BR102018010470B1 - MONITORING SYSTEM, AND, IMPACT SHOCK ABSORBER ARRANGEMENT - Google Patents

Abstract

A monitoring system for a separate two-stage gas/fluid shock absorber that may comprise a controller and a tangible, non-transient memory configured to communicate with the controller. Tangible, non-transitory memory may have instructions stored in it that, in response to execution by the controller, cause the controller to perform various operations. Said operations may include calculating, by the controller, a nominal pressure of the secondary chamber, determining, by the controller, a shock absorber stroke associated with the nominal pressure of the secondary chamber, calculating, by the controller, a volume of oil in an oil chamber of the shock absorber, the calculation by the controller of a volume of gas in a primary chamber of the shock absorber, the calculation by the controller of an inflation pressure of the secondary chamber and calculation by the controller of a volume of oil leaked into the primary chamber of the shock absorber.

Description

FIELD OF INVENTION

[001] The present disclosure relates to landing gear and, more particularly, to systems and methods for monitoring impact absorbers.

FUNDAMENTALS

[002] Impact absorption devices are used in a wide variety of vehicle suspension systems to control the movement of the vehicle and its tires relative to the ground and to reduce the transmission of transient forces from the ground to the vehicle. Shock absorbing bumpers are a common component in most aircraft landing gear assemblies. Shock absorbers control the movement of landing equipment and absorb and dampen loads imposed on the landing gear during landing, taxiing, braking and takeoff.

[003] An impact absorber generally performs these functions by compressing a fluid within a sealed chamber formed by hollow telescopic cylinders. Fluid generally includes both a gas and a liquid, such as hydraulic fluid or oil. One type of shock absorber generally utilizes an “air over oil” arrangement in which a volume of confined gas is compressed as the shock absorber is compressed axially and a volume of oil is measured through an orifice. The gas acts as an energy storage device, similar to a spring, so that after a compressive force ends, the shock absorber returns to its original length. Shock absorbers also dissipate energy by passing oil through the orifice so that as the shock absorber is compressed or extended, its rate of movement is limited by the damping action from the interaction of the orifice and the oil.

[004] The performance of the shock absorber assembly may degrade over time. This degradation can cause damage to other aircraft components, including bearings in the landing gear assembly.

[005] The functionality and performance of a landing gear shock absorber may depend on internal gas and oil levels. Gas pressure and oil volume can be maintained within a design envelope to ensure landing gear functionality is within an acceptable range.

SUMMARY

[006] A monitoring system for a dual-stage separate gas/fluid shock absorber is disclosed herein, according to various embodiments. The monitoring system for a two-stage separate gas/fluid shock absorber may comprise a controller and a tangible, non-transitory memory configured to communicate with the controller, the tangible, non-transitory memory having instructions stored therein which, in response to execution by the controller, cause the controller to perform operations comprising: receiving, by the controller, a temperature sensor reading from the primary chamber; reception, by the controller, of the primary chamber pressure sensor reading; receiving, by the controller, a reading from the shock absorber travel sensor; calculation, by the controller, of a nominal pressure of the secondary chamber based on the reading of the primary chamber temperature sensor; determination, by the controller, of an impact shock absorber stroke associated with the nominal pressure of the secondary chamber; calculating, by the controller, a volume of oil in an oil chamber of the two-stage separate gas/fluid shock absorber; calculating, by the controller, a volume of gas in a primary chamber of the two-stage separate gas/fluid shock absorber based on at least the volume of oil; calculation, by the controller, of an inflation pressure of the secondary chamber; and calculating, by the controller, a volume of oil leaked into the primary chamber of the two-stage separate gas/fluid shock absorber, based on the inflation pressure of the secondary chamber.

[007] In various embodiments, the instructions may cause the controller to perform additional operations comprising calculating, by the controller, a number of moles of gas in the primary chamber of the two-stage separate gas/fluid shock absorber, based on at least in the volume of gas in the primary chamber. The instructions may cause the controller to perform other operations that include calculating, by the controller, a volume of gas in a secondary chamber of the two-stage separate gas/fluid shock absorber, and calculating, by the controller, a number of moles of gas in the secondary chamber of the two-stage separate gas/fluid shock absorber, based on at least the volume of gas in the secondary chamber. The instructions may cause the controller to perform additional operations comprising calculating, by the controller, a displacement volume of the secondary chamber of the two-stage separate gas/fluid shock absorber. Calculation by the controller of the oil volume may comprise: calculation by the controller of an estimate of the first oil volume using the nominal pressure of the secondary chamber and the stroke of the shock absorber associated with the nominal pressure of the secondary chamber; calculation, by the controller, of a second nominal pressure of the second secondary chamber; determining, by the controller, a second shock absorber stroke associated with the second nominal pressure of the secondary chamber; and calculate, by the controller, a second estimate of the oil volume using the second nominal pressure of the secondary chamber and the second stroke of the shock absorber associated with the nominal pressure of the secondary chamber. The controller's calculation of the oil volume may include the controller calculating an error between the estimate of the first oil volume and the estimate of the second oil volume and determining by the controller whether the error is less or less. equal to a threshold value. The controller may determine the oil volume in the oil chamber as the first oil volume estimate in response to the error being less than or equal to the threshold value. The instructions may cause the controller to perform additional operations comprising at least one of: comparing, by the controller, the volume of oil in the oil chamber with a plurality of threshold values; comparing, by the controller, the number of moles of gas in the primary chamber with a plurality of threshold values; comparing, by the controller, the number of moles of gas in the secondary chamber with a plurality of threshold values; and comparing, by the controller, the volume of oil leaked into the primary chamber with a plurality of limit values. The instructions may cause the controller to perform additional operations including the controller issuing a maintenance message in response to the comparison. The nominal pressure of the secondary chamber can be adjusted according to the reading of the primary chamber temperature sensor. The controller may be in electronic communication with a pressure/temperature sensor for the primary chamber. The instructions may cause the controller to perform additional operations, including adjusting the volume of oil in the oil chamber to a reference temperature. The instructions may cause the controller to perform additional operations, comprising calculating by the controller a deviation of the oil volume in the primary chamber from a nominal oil volume level for the oil chamber.

[008] An arrangement of a separate two-stage gas/fluid shock absorber is disclosed herein, according to various embodiments. The two-stage separate gas/fluid shock absorber arrangement may comprise the two-stage separate gas/fluid shock absorber, a pressure/temperature sensor mounted in the primary gas chamber, a stroke sensor mounted in the two-stage separate gas/fluid impact and monitoring system. The two-stage separate gas/fluid shock absorber may comprise a buffer cylinder, a buffer piston operatively coupled to the buffer cylinder, an oil chamber, a primary gas chamber, and a secondary gas chamber. The monitoring system may comprise a recorder configured to receive a plurality of sensor readings from at least one of the pressure/temperature sensor and the course sensor, a landing detector configured to detect a landing event based on a sensor reading. stroke received from the stroke sensor and a health monitor configured to determine a volume of oil in the oil chamber, a volume of gas in the primary gas chamber, and a volume of gas in the secondary gas chamber.

[009] In various embodiments, the monitoring system may further comprise a takeoff detector configured to detect a takeoff event based on the course sensor reading received from the course sensor, wherein the plurality of sensor readings are recorded after a takeoff event. The primary gas chamber may be separated from the oil chamber by a first separator piston and the secondary gas chamber is separated from the oil chamber by a second separator piston. The monitoring system may further comprise a counter configured to prevent the at least one landing detector and takeoff detector from receiving data from the recorder for a predetermined period, and a data profiler configured to receive data from the health monitor. The health monitor can calculate the nominal pressure of a secondary chamber, determine a shock absorber stroke associated with the nominal pressure of the secondary chamber, and calculate the volume of oil in the oil chamber.

[0010] A method for monitoring a two-stage separate gas/fluid shock absorber is disclosed herein, according to various embodiments. The method may comprise receiving, by a controller, a reading from the primary chamber temperature sensor; receive, by the controller, a reading from the primary chamber pressure sensor; receive, by the controller, a reading from the shock absorber travel sensor; calculate, by the controller, a nominal pressure of the secondary chamber based on the reading of the primary chamber temperature sensor; determine, by the controller, an impact shock absorber stroke associated with the nominal pressure of the secondary chamber; calculating, by the controller, a volume of oil in an oil chamber of the two-stage separate gas/fluid shock absorber; calculating, by the controller, a gas volume in a primary gas chamber of the two-stage separate gas/fluid shock absorber based on at least the oil volume; calculating, by the controller, a number of moles of gas in the primary gas chamber of the two-stage separate gas/fluid shock absorber; calculating, by the controller, a volume of oil that has leaked into the primary gas chamber of the two-stage separate gas/fluid shock absorber; calculating, by the controller, a volume of gas in a secondary chamber of the two-stage separate gas/fluid shock absorber; and calculate, by the controller, a number of moles of gas in the secondary chamber.

[0011] In various embodiments, the controller's calculation of the volume of oil in the oil chamber may comprise: calculation, by the controller, of an estimate of the first oil volume using the nominal pressure of the secondary chamber and the stroke of the damper impact associated with the nominal pressure of the secondary chamber; calculation, by the controller, of a second nominal pressure of the second secondary chamber; determining, by the controller, a second shock absorber stroke associated with the second nominal pressure of the secondary chamber; and calculate, by the controller, a second estimate of the oil volume using the second nominal pressure of the secondary chamber and the second stroke of the shock absorber associated with the nominal pressure of the secondary chamber; and sending, by the controller, a maintenance message to a display screen.

[0012] The foregoing features and elements may be combined in various non-exclusive combinations, unless expressly indicated otherwise in this document. These features and elements, as well as the operation of the disclosed embodiments, will become more apparent in light of the following description and the attached figures.

BRIEF DESCRIPTION OF FIGURES

[0013] FIG. 1 illustrates a schematic view of a two-stage separate gas/fluid shock absorber at a zero (0) stroke (i.e., maximum extension), in accordance with various embodiments; FIG. 2 illustrates a schematic view of the two-stage separate gas/fluid shock absorber of FIG. 1 in a course of activation of the secondary gas chamber (Sactivation), according to various modalities; FIG. 3 illustrates a schematic view of the two-stage separate gas/fluid shock absorber of FIG. 1 at a maximum stroke (Smax), according to various modalities; FIG. 4A illustrates a schematic view of a two-stage separate gas/fluid shock absorber arrangement comprising the two-stage separate gas/fluid shock absorber of FIG. 2 and a monitoring system, according to various embodiments; FIG. 4B illustrates a schematic view of the two-stage separate gas/fluid shock absorber arrangement of FIG. 4A, with a more detailed view of the monitoring system, according to various modalities; FIG. 4C illustrates a schematic view of a portion of the monitoring system of FIG. 4B with a takeoff detector, in accordance with various embodiments; FIG. 5A illustrates a spring dynamic curve of a primary gas chamber, in accordance with various embodiments; FIG. 5B illustrates a dynamic spring curve of a primary gas chamber, in a scenario in which a significant pressure loss occurred in a secondary gas chamber, according to various embodiments; FIG. 5C illustrates the dynamic curves of the spring of a primary gas chamber representing the pressure points used to estimate the volume of oil, according to various embodiments; FIG. 6 illustrates an algorithm for estimating a volume of oil in an oil chamber of a shock absorber, according to various embodiments; FIG. 7 illustrates an algorithm for estimating a displacement volume of a primary gas chamber, according to various embodiments; FIG. 8 illustrates an algorithm for estimating a secondary chamber inflation pressure, according to various embodiments; and FIG. 9A and FIG. 9B illustrate a method for monitoring a two-stage separate gas/fluid shock absorber, according to various embodiments.

[0014] The subject matter of the present disclosure is particularly highlighted and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, can best be obtained by reference to the detailed description and the claims when considered in connection with the figures, wherein like numbers indicate like elements.

DETAILED DESCRIPTION

[0015] The detailed description of example embodiments in this document refers to the attached figures, which show example embodiments by way of illustration. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be carried out and that logical changes and adaptations in design and construction may be made in accordance with this disclosure and the teachings of this document without departing from the spirit and scope of the disclosure. Therefore, the detailed description in this document is presented for illustration purposes only and not for limitation.

[0016] System program instructions and/or controller instructions may be loaded into a tangible, non-transitory, computer-readable medium (also referred to herein as a tangible, non-transitory memory) having instructions stored thereon as , in response to execution by a controller, causes the controller to perform various operations. The term “non-transient” should be understood as removing only the propagation of transient signals per se from the scope of the claim and does not waive the rights of all standard computer-readable media that are not only propagating transient signals per se. Stated differently, the meaning of the term “computer-readable non-transitory medium” and “computer-readable non-transitory storage medium” should be interpreted as excluding only those types of computer-readable transient media found in In Re Nuijten that leave the scope of patentable subject matter under 35 U.S.C. § 101.

[0017] A gas pressure and stroke in static condition of a shock absorber can be measured, and any deviation from the theoretical static air suspension curve of the shock absorber can be compensated by re-maintaining the shock absorber with gas . Such an approach can be taken to reduce the maintenance time associated with just adding gas to the shock absorber. However, this approach assumes that the deviation from the static air suspension curve is due solely to gas loss and therefore can ignore oil leakage into the system.

[0018] Aircraft landing gear systems, in accordance with the present disclosure, may comprise an impact shock absorber. An impact shock absorber can comprise various fluids, such as oil and gas. Shock absorber performance can be evaluated by monitoring aspects of the shock absorber, including primary chamber gas temperature, primary chamber gas pressure, and shock absorber shock absorber stroke at various points during aircraft operation. Stroke may refer to a shock absorber piston position relative to a shock absorber cylinder.

[0019] A monitoring system as provided herein may comprise an integrated pressure/temperature sensor installed in the primary gas chamber separate two-stage gas/fluid shock absorber, a stroke sensor that directly or indirectly measures the shock absorber travel and an electronic control unit that runs a monitoring algorithm. The monitoring algorithm can use transient gas pressure and gas temperature during landing or takeoff and quantifies oil and gas levels in the shock absorber. Furthermore, the monitoring system can estimate oil leakage in gas chambers. The monitoring algorithm can issue a maintenance message based on estimated fluid and gas levels.

[0020] As oil and gas levels can be determined independently, these levels can be used for diagnostic and prognostic purposes. The oil or gas loss rate can be used to schedule future maintenance.

[0021] The following nomenclature in table 1 and table 2 corresponds to various equations and parameters described in the present disclosure: Table 1. - Measurements Table 2 - Internal parameters of the algorithm

[0022] In various embodiments, a two-stage separate gas/fluid shock absorber monitoring system is provided herein. A functional schematic view of such a shock absorber is presented in FIG. 1.

[0023] With reference to FIG. 1, a separate two-stage gas/fluid shock absorber (impact absorber) 100 is illustrated, in accordance with various embodiments. The shock absorber 100 may comprise a shock absorber cylinder 110 and a shock absorber piston 120. The shock absorber piston 120 may be operatively coupled to the shock absorber cylinder 110 as described herein. The shock cylinder 110 may be configured to receive the shock piston 120 in a manner that allows the two components to telescopically move together and absorb and dampen forces that are transmitted thereto. In various embodiments, a liquid, such as a hydraulic fluid and/or oil, may be located within the shock cylinder 110. Additionally, a gas, such as nitrogen or air, may be located within the shock cylinder 110. The cylinder of the shock absorber 110 and the shock absorber piston 120 may, for example, be configured to seal such that fluid contained within the shock absorber cylinder 110 is prevented from leaking as the shock absorber piston 120 translates relative to the shock absorber cylinder 110.

[0024] The shock absorber 100 may consist of a low pressure primary gas chamber 130 in which the gas is contained. In this regard, a gas volume (also referred to herein as a primary chamber gas volume) 131 and may be contained in the primary gas chamber 130. The shock absorber 100 may further consist of a secondary high-pressure gas chamber. 140. In this regard, a volume of gas 141 (also referred to herein as a volume of secondary chamber gas) may be contained in the secondary gas chamber 140. The volume of gas 131 may be at a lower pressure than the volume of gas 141 when the shock absorber 100 is in the fully extended position (i.e., at a shock absorber stroke of zero). The primary gas chamber 130 may be located at a first end 191 of the shock absorber 100. The first end 191 may be the bottom of the shock absorber 100. The secondary gas chamber 140 may be located at a second end 192 of the shock absorber 100. The second end 192 may be the upper part of the shock absorber 100.

[0025] The shock absorber 100 may further consist of an oil chamber 150. In this regard, a volume of oil (also referred to herein as an oil chamber oil volume) 151 may be contained in the oil chamber 150. The primary gas chamber 130 may be separated from the oil chamber 150 by a separator piston (also referred to herein as a first separator piston) 132. The secondary gas chamber 140 may be separated from the oil chamber 150 by a piston separator (also referred to herein as a second separator piston) 142. The separator piston 142 can translate within the secondary gas chamber 140. FIG. 1 illustrates the separator piston 142 in a minimum compression stroke (also referred to herein as being “bottom to top”). Stated differently, with the shock absorber 100 in the fully extended position, the separator piston 142 may be located in a position such that the volume of the secondary gas chamber 140 is at its maximum value. When the separator piston 142 is bottomed out, it can be mechanically prevented from translating to the first end 191.

[0026] The shock absorber 100 may further consist of an orifice plate 114. The orifice plate 114 may be located in the oil chamber 150. The shock absorber 100 may comprise an oil loading port 102 in hydraulic communication with the shock absorber 100 may comprise an oil bleed port 104 in fluid communication with the oil chamber 150. The shock absorber 100 may comprise a primary chamber gas charging port 135 in fluid communication with the primary gas chamber 130. The shock absorber 100 may comprise a secondary chamber gas charging port 145 in hydraulic communication with the secondary gas chamber 140.

[0027] In various embodiments, the impact absorber 100 can be installed on an aircraft landing gear. During a landing event, the shock absorber 100 may be compressed in which the shock absorber piston 120 translates within the shock absorber cylinder 110. During landing, the shock absorber may initially function as a separate gas/fluid shock absorber. single stage, measuring oil through orifice plate 114 and compressing the volume of gas 131 in the primary gas chamber 130. Compression of the primary gas chamber 130 may continue until the pressure in the primary gas chamber 130 is equal to or greater than the pressure of the gas volume 141 within the secondary gas chamber 140. As illustrated in FIG. 2, this occurs at a shock absorber stroke 194 (i.e. ) between zero and the maximum stroke of the shock absorber, . The separator piston 132 can be translated to the first end 191 as the shock absorber 100 is compressed. Once the secondary gas chamber 140 is activated, further compression of the shock absorber can compress the gas volume 141 in the secondary gas chamber 140, as illustrated in FIG. 3. FIG. 3 illustrates the shock absorber 100 in a fully compressed position or at a maximum shock absorber stroke 195 (i.e., ).

[0028] With reference to FIG. 4A and FIG. 4B, a separate two-stage gas/fluid shock absorber arrangement (impact absorber arrangement) 400 is illustrated, in accordance with various embodiments. The shock absorber arrangement 400 may include an impact absorber 100 and a monitoring system 200. The monitoring system 200 may comprise various sensing elements. The monitoring system 200 may comprise an integrated pressure/temperature sensor 202 installed in the primary gas chamber 130 to measure the pressure and temperature of gas within a primary gas chamber 130. Although described herein as a pressure/temperature sensor integrated 202, it is contemplated herein that a separate pressure sensor and a separate temperature sensor may be used in place of the integrated pressure/temperature sensor. In this regard, the term “pressure/temperature sensor” as used herein may refer to an integrated pressure/temperature sensor or to separate pressure and temperature sensors. The monitoring system 200 may comprise a position sensor (also referred to herein as a travel sensor) 206 configured to directly or indirectly measure the shock absorber 258 . In this regard, sensors can measure various parameters and provide measurements to a monitoring algorithm.

[0029] The integrated pressure/temperature sensor 202 can measure the gas pressure of the primary chamber 250 and primary chamber gas temperature 252 . The stroke sensor 206 can measure the stroke of the shock absorber 258 . The gas pressure of the primary chamber, , the gas temperature of the primary chamber, and the impact course may be referred to in this document as sensor readings (e.g. primary chamber gas pressure sensor reading).

[0030] The monitoring system 200 can be designed assuming that the sensors comprise a minimum sampling frequency between 10 Hz and 1000 Hz according to various embodiments, between 60 Hz and 200 Hz according to various embodiments, or about of 100 Hz, according to various embodiments, wherein the term “about” in this regard may mean ± 20 Hz.

[0031] With reference to FIG. 4A, the monitoring system 200 may comprise a controller 201 and a non-transitory tangible memory 208 configured to communicate with the controller 201. The non-transitory tangible memory 208 may have instructions stored therein that, in response to execution by the controller 201, cause controller 201 to perform various operations as described in this document. The monitoring system 200 may comprise a visual display 270. The visual display 270 may be in electronic communication with the controller 201. As described herein, the controller 201 may issue or send a maintenance message 272. The maintenance message 272 may be displayed on visual display 270. In various embodiments, maintenance message 272 may comprise an indication of an amount of oil or gas in shock absorber 100. In various embodiments, maintenance message 272 may comprise a current signal and/or or tension. Controller 201 may be in electronic communication with integrated pressure/temperature sensor 202. FIG. 4B illustrates the monitoring system 200 in more detail.

[0032] In various embodiments, with reference to FIG. 4B, the monitoring system 200 may comprise a recorder 210, an entry detector 220, a counter 225, an integrity monitor 230, and/or a data profiler 240. The recorder 210, the landing detector 220, the counter 225 , the health monitor 230 and/or the data recorder 240 may comprise instructions stored in a tangible, non-transitory memory 208 (see FIG. 4A). The recorder 210, the landing detector 220, the counter 225, the health monitor 230 and/or the data recorder 240 may be implemented in one or more controllers (e.g., controller 201 of Figure 4A). In this regard, controller 201 (see Figure 4A) may comprise one or more controllers. For example, a first controller (e.g., recorder 210) may receive information from the sensor and a second controller (e.g., health monitor 230) may perform calculations as described herein.

[0033] In various embodiments, recorder 210 may receive gas pressure from primary chamber 250 , primary chamber gas temperature 252 and shock absorber stroke 258 and write them to a matrix that holds the readings for a predetermined period of time, such as 15 seconds, for example. A new set of writes can be added to the top of the array and the oldest set of data can be dropped from the bottom of the array to keep the length of the array constant. At any instant, recorder 210 may export the matrix comprising the last set of data recorded during the predetermined period of time to landing detector 220. Recorder 210 may receive sensor readings in real time or at a later time.

[0034] At startup when the length of the data matrix 214 is not equivalent to 15 seconds (adjustable parameter), the recorder 210 may send a false detection status signal 212 to the landing detector 220 to prevent the landing detector from 220 use the incomplete matrix. Once 15 seconds (adjustable parameter) of measurement are available, the detection state signal 212 may become true to allow the landing detector 220 to use the measurements.

[0035] In various embodiments, the landing detector 220 may receive the data set 214 and check the array against the following set of criteria: first, that the minimum stroke in the array is less than a minimum dimension, such as 0.2 inches (adjustable parameter), second, that the maximum trace in the matrix is greater than a maximum dimension, such as 5” (adjustable parameter), third, that the trace for the first five (5) seconds of the matrix is smaller than the minimum dimension and fourth, that the maximum trace in the first ten (10) seconds (adjustable parameter) of the matrix is greater than a limiting dimension, such as 4” (adjustable parameter).

[0036] The first two criteria can ensure that the data set is associated with a landing or takeoff or any other event that caused the shock absorber to move between 0.2” to 5” (adjustable parameters). The third criterion can ensure that the data set is associated with a landing, such as the first five (5) seconds that the shock absorber was fully extended. The fourth criterion can ensure that the selected set of data also includes 5 seconds of measurement after compression. It is contemplated herein that the parameters of the algorithm may be adjusted according to various embodiments, e.g., may be further adjusted. If the data matrix 214 meets all of these criteria, it is classified as a landing event and exported to the health monitor 230. A signal 227 may also be sent to the health monitor 230 indicating that the data matrix 214 satisfies all the above criteria. A counter 225 may also be started to prevent the landing detector 220 from receiving any new array of measurements for a predetermined duration, such as five (5) minutes (adjustable parameter). This can relax the need for a high-speed processor for health monitoring purposes. If the data array 214 does not meet all criteria, the landing detector 220 may disregard the array and wait for the new data set.

[0037] In various embodiments, health monitor 230 may receive data set 214 that includes various sensor measurements. In various embodiments, sensor measurements may include primary chamber gas pressure 250 , primary chamber gas temperature 252 and/or shock absorber stroke 258 . The data array 214 may be received by the health monitor 230 for a predetermined period of time, such as 15 seconds, for example.

[0038] With reference to FIG. 4C, a portion of the monitoring system 200 is illustrated with a landing detector 260. In this regard, in addition to the landing detector 220, the monitoring system 200 may further comprise the takeoff detector 260. It may be desirable to ensure that the readings of sensors are available when the shock absorber 100 is in the fully extended position, as illustrated in FIG. 1. Thus, liftoff detector 260 may be provided to detect a liftoff event. After takeoff, the shock absorber 100 may be in a fully extended position. In this regard, sensor readings taken after takeoff may include values corresponding to a shock absorber stroke of zero (0). In this regard, monitoring system 200 may use sensor readings from data matrix 264 for calculations using data corresponding to a shock absorber stroke of zero (0), as described herein.

[0039] The takeoff detector 260 may function similarly to the landing detector 220, but using different criteria to examine the course sensor readings to determine the takeoff event. A data array 264 may be sent from recorder 210 to liftoff detector 260. Likewise, data set 264 may be sent to health monitor 230. Data set 264 may be similar to data set 214, as described in FIG. 4B. In this regard, at initialization when the length of the data matrix 264 is not equivalent to a predetermined duration, such as 15 seconds, for example, the recorder 210 may send a false detection status signal 212 to the takeoff detector 260 to prevent the takeoff detector 260 from using the incomplete array. Once the predetermined measurement duration is available, the detection state signal 212 may turn true to allow the liftoff detector 260 to use the measurements in the data matrix 264.

[0040] In various embodiments, the takeoff detector 260 may receive the data set 264 and verify the arrangement against the following set of criteria: first, that the minimum stroke in the array is less than a minimum dimension (i.e., ), such as 0.2” (adjustable parameter), second, that the maximum trace in the matrix is greater than the maximum dimension (i.e. ), such as 5” (adjustable parameter), third, that the stroke for the first five (5) seconds of the array is greater than the maximum dimension (i.e. ) and fourth, that the minimum stroke in the first ten (10) seconds (adjustable parameter) of the die is less than the minimum dimension (i.e. ).

[0041] The first two criteria can ensure that the data set is associated with a landing or takeoff or any other event that caused the shock absorber to move between 0.2” to 5” (adjustable parameters). The third criterion can ensure that the data set is associated with a takeoff because in the first five (5) seconds of data, the shock absorber is compressed to a shock absorber stroke greater than . The fourth criterion can ensure that the selected set of data also includes 5 seconds of measurement after takeoff. It is contemplated herein that the parameters of the algorithm may be adjusted according to various embodiments. If the data matrix 264 meets all of these criteria, it is classified as a liftoff event and exported to the health monitor 230. A signal 267 may also be sent to the health monitor 230 indicating that the data matrix 264 satisfies all the above criteria. A counter 265 may also be started to prevent the takeoff detector 260 from receiving any new array of measurements for a predetermined duration, such as five (5) minutes (adjustable parameter). This can relax the need for a high-speed processor for health monitoring purposes. If the data array 264 does not meet all criteria, the liftoff detector 260 may disregard the array and wait for the new data set.

Determination of oil volume:

[0042] In various embodiments, the volume of oil 133 can be determined via the integrity monitor 230. With combined reference to FIG. 4B and FIG. 5A, at the beginning of compression of shock absorber 100, the pressure within the primary gas chamber 130 is less than the pressure within the secondary gas chamber 140. As compression continues, the primary chamber gas pressure increases and may exceed the secondary chamber gas pressure. Once the primary chamber gas pressure exceeds the secondary chamber gas pressure, the secondary gas chamber 140 may be activated and further compression of the shock mount 100 may cause compression of the primary gas chamber 130 and the secondary gas chamber 140. The monitoring system 200 may utilize the measured dynamic air suspension curve 502 of the primary gas chamber 130, prior to activation of the secondary chamber, to determine the volume of oil 151 in the oil chamber 150. In the first step compression, the shock absorber functions as a separate two-stage gas/fluid shock absorber with a known initial internal volume and the slope of the airflow curve 502 depends only on the volume of oil in the oil chamber 150. However , because the pressure of the secondary gas chamber 140 may not be measured, the portion of the spring corresponding to the first compression phase may not be directly established. The stroke of the shock absorber, in which the secondary gas chamber 140 is activated, directly depends on the pressure of the secondary gas chamber 140, which is not measured and remains unknown to the algorithm. In this regard, when the secondary gas chamber 140 is activated, the slope of the curve of the air stream 502 versus the stroke of the shock absorber may decrease. Thus, the algorithm can indirectly determine the portion of the spring that corresponds to the initial phase of compression by monitoring the slope of the airflow curve 502 versus the stroke of the shock absorber.

[0043] In various embodiments, the monitoring system 200 may calculate a nominal secondary chamber pressure of the secondary gas chamber 140, adjusted for temperature, as follows:

[0044] Then, the monitoring system 200 can determine the stroke of the shock absorber (i.e., ) associated with pressure (i.e. ) of the secondary gas chamber 140 using the airflow curve 502. It is worth noting that the estimated activation stroke (i.e. ) is just a starting point for the algorithm. The actual activation stroke may differ from this estimated value, as shown in FIG. 5A. The true activation stroke may be the stroke at which the pressure of the secondary gas chamber 140 begins to change.

[0045] If the pressure in the primary gas chamber 130 remains below during a landing event and cannot be defined, it may be determined that either the compression ratio is not high enough or that the secondary gas chamber 140 has suffered a significant loss of pressure. In this case, the monitoring system 200 may stop and a maintenance message may be recorded in the data logger 240.

[0046] Once the nominal pressure of the secondary gas chamber 140 has been determined, the inflation pressure of the primary chamber in the fully extended position (i.e., ) or near the fully extended position, the temperature of the primary chamber at the fully extended position (i.e. ) or near the fully extended position, the nominal pressure of the secondary gas chamber 140, adjusted for temperature (i.e., and the impact course on (that is, ) may be stored for use by monitoring system 200 to determine oil volume 151.

[0047] With combined reference to FIG. 4B and FIG. 6, monitoring system 200 may utilize a dynamic spring model 610 together with a numerical optimization method 620 to estimate the volume of oil 151 in oil chamber 150. In this regard, FIG. 6 illustrates an algorithm 600 for estimating the volume of oil 151 in the oil chamber 150. The dynamic spring model 610 can generate an accurate estimate of the transient gas pressure for a separate two-stage gas/fluid shock absorber for a volume of displacement, if the oil volume, initial temperature, initial gas pressure, and initial total internal volume are known. However, because oil volume is required for the model to function, algorithm 600 provides an initial estimate for oil volume (i.e. ), calculates the pressure in and compares the pressure with the pressure measured in . In other words, the health monitor 230 can use inflation pressure from the primary chamber in the fully extended position (i.e., ), the temperature of the primary chamber in the fully extended position (i.e. ), the displacement volume of the primary gas chamber 130 in (that is, ), the total volume of the primary gas chamber 130 and the oil chamber 150 (i.e., ) and an initial estimate for the volume of oil in oil chamber 150 (i.e., ), for example 10 cubic inches (163.87 cm3) and can calculate the primary chamber gas pressure in .

[0048] A numerical, gradient-free, single-variable optimization technique such as Bisection or Line Search can be used to adjust the initial estimate for oil volume so that the difference between the primary gas chamber pressure (that is, ), (see FIG. 5A) and the estimated primary gas chamber pressure at (that is, ) is minimized. In various embodiments, the nominal oil volume value can be used as the initial estimate for the oil volume, which can improve the optimization convergence speed. A block diagram of the algorithm 600, described above, for determining the shock absorber oil volume is provided in FIG. 6.

[0049] The optimization loop can continue until the absolute difference between the estimated pressure and the measured pressure in is less than or equal to a pre-determined limit as follows:

[0050] When equation 2 is satisfied, the last estimate for the oil volume can be recorded as the first estimate of the volume of oil 151 within the oil chamber 150 at the stroke of the zero shock absorber. I.e:

[0051] Referring to FIG 5A, if a significant loss of pressure from the secondary gas chamber 140 has not occurred, may be shorter than the actual activation stroke due to the effects of the inertia of the separator piston 132 on the pressure versus the stroke profile (i.e., curve 502 of the primary gas chamber 130) and equation 3 may generate an accurate estimate of the volume of oil 151 because the pressure versus stroke values used to determine the oil volume are associated with the first compression phase in which the secondary gas chamber 140 is not activated. However, if a significant pressure loss occurs in the secondary gas chamber 140 (e.g., a pressure loss greater than 25%), the actual activation stroke may be less than , in which case equation 3 will underestimate the volume of oil in oil chamber 150. For example, FIG. 5A illustrates a scenario in which a significant loss of pressure from the secondary gas chamber 140 did not occur, while FIG. 5B illustrates a scenario in which a significant loss of pressure has occurred in the secondary gas chamber 140. In FIG. 5B, the actual pressure in the secondary gas chamber 140 is much lower than the nominal pressure. In this case, the actual activation stroke is smaller than the estimated activation stroke .

[0052] In order to ensure that a loss in gas pressure in the secondary gas chamber 140 does not cause erroneous results, the monitoring system 200 can estimate the volume of oil in the oil chamber 150 based on the gas pressure in the secondary gas chamber 140. primary gas 130, as described below.

[0053] With combined reference to FIG. 4B and FIG. 5C, a second pressure for the primary gas chamber 130 may be determined. The second pressure may be a predetermined value (ΔP) less than . For example, the predetermined value (ΔP) can be 100 psi (689.5 kPa) or any other predetermined pressure value. The stroke associated with the second pressure value along the dynamic spring curve 502 can be . With further reference to FIG. 6, a second estimate for the oil volume can be made using algorithm 600. In this regard, the health monitor 230 can use the inflation pressure of the primary chamber in the fully extended position (i.e. ), the temperature of the primary chamber in the fully extended position (i.e. ), the displacement volume of the primary gas chamber 130 in (that is, ), the total volume of the primary gas chamber 130 and the oil chamber 150 (i.e., ) and an initial estimate for the volume of oil in oil chamber 150 (i.e., ) and can calculate the primary chamber gas pressure in . In this regard, although illustrated as being estimated at in FIG. 6, algorithm 600 can also estimate pressure in . Using algorithm 600, as described above, the second estimate for oil volume 151 is made as follows:

[0054] If is bigger than , a third point on the primary chamber curve 502 can also be identified using the same method and a third estimate for the oil volume can be calculated. This iteration can continue for “n” times until the following condition is met:

[0055] With reference to FIG. 5C, an illustration of the air stream curve 502 is provided, where four oil volume estimates were made in accordance with the described procedure. An error between every two subsequent oil volume estimates can be calculated as follows:

[0056] For example,

[0057] Then, the volume of oil 151 can be determined using the following method: also where Limit 2 is a predetermined value, such as 5%, for example. For example, if all , the values for (i = 1 to n-1) are below Limit 2, this implies that no significant pressure loss occurred and that the slope of the dynamic spring curve 502 was maintained until at least, . As a result, the first oil volume estimate can be taken as the actual oil volume 151. Said differently,

[0058] However, if there is above Threshold 2, this implies that a significant loss of pressure has occurred in the secondary gas chamber 140 and that the shape of the dynamic spring curve 502 has changed before reaching . As a result, the first estimate of oil volume may not be accurate. In this case, the oil volume will be equal to the estimate of oil volume . If no “x” can be defined, a maintenance message may be recorded in data recorder 240, suggesting a significant loss of pressure in secondary gas chamber 140.

[0059] The method described above can be designed to provide the most accurate volume estimate for the volume of oil 151 in the oil chamber 150. If a significant loss of pressure occurs, the secondary gas chamber 140 can be activated earlier during compression and as a result, the stiffness of shock absorber 100 may be reduced and the slope of the primary gas chamber pressure profile (i.e., curve 502) may change earlier during compression which could potentially bias the volume estimate. of oil using . However, a change in slope can be reflected in oil volume estimates and consequently in . In this regard, the provided method can capture an unexpected change in the slope of the dynamic spring curve 502 and ensure that the oil volume of the shock absorber 151 is estimated based on the pressure profile of the primary gas chamber 130 before the shock chamber 130. secondary gas 140 be activated. This method can prevent an incorrect estimate of the oil volume 151 in the event of a loss of pressure in the secondary gas chamber 140 while providing the most accurate estimate of the oil volume.

Determination of Primary Chamber Gas Level:

[0060] Once the oil volume in the fully extended position is determined, the gas volume of the primary chamber in the fully extended position can be determined as follows: where is the total internal volume of the shock absorber in the fully extended position and is the nominal volume of the secondary chamber when the piston is at the bottom.

[0061] The number of moles of gas in the primary gas chamber 130 of the impact cushion 100 can then be calculated using the following equation: where is the ideal gas constant and is the nitrogen compressibility factor. The calculated number of moles of gas in primary gas chamber 130 can then be recorded on data recorder 240. Although and are described in this document as being measured during a landing event, it is contemplated in this document that they may also be recorded after a takeoff event. In various modalities, It is at any point during a takeoff event (e.g., detected by takeoff detector 260 with momentary reference to FIG. 4C) or a landing event may be used. In this regard, It is are primary chamber gas pressure and temperature, respectively, when the shock absorber 100 is in the fully extended position (or within 25% of the fully extended position) recorded during a landing event or a takeoff event. It is worth mentioning that, instead of the temperature of the primary chamber, , the temperature of the secondary chamber can be used to calculate the number of moles of gas in the primary gas chamber 130.

Determination of Primary Chamber Oil Leak Volume:

[0062] Depending on the sink rate of the aircraft, the dynamic weight on the landing gear, and the shock absorber's internal fluid levels, the primary chamber may or may not achieve a maximum compression stroke (e.g., separator piston 132 may go to the bottom) during a landing event. If the primary chamber does not reach a maximum compression stroke during the landing event, the maximum pressure achieved in the primary chamber will be equal to the maximum pressure in the secondary chamber at the maximum compression stroke. If the primary chamber reaches maximum compression stroke, the secondary chamber pressure continues to increase while the primary chamber pressure drops due to thermal losses. In both conditions, a maximum pressure value for the primary chamber can be found. Furthermore, in both conditions, the secondary chamber pressure will be almost equal to the primary chamber pressure when the primary chamber pressure reaches its maximum value.

[0063] In various embodiments, with combined reference to FIG. 4B and FIG. 5, the monitoring system 200 may determine the minimum pressure (also referred to herein as the minimum primary chamber pressure) of the primary gas chamber 130 during landing (i.e., and the shock stroke associated with pressure (i.e. Since are determined, the total volume of the primary and secondary chambers in can be determined as follows: It is where is the oil mass modulus, is the total internal volume of the shock absorber in the fully extended position and is the area of the piston. is the total volume of the primary and secondary gas chambers on the course at which the primary chamber pressure reaches its maximum level during landing.

[0064] With combined reference to FIG. 4B and FIG. 7, the monitoring system 200 may utilize a dynamic spring model 710 together with a numerical optimization method 720 to estimate the displacement volume of the primary chamber in . In this regard, FIG. 7 illustrates an algorithm 700 for estimating the displacement volume of the primary chamber in . The 710 dynamic spring model can generate an accurate estimate of the transient gas pressure for a two-stage separate gas/fluid shock absorber for a displacement volume, if the oil volume, initial temperature, initial gas pressure and volume initial internal total are known. However, since the displacement volume is necessary for the model to work, the algorithm 700 provides an initial estimate for the displacement volume (i.e., ) , calculates the pressure in and compares the pressure with the pressure measured in In other words, the health monitor 230 may use primary chamber inflation pressure measured in the fully extended position (i.e., , the temperature of the primary chamber in the fully extended position (i.e. , the initial estimate for the displacement volume of the primary gas chamber 130 (i.e., , the total volume of the primary gas chamber 130, calculated by Eq. 5 (i.e., and an oil volume of zero and can calculate the primary chamber gas pressure in

[0065] A gradient-free, single-variable, numerical optimization technique, such as the Bisection or Line Search methods, can be used to adjust the initial estimate of the displacement volume, so that the difference between the chamber pressure primary gas (that is, (see FIG. 5) and the estimated primary gas chamber pressure in (that is, be minimized.

[0066] The optimization loop can continue until the absolute difference between the estimated pressure and the measured pressure in is less than or equal to a pre-determined limit as follows:

[0067] When equation 9 is satisfied, the last estimate for the displacement volume of the primary gas chamber (i.e. can be recorded and the volume of gas in the primary gas chamber 130 can be determined as follows:

[0068] What if is greater than the dead volume of the primary chamber (i.e. No conclusions can be made regarding the possible oil leak in the primary chamber. And if is less than or equal to the primary chamber dead volume, then the primary chamber oil leak volume (also referred to herein as a primary chamber oil leak volume) is estimated as follows:

Secondary Chamber Gas Level Determination:

[0069] Although a direct measurement of the gas pressure in the secondary gas chamber 140 is not available for the monitoring system 200, the method described below can estimate the inflation pressure of the secondary gas chamber 140 in the fully extended position, assuming a No oil leaks from the secondary gas chamber 140. Because the secondary gas chamber 140 has a pressure greater than or equal to the oil chamber during a full operating cycle of the aircraft and is located on top of the oil chamber, leakage is unlikely of oil in the secondary gas chamber 140 and therefore the assumption is considered valid. In various embodiments, with reference to FIG. 4B, the gas level of the secondary gas chamber 140 can be determined. In this step, the relationship between the pressures in the primary gas chamber 130 and the secondary gas chamber 140 is taken advantage of and the gas pressure in the secondary gas chamber 140 follows the is calculated as:

[0070] Then, the monitoring system 200 can calculate the volume of the secondary gas chamber 140 in the course of as follows: and the displacement volume of the secondary gas chamber 140 in can be determined as follows:

[0071] With combined reference to FIG. 4B and FIG. 8, the health monitor 230 may use a dynamic spring model 810 together with a numerical optimization method 820 to estimate the gas pressure in the secondary gas chamber 140. In this regard, FIG. 8 illustrates an algorithm 800 for estimating the inflation pressure of the secondary gas chamber 140, knowing the displacement volume of the secondary gas chamber 140 in (that is, It is assumed that the oil leakage into the secondary chamber is zero and that the temperature of the gas in the secondary gas chamber 140 is the same as the temperature of the gas in the primary gas chamber 130, which is measured by the temperature sensor.

[0072] Integrity monitoring 230 may use the temperature of the primary gas chamber (i.e., the displacement volume of the secondary gas chamber 140 in calculated by equation 16, the nominal volume of the secondary gas chamber 140 with the piston at the bottom (i.e. , a zero oil leak for the secondary gas chamber 140, and an initial guess for the inflation pressure of the secondary gas chamber (i.e., and can calculate the secondary chamber pressure in

[0073] A gradient-free, single-variable, numerical optimization technique such as Bisection or Line Search can be used to adjust the initial inflation pressure estimate such that the difference between the primary gas chamber pressure (that is, and the estimated pressure of the secondary gas chamber (that is, are minimized.

[0074] The optimization loop can continue until the absolute difference between the estimated pressure and the measured pressure in is less than or equal to a predetermined limit as follows:

[0075] When equation 14 is satisfied, the last estimate for inflation pressure (i.e. can be registered.

[0076] The number of moles of gas in the secondary gas chamber 140 of the shock absorber 100 can then be calculated using the following equation: where is the ideal gas constant and is the compressibility factor of nitrogen (or the compressibility factor for the type of gas used in shock absorber 100). The calculated number of moles of gas in the secondary gas chamber 140 can then be recorded in the data recorder 240. and are the secondary chamber inflation pressure and primary chamber temperature, respectively, with the shock absorber 100 in the fully extended position (or within 25% of the fully extended position) associated with a landing or takeoff event.

Determination of the Maintenance Status of the Impact Damper:

[0077] In the next step, the oil volume can be adjusted to a reference temperature, such as 20° C (68° F) using the following thermal model: where is the coefficient of thermal expansion of the oil, is a step of numerical integration and is the temperature of the oil. can be derived from . The oil volume calculated above can be recorded in data logger 240.

[0078] The deviation of the oil volume 151 from the nominal oil volume can be calculated as follows: where is the nominal volume of oil that is known by the algorithm. In various embodiments, the nominal oil volume may be a desired volume of the oil volume 151 of the shock absorber 100. The deviation of the oil volume 151 from the nominal oil volume may be recorded in the data recorder 240.

[0079] In the next step, the estimated oil volume at the reference temperature (output of Eq. 17) can be compared with a plurality of limits, such as four limits, as used in the example herein, to determine whether the volume of estimated oil is acceptable and an appropriate maintenance message may be issued as follows: The issued maintenance message may be recorded in data recorder 240.

[0080] In the next step, the number of moles of gas in the primary gas chamber 130 estimated by Eq. (6) can be compared with the nominal number of moles of gas calculated with the following equation:

[0081] The deviation of the primary chamber gas level from the nominal value can be calculated as follows: The deviation of the primary gas level from the nominal level can be recorded in data recorder 240.

[0082] The estimated number of moles of gas in the primary gas chamber 130 can be compared with a plurality of limits, such as four limits, as used in the example herein, and a suitable maintenance message is issued as follows:

[0083] The issued maintenance message can be recorded in data recorder 240.

[0084] In the next step, the number of moles of gas in the secondary gas chamber 140 estimated by Eq. (14) can be compared with the nominal number of moles of gas calculated with the following equation:

[0085] The deviation of the secondary chamber gas level nominal value can be calculated as follows:

[0086] The deviation of the secondary gas level from the nominal level can be recorded in data recorder 240.

[0087] The estimated number of moles of gas in secondary gas chamber 140 can be compared to four limits (or any other number of limits) and a suitable maintenance message can be issued as follows:

[0088] The issued maintenance message can be recorded in data recorder 240.

[0089] The oil leak volume for the primary gas chamber 130 (calculated by Eq. 13) can be compared with a plurality of limits and a suitable service message can be issued as follows:

[0090] The issued maintenance message can be recorded in data recorder 240.

[0091] With reference to FIG. 9A, a method 900 for monitoring a shock absorber is provided, in accordance with various embodiments. Method 900 includes receiving a plurality of sensor readings (step 910). Method 900 includes calculating a nominal secondary chamber pressure adjusted for a temperature (step 920). Method 900 includes determining a shock absorber stroke associated with the nominal pressure of the secondary chamber (step 925). Method 900 includes calculating a volume of oil in an oil chamber (step 930). Method 900 includes calculating a volume of gas in a primary chamber (step 940). Method 900 includes calculating a number of moles of gas in the primary chamber (step 950). Method 900 includes calculating a volume of oil leaked into the primary chamber (step 960). Method 900 includes calculating a volume of gas in a secondary chamber (step 970). Method 900 includes calculating a secondary chamber inflation pressure (step 980). Method 900 includes calculating a number of moles of gas in the secondary chamber (step 990).

[0092] With combined reference to FIG. 4A, FIG. 4B and FIG. 9A, step 910 may include receiving, by controller 201, primary chamber gas pressure 250, primary chamber gas temperature 252, and/or shock absorber stroke 258. Step 920 may include calculation by the controller 201 using equation 1, as described in this document. Step 925 may include determining by controller 201 using dynamic curve 502 to determine course (i.e. corresponding to as described in this document. In this regard, controller 201 may determine based on the primary chamber temperature sensor reading and the shock absorber stroke sensor reading. Step 930 may include calculating, by controller 201, the volume of oil 151 using algorithm 600 (see FIG. 6), as described herein.

[0093] With further reference to FIG. 9B, step 930 may further include substep 931 through substep 936. In this regard, step 930 may include calculating an estimate of the first oil volume using the nominal pressure of the secondary chamber and the stroke of the shock absorber (substep 931). Substep 931 may include calculation by controller 201 using the 600 algorithm (see FIG. 6) and calculated in step 920 and calculated in step 925 and using equation 3, as described in this document. Step 930 may include calculating a second nominal pressure (substep 932). Substep 932 may include calculation by controller 201 as described in this document. Step 930 may include calculating a second shock absorber stroke associated with the second nominal pressure (substep 933). Substep 933 may include determining by controller 201 using the dynamic spring curve 502 to determine the stroke of the shock absorber (i.e. corresponding to as described in this document. Step 930 may include calculating a second estimate of the oil volume using the second nominal pressure and the second damper stroke (substep 934). Substep 931 may include calculation by controller 201 using the 600 algorithm (see FIG. 6) and calculated in step 920 and calculated in step 925 and using equation 4, as described in this document. Step 930 may include calculating an error between the first oil volume estimate and the second oil volume estimate (substep 935). Substep 935 may include calculation by controller 201 using equation 6, as described in this document. Step 930 may include determining whether the error is less than or equal to a threshold value (substep 936). Substep 936 may include determining whether as described here.

[0094] With combined reference to FIG. 4A, FIG. 4B and FIG. 9A, step 940 may include calculating, by controller 201, the volume of gas 131 in primary gas chamber 130, as described herein. Step 950 may include calculating, by controller 201, a number of moles of gas in primary gas chamber 130 using Eq. 8, as described herein. Step 960 may include calculating, by controller 201, a volume of oil leaked into primary gas chamber 130 (i.e., using equation 13, as described in this document. Step 970 may include calculating, by controller 201, a volume of gas 141 in secondary gas chamber 140, using equation 15, as described herein. Step 980 may include calculating, by controller 201, the inflation pressure of the secondary chamber (i.e., as described herein in relation to FIG. 8 and equations 14 through equation 17. Step 990 may include calculating, by controller 201, a number of moles of gas in secondary gas chamber 140, using equation 23, as described herein.

[0095] Benefits, other advantages and solutions to problems have been described in this document with respect to specific modalities. Furthermore, the connection lines shown in the various figures contained herein are intended to represent examples of functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical links may be present in a practical system. However, the benefits, advantages, solutions to problems and any elements that may cause any benefit, advantage, or solution to occur or occur will not be construed as critical, necessary or essential features or elements of the disclosure.

[0096] The scope of the disclosure is therefore limited by nothing more than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly stated, but rather , “one or more. “It should be understood that, unless specifically indicated otherwise, references to “a,” “an,” and/or “the” may include one or more than one and that reference to an item in the singular may also include the item in the plural. All ratio ranges and limits disclosed in this document can be combined.

[0097] Furthermore, when a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the expression be interpreted as meaning that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

[0098] The steps referred to in any of the method or process descriptions can be performed in any order and are not necessarily limited to the order presented. Furthermore, any reference to the singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Elements and steps in the figures are illustrated for simplicity and clarity and have not necessarily been provided according to any particular sequence. For example, steps that may be performed simultaneously or in a different order are illustrated in the figures to help improve understanding of embodiments of the present disclosure.

[0099] Any reference to connection, fixation, connection or similar may include another possible permanent, removable, temporary, partial and/or complete connection option. Additionally, any reference to no contact (or similar phrases) may also include reduced contact or minimal contact. Surface shading lines may be used throughout figures to designate different parts or areas, but not necessarily to designate the same or different materials. In some cases, reference coordinates may be specific to each figure.

[00100] Systems, methods and apparatus are provided in this document. In the description detailed here, references to “an embodiment”, “an embodiment”, “an exemplary embodiment”, etc., indicate that the described embodiment may include a specific feature, structure, or characteristic, but every embodiment may not necessarily include the specific resource, structure, or characteristic. Furthermore, such phrases do not necessarily refer to the same modality. Additionally, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is alleged to be within the knowledge of those skilled in the art to presuppose such feature, structure, or characteristic in connection with other modalities whether explicitly described or not. After reading the specification, it will be apparent to those versed in the relevant technique(s) how to implement disclosure in alternative modalities.

[00101] Furthermore, no element, component or step of the method in the present disclosure is intended to be dedicated to the public, regardless of whether the element, component or step of the method is expressly recited in the claims. No claim element is intended to invoke 35 USC 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article or apparatus comprising a list of elements does not include only the elements but may include other elements that are not expressly listed or inherent in such process, method, article or apparatus.

Claims (13)

1. Monitoring system for a separate two-stage gas/fluid shock absorber, comprising: a controller (201); and a non-transitory tangible memory (208) configured to communicate with the controller (201), the non-transitory tangible memory (208) with instructions stored therein which, in response to execution by the controller (201), causes the controller (201) performs operations comprising: receiving, by the controller (201), a primary chamber temperature sensor reading from a temperature sensor coupled to a primary chamber of the two-stage separate gas/fluid shock absorber ; receiving, by the controller (201), a primary chamber pressure sensor reading from a pressure sensor coupled to the primary chamber of the two-stage separate gas/fluid shock absorber; receiving, by the controller (201), a reading of the shock absorber travel sensor (206) from a travel sensor; calculating, by the controller (201), a nominal pressure of the secondary chamber based on the reading of the primary chamber temperature sensor; determination, by the controller (201), of an impact shock absorber stroke associated with the nominal pressure of the secondary chamber; calculating, by the controller (201), a volume of oil in an oil chamber (150) of the two-stage separate gas/fluid impact damper based on the stroke of the damper associated with the nominal pressure of the secondary chamber; calculating, by the controller (201), a volume of gas in a primary chamber (130) of the two-stage separate gas/fluid shock absorber based on at least the volume of oil; calculation, by the controller (201), of an inflation pressure of the secondary chamber; calculating, by the controller (201), a volume of oil leaked into the primary chamber of the two-stage separate gas/fluid shock absorber, based on the inflation pressure of the secondary chamber; and comparing, by the controller (201), the volume of oil leaked into the primary chamber (130) with a plurality of limit values; and issuing, by the controller (201), a maintenance message in response to the comparison. 2. Monitoring system according to claim 1, characterized by the fact that the instructions cause the controller (201) to perform additional operations comprising: calculation, by the controller (201), of a number of moles of gas in the chamber two-stage separate gas/fluid shock absorber primary, based at least on the volume of gas in the primary chamber; and preferably wherein the instructions cause the controller (201) to perform additional operations comprising: calculating, by the controller (201), a volume of gas in a second chamber (140) of the gas/fluid shock absorber separated from two steps; and calculating, by the controller (201), a number of moles of gas in the secondary chamber of the two-stage separate gas/fluid shock absorber, based at least on the volume of gas in the secondary chamber. 3. Monitoring system according to claim 2, characterized by the fact that the instructions cause the controller (201) to perform additional operations comprising: calculation, by the controller (201), of a displacement volume of the secondary chamber of the Two-stage separate gas/fluid shock absorber. 4. Monitoring system according to any one of claims 1 to 3, characterized by the fact that the calculation, by the controller (201), of the volume of oil comprises: calculating, by the controller (201), a first estimate of the volume of oil using the nominal secondary chamber pressure and the impact shock absorber stroke associated with the nominal secondary chamber pressure; calculate, by the controller (201), a second nominal pressure of the second secondary chamber; determine, by the controller (201), a second shock absorber stroke associated with the nominal pressure of the secondary chamber; and calculate, by the controller (201), a second estimate of the oil volume using the second nominal pressure of the secondary chamber and the second stroke of the impact damper associated with the nominal pressure of the secondary chamber. 5. Monitoring system according to claim 4, characterized by the fact that the calculation, by the controller (201), of the oil volume comprises: calculating, by the controller (201), an error between the first estimate of the oil volume and the second estimate of the oil volume; and determining, by the controller (201), whether the error is less than or equal to a threshold value; and preferably wherein the controller (201) determines that the oil volume in the oil chamber is the first oil volume estimate in response to the error being less than or equal to the threshold value. 6. Monitoring system according to claim 2, characterized by the fact that the instructions cause the controller (201) to perform additional operations comprising at least one of: comparing, by the controller (201), the volume of oil in the chamber of oil with a plurality of limit values; comparing, by controller (201), the number of moles of gas in the primary chamber with a plurality of threshold values; comparing, by controller (201), the number of moles of gas in the secondary chamber with a plurality of threshold values. 7. Monitoring system according to any one of claims 1 to 6, characterized in that the nominal pressure of the secondary chamber is adjusted according to the reading of the primary chamber temperature sensor. 8. Monitoring system according to any one of claims 1 to 7, characterized by the fact that the controller (201) is in electronic communication with a pressure/temperature sensor for the primary chamber. 9. Monitoring system according to any one of claims 1 to 8, characterized in that the instructions cause the controller (201) to perform additional operations comprising adjusting the volume of oil in the oil chamber at a temperature of reference and/or wherein the instructions cause the controller (201) to perform additional operations comprising calculating, by the controller (201), a deviation of the oil volume in the primary chamber from a nominal oil volume level for the pressure chamber. oil. 10. Two-stage separate gas/fluid shock absorber arrangement, comprising: a two-stage separate gas/fluid shock absorber, wherein the two-stage separate gas/fluid shock absorber comprises: a damper cylinder (110); a damper piston (120) operatively coupled to the damper cylinder (110); an oil chamber (150); a primary gas chamber (130); and a secondary gas chamber (140); a pressure/temperature sensor (202) mounted in the primary gas chamber (130); a stroke sensor (206) mounted on the separate two-stage gas/fluid shock absorber; and a monitoring system as defined in any one of claims 1 to 9, and further comprising: a recorder (210) configured to receive a plurality of sensor readings from at least one of the pressure/temperature sensors (202) and the stroke sensor (206); a landing detector (220) configured to detect a landing event based on a course sensor reading received from the course sensor (206); and an integrity monitor (230) configured to determine a volume of oil in the oil chamber (150), a volume of gas in the primary chamber (130) in the primary gas chamber (130), and a volume of gas in the gas chamber (130) secondary (140). 11. The two-stage separate gas/fluid shock absorber arrangement of claim 10, wherein the monitoring system further comprises a liftoff detector (260) configured to detect a liftoff event based on the reading. of the course sensor received from the course sensor (206), wherein the plurality of sensor readings are recorded after a takeoff event; and preferably wherein the monitoring system further comprises: a counter (225) configured to prevent at least one of the landing detector and the takeoff detector from receiving data from the recorder for a predetermined duration; and a data recorder (240) configured to receive data from the health monitor. 12. A two-stage separate gas/fluid shock absorber arrangement according to claim 10 or 11, wherein the primary gas chamber (130) is separated from the oil chamber (150) by a first piston separator (132) and the secondary gas chamber (140) is separated from the oil chamber (150) by a second separator piston (142). 13. A two-stage separate gas/fluid shock absorber arrangement according to any one of claims 10 to 12, characterized in that the integrity monitor (230): calculates a nominal pressure of the secondary chamber (140); determines a shock absorber stroke associated with the nominal pressure of the secondary chamber (140); and calculates the volume of oil in the oil chamber (150).