A tower swing suppression control method and system based on event triggering

Abstract

The application discloses a tower crane swing suppression control method and system based on event triggering, belongs to the technical field of tower crane swing prevention, and is composed of a sensor, an actuator, a signal sending controller and the like. The control method has the functions of avoiding safety accidents and improving operation efficiency. The application can quickly suppress the swing of a load when the load inevitably swings during the use of a crane, until the swing angle is reduced to an acceptable range, thereby effectively avoiding safety accidents during the operation of the crane and improving the working efficiency of the crane.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of tower crane anti-swing, and particularly relates to a tower crane swing suppression control method and system based on event triggering. BACKGROUND

[0002] At present, as a common hoisting and transporting device, the tower crane is widely used in the transportation of large building materials on construction sites, and the tower crane also needs to change towards intelligence, high efficiency and safety.

[0003] In the hoisting process of goods, the transportation speed of the load should be as fast as possible in most cases to improve production efficiency. However, the change of the speed of the tower crane load trolley, the uneven distribution of the load mass and external environmental interference will cause the swing of the load, which may cause the load to collide with other working cranes or other objects, resulting in damage to the load and even serious safety accidents. Especially when the tower crane load trolley reaches the specified position and stops running, the load suspended below the load trolley will swing strongly, which seriously affects the accuracy and efficiency of the crane work. SUMMARY

[0004] The present application provides a tower crane swing suppression control method and system based on event triggering, which can improve the working efficiency of the tower crane and avoid safety hazards. On the one hand, the tower crane load trolley should be quickly brought to the specified position to meet the requirement of fast transportation of the load; on the other hand, the swing of the load needs to be quickly and effectively suppressed to improve the working efficiency of the crane. In order to meet the requirements of the two aspects, a controller that can effectively suppress the swing of the load needs to be designed, which has significant scientific research significance and practical value.

[0005] In order to achieve the above purpose, the present application provides a technical solution: a tower crane swing suppression control system based on event triggering, which is composed of a sensor, a signal conversion controller, an actuator and a tower crane load trolley; the tower crane load trolley is connected with the sensor, the sensor is connected with the signal conversion controller, the signal conversion controller is connected with the actuator, and the actuator is connected with the tower crane load trolley. The adaptive control system has the functions of avoiding safety accidents and improving work efficiency. The present application can quickly suppress the swing of the load when the load inevitably swings during the use of the crane, until the swing angle is reduced to an acceptable range, thereby effectively avoiding safety accidents during the operation of the crane and improving its working efficiency.

[0006] Preferably, the position sensor includes a position sensor and an angle sensor, both of which are used to collect the boundary state information of the tower crane load trolley, and the state information includes the relative displacement x(t) of the tower crane load trolley and the load, and the swing angle θ(t) of the rope below the load trolley.

[0007] Preferably, the signal transformer contained in the signal transformer controller compiles the state signal to obtain a control law that can make the system stable.

[0008] Preferably, the actuator receives the output signal of the signal transformer and acts on the driving motor of the tower crane load trolley to suppress the swing of the load.

[0009] Preferably, the signal transformer controller outputs the control signal u(t) acting on the actuator according to the boundary state information x(t) and θ(t) of the tower crane load trolley collected by the sensor, so as to update the working characteristics of the driving motor. In order to avoid the shock and heat loss caused by the too frequent change of the working characteristics of the actuator motor, the controller design adopts an output mode based on event triggering.

[0010] Preferably, the signal transformer controller has the following specific form:

[0011]

[0012]

[0013] Wherein a4, z4 are intermediate variables composed of the signals fed back by the sensor, σ(t) = 2e -0.5t In addition, the introduction of the correction term is to compensate for the measurement error caused by the triggering mechanism. Obviously, u(t) remains the same value in the time period t∈[t k , t k+1 ), and when the input error reaches the relative threshold value defined by the user, u(t) will be triggered to refresh and be assigned the same value as v(t). This method can avoid the shock and heat loss caused by the too frequent change of the working characteristics of the actuator motor.

[0014] Preferably, the sensor includes a position sensor and an angle sensor, the position sensor is installed on the load trolley, and the angle sensor is installed below the rope end of the load trolley of the tower crane.

[0015] Preferably, the event triggering based on event triggering refers to introducing an event triggering mechanism between the output of the signal transformer controller and the input of the actuator. First, the difference between the current output signal of the signal transformer controller and the last transmitted measurement value is defined as an error, and if the error reaches the threshold value defined by the user, the output signal of the signal transformer controller is refreshed.

[0016] In another aspect, based on the above-mentioned event-triggered tower crane swing suppression control system, the control process of the control system comprises: real-time measurement of the boundary state signal of the tower crane load trolley by the sensor to feed back to the signal transmission controller, the signal transmitter contained in the signal transmission controller compiles the state signal according to the given control law, and then judges the difference between the current signal transmission controller output signal and the last transmitted measurement signal, when the error reaches the threshold value, the signal transmission controller outputs a new control signal to the actuator, and acts on the drive motor of the tower crane load trolley to realize suppression of the swing of the load.

[0017] Due to the adoption of the above technical solutions, the technical progress achieved by the present application is:

[0018] The present application applies nonlinear system control to the tower crane swing suppression system, which can quickly suppress the swing of the load when the load inevitably swings during the use of the crane, until the swing angle is reduced to an acceptable range, thereby effectively avoiding safety accidents during the operation of the crane and improving the working efficiency.

[0019] The present application extends the event-triggered control to the tower crane anti-swing adaptive control system, which can effectively avoid the shock and heat loss caused by the too frequent change of the working characteristics of the actuator motor. In addition, the Zeno phenomenon refers to the infinite refreshing of the system in a limited time, which should be strictly avoided in the event-triggered mechanism. The Zeno phenomenon will not occur in the present application. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to illustrate the technical solutions adopted in the embodiments of the present application, the drawings involved in the present technical solution will be briefly introduced as follows.

[0021] Figure 1 The structural diagram of the present application;

[0022] Figure 2 The flowchart of the present application. DETAILED DESCRIPTION

[0023] In order to clarify the content, implementation means and technical advantages of the present application, the design process of the controller will be explained in detail in three steps in combination with the actual deployment situation of the tower crane system.

[0024] The actual deployment situation of the tower crane system is as follows:

[0025] The tower crane starts to run, the load swings in a large range, sensor reading state information, including position sensor and angle sensor, the position sensor is installed on the load trolley, the angle sensor is installed on the rope end below the load trolley of the tower crane, the state information is input to the adaptive controller to obtain a control signal, the signal is sent to the inverter to process the control signal and output to the actuator motor to suppress the load swing. The controller design includes the following steps:

[0026] First step: mathematical modeling for a kind of tower crane anti-swing nonlinear system:

[0027] 1.1: The work of the tower crane requires high stability and accuracy of the object, and the object is sent to the designated location by controlling the amplitude and rotation of the tower crane. The swing of the object is basically zero when performing vertical motion, and not only the tower crane load trolley is accurately positioned, but also the swing of the object to the designated position is zero. The constructed dynamic equation is as follows:

[0028]

[0029] Simplify to get

[0030]

[0031]

[0032] In the formula, θ represents the swing angle of the loaded object; x represents the relative position of the load and the tower crane load trolley, when x→0, the tower crane load trolley is accurately positioned, and the object reaches the designated position; L(t) represents the rope length of the suspended object, which is a bounded unknown function. M, m and g represent the mass of the tower crane load trolley, the mass of the load and the acceleration of gravity, respectively. F(x) is the force generated by the degree of freedom x in the system Lagrange equation. It is worth noting that the swing angle of the loaded object described in the application is an unmeasurable state. Let x1=x, x3=θ, u=F(x) is the system input, and the following state equation can be obtained:

[0033]

[0034] In the formula, b1=1, b3=1,

[0035] 1.2: Obviously, the nonlinear term of the tower crane anti-swing nonlinear system satisfies the following condition:

[0036]

[0037] S1.3: Before starting the controller design and stability analysis, the following coordinate transformation is introduced for the original nonlinear anti-swing system of tower crane:

[0038]

[0039] Therefore, the original system can be transformed into the following form:

[0040]

[0041] where Obviously, the stability of ζ i is completely equivalent to the stability of x i , so if the controller design can ensure ζ i → 0, then x i → 0 naturally holds.

[0042] 1.4: In this design, the initial value x i (0) of the anti-swing nonlinear system of tower crane is bounded, and the initial value y(0) of the output satisfies:

[0043] -G(0)<y(0)<G(0)

[0044] where G(x) is the output constraint condition, which will be defined later.

[0045] Second step: adaptive controller design under event-triggered mechanism:

[0046] According to the actual application situation, in view of the problems such as unknown length of hoisting rope, mass of load and trolley, error of load swing angle and angular velocity, and too long communication bandwidth, the control motor and actuator provide corresponding force to realize accurate positioning of the trolley and zero swing when the object reaches the specified position.

[0047] 2.1: In order to deal with the unmeasurable state ζ i in the anti-swing nonlinear system of tower crane in this design, a linear form observer is proposed, whose dynamics equation is as follows:

[0048]

[0049] where is the observer state, and real numbers a i (i = 1, 2, 3, 4) are the coefficients of the Hurwitz polynomials to be designed.

[0050] 2.2: Define the observer error as:

[0051]

[0052] Thus, the derivative of the error between the state variable of the system and the state estimate of the system unknown state corresponding to the observer can be obtained as follows:

[0053]

[0054] where

[0055] L = diag [Θm1, Θm2,..., Θm4],

[0056] f (·) = [f1(y, t, θ1), f2(y, t, θ2),..., f4(y, t, θ n )] T , a = [a1, a2,..., a4] T .

[0057] 2.3: For the observer error in this design, a Lyapunov function is selected as follows:

[0058] V e = e T Pe

[0059] where P is a symmetric positive definite matrix. According to the dynamic equation in step 2.2, we have For the nonlinear term, according to condition 1.2, we have where is a function greater than zero and smooth and derivable, l = 4n 2 ||P|| 2 , λ = 4||Pa|| 2 are all known constants, and θ = max{θ1, θ2,... θ4} is a constant unknown in sign and size. Then we can get:

[0060]

[0061] 2.4: Signal transmission controller design under event-triggered mechanism:

[0062] According to the actual application, for the unknown length of the hoisting rope, the mass of the load and the trolley, the error of the load swing angle and angular velocity, and the long communication bandwidth and a series of problems, the motor and the actuator provide the corresponding force to realize the accurate positioning of the trolley and the swing of the object to be zero when it reaches the specified position. The signal transmission controller has the following expression:

[0063]

[0064]

[0065] where a4 is a virtual controller of the system, which will be given in the stability analysis. s(t) = 2e -0.5tIn addition, the introduction of the amendment is to compensate for the measurement error caused by the trigger mechanism. Obviously, in the time period t∈[t k ,t k+1 ) u(t) remains the same value, when the input error reaches the user-defined relative threshold, u(t) will be triggered to refresh and be assigned the same value as v(t). This method can save a lot of communication costs while ensuring system performance, saving bandwidth.

[0066] Step 3: Stability analysis

[0067] This part proves the role of the controller and its functions in theory.

[0068] 3.1 First, introduce the following coordinate transformation:

[0069]

[0070] Where a i is a smooth differentiable function, representing the virtual controller that needs to be designed at the i-th step of the system. Define as an unknown constant, let Where represents the estimate of the unknown parameter , Where represents the estimate of the unknown parameter Θ.

[0071] 3.2 Select the first barrier Lyapunov function as It is not difficult to see that when y→±G(t), V→∞, so as long as V can be guaranteed to be bounded, the output y can be strictly constrained within the range of ±G(t)

[0072] The first virtual controller is designed as:

[0073]

[0074]

[0075]

[0076] Where N(k) is a class of Nussbaum functions. From this we can derive:

[0077]

[0078] Where

[0079] 3.3: Select the second Lyapunov function as

[0080] The second virtual controller is designed as:

[0081]

[0082] Thus, it can be derived that:

[0083]

[0084] wherein

[0085] 3.4 Given the Lyapunov function is: The nth virtual controller is designed as: The nth virtual controller is designed as:

[0086]

[0087] wherein

[0088] Thus, it can be derived that:

[0089]

[0090] Given the adaptive law Finally, it can be derived that:

[0091]

[0092] 3.5: It can be derived from step 3.4 that

[0093] That is, the tower crane anti-swing nonlinear system in the present application realizes asymptotic convergence.

[0094] The above is only a specific embodiment of the present application, any feature disclosed in the specification can be replaced by other equivalent or similar purpose alternative features, unless specifically stated, and any modification or improvement of the technical solutions of the present application made by those skilled in the art without departing from the spirit of the present application shall fall within the scope of protection of the claims of the present application.

Claims

1. A tower crane swing suppression control system based on event triggering, characterized in that: It includes a sensor, a signal transmission controller, an actuator and a tower crane loading trolley; wherein the tower crane loading trolley is connected to the sensor, the sensor is connected to the signal transmission controller, the signal transmission controller is connected to the actuator, and the actuator is connected to the tower crane loading trolley; The specific form of the signal transmission controller is as follows: Where α4 is the virtual controller of the system, z4 is the intermediate variable of the system state variable after coordinate transformation, σ(t)=2e -0.5t In addition, the correction The introduction of is to compensate for the measurement error caused by the trigger mechanism; obviously, at t∈[t k ,t k+1 ) period, u(t) remains constant. When the input error reaches a relative threshold defined by the user, u(t) is triggered to refresh and assigned the same value as v(t). This method can prevent the actuator motor from changing its operating characteristics too frequently, which can cause oscillation and heat loss.

2. The tower crane swing suppression control system based on event triggering according to claim 1 is characterized in that: The sensors include a position sensor and an angle sensor, which are used to collect boundary state information of the tower crane trolley. The state information includes the relative displacement x(t) of the tower crane trolley and the swing angle θ(t) of the rope below the trolley.

3. The event-triggered tower crane swing suppression control system according to claim 1, characterized in that: The signal transmitter included in the signal transmission controller will compile the state signal to obtain a control law that can stabilize the system.

4. The tower crane swing suppression control system based on event triggering according to claim 1, characterized in that: The actuator is used to receive the output signal of the signal transmission controller and act on the drive motor of the load trolley of the tower crane to suppress the swing of the load.

5. The tower crane swing suppression control system based on event triggering according to claim 1 is characterized in that: The signal transmission controller is used to output a control signal u(t) acting on the actuator based on the boundary state information x(t) and θ(t) of the tower crane trolley collected by the sensor.

6. The event-triggered tower crane swing suppression control system according to claim 1, characterized in that: The signal transmission controller adopts an output mode based on event triggering.

7. The tower crane swing suppression control system based on event triggering according to claim 1 is characterized in that: The event-based triggering refers to the introduction of an event triggering mechanism between the output of the signal transmission controller and the input of the actuator. First, the difference between the current output signal of the signal transmission controller and the last transmitted measurement value is defined as the error. If the error reaches the threshold defined by the user, the output signal of the signal transmission controller is refreshed.

8. The method of controlling a tower crane swing suppression system based on event triggering according to any one of claims 1 to 7, characterized in that: The control process of the control system includes: the sensor measures the boundary state signal of the tower crane load trolley in real time and feeds it back to the signal transmitter controller. The signal transmitter contained in it compiles the state signal according to a given control law, and judges the difference between the current signal transmitter controller output signal and the last transmitted measurement signal. When the error reaches the threshold, the signal transmitter controller will output a new control signal to the actuator, and act on the drive motor of the tower crane load trolley to suppress the swing of the load.

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