Tower crane slewing control mechanism and its control method

Abstract

The present invention provides a slewing control mechanism for a tower crane, comprising an asynchronous motor and a slewing inverter connected to the asynchronous motor, the slewing inverter is used to drive the asynchronous motor, and the asynchronous motor is used to drive the slewing mechanism in the tower crane to operate; and further comprising a correction module, which is used to correct the command speed of the asynchronous motor, and input the corrected command speed to the asynchronous motor, so as to achieve the effect of de-jittering the slewing mechanism. The present invention eliminates the jitter of the slewing mechanism speed curve, realizes stable start and stop, and cooperates with the zero-frequency brake function of the inverter itself, so as to realize smooth control without using an eddy current controller and increase the stability of the slewing system.

Description

Technical Field

[0001] The present invention relates to the field of motor speed control system, and particularly to a slewing control mechanism of a tower crane and a control method thereof. Background Art

[0002] In tower cranes, traditional control methods include OMD and RCV, etc., which have the disadvantages of high maintenance cost and high energy consumption. With the development of power electronics technology and computer control technology, in small tower cranes, slewing frequency conversion control gradually replaces the traditional method.

[0003] Since the slewing mechanism belongs to a large inertia elastic load, when the asynchronous motor speed is used as the control target, there is a problem of unstable slewing control of the slewing mechanism. This results in low actual production efficiency and certain requirements for operators.

[0004] For the control of the frequency conversion driven slewing mechanism, there are currently two main control schemes:

[0005] One method is to adopt a closed-loop control method, which mainly realizes compensation by estimating the slewing speed of the tower crane. The necessary condition for closed-loop control is to obtain accurate motor parameters of the asynchronous motor and the encoder feedback speed, and adding the estimation of the slewing speed can achieve stable control of the slewing mechanism. However, the closed-loop control will increase the risk of encoder damage, and not all tower crane manufacturers have the conditions for closed-loop control, and there is great cost pressure for upgrading the open-loop control scheme in the original market, and the operation is complex.

[0006] Another method is the open-loop control method, which suppresses the instability of the slewing mechanism during operation by generating a specific speed curve. This method analyzes the engineering model of the tower crane, inputs a specific speed curve to the model and observes the output curve of the model. A large number of experiments and tests show that this method has good adaptability and performance in actual production. In addition, this method uses open-loop control, which is stable and reliable, and has low on-site upgrade difficulty. Summary of the Invention

[0007] In view of the above problems existing in the prior art, the present invention proposes a slewing control mechanism of a tower crane and a control method thereof.

[0008] The present invention provides a slewing control mechanism of a tower crane, including an asynchronous motor and a slewing frequency converter connected to the asynchronous motor. The slewing frequency converter is used to drive the asynchronous motor, and the asynchronous motor is used to drive the slewing mechanism in the tower crane to operate. It further includes a correction module, which is used to correct the command speed of the asynchronous motor through a correction model and input the corrected speed to the asynchronous motor to achieve the effect of eliminating jitter of the slewing mechanism.

[0009] In the tower crane slewing control mechanism provided by the present invention, the correction module corrects the command speed through the following correction model:

[0010]

[0011] Among them, ω Ref represents the command speed of the asynchronous motor, α represents the acceleration of the asynchronous motor, ω comp It represents the velocity after the acceleration passes through the first-order inertial filter, ω m represents the corrected command speed of the asynchronous motor, τ represents the time constant, K represents the proportional coefficient, and s represents the differential.

[0012] According to another aspect of the present invention, there is also provided a control method for the slewing control mechanism of the tower crane as described above, comprising the following steps:

[0013] The command speed ω of the asynchronous motor is adjusted by the correction model Ref Make corrections;

[0014] The corrected command speed ω of the asynchronous motor m Input to the asynchronous motor.

[0015] The asynchronous motor is controlled according to the corrected command speed ω m The slewing mechanism in the tower crane is driven to operate.

[0016] In the control method provided by the present invention, the correction model is:

[0017]

[0018] Among them, ω Ref represents the command speed of the asynchronous motor, α represents the acceleration of the asynchronous motor, ω comp It represents the velocity after the acceleration passes through the first-order inertial filter, ω m represents the command speed of the asynchronous motor after correction, τ represents the time constant, K represents the proportional coefficient, and s represents the differential. The implementation of the embodiment of the present invention has the following beneficial effects: the slewing open-loop control method provided by the present invention can be applied to slewing mechanisms of different models, reducing the mechanical stress of the tower body during acceleration and deceleration, while the current during the operation of the inverter is also reduced, thereby increasing the service life of the tower crane; since the jitter of the speed curve is eliminated and stable start and stop are achieved, in combination with the zero-frequency brake function of the inverter itself, smooth control can be achieved without using an eddy current controller, thereby increasing the stability of the slewing system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on these drawings.

[0020] Figure 1 The figure shows a module diagram of a slewing control mechanism of a tower crane provided by an embodiment of the present invention;

[0021] Figure 2 The figure shows a schematic diagram of the control structure of the present invention;

[0022] Figure 3 is Figure 2 The figure shows the result diagrams of each stage;

[0023] Figure 4 The figure shows a result comparison diagram before and after calibration;

[0024] Figure 5 is a simulation using MATLAB;

[0025] Figure 6 is a simulation waveform. Detailed implementation manners

[0026] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively with reference to the relevant accompanying drawings. The typical embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0027] It should be noted that the terms "connected" or "coupled", unless otherwise defined, not only include directly connecting two entities. All technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] The general idea of the present invention is: by means of series calibration, subtract the calibrated speed from the forward path of the speed output curve to obtain an output similar to an S-curve, thereby eliminating jitter.

[0029] To better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings of the specification and specific implementation manners. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present application, rather than limitations on the technical solution of the present application. Without conflict, the technical features in the embodiments of the present invention and the embodiments can be combined with each other.

[0030] Figure 1 The following is a schematic diagram of the slewing control mechanism of a tower crane provided by an embodiment of the present invention; as Figure 1 shown, the slewing control mechanism provided by the present invention includes an asynchronous motor 20 and a slewing frequency converter 10 electrically connected to the asynchronous motor. The slewing frequency converter is used to drive the asynchronous motor, and the asynchronous motor is used to drive the slewing mechanism 30 in the tower crane to operate. It further includes a correction module 40 for correcting the commanded speed of the asynchronous motor through a correction model and inputting the corrected speed to the asynchronous motor to achieve the effect of eliminating jitter of the slewing mechanism.

[0031] Specifically, in an embodiment of the present invention, Figure 2 is the control structure of the present invention. The part within the dashed box is the added correction link, and the other parts are the original speed control of the frequency converter. The correction link is composed of a differential link and a first-order inertia link. The user can set the time constant τ and the proportional coefficient K of the first-order inertia link through the frequency converter keyboard. The correction model is as follows:

[0032]

[0033] ω Ref represents the commanded speed of the asynchronous motor, α represents the acceleration of the asynchronous motor, ω comp represents the speed after the acceleration passes through a first-order inertia filter, ω m represents the corrected commanded speed of the asynchronous motor, τ represents the time constant, K represents the proportional coefficient, and s represents differentiation.

[0034] The correction result is as Figure 3 and Figure 4 shown, where the line ① represents the original speed curve ω Ref , the line ② represents the output acceleration α, the line ③ represents the speed ω comp after the acceleration passes through a first-order inertia filter, and the line ④ represents the synthesized actual frequency converter output speed ω m . Figure 4 In Ref , the line ⑤ represents the actual speed of the slewing jib when the original speed curve ω m (line ①) is output, and the line ⑥ represents the actual speed of the jib after output according to ω Figure 5 is the simulation using MATLAB.Figure 6 is the simulation waveform. Figure 6 It can be seen that the present invention uses a serial correction method to subtract the corrected speed from the forward channel of the speed output curve to obtain an output similar to an S curve, thereby eliminating jitter.

[0035] Based on the same inventive concept, the present invention also discloses a control method for a slewing control mechanism of a tower crane, which is characterized by comprising the following steps:

[0036] The command speed ω of the asynchronous motor is adjusted by the correction model Ref Make corrections;

[0037] The corrected command speed ω of the asynchronous motor m Input to the asynchronous motor.

[0038] The asynchronous motor is controlled according to the corrected command speed ω m The slewing mechanism in the tower crane is driven to operate.

[0039] The calibration model is as follows:

[0040]

[0041] ω Ref represents the command speed of the asynchronous motor, α represents the acceleration of the asynchronous motor, ω comp It represents the velocity after the acceleration passes through the first-order inertial filter, ω m represents the corrected command speed of the asynchronous motor, τ represents the time constant, K represents the proportional coefficient, and s represents the differential.

[0042] The slewing open-loop control method provided by the present invention can be applied to slewing mechanisms of different models, reduce the mechanical stress of the tower body during acceleration and deceleration, and reduce the current during the operation of the inverter, thereby increasing the service life of the tower crane. Since the jitter of the speed curve is eliminated and stable start and stop are achieved, the zero-frequency brake function of the inverter itself can be used to achieve smooth control without using an eddy current controller, thereby increasing the stability of the slewing system.

[0043] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A slewing control mechanism for a tower crane, comprising an asynchronous motor and a slewing frequency converter connected to the asynchronous motor, the slewing frequency converter being used to drive the asynchronous motor, and the asynchronous motor being used to drive the slewing mechanism in the tower crane to operate, Characterized in that, it further comprises a correction module for correcting the commanded speed of the asynchronous motor and inputting the corrected commanded speed to the asynchronous motor; The correction module corrects the commanded speed through the following correction model: where ω Ref represents the commanded speed of the induction motor, α represents the acceleration of the induction motor, and ω comp represents the speed after the acceleration passes through a first-order inertial filter, and ω m represents the corrected commanded speed of the induction motor, τ represents the time constant, K represents the proportionality coefficient, and s represents the differential.

2. A control method for the slewing control mechanism of the tower crane according to claim 1, Characterized in that, it comprises the following steps: The command speed ω of the asynchronous motor is corrected by a correction model Ref for correction; Input the corrected commanded speed ω of the asynchronous motor m to the asynchronous motor; The asynchronous motor drives the slewing mechanism in the tower crane according to the corrected command speed ω m ; The correction model is: Among them, ω Ref represents the commanded speed of the induction motor, α represents the acceleration of the induction motor, and ω comp represents the speed after the acceleration passes through a first-order inertial filter, and ω m represents the corrected commanded speed of the induction motor, τ represents the time constant, K represents the proportionality coefficient, and s represents the differential.

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