Method and system for state of charge estimation for aircraft lithium battery packs

Abstract

The application provides a state of charge estimation method and system for an aircraft lithium battery pack. The state of charge estimation method comprises: identifying an operating condition of the aircraft; and in response to the identified operating condition being a continuous leakage current condition, an auxiliary power unit starting condition, or an emergency power supply condition, using current values collected by at least one of a first current sensor and a second current sensor to estimate the state of charge of the lithium battery pack, wherein the first current sensor has a first rated detection range, and the second current sensor has a second rated detection range, an upper limit value of the second rated detection range being greater than or equal to an upper limit value of the first rated detection range.

Description

Technical Field

[0001] This invention relates to the field of aviation, and more specifically, to a method and system for estimating the state of charge of aircraft lithium battery packs. Background Technology

[0002] With the development of lithium battery technology, lithium batteries have been widely used in aircraft due to their advantages such as high output voltage, high energy density, long cycle life, low self-discharge rate, and wide operating temperature range. At the same time, lithium iron phosphate batteries have become the preferred choice for lithium battery selection in aircraft (such as civil aircraft) power supply systems due to their better safety and lower cost.

[0003] State of charge (SOC) is a core parameter for lithium battery operation management. Its estimation accuracy directly affects the battery's lifespan and safety. If the SOC estimation deviation is too large, it will not only cause the remaining power display to jump and reduce the user experience of the crew, but may also cause overcharging and over-discharging risks, resulting in irreversible damage to the battery, and in severe cases, even threatening the flight safety of the aircraft.

[0004] Currently, the ampere-hour integration method is commonly used in engineering for State of Charge (SOC) estimation, which calculates the remaining battery capacity by integrating the current sampling values ​​over time. However, lithium iron phosphate (LFP) batteries have a long plateau period in their discharge characteristic curves, and the voltage amplitudes corresponding to different SOCs are very similar, making it difficult to correct the SOC estimate using the open-circuit voltage method. Furthermore, aircraft lithium batteries operate over a wide range of conditions, with output currents ranging from milliampere-level leakage currents to short-term high currents in the hundreds of amperes. If a single type of current sensor is used for current acquisition, it cannot simultaneously meet the current detection accuracy requirements under all operating conditions. The current sampling error accumulates continuously with each cycle, further exacerbating the deviation in SOC estimation and making it difficult to adapt to the high reliability requirements and airworthiness verification standards of aircraft.

[0005] Current optimization schemes for lithium battery SOC estimation are mostly geared towards ground transportation and general energy storage scenarios, and cannot be directly adapted to the special operating conditions and safety design specifications of aircraft. There is an urgent need for a high-precision SOC estimation scheme suitable for aircraft lithium batteries to ensure the reliability and safety of aircraft lithium batteries. Summary of the Invention

[0006] This summary is provided to introduce, in a simplified form, some concepts that will be further described in the following detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0007] One of the objectives of this invention is to provide a method and system for estimating the state of charge (SOC) of aircraft lithium battery packs. This system is designed to adapt to the wide current range requirements of aircraft lithium batteries, improve the accuracy of current detection under all operating conditions through a differentiated current acquisition architecture, reduce the cumulative error of the ampere-hour integration method, achieve stable and accurate SOC estimation, ensure the reliability and safety of aircraft lithium batteries, and meet the high reliability requirements and airworthiness verification standards in the civil aviation field.

[0008] According to one aspect of the present invention, a method for estimating the state of charge (SOC) of an aircraft lithium battery pack is provided. The SOC estimation method includes: identifying the operating conditions of the aircraft; and, in response to the identified operating conditions being a continuous leakage current condition, an auxiliary power unit start-up condition, or an emergency power supply condition, estimating the SOC of the lithium battery pack using current values ​​collected by at least one of a first current sensor and a second current sensor, wherein the first current sensor has a first rated detection range, and the second current sensor has a second rated detection range, and the upper limit of the second rated detection range is greater than or equal to the upper limit of the first rated detection range.

[0009] In one embodiment of the present invention, identifying the operating condition of an aircraft includes: detecting the aircraft's wheel-mounted signal, the power supply status of the DC emergency busbar, and the current value and current duration of the lithium battery pack; and determining that the identified operating condition is a continuous leakage current condition when the wheel-mounted signal is detected as ground status, the DC emergency busbar loses power supply, and the current value and current duration of the lithium battery pack meet a first threshold condition, wherein the first threshold condition includes a first current threshold and a first duration threshold.

[0010] In one embodiment of the present invention, identifying the operating condition of the aircraft includes: detecting the start signal of the auxiliary power unit, the rotation speed signal of the auxiliary power unit, and the current value of the lithium battery pack; and determining the identified operating condition as the auxiliary power unit start condition when the start signal of the auxiliary power unit is detected to be in an active state, the rotation speed signal of the auxiliary power unit switches from a stopped state to an increasing state, and the current value of the lithium battery pack meets a second threshold condition, wherein the second threshold condition includes a second current threshold.

[0011] In one embodiment of the present invention, identifying the operating condition of an aircraft includes: detecting the aircraft's wheel-mounted signal, the power supply status of the DC main bus, and the current value and current duration of the lithium battery pack; and determining the identified operating condition as an emergency power supply condition when the wheel-mounted signal is detected to be in a non-ground state, the DC main bus loses power supply, and the current value and current duration of the lithium battery pack meet a third threshold condition, wherein the third threshold condition includes a third current threshold and a third duration threshold.

[0012] In one embodiment of the present invention, in response to the identified operating condition being a continuous leakage current condition, the current value collected by the first current sensor is integrated in ampere-hours to calculate the state of charge.

[0013] In one embodiment of the present invention, in response to the identified operating condition being the start-up condition of the auxiliary power unit, the current value collected by the second current sensor is integrated in ampere-hours to calculate the state of charge.

[0014] In one embodiment of the present invention, in response to the identified operating condition being an emergency power supply condition, a fused current is obtained by weighting the current values ​​collected by the first current sensor and the second current sensor, and an ampere-hour integral is performed based on the fused current to calculate the state of charge, wherein the weighting weight of the first current sensor is higher than that of the second current sensor.

[0015] In one embodiment of the present invention, in response to detecting a bidirectional switching of the operating condition between the auxiliary power unit starting condition and other operating conditions, during the window duration of the bidirectional switching, a fused current is calculated by weighting the current values ​​collected by the first current sensor and the second current sensor, and the state of charge is calculated by ampere-hour integration based on the fused current, wherein the weighting weights of the first current sensor and the second current sensor are linearly adjusted with the window duration.

[0016] In a further embodiment of the present invention, when switching into the auxiliary power unit start-up condition, during the first switching window duration, the weighting weight of the first current sensor is linearly reduced from the current value to 0; and when switching out of the auxiliary power unit start-up condition, during the second switching window duration, the weighting weight of the first current sensor is linearly increased from 0 to the target value, wherein the sum of the weighting weight of the first current sensor and the weighting weight of the second current sensor is 1.

[0017] According to another aspect of the present invention, a state-of-charge estimation system for an aircraft lithium battery pack is provided, the state-of-charge estimation system comprising: a first current sensor having a first rated detection range; a second current sensor having a second rated detection range, the upper limit of the second rated detection range being greater than or equal to the upper limit of the first rated detection range; and a battery management system communicatively connected to the first current sensor and the second current sensor, and configured to perform the state-of-charge estimation method of the present invention.

[0018] In one embodiment of the present invention, the first current sensor is a resistive shunt, and the second current sensor is a Hall effect sensor.

[0019] In a further embodiment of the present invention, the first current sensor is disposed outside the lithium battery pack, and the second current sensor is disposed inside the lithium battery pack.

[0020] According to another aspect of the present invention, a non-transient computer-readable medium is provided for storing computer-executable instructions that, when executed by a state-of-charge estimation system, perform the state-of-charge estimation method of the present invention.

[0021] These and other features and advantages will become apparent from the following detailed description and with reference to the accompanying drawings. It should be understood that the foregoing general description and the following detailed description are illustrative only and do not limit the scope of the claims. Attached Figure Description

[0022] To gain a more detailed understanding of the manner in which the features of the present invention are described above, reference can be made to various embodiments to provide a more specific description of the above-briefly summarized aspects, some of which are illustrated in the accompanying drawings. However, it should be noted that the drawings illustrate only certain typical aspects of the invention and should not be considered as limiting its scope, as this description may allow for other equivalent and effective aspects.

[0023] Figure 1 This is a functional block diagram of a state-of-charge estimation system for an aircraft lithium battery pack according to an embodiment of the present invention.

[0024] Figure 2 This is a flowchart of a method for estimating the state of charge of an aircraft lithium battery pack according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the aircraft operating status and current sensor usage logic according to an embodiment of the present invention.

[0026] Figure 4 This is a flowchart of a process for estimating the state of charge of an aircraft lithium battery according to an embodiment of the present invention.

[0027] Figure 5 This is a hardware architecture diagram of a state-of-charge estimation system for aircraft lithium battery packs according to an embodiment of the present invention.

[0028] The accompanying drawings are not drawn to scale. Detailed Implementation

[0029] Embodiments of this disclosure will now be described in more detail with reference to the accompanying drawings. While some embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of this disclosure. It should be understood that the accompanying drawings and embodiments of this disclosure are for illustrative purposes only and are not intended to limit the scope of protection of this disclosure.

[0030] In the description of this disclosure, it should be noted that, unless otherwise stated, "a plurality of" means two or more (including two); the terms "upper," "lower," "left," "right," "inner," "outer," etc., indicating orientation or positional relationships are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the allowable tolerance range. "Parallel" is not parallel in the strict sense, but within the allowable tolerance range.

[0031] The directional terms used in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this disclosure. It should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this disclosure. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] In the description of the embodiments of this disclosure, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0034] Figure 1 A functional block diagram of a state-of-charge estimation system 100 for an aircraft lithium-ion battery pack according to an embodiment of the present invention is shown. It should be noted that... Figure 1 The illustrated state of charge estimation system 100 is merely exemplary and not limiting. The state of charge estimation system of the present invention may include, but is not limited to, systems that can be compared to... Figure 1 The state of charge estimation system 100 shown has more or fewer components.

[0035] like Figure 1As shown, the state-of-charge estimation system 100 may include a first current sensor 110, a second current sensor 120, and a battery management system (BMS) 130. The first current sensor 110 has a first rated detection range, and the second current sensor 120 has a second rated detection range, with the upper limit of the second rated detection range being greater than or equal to the upper limit of the first rated detection range, to adapt to the detection requirements of aircraft lithium batteries under large current range conditions. Those skilled in the art will understand that both types of sensors have multiple series of models with different ranges available. The sensor model selected in this solution prioritizes matching the usage requirements of the corresponding detection environment, and the sensor has the optimal detection accuracy within its own rated detection range. Therefore, by matching the sensor to the corresponding range for the operating conditions, high-precision current acquisition can be achieved in all scenarios.

[0036] For example, the second current sensor can be a non-contact detection device. In high-current detection scenarios, it does not need to be connected in series to the power circuit, and its heat dissipation loss is less than that of contact current detection solutions. Therefore, it can adapt to the long-term stable operation requirements of high-current conditions such as APU startup. By matching the sensor to the corresponding range of operating conditions, high-precision current acquisition can be achieved in all scenarios.

[0037] The battery management system 130 is communicatively connected to the first current sensor 110 and the second current sensor 120, and is configured to execute corresponding state-of-charge estimation methods. Specifically, it can receive measurement data from the two types of current sensors, combine them with aircraft operating condition signals to complete the state-of-charge estimation process, and output an estimated state indication 250, thereby ensuring the reliability and safety of lithium battery operation.

[0038] In one example, the first current sensor 110 can be a resistive shunt, and the second current sensor 120 can be a Hall effect sensor. The resistive shunt is a contact-type current sensing device based on Ohm's law, which calculates the current value by measuring the voltage difference across the device connected in series in the current loop, exhibiting high accuracy for small current detection. The Hall effect sensor is a non-contact current sensing device based on the Hall magnetic effect, which calculates the current value by detecting the magnetic field strength generated by the current, exhibiting good adaptability for large current and high rate of change current detection.

[0039] Based on the performance differences between the two types of sensors, the first current sensor 110 (resistive shunt) achieves a detection accuracy of ±0.1%~±1% (example value) after calibration, supporting mA-level current detection; the second current sensor 120 (Hall effect sensor) has a closed-loop detection accuracy of ±0.2%~±0.5% (example value), suitable for current change rate detection ≥50A / s. It is evident that the advantages and disadvantages of the two types of sensors perfectly match the current detection requirements of the aircraft under three operating conditions. This solution defaults to using the measurement value of the first current sensor to calculate the ampere-hour integral for SOC estimation, which can minimize the cumulative error over long-term operation.

[0040] In one example, the first current sensor 110 can be located outside the lithium battery pack 140, and the second current sensor 120 can be located inside the lithium battery pack 140. For example, the first current sensor 110 can be connected in series between the negative power circuit of the lithium battery pack 140 and the ground terminal (GND). Its installation position can be close to the ground terminal, resulting in low electromagnetic interference and allowing maintenance and replacement without disassembling the battery pack, thus meeting the high maintainability design requirements of aircraft. The second current sensor 120 can be arranged in a ring within the single-cell charge / discharge current circuit inside the lithium battery pack 140. It can perform current detection without being connected in series to the power circuit, providing excellent electrical isolation performance. Depending on the actual layout requirements, the first current sensor can also be located inside the lithium battery pack, and the second current sensor can also be located outside the lithium battery pack. As long as both types of current sensors are connected to the charge / discharge current circuit of the lithium battery pack, the current acquisition function can be achieved. The negative output terminal of the lithium battery pack is directly grounded. Regardless of whether the two types of sensors are located inside or outside the battery pack, installation close to the ground terminal will result in less electromagnetic interference.

[0041] In one example, the input signals of the battery management system 130 also include the aircraft auxiliary power unit (APU) start signal 102, the APU speed signal 104, and the aircraft wheel load (WOW) signal 106, which provide a basis for judgment for operating condition identification.

[0042] In one example, the output of the battery management system 130 can output an estimated state indication signal, transmitting data such as the current state of charge, operating condition, and sensor status to the aircraft avionics system for query by the flight crew or ground staff.

[0043] In one example, the lithium battery pack 140 is a lithium iron phosphate battery pack, containing multiple lithium battery cells 1405 connected in series and parallel. Its power output terminal is connected to external circuits such as the lithium battery charger 150 and the HOT busbar 160 (a hot busbar, i.e., a power busbar that is continuously charged in scenarios such as aircraft shutdown, ground maintenance, and APU startup) via a positive power line. The lithium battery charger 150 is used to manage the charging of the lithium battery pack 140, and its charging control logic can be uniformly scheduled by the power controller 280. The HOT busbar 160 can supply power to the motor controller 170 through the contactor K1. The motor controller 170 drives the APU starter motor M to run. The speed signal of the APU can be obtained by the speed acquisition module and fed back to the battery management system 130. At the same time, the HOT busbar 160 can also supply power to the shutdown load 220. The power output terminal of the lithium battery pack 140 can also be connected to the DC critical bus 180 (i.e., the DC emergency bus) to power the DC critical load 190. The DC critical bus is further connected to the DC bus 260 (i.e., the DC main bus) to power the conventional DC load 210.

[0044] Those skilled in the art will understand that in this invention, "battery" and "battery pack" are different names for the same energy storage device, and are completely equivalent, both referring to an energy storage power supply unit composed of multiple individual battery cells connected in series and parallel, capable of providing electrical energy to external loads. Furthermore, in this invention, "critical DC busbar" and "emergency DC busbar" are different names for the same power supply link, and are completely equivalent: this busbar belongs to the highest priority power supply link for the aircraft, is normally powered by the main generator, and only switches to lithium battery pack power supply when the main power supply system fails. It supplies power to critical safety loads such as flight control, avionics, and emergency lighting, and is the core power supply link ensuring aircraft flight safety; it is not connected to unnecessary conventional loads. Furthermore, "DC busbar" and "DC main busbar" are different names for the same power supply link, and they are completely equivalent: this busbar is the aircraft's conventional power supply link, supplying power to the main generator under normal conditions and covering non-safety-related conventional loads such as cabin lighting and entertainment systems. Its power supply priority is lower than that of the critical DC busbar. Only when the main busbar fails and the aircraft is in the air will the emergency power supply mode of the lithium battery pack be triggered. The status detection signals of both types of busbars are directly connected to the battery management system 130, serving as the core basis for determining operating conditions.

[0045] It is clear that, depending on the actual situation, the above examples can be implemented individually or in combination.

[0046] The system architecture described in this embodiment can reuse the existing hardware configuration of aircraft lithium batteries. It can achieve high-precision state of charge estimation under all operating conditions simply by upgrading the functions of the battery management system 130. It is suitable for the batch deployment needs of new aircraft models and also supports the rapid retrofitting of in-service aircraft models.

[0047] Figure 2 A flowchart of a method 200 for estimating the state of charge of an aircraft lithium battery pack according to an embodiment of the present invention is shown. It should be noted that... Figure 2 The illustrated state of charge estimation method 200 is merely exemplary and not limiting. The state of charge estimation method of the present invention may include more than Figure 2 The number of steps shown may be increased or decreased, or the order in which the steps are executed may be adjusted.

[0048] The state of charge estimation method 200 described in this embodiment can be implemented using the aforementioned state of charge estimation system 100. Relying on the differentiated range coverage characteristics of dual current sensors, it can achieve high-precision current acquisition and state of charge estimation for various operating conditions of aircraft lithium batteries with a wide range. It can be implemented through software logic upgrades of the battery management system (BMS) 130 without the need for additional hardware, thus adapting to the high reliability and high safety design requirements of aircraft.

[0049] like Figure 2 As shown, the state of charge estimation method 200 may include the following steps: In step 202, the aircraft's operating conditions can be identified. This operation can be performed, for example, via the battery management system 130. The operating range of aircraft lithium batteries extends from milliampere-level leakage current to hundred-ampere-level short-term high current, covering a variety of different operating conditions. Moreover, the triggering of these operating conditions is coupled with the overall operating status of the aircraft. This solution combines the existing wheel-mounted signals, APU status signals, and busbar status signals of the aircraft avionics system with the current parameters of the lithium battery pack for joint logic determination. It can achieve accurate identification of three types of operating conditions without the need for additional detection links. Specifically, it can cover typical scenarios such as continuous leakage current conditions, auxiliary power unit (APU) start-up conditions, and emergency power supply conditions.

[0050] In one example, identifying the aircraft's operating condition may include: detecting the aircraft's wheel-mounted (WOW) signal, the power supply status of the critical DC bus (i.e., the DC emergency bus), and the current value and duration of the lithium battery pack 140; and determining the identified operating condition as a continuous leakage current condition when the wheel-mounted signal is detected as ground-based, the critical DC bus (i.e., the DC emergency bus) is out of power, and the current value and duration of the lithium battery pack 140 meet a first threshold condition, wherein the first threshold condition includes a first current threshold and a first duration threshold. Under this condition, the lithium battery pack 140 is in a ground-based, stationary state, with only milliampere-level leakage current. The joint determination of the wheel-mounted signal and the bus status can avoid false triggering and ensure the accuracy of state estimation in leakage current scenarios.

[0051] In one example, identifying the aircraft's operating condition may include: detecting the start signal of the auxiliary power unit (APU), the APU's rotational speed signal, and the current value of the lithium battery pack 140; and determining the identified operating condition as the APU start-up condition when the APU start signal is detected as active, the APU's rotational speed signal switches from a stopped state to an increasing state, and the current value of the lithium battery pack 140 meets a second threshold condition, wherein the second threshold condition includes a second current threshold. Under this condition, the lithium battery pack 140 outputs a short-term high current in the hundreds of amperes. By jointly determining the start signal and rotational speed signal, the short-term high-current discharge scenario can be quickly captured, avoiding detection errors under high current.

[0052] In one example, identifying the aircraft's operating condition may include: detecting the aircraft's wheel-mounted signals, the power supply status of the DC main bus, and the current value and duration of the lithium battery pack 140; and determining the identified operating condition as an emergency power supply condition when the wheel-mounted signals are detected as being in a non-ground state, the DC main bus loses power supply, and the current value and duration of the lithium battery pack 140 meet a third threshold condition, wherein the third threshold condition includes a third current threshold and a third duration threshold. Under this condition, the lithium battery pack 140 supplies power to critical loads on the aircraft. Identifying the airborne status through wheel-mounted signals and combining this with the bus power supply status for joint determination avoids confusion with other ground operating conditions, ensuring power supply reliability in flight scenarios.

[0053] In one example, the determination of the above three types of operating conditions can all adopt multi-signal AND gate logic. The corresponding operating condition will only be triggered when all the determination conditions are met simultaneously, minimizing false judgments and adapting to the high reliability requirements of aircraft. The specific principle of this AND gate determination logic can be referred to in the following sections of this invention. Figure 3 The illustration is as follows.

[0054] In step 204, in response to the identified operating condition being a continuous leakage current condition, an auxiliary power unit start-up condition, or an emergency power supply condition, the state of charge of the lithium battery pack 140 can be estimated using the current value collected by at least one of the first current sensor 110 and the second current sensor 120. The first current sensor 110 has a first rated detection range, and the second current sensor 120 has a second rated detection range, the upper limit of which is greater than or equal to the upper limit of the first rated detection range. This operation can be performed, for example, via the battery management system 130. Adapting the optimal detection sensor to the current characteristics of different operating conditions can simultaneously achieve both low-current accuracy and high-current applicability, reducing the cumulative error of the ampere-hour integration.

[0055] In one example, in response to the identified operating condition being a continuous leakage current condition, the current value collected by the first current sensor 110 can be integrated in ampere-hours to calculate the state of charge (SOC). Under this condition, the current value is extremely small; using the first current sensor 110, which supports high-precision detection at the milliampere level, can reduce sampling errors and avoid SOC estimation drift during long-term static states.

[0056] In one example, in response to the identified operating condition being the auxiliary power unit starting condition, the current value collected by the second current sensor 120 can be integrated in ampere-hours to calculate the state of charge. Under this condition, the current amplitude is large and the rate of change is high. Using the second current sensor 120, which supports high current detection, can avoid the problems of high current heating and temperature drift of the first current sensor 110, and ensure the sampling accuracy under short-term high current.

[0057] In one example, in response to the identified operating condition being an emergency power supply condition, a weighted average current can be calculated from the current values ​​collected by the first current sensor 110 and the second current sensor 120. An ampere-hour integral is then performed based on this weighted average current to calculate the state of charge (SOC). The weighting of the first current sensor 110 is higher than that of the second current sensor 120. Optionally, the sum of their weightings is 1. Under this condition, the current is in a medium amplitude range. Using the more accurate data from the first current sensor 110 as the primary source and the data from the second current sensor 120 as a secondary source maintains high accuracy while improving reliability through dual-sensor verification, thus meeting the independent and dissimilar design requirements of aircraft power supply systems.

[0058] Furthermore, when a change in operating condition is detected, a smooth transition mechanism can be used to avoid current jumps caused by sensor switching, ensuring the continuity and stability of SOC estimation and meeting the design requirements for seamless switching of aircraft systems. It can be understood that the duration of the switching window can be flexibly configured, for example, based on the dynamic response characteristics of the aircraft's lithium battery system, ensuring a smooth transition without introducing additional estimation delays.

[0059] In one example, in response to the detection of a bidirectional switch between the auxiliary power unit (APU) start-up condition and other operating conditions, a fused current can be calculated, for example, by weighting the current values ​​collected by the first current sensor 110 and the second current sensor 120 during a preset bidirectional switching window period. The APU is then integrated in ampere-hours based on the fused current to calculate the state of charge (SOC). The weighting of the first current sensor 110 and the second current sensor 120 is linearly adjusted with the window duration. Those skilled in the art will understand that the bidirectional switching can include two scenarios: first, switching into the APU start-up condition, i.e., switching from either the continuous leakage current condition or the emergency power supply condition to the APU start-up condition; and second, switching out of the APU start-up condition, i.e., switching from the APU start-up condition to either the continuous leakage current condition or the emergency power supply condition. This linear weighted transition within the window duration avoids current step errors caused by direct sensor switching, improving the smoothness of the SOC estimation.

[0060] Optionally, the specific weight adjustment logic can be adaptively matched according to different scenarios of switching into and out of the APU startup condition. For example, when switching into the APU startup condition, during the first switching window period, the weight of the first current sensor 110 can be linearly reduced from its current value to 0 via the battery management system 130; when switching out of the APU startup condition, during the second switching window period, the weight of the first current sensor 110 can be linearly increased from 0 to a target value via the battery management system 130, wherein the sum of the weight of the first current sensor 110 and the weight of the second current sensor 120 is 1. It is understood that those skilled in the art can also adjust the weight sum of the two types of sensors to other values ​​according to actual accuracy requirements, and such adjustments all fall within the protection scope of this invention.

[0061] It is clear that, depending on the actual situation, the above examples can be implemented individually or in combination.

[0062] The state of charge estimation method in this embodiment is designed to meet the differentiated needs of various operating conditions of aircraft lithium batteries. Compared with a single sensor solution, the current detection accuracy can be effectively improved across the entire operating range, the cumulative error of ampere-hour integration is significantly reduced, and the SOC correction cycle of lithium iron phosphate batteries is extended. It is suitable for the batch deployment needs of new aircraft models and also supports the rapid upgrade and transformation of in-service aircraft models.

[0063] To more clearly demonstrate the execution details of the entire process of the operating condition adaptation logic and state of charge estimation of this invention, the following is a schematic diagram of the aircraft operating conditions and the current sensor usage logic. Figure 3 ) and a workflow diagram applicable to the state of charge estimation of aircraft lithium batteries ( Figure 4(Expand for further details.) The lithium battery pack described in the following embodiments is... Figure 1 The lithium battery pack 140 described herein includes a first current sensor, a second current sensor, an aircraft APU start signal, an aircraft WOW signal, and an APU speed signal. Figure 1 The first current sensor 110, the second current sensor 120, the aircraft APU start signal 102, the aircraft WOW signal 106, and the APU speed signal 104 are described in the document.

[0064] It should be made clear that Figure 3 and Figure 4 The logical judgment process and execution steps shown are merely exemplary optional implementation schemes and are not intended to limit the scope of protection of this invention. Those skilled in the art can adaptively adjust the combination of working condition judgment conditions, sensor switching logic, and weighting coefficient values ​​according to actual application scenarios. They can also selectively add or delete some working condition adaptation rules according to the needs of the aircraft model. All such adjustments fall within the protection scope of this invention. In addition, all thresholds, durations, sensor accuracy, weighting coefficients, and other parameters mentioned in the following embodiments are exemplary values. In actual applications, they can be adapted and adjusted according to the lithium battery model, aircraft airworthiness requirements, and working condition requirements.

[0065] Figure 3 This diagram illustrates the logic for aircraft operating conditions and current sensor usage according to an embodiment of the present invention. Specifically, it shows the multi-condition AND gate judgment logic for three typical operating conditions of an aircraft lithium battery. All prerequisite judgment conditions must be met simultaneously to trigger the sensor selection strategy for the corresponding operating condition. This logic can be used with… Figure 2 The corresponding working condition identification method in step 202.

[0066] The judgment logic for the three types of operating conditions is executed independently and in parallel. The optimal current sampling strategy can be switched in real time according to the aircraft's operating status. High-precision current acquisition under all operating conditions can be achieved without adding an additional detection link, which is suitable for the high reliability design requirements of aircraft.

[0067] The first set of AND gate logic 310 is used to determine the continuous leakage current condition. Specifically, when three conditions are simultaneously met—no detected in-flight wheel-on-the-ground (WOW) signal (i.e., the aircraft is on the ground), loss of power supply to the aircraft's critical DC bus (i.e., the DC emergency bus), and the current value I(t) and duration Δt of the lithium battery pack satisfying the first threshold condition (i.e., threshold 1)—the aircraft can be determined to be in a continuous leakage current condition. In this case, the measured value of the first current sensor is used for state of charge estimation. Under this condition, the lithium battery pack is in a ground-based, stationary state, with only milliampere-level leakage current. The joint determination of the wheel-on-the-ground signal and the bus status can avoid false triggering and ensure the accuracy of state estimation in leakage current scenarios.

[0068] The second set of AND gate logic 320 is used to determine the emergency power supply condition. Specifically, when three conditions are simultaneously met—the detection of a wheel-mounted (WOW) signal indicating the aircraft is not on the ground, the detection of a loss of power supply from the aircraft's DC main bus, and the detection that the current value I(t) and duration Δt of the lithium battery pack meet the third threshold condition (i.e., threshold 3)—the aircraft can be determined to be in an emergency power supply condition. In this condition, the state of charge is estimated using the fused measurement values ​​from the first and second current sensors. Under this condition, the lithium battery pack supplies power to critical loads on the aircraft. By identifying the in-flight status through the wheel-mounted signal and combining it with the bus power supply status for joint determination, confusion with other ground conditions can be avoided, ensuring the reliability of power supply in flight scenarios.

[0069] The third AND gate logic 330 is used to determine the Auxiliary Power Unit (APU) startup condition. Specifically, when three conditions are simultaneously met—the detection of an aircraft APU startup signal, the detection of the aircraft APU speed signal switching from a stopped state to an increasing state, and the detection that the current value I(t) and duration Δt of the lithium battery pack meet the second threshold condition (i.e., threshold 2)—the aircraft can be determined to be in the APU startup condition. In this case, the measurement value of the second current sensor is used for state of charge estimation. Under this condition, the lithium battery pack outputs a short-term high current in the hundreds of amperes. By jointly determining the startup signal and speed signal, the short-term high-current discharge scenario can be quickly captured, avoiding detection errors under high current.

[0070] The logic for determining all three operating conditions can be executed by the battery management system 130, and is reusable. Figure 1 The existing APU start signal, APU speed signal, and aircraft WOW signal acquisition links can be used without adding new detection hardware; they can be implemented simply through a software logic upgrade of the BMS.

[0071] Figure 4 A workflow diagram for estimating the state of charge (SOC) of an aircraft lithium-ion battery according to an embodiment of the present invention is shown. The workflow is... Figure 2 The detailed execution logic of the charge state estimation method shown can be obtained through... Figure 1 The battery management system 130 is implemented as described. For example... Figure 4 As shown, the complete execution process for state of charge estimation is as follows.

[0072] After the battery management system 130 is powered on and initialized, the three detection links can be executed in parallel: In step 402, it is detected whether the aircraft is in a power-down shutdown state. The aircraft's wheel-mounted signals, the power supply status of the important DC busbar (i.e., the DC emergency busbar) and the battery pack operating parameters are continuously monitored. The judgment node in step 404 is used to confirm whether the aircraft is in a shutdown state. If the judgment is yes, otherwise, return to step 402 to continuously cycle through the detection. If the judgment is yes, then step 406 is executed.

[0073] In step 406, the current value I(t) and duration Δt of the lithium battery pack are checked to see if they meet the preset first threshold condition (i.e., whether threshold 1 is met). The judgment node in step 408 confirms whether the parameters meet the leakage current condition requirements. If the judgment is yes, otherwise, the process returns to step 406 for continuous loop detection. If the judgment is yes, step 410 is executed to determine that the aircraft is in a continuous leakage current condition. Step 412 is then executed, and the measurement value of the first current sensor 110 (such as a resistor shunt) is used for ampere-hour integration to complete the state of charge estimation. The threshold 1 can be set, for example, to I(t) < 2A and Δt ≥ 30 seconds (example value, which can be adjusted according to the actual load size).

[0074] In the emergency power supply condition detection link that runs parallel to the leakage current condition detection link, step 422 continuously detects whether the aircraft has triggered an emergency power supply scenario, monitors the power supply status of the DC main bus bar, and confirms whether it is an emergency power supply status through the judgment node in step 424. If it is determined to be an emergency power supply status, otherwise, it returns to step 422 to continuously loop the detection. If it is determined to be an emergency power supply status, then step 426 is executed.

[0075] In step 426, the current value I(t) and duration Δt of the lithium battery pack are checked to see if they meet the preset third threshold condition (i.e., whether threshold 3 is met). The judgment node in step 428 confirms whether the parameters meet the requirements of the emergency power supply condition. If the judgment is yes, otherwise, the process returns to step 426 for continuous loop detection. If the judgment is yes, step 430 is executed, determining that the aircraft is in an emergency power supply condition. Step 432 is then executed, using the weighted fusion current values ​​from the first current sensor 110 and the second current sensor 120 to perform ampere-hour integration to complete the state of charge estimation. The weighting weight of the first current sensor can be higher than that of the second current sensor. Threshold 3 can be set, for example, to I(t) ≥ 30A and Δt ≥ 5 seconds (example values, which can be adjusted according to the actual load). The weighting coefficient... For example, it can be set to ≥0.9 (example value, which can be adjusted according to the actual detection current). The sum of the weights of the two types of sensors can be set to always be 1. Optionally, the threshold determination can be based on the detection results of a number of consecutive sampling points. For example, it can be set so that the detection values ​​of 5 consecutive sampling points all meet the threshold requirement to avoid misjudgment caused by interference.

[0076] In the APU start-up condition detection link, which runs parallel to the first two types of condition detection links, step 442 continuously detects the aircraft APU start-up signal and monitors the APU start-up command of the aircraft avionics system. The judgment node in step 444 confirms whether the APU start-up signal has been detected. If the judgment is yes, the system returns to step 442 to continuously detect the signal. If the judgment is yes, step 446 is executed to further detect the aircraft APU speed signal.

[0077] In step 446, the judgment node in step 448 confirms whether the APU speed signal has switched from a stopped state to an increasing state. If the judgment is yes, otherwise, return to step 446 to continue detection. If the judgment is yes, proceed to step 450 to check whether the current value I(t) and duration Δt of the lithium battery pack meet the preset second threshold condition (i.e., whether threshold 2 is met). The judgment node in step 452 confirms whether the parameters meet the APU start-up requirements. If the judgment is no, otherwise, return to step 450 to continue cyclic detection. If the judgment is yes, proceed to step 454 to determine that the aircraft is in the APU start-up condition. Proceed to step 456 to perform ampere-hour integration using only the measurement value of the second current sensor 120 (Hall effect sensor) to complete the state of charge estimation. Here, threshold 2 can be set, for example, to I(t) ≥ 100A (example value, which can be adjusted according to the actual load size).

[0078] The detection logic for the three operating conditions is executed independently and in parallel. After the operating condition judgment result is output, the system can also monitor the operating condition switching signal in real time. When a bidirectional switch is detected between the APU startup operating condition and other operating conditions, the weighting of the two types of current sensors is linearly adjusted within a preset switching window duration. The weighted fusion current value is used to smoothly transition and complete the state of charge estimation, avoiding estimation errors caused by current jumps. Then, the process ends and returns to the initial detection state, achieving continuous high-precision state of charge estimation under all operating conditions. The switching window duration for APU operating condition entry and exit can be set to, for example, 3 seconds (example value). When entering, the weighting of the first current sensor can be linearly decreased from the current value to 0, and when exiting, it can be linearly increased from 0 to the target value.

[0079] Figure 5 A hardware architecture diagram of a state-of-charge estimation system for an aircraft lithium-ion battery pack according to an embodiment of the present invention is shown. The system illustrates a typical hardware environment in which the invention can be applied according to exemplary embodiments thereof.

[0080] The system may include components that are connected to or communicate with the bus 520. For example, the system may include the bus 520, a processor 505, and one or more memories 510, etc.

[0081] Processor 505 can be any type of processor and may include, but is not limited to, general-purpose processors and / or special-purpose processors (e.g., special-purpose chips), intelligent hardware devices (e.g., general-purpose processors, DSPs, CPUs, microcontrollers, ASICs, FPGAs, programmable logic devices, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, processor 505 may be configured to use a memory controller to operate the memory array. In other cases, a memory controller (not shown) may be integrated into processor 505. Processor 505 may be responsible for managing bus 520 and general processing, including executing computer-executable instructions 515 stored on memory 510. Processor 505 may also be configured to perform various functions described herein related to the state-of-charge estimation method for aircraft lithium-ion battery packs. For example, processor 505 may be configured to: identify the operating conditions of the aircraft; and in response to the identified operating conditions being a continuous leakage current condition, an auxiliary power unit start-up condition, or an emergency power supply condition, to estimate the state of charge of the lithium battery pack using current values ​​collected by at least one of a first current sensor and a second current sensor, wherein the first current sensor has a first rated detection range and the second current sensor has a second rated detection range, the upper limit of the second rated detection range being greater than or equal to the upper limit of the first rated detection range.

[0082] Memory 510 is any storage device that meets airborne reliability requirements, including but not limited to non-volatile solid-state memory, ROM (read-only memory), RAM (random access memory), cache memory, programmable read-only memory, and / or other storage media conforming to airborne standards. Memory 510 may store computer-executable instructions 515, which, when executed, cause the processor to perform the various functions described herein. Memory 510 may have various data / instructions / codes for implementing the various functions described herein related to the design of a state-of-charge estimation system for aircraft lithium-ion battery packs. In one example, memory 510 may also store threshold parameters for three operating conditions (first, second, and third threshold conditions and corresponding duration thresholds), weighting rules for two types of current sensors, operating condition switching window duration, ampere-hour integral coefficient, and initial state-of-charge value, for use by processor 505.

[0083] Computer-executable instructions 515 may be stored in memory 510, including but not limited to an operating system, one or more application programs, drivers, and / or other data and code. Instructions for performing the various functions described herein may be included in one or more application programs, and components of the system may be implemented by processor 505 reading and executing the instructions of one or more application programs. In some cases, computer-executable instructions 515 may not be directly executable by the processor, but may (e.g., at compile and execution time) cause the computer to perform the various functions described herein related to the state-of-charge estimation method for aircraft lithium-ion battery packs.

[0084] It is understood that the above hardware architecture is merely an example. In practical applications, the configuration and connection relationship of hardware components can be adjusted according to the airborne safety level and performance requirements, as long as the state of charge estimation function for aircraft lithium battery packs described in this invention can be achieved.

[0085] This invention addresses the extreme operating conditions of lithium-ion batteries in civil aircraft, where the output current spans five orders of magnitude. Through a dual-current sensor architecture with differentiated range adaptation, it achieves high-precision current acquisition across all operating conditions, effectively reducing the cumulative error of ampere-hour integration and solving the industry-wide problem of difficulty in estimating the state of charge (SOC) of lithium iron phosphate batteries during their plateau phase. In engineering implementation, this solution fully reuses the existing avionics system's APU start-up signal, wheel load signal, speed signal, and busbar status signal acquisition links for civil aircraft lithium-ion batteries. No new hardware modules are required; implementation is achieved solely through a software upgrade of the battery management system. This adapts to the batch deployment needs of new aircraft models and supports rapid retrofitting of existing models. Furthermore, the dual-sensor architecture complies with the safety principles of independent and dissimilar designs for civil aircraft. Compared to a single-sensor solution, it significantly reduces the risk of sensor failure, avoids safety hazards such as fluctuating remaining charge levels, overcharging, and over-discharging caused by inaccurate SOC estimation, improves the reliability and safety of lithium-ion battery operation, extends the SOC calibration cycle of lithium iron phosphate batteries, and reduces maintenance and spare parts inventory costs. Furthermore, a linear weighted transition mechanism is adopted during operating condition switching, which can achieve seamless connection of sensor switching, avoid charge state jumps, improve the user experience of the unit, and fully meet the design requirements of high reliability and high safety of civil aircraft.

[0086] The foregoing description includes examples of various aspects of the claimed subject matter. It is certainly impossible to describe every conceivable combination of components or methods for the purpose of depicting the claimed subject matter, but those skilled in the art will recognize that many further combinations and arrangements of the claimed subject matter are possible. Thus, the disclosed subject matter is intended to cover all such changes, modifications, and variations that fall within the spirit and scope of the appended claims.

Claims

1. A method for estimating the state of charge (SOC) of an aircraft lithium battery pack, characterized in that, The state of charge estimation method includes: Identify the operating conditions of the aircraft; and In response to the identified operating conditions being continuous leakage current condition, auxiliary power unit start-up condition, or emergency power supply condition, the state of charge of the lithium battery pack is estimated using the current value collected by at least one of the first current sensor and the second current sensor. The first current sensor has a first rated detection range, and the second current sensor has a second rated detection range, wherein the upper limit of the second rated detection range is greater than or equal to the upper limit of the first rated detection range.

2. The state of charge estimation method as described in claim 1, characterized in that, Identifying the operating conditions of the aircraft includes: The system detects the aircraft's wheel-mounted signals, the power supply status of the DC emergency busbar, and the current value and duration of the lithium battery pack; and If the detected wheel-mounted signal is in ground condition, the DC emergency busbar loses power, and the current value and current duration of the lithium battery pack meet the first threshold condition, the identified operating condition is determined to be the continuous leakage current condition, wherein the first threshold condition includes a first current threshold and a first duration threshold.

3. The state of charge estimation method as described in claim 1, characterized in that, Identifying the operating conditions of the aircraft includes: The system detects the start signal of the aircraft's auxiliary power unit, the rotational speed signal of the auxiliary power unit, and the current value of the lithium battery pack; and When the starting signal of the auxiliary power unit is detected to be in an active state, the rotation speed signal of the auxiliary power unit switches from a stopped state to an increasing state, and the current value of the lithium battery pack meets the second threshold condition, the identified operating condition is determined to be the starting condition of the auxiliary power unit, wherein the second threshold condition includes a second current threshold.

4. The state of charge estimation method as described in claim 1, characterized in that, Identifying the operating conditions of the aircraft includes: The system detects the aircraft's wheel-mounted signals, the power supply status of the DC main busbar, and the current value and duration of the lithium battery pack; and If the detected wheel-mounted signal is in a non-ground state, the DC main busbar loses power supply, and the current value and current duration of the lithium battery pack meet the third threshold condition, the identified operating condition is determined to be the emergency power supply condition, wherein the third threshold condition includes a third current threshold and a third duration threshold.

5. The state of charge estimation method as described in claim 1, characterized in that, In response to the identified operating condition being the continuous leakage current condition, the state of charge is calculated by integrating the current value collected by the first current sensor in ampere-hours.

6. The state of charge estimation method as described in claim 1, characterized in that, In response to the identified operating condition being the start-up condition of the auxiliary power unit, the current value collected by the second current sensor is integrated in ampere-hours to calculate the state of charge.

7. The state of charge estimation method as described in claim 1, characterized in that, In response to the identified operating condition being the emergency power supply condition, a weighted calculation is performed using the current values ​​collected by the first current sensor and the second current sensor to obtain a fused current, and an ampere-hour integral is performed based on the fused current to calculate the state of charge, wherein the weighting weight of the first current sensor is higher than the weighting weight of the second current sensor.

8. The state of charge estimation method as described in claim 1, characterized in that, In response to the detection of a bidirectional switching of the operating condition between the auxiliary power unit start-up condition and other operating conditions, during the window duration of the bidirectional switching, a fused current is calculated by weighting the current values ​​collected by the first current sensor and the second current sensor, and the state of charge is calculated by ampere-hour integration based on the fused current, wherein the weighting weights of the first current sensor and the second current sensor are linearly adjusted with the window duration.

9. The state of charge estimation method as described in claim 8, characterized in that, When the auxiliary power unit starts, during the first switching window period, the weight of the first current sensor is linearly reduced from its current value to 0. and When the auxiliary power unit starting condition is switched out, during the second switching window period, the weighting of the first current sensor is linearly increased from 0 to the target value. Wherein, the sum of the weighting weights of the first current sensor and the second current sensor is 1.

10. A state-of-charge estimation system for aircraft lithium battery packs, characterized in that, The state of charge estimation system includes: A first current sensor has a first rated detection range; A second current sensor has a second rated detection range, wherein the upper limit of the second rated detection range is greater than or equal to the upper limit of the first rated detection range; and The battery management system is communicatively connected to the first current sensor and the second current sensor, respectively, and is configured to perform the state-of-charge estimation method as described in any one of claims 1 to 9.

11. The state of charge estimation system as described in claim 10, characterized in that, The first current sensor is a resistive shunt, and the second current sensor is a Hall effect sensor.

12. The state of charge estimation system as described in claim 11, characterized in that, The first current sensor is located outside the lithium battery pack, and the second current sensor is located inside the lithium battery pack.

13. A non-transient computer-readable medium storing computer-executable instructions that, when executed by a state of charge estimation system, perform the state of charge estimation method as described in any one of claims 1 to 9.

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