Adaptive fault-tolerant control method and storage medium for forklift actuator failure

Abstract

The present invention discloses an adaptive fault-tolerant control method and storage medium for a forklift actuator failure, comprising setting a failure factor module, an actuator failure module, a fuzzy system model, and an adaptive fault-tolerant controller module; the hydraulic support cylinder acts as an actuator in the forklift anti-rollover system to provide support force for the forklift body; the failure factor is an unhealthy factor, and the size range of the failure factor is judged to distinguish different fault types of the actuator of the counterbalanced forklift anti-rollover system; there are many types of actuator failures, and various failures are combined to perform a unique fault model representation; a fuzzy model of the forklift anti-rollover system is established based on the forklift body state parameters and fault control input; the adaptive fault-tolerant controller updates the controller parameters by using the adaptive law to ensure the stability of the closed-loop forklift anti-rollover system.

Description

Technical Field

[0001] The invention relates to the technical field of vehicle active safety, and in particular to an adaptive fault-tolerant control method for a forklift actuator failure. Background Art

[0002] In the field of active safety technology of forklifts, although the anti-rollover system is becoming more and more perfect, the fault-tolerant control technology for the actuator failure of the anti-rollover system of counterbalanced forklifts has not yet been applied. If the actuator fails in the forklift anti-rollover system, if the actuator fails, the instructions issued by the electronic control unit cannot get feedback from the actuator, the actuator cannot carry out the corresponding instructions, and the safety and stability of the forklift cannot be guaranteed. Therefore, the fault-tolerant control of the forklift anti-rollover system is essential. Summary of the invention

[0003] The present invention provides an adaptive fault-tolerant control method for a forklift actuator failure, which can solve the above technical problems.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] An adaptive fault-tolerant control method for a forklift actuator failure comprises the following steps:

[0006] Setting the failure factor υ ij Used to cooperate with the uncertain control part caused by the forklift anti-rollover system actuator to determine the system actuator fault type;

[0007] Set the actuator fault model u F (t) For all M A forklift actuator fault model describes the only forklift anti-rollover system actuator fault model, providing practical control input for the forklift model with actuator faults;

[0008] The fuzzy system model is set up to consider the vehicle body slip angular velocity, yaw angular velocity, frame roll angle, actuator fault control input, disturbance input and control output;

[0009] An adaptive fault-tolerant controller is set up to update the parameters of the adaptive law controller and apply the Lyaounov stability theory to give sufficient conditions for the stability of the forklift anti-rollover system when there are actuator failures and external interference.

[0010] Furthermore, through formula (1-1), the failure factor υ ij The range of the uncertain control part E(t) caused by the actuator failure is combined to distinguish the type of actuator failure:

[0011]

[0012] Furthermore, through formula (1-2), all the M forklift actuator fault models are expressed as the following unique fault model:

[0013] u F (t) = (1-υ i )u(t)+ζ i u s (t)+E(t)(1-2)

[0014] In formula (1-2), 1-υ i (t) = diag[υ i1 (t),…,υ im (t)]∈{υ i1 ,…,υ iΦ}; E(t) is the uncertain control part caused by the actuator of the forklift anti-rollover system; where u s (t) represents the non-decomposable actuator fault model in the counterbalanced forklift rollover fuzzy system.

[0015] Furthermore, the forklift anti-rollover fuzzy system model is constructed using formula (1-3):

[0016]

[0017] In formula (1-3), x c (t) represents the body state of the forklift, including the sideslip angular velocity, yaw angular velocity and frame roll angle; u(t) is the actual control input of the counterbalanced forklift rollover fuzzy system; w(t) is the external disturbance of the system.

[0018] Furthermore, the adaptive controller (1-4) ensures the update of the strategy by updating the adaptive law controller parameters (1-5):

[0019]

[0020]

[0021] In formula (1-4), where Φ k is any positive constant, is limited, b k (k=1,2,…,N) is the matrix B i The kth column of

[0022] On the other hand, the present invention further discloses a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the above method.

[0023] It can be seen from the above technical solution that the adaptive fault-tolerant control method for forklift actuator failure of the present invention is expected to improve the fault tolerance capability of the anti-rollover system of the counterbalanced forklift, thereby improving the stability of the anti-rollover system of the forklift and improving the active safety of the forklift.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. A unique fault model that summarizes various faults and their combinations is established, which effectively includes the diversity of fault types of forklift anti-rollover system actuators;

[0026] 2. When the actuator fails and the upper limit of the interference is unknown, the controller parameters are updated at an adaptive rate to approximate the controller model and ensure the stability of the forklift anti-rollover system;

[0027] 3. The proposed adaptive fault-tolerant control method combines the adaptive technology with the fault-tolerant control technology controller model, which improves the fault-tolerant capability of the forklift anti-rollover system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the structure diagram of fault-tolerant control system;

[0029] Figure 2 This is the state response diagram of a normal controller without fault;

[0030] Figure 3 This is the state response diagram of the normal controller when it is faulty;

[0031] Figure 4 It is the state response diagram of the fault-tolerant controller under fault;

[0032] Figure 5 The fault level is the body roll angle;

[0033] Figure 6 The fault level is the body roll angle;

[0034] Figure 7 The body roll angle is fault level 2;

[0035] Figure 8 It is the yaw rate of the vehicle at fault level 2. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0037] like Figure 1As shown, the adaptive fault-tolerant control method for forklift actuator failure described in this embodiment includes setting a hydraulic support cylinder, a failure factor υ ij , actuator fault model u F (t), fuzzy system model, adaptive fault-tolerant controller;

[0038] As the actuator of the anti-rollover system of the counterbalanced forklift, the hydraulic support cylinder provides lateral support force to ensure that the forklift does not enter the danger zone when it tilts, while restoring the lateral stability of the vehicle body.

[0039] Failure factor ij Also known as the unhealthy factor, it is used to determine the fault type of the actuator; specifically, when considering the actuator fault of the forklift anti-rollover system (mainly including power failure, impact, jamming, deviation, or a combination of these faults), the actual control input u(t) of the counterbalanced forklift rollover fuzzy system has changed. Formula (2-1) is the actual fault input model of the system. The signal representing the failure of the i-th actuator in the j-th fault model.

[0040] where u is (t) represents the non-decomposable actuator fault model in the counterbalanced forklift rollover fuzzy system, u i (t) represents the desired control input signal. ij is a scalar function, υ ij represents the failure factor or unhealthy factor of the unknown time-varying actuator, and satisfies 0<υ a ≤υ i ≤υ b ≤1, E(t) is the uncertain control part caused by the actuator of the forklift anti-rollover system, The definition of is as follows:

[0041]

[0042]

[0043] In formula (2-1) (2-2)

[0044]

[0045] Then the operator set with the above structure is expressed as:

[0046]

[0047] At the same time we define the following collection:

[0048]

[0049] Actuator fault model u F(t) As the only fault model, it clearly describes all possible system failures M The actuator fault model of the forklift anti-rollover system can be expressed as:

[0050] u F (t) = (1-υ i )u(t)+ζ i u s (t)+E(t)(1-2)

[0051] In formula (1-2), 1-υ i (t) = diag[υ i1 (t),…,υ im (t)]∈{υ i1 ,…,υ iΦ}.

[0052] In the specific implementation, the fuzzy system model with actuator failure is constructed as follows:

[0053] Step 31, when the forklift tire tilts, the tire itself also deforms. Similarly, when the forklift turns at high speed, the deformation of the forklift tire will also increase, resulting in a larger tire side slip angle. Since the force characteristic curve of the forklift tire is not always approximately linear, the present invention adopts a typical nonlinear tire model in vehicle research, which is more common in vehicle stability research, namely the magic formula model, so the lateral force F of the front and rear tires is yf , F yr It can be expressed as:

[0054]

[0055]

[0056] In the formula, α f and α r are the side slip angles of the front and rear tires of the forklift respectively. In addition, for the parameter D in the above formula i , L i , G i and V i (i=f,r), their values ​​are affected by many factors, among which the key ones include travel speed, wheel adhesion, and wheel force characteristics.

[0057] Step 32: Based on the TS fuzzy model, the nonlinear characteristics of the front lateral force are estimated using the sliding area M1; the nonlinear characteristics of the rear lateral force are estimated using the sliding area M2; if |α f | belongs to M1, then:

[0058]

[0059] If |α f | belongs to M2, then:

[0060]

[0061] In formula (2-5) and (2-6), C fi (i=1,2) and C ri (i=1,2) are the cornering stiffness of the front and rear tires respectively, and their values ​​are affected by many factors, including tire width, load mass, wheel adhesion and vehicle speed.

[0062] Step 33: The lateral forces of the front and rear tires of the forklift are expressed as follows:

[0063]

[0064] In formula (2-7), λ i (|α f |)(i=1,2) is about the variable |α f |, these weighting functions satisfy the following properties: 0≤λ i (|α f |)≤1 and

[0065] Step 34: Assuming that the side slip angles of the front and rear tires of the forklift are small, we can get α f =β-(aω / v x ) and α r =δ-β-(bω / v x ). Considering the forklift dynamics model, the overall forklift anti-rollover TS fuzzy model is as follows:

[0066]

[0067] In formula (2-8) u(t)=F(t), and z(t)=[LTR] are the state, control input, disturbance input and control output of the above system model respectively. The correlation matrix is ​​as follows:

[0068]

[0069]

[0070]

[0071]

[0072] Step 35: Consider the above actuator fault model u F (t), then with actuator fault u FThe fuzzy system of (t) can be expressed as:

[0073]

[0074] For fuzzy systems with actuator faults, the following assumptions need to be ensured to be valid:

[0075] 1. All states of the forklift anti-rollover system are available at all times;

[0076] 2. For any actuator failure model of the forklift anti-rollover system (1-υ i )∈{υ i1 (t),…,υ iΦ (t)},{A i ,B i (1-υ i )} is unique and fully controllable;

[0077] 3. The non-parameterized E(t) is a continuous bounded function. The actuator fault and disturbance input are piecewise bounded continuous functions, that is, there is an unknown constant a greater than zero. E , Make ||E(t)||≤a e <∞, Established;

[0078] 4. For the forklift anti-rollover fault-tolerant system mentioned above, there exists a matrix function H with appropriate dimension: i , so that B = B i H i ;

[0079] 5. Regardless of any actuator fault model [1-υ i (t)]∈{υ i1 ,…,υ iΦ}, there is rank[B i (1-υ i )(t)]=rank[B].

[0080] The adaptive controller (2-10) ensures the update of the strategy by updating the adaptive law controller parameters (2-11). In the specific implementation, the following steps are performed:

[0081] Step 41, considering the linear time-invariant forklift anti-rollover fault-tolerant system fuzzy model (2-1), the controller model can be obtained as follows:

[0082]

[0083] In formula (2-10) At the same time, it is updated by the following adaptive law:

[0084]

[0085] Step 42: From step 1, Φ k is any positive constant, is limited, b k (k=1,2,…,N) is the matrix B i The kth column of Given as:

[0086]

[0087] Where α and β are appropriate positive numbers that satisfy:

[0088]

[0089] According to the adaptive correction rate, The update strategy is:

[0090]

[0091] In the above formula: κ is an arbitrary positive constant, is a finite function, and from the above formula we can see that when hour, Must satisfy

[0092] Step 43, from the above formula (2-9) and the controller model (2-10) in step 1 and the above assumption 4, the closed-loop fault-tolerant system with actuator failure can be obtained as:

[0093]

[0094] Theorem 1: For fuzzy systems with actuator failures and bounded disturbances, under the conditions of satisfying assumptions 1 to 5, the adaptive fault-tolerant control strategy shown in formulas (2-11) to (2-13) is adopted, and there exists a positive definite matrix P that satisfies the following inequality:

[0095]

[0096] Then the above-mentioned fuzzy closed-loop fault-tolerant closed-loop system (2-14) can be achieved to achieve asymptotic stability.

[0097] Step 44. Proof:

[0098] The corresponding candidate Lyapunov function is selected as:

[0099]

[0100] Then its derivative with respect to time is:

[0101]

[0102] According to the above assumption 3, the above formula can be deduced as follows:

[0103]

[0104] From Assumption 2 above, we can know that for a stable A i , B i There must be a positive definite matrix and P, such that:

[0105]

[0106] From the above assumption 5, we can know that there must be So that:

[0107]

[0108] Then we can know that:

[0109]

[0110] From Assumption 3, we know that there is an unknown constant a greater than zero e , Make ||E(t)||≤a e <∞, If true, then there must be a constant satisfy:

[0111]

[0112] definition:

[0113]

[0114] From the above adaptive laws (2-11) and (2-12), we can see that formula (2-14) can be written as:

[0115]

[0116] From the above formula (2-16), we can know that Q>0, and from the above formula (2-24), we can get Therefore, according to Lyaounov stability theory, when there is an actuator failure and external interference in the forklift anti-rollover system, the fault-tolerant controller designed above can ensure the global stability of the system.

[0117] Simulation Example

[0118] For the anti-rollover control system of the forklift vehicle dynamics model, a corresponding effective control strategy is designed so that when the forklift anti-rollover system actuator fails, the entire system can still be kept stable and the anti-rollover performance of the entire system can be guaranteed. In order to verify the effectiveness of the control strategy when the forklift anti-rollover control system actuator fails, a simulation verification is carried out. The parameters of the vehicle are shown in Table 1.

[0119] Table 1 Vehicle parameters

[0120]

[0121]

[0122] The fuzzy model of the forklift anti-rollover system is shown in the following formula, and its model parameters and system matrix are shown as follows:

[0123]

[0124] B i =[0.070 0 0.852 0]

[0125] B=[0.369 0 49.334 0]

[0126] In addition, bounded interference needs to be considered to meet practical needs, so the bounded interference is taken as: w(t) = 4sin(t) + 2, and the time when the interference starts in the system is t≥0. The initial state of the system is: x(0) = [3 0 0 4] T .

[0127] In order to verify the effectiveness of the adaptive method designed in this paper, simulations were performed under the following parameters:

[0128] α=2,β=20

[0129]

[0130] In the simulation, the system is set to operate normally when t≤5 with bounded interference. When t=5, the system actuator is set to fail, including two actuator failures, one of which is the uncontrollable part E(t)=10+3sin(t)+2cos(0.5t), and the unhealthy factor of the other actuator is υ=0.03t.

[0131] As a simulation example of the present invention, Figure 2 , Figure 3 , Figure 4They are the state response of the counterbalanced forklift anti-rollover system without fault, the state response under the normal controller with fault, and the state response of the fault-tolerant controller under fault. As can be seen from the figure, when the system is faulted at t=5s, the four controlled states in the system deviate from the origin, and a good control effect is obtained under the forklift anti-rollover system fault-tolerant controller, so that the four controlled states converge to zero again. The forklift anti-rollover system fault-tolerant controller can effectively improve the anti-rollover fault tolerance rate and the stability of the anti-rollover system during the turning process.

[0132] The following are examples:

[0133] As a practical example of the present invention, a test system is built based on the adaptive fault-tolerant control method. Under European standard road conditions, when the forklift is turning, the gyroscope sensor installed in the vehicle can collect the roll angle signal and yaw rate signal required by the controller. The controller receives and analyzes the sensor signal, and outputs the control current or control voltage through the internal drive circuit to control the actuator. The vehicle body signal acquisition sensor can also collect the roll angle and yaw rate signals, but the difference is that they are directly sent to the computer, and the computer records the data required for the test through the NAV-VIEW software.

[0134] In the experiment, the fault can be set by the following method: connect a resistor with a value of 0-100 in series between the drive output circuit and the hydraulic support cylinder solenoid valve. Ω Since the driving voltage output by the driving circuit will not change, when the potentiometer is added, the corresponding driving current will change with the change of the potentiometer resistance, and then the displacement of the solenoid valve core in the hydraulic support cylinder will change, resulting in a change in the actuator support force, which is equivalent to different faults in the actuator. The fault severity simulated after adjusting the potentiometer is divided into two conditions: fault level one and fault level two.

[0135] As an embodiment of the present invention, Figure 5 , Figure 6 , Figure 7 , Figure 8They are the body roll angle of the European standard test fault level 1, the vehicle yaw rate of the European standard test fault level 1, the body roll angle of the European standard test fault level 2, and the vehicle yaw rate of the European standard test fault level 2. Starting from the fault time t=5s, under the European standard road conditions, when the forklift turns, the fault is applied to the actuator by adjusting the resistance of the potentiometer. Compared with the non-fault-tolerant controller, the control effect of the adaptive fault-tolerant controller on the maximum value of the body roll angle is improved by 81.7%, and the maximum value of the vehicle yaw rate is improved by 53.7%. Compared with the non-fault-tolerant controller, the anti-rollover system under the control of the adaptive fault-tolerant controller can be stabilized 2 to 3 seconds earlier. The results show that when the actuator of the forklift anti-rollover system under the control of the adaptive fault-tolerant controller fails, the body roll angle and the vehicle yaw rate have a significant amplitude reduction effect compared with the non-fault-tolerant controller, and the fault-tolerant effect is significant, which corresponds to the simulation results, and the system eventually tends to be stable.

[0136] In yet another aspect, the present invention further discloses a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of any of the above methods.

[0137] On the other hand, the present invention further discloses a computer device, including a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of any of the above methods.

[0138] In another embodiment provided by the present application, a computer program product including instructions is also provided, which, when executed on a computer, enables the computer to execute the steps of any method in the above embodiments.

[0139] It is understandable that the system provided by the embodiment of the present invention corresponds to the method provided by the embodiment of the present invention, and the explanation, examples and beneficial effects of the relevant contents can refer to the corresponding parts in the above method.

[0140] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the program can be stored in a non-volatile computer-readable storage medium. When the program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0141] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0142] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive fault-tolerant control method for forklift actuator failure, characterized in that: The following steps are included: Setting the failure factor υ ij Used to cooperate with the uncertain control part caused by the forklift anti-rollover system actuator to determine the system actuator fault type; Set the actuator fault model u F (t) For all M forklift actuator failure models, a unique forklift anti-rollover system actuator failure model is described, providing actual control input for the forklift model with actuator failure; The fuzzy system model is set up to consider the vehicle body slip angular velocity, yaw angular velocity, frame roll angle, actuator fault control input, disturbance input and control output; The adaptive fault-tolerant controller is set up to update the parameters of the adaptive law controller and apply the Lyaounov stability theory to give sufficient conditions for the stability of the forklift anti-rollover system when there are actuator failures and external interference. Through formula (1-2), for all M forklift actuator fault models, it is expressed as the following unique fault model: u F (t)=(1-υ i )u(t)+ζ i u s (t)+E(t) (1-2) In formula (1-2), 1-υ i (t) = diag[υ i1 (t),…,υ im (t)]∈{υ i1 ,…,υ iΦ }; E(t) is the uncertain control part caused by the actuator of the forklift anti-rollover system; where u s (t) represents the non-decomposable actuator fault model in the counterbalanced forklift rollover fuzzy system.

2. The adaptive fault-tolerant control method for forklift actuator failure according to claim 1, characterized in that: The failure factor υ is obtained by formula (1-1) ij The range of the uncertain control part E(t) caused by the actuator failure is combined to distinguish the type of actuator failure:

3. The adaptive fault-tolerant control method for forklift actuator failure according to claim 1, characterized in that: Use formula (1-3) to build the forklift anti-rollover fuzzy system model: In formula (1-3), x c (t) represents the body state of the forklift, including the sideslip angular velocity, yaw angular velocity and frame roll angle; u(t) is the actual control input of the counterbalanced forklift rollover fuzzy system; w(t) is the external disturbance of the system.

4. The adaptive fault-tolerant control method for forklift actuator failure according to claim 1, characterized in that: The adaptive controller (1-4) ensures the update of the strategy by updating the adaptive law controller parameters (1-5): In formula (1-4), where Φ k is any positive constant, is limited, b k (k=1,2,…,N) is the matrix B i The kth column of 5. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 4.

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