Cascade PID (Proportion Integration Differentiation) control method for oil cylinder of quay crane

Abstract

The invention provides a cascade PID (Proportion Integration Differentiation) control method for oil cylinders of a quay crane, the quay crane is provided with a plurality of oil cylinders and a lifting appliance, pistons of the plurality of oil cylinders are linked with piston rods to drive the lifting appliance to move, and cascade PID control is performed on each oil cylinder. The cascade PID control method comprises the steps that outer ring control is conducted on the position of a piston based on the actual position of the piston and the expected position of the piston; and performing inner ring control on the speed of the piston based on the expected speed of the piston and the feedback speed of the piston. According to the cascade PID control method for the oil cylinder of the quay crane, the stable tilting motion of the lifting appliance can be realized.

Description

Technical Field

[0001] The invention relates to the field of quay cranes, and in particular to a cascade PID control method for an oil cylinder of a quay crane. Background Art

[0002] In order to facilitate operation and container loading, the quay crane needs to tilt the spreader, tilting forward and backward with the left and right horizontal axes as the center line, tilting left and right with the front and rear longitudinal axes as the center line, and rotating with the vertical axis as the center line.

[0003] The above action is completed by driving the oil cylinder to pull the wire rope and map it to the relative change of the sling height. If the position of the oil cylinder is mismatched during the tilting process, it will cause abnormal changes in the force on the wire rope and cause the sling posture to be messy. Summary of the invention

[0004] In view of the above problems in the prior art, an object of the present invention is to provide a cascade PID control method for the oil cylinder of a quay crane, which can enable the spreader to achieve stable tilting movement.

[0005] In order to solve the above problems, the present invention provides a cascade PID control method for a cylinder of a quay crane, wherein the quay crane has a plurality of cylinders and a spreader, and pistons of the plurality of cylinders are linked with piston rods to drive the spreader to move, wherein the cascade PID control is performed on each cylinder, and the cascade PID control method comprises:

[0006] performing outer loop control on the position of the piston based on the actual position of the piston and the desired position of the piston;

[0007] The speed of the piston is inner-loop controlled based on the desired speed of the piston and the feedback speed of the piston.

[0008] Further, the zero position of the piston is obtained, at which the pistons of all the oil cylinders can make the sling regulated;

[0009] The actual position of the piston is obtained by measuring the relative position of the piston from the zero point by a displacement sensor;

[0010] The expected position is obtained based on the target position reached by the piston after completing the predetermined movement and the current position. The predetermined movement includes tilting movement, and the tilting movement includes front and rear tilting movement, left and right tilting movement and rotational movement. The sling makes the piston located at the zero position before the tilting movement.

[0011] Furthermore, an oil pump is used to supply oil to the plurality of oil cylinders so that the plurality of oil cylinders move synchronously. During the tilting movement,

[0012] The first total volume is obtained by adding the product of the cross-sectional area of ​​each cylinder and the stroke distance of the cylinder, and the first total volume is divided by the flow rate of the oil pump to obtain the first expected time of the piston, and the stroke distance is the difference distance between the expected position of the piston and the zero position;

[0013] Dividing the first expected time into a plurality of first interruption periods;

[0014] The piston is discretely sampled, and the feedback speed of the piston is calculated based on the measured first cycle distance of the movement of the piston within a single first interruption cycle.

[0015] Further, the oil cylinder is a double-acting oil cylinder, which includes a rod chamber and a rodless chamber, and the first total volume is obtained by multiplying the first cross-sectional area of ​​each oil cylinder performing an extension movement by the sum of the stroke distance of the oil cylinder, plus the second cross-sectional area of ​​each oil cylinder performing a retraction movement by the sum of the stroke distance of the oil cylinder.

[0016] The first cross-sectional area is the cross-sectional area of ​​the rodless cavity, and the second cross-sectional area is the cross-sectional area of ​​the rod cavity minus the cross-sectional area of ​​the piston rod.

[0017] Further, the expected speed of the piston is obtained based on the stroke distance of the piston of the cylinder divided by the first expected time.

[0018] Further, after completing one of the first interruption cycles, the expected position and the expected speed of the piston are recalculated, and the outer loop control is performed based on the recalculated expected position and the actual position, and the outer loop control is performed based on the recalculated expected speed and the feedback speed.

[0019] Furthermore, the predetermined movement also includes a return-to-zero movement. When the spreader completes the tilting movement, the piston is controlled to perform the return-to-zero movement. In the return-to-zero movement, the desired position of the piston is the zero point position.

[0020] The product of the cross-sectional area of ​​each oil cylinder and the zeroing distance of the oil cylinder is added to obtain a second total volume, and the second total volume is divided by the flow rate of the oil pump to obtain a second expected time of the piston, wherein the zeroing distance is the difference distance between the zero point position of the piston and the current position of the piston;

[0021] dividing the second expected time into a plurality of second interruption periods;

[0022] discretely sampling the piston, and calculating the feedback speed of the piston based on the measured second period distance of movement of the piston within a single second interruption period;

[0023] The expected speed of the piston is obtained by dividing the zero return distance of the piston of the cylinder by the second expected time.

[0024] Furthermore, the stroke of the piston includes a tilting stroke and a cabin safety stroke.

[0025] When the piston is extended to the maximum extension stroke of the tilting stroke, the piston is controlled to stop moving;

[0026] When the piston retracts to the maximum retraction stroke of the tilting stroke and does not reach the desired position of the piston, the piston is controlled to continue to retract using the cargo hold safety stroke, and when the load of the piston is reduced, the piston is controlled to disengage from the cargo hold safety stroke to the tilting stroke.

[0027] Furthermore, the oil cylinders include four, and the four oil cylinders drive the four corners of the spreader.

[0028] During the tilting movement, when the piston reaches the tilting stroke and the sling has not reached the predetermined tilting angle, the piston performing the retraction movement is controlled to continue to retract to the nacelle safety stroke, so that the sling reaches the predetermined tilting angle, and when the tilting movement ends, the sling promptly leaves the nacelle safety stroke.

[0029] Furthermore, the outer loop control and the inner loop control are formed based on a neural unit self-tuning method.

[0030] Another aspect of the present invention provides a cascade PID control system for an oil cylinder of a quay crane, the cascade PID control system comprising:

[0031] an outer loop controller, the outer loop controller being used to control the position of the piston based on the actual position of the piston and the desired position of the piston;

[0032] An inner loop controller is used to perform inner loop control on the speed of the piston based on the desired speed of the piston and the feedback speed of the piston.

[0033] Due to the above technical solution, the present invention has the following beneficial effects:

[0034] According to the cascade PID control method for the oil cylinder of the quay crane of the present invention, the spreader is driven by multiple oil cylinders to perform tilting movement, and the piston of each oil cylinder is controlled synchronously. The outer loop control is performed based on the actual position of the piston detected and the expected position to be reached by the piston, and the inner loop control is performed based on the actual speed of the piston detected and the expected speed required by the piston. In this way, the piston can reach a precise position according to a stable speed, and the movements of each piston can be coordinated with each other, so that the tilting of the spreader is stable, and the PID control of the oil cylinder is simpler and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 is a structural diagram of a quay crane according to an embodiment of the present invention;

[0037] Figure 2 is a flow chart of a cascade PID control method for an oil cylinder of a quay crane according to an embodiment of the present invention;

[0038] Figure 3 is a schematic diagram of cascade PID control of an oil cylinder for a quay crane according to an embodiment of the present invention;

[0039] Figure 4 Schematic diagram of a cascade PID control system for a cylinder of a quay crane according to an embodiment of the present invention.

[0040] Reference numerals:

[0041] 101. First lifting wheel; 102. Second lifting wheel; 103. Third lifting wheel; 104. Fourth lifting wheel; 201. First oil cylinder; 202. Second oil cylinder; 203. Third oil cylinder; 204. Fourth oil cylinder; 300. Lifting device. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions.

[0044] Next, a cascade PID (proportional-integral-differential) control method for a cylinder of a quay crane according to an embodiment of the present invention is described. The quay crane has a plurality of cylinders and a spreader 300. The pistons of the plurality of cylinders are linked with piston rods to drive the spreader 300 to move, and a cascade PID control is performed on each cylinder. The cascade PID control is a known technology and will not be described in detail here.

[0045] like Figure 1 As shown, four oil cylinders (first oil cylinder 201, second oil cylinder 202, third oil cylinder 203 and fourth oil cylinder 204) drive four suspension wheels (first suspension wheel 101, second suspension wheel 102, third suspension wheel 103 and fourth suspension wheel 104) to move through steel wire ropes, thereby driving the sling 300 to tilt. It should be noted that the above are only optional examples, and the number of oil cylinders and suspension wheels is not specifically limited here.

[0046] The oil cylinder includes a piston and a piston rod connected to the piston, and the piston rod drives the hanging wheel to move, thereby realizing the tilting movement of the hanger 300 connected to the hanging wheel.

[0047] like Figure 2 and Figure 3 As shown, the cascade PID control method for the oil cylinder of the quay crane according to the embodiment of the present invention includes:

[0048] Step S1 : performing outer loop control on the position of the piston based on the actual position of the piston and the expected position of the piston.

[0049] The position of the piston is controlled by an outer ring, so that the piston can be accurately moved to the desired position, thereby facilitating the piston to stably drive the hoisting wheel to the predetermined position through the piston rod, and accurately realizing the tilting of the hoisting device 300.

[0050] Step S2, performing inner loop control on the speed of the piston based on the desired speed of the piston and the feedback speed of the piston.

[0051] The piston speed is controlled by an inner loop, so that the piston speed can be stable and accurate.

[0052] Compared with the unipolar PID control method (controlling only the position of the piston), the speed of the piston of the oil cylinder is unstable, resulting in unstable deflection of the spreader 300 and the spreader 300 failing to reach the predetermined position. Moreover, the PID parameters are not easy to set and adjust.

[0053] Compared with the proportional valve of the pipeline that uses the oil pump to inject oil into the oil cylinder to give a constant signal, as an open-loop control, different proportional valves have different performances, resulting in reduced compatibility. Moreover, during the tilting process, the force change on the wire rope caused by the transfer of the center of gravity of the load of the sling 300 may cause the load of the oil cylinder to change, resulting in a large change in the speed of the piston of the oil cylinder, causing the deflection of the sling 300 to be unstable and the sling 300 to fail to reach the predetermined position.

[0054] The control method of the present application can make the position of the piston of the oil cylinder accurate, the speed of the piston stable, and can make the movements of each piston coordinated with each other, so that the tilting of the sling 300 is stable, and the PID control of the oil cylinder is simpler and more stable.

[0055] The above cascade PID control method for the oil cylinder of the quay crane drives the spreader 300 to perform tilting movement through multiple oil cylinders, and synchronously controls the piston of each oil cylinder, performs outer loop control based on the actual position of the piston detected and the expected position to be reached by the piston, and performs inner loop control based on the actual speed of the piston detected and the expected speed required by the piston. In this way, the piston can reach a precise position at a stable speed, and the movements of each piston can be coordinated with each other, so that the tilting of the spreader 300 is stable, and the PID control of the oil cylinder is simpler and more stable.

[0056] In some embodiments of the present invention, the zero position of the piston is obtained. At the zero position, the pistons of all the oil cylinders can make the spreader 300 regulated. The actual position of the piston is obtained by measuring the relative position of the piston from the zero point through a displacement sensor. The desired position is obtained based on the target position reached by the piston after completing the predetermined movement and the current position. The predetermined movement includes tilting movement, which includes front and rear tilting movement, left and right tilting movement and rotation movement. The spreader 300 makes the piston at the zero position before the tilting movement.

[0057] That is, the zero position of the piston is obtained, that is, each piston is first at the zero position and the speed is zero, so that the spreader 300 is regulated, thereby ensuring the consistency and accuracy of each adjustment.

[0058] The displacement sensor can accurately test the actual position of the piston. The target position that the piston needs to reach during the tilting motion is the expected position relative to the zero position, and the expected position of the piston can be accurately obtained. For example: if the expected position is +200mm, the target position has a positive (extending direction) distance of 200mm relative to the zero position, and if the expected position is -200mm, the target position has a negative (retracting direction) distance of 200mm relative to the zero position.

[0059] Furthermore, oil is supplied to multiple cylinders through an oil pump so that the multiple cylinders move synchronously. In the tilting movement, the product of the cross-sectional area of ​​each cylinder and the stroke distance of the cylinder is added to obtain the first total volume, and the first total volume is divided by the flow rate of the oil pump to obtain the first expected time of the piston. The stroke distance is the difference between the expected position of the piston and the zero position. The first expected time is divided into multiple first interruption cycles. Discrete sampling is performed on the piston, and the feedback speed of the piston is calculated based on the measured first cycle distance of the movement of the piston in a single first interruption cycle.

[0060] like Figure 1 As shown, an oil pump supplies oil to four oil cylinders through pipelines, and a proportional valve is set on each pipeline to control the oil supply of each pipeline to the corresponding cylinder, thereby ensuring the synchronous movement of multiple cylinders. The cross-sectional area of ​​the four oil pumps and the stroke distance of the cylinder can calculate the first total volume of oil required for the movement of the four cylinders, that is, the required first total oil volume, and the first expected time (the shortest time required for the four pistons to complete the movement) is obtained by dividing the first total oil volume by the flow rate of the oil pump.

[0061] The first expected time is divided into multiple first interruption cycles, for example, the first expected time is 10s, the first interruption cycle is 50ms, that is, the first cycle is divided into 50 time periods. Discrete sampling is performed on the piston, and the feedback speed of the piston is calculated based on the measured first cycle distance of the piston in a single first interruption cycle. For example, if the piston moves 1.2mm in one time period, the feedback speed (actual detection speed) of the piston can be accurately calculated to be 2.4mm / s.

[0062] Through the above, the required oil volume can be accurately known to avoid the situation where the required oil volume of all cylinders exceeds the total capacity of the oil pump, causing the piston to slow down under the pressure of the load when extending. In addition, the shortest time of piston movement can be clearly determined. If the actual movement of the piston exceeds the predetermined time of the first cycle time, it can be determined that the tilting movement has a fault.

[0063] Furthermore, the control process may exceed the capacity of the oil pump supplying the cylinder, which may cause the cylinder to slow down under the pressure of the load when extending.

[0064] Further, the oil cylinder is a double-acting oil cylinder, which includes a rod chamber and a rodless chamber, and the sum of the first cross-sectional area of ​​each oil cylinder for extension movement multiplied by the stroke distance of the oil cylinder, plus the sum of the second cross-sectional area of ​​each oil cylinder for retraction movement multiplied by the stroke distance of the oil cylinder, thereby obtaining a first total volume. Among them, the first cross-sectional area is the cross-sectional area of ​​the rodless chamber, and the second cross-sectional area is the cross-sectional area of ​​the rod chamber minus the cross-sectional area of ​​the piston rod.

[0065] For example, in order to achieve the forward tilting movement of the spreader 300, the Figure 1 The second piston and the third piston in the middle retract, that is, the second hanging wheel 102 and the third hanging wheel 103 descend, and the first piston and the fourth piston extend, that is, the first hanging wheel 101 and the fourth hanging wheel 104 rise.

[0066] The cross-sectional areas of the rod chambers of the second oil cylinder 202 (with the second piston) and the third oil cylinder 203 (with the third piston) are respectively S 20 and S 30 The cross-sectional areas of the second piston rod and the third piston rod are S2 and S3, and the cross-sectional areas of the rodless chambers of the first oil cylinder 201 (with the first piston) and the fourth oil cylinder 204 (with the fourth piston) are S 01 and S 04 The extension strokes of the first piston and the fourth piston are D1 and D4 respectively, and the retraction strokes of the second piston and the third piston are D2 and D3 respectively.

[0067] The first total volume (V 总 ) is calculated as follows:

[0068] V 总1 =(S 20 -S2)*D2+(S 30 -S3)*D3+S 01 *D1+S 04 *D4

[0069] If the flow rate of the oil pump is Q, the corresponding first cycle time T1 is calculated as follows:

[0070] T1=V 总1 / Q

[0071] Further, the expected speed of the piston is obtained based on the stroke distance of the piston of the cylinder divided by the first expected time.

[0072] For example, if the stroke distance of the first piston is D1, the stroke distance of the second piston is D2, the stroke distance of the third piston is D3, and the stroke distance of the fourth piston is D4, then the corresponding expected speed V of the first piston is 01 (equal to D1 / T1), the desired speed of the second piston V 02 (equal to D2 / T1), the desired speed V of the third piston 03 (equal to D3 / T1), the desired speed of the second piston V 02 (equal to D4 / T1). That is, the outer loop control inputs the desired speed to the inner loop control, and establishes the relationship between the inner loop control and the outer loop control.

[0073] Further, after completing a first interruption cycle, the desired position and desired speed of the piston are recalculated, and outer loop control is performed based on the recalculated desired position and actual position, and outer loop control is performed based on the recalculated desired speed and feedback speed.

[0074] For example, the expected position is +20mm, the piston completes the first interruption cycle, the actual position is +0.8mm, the expected position is +1mm, then the expected position of the next second interruption cycle is +19.2mm. Accordingly, the expected speed calculated based on the expected position is also adjusted accordingly.

[0075] In this way, the position of the piston can be corrected in real time, the difference between the pistons can be reduced, and the consistency of the pistons can be guaranteed as much as possible.

[0076] This enables the position and speed errors of the piston to be corrected in real time during the movement of the piston. To ensure the displacement synchronization during the cylinder movement, the system calculates the expected position of the piston in each first interruption cycle, which is used as the synchronous target position for the piston to stop when the tilt control suddenly stops. In this way, the system continuously calculates the remaining expected stroke and the expected speed of the piston, and continuously refreshes.

[0077] In some embodiments of the present invention, the predetermined movement also includes a zeroing movement. When the sling 300 completes the tilting movement, the piston is controlled to perform a zeroing movement. In the zeroing movement, the product of the cross-sectional area of ​​each cylinder and the zeroing distance of the cylinder is added to obtain a second total volume, and the second total volume is divided by the flow rate of the oil pump to obtain the second expected time of the piston. The zeroing distance is the difference between the zero position of the piston and the current position of the piston. The second expected time is divided into a plurality of second interruption cycles. The piston is discretely sampled, and the feedback speed of the piston is calculated based on the measured second cycle distance of the movement of the piston in a single second interruption cycle. The zeroing distance of the piston of the cylinder is divided by the second expected time to obtain the expected speed of the piston.

[0078] The zeroing movement is the reverse process of the aforementioned tilting movement, so as to ensure the consistency of the subsequent tilting movement. The target position (expected position) is the zero position, and the current position is the current position of the piston.

[0079] For example, in order to achieve the zero return movement after the forward tilting movement of the spreader 300, the Figure 1The second piston and the third piston extend out, that is, the second hanging wheel 102 and the third hanging wheel 103 rise, and the first piston and the fourth piston retract, that is, the first hanging wheel 101 and the fourth hanging wheel 104 fall.

[0080] The cross-sectional areas of the rod chambers of the first oil cylinder 201 (with the first piston) and the fourth oil cylinder 204 (with the fourth piston) are respectively S 10 and S 40 The cross-sectional areas of the first piston rod and the fourth piston rod are S1 and S4, and the cross-sectional areas of the rodless chambers of the second oil cylinder 202 (with the second piston) and the third oil cylinder 203 (with the third piston) are S 02 and S 03 The retraction stroke of the first piston is D 01 , the retraction stroke of the fourth piston is D 04 , the extension stroke of the second piston is D 02 , the extension stroke of the third piston is D 03 .

[0081] The second total volume (V 总 ) is calculated as follows:

[0082] V 总2 =(S 10 -S1)*D 01 +(S 40 -S4)*D 04 +S 02 *D 02 +S 03 *D 03

[0083] If the flow rate of the oil pump is Q, the corresponding second cycle time T2 is calculated as follows:

[0084] T2=V 总2 / Q

[0085] The rest refers to the tilting motion.

[0086] As a result, the piston of each cylinder can be accurately returned to zero at a stable speed.

[0087] In some embodiments of the present invention, the stroke of the piston includes a tilting stroke and a pod safety stroke. When the piston extends to the maximum extension stroke of the tilting stroke, the piston is controlled to stop moving. When the piston retracts to the maximum retraction stroke of the tilting stroke and does not reach the desired position of the piston, the piston is controlled to continue to retract using the pod safety stroke, and when the load of the piston is reduced, the piston is controlled to leave the pod safety stroke to the tilting stroke.

[0088] For example, the piston stroke is 1000mm, the pod protection stroke is 500mm, the tilting stroke is 500mm (maximum extension stroke +250mm, maximum retraction stroke -250mm), and the zero position of the piston is 750mm.

[0089] The lifting device 300 lifts the container and performs a tilting motion to place the container on the heavy truck. The piston of some oil cylinders retracts, and after retracting to -250mm, it still does not reach the desired position, and can continue to retract to a position of -300mm to reach the desired position. When the load on the piston is reduced, the tilting motion is completed, and the piston is controlled to extend so that the piston is within the range of -250mm to 0mm.

[0090] By setting the cabin safety stroke, it is possible to avoid the situation where the hoist 300 collides with the ship hatch or other obstacles during the lifting process or gets stuck, thereby preventing safety accidents. The extension and retraction strokes of the piston are limited to avoid safety accidents and increase safety. On this basis, the retraction movement of the piston uses the cabin safety stroke to achieve special tilting movement, and the cabin safety stroke is promptly separated to ensure safety.

[0091] Furthermore, the oil cylinder includes four oil cylinders, and the four oil cylinders drive the four corners of the spreader 300. During the tilting movement, when the piston reaches the tilting stroke and the spreader 300 has not reached the predetermined tilting angle, the piston that is doing the retraction movement is controlled to continue to retract to the cabin safety stroke, so that the spreader 300 reaches the predetermined tilting angle, and when the tilting movement ends, it leaves the cabin safety stroke in time.

[0092] For example, four oil cylinders drive the spreader 300 to tilt forward and backward, two pistons of which retract and the other two pistons extend. When the tilt angle of the spreader 300 does not reach the predetermined tilt angle, the pistons are already at the maximum stroke of the tilt stroke, and the two pistons in the retracting motion continue to retract, so that the pistons are located in the cabin safety stroke, so that the spreader 300 reaches the predetermined tilt angle, and the two retracting pistons extend in time, thereby leaving the cabin safety stroke. In this way, the spreader 300 can achieve a large-angle tilting motion with high safety.

[0093] In some embodiments of the present invention, the outer loop control and the inner loop control are formed based on a neural unit self-tuning method.

[0094] For example, the outer loop control and inner loop control are formed by the PID parameter self-tuning control method of the BP neural network or the single neuron adaptive PID control method, thereby improving the stability and accuracy of the control.

[0095] The following describes a cascade PID control system 1000 for a cylinder of a quay crane according to an embodiment of the present invention. The cascade PID control system 1000 includes an outer loop controller 1001 and an inner loop controller 1002 .

[0096] like Figure 4 As shown, the outer loop controller 1001 is used to control the position of the piston based on the actual position of the piston and the desired position of the piston. The inner loop controller 1002 is used to perform inner loop control on the speed of the piston based on the desired speed of the piston and the feedback speed of the piston.

[0097] The outer loop controller 1001 and the inner loop controller 1002 can enable the piston to reach a precise position at a stable speed, and the movements of the various pistons can be coordinated with each other, so that the tilting of the sling 300 is stable.

[0098] Since the cascade PID control method for the oil cylinder of the quay crane according to the embodiment of the present invention has the above-mentioned technical effects, the cascade PID control system 1000 for the oil cylinder of the quay crane according to the embodiment of the present invention also has corresponding technical effects.

[0099] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A cascade PID control method for a cylinder of a quay crane, wherein the quay crane has a plurality of cylinders and a spreader, and the pistons of the plurality of cylinders are linked with piston rods to drive the spreader to move, characterized in that: The cascade PID control is performed on each of the oil cylinders, and the cascade PID control method includes: performing outer loop control on the position of the piston based on the actual position of the piston and the desired position of the piston; The speed of the piston is inner-loop controlled based on the desired speed of the piston and the feedback speed of the piston.

2. The cascade PID control method for the oil cylinder of the quay crane according to claim 1, characterized in that: Obtaining the zero position of the piston, at which the pistons of all the oil cylinders can make the sling regulated; The actual position of the piston is obtained by measuring the relative position of the piston from the zero point by a displacement sensor; The expected position is obtained based on the target position reached by the piston after completing a predetermined movement and the current position, the predetermined movement includes a tilting movement, and the tilting movement includes a front-back tilting movement, a left-right tilting movement, and a rotational movement. The sling makes the piston located at the zero position before the tilting movement.

3. The cascade PID control method for the oil cylinder of the quay crane according to claim 2, characterized in that: An oil pump is used to supply oil to the multiple oil cylinders so that the multiple oil cylinders move synchronously. During the tilting movement, The first total volume is obtained by adding the product of the cross-sectional area of ​​each cylinder and the stroke distance of the cylinder, and the first total volume is divided by the flow rate of the oil pump to obtain the first expected time of the piston, and the stroke distance is the difference distance between the expected position of the piston and the zero position; Dividing the first expected time into a plurality of first interruption periods; The piston is discretely sampled, and the feedback speed of the piston is calculated based on the measured first cycle distance of the movement of the piston within a single first interruption cycle.

4. The cascade PID control method for the oil cylinder of the quay crane according to claim 3, characterized in that: The oil cylinder is a double-acting oil cylinder, which includes a rod chamber and a rodless chamber. The first total volume is obtained by multiplying the first cross-sectional area of ​​each oil cylinder for extension movement by the sum of the stroke distance of the oil cylinder, plus the second cross-sectional area of ​​each oil cylinder for retraction movement by the sum of the stroke distance of the oil cylinder. The first cross-sectional area is the cross-sectional area of ​​the rodless cavity, and the second cross-sectional area is the cross-sectional area of ​​the rod cavity minus the cross-sectional area of ​​the piston rod.

5. The cascade PID control method for the oil cylinder of the quay crane according to claim 4, characterized in that: The expected speed of the piston is obtained based on the stroke distance of the piston of the cylinder divided by the first expected time.

6. The cascade PID control method for the oil cylinder of the quay crane according to claim 5, characterized in that: After completing one of the first interruption cycles, the desired position and the desired speed of the piston are recalculated, and the outer loop control is performed based on the recalculated desired position and the actual position, and the outer loop control is performed based on the recalculated desired speed and the feedback speed.

7. The cascade PID control method for the oil cylinder of the quay crane according to claim 6, characterized in that: The predetermined movement also includes a return-to-zero movement. When the sling completes the tilting movement, the piston is controlled to perform the return-to-zero movement. During the return-to-zero movement, the desired position of the piston is the zero point position. The product of the cross-sectional area of ​​each oil cylinder and the zeroing distance of the oil cylinder is added to obtain a second total volume, and the second total volume is divided by the flow rate of the oil pump to obtain a second expected time of the piston, wherein the zeroing distance is the difference distance between the zero point position of the piston and the current position of the piston; dividing the second expected time into a plurality of second interruption periods; discretely sampling the piston, and calculating the feedback speed of the piston based on the measured second period distance of movement of the piston within a single second interruption period; The expected speed of the piston is obtained by dividing the zero return distance of the piston of the cylinder by the second expected time.

8. The cascade PID control method for the oil cylinder of a quay crane according to claim 2, characterized in that: The stroke of the piston includes a tilting stroke and a cabin safety stroke. When the piston is extended to the maximum extension stroke of the tilting stroke, the piston is controlled to stop moving; When the piston retracts to the maximum retraction stroke of the tilting stroke and does not reach the desired position of the piston, the piston is controlled to continue to retract using the cargo hold safety stroke, and when the load of the piston is reduced, the piston is controlled to disengage from the cargo hold safety stroke to the tilting stroke.

9. The cascade PID control method for the oil cylinder of the quay crane according to claim 8, characterized in that: The oil cylinders include four, and the four oil cylinders drive the four corners of the spreader. During the tilting movement, when the piston reaches the tilting stroke and the sling has not reached the predetermined tilting angle, the piston performing the retraction movement is controlled to continue to retract to the nacelle safety stroke, so that the sling reaches the predetermined tilting angle, and when the tilting movement ends, the sling promptly leaves the nacelle safety stroke.

10. The cascade PID control method for the oil cylinder of a quay crane according to claim 1, characterized in that: The outer loop control and the inner loop control are formed based on a neural unit self-tuning method.

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