CN109241558B - Electromechanical system service life prediction method based on fault hybrid model - Google Patents
Electromechanical system service life prediction method based on fault hybrid model Download PDFInfo
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Abstract
The invention relates to a method for predicting the service life of an electromechanical system based on a fault hybrid model, belongs to the technical field of reliability engineering, and solves the problems of low efficiency and high cost of service life prediction of the electromechanical system in the prior art. The method comprises the following steps: dividing an electromechanical system into a plurality of functional modules according to functions; establishing a fault hybrid model of each functional module to obtain a corresponding functional module fault hybrid model transfer function; and simultaneously simulating the non-fault and fault mixed conditions of the electromechanical system to obtain a non-fault output signal of the electromechanical system, an output signal when the electromechanical system has mixed faults and a fault characteristic value, and predicting the service life of the electromechanical system according to the time when the fault characteristic value reaches a fault threshold value. The method can effectively improve the service life prediction efficiency of the electromechanical system and reduce the prediction cost; in addition, the method can predict the service life of the product in the product design stage, and provides a basis for the improvement design and weak link discovery of subsequent products.
Description
Technical Field
The invention relates to the technical field of reliability engineering, in particular to a method for predicting the service life of an electromechanical system based on a fault hybrid model.
Background
The electromechanical system is a system formed by organizing circuit modules and mechanical modules which are related, interacted and mutually influenced, faults are common in operation and have mixed characteristics in real life, the faults comprise structural faults and non-structural faults, wherein the structural faults refer to circuit topological structure changes caused by faults of electronic devices in the functional modules, and the non-structural faults refer to electrical performance signal changes caused by degradation or parameter drift of the electronic devices in the functional modules.
The electromechanical system is widely applied in actual life, and the weak link of the electromechanical system can be determined more quickly and accurately, the reliability level of the electromechanical system can be evaluated, and reasonable measures can be selected to implement reliability increase by predicting the service life of the electromechanical system.
At present, the reliability life prediction of an electromechanical system is mainly researched by collecting reliability test data to predict the life; however, the reliability test is expensive and historical failure data is difficult to collect.
Disclosure of Invention
In view of the above analysis, the present invention aims to provide a method for predicting a lifetime of an electromechanical system based on a fault mixture model, so as to solve the problems of low efficiency and high cost of predicting the lifetime of the electromechanical system in the prior art.
The purpose of the invention is mainly realized by the following technical scheme:
a method for predicting the service life of an electromechanical system based on a fault hybrid model comprises the following steps:
dividing an electromechanical system into a plurality of functional modules according to functions;
respectively establishing a fault hybrid model of each functional module to obtain a corresponding functional module fault hybrid model transfer function, and then establishing a fault hybrid model of the whole electromechanical system;
respectively simulating the fault mixed condition which changes along with time under the condition that the electromechanical system has no fault and the fault occurs randomly, acquiring the fault-free output signal of the electromechanical system, the output signal when the electromechanical system has the mixed fault and the fault characteristic value, and predicting the service life of the electromechanical system according to the time when the fault characteristic value reaches the fault threshold value.
The invention has the following beneficial effects: the method is carried out in the design stage of the electromechanical system, the prediction cost is low, meanwhile, the electromechanical system is described by establishing a fault hybrid model of the electromechanical system, the fault-free and fault-hybrid conditions of the electromechanical system are simulated respectively, and the predicted service life of the electromechanical system is obtained according to the simulation result. In addition, the service life prediction method provided by the invention can predict the service life of the product in the product design stage, and provides a basis for the improvement design and weak link discovery of the subsequent product.
Further, the fault characteristic value of the electromechanical system is:
wherein, Cu(t) is the output signal at time t when the electromechanical system is faultless, Cu' (t) is the output signal at time t when the electromechanical system has a miscellaneous fault.
The beneficial effect of adopting the further scheme is that: the method for obtaining the fault characteristic value of the electromechanical system by utilizing the fault-free and fault-mixed output signals of the electromechanical system is simple, effective and easy to implement, is beneficial to quantitatively judging the fault condition, understanding the deviation between the fault and the fault-free condition and providing a reference basis for subsequently judging the fault type.
Further, the service life of the electromechanical system is predicted through the time when the simulation fault characteristic value reaches the fault threshold value, and the method comprises the following steps:
and if the fault characteristic value exceeds the set fault threshold value, stopping the simulation, wherein the simulation time at the moment is the service life of the electromechanical system.
The beneficial effect of adopting the further scheme is that: when the fault characteristic value exceeds the set fault threshold value, the system signal output deviation degree is unacceptable, and the electromechanical system cannot complete the specified function, so that the time from the simulation beginning to the simulation end is considered as the service life of the electromechanical system.
Further, the fault hybrid model of the functional module is divided into a discrete layer, a continuous layer and an interactive layer:
the discrete layer is used for representing a corresponding circuit topological structure after the functional module has structural faults;
the continuous layer is used for representing the parameter change of the electronic device of the corresponding functional module after the non-structural fault occurs to the functional module;
the interaction layer is used for expressing a fault hybrid model result obtained by the functional module under the combined action of the discrete layer and the continuous layer.
The beneficial effect of adopting the further scheme is that: the fault hybrid model of the functional module is layered, the structural fault and the non-structural fault of the functional module are respectively analyzed, and finally, a fault hybrid model result obtained by the combined action of the discrete layer and the continuous layer is obtained on the interaction layer, so that the idea is clear and convenient to realize.
Further, the structural failure refers to a circuit topology change caused by a failure of an electronic device in the functional module;
the non-structural fault refers to the change of an electrical property signal caused by the degradation of an electronic device or parameter drift in the functional module.
The beneficial effect of adopting the further scheme is that: by determining the specific contents of the structural fault and the non-structural fault, related personnel can analyze the two faults conveniently, and more accurate analysis results can be obtained.
Further, establishing a fault hybrid model of each functional module, including:
defining structural faults of electronic devices in the functional modules as discrete events, and analyzing the structural faults of the electronic devices in the functional modules to obtain n discrete events;
determining a circuit topological structure of a fault hybrid model discrete layer in each discrete event, and establishing a circuit state equation under a corresponding structural fault;
analyzing the electronic devices involved in the structural fault circuit state equation, and obtaining parameter change functions of the electronic devices involved in the fault hybrid model continuous layer;
respectively inputting a structural fault circuit state equation established by the discrete layer and a parameter change function of an electronic device related to the corresponding continuous layer into an interaction layer of the fault hybrid model;
in the interaction layer, the parameter change function of the electronic device is used for replacing the corresponding parameter value of the electronic device in the structural fault circuit state equation to obtain a fault hybrid model result.
The beneficial effect of adopting the further scheme is that: the specific method for establishing the fault hybrid model is given, so that the establishing process of the fault hybrid model is clarified, and related technical personnel can conveniently establish the fault hybrid model according to the method provided by the application and obtain the result of the fault hybrid model.
Further, the input-output relationship among the u functional modules under the condition of mixed faults of the electromechanical system is as follows:
input signal of electromechanical system fault hybrid modelWherein i is more than or equal to 1, m is more than or equal to u, Cm' (t-1) represents an output signal of the mth functional module at the time t-1 in the event of a fault contamination;
eimshowing the connection relationship between the ith functional module and the mth functional module:
Cr' (t) represents the output signal of the r-th functional module at time t in the event of a fault contamination; n represents the number of discrete events in each functional module of the electromechanical system; lrjIndicates whether the jth discrete event in the tth functional circuit occurs,/rj0 means that the jth discrete event in the r-th functional module does not occur, lrj1 denotes the occurrence of the jth discrete event in the r-th functional circuit, GrjRepresenting a fault mixed model transfer function corresponding to the jth discrete event in the jth functional module; l1,l2,···,luRespectively showing whether the 1 st, 2 nd, u th functional modules work normally or not, G1,G2,···,GuRespectively representing the transfer functions of 1,2, ·, u functional modules in normal operation;
the beneficial effect of adopting the further scheme is that: through the input and output relation among all the functional modules, the overall quantitative expression result of the electromechanical system can be obtained, and the fault condition of the overall electromechanical system including structural faults and non-structural faults can be quantitatively analyzed.
Further, according to the connection relation of the electromechanical system function modules, the ith function module is determined to be the electromechanical system output module, and the fault hybrid transfer function output signal of the electromechanical system is an element C in a C' (t) matrixi′(t)。
The beneficial effect of adopting the further scheme is that: through the input and output relation among all the functional modules, the overall quantitative expression result of the electromechanical system can be obtained, and the fault condition of the overall electromechanical system including structural faults and non-structural faults can be quantitatively analyzed.
Further, in the input-output relationship among u functional modules in the electromechanical system, for the input-output relationship of each path, lr1,lr2,···,lrn,lrOne and only one value is 1 and the remaining values are 0.
The beneficial effect of adopting the further scheme is that: the working conditions of all modules in the electromechanical system are analyzed, and only normal or 1 discrete time form exists in the actual operation process of the electromechanical system, so thatr1,lr2,···,lruOne and only one value is 1 and the remaining values are 0.
Further, the calculation process of the fault-free response result of the electromechanical system comprises the following steps:
analyzing the circuit topological structure of each functional module in normal work, and establishing a corresponding circuit state equation;
obtaining a normal transfer function of a corresponding functional module through Laplace transformation, and obtaining an input-output relation among u functional modules in the electromechanical system:
G1,G2,···,Gurespectively representing the transfer function of the 1,2,. cndot., u functional modules in normal operation, the input signal of the ith functional moduleWherein 1 is≤i、m≤u，Cm(t-1) represents the output signal of the mth functional module at the time of t-1 in normal operation;
eimshowing the connection relationship between the ith functional module and the mth functional module:
Ci(t) represents the output signal of the ith functional module at the time of t in normal operation; determining the ith functional module as an electromechanical system output module according to the connection relation of the electromechanical system functional modules, wherein the failure-free response result of the electromechanical system is an element C in a matrix C (t)i(t)。
The beneficial effect of adopting the further scheme is that: by analyzing the circuit topological structure of each functional module of the electromechanical system when the functional module works normally, the transfer function of each module response is obtained, and accordingly, the fault-free transfer function of the electromechanical system is obtained.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a flow chart of a method for predicting the life of an electromechanical system based on a fault confounding model;
FIG. 2 is a functional module division diagram of an electric steering engine system;
FIG. 3 is a topology diagram of a discrete layer circuit when the circuit in the functional module of the DC servo motor is normal;
FIG. 4 is a topological structure diagram of a discrete layer circuit when a resistor in a functional module of a DC servo motor is short-circuited;
FIG. 5 is a control diagram of an electric steering engine system;
FIG. 6 is a flow chart of a simulation run of an electromechanical system;
FIG. 7 is a graph of output results of a fault-free operation of an electromechanical system;
FIG. 8 is a graph of output results when the electromechanical system fails;
fig. 9 shows the actual life prediction simulation result of the electromechanical system.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
One embodiment of the present invention discloses a method for predicting the life of an electromechanical system based on a fault hybrid model, as shown in fig. 1, the method includes the following steps:
step S1: the electromechanical system is divided into a plurality of functional modules according to functions: determining the structural composition of the electromechanical system, analyzing the logical relationship of each composition unit in the electromechanical system, and dividing the functional modules according to the functions of the composition units.
For an electric steering engine system, it is a component of the control system on the missile. And controlling the control surface of the missile or changing the thrust vector of an engine according to a signal input by the missile-borne control system, and controlling the flight of the missile. According to the functions of all the components, the device is divided into five functional modules, namely a steering engine controller, a driver, a direct current servo motor, a speed reduction transmission mechanism and an angle sensor, as shown in figure 2.
Step S2: establishing a fault hybrid model of each functional module: and analyzing the fault mode of each functional module, and establishing a fault mixed model containing structural faults and non-structural faults. Wherein a structural failure refers to a change in circuit topology caused by a failure of an electronic device in a functional module; non-structural faults refer to electrical performance signal changes caused by degradation of electronic devices or parameter drift in functional modules. By determining the specific contents of the structural fault and the non-structural fault, related personnel can analyze the two faults conveniently, and more accurate analysis results can be obtained.
The fault hybrid model of the functional module is divided into a discrete layer, a continuous layer and an interactive layer;
the discrete layer is used for representing a corresponding circuit topological structure after the functional module has structural faults; the continuous layer is used for representing the parameter change of the electronic device of the corresponding functional module after the non-structural fault occurs to the functional module; the interaction layer is used for expressing a fault hybrid model result obtained by the functional module under the combined action of the discrete layer and the continuous layer. The fault hybrid model of the functional module is layered, the structural fault and the non-structural fault of the functional module are respectively analyzed, and finally, a fault hybrid model result obtained by the combined action of the discrete layer and the continuous layer is obtained on the interaction layer, so that the idea is clear and convenient to realize.
Establishing a fault hybrid model of each functional module, which specifically comprises the following steps:
step S21: analyzing the component devices of each functional module, and determining the devices which are likely to generate structural faults and the corresponding circuit topological structures thereof; defining structural faults of electronic devices in the functional module as discrete events to obtain n fault discrete events:
for the electric steering engine system of this embodiment, the number of discrete fault events is set to 6, and six structural fault conditions include an inductance short circuit, an inductance open circuit, a resistance short circuit, a resistance open circuit, a short circuit between the inductance and the resistance, and a simultaneous open circuit between the inductance and the resistance.
Step S22: determining a circuit topological structure of a fault hybrid model discrete layer in each discrete event, and establishing a circuit state equation under a corresponding structural fault;
for example, in a direct current servo motor functional module in an electric steering engine system, when a resistor is short-circuited, a circuit topology structure diagram of a discrete layer is changed from fig. 3 to fig. 4.
The state equation is established for the resistance short circuit in the servo motor as follows:
TM＝KTi (1-3)
in the above formula: u represents an armature voltage; l represents the armature total inductance (H); i represents the armature current (a); r represents the armature total resistance (Ω): e represents a counter potential (V); t isMRepresenting motor torque (Nm); t isLRepresenting the load torque (Nm) translated onto the motor shaft; t isBRepresents an acceleration torque (Nm); j denotes the total through rotation (kgm) on the motor shaft2)；KERepresents the back electromotive force coefficient (Vs/rad); kTRepresents the torque coefficient (Nm/rad); t isfRepresenting the friction torque (Nm); θ represents a motor rotational angle (°).
Step S23: analyzing devices which are possibly subjected to non-structural faults in each functional module, namely electronic devices involved in a structural fault circuit state equation, determining parameter change functions of the electronic devices, and completing construction of continuous layers in a fault hybrid model. If L in the circuit is degraded, then L is equal to L0(1+ kt), L represents the inductance value of the inductor at time t, L0The inductance value when the inductance is normal is shown. k represents the degradation rate of the inductance.
Step S24: after the state equation under each fault discrete event is established and the device with non-structural fault and the parameter change function thereof are determined, namely the discrete layer and the continuous layer are established, finally the interactive layer of the fault hybrid model is established, and the electronic device parameter change function is used for replacing the corresponding electronic device parameter in the state equation of the structural fault circuit to obtain the fault hybrid model result. The fault confounding model result is a space containing all state equations containing parametric variation functions.
If the resistance in the servo motor circuit is short-circuited, the state equation of the circuit under the condition that the inductance is degraded and has a fault is as follows:
wherein L is0Represents the nominal value of the inductance, k represents the degradation rate of the inductance, and t represents the degradation time.
The specific method for establishing the fault hybrid model is given, so that the establishing process of the fault hybrid model is clarified, and related technical personnel can conveniently establish the fault hybrid model according to the method provided by the application and obtain the result of the fault hybrid model.
Step S3: and analyzing the circuit topological structure of each functional module in normal work, establishing a corresponding circuit state equation, and obtaining the normal transfer function of the corresponding functional module through Laplace transformation.
According to the fault hybrid model of each functional module, performing Laplace transform on the fault hybrid model result of each functional module, namely each state equation containing a parameter change function to obtain a corresponding functional module fault hybrid model transfer function, wherein the mathematical description is as follows:
wherein
1)qjRepresenting the jth discrete event q.
2)lj: indicating whether the circuit has occurred at time t with the jth discrete event.
3)Cj: representing an output matrix at the jth discrete event;
4) s: represents an expression of the primitive function after laplace transformation, not a parameter.
5) E: representing an identity matrix;
6)representing the state matrix at time t at the jth discrete event. Because the components in the circuit generate parameter drift along with time, the circuit has the advantages of high reliability, low cost and the likeIs a function related to time and circuit composition parameters.
7)Is the control matrix for the jth discrete event.
8) n indicates that a total of n structural faults occur in the circuit, and n topologies correspond to the structural faults.
Taking a servo motor in an electric steering engine system as an example, the normal transfer function of the circuit is a constant value, and is represented as follows:
no structural failure occurs, only non-structural failure occurs, and the transfer function is
When the inductor is short-circuited, the transfer function of the functional module is as follows:
when the resistance is short-circuited, the transfer function of the functional module is
When both inductive short-circuiting and resistive degradation in the circuit are involved, the transfer function of the functional block is
Similarly, when the circuit simultaneously comprises inductance degradation and resistance short circuit, the transfer function of the functional module is as follows:
the functional module fault hash model transfer function is represented as follows:
wherein: j67.2 gcm2，KT＝2.8×105N·m/rad，KE＝7.68×10-4v/deg/s，R0＝10Ω，L＝6.7H，krRepresenting the degradation rate of resistance, klRepresenting the degradation rate of the inductance;
l1(t) indicating whether an inductive short circuit discrete event occurs at time t; if it occurs, then1(t) is 1, if l does not occur1(t)＝0；
l2(t) indicating whether a resistance short circuit discrete event occurs at time t; if it occurs, then2(t) is 1, if l does not occur2(t)＝0；
l3(t) indicates whether or not a structural failure has occurred in the system at or before time t, and if no structural failure has occurred, then l3(t) ═ 1; if a structural failure occurs,/, then3(t)＝0。
The specific method for establishing the fault hybrid model is given, so that the establishing process of the fault hybrid model is clarified, and related technical personnel can conveniently establish the fault hybrid model according to the method provided by the application and obtain the result of the fault hybrid model.
For an electric steering engine system, the information is summarized as follows:
the transfer function of the electric steering engine system at the moment t can be calculated according to the functional logic relationship of the functional modules formed by the electric steering engine system at the moment t. An electric steering engine system control diagram is shown in figure 5.
When the electromechanical system has no fault, the transfer functions of all the constituent functional modules are as follows:
then the transfer function of the system
Step S4: and obtaining an output signal under the fault condition according to the input signal of the electromechanical system and the fault hybrid model, calculating a fault characteristic value, and realizing the service life prediction of the electromechanical system based on the fault hybrid model through the time when the fault characteristic value reaches a fault threshold value.
Step S41: and determining the devices which are possible to have structural faults and the fault rate thereof, and calculating the probability of each discrete event. The resulting failure rate for each discrete event is the input data for the time-and event-driven failure-confounding model simulation run. If the failure rates of the resistor and the inductor are respectively set to 0.01 for the electric steering engine system, the failure rate statistics of the possible structural failures for this embodiment are shown in the following table:
| serial number | Structural failure | Failure rate |
| 1 | Resistance breaking | 0.01 |
| 2 | Inductance open circuit | 0.01 |
| 3 | Short circuit of resistance | 0.01 |
| 4 | Short circuit of inductor | 0.01 |
| 5 | Short circuit at the same time | 0.00001 |
| 6 | Simultaneous disconnection | 0.00001 |
Step S42: and randomly extracting the time when the structural fault occurs on the simulation time axis according to the fault rate. The fault-blending model simulation referred to in this application is time and event driven based. The time is the time of system operation, and since the device parameter variation function represented by the non-structural fault is the variation of the description parameter with time, the transfer function of the functional module at each moment also continuously generates parameter variation with time. The event is a discrete event occurring in the system operation, and is used for expressing a structural fault, and when the discrete event occurs, the structural change of the transfer function at the current moment is caused.
Step S43: and determining fault threshold eta of each functional module in the composition system, and stopping the simulation when the fault degree value Z (t) exceeds a set threshold.
The fault threshold for the electromechanical system is given by the circuit designer to indicate the highest degree of fault deviation that is acceptable. When the fault characteristic value is lower than a fault threshold eta, the simulation is continued; when the fault characteristic value is higher than the fault threshold value, the simulation is stopped;
the fault characteristic value Z (t) is used for expressing the fault deviation degree of the corresponding functional module at the time t,
wherein, Cu(t) is the output signal at time t when the electromechanical system is faultless, Cu' (t) is the output signal at time t when the electromechanical system fails.
For the electric steering engine system in this embodiment, the statistics of the fault threshold values of the functional modules are as follows:
step S44: simulating an operation fault hybrid model;
the simulation in the invention is based on discrete events and time drive, the occurrence time of the discrete events is extracted according to the fault rate of each discrete event, and each discrete event is arranged on a time axis. The signal is input to a transfer function with no faults and mixed faults. The output signal at time t of each functional module is related to the fault-free transfer function, its own hybrid model result (transfer function at time t) and the input signal to the module at time t-1.
The input and output relations among the u functional modules in the electromechanical system are as follows:
input signal of electromechanical system fault hybrid modelWherein i is more than or equal to 1, m is more than or equal to u, Cm' (t-1) denotes the m-th one in the event of a fault contaminationThe functional module outputs signals at the time t-1;
eimshowing the connection relationship between the ith functional module and the mth functional module:
Cr' (t) represents the output signal of the r-th functional module at time t in the event of a fault contamination; n represents the number of discrete events in each functional module of the electromechanical system; lrjIndicates whether the jth discrete event in the tth functional circuit occurs,/rj0 means that the jth discrete event in the r-th functional module does not occur, lrj1 denotes the occurrence of the jth discrete event in the r-th functional circuit, GrjAnd representing the transfer function of the fault hybrid model corresponding to the jth discrete event in the ith functional module. l1,l2,···,luRespectively showing whether the 1 st, 2 nd, u th functional modules work normally or not, G1,G2,···,GuRespectively representing the transfer functions of 1,2,. cndot.u functional modules in normal operation.
Through the input and output relation among all the functional modules, the overall quantitative expression result of the electromechanical system can be obtained, and the fault condition of the overall electromechanical system including structural faults and non-structural faults can be quantitatively analyzed.
In the input-output relationship among u functional modules in the electromechanical system, for the input-output relationship of each path, lr1,lr2,···,lrn,lrOne and only one value is 1 and the remaining values are 0.
The working conditions of all modules in the electromechanical system are analyzed, and only normal or 1 discrete time form exists in the actual operation process of the electromechanical system, so thatr1,lr2,···,lruOne and only one value is 1 and the remaining values are 0.
The input-output relationship among the u functional modules of the electromechanical system is expressed by a matrix as follows:
a fault output matrix of the electromechanical system at the moment t:
C′(t)＝[C1′(t),C2′(t)，···,Cu′(t)]T (5)
a fault input matrix at the moment t of the electromechanical system:
R′(t)＝[R1′(t),R2′(t)，···,Ru′(t)]T (6)
discrete event occurrence matrix:
fault transfer function of electromechanical system
The input and output matrix relationship among the u functional modules of the electromechanical system is as follows:
C′(t)＝L(t)G(t)TR′(t) (9)
by establishing the input and output matrix among the u functional modules of the electromechanical system, related technicians can directly fill related functions and coefficients into corresponding matrices, and the output matrix C' (t) of the u functional modules can be obtained through calculation, so that the powerful calculation capacity of the matrices is fully utilized, the calculation time is saved, and meanwhile, a more accurate fault mixing analysis result is obtained.
The simulation operation flow chart is shown in FIG. 6; the transfer function under the fault-free condition is constant to G (K); a fault-free output signal c (t) ═ g (k) r (t);
wherein R (t): an input signal representing the time;
k: representing the parameters of the circuit component devices in the absence of faults.
Judging whether a discrete event occurs at the current moment, if not, only generating non-structural faults, changing a system matrix A in a transfer function according to the parameter change rule of the component to change the transfer function from G (K) to G (K + kt). Wherein K represents the parameter change rate of a circuit device, and G (K + kt) represents the transfer function of the circuit after the non-structural fault occurs at the time t; the signal output deviation at that time
C′(t)＝G(K+kΔt)R(t) (10)
C' (t): an output deviation signal indicative of the time;
r (t) represents an input signal at the time;
Δ t: represents a unit time;
if the discrete event occurs, judging whether the discrete event is a new discrete event;
if yes, the transfer function at the moment is structurally changed, and structural fault jump occurs:
wherein:
g (t): representing the transfer function of the electromechanical system at the present moment;
qj(t): representing a discrete event occurring at that time;
the deviation signal outputted at this moment is
C' (t): an output deviation signal indicative of the time;
if the discrete event is not a new discrete event, no structural fault jump occurs, and an unstructured fault still occurs on the transfer function under the discrete event at the previous moment, wherein the transfer function is as follows:
the output offset signal is:
determining an output deviation signal and a fault-free output signal at the moment t, and calculating a fault characteristic value at each moment; when the fault characteristic value does not exceed the threshold value, the simulation is continued; when it reaches the threshold, the simulation stops.
Due to the transition of the transfer function, a deviation of the output signal is caused. And calculating the fault characteristic value of the circuit through the output signal value of the transfer function after the non-structural fault occurs and the value of the normal output signal, finishing the simulation when the fault characteristic value exceeds a fault threshold eta of the circuit, and indicating that the simulation is continued if the fault characteristic value does not exceed the threshold.
Step S45: according to the simulation result, the service life of the electromechanical system is predicted; the method simulates the operation condition of the electromechanical system by simulating the operation fault hybrid model, and when the fault characteristic value exceeds a threshold value, the system signal output deviation degree is unacceptable, and the electromechanical system cannot complete the specified function, so that the time from the start of simulation to the end of simulation can be considered as the service life of the electromechanical system;
specifically, the life of the electromechanical system is predicted by simulating the time when the fault characteristic value reaches the fault threshold value, and the steps are as follows:
and sampling according to the fault rate of each structural fault mode of each component unit of the electromechanical system to obtain the occurrence time of each structural fault of each unit, and arranging according to the time sequence.
And (4) simulating the input signal of the fault-free system model to obtain the output signal of the system at each moment under the fault-free condition.
According to the fault occurrence sequence, sequentially injecting structural faults into the electromechanical system at corresponding moments, and establishing a discrete layer fault hybrid model; simultaneously, calculating a fault hybrid model of a continuous layer of the electromechanical system at each moment; and further combining the two models to establish an interaction layer hybrid model, and simulating an output signal of the electromechanical system under the condition that hybrid faults exist.
At the moment when each structural fault occurs, calculating the fault characteristic value of each moment of the system by comparing output signals under the conditions of no fault and mixed fault;
and if the fault characteristic value exceeds the set fault threshold value, stopping the simulation, wherein the simulation time at the moment is the service life of the electromechanical system.
For an electric steering engine system, the output response when the system is operating without faults is shown in fig. 7, wherein the vertical axis represents the output response of the system, and the horizontal axis represents different times of system simulation. It can be seen that the system output response gradually stabilizes with increasing simulation time.
Fig. 7 shows the system output response of the system without fault after injecting the miscellaneous fault. Its non-structural failure, i.e., parameter degradation, occurs all the time from the start of the simulation, and thus its output response has changed compared to the normal system output. When the time is about 50 hours, structural faults occur in the system, the output response of the system is changed greatly, the slope is changed, meanwhile, the system is accompanied by non-structural faults all the time, and the process accurately reflects the operation process of the steering engine system.
A failure characteristic value calculation result graph in the operation process of the electric steering engine system is shown in fig. 9, wherein the unit time is hour (h). The horizontal axis represents simulation time, the vertical axis represents fault characteristic values, and as seen from the figure, structural faults occur twice in total during the operation of the electromechanical system, after the structural faults occur, the fault characteristic values suddenly change, the slope of the curve of the fault characteristic values along with the change of the time is increased, meanwhile, the non-structural faults are always accompanied, and in the case that the threshold value is 0.45, the simulation is stopped when the time is about 800h, namely, the service life of the electromechanical system is 800 h.
Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.
Claims (9)
1. A method for predicting the service life of an electromechanical system based on a fault hybrid model is characterized by comprising the following steps:
dividing an electromechanical system into a plurality of functional modules according to functions;
respectively establishing a fault hybrid model of each functional module to obtain a corresponding functional module fault hybrid model transfer function, and then establishing a fault hybrid model of the whole electromechanical system;
the establishing of the fault hybrid model of each functional module comprises the following steps:
defining structural faults of electronic devices in the functional modules as discrete events, and analyzing the structural faults of the electronic devices in the functional modules to obtain n discrete events;
determining a circuit topological structure of a fault hybrid model discrete layer in each discrete event, and establishing a circuit state equation under a corresponding structural fault;
analyzing the electronic devices involved in the structural fault circuit state equation, and obtaining parameter change functions of the electronic devices involved in the fault hybrid model continuous layer;
respectively inputting a structural fault circuit state equation established by the discrete layer and a parameter change function of an electronic device related to the corresponding continuous layer into an interaction layer of the fault hybrid model;
in the interaction layer, replacing corresponding electronic device parameter values in a structural fault circuit state equation by electronic device parameter change functions to obtain a fault hybrid model result;
respectively simulating the fault mixed condition which changes along with time under the condition that the electromechanical system has no fault and the fault occurs randomly, acquiring the fault-free output signal of the electromechanical system, the output signal when the electromechanical system has the mixed fault and the fault characteristic value, and predicting the service life of the electromechanical system according to the time when the fault characteristic value reaches the fault threshold value.
2. The method of claim 1, wherein the fault signature values of the electromechanical system are:
wherein, Cu(t) is the output signal at time t when the electromechanical system is faultless, Cu' (t) is the output signal at time t when the electromechanical system has a miscellaneous fault.
3. The method for predicting the life of the electromechanical system based on the fault hybrid model according to claim 2, wherein the life of the electromechanical system is predicted by the time when the fault characteristic value reaches the fault threshold value, and the method comprises the following steps:
and if the fault characteristic value exceeds the set fault threshold value, stopping the simulation, wherein the simulation time at the moment is the service life of the electromechanical system.
4. The method of claim 1, wherein the fault-blending model of the functional module is divided into a discrete layer, a continuous layer, and an interactive layer:
the discrete layer is used for representing a corresponding circuit topological structure after the functional module has structural faults;
the continuous layer is used for representing the parameter change of the electronic device of the corresponding functional module after the non-structural fault occurs to the functional module;
the interaction layer is used for expressing a fault hybrid model result obtained by the functional module under the combined action of the discrete layer and the continuous layer.
5. The method of claim 4, wherein the fault hybridization model based electromechanical system life prediction method,
the structural fault refers to a circuit topology structure change caused by electronic device faults in the functional module;
the non-structural fault refers to the change of an electrical property signal caused by the degradation of an electronic device or parameter drift in the functional module.
6. The method for predicting the service life of the electromechanical system based on the fault hybrid model according to any one of claims 4 to 5, wherein the input-output relationship among the u functional modules under the condition of the fault hybrid of the electromechanical system is as follows:
input signal of electromechanical system fault hybrid modelWherein i is more than or equal to 1, m is more than or equal to u, Cm' (t-1) represents an output signal of the mth functional module at the time t-1 in the event of a fault contamination;
eimshowing the connection relationship between the ith functional module and the mth functional module:
Cr' (t) represents the output signal of the r-th functional module at time t in the event of a fault contamination; n represents the number of discrete events in each functional module of the electromechanical system; lrjIndicates whether the jth discrete event in the tth functional circuit occurs,/rj0 means that the jth discrete event in the r-th functional module does not occur, lrj1 denotes the occurrence of the jth discrete event in the r-th functional circuit, GrjRepresenting a fault mixed model transfer function corresponding to the jth discrete event in the jth functional module; l1,l2,···,luRespectively showing whether the 1 st, 2 nd, u th functional modules work normally or not, G1,G2,···,GuRespectively representing the transfer functions of 1,2,. cndot.u functional modules in normal operation.
7. The method of claim 6, wherein the connection of functional modules of the electromechanical system is based on a fault hybridization modelAnd (3) determining that the ith functional module is an electromechanical system output module, and the fault hybrid transfer function output signal of the electromechanical system is an element C in a C' (t) matrixi′(t)。
8. The method according to claim 6, wherein, in the I/O relationships between u functional modules in the electromechanical system, for each path, i is the I/O relationshipr1,lr2,···,lrn,lrOne and only one value is 1 and the remaining values are 0.
9. The method for predicting the service life of the electromechanical system based on the fault hybrid model according to claim 6, wherein the calculation process of the no-fault response result of the electromechanical system comprises the following steps:
analyzing the circuit topological structure of each functional module in normal work, and establishing a corresponding circuit state equation;
obtaining a normal transfer function of a corresponding functional module through Laplace transformation, and obtaining an input-output relation among u functional modules in the electromechanical system:
G1,G2,···,Gurespectively representing the transfer function of the 1,2,. cndot., u functional modules in normal operation, the input signal of the ith functional moduleWherein i is more than or equal to 1, m is more than or equal to u, Cm(t-1) represents the output signal of the mth functional module at the time of t-1 in normal operation;
eimshowing the connection relationship between the ith functional module and the mth functional module:
Ci(t) represents the output signal of the ith functional module at the time of t in normal operation; determining the ith functional module as an electromechanical system output module according to the connection relation of the electromechanical system functional modules, wherein the failure-free response result of the electromechanical system is an element C in a matrix C (t)i(t)。
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