensors. As the amount of brake fluid supplied to the cylinder increases at a fixed rate, the brake system is also caused to determine a derivative value of the output of the proportional electrical signal. The brake system is also caused to determine a transition point of the derivative value, wherein the transition point indicates when the derivative value exceeds approximately zero and increases to a positive value. Finally, the brake system is caused to select the fluid pressure at the transition point as the stack closing pressure of the brake system.

[0006] In another embodiment, an aircraft having a braking system is disclosed. The aircraft includes: a brake stack including one or more rotors interleaved with one or more stators; a force member positioned within a cylinder; a valve configured to regulate fluid pressure in the braking system; one or more pressure sensors generating a proportional electrical signal representing the fluid pressure within the cylinder; one or more processors in electronic communication with the valve and the one or more pressure sensors; and a memory coupled to the one or more processors. The memory stores data including a database and program code, which when executed by the one or more processors causes the braking system to generate a valve command instructing the valve to increase the fluid pressure in the braking system, which results in an increase in the amount of hydraulic brake fluid supplied to the cylinder at a fixed rate. The braking system is also caused to monitor the output of the proportional electrical signal generated by the one or more pressure sensors. As the amount of hydraulic brake fluid supplied to the cylinder increases at a fixed rate, the braking control system is also caused to determine a derivative value of the output of the proportional electrical signal. The braking control system is caused to determine a transition point of the derivative value, wherein the transition point indicates when the derivative value exceeds approximately zero and increases to a positive value. Finally, the brake control system is caused to select the fluid pressure at the transition point as the stack closing pressure of the brake system. The stack closing pressure represents the minimum amount of brake pressure required for the brake stack to generate a braking torque.

[0007] In another embodiment, a method for determining a stack closing pressure of a brake stack of a braking system is disclosed. The method includes: generating, by a computer, a valve command instructing a valve to increase the fluid pressure of the braking system, which causes the amount of brake fluid supplied to the cylinder to increase at a fixed rate. The force member is positioned within the cylinder, and the valve is configured to control the amount of brake fluid supplied to the cylinder. The method also includes: monitoring, by a computer, an output of a proportional electrical signal generated by one or more pressure sensors. The proportional electrical signal represents the fluid pressure within the cylinder. The method also includes: determining a derivative value of the output of the proportional electrical signal as the amount of brake fluid supplied to the cylinder increases at a fixed rate. The method also includes: determining a transition point of the derivative value, wherein the transition point indicates when the derivative value exceeds approximately zero and increases to a positive value. Finally, the method includes: selecting the fluid pressure at the transition point as the stack closing pressure of the braking system.

[0008] The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

[0010] Figure 1 is a schematic diagram of a vehicle including the disclosed braking system having a control module, a valve, a force member disposed within a cylinder, a brake stack, and a fluid reservoir according to an exemplary embodiment.

[0011] Figure 2 is a diagram showing determination according to an exemplary embodiment Figure 1 A graph showing the course of the stack closing pressure of a brake stack is shown.

[0012] Figure 3A is a diagram showing the execution of the Figure 2 The process shown is a graph of the fluid pressure of the brake fluid.

[0013] Figure 3B is a diagram showing the execution of the Figure 2 The process shown is a graph of the braking torque generated by the brake stack.

[0014] Figure 4 is a process flow diagram illustrating a method of determining brake stack closure according to an exemplary embodiment.

[0015] Figure 5A is a diagram showing a method for determining a signal based on amplitude attenuation according to an exemplary embodiment. Figure 1Graphs of alternative courses of stack closing pressure for brake stacks are shown.

[0016] Figure 5B is a diagram showing a method for determining a phase lag based on an exemplary embodiment. Figure 1 A graph of another course of the stack closing pressure of a brake stack is shown.

[0017] Figure 6 is a diagram showing a method based on an exemplary embodiment Figure 5A Process flow chart of an alternative method of determining brake stack closure based on the amplitude decay seen in FIG.

[0018] Figure 7 is a diagram showing a method based on an exemplary embodiment Figure 5B Flowchart of an alternative method of determining brake stack closure based on phase lag as seen in FIG.

[0019] Figure 8 According to an exemplary embodiment Figure 1 An illustration of a computer system used by a braking system. DETAILED DESCRIPTION

[0020] The present disclosure relates to a system and method for determining a stack closing pressure of a brake stack. The brake stack is part of a braking system for a vehicle. The stack closing pressure represents the minimum amount of brake pressure required to generate a braking torque, wherein the braking torque causes the vehicle to slow down or stop. The stack closing pressure is then used as an initial command pressure for the braking system. It will be appreciated that this initial command pressure can be used in an automatic braking control system. Setting the stack closing pressure to the initial command pressure for the braking system reduces the hysteresis that typically occurs in a conventional open-loop braking system when the brakes are initially applied. The stack closing pressure is recalculated over time to account for changes in the braking system, such as brake wear and any changes in the volume of brake fluid.

[0021] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0022] Reference Figure 1 , a schematic diagram of a vehicle 10 having a brake system 18 is shown. The brake system 18 includes a brake input 20, a control module 22, a valve 26, one or more pressure sensors 28, a force member 30, a brake thermal stack (referred to as a brake stack 32), and a fluid reservoir 34. The control module 22 is in electronic communication with the brake input 20, the valve 26, and the pressure sensor 28. The force member 30 is configured to translate back and forth within a cylinder 40 in a linear motion. Specifically, the force member 30 translates within the cylinder 40 in response to changes in fluid pressure within a pressurized chamber 48 of the cylinder 40, which is described in more detail below and shown in Figures 2 to 4 The brake system 18 also includes a high pressure conduit 42 fluidly connecting the fluid reservoir 34 to the valve 26 and a return conduit 44 fluidly connecting the pressurized chamber 48 of the cylinder 40 to the valve 26. The pressure sensor 28 monitors the fluid pressure within the cylinder 40, and more specifically, the fluid pressure of the pressurized chamber 48 within the cylinder 40.

[0023] The brake stack 32 includes one or more rotors 36 interleaved with one or more stators 38. Brake stack closed represents a state of the brake stack 32 in which the rotors 36 and stators 38 frictionally bear against each other and any further compression of the brake stack 32 produces a braking torque that restricts movement of the vehicle 10. As explained below, the control module 22 determines a stack closing pressure for the brake stack 32. The stack closing pressure represents the minimum amount of braking pressure required to generate a braking torque through the brake stack 32.

[0024] In one embodiment, the vehicle 10 is an aircraft and the brake system 18 uses hydraulic brake fluid to deliver hydraulic pressure to the brake stack 32. However, it will be understood that the vehicle 10 is not limited to aircraft. It will also be understood that although Figure 1 Only a single brake system 18 is shown, but the aircraft may actually include multiple brake systems 18. For example, the aircraft may include separate brake systems corresponding to the left and right wheels of the aircraft. Therefore, a separate stack closing pressure is determined for each separate brake system 18.

[0025] The disclosed brake system 18 is any brake system that includes dead space. Dead space represents the displacement experienced by the brake piston (i.e., force member 30) when a user initially applies force to the brake pedal, but the force is not transmitted to the brake stack 32. Therefore, the brake system 18 is not limited to a hydraulic system. For example, in an alternative embodiment, the brake system 18 can be a pneumatic-based brake system rather than a hydraulic brake system. Therefore, the brake fluid is a liquid or a gas.

[0026] In one embodiment, the brake input 20 is a brake pedal. The operator manually depresses the brake pedal to create an input command 50 received by the control module 22. The input command 50 represents the amount of braking requested by the braking system 18. Therefore, if a manual brake pedal is used, the operator uses the brake pedal to indicate the amount of braking requested by the braking system 18. Alternatively, instead of manual control, the input command 50 is generated by an automatic braking algorithm, where the automatic braking instructions are stored in the memory 1034 of the control module 22 (the memory 1034 is shown in FIG. Figure 7 middle).

[0027] In response to receiving the input command 50 from the brake input 20, the control module 22 determines the valve command 52. Specifically, the control module 22 determines the valve command 52 based on the input command 50 from the brake input 20. The valve command 52 may also be determined based on a plurality of other brake commands 54. Some examples of other brake commands 54 include, but are not limited to, automatic braking, gear retraction braking, or parking braking. For example, if an automatic braking algorithm is employed, the automatic braking command generates the input command 50, wherein the input command 50 represents the amount of braking requested by the brake system 18. The control module 22 then determines the valve command 52 based at least on the input command 50. The valve command 52 is sent to the valve 26, wherein the valve 26 is configured to adjust the fluid pressure in the brake system 18. In response to receiving the valve command 52 from the control module 22, the valve 26 adjusts the amount of fluid pressure supplied to the brake system 18, which results in an increase in the amount of brake fluid contained in the pressurized chamber 48. Specifically, the valve 26 increases or decreases the amount of pressure supplied to the brake system 18.

[0028] The force member 30 may be a piston including an end 68. A biasing member 66 (e.g., a coil spring) may be disposed within the cylinder 40. The force member 30 overcomes the biasing force applied by the biasing member 66 to translate toward the brake stack 32 in the first direction D1. As the force member 30 translates in the first direction D1, the end 68 of the force member 30 eventually abuts against the brake stack 32 and applies a compressive force. For example, referring to Figure 1 and Figure 2 , actuation of valve 26 causes the amount of brake fluid supplied to cylinder 40 to increase until the fluid pressure in pressurizing chamber 48 is at least equal to the stack closing pressure (the stack closing pressure is Figure 2 Once the fluid pressure in the pressurizing chamber 48 is at least equal to the stack closing pressure, any additional brake fluid supplied to the pressurizing chamber 48 causes the end 68 of the force member 30 to further compress the brake stack 32. The force member 30 continues to compress the brake stack 32 until the fluid pressure in the pressurizing chamber 48 reaches a maximum pressure value 74 ( Figure 2 ). Thus, when the fluid pressure in the pressurized chamber 48 is at the maximum pressure value 74, the brake stack 32 ( Figure 1 ) is fully compressed.

[0029] The pressure sensor 28 generates a proportional electrical signal 58 representing the fluid pressure in the pressurized chamber 48 of the cylinder 40. The proportional electrical signal 58 is received by the control module 22. For example, in one non-limiting embodiment, the proportional electrical signal 58 is a current value in the range of about 4 mA to about 20 mA. Although current is described, it will be understood that the pressure sensor 28 may output other electrical signals instead. That is, the proportional electrical signal 58 is selected from a current value, a capacitance value, or a voltage value. For example, in one non-limiting embodiment, the valve 26 is a servo valve and the valve command 52 is a mA signal.

[0030] A method of determining the stack closing pressure of the brake stack 32 will now be described. Figure 2 is a graph 70 illustrating an exemplary process for determining stack closing pressure, wherein the x-axis represents the brake fluid compliance displacement within the pressurized chamber 48 of the cylinder 40 and the y-axis represents the fluid pressure measured by the pressure sensor 28. Figure 1 and Figure 2 In addition, the brake fluid compliance displacement represents the displacement of the force member 30 in the cylinder 40, wherein a positive displacement is a movement in the first direction D1 and a negative displacement is a movement in the second direction D2. Figure 2 As seen in FIG. 8 , the second direction D2 is opposite to the first direction D1 and is oriented in a direction away from the brake stack 32 .

[0031] The control module 22 generates a valve command 52 that instructs the valve 26 to increase the fluid pressure of the brake system 18 and causes the amount of brake fluid supplied to the cylinder 40 to increase at a fixed rate. The fixed rate represents a steady-state amount of brake fluid supplied to the cylinder 40. The graph 70 includes a line representing an output 72 of the proportional electrical signal 58 generated by the one or more pressure sensors 28. The output 72 is divided into two portions, namely, portion A and portion B. During portion A, the control module 22 instructs the valve 26 to increase the fluid pressure, which causes the amount of brake fluid supplied to the cylinder 40 to increase at a fixed rate. However, as Figure 2As seen in FIG. 1 , although the brake fluid compliance displacement along the y-axis increases, there is only a negligible increase in brake pressure. That is, the relationship between the hydraulic brake fluid compliance displacement and the fluid pressure has a derivative value (i.e., the slope of the line) of about zero. For the purposes of this disclosure, about zero may include positive fluid pressure values. For example, in an embodiment, any fluid pressure value less than about 300psi (2068 kilopascals) may be considered to be about zero. In one embodiment, the control module 22 filters the derivative value of the output 72 of the proportional electrical signal 58 below the threshold pressure value to about zero. The threshold pressure value represents a negligible change in the brake pressure that is negligible for detecting the stack closing pressure. That is, in response to determining that the derivative value of the output 72 of the proportional electrical signal 58 is lower than the threshold pressure value, the control module 22 sets the derivative value to about zero. For example, in one embodiment, the threshold pressure value is about 200 pounds per square inch (psi) (about 1379 kilopascals).

[0032] Portion A terminates at transition point C. Transition point C represents when the derivative value of the fluid pressure exceeds approximately zero and increases to a positive value. In an embodiment, the positive value is equal to or greater than approximately 300 psi. Transition point C represents the stack closing pressure of the brake system 18. As described above, the stack closing pressure represents the minimum amount of brake pressure required to generate braking torque through the brake stack 32.

[0033] It will be appreciated that although portions A and B of output 72 of proportional electrical signal 58 generated by pressure sensor(s) 28 include different derivative values, the rate at which brake fluid is supplied to cylinder 40 does not change. In other words, brake fluid continues to be supplied to cylinder 40 at a fixed rate.

[0034] In one embodiment, the control module 22 selects the fluid pressure at the transition point C as the stack closing pressure of the brake system 18, wherein the stack closing pressure represents the minimum amount of brake pressure required to generate braking torque through the brake stack 32. The fluid pressure at the transition point is stored in the memory 1034 ( Figure 7 ), where the memory 1034 stores magnitudes of previously recorded derivative values ​​of fluid pressure, which are referred to as a plurality of previously recorded values ​​at the transition point C. Thus, the stack closing pressure of the brake system 18 is the average of the fluid pressure at the transition point and the plurality of previously recorded values ​​at the transition point C. For example, in one embodiment, before the control module 22 determines the stack closing pressure, magnitudes of at least three fluid pressures are stored in the memory of the control module 22. It will be appreciated that the stack closing pressure may be adjusted over time to account for factors such as, for example, wear in the brake stack 32 and changes in the volume of the brake fluid.

[0035] Figure 3A A graph 80 is shown which shows that Figure 2The relationship between fluid pressure in pressurized chamber 48 and time during the process is shown. Figure 3A Also shown are a stack closing pressure 82 and a maximum pressure value 74. The stack closing pressure 82 represents the minimum amount of brake pressure required to generate the braking torque, and the maximum pressure value 74 represents the maximum amount of brake pressure that the brake system 18 can command. That is, at the maximum pressure value 74, the brake stack 32 ( Figure 1 ) is fully compressed. Figure 3B A graph 90 is shown which shows that Figure 2 Braking torque versus time during the process shown. Figure 3B Also shown is a zero torque point 92. The zero torque point 92 represents the brake stack 32 ( Figure 1 ) when to start generating braking torque to slow down or stop the vehicle 10.

[0036] Figure 4 is an exemplary process flow diagram illustrating a method 100 of determining a stack closure pressure of a brake system 18. Figure 1 and Figure 4 In both cases, the method 100 begins at block 102. In block 102, the control module 22 determines whether the method 100 is initiated. For example, if the vehicle 10 is an aircraft, the method 100 is initiated if the aircraft is in the air and the landing gear (not shown) of the aircraft is deployed. Once the method 100 is initiated, the method 100 proceeds to block 104.

[0037] In box 104 , the control module 22 generates the valve command 52 instructing the valve 26 to increase the fluid pressure of the brake system 18 and cause the amount of brake fluid supplied to the cylinder 40 to increase at a fixed rate. The method 100 may then proceed to box 106 .

[0038] In block 106, the control module 22 monitors the output 72 (proportional electrical signal 58) generated by the one or more pressure sensors 28. Figure 2 ). The method 100 may then proceed to block 108 .

[0039] In block 108, the control module 22 determines the output 72 ( Figure 2 ). It will be appreciated that as the valve 26 increases the amount of brake fluid supplied to the cylinder 40 at a fixed rate, the proportional electrical signal 58 is monitored by the control module 22. The method 100 may then proceed to box 110.

[0040] In block 110 , the control module 22 determines a transition point C of the derivative value, where the transition point C occurs when the derivative value exceeds approximately zero and increases to a positive value. The method 100 may then proceed to block 112 .

[0041] In block 112, the control module 22 stores the transition point C determined in block 110 in the memory 1034 ( Figure 7 The method may then proceed to decision block 114.

[0042] In decision box 114, control module 22 determines whether memory 1034 includes at least a threshold number of previously recorded fluid pressures at the transition point. For example, in one embodiment, the threshold number of previously recorded fluid pressures is two. Therefore, a total of three fluid pressures are stored in memory 1034. If memory 1034 does not include the threshold number of previously recorded values, method 100 proceeds to box 116. In box 116, control module 22 selects the fluid pressure at transition point C determined in box 110 as the brake stack pressure. Alternatively, control module 22 may not select a brake stack pressure. Method 100 may then terminate.

[0043] If the memory 1034 includes a threshold number of previously recorded values, the method 100 may proceed to box 118. In box 118, the control module 22 determines that the stack closing pressure of the brake system 18 is the fluid pressure at the transition point C and the average of the plurality of previously recorded values ​​at the transition point C. The method 100 may then terminate.

[0044] Figure 5A and Figure 5B An alternative method of determining the stack closure pressure is shown. That is, Figure 5A A graph 200 showing the response of the braking system 18 based on amplitude damping, Figure 5B is a graph 250 of the response of the braking system 18 based on phase lag. It will be appreciated that although amplitude damping and phase lag are shown in separate graphs, the braking system 18 may exhibit both responses. In other words, amplitude damping and phase lag are not mutually exclusive of each other. Referring now to Figure 1 and Figure 5A In both cases, the reference dashed line is the fluid pressure indicated by the valve command 196, and the solid line represents the output of the proportional electrical signal 198 generated by one or more pressure sensors 28. The fluid pressure indicated by the valve command 196 is in the form of a periodic signal. Figure 5A In the illustrated embodiment, the periodic signal comprises a sinusoidal waveform. Although a sinusoidal waveform is illustrated, it will be appreciated that other types of periodic signals may also be used. In an embodiment, the periodic signal comprises one of the following: a sinusoidal waveform, a step waveform, a pulse waveform, a triangle waveform, and a sawtooth waveform.

[0045] The periodic signal may also be referred to as a dithering input because the value of the periodic signal switches between respective maximum and minimum values. Specifically, the fluid pressure indicated by the valve command 196 includes each period P of the periodic signal.n The maximum value 202 and the minimum value 204 (where Figure 5A Show multiple cycles P 1 , P 2 Similarly, the output of the proportional electrical signal 198 also includes each period p of the periodic signal. n The maximum value is 212 and the minimum value is 214.

[0046] The valve command 52 instructs the valve 26 to adjust the fluid pressure of the brake system 18 based on the waveform of the periodic signal, which results in adjusting the amount of brake fluid supplied to the cylinder 40. For example, in the embodiment shown, the valve 26 adjusts the fluid pressure of the brake system 18 based on the sinusoidal waveform. The valve command 52 also instructs the valve 26 to increase the fluid pressure of the brake system 18 at a fixed rate while also adjusting the fluid pressure. This results in the amount of brake fluid supplied to the cylinder 40 increasing at a fixed rate while adjusting the amount of brake fluid. In other words, over time, each cycle P of the fluid pressure indicated by the valve command 196 is n The maximum value 202 and the minimum value 204 of P increase. For example, in the third period P 3 The maximum value 202 and the minimum value 204 are greater than the second period P 2 The corresponding maximum value 202 and minimum value 204 of the fourth period P 4 The maximum value 202 and the minimum value 204 of the third period P 3 The corresponding values ​​of the maximum value 202 and the minimum value 204 of .

[0047] Continue to refer to Figure 1 and Figure 5A , the valve 26 initially begins to increase the amount of brake fluid to the cylinder 40 as a result of increasing fluid pressure in the brake system 18 in response to receiving the valve command 52. However, the output of the proportional electrical signal 198 (generated by the one or more pressure sensors 28) does not match the fluid pressure indicated by the valve command 196 until the stack closing pressure 300 is reached. This is because the frequency response of the brake system 18 changes in response to changes in the compliance of the brake fluid within the cylinder 40 to match.

[0048] The fluid pressure of the pressurized chamber 48 of the cylinder 40 follows the waveform of the periodic signal of the valve command 52. Specifically, before the stack closing pressure 300 is achieved, the phase P of the fluid pressure indicated by the valve command 196 is n The phase p of the output of the proportional electrical signal 198 n However, after stack closing pressure 300 is achieved, a phase lag between valve command 196 and proportional electrical signal 198 is observed. It will be appreciated that Figure 5A Phase lag is usually not visible in the x-axis and y-axis scales. Figure 5B and described below. Return to reference Figure 5A , the specific phase P of the fluid pressure indicated by the valve command 196 n The maximum value 202 and the minimum value 204 do not correspond to the corresponding phase p n The maximum value 212 and the minimum value 216 of the output of the proportional electrical signal 198 match until the proportional electrical signal 58 is approximately equal to the stack closing pressure 300 .

[0049] like Figure 5A As seen in FIG. 1 , the corresponding phase p of the output of the proportional electrical signal 198 n The pressure amplitude a n A single phase P of fluid pressure less than that indicated by valve command 196 n Valve amplitude A n , until the proportional electrical signal 58 generated by the pressure sensor 28 is approximately equal to the stack closing pressure 300. However, after the stack closing pressure 300 is achieved, the corresponding phase p of the output of the proportional electrical signal 198 is n The pressure amplitude a n The single phase P of the fluid pressure indicated by the valve command 196 n The valve amplitude A is defined n Therefore, the control module 22 determines a single phase P of the command pressure indicated by the valve command 196 n Valve amplitude A n and the corresponding phase p of the output of the proportional electrical signal 198 generated by the one or more pressure sensors 28 n The pressure amplitude a n Then, the control module 22 sets the valve amplitude A n With pressure amplitude a n In response to determining the valve amplitude A n and pressure amplitude a n Being approximately equal to each other, the control module 22 determines that the output of the proportional electrical signal 198 is approximately equal to the stack closing pressure 300 .

[0050] In one non-limiting embodiment, when the first amplitude A n and the second amplitude a n When the difference between the fluid pressure indicated by the valve command 196 and the output of the proportional electrical signal 198 is equal to or less than about twenty-seven percent (27%), the control module 22 determines that the fluid pressure indicated by the valve command 196 and the output of the proportional electrical signal 198 are approximately equal to each other. However, it will be understood that this value is merely exemplary in nature. In practice, the amplitude difference between the fluid pressure indicated by the valve command 196 and the output of the proportional electrical signal 198 may vary based on the accuracy required for a particular application.

[0051] In one embodiment, once the control module 22 determines that the value indicated by the output of the proportional electrical signal 198 is approximately equal to the fluid pressure indicated by the valve command 196, the control module 22 stores the value of the output of the proportional electrical signal 198 in the memory 1034 of the control module 22 ( Figure 7 ). In one embodiment, the memory 1034 includes a threshold number of multiple previously recorded outputs of the proportional electrical signal 198. As described above, in one embodiment, the threshold number of multiple previously recorded outputs of the proportional electrical signal 198 is two. Therefore, the stack closing pressure of the brake system 18 is the output of the proportional electrical signal 198 and the average of the two previously recorded outputs of the proportional electrical signal 198.

[0052] Figure 6 is shown based on the amplitude attenuation, based on Figure 5A A process flow diagram of an alternative method 400 for determining a stack closing pressure of a brake stack 32 using a periodic signal is shown. Figure 1 , Figure 5A and Figure 6 , the method 400 begins at block 402. In block 402, the control module 22 initiates the method 400. For example, if the vehicle 10 is an aircraft, the method 400 is initiated if the aircraft is in the air and the landing gear (not shown) of the aircraft is deployed. Once the method 400 is deployed, the method 400 proceeds to block 404.

[0053] In block 404, the control module 22 generates a valve command 52 instructing the valve 56 to adjust the fluid pressure of the brake system 18 and causes the amount of brake fluid supplied to the cylinder 40 to be adjusted based on the waveform of the periodic signal, which Figure 5A and Figure 5B 4. The method 400 may then proceed to block 406.

[0054] In block 406, the control module 22 monitors the output of the proportional electrical signal 198 generated by the one or more pressure sensors 28. Figure 5A and Figure 5B As seen in FIG. 4 , the output of the proportional electrical signal 198 is not equal to the fluid pressure indicated by the valve command 196 until the stack closing pressure 300 is achieved. The method 400 may then proceed to block 408 .

[0055] In block 408, in response to the output of the proportional electrical signal 198 being approximately equal to the fluid pressure indicated by the valve command 196, the control module 22 determines that the fluid pressure within the cylinder 40 is at the stack closing pressure 300, wherein the stack closing pressure represents a minimum amount of brake pressure required to generate braking torque through the brake stack 32. The method 400 may then proceed to block 410.

[0056] In block 410, the control module 22 stores the output value of the proportional electrical signal 198 approximately equal to the fluid pressure indicated by the valve command 196 in the memory 1034 ( Figure 7 The method 400 may then proceed to decision block 412.

[0057] In decision block 412, the control module 22 determines whether the memory 1034 includes at least a threshold number of previously recorded outputs of the proportional electrical signal 198. For example, in one embodiment, the threshold number of previously recorded outputs of the proportional electrical signal 198 is two. If the memory 1034 does not include a threshold number of previously recorded outputs of the proportional electrical signal 198, the method 400 proceeds to block 414. In block 412, the control module 22 selects the output value of the proportional electrical signal 198 determined in block 408 as the brake stack pressure. Alternatively, the control module 22 may not select the brake stack pressure. The method 400 may then terminate.

[0058] If the memory 1034 includes a threshold number of outputs of the proportional electrical signal 198, the method 400 may proceed to block 416. In block 416, the control module 22 determines that the stack closing pressure of the brake system 18 is approximately equal to the average of the output value of the proportional electrical signal 198 of the fluid pressure indicated by the valve command 196 and the previously recorded output of the proportional electrical signal 198. The method 400 may then terminate.

[0059] Now refer to Figure 1 and Figure 5B , we now describe the phase lag. Specifically, Figure 5B Graph 250 in FIG. 5 shows the output of valve command 196 and proportional electrical signal 198 generated by one or more pressure sensors 28. Valve 26 regulates the fluid pressure of brake system 18 based on the periodic signal of the sinusoidal waveform. Valve command 52 also instructs valve 26 to increase the fluid pressure of brake system 18 at a fixed rate while also regulating the fluid pressure, which results in increasing the amount of brake fluid supplied to cylinder 40 at a fixed rate while regulating the amount of brake fluid.

[0060] The fluid pressure of the pressurized chamber 48 of the cylinder 40 follows the waveform of the periodic signal of the valve command 52. Specifically, before the stack closing pressure 300 is achieved, the phase p of the output of the proportional electrical signal 198 is n and the phase P of the fluid pressure indicated by the valve command 196 n However, immediately after stack closing pressure 300 is achieved, there is a phase lag 304 between valve command 196 and proportional electrical signal 198. Figure 5A As seen in the figure, immediately following the proportional electrical signal 58 ( Figure 1) is approximately equal to the stack closing pressure 300, the phase p of the output of the proportional electrical signal 198 n The phase P of the fluid pressure indicated by the valve command 196 n In other words, the phase p of the output of the proportional electrical signal 198 is n The phase P of the fluid pressure indicated by the valve command 196 n There is a phase lag 304 between them.

[0061] Figure 5B The phase lag 304 shown represents the difference between the maximum value 202 of the output of the proportional electrical signal 198 and the maximum value 212 of the fluid pressure indicated by the valve command 196. However, it will be understood that the phase lag 304 can be represented as the difference between any two similar points measured along the proportional electrical signal 198 and the fluid pressure indicated by the valve command 196. After the stack closing pressure 300 is reached, the phase lag 304 remains constant. In other words, the first maximum value 202 of the output of the proportional electrical signal 198 is 1 The first maximum value 212 of the fluid pressure indicated by the valve command 196 1 The phase lag 304 measured between the output of the proportional electrical signal 198 and the third maximum value 202 is approximately 3 The third maximum value 212 of the fluid pressure indicated by the valve command 196 3 However, it will be appreciated that the phase lag 304 is recalculated over the life of the brake system to account for changes to the brake system 18, such as brake wear and any changes in the volume of brake fluid.

[0062] Figure 7 is a process flow diagram illustrating an alternative method 500 for determining a stack closing pressure of a brake stack 32 based on a phase shift. Figure 1 , Figure 5B and Figure 6 , the method 500 begins at block 502. In block 502, the control module 22 initiates the method 400. Once the method 500 is initiated, the method 400 proceeds to block 504.

[0063] In block 504, the control module 22 generates a valve command 52 instructing the valve 56 to adjust the fluid pressure of the brake system 18, which results in adjusting the amount of brake fluid supplied to the cylinder 40 based on the waveform of the periodic signal, as shown in FIG. Figure 5B The fluid pressure indicated by the valve command 196 is then seen. The method 500 may then proceed to block 506 .

[0064] In block 506, the control module 22 monitors the output of the proportional electrical signal 198 generated by the one or more pressure sensors 28. Figure 5BAs seen in FIG. 5 , the output of the proportional electrical signal 198 is in phase with the fluid pressure indicated by the valve command 196 until the stack closing pressure 300 is achieved. The method 500 may then proceed to block 508 .

[0065] In block 508 , the control module 22 detects the phase lag 304 , which represents a lag in the output of the proportional electrical signal 198 generated by the one or more pressure sensors compared to the fluid pressure indicated by the valve command 196 . The method 500 may then proceed to block 510 .

[0066] In block 510, in response to detecting the phase lag 304, the control module 22 stores the output value of the proportional electrical signal 198 generated by the one or more pressure sensors 28 immediately after the phase lag 304 is detected in the memory 1034 ( Figure 7 Then, the method 500 may proceed to decision block 512.

[0067] In decision block 512, the control module 22 determines whether the memory 1034 includes at least a threshold number of previously recorded outputs of the proportional electrical signal 198. For example, in one embodiment, the threshold number of previously recorded outputs of the proportional electrical signal 198 is two. If the memory 1034 does not include a threshold number of previously recorded outputs of the proportional electrical signal 198, the method 500 proceeds to block 514. In block 512, the control module 22 selects the value of the output of the proportional electrical signal 198 determined in block 510 as the brake stack pressure. Alternatively, the control module 22 may not select the brake stack pressure. The method 500 may then terminate.

[0068] If the memory 1034 includes a threshold number of outputs of the proportional electrical signal 198, the method 500 may proceed to block 516. In block 516, the control module 22 determines the stack closing pressure of the brake system 18 as an average of the value of the output of the proportional electrical signal 198 generated by the one or more pressure sensors 28 immediately after the phase lag 304 is detected and the previously recorded output of the proportional electrical signal 198. The method 500 may then terminate.

[0069] Referring generally to the accompanying drawings, the disclosed braking system provides a relatively simple and robust method of determining a stack closing pressure for a brake stack. The value of the stack closing pressure can be used as an initial pressure command, which results in a reduction in the amount of hysteresis that typically occurs in conventional braking systems when the brakes are initially applied. In addition, it will be appreciated that the value of the stack closing pressure is not fixed and can be adjusted to accommodate changes to the braking system that occur over time. Specifically, the stack closing pressure is recalculated over the life of the braking system to account for changes to the braking system, such as brake wear and any changes in the volume of brake fluid. It will be appreciated that a vehicle such as an aircraft includes more than one braking system, and each braking system may include its own separate stack closing pressure.

[0070] Now refer to Figure 7 , the control module 22 is implemented on one or more computer devices or systems such as an exemplary computer system 1030. The computer system 1030 includes a processor 1032, a memory 1034, a mass storage memory device 1036, an input / output (I / O) interface 1038, and a human-machine interface (HMI) 1040. The computer system 1030 is operatively coupled to one or more external resources 1042 via the network 1026 or the I / O interface 1038. The external resources may include, but are not limited to, servers, databases, mass storage devices, peripheral devices, cloud-based network services, or any other suitable computer resources that may be used by the computer system 1030.

[0071] The processor 1032 includes one or more devices selected from a microprocessor, a microcontroller, a digital signal processor, a microcomputer, a central processing unit, a field programmable gate array, a programmable logic device, a state machine, a logic circuit, an analog circuit, a digital circuit, or any other device that manipulates signals (analog or digital) based on operating instructions stored in the memory 1034. The memory 1034 includes a single memory device or multiple memory devices, including (but not limited to) read-only memory (ROM), random access memory (RAM), volatile memory, non-volatile memory, static random access memory (SRAM), dynamic random access memory (DRAM), flash memory, cache memory, or any other device capable of storing information. The mass storage memory device 1036 includes data storage devices such as hard disk drives, optical drives, tape drives, volatile or non-volatile solid-state devices, or any other device capable of storing information.

[0072] The processor 1032 operates under the control of an operating system 1046 residing in the memory 1034. The operating system 1046 manages computer resources so that computer program code embodied as one or more computer software applications (e.g., applications 1048 residing in the memory 1034) may have instructions executed by the processor 1032. In an alternative example, the processor 1032 may directly execute the application 1048, in which case the operating system 1046 may be omitted. One or more data structures 1049 also reside in the memory 1034 and may be used by the processor 1032, the operating system 1046, or the application 1048 to store or manipulate data.

[0073] The I / O interface 1038 provides a machine interface that connects the processor 1032 to other devices and systems (e.g., the network 1026 or external resources 1042) when in operation. The application 1048 thus works in cooperation with the network 1026 or external resources 1042 by communicating via the I / O interface 1038 to provide various features, functions, applications, processes, or modules that include examples of the present disclosure. The application 1048 also includes program code executed by one or more external resources 1042, or relies on functions or signals provided by other systems or network components external to the computer system 1030. In fact, given that an almost endless number of hardware and software configurations are possible, one of ordinary skill in the art will understand that examples of the present disclosure may include applications that are located external to the computer system 1030, distributed among multiple computers or other external resources 1042, or provided by computing resources (hardware and software) provided as a service (e.g., cloud computing services) via the network 1026.

[0074] The HMI 1040 is operatively coupled to the processor 1032 of the computer system 1030 in a known manner to allow a user to interact directly with the computer system 1030. The HMI 1040 may include a video or alphanumeric display, a touch screen, speakers, and any other suitable audio and visual indicators capable of providing data to the user. The HMI 1040 also includes input devices and controls (e.g., alphanumeric keyboards, pointing devices, keypads, buttons, control knobs, microphones, etc.) capable of accepting commands or input from a user and sending the typed input to the processor 1032.

[0075] The database 1044 may reside on the mass storage memory device 1036 and may be used to collect and organize data used by the various systems and modules described herein. The database 1044 may include data and supporting data structures for storing and organizing the data. Specifically, the database 1044 may be arranged with any database organization or structure, including (but not limited to) a relational database, a hierarchical database, a network database, or a combination thereof. A database management system in the form of a computer software application executed as instructions on the processor 1032 may be used to access information or data stored in records of the database 1044 in response to a query, where the query may be dynamically determined and executed by the operating system 1046, other applications 1048, or one or more modules.

[0076] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. These variations should not be regarded as departing from the spirit and scope of the present disclosure.

Claims

1. A brake system (18) having: a brake stack (32) having a stack closing pressure (82), a force member (30) positioned within a cylinder (40), a valve (56) configured to regulate fluid pressure in the brake system (18), and one or more pressure sensors (28) generating a proportional electrical signal (58) representative of the fluid pressure within the cylinder (40), the brake system (18) comprising: one or more processors (1032) in electronic communication with the valve (56) and the one or more pressure sensors (28); as well as A memory (1034) coupled to the one or more processors (1032), the memory (1034) storing data including a database (1044) and program code that, when executed by the one or more processors (1032), causes the brake system (18) to: generating a valve command (156) instructing the valve (56) to increase the fluid pressure in the brake system (18), which causes the amount of brake fluid supplied to the cylinder (40) to increase at a fixed rate; monitoring an output of the proportional electrical signal (58) generated by the one or more pressure sensors (28); determining a derivative value of the output of the proportional electrical signal (58) as the amount of the brake fluid supplied to the cylinder (40) increases at the fixed rate; determining a transition point (C) of the derivative value, wherein the transition point (C) indicates when the derivative value exceeds zero and increases to a positive value; and The fluid pressure at the transition point (C) is selected as the stack closing pressure (82) of the brake system (18).

2. The brake system (18) according to claim 1, wherein: The one or more processors (1032) execute instructions to: The fluid pressure at the transition point (C) is stored in the memory (1034), wherein the memory (1034) includes a plurality of previously recorded values ​​at the transition point (C).

3. The braking system (18) according to claim 2, wherein: The one or more processors (1032) execute instructions to: The stack closing pressure (82) of the brake system (18) is determined to be the fluid pressure at the transition point (C) and an average of the plurality of previously recorded values ​​at the transition point (C).

4. The brake system (18) according to claim 1, wherein: Automatic braking instructions are stored in the memory (1034), and wherein the one or more processors (1032) execute the instructions to: generating an input command (50) from the automatic braking instruction, wherein the input command (50) represents an amount of braking requested by the braking system (18); and The valve command (156) is determined based at least on the input command (50).

5. The brake system (18) according to claim 1, wherein: The one or more processors (1032) execute instructions to: determining that the derivative value of the output of the proportional electrical signal (58) is below a threshold pressure value; and In response to determining that the derivative value of the output of the proportional electrical signal (58) is below the threshold pressure value, the derivative value is set to zero.

6. The brake system (18) according to claim 1, wherein: The brake fluid is one of a liquid and a gas.

7. The brake system (18) according to claim 1, wherein: The braking system (18) includes a dead space.

8. The brake system (18) of claim 1, wherein: The proportional electrical signal (58) is selected from the group consisting of a current value, a capacitance value, and a voltage value.

9. An aircraft having a braking system (18), the aircraft comprising: A brake stack (32) comprising one or more rotors (36) interleaved with one or more stators (38); a force member (30) positioned within the cylinder (40); a valve (56) configured to regulate fluid pressure in the brake system (18); one or more pressure sensors (28) generating a proportional electrical signal (58) representative of the pressure of the fluid within the cylinder (40); one or more processors (1032) in electronic communication with the valve and the one or more pressure sensors (28); and A memory (1034) coupled to the one or more processors (1032), the memory (1034) storing data including a database (1044) and program code that, when executed by the one or more processors (1032), causes the brake system (18) to: generating a valve command (156) instructing the valve (56) to increase the fluid pressure in the brake system (18), which causes the amount of hydraulic brake fluid supplied to the cylinder (40) to increase at a fixed rate; monitoring an output of the proportional electrical signal (58) generated by the one or more pressure sensors (28); determining a derivative value of the output of the proportional electrical signal (58) as the amount of the hydraulic brake fluid supplied to the cylinder (40) increases at the fixed rate; determining a transition point (C) of the derivative value, wherein the transition point (C) indicates when the derivative value exceeds zero and increases to a positive value; and The fluid pressure at the transition point (C) is selected as a stack closing pressure (82) of the brake system (18), wherein the stack closing pressure (82) represents a minimum amount of brake pressure required to generate braking torque through the brake stack (32).

10. The aircraft according to claim 9, wherein: The aircraft has a braking system according to any one of claims 2 to 8.

11. A method of determining a stack closing pressure (82) of a brake stack (32) of a brake system (18), the method comprising the steps of: generating, by a computer (1030), a valve command (156) instructing a valve (56) to increase fluid pressure of the brake system (18), which causes the amount of brake fluid supplied to a cylinder (40) to increase at a fixed rate, wherein a force member (30) is positioned within the cylinder (40) and the valve (56) is configured to control the amount of brake fluid supplied to the cylinder (40); monitoring, by the computer (1030), an output of a proportional electrical signal (58) generated by one or more pressure sensors (28), wherein the proportional electrical signal (58) is representative of the fluid pressure within the cylinder (40); determining a derivative value of the output of the proportional electrical signal (58) as the amount of the brake fluid supplied to the cylinder (40) increases at the fixed rate; determining a transition point (C) of the derivative value, wherein the transition point (C) indicates when the derivative value exceeds zero and increases to a positive value; and The fluid pressure at the transition point (C) is selected as the stack closing pressure (82) of the brake system (18).

12. The method according to claim 11, further comprising the steps of: The fluid pressure at the transition point (C) is saved in a memory (1034) of the computer (1030), wherein the memory (1034) includes a plurality of previously recorded values ​​at the transition point (C).

13. The method according to claim 12, further comprising the steps of: The stack closing pressure (82) of the brake system (18) is determined to be the fluid pressure at the transition point (C) and an average of the plurality of previously recorded values ​​at the transition point (C).

14. The method according to claim 11, further comprising the steps of: generating an input command (50) from an automatic braking instruction, wherein the input command (50) represents the amount of braking requested by the braking system (18), and the automatic braking instruction is stored in a memory (1034) of the computer (1030); and The valve command (156) is determined based at least on the input command (50).

15. The method according to claim 11, further comprising the steps of: determining that the derivative value of the output of the proportional electrical signal (58) is below a threshold pressure value; and In response to determining that the derivative value of the output of the proportional electrical signal (58) is below the threshold pressure value, the derivative value is set to zero.

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