A bridge crane anti-sway method and system based on switching control

Abstract

This invention provides a method and system for anti-swaying a bridge crane based on switching control, including a trolley and a spreader, comprising the following steps: obtaining the target position of the trolley; calculating the acceleration trajectory of the trolley based on its pendulum period; when the trolley reaches the target position, obtaining the angular velocity of the spreader; calculating the control force applied to the trolley based on the angular velocity of the spreader; and completing anti-swaying when the angular velocity of the spreader is less than a preset threshold; detecting the real-time position of the trolley; and using a variable proportional controller to return the trolley to the target position based on the error between the real-time position and the target position. The anti-swaying method and system for a bridge crane based on switching control provided by this invention ensures that the swing angle of the spreader can be constrained within a defined threshold during the trolley's movement, and guarantees that the trolley can quickly suppress the swing angle to zero at the target position.

Description

Technical Field

[0001] This invention relates to the field of control technology for bridge cranes, and in particular to an anti-sway method and system for bridge cranes based on switching control. Background Technology

[0002] Bridge cranes, as heavy-duty material handling equipment, are widely used in industrial sites such as ports, construction sites, and warehouses. With the improvement of production levels, bridge cranes are playing an increasingly important role in industrial automation. However, the biggest problem affecting the conveying efficiency of bridge crane systems is the swaying of the bottom spreader during the movement of the top trolley. This swaying not only reduces conveying efficiency and affects the accuracy of the container, but can even lead to collisions and safety issues. Since bridge cranes are underactuated systems, the swaying of the spreader cannot be directly controlled; it can only be indirectly suppressed through the displacement of the top trolley. This presents a significant challenge to the control of bridge cranes. Therefore, researching anti-sway control methods for bridge cranes is of great significance for improving operational efficiency, ensuring safety, and enhancing automation levels in industrial settings.

[0003] In existing technologies, the mainstream practice in industrial settings is for experienced workers to manually control the crane's movement by observing the sway of the spreader. To reduce on-site operating costs, there is an urgent need to achieve unmanned crane movement. Some existing anti-sway control methods for bridge cranes minimize the spreader's sway angle by moving the top trolley, but they cannot constrain the sway angle within a defined threshold. If the sway angle cannot be constrained within a defined threshold, excessive sway angles will pose safety hazards in industrial settings. Even methods with defined sway angle constraints are implemented through open-loop control, making them highly susceptible to wind interference during operation, which can cause the sway angle to exceed the threshold at the target position.

[0004] To address the contradiction that open-loop control methods can achieve swing angle constraints but cannot actively eliminate swing or cope with external disturbances, while closed-loop control methods can achieve active swing elimination and have a certain degree of anti-interference capability but cannot achieve swing angle threshold constraints, a method for preventing swaying of bridge cranes is needed to solve these problems. Summary of the Invention

[0005] This invention provides a bridge crane anti-sway method and system based on switching control, which enables the swing angle of the lifting device to be constrained within a certain threshold during the movement of the trolley, and ensures that the trolley can quickly suppress the swing angle to zero at the target position.

[0006] This invention provides a method for preventing swaying of a bridge crane based on switching control, comprising a trolley and a lifting device, and including the following steps:

[0007] Obtain the target position of the trolley, and calculate the acceleration trajectory of the trolley based on the pendulum period of the trolley.

[0008] When the trolley reaches the target position, the angular velocity of the lifting device is obtained, and the control force applied to the trolley is obtained based on the angular velocity of the lifting device. When the angular velocity of the lifting device is less than a preset threshold, the swaying is eliminated.

[0009] The real-time position of the trolley is detected, and based on the error value between the real-time position and the target position, a variable proportional controller is used to return the trolley to the target position.

[0010] Preferably, before obtaining the target position of the trolley, the method further includes establishing a single-input, quadratic-output underactuated model based on the displacement of the trolley and the swing angle of the lifting device:

[0011]

[0012] Where M is the mass of the trolley, m is the mass of the lifting device, l is the rope length, θ is the swing angle of the lifting device, x is the displacement of the trolley, F is the control force applied to the trolley, and g is the acceleration due to gravity.

[0013] Preferably, the pendulum period of the trolley is calculated using the following formula:

[0014]

[0015] Where, ω n Let l be the pendulum frequency of the trolley, l be the rope length, and g be the acceleration due to gravity.

[0016] Preferably, the acceleration trajectory planning of the trolley is based on the embedded slope acceleration trajectory planning, and is calculated using the following formula:

[0017] When 0≤t≤τ1,

[0018] When τ1≤t≤T aux1 When -τ1,

[0019] When T aux1 -τ1≤t≤T aux1 hour,

[0020] When T aux2 ≤t≤T aux2 When +τ1,

[0021] When T au +τ1≤t≤Tau hour,

[0022] When T aux3 ≤t≤T aux4 hour,

[0023] Other situations

[0024] Where τ1 is an adjustable parameter, and its value range is ω n Let a be the pendulum frequency of the trolley. 1max T is the maximum acceleration value during the translational motion of the trolley. aux ,T au ,T aux3 ,T aux4 It is a constant that is related to the period T of the simple pendulum.

[0025] Preferably, the control force applied to the trolley, based on the angular velocity of the lifting device, is calculated using the following formula:

[0026]

[0027] Where k is an adjustable constant. This indicates the angular velocity of the lifting device.

[0028] Preferably, the range of the preset threshold is -0.05 rad / s to 0.05 rad / s.

[0029] Preferably, the method for returning the trolley to the target position using a variable proportional controller is calculated based on the error value between the target position and the real-time position using the following formula:

[0030] e = x r -x

[0031] u=α(e)*e

[0032] α(e)=Ae

[0033] Where x represents the real-time position of the trolley, x r Let represent the target position of the trolley, e represent the error value between the target position and the real-time position, α(e) is a variable parameter that changes with the error value e, and A is a constant.

[0034] Preferably, when the trolley has not reached the target position, the variable proportional controller continues to use to make the trolley return to the target; when the trolley reaches the target position, the control ends.

[0035] This invention also provides a bridge crane anti-sway system based on switching control, comprising: a server, the server including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method described above.

[0036] This invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the method described in any of the preceding embodiments.

[0037] Compared with the prior art, the technical solution of the embodiments of the present invention has the following beneficial effects:

[0038] The anti-sway method and system for bridge cranes based on switching control according to this invention consists of three stages. The first stage is to obtain the target position of the trolley and plan the acceleration trajectory of the trolley based on the single pendulum period of the trolley. The second stage is to obtain the angular velocity of the spreader when the trolley reaches the target position and obtain the control force applied to the trolley based on the angular velocity of the spreader. When the angular velocity of the spreader is less than a preset threshold, the sway is eliminated. The third stage is to detect the real-time position of the trolley and use a variable proportional controller to return the trolley to the target position based on the error value between the target position and the real-time position. Through staged control, the first stage ensures that the trolley can reach the target position and the sway angle is limited to a certain and safe threshold. The second stage makes the sway angle quickly converge to a minimum value. The third stage makes the trolley return to the target position, and during the movement, the converged spreader sway angle no longer diverges. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention, but not all embodiments. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 A flowchart of a bridge crane anti-sway method based on switching control provided in an embodiment of the present invention;

[0041] Figure 2 A physical model of a bridge crane provided for one embodiment of the present invention;

[0042] Figure 3A A schematic diagram of acceleration trajectory planning for a bridge crane anti-sway method based on switching control, provided as an embodiment of the present invention;

[0043] Figure 3B A schematic diagram of speed trajectory planning for a bridge crane anti-sway method based on switching control, provided as an embodiment of the present invention;

[0044] Figure 3C A schematic diagram of displacement trajectory planning for a bridge crane anti-sway method based on switching control, provided as an embodiment of the present invention;

[0045] Figure 4 A comparison diagram of position waveforms for a bridge crane anti-sway method based on switching control, provided as an embodiment of the present invention;

[0046] Figure 5 An angle waveform comparison diagram of a bridge crane anti-sway method based on switching control provided in an embodiment of the present invention. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] The technical solution of the present invention will be described in detail below with reference to specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0049] Based on the problems existing in the prior art, the present invention provides a bridge crane anti-sway method and system based on switching control, which enables the swing angle of the spreader to be constrained within a certain and safe threshold during the movement of the trolley, and ensures that the trolley can quickly suppress the swing angle to zero at the target position.

[0050] Figure 1 A flowchart of a bridge crane anti-sway method based on switching control is provided as an embodiment of the present invention. Figure 2 A physical model of a bridge crane provided in one embodiment of the present invention. Now see Figure 1 and Figure 2 This invention provides a method for preventing swaying of a bridge crane based on switching control, comprising a trolley and a lifting device, and including the following steps:

[0051] Step S102: Obtain the target position of the trolley, and plan the acceleration trajectory of the trolley based on the pendulum period of the trolley.

[0052] Step S104: When the trolley reaches the target position, the angular velocity of the lifting device is obtained, and the control force applied to the trolley is obtained based on the angular velocity of the lifting device. When the angular velocity of the lifting device is less than a preset threshold, the swaying is eliminated.

[0053] Step S106: Detect the real-time position of the trolley, and use a variable proportional controller to return the trolley to the target position based on the error value between the real-time position of the trolley and the target position of the trolley.

[0054] In practice, by Figure 2 As can be seen from the physical model, the bridge crane is an underactuated system. The only control variable of the system is the control force F applied to the trolley, and the output variables are the displacement x of the trolley and the swing angle θ of the spreader. Before step S102, step S101 is included: establishing a single-input, quadratic-output underactuated model based on the displacement of the trolley and the swing angle of the spreader.

[0055]

[0056] Where M is the mass of the trolley, m is the mass of the lifting device, l is the rope length, θ is the swing angle of the lifting device, x is the displacement of the trolley, F is the control force applied to the trolley, and g is the acceleration due to gravity.

[0057] For bridge crane systems, the control objective is to bring the trolley to the target position while minimizing the swing angle of the spreader during the movement. Due to the underactuated nature of the system, the spreader's swing can only be suppressed by the movement of the trolley, thus posing a significant challenge to control.

[0058] In specific implementation, the pendulum period of the trolley in step S102 is calculated using the following formula:

[0059]

[0060] Where, ω n Let l be the pendulum frequency of the trolley, l be the rope length, and g be the acceleration due to gravity.

[0061] From the physical model of the bridge crane system, it can be seen that it can be equivalent to a simple pendulum model, and the natural frequency of the pendulum is: The period of a simple pendulum is: Therefore, as long as the acceleration and deceleration times during the trolley's movement are equal to the pendulum period T, it can be guaranteed that the lifting device will have both a zero swing angle and a zero angular velocity after acceleration and deceleration. This ensures that the swing angle during the trolley's movement is limited to a defined and safe threshold, and that when the target position is reached, both the swing angle and angular velocity are zero, with no residual oscillation.

[0062] In specific implementation, in step S102, in order to achieve an acceleration and deceleration process with a period of T, the acceleration trajectory of the trolley is planned as an acceleration trajectory based on an embedded slope, which is calculated using the following formula:

[0063] When 0≤t≤τ1,

[0064] When τ1≤t≤T aux1 When -τ1,

[0065] When T aux1 -τ1≤t≤T aux1 hour,

[0066] When T aux2 ≤t≤T aux2 When +τ1,

[0067] When T aux2 +τ1≤t≤T aux3 hour,

[0068] When T aux3 ≤t≤T aux hour,

[0069] Other situations

[0070] Where τ1 is an adjustable parameter, and its value range is That is to say ω n Let a be the pendulum frequency of the trolley. 1max T is the maximum acceleration value during the translational motion of the trolley. aux1 ,T aux ,T aux3 ,T aux4 It is a constant that is related to the period T of the simple pendulum.

[0071] The acceleration, velocity, and position obtained from the acceleration trajectory planning based on the embedded slope are shown in Figure 3A. Figure 3B , Figure 3C As shown.

[0072] By using the above-mentioned acceleration trajectory planning method based on embedded slope, the motion trajectory of the trolley can be tracked to the planned position, thus achieving the effects of trolley positioning and anti-swaying of the lifting device.

[0073] Specifically, Figure 3A , Figure 3B , Figure 3CThe waveforms of the trolley's planned acceleration, velocity, and position shown take into account the coupling between the trolley and the load of the lifting device. By using the PID method to make the actual movement position of the trolley track the planned position, the trolley positioning and the lifting device anti-sway effect can be achieved.

[0074] In industrial settings, due to model uncertainties and susceptibility to external interference such as wind, as well as issues like time delay, dead zones, and saturation in actuators, the aforementioned acceleration trajectory planning method based on embedded ramps, while ensuring that the swing angle is constrained within the desired threshold during motion, still results in residual oscillations at the target position. These residual oscillations not only pose safety hazards but also cause inconvenience to subsequent operations.

[0075] Therefore, it is necessary to monitor the swing angle information of the spreader at the target position and use this information to control the movement of the control vehicle so that the swing angle of the spreader at the target position can quickly converge to zero.

[0076] In specific implementation, in step S104, the control force applied to the trolley based on the angular velocity of the lifting device is calculated using the following formula:

[0077]

[0078] Where k is an adjustable constant. This indicates the angular velocity of the lifting device.

[0079] The desired swing angle of the lifting device is zero. However, due to the susceptibility of on-site sensors to noise and interference, and the inherent bias in angle measurements caused by sensor installation positions, the measured swing angle may not be zero even when the swing angle is zero. Therefore, in practice, the swing angle bias is mitigated by detecting the angular velocity of the lifting device; that is, the trolley tracks the angular velocity of the lifting device to eliminate the swing.

[0080] In practice, the amplitude of the angular velocity of the spreader will be continuously monitored. When the amplitude of the angular velocity of the spreader is less than a preset threshold, it can be considered that the sway elimination has been completed. The preset threshold ranges from -0.05 rad / s to 0.05 rad / s.

[0081] In practical implementation, based on the error value between the target position and the real-time position, the variable proportional controller is used to return the trolley to the target position, which is calculated using the following formula:

[0082] e = x r -x

[0083] u=α(e)*e

[0084] α(e)=Ae

[0085] Where x represents the real-time position of the trolley, x r Let represent the target position of the trolley, e represent the error value between the target position and the real-time position, α(e) is a variable parameter that changes with the error value e, and A is a constant.

[0086] The above-described method of eliminating sway by controlling the movement of the control trolley has completed the sway elimination task, and the sway angle of the spreader has approximately converged to zero. However, due to the movement of the trolley, it is not currently at the target position, but rather near it. To ensure the trolley returns to the target position and that the sway angle of the spreader, which has converged to zero, does not diverge further during this process, a variable proportional controller is used to guide the trolley back to the target position. Here, A is a constant, so α(e) increases as the position error e decreases. Using this control method, the trolley can return to the target position at a slow speed, and during the trolley's movement, the sway angle of the spreader, which has converged to zero, will not diverge again. Ultimately, when the trolley reaches the target position, the sway angle of the spreader also converges to zero.

[0087] If the trolley does not reach the target position, the variable proportional controller continues to drive the trolley back to the target position. When the trolley reaches the target position, the control ends.

[0088] Figure 4 A position waveform comparison diagram of a bridge crane anti-sway method based on switching control provided in an embodiment of the present invention. Figure 5 An angle waveform comparison diagram of a bridge crane anti-sway method based on switching control provided in an embodiment of the present invention. Now refer to... Figure 4 and Figure 5 Waveform 1 is the system response waveform diagram corresponding to the trajectory planning method using only the embedded ramp. Waveform 2 is the system response waveform diagram corresponding to the bridge crane anti-sway method based on switching control in this invention.

[0089] Specifically, during the 0-16s period, both waveform 1 and waveform 2 use the trajectory planning method with embedded ramps, which is... Figure 5 It can be seen that the spreader's swing angle experiences a negative swing and a positive swing, with a maximum swing angle of 1.45 degrees. At 16 seconds, the swing angle is near 0 degrees. The maximum swing angle can be limited using the trajectory planning method embedded with the ramp described earlier. This ensures that the spreader's swing angle is kept within a defined and safe threshold during movement.

[0090] After 16 seconds, if the switching control method described in this application is not used, as shown in waveform 1, the swing angle of the spreader will have residual oscillation; while if the switching control method described in this application is used, as shown in waveform 2, the swing angle of the spreader can quickly converge to 0 degrees without residual oscillation.

[0091] Depend on Figure 4 and Figure 5 As can be seen from the waveform comparison, the anti-sway method for bridge cranes based on switching control in this application can not only ensure that the swing angle of the spreader can be limited within a certain and safe threshold during the translation of the trolley, but also eliminate the residual swing of the spreader at the target position.

[0092] This invention also provides a bridge crane anti-sway system based on switching control, comprising: a server, the server including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method described above.

[0093] This invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the method described in any of the preceding embodiments.

[0094] In summary, the anti-sway method and system for bridge cranes based on switching control according to embodiments of the present invention are divided into three stages. The first stage is to obtain the target position of the trolley and plan the acceleration trajectory of the trolley based on the single pendulum period of the trolley. The second stage is to obtain the angular velocity of the spreader when the trolley reaches the target position, and obtain the control force applied to the trolley based on the angular velocity of the spreader. When the angular velocity of the spreader is less than a preset threshold, the sway is eliminated. The third stage is to detect the real-time position of the trolley and use a variable proportional controller to return the trolley to the target position based on the error value between the target position and the real-time position. Through staged control, the first stage ensures that the trolley can reach the target position and the swing angle of the spreader is limited to a safe and definite threshold. The second stage makes the swing angle converge rapidly to a minimum value. The third stage makes the trolley return to the target position, and during the movement, the converged swing angle of the spreader no longer diverges.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing swaying of a bridge crane based on switching control, comprising a trolley and a lifting device, characterized in that, Includes the following steps: Obtain the target position of the trolley, and calculate the acceleration trajectory of the trolley based on the pendulum period of the trolley. When the trolley reaches the target position, the angular velocity of the lifting device is obtained, and the control force applied to the trolley is obtained based on the angular velocity of the lifting device. When the angular velocity of the lifting device is less than a preset threshold, the swaying is eliminated. The real-time position of the trolley is detected, and based on the error value between the real-time position and the target position, a variable proportional controller is used to return the trolley to the target position. The control force applied to the trolley, based on the angular velocity of the lifting device, is calculated using the following formula: Where k is an adjustable constant. This indicates the angular velocity of the lifting device; The range of the preset threshold is -0.05 rad / s to 0.05 rad / s; Based on the error value between the target position and the real-time position, the return of the trolley to the target position using a variable proportional controller is calculated using the following formula: e=x r -x u=α(e)*e α(e)=Ae Where x represents the real-time position of the trolley, x r Let represent the target position of the trolley, e represent the error value between the target position and the real-time position, α(e) is a variable parameter that changes with the error value e, and A is a constant.

2. The anti-sway method for bridge cranes based on switching control according to claim 1, characterized in that, Before obtaining the target position of the trolley, a single-input, quadratic-output underactuated model is established based on the displacement of the trolley and the swing angle of the lifting device. Where M is the mass of the trolley, m is the mass of the lifting device, l is the rope length, θ is the swing angle of the lifting device, x is the displacement of the trolley, F is the control force applied to the trolley, and g is the acceleration due to gravity.

3. The anti-sway method for bridge cranes based on switching control according to claim 1, characterized in that, The period of the pendulum of the trolley is calculated using the following formula: Where, ω n Let l be the pendulum frequency of the trolley, l be the rope length, and g be the acceleration due to gravity.

4. The anti-sway method for bridge cranes based on switching control according to claim 1, characterized in that, The acceleration trajectory planning of the trolley is based on the embedded slope acceleration trajectory planning, and is calculated using the following formula: When 0≤t≤τ1, When τ1≤t≤T aux1 When -τ1, When T aux1 -τ1≤t≤T aux1 hour, When T aux2 ≤t≤T aux2 When +τ1, When T aux2 +τ1≤t≤T aux3 hour, When T aux3 ≤t≤T aux4 hour, Other situations Where τ1 is an adjustable parameter, and its value range is ω n Let a be the pendulum frequency of the trolley. 1max T is the maximum acceleration value during the translational motion of the trolley. aux1 ,T aux2 ,T aux3 ,T aux4 It is a constant that is related to the period T of the simple pendulum.

5. The anti-sway method for bridge cranes based on switching control according to claim 1, characterized in that, If the trolley does not reach the target position, the variable proportional controller continues to use to return the trolley to the target. When the trolley reaches the target position, the control ends.

6. A bridge crane anti-sway system based on switching control, characterized in that, include: The server includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method of any one of claims 1-5.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it performs the method described in any one of claims 1-5.

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