GB2586052A - Method of estimating a mass, and other factors, of an aircraft - Google Patents
Method of estimating a mass, and other factors, of an aircraft Download PDFInfo
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- 238000000034 method Methods 0.000 title claims abstract description 57
- 230000001133 acceleration Effects 0.000 claims abstract description 247
- 238000005096 rolling process Methods 0.000 claims abstract description 80
- 241001442234 Cosa Species 0.000 claims description 3
- 238000012804 iterative process Methods 0.000 abstract 1
- 239000000446 fuel Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 2
- 239000002828 fuel tank Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G19/00—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups
- G01G19/02—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for weighing wheeled or rolling bodies, e.g. vehicles
- G01G19/07—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for weighing wheeled or rolling bodies, e.g. vehicles for weighing aircraft
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01G—WEIGHING
- G01G19/00—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups
- G01G19/08—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for incorporation in vehicles
- G01G19/086—Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups for incorporation in vehicles wherein the vehicle mass is dynamically estimated
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Abstract
Method of and apparatus for estimating the mass of an aircraft 100, the method comprising: calculating an expected acceleration along a ground surface, based on an estimated mass; measuring the actual acceleration, optionally with the aircraft driven by a known torque applied to one or more landing wheels, optionally accounting for rolling resistance 142 and ground slope 131; and comparing the actual and expected accelerations. The difference between actual and expected acceleration may be used to improve the estimated mass, optionally with an iterative process of repeatedly updating the estimated mass used until the calculated expected acceleration and actual acceleration converge to within a predefined limit. Independent claims are made to using a similar method for improving estimates of ground slope or rolling resistance, and apparatuses for carrying out these methods. One or more of the apparatuses may be included on an aircraft.
Description
METHOD OF ESTIMATING A MASS AND OTHER FACTORS OF AN AIRCRAFT
BACKGROUND OF THE INVENTION
100011 The present disclosure relates to commercial passenger aircraft and methods for estimating their mass, as well as estimating other factors.
[0002] More particularly, but not exclusively, this invention concerns a method of estimating a mass of an aircraft. The invention also concerns an aircraft mass estimator apparatus, a method of estimating a rolling resistance of an aircraft, an aircraft rolling resistance estimator apparatus, a method of estimating a slope angle of a ground surface an aircraft is on, an aircraft slope angle estimator apparatus and an aircraft.
[0003] Aircraft mass estimation is conventionally done by calculating the sum of the masses of the empty aircraft, the fuel that will be on board, and the payload, made up of cargo and then allowing 90kg per passenger (70kg for the passenger and 20kg for their luggage).
100041 This mass estimation is used, among other things, to manage the balance of the aircraft during flight. For example, the mass estimation can be used to ensure the aircraft is balanced by pumping fuel between the fuel tanks (including those in the central tank, wing tanks and tail tanks) during flight. This changes the centre of gravity of the aircraft. This enables, for example, the aircraft to cruise at its ideal pitch angle whilst using minimal intervention from the elevators to control the pitch. This leads to a fuel saving as the aircraft can fly more economically by not using elevators (that inherently increase the drag of the aircraft). The same applies to controlling the aircraft with the rudder or ailerons.
[0005] However, it may be considered that the mass estimation method above is not as accurate as would be desired, and so the balancing of the aircraft is also not as efficient as would be desired. Hence, the fuel savings are not optimised.
100061 The present invention seeks to mitigate the above-mentioned problems.
Alternatively or additionally, the present invention seeks to provide an improved method of estimating a mass of an aircraft. -2 -
SUMMARY OF THE INVENTION
[0007] The present invention provides, according to a first aspect, a method of estimating a mass of an aircraft, the method comprising the steps of calculating an initial expected acceleration of the aircraft along a ground surface, based upon an initial aircraft mass estimation, measuring an actual acceleration of the aircraft along the ground surface, and comparing the initial expected acceleration to the actual acceleration.
100081 Such a method allows a mass estimation that is more accurate than the initial mass estimation. For example, the comparison of the actual and expected accelerations provides an indication of whether or not the initial estimated mass is similar to the actual mass (i.e. whether or not the initial mass estimation was accurate). This can then be used to establish a better mass estimation.
100091 The measurement of the actual acceleration could be performed by using on board sensors on the aircraft. These sensors are likely to be on the aircraft for other purposes so the use of such sensors does not increase the weight of the aircraft.
[0010] For example, the initial mass estimation may be obtained by the prior art method described in the "Background of the Invention" section.
[0011] Preferably, the method further comprises the steps of providing a second aircraft mass estimation based upon the comparison of the expected acceleration to the actual acceleration described above, calculating a second expected acceleration of the aircraft along the ground surface, based upon the second aircraft mass estimation, and comparing the second expected acceleration to the actual acceleration. In other words, if it is established that the initial mass estimation is dissimilar to the actual mass (because the initial estimated acceleration is dissimilar to the actual acceleration), a second mass estimation of the aircraft can then be provided. This second mass estimation may be chosen to be higher or lower than the initial mass estimation, depending on whether or not the estimated acceleration was higher or lower than the actual acceleration. The second mass estimation may be chosen, based on the size of the difference in expected and actual acceleration. Hence, the indication of whether the initial estimated aircraft -3 -mass is accurate is used to provide a different estimation of the aircraft mass, to then see if this different estimation is more accurate.
[0012] More preferably, the method further comprises the steps of providing a new aircraft mass estimation based upon the comparison of the latest expected acceleration to the actual acceleration, calculating a new expected acceleration of the aircraft along the ground surface, based upon the new aircraft mass estimation, and comparing the new expected acceleration to the actual acceleration. Hence, the indication of whether the second estimated aircraft mass is accurate is used to provide a different estimation of the aircraft mass, to then see if this different estimation is accurate. This can be done iteratively to obtain a more and more accurate mass estimation (as the estimated acceleration converges to the actual acceleration).
100131 Even more preferably, the steps above are repeated until the expected acceleration and actual acceleration have converged to within a set convergence limit. At this point, it is considered that the mass estimation is accurate within a desired limit.
[0014] Preferably, the calculation of the expected acceleration of the aircraft along the ground surface is based upon a driving torque (T) applied to one or more wheels of the aircraft to drive the one or more wheels along the ground surface. Hence, this may provide an accurate measure for the forwards driving force applied to the aircraft.
[0015] The calculation of the expected acceleration of the aircraft along the ground surface may also be based upon a wheel radius (r) of the wheel to which the torque is being applied. For example, T/r is a measure of the driving force applied to the wheel. If more than one wheel is being driven, the (forwards) driving force on the aircraft may be calculated by Ti/ri + T,/r2 + T3/r3 etc. where 1, 2, 3 denotes wheels 1, 2 and 3 being driven.
[0016] Preferably, the calculation of the expected acceleration of the aircraft along the ground surface is based upon an estimated rolling resistance (pt) of the one or more wheels along the ground surface. This may provide a measure for the resistive force of the wheels (including those being driven and those not being driven). In other words, the rolling resistance may be a value that encompasses the (backwards) resistive force on the total number of wheels of the aircraft (i.e. the total rolling resistance of the aircraft). -4 -
[0017] More preferably, the method further comprises the steps of calculating an expected acceleration of the aircraft along the ground surface, based upon an initial rolling resistance estimation, and comparing the expected acceleration to the actual acceleration. For example, the comparison of the actual and expected accelerations provides an indication of whether or not the estimated rolling resistance is similar to the actual rolling resistance (i.e. whether or not the initial rolling resistance estimation was accurate). This can then be used to establish a better rolling resistance estimation.
100181 Preferably, the method further comprises the steps of providing a second rolling resistance estimation based upon the comparison of the expected acceleration to the actual acceleration described above, calculating a second expected acceleration of the aircraft along the ground surface, based upon the second rolling resistance estimation, and comparing the second expected acceleration to the actual acceleration. In other words, if it is established that the initial rolling resistance estimation is dissimilar to the actual rolling resistance (because the estimated acceleration is dissimilar to the actual acceleration), a second rolling resistance estimation of the aircraft can then be provided. This second rolling resistance estimation may be chosen to be higher or lower than the initial rolling resistance estimation, depending on whether or not the estimated acceleration was higher or lower than the actual acceleration. The second rolling resistance estimation may be chosen, based on the size of the difference in expected and actual acceleration. Hence, the indication of whether the initial estimated rolling resistance is accurate is used to provide a different estimation of the rolling resistance, to then see if this different estimation is more accurate.
[0019] More preferably, the method further comprises the steps of providing a new rolling resistance estimation based upon the comparison of the latest expected acceleration to the actual acceleration, calculating a new expected acceleration of the aircraft along the ground surface, based upon the new rolling resistance estimation, and comparing the new expected acceleration to the actual acceleration. Hence, the indication of whether the second estimated rolling resistance is accurate is used to provide a different estimation of the rolling resistance, to then see if this different estimation is -5 -accurate. This can be done iteratively to obtain a more and more accurate rolling resistance estimation (as the estimated acceleration converges to the actual acceleration).
[0020] Even more preferably, the steps above are repeated until the expected acceleration and actual acceleration have converged to within a set convergence limit. At this point, it is considered that the rolling resistance estimation is accurate within a desired limit.
[0021] The steps involved in estimating the rolling resistance may be done after the steps to estimate the aircraft mass.
[0022] Preferably, the calculation of the expected acceleration of the aircraft along the ground surface is based upon an estimated slope angle of the ground surface. This provides for adjusting for any forwards or backwards gravitational force acting on the aircraft, based on the angle of the slope the aircraft is travelling over.
[0023] More preferably, the method further comprises the steps of calculating an expected acceleration of the aircraft along the ground surface, based upon an initial slope angle estimation, and comparing the expected acceleration to the actual acceleration. For example, the comparison of the actual and expected accelerations provides an indication of whether or not the estimated slope angle is similar to the actual slope angle (i.e. whether or not the initial slope angle estimation was accurate). This can then be used to establish a better slope angle estimation.
[0024] Preferably, the method further comprises the steps of providing a second slope angle estimation based upon the comparison of the expected acceleration to the actual acceleration described above, calculating a second expected acceleration of the aircraft along the ground surface, based upon the second slope angle estimation, and comparing the second expected acceleration to the actual acceleration. In other words, if it is established that the initial slope angle estimation is dissimilar to the actual slope angle (because the estimated acceleration is dissimilar to the actual acceleration), a second slope angle estimation of the aircraft can then be provided. This second slope angle estimation may be chosen to be lower or higher than the initial slope angle estimation, depending on whether or not the estimated acceleration was higher or lower than the actual acceleration. The second slope angle estimation may be chosen, based on -6 -the size of the difference in expected and actual acceleration. Hence, the indication of whether the initial estimated slope angle is accurate is used to provide a different estimation of the slope angle, to then see if this different estimation is more accurate.
[0025] More preferably, the method further comprises the steps of providing a new slope angle estimation based upon the comparison of the latest expected acceleration to the actual acceleration, calculating a new expected acceleration of the aircraft along the ground surface, based upon the new slope angle estimation, and comparing the new expected acceleration to the actual acceleration. Hence, the indication of whether the second estimated slope angle is accurate is used to provide a different estimation of the slope angle, to then see if this different estimation is accurate. This can be done iteratively to obtain a more and more accurate slope angle estimation (as the estimated acceleration converges to the actual acceleration).
[0026] Even more preferably, the steps above are repeated until the expected acceleration and actual acceleration have converged to within a set convergence limit. At this point, it is considered that the slope angle estimation is accurate within a desired limit.
100271 The steps involved in estimating the slope angle may be done after the steps to estimate the aircraft mass, and may be done before or after the steps to estimate the rolling resistance.
[0028] Preferably, the estimated acceleration (a) is calculated using the following equation: (T/r) -t mg cosa = m(a -g sing) [0029] where: T is the driving torque applied to one or more wheels of the aircraft r is the radius of the one or more wheels p is the rolling resistance m is the estimated mass of the aircraft g is the gravitational acceleration constant, and a is the slope angle of the ground surface.
100301 The driving torque (T) may be measured in Newton metres (Nm), the radius (r) may be estimated/measured in metres ( m) , the rolling resistance GO is dimensionless, the mass (m) may be estimated in kilograms (kg), the gravitational constant is approximately 9.81 metres/second' (m/s2), and the slope angle (a) may be estimated in degrees (°) or radians.
[0031] In other words, a = (T/rm) -µ g cosa + gsina [0032] If more than one wheel is being driven, the driving force (D) on the aircraft may be calculated by Ti/ri + + T3/r3 etc. where I, 2, 3 denotes wheels 1, 2 and 3 being driven (instead of] ust T/r).
100331 Preferably, the method comprises measuring an actual acceleration of the aircraft along the ground surface at a plurality of instances and wherein the step(s) of comparing the expected acceleration to the actual acceleration involves comparing the expected acceleration at an instance with the measured acceleration at that instance. In other words, the driving torques (T), slope angle (a) and rolling resistance GO estimations or measurements used to calculate the expected acceleration, correspond to the instance when the actual acceleration is measured.
[0034] According to a second aspect, the invention provides an aircraft mass estimator apparatus comprising a number of inputs (including a mass estimation) used to calculate an expected acceleration, an expected acceleration calculator, an actual acceleration input, a comparator, for comparing the expected acceleration and an actual acceleration, and a further estimation generator, for providing a further estimation of the mass, based on the comparison of expected acceleration and actual acceleration.
[0035] According to a third aspect, the invention provides a method of estimating a rolling resistance of an aircraft, the method comprising the steps of calculating an initial expected acceleration of the aircraft along a ground surface, based upon an initial rolling resistance estimation, measuring an actual acceleration of the aircraft along the ground surface, and comparing the initial expected acceleration to the actual acceleration.
100361 This third aspect of a method of estimating a rolling resistance of an aircraft may include any of the features (or equivalent features) described above in relation to the method of estimating a mass of an aircraft.
100371 According to a fourth aspect, the invention provides an aircraft rolling resistance estimator apparatus comprising a number of inputs, including a rolling -8 -resistance estimation, used to calculate an expected acceleration, an expected acceleration calculator, an actual acceleration input, a comparator, for comparing the expected acceleration and an actual acceleration, and a further estimation generator, for providing a further estimation of the rolling resistance, based on the comparison of expected acceleration and actual acceleration.
[0038] This fourth aspect of an aircraft rolling resistance estimator apparatus may include any of the features (or equivalent features) described above in relation to the aircraft mass estimator apparatus.
[0039] According to a fifth aspect, the invention provides a method of estimating a slope angle of a ground surface an aircraft is on, the method comprising the steps of calculating an initial expected acceleration of the aircraft along the ground surface, based upon an initial slope angle estimation, measuring an actual acceleration of the aircraft along the ground surface, and comparing the initial expected acceleration to the actual acceleration.
[0040] This fifth aspect of a method of estimating a slope angle of an aircraft may include any of the features (or equivalent features) described above in relation to the method of estimating a mass of an aircraft.
[0041] According to a sixth aspect, the invention provides an aircraft slope angle estimator apparatus comprising a number of inputs, including a slope angle estimation, used to calculate an expected acceleration, an expected acceleration calculator, an actual acceleration input, a comparator, for comparing the expected acceleration and an actual acceleration, and a further estimation generator, for providing a further estimation of the slope angle, based on the comparison of expected acceleration and actual acceleration.
[0042] This sixth aspect of an aircraft slope angle estimator apparatus may include any of the features (or equivalent features) described above in relation to the aircraft mass estimator apparatus.
100431 According to a seventh aspect, the invention provides an aircraft comprising the aircraft mass estimator apparatus, aircraft rolling resistance estimator apparatus and/or aircraft slope angle estimator apparatus described above. -9 -
[0044] It will of course be appreciated that features described in relation to one aspect of the present invention may be incorporated into other aspects of the present invention. For example, the method of the invention may incorporate any of the features described with reference to the apparatus of the invention and vice versa.
DESCRIPTION OF THE DRAWINGS
[0045] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which: [0046] Figure 1 shows a side view of an aircraft according to a first embodiment of the invention; and [0047] Figure 2 shows a schematic view of an aircraft mass estimator on board the aircraft of Figure 1.
DETAILED DESCRIPTION
[0048] Figure I shows a side view of an aircraft I 00 according to a first embodiment of the invention.
100491 The aircraft 100 is on a ground surface 130, which is at a slope angle (a) 131.
Here, the slope is downwards and the slope angle is positive, and is 1 degree (°). The slope angle could also be negative, to indicate an upward slope.
100501 The aircraft 100 is provided with two main landing gear 110 and a nose landing gear 120. The main landing gear 110 comprises four wheels; on the left main landing gear an outer wheel (wheel 1) labelled 111, and an inner wheel (wheel 2), not shown, and on the right main landing gear an inner wheel (wheel 3), not shown, and an outer wheel (wheel 4), not shown. For the aircraft shown, the two inner main landing gear wheels (i.e. wheels 2 and 3) are provided with a landing gear drive system (not shown), such as that described in W02014/023941 such that a driving torque (T) is provided to both of those wheels during taxiing.
[0051] The driving torque provided to wheel 2 is identified as T2 and the driving torque provided to wheel 3 is identified as T.3. The landing gear drive systems provided -10 -monitor the torque provided. The torque for each wheel is approximately 8,000Nm during taxiing but can vary. The radius of the second and third wheels are r2 and r3 respectively. These are both 0.56m [0052] The aircraft has a first estimated mass (miest) that has been estimated using the empty weight, fuel and payload of the aircraft. This first estimation is 80,000kg.
[0053] The forces acting on the aircraft are as follows: a forwards/driving force (identified as D) and shown in Figure 1 by arrow 141.
a backwards/friction force (identified as F) and shown in Figure 1 by arrow a gravitational downwards force (weight, W), shown in Figure 1 by arrow a reaction (normal) force (identified as R) and shown in Figure 1 by arrow 144.
[0054] Figure 2 shows a schematic view of an aircraft mass estimator 200 on board the aircraft 100 of Figure 1.
100551 The aircraft mass estimator 200 receives a number of inputs 210. These inputs are: i) estimated rolling resistance (ii) of the aircraft on the ground 130. The value of this varies depending on the conditions (e.g. wet/dry) and the ground surface 130. The rolling resistance is defined as the ratio of the friction force to the reaction force for the total number of wheels. Here, it is estimated as 0.008.
ii) slope angle (a) of the ground 130. This is estimated or it may be measured using pitch angle sensors on the aircraft 100. As mentioned before, this is 1 degree (°) in this example.
iii) wheel radius values for those wheels being driven (r2 and r3). As mentioned before, these are both 0.56m, in this example.
iv) the thrust provided for each driven wheel (T2 and T3) at a certain point in time. For the purpose of this example, these will both be taken to be 8,000Nm, at the point of time they are measured.
v) a first mass estimation (miesi) of the aircraft. As mentioned before, this is 80,000kg.
[0056] In addition, there is an input 220 of the actual acceleration of the aircraft, measured at the same (or corresponding) point of time as the thrust values in iv).
[0057] The aircraft mass estimator 200 comprises an expected acceleration calculator 230, which uses the inputs 210 to calculate an expected acceleration 231, as follows: [0058] The expected acceleration (a) 231 is equal to the resultant force acting on the aircraft in its direction of travel divided by its mass. From resolving forces based on Figure 1, the resultant force acting along the ground 130 in the forwards direction = D -F + Wsin(a) [0059] The various forces on the aircraft are calculate as follows: The forwards/driving force 141 is calculated as D = T//r2 +T3/r3.
The gravitational downwards force (weight W) 143 is calculated as mg (where g is the gravitational constant = 9.81 m/s2). Based upon the first mass estimation, this is estimated as mlestg.
1'he reaction (normal) force 144 is calculated as R = Wcos(a) = mlestg cos(a). The friction force 142 is calculated as F = µ R = µ mlestg cos(a).
100601 Hence, performing the calculations: - D = (8,000Nm)/(0.56m) + (8,000Nm)/(0.56m) = 28,571 N - W = 80,000kg * 9.81 na,is2 = 784,800 N - R= 80,000kg * 9.81m/s2 * cos (1°) = 784,680 N - F = 0.008 * R = 6,277 N [0061] Hence, the total force acting on the aircraft in the forwards direction is: D -F + Wsin(a) = 28,57 I N -6,277N + I 3,967N = 36,261 N. [0062] Therefore the expected acceleration 231: a = 36,261 N 80,000 kg = 0.453 m/s2.
100631 Taking as one equation: a = (D-F+Wsin(a))/m = (T2/rem) + (T3/r3m) -pg cos(a) + g sin(a).
[0064] This expected acceleration 231 is output to a comparator 240 of the aircraft mass estimator 200. This comparator 240 compares the actual acceleration and the estimated acceleration and outputs a +/-difference value 241 between the two to a further -12 -estimation generator 250 of the aircraft mass estimator 200. Here, the actual acceleration measured by sensors on the aircraft is 0.394/s2. And so the +/-difference value 241 is +0.059 m/s2.
[0065] The further estimation generator 250 uses the value 241 to provide a second estimation 251 of the aircraft mass. In other words, as the estimated acceleration was higher than the actual acceleration, this is an indication that the initial mass estimation was too low compared to the actual aircraft mass. Hence, a second mass estimation 25 I will be higher than the initial mass estimation. For example, it may be 81,000kg.
[0066] This new mass estimation 251 is used for a second estimated acceleration (that may or may not be based on the torque (T) values as before) by the expected acceleration calculator 230. The second estimated acceleration 231 is then compared to the corresponding actual acceleration 220 (i.e. the acceleration at the time of the torque (T) values used). Again, a +/-difference value 241 is calculated by the comparator 240 and fed to the further estimation generator 250 to generate a further estimation, based on the difference value 241 and the previous values of the difference value and the corresponding mass estimations used.
100671 When the actual acceleration is within a set limit of the estimated acceleration, the mass estimate used for that iteration is output 260 as a final mass estimation value. A suitable value for the set limit is 5% (i.e. when the actual acceleration is within 5% of the estimated acceleration).
[0068] Of course, where the slope angle (a) is zero, the calculation is simplified as expected acceleration, a = (D-F)/m (where F = LW) = (T2/r2m) + (T3/r3m) -mg.
[0069] Once the mass estimation has been finalised, it is possible to then optimise the estimation of the rolling resistance (R) in a similar way. If this is done, the aircraft mass estimator 200 (or another estimator device) calculates the expected acceleration using the final mass estimation value and the other input values 210, 220 (including an initial estimation value of the rolling resistance) using the equations above.
100701 This value 231 is then compared to the actual acceleration by the comparator 240 and a +if-difference value 241 calculated. The further estimation generator 250 uses -13 -the value 241 to provide a second estimation 251 of the rolling resistance. If, for example, the estimated acceleration was higher than the actual acceleration, this is an indication that the initial rolling resistance estimation was too low compared to the actual rolling resistance. Hence, a second rolling resistance estimation 251 will be higher than the initial rolling resistance estimation. For example, it may be 0.009.
[0071] Further iterations may occur and the further estimation generator 250 may generate further estimations, based on the difference value 241, the previous values of the difference value and the corresponding rolling resistance estimations used. A final rolling resistance estimation may be output 260 when the difference between the actual and estimated accelerations are within a set limit.
100721 Once the mass estimation has been finalised, it is possible to also optimise the estimation of the slope angle (a) in a similar way. If this is done, the aircraft mass estimator 200 (or another estimator device) calculates the expected acceleration using the final mass estimation value and the other input values 210, 220 (including an initial estimation value of the slope angle) using the equations above.
[0073] This value 231 is then compared to the actual acceleration by the comparator 240 and a +if-difference value 241 calculated. The further estimation generator 250 uses the value 241 to provide a second estimation 251 of the slope angle. If, for example, the estimated acceleration was lower than the actual acceleration, this is an indication that the initial slope angle estimation was too low compared to the actual slope angle. Hence, a second slope angle estimation 251 will be higher than the initial slope angle estimation. For example, it may be 1.02°.
[0074] Further iterations may occur and the further estimation generator 250 may generate further estimations, based on the difference value 241, the previous values of the difference value and the corresponding slope angle estimations used. A final slope angle estimation may be output 260 when the difference between the actual and estimated accelerations are within a set limit.
[0075] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that -14 -the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.
[0076] Of course, any reasonable method for the initial estimation of aircraft mass may be used. Similarly, any reasonable method for the initial estimation of slope angle or rolling resistance may be used. Similarly, any reasonable value of wheel radius (or different wheel radii) may be used.
[0077] In the above example, the values of estimated rolling resistance, slope angle and wheel radius (radii) are input to the aircraft mass estimator 200 as part of inputs 210. However, these values may not change as the driving torque changes and so, especially in the case of wheel radius (radii), these may not be input at all, and may instead be known by the aircraft mass estimator 200.
100781 Any number of, and different, wheels of the aircraft (including outer wheels and/or nose landing gear wheels) may be provided with a landing gear drive system. For the wheels that are driven, the aircraft mass estimator 200 needs to know an estimated wheel radius, as well as the driving torque (T) value of each wheel.
[0079] A suitable aircraft rolling resistance estimator apparatus or aircraft slope angle estimator apparatus may be provided that works in essentially the same way as the aircraft mass estimator 200 described above.
[0080] For a rolling resistance estimator apparatus, the inputs 210 may be: i) slope angle (a) of the ground 130. This is estimated or it may be measured using pitch angle sensors on the aircraft 100. As mentioned before, this is 1 degree (°) in this example.
ii) wheel radius values for those wheels being driven (r2 and r3). As mentioned before, these are both 0.56m, in this example.
iii) the thrust provided for each driven wheel (T, and T3) at a certain point in time. For the purpose of this example, these will both be taken to be 8,000Nm, at the point of time they are measured.
iv) a mass estimation of the aircraft. As mentioned before, this is 80,000kg.
v) an initial estimated rolling resistance GO of the aircraft on the ground 130. Here, it is estimated as 0.008.
-15 - [0081] There is also an input 220 of the actual acceleration of the aircraft, measured at the same (or corresponding) point of time as the thrust values in iii).
[0082] The aircraft rolling resistance estimator comprises an expected acceleration calculator 230, which uses the inputs 210 to calculate an expected acceleration 231, as described above.
[0083] This expected acceleration 231 is output to a comparator 240 of the aircraft rolling resistance estimator. This comparator 240 compares the actual acceleration and the estimated acceleration and outputs a +/-difference value 241 between the two to a further estimation generator 250 of the aircraft rolling resistance estimator. Here, the actual acceleration measured by sensors on the aircraft is 0.394/s2. And so the difference value 241 is +0.059 m/s'.
100841 The further estimation generator 250 uses the value 241 to provide a second estimation 251 of the aircraft rolling resistance. In other words, as the estimated acceleration was higher than the actual acceleration, this is an indication that the initial rolling resistance estimation was too low compared to the actual aircraft rolling resistance. Hence, a second rolling resistance estimation 251 will be higher than the initial rolling resistance estimation. For example, it may be 0.009.
[0085] This new rolling resistance estimation 251 is used for a second estimated acceleration (that may or may not be based on the torque (T) values as before) by the expected acceleration calculator 230. The second estimated acceleration 231 is then compared to the corresponding actual acceleration 220 (i.e. the acceleration at the time of the torque (T) values used). Again, a +/-difference value 241 is calculated by the comparator 240 and fed to the further estimation generator 250 to generate a further estimation, based on the difference value 241 and the previous values of the difference value and the corresponding rolling resistance estimations used.
100861 When the actual acceleration is within a set limit of the estimated acceleration, the rolling resistance estimate used for that iteration is output 260 as a final rolling resistance estimation value. A suitable value for the set limit is 5% (i.e. when the actual acceleration is within 5% of the estimated acceleration).
100871 For a slope angle estimator apparatus, the inputs 210 may be: -16 -i) estimated rolling resistance (ii) of the aircraft on the ground 130. The value of this varies depending on the conditions (e.g. wetdry) and the ground surface 130. The rolling resistance is defined as the ratio of the friction force to the reaction force for the total number of wheels. Here, it is estimated as 0.008.
ii) wheel radius values for those wheels being driven (r2 and r3). As mentioned before, these are both 0.56m, in this example.
iii) the thrust provided for each driven wheel (T, and T3) at a certain point in time. For the purpose of this example, these will both be taken to be 8,000Nm, at the point of time they are measured.
iv) a mass estimation of the aircraft. As mentioned before, this is 80,000kg.
v) an initial estimated slope angle (a) of the ground 130. This is 1 degree (°) in this example.
[0088] There is also an input 220 of the actual acceleration of the aircraft, measured at the same (or corresponding) point of time as the thrust values in iii).
[0089] The aircraft slope angle estimator comprises an expected acceleration calculator 230, which uses the inputs 210 to calculate an expected acceleration 231, as described above.
[0090] This expected acceleration 231 is output to a comparator 240 of the aircraft slope angle estimator. This comparator 240 compares the actual acceleration and the estimated acceleration and outputs a +/I difference value 241 between the two to a further estimation generator 250 of the aircraft slope angle estimator. Here, the actual acceleration measured by sensors on the aircraft is 0.394/s2. And so the +7-difference value 241 is +0.059 m/s2.
[0091] The further estimation generator 250 uses the value 241 to provide a second estimation 25 I of the aircraft slope angle. In other words, as the estimated acceleration was higher than the actual acceleration, this is an indication that the initial slope angle estimation was too high compared to the actual aircraft slope angle. Hence, a second slope angle estimation 251 will be lower than the initial slope angle estimation. For example, it may be 0.90°.
-17 - [0092] This new slope angle estimation 251 is used for a second estimated acceleration (that may or may not be based on the torque (T) values as before) by the expected acceleration calculator 230. The second estimated acceleration 231 is then compared to the corresponding actual acceleration 220 (i.e. the acceleration at the time of the torque (T) values used). Again, a +/-difference value 241 is calculated by the comparator 240 and fed to the further estimation generator 250 to generate a further estimation, based on the difference value 241 and the previous values of the difference value and the corresponding slope angle estimations used.
[0093] When the actual acceleration is within a set limit of the estimated acceleration, the slope angle estimate used for that iteration is output 260 as a final slope angle estimation value. A suitable value for the set limit is 5% (i.e. when the actual acceleration is within 5% of the estimated acceleration).
[0094] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.
[0095] It should be noted that throughout this specification, "or" should be interpreted as "and/or".
Claims (17)
- -18 -CLAIMSA method of estimating a mass of an aircraft, the method comprising the steps of: i) calculating an initial expected acceleration of the aircraft along a ground surface, based upon an initial aircraft mass estimation, ii) measuring an actual acceleration of the aircraft along the ground surface, and) comparing the initial expected acceleration to the actual acceleration.
- 2. A method of estimating a mass of an aircraft, as claimed in claim 1, wherein the method further comprises the steps of: iv) providing a second aircraft mass estimation based upon the comparison of the expected acceleration to the actual acceleration in step i), v) calculating a second expected acceleration of the aircraft along the ground surface, based upon the second aircraft mass estimation, and vi) comparing the second expected acceleration to the actual acceleration.
- 3. A method of estimating a mass of an aircraft, as claimed in claim 2, wherein the method further comprises the steps of: vii) providing a new aircraft mass estimation based upon the comparison of the latest expected acceleration to the actual acceleration, viii) calculating a new expected acceleration of the aircraft along the ground surface, based upon the new aircraft mass estimation, and ix) comparing the new expected acceleration to the actual acceleration.
- -19 - 4. A method of estimating a mass of an aircraft, as claimed in claim 3, wherein the steps of claim 3 are repeated until the expected acceleration and actual acceleration have converged to within a set convergence limit.
- 5. A method of estimating a mass of an aircraft, as claimed in any preceding claim, wherein the calculation of the expected acceleration of the aircraft along the ground surface is based upon a driving torque applied to one or more wheels of the aircraft to drive the one or more wheels along the ground surface.
- 6. A method of estimating a mass of an aircraft, as claimed in any preceding claim, wherein the calculation of the expected acceleration of the aircraft along the ground surface is based upon an estimated rolling resistance of the one or more wheels along the ground surface.
- 7. A method of estimating a mass of an aircraft, as claimed in claim 6, wherein the method further comprises the steps of: - calculating an expected acceleration of the aircraft along the ground surface, based upon an initial rolling resistance estimation, and - comparing the expected acceleration to the actual acceleration.
- 8. A method of estimating a mass of an aircraft, as claimed in any preceding claim, wherein the calculation of the expected acceleration of the aircraft along the ground surface is based upon an estimated slope angle of the ground surface.
- 9. A method of estimating a mass of an aircraft, as claimed in claim 10, wherein the method further comprises the steps of: - calculating an expected acceleration of the aircraft along the ground surface, based upon an initial slope angle estimation, and - comparing the expected acceleration to the actual acceleration.-20 -
- 10. A method of estimating a mass of an aircraft, as claimed in any preceding claim, wherein the estimated acceleration (a) is calculated using the following equation: Tir -p. mg cosa = m(a -gsina) where: T is the driving torque applied to one or more wheels of the aircraft r is the radius of the one or more wheels u is the rolling resistance m is the estimated mass of the aircraft g is the gravitational acceleration constant a is the slope angle of the ground surface
- 11. A method of estimating a mass of an aircraft, as claimed in any preceding claim, wherein the method comprises measuring an actual acceleration of the aircraft along the ground surface at a plurality of instances and wherein the step(s) of comparing the expected acceleration to the actual acceleration involves comparing the expected acceleration at an instance with the measured acceleration at that instance.
- 12. An aircraft mass estimator apparatus comprising: - a number of inputs, including a mass estimation, used to calculate an expected acceleration, - an expected acceleration calculator, - an actual acceleration input, - a comparator, for comparing the expected acceleration and an actual acceleration, and - a further estimation generator, for providing a further estimation of the mass, based on the comparison of expected acceleration and actual acceleration.-21 -
- 13. A method of estimating a rolling resistance of an aircraft, the method comprising the steps of: i) calculating an initial expected acceleration of the aircraft along a ground surface, based upon an initial rolling resistance estimation, ii) measuring an actual acceleration of the aircraft along the ground surface, and iii) comparing the initial expected acceleration to the actual acceleration.
- 14. An aircraft rolling resistance estimator apparatus comprising: - a number of inputs, including a rolling resistance estimation, used to calculate an expected acceleration, - an expected acceleration calculator, - an actual acceleration input, - a comparator, for comparing the expected acceleration and an actual acceleration, and - a further estimation generator, for providing a further estimation of the rolling resistance, based on the comparison of expected acceleration and actual acceleration.
- 15. A method of estimating a slope angle of a ground surface an aircraft is on, the method comprising the steps of: i) calculating an initial expected acceleration of the aircraft along the ground surface, based upon an initial slope angle estimation, ii) measuring an actual acceleration of the aircraft along the ground surface, and) comparing the initial expected acceleration to the actual acceleration.-22 -
- 16. An aircraft slope angle estimator apparatus comprising: - a number of inputs, including a slope angle estimation, used to calculate an expected acceleration, - an expected acceleration calculator, - an actual acceleration input, - a comparator, for comparing the expected acceleration and an actual acceleration, and - a further estimation generator, for providing a further estimation of the slope angle, based on the comparison of expected acceleration and actual acceleration.
- 17. An aircraft comprising the aircraft mass estimator apparatus of claim 12, aircraft rolling resistance estimator apparatus of claim 14, or the aircraft slope angle estimator apparatus of claim 16.
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| GB1910937.0A GB2586052A (en) | 2019-07-31 | 2019-07-31 | Method of estimating a mass, and other factors, of an aircraft |
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| Application Number | Priority Date | Filing Date | Title |
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| GB1910937.0A GB2586052A (en) | 2019-07-31 | 2019-07-31 | Method of estimating a mass, and other factors, of an aircraft |
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| GB2586052A true GB2586052A (en) | 2021-02-03 |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0082663A2 (en) * | 1981-12-21 | 1983-06-29 | Sperry Corporation | Takeoff weight computer apparatus for aircraft |
| US20160187184A1 (en) * | 2013-08-06 | 2016-06-30 | Lacsop Limited | Method and apparatus for determining the mass of a body |
| EP3367076A1 (en) * | 2017-02-24 | 2018-08-29 | The Boeing Company | Systems and methods for aircraft mass determination |
-
2019
- 2019-07-31 GB GB1910937.0A patent/GB2586052A/en not_active Withdrawn
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0082663A2 (en) * | 1981-12-21 | 1983-06-29 | Sperry Corporation | Takeoff weight computer apparatus for aircraft |
| US20160187184A1 (en) * | 2013-08-06 | 2016-06-30 | Lacsop Limited | Method and apparatus for determining the mass of a body |
| EP3367076A1 (en) * | 2017-02-24 | 2018-08-29 | The Boeing Company | Systems and methods for aircraft mass determination |
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| GB201910937D0 (en) | 2019-09-11 |
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