Cascade PID control method for oil cylinders of quay cranes

Abstract

The present invention provides a cascade PID control method for cylinders used in quay cranes. The quay crane has multiple cylinders and a spreader. The pistons of the multiple cylinders are linked to piston rods to drive the spreader. Each cylinder is subjected to cascade PID control. The cascade PID control method includes: outer-loop control of the piston position based on its actual position and its desired position; and inner-loop control of the piston speed based on its desired speed and its feedback speed. This cascade PID control method for cylinders in a quay crane can achieve stable tilting motion of the spreader.

Description

Technical Field

[0001] The present 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 handling, the quay crane needs to tilt the spreader, tilting it forward and backward with the left and right horizontal axes as the center line, tilting it left and right with the front and back longitudinal axes as the center line, and rotating it with the vertical axis as the center line.

[0003] The above action is achieved by driving the oil cylinder to pull the wire rope and mapping it to the relative change in the height of the spreader. 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 spreader posture to become messy. Summary of the Invention

[0004] In view of the above problems in the prior art, the 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 multiple cylinders and a spreader, and the pistons of the multiple cylinders are linked with piston rods to drive the spreader to move. The method is characterized in that the cascade PID control is performed on each cylinder, and the method includes:

[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] Furthermore, the zero position of the piston is obtained, at which the pistons of all the oil cylinders can make the spreader straight;

[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 back 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] A 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 a first expected time of the piston, where the stroke distance is the difference 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 piston in a single first interruption cycle.

[0015] Furthermore, 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 oil cylinder divided by the first expected time.

[0018] Furthermore, after completing one of the first interruption cycles, the desired position and desired speed of the piston are recalculated, and the outer loop control is performed based on the recalculated desired position and actual position, and the outer loop control is performed based on the recalculated desired speed and 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. During the return-to-zero movement, the desired position of the piston is the zero position.

[0020] A second total volume is obtained by adding the product of the cross-sectional area of ​​each cylinder and the zeroing distance of the cylinder, and the second total volume is divided by the flow rate of the oil pump to obtain a second expected time of the piston, where the zeroing distance is the difference between the zero 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] performing discrete sampling on 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 extends to the maximum extension stroke of the tilting stroke, controlling the piston 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 nacelle safety stroke, and when the load of the piston is reduced, the piston is controlled to disengage from the nacelle 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 spreader 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 spreader reaches the predetermined tilting angle, and when the tilting movement ends, it 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 configured 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 present invention, the cascaded PID control method for hydraulic cylinders used in quay cranes utilizes multiple hydraulic cylinders to drive the spreader's tilting motion. The pistons in each cylinder are synchronously controlled, with outer-loop control based on the detected piston position and the desired position, and inner-loop control based on the detected piston speed and the desired speed. This method enables the pistons to reach precise positions at a stable speed, coordinates the movements of the individual pistons, stabilizes the spreader's tilting motion, and makes the PID control of the hydraulic cylinders simpler and more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without inventive effort.

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

[0038] Figure 3 1 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 FIG. 1 is a schematic diagram of a cascade PID control system for an oil 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 solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of 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 making creative efforts shall fall within the scope of protection of the present invention.

[0043] It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and the accompanying drawings are used to distinguish similar items and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, such that the embodiments of the present invention described herein can be implemented in sequences other than those illustrated or described herein. Furthermore, the terms "including," "having," and any variations thereof are intended to cover non-exclusive inclusions.

[0044] The following describes a cascade PID (Proportional-Integral-Derivative) control method for a quay crane's hydraulic cylinders, according to an embodiment of the present invention. The quay crane has multiple hydraulic cylinders and a spreader 300. The pistons of the multiple cylinders are linked to piston rods to drive the spreader 300. Cascade PID control is performed on each cylinder. Cascade PID control is a well-known technique 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 hanging wheels (first hanging wheel 101, second hanging wheel 102, third hanging wheel 103, and fourth hanging wheel 104) via steel wire ropes, thereby driving the spreader 300 to tilt. It should be noted that the above is only an optional example, and the number of oil cylinders and hanging wheels is not specifically limited here.

[0046] The oil cylinder includes a piston and a piston rod connected to the piston. The piston rod drives the hanging wheel to move, thereby realizing the tilting movement of the sling 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 desired 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 hoist 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 to a unipolar PID control method (which only controls the position of the piston), the speed of the cylinder piston is unstable, resulting in unstable deflection of the spreader 300 and the spreader 300 failing to reach the predetermined position. Furthermore, PID parameters are difficult to tune and adjust.

[0053] Compared to using a proportional valve in the pipeline that injects oil into the cylinder using an oil pump to provide a constant signal, open-loop control results in different proportional valves with varying performance, reducing compatibility. Furthermore, during the tilting process, the shifting center of gravity of the spreader 300 causes changes in the force on the wire rope, which in turn causes changes in the cylinder load. This can cause significant changes in the speed of the cylinder piston, resulting in unstable deflection of the spreader 300 and the spreader 300 failing to reach the desired 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 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-described cascade PID control method for hydraulic cylinders in a quay crane uses multiple cylinders to drive the spreader 300 for tilting motion. Each cylinder's piston is synchronously controlled, with outer-loop control based on the detected piston position and the desired position, and inner-loop control based on the detected piston speed and the desired speed. This method enables the pistons to reach precise positions at a stable speed, coordinates the movements of the various pistons, stabilizes the tilting of the spreader 300, and makes PID control of the cylinders simpler and more stable.

[0056] In some embodiments of the present invention, the zero position of the piston is determined. At the zero position, the pistons of all cylinders can align the spreader 300. A displacement sensor measures the relative position of the piston from the zero point to obtain the actual position of the piston. A desired position is determined based on the target position reached by the piston after completing a predetermined motion and the current position. The predetermined motion includes tilting motion, which includes forward and backward tilting motion, left and right tilting motion, and rotational motion. The spreader 300 is positioned at the zero position before the tilting motion is performed.

[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 accurately measures the piston's actual position. The desired target position relative to the zero position during the tilting motion is calculated, accurately determining the desired piston position. For example, a desired position of +200mm would have a positive distance (extending direction) of 200mm relative to the zero position. A desired position of -200mm would have a negative distance (retracting direction) of 200mm relative to the zero position.

[0059] Furthermore, a single oil pump supplies oil to multiple cylinders, enabling synchronous operation. During tilting motion, the product of the cross-sectional area of ​​each cylinder and the stroke distance of that cylinder is added together to obtain a first total volume. This first total volume is divided by the oil pump flow rate to obtain the first desired piston time, where the stroke distance is the difference between the desired piston position and the zero position. The first desired time is divided into multiple first interruption periods. The piston is discretely sampled, and the piston feedback speed is calculated based on the measured first cycle distance of the piston movement within a single first interruption period.

[0060] like Figure 1 As shown, a single oil pump supplies oil to four cylinders via pipelines. A proportional valve is installed on each pipeline to control the oil supply to the corresponding cylinder, thereby ensuring synchronized movement of the multiple cylinders. The cross-sectional areas of the four oil pumps and the stroke distances of the cylinders can be used to calculate the first total volume of oil required for the movement of the four cylinders, i.e., the required first total oil volume. Dividing the first total oil volume by the oil pump flow rate yields the first expected time (the shortest time required for all four pistons to complete movement).

[0061] The first desired time is divided into multiple first interruption periods. For example, if the first desired time is 10 seconds and the first interruption period is 50 milliseconds, the first period is divided into 50 time periods. The piston is discretely sampled, and the piston feedback speed is calculated based on the measured first-period distance of the piston movement within a single first interruption period. For example, if the piston moves 1.2 mm in one time period, the piston feedback speed (actual detection speed) can be accurately calculated to be 2.4 mm / s.

[0062] This allows accurate determination of the required oil volume, preventing the situation where the required oil volume for all cylinders exceeds the total pump capacity, causing the piston to slow down under load pressure during extension. Furthermore, the minimum piston movement time can be determined, and if the actual piston movement exceeds the first cycle time, a tilting motion failure can be determined.

[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] Furthermore, the cylinder is a double-acting cylinder comprising a rod chamber and a rodless chamber. The first total volume is obtained by multiplying the first cross-sectional area of ​​each extending cylinder by the stroke of the cylinder, plus the second cross-sectional area of ​​each retracting cylinder by the stroke of the cylinder. 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 ascend.

[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] Furthermore, the desired speed of the piston is obtained based on a stroke distance of the piston of the oil cylinder divided by the first desired 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, establishing the relationship between the inner and outer loop controls.

[0073] Furthermore, 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, if the desired position is +20mm, and the piston completes the first interruption cycle, the actual position is +0.8mm, and the desired position is +1mm, then the desired position for the next second interruption cycle is +19.2mm. Accordingly, the desired speed calculated based on the desired position is also adjusted accordingly.

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

[0076] This allows for real-time correction of position and velocity errors during piston movement. To ensure displacement synchronization during cylinder operation, the system calculates the desired piston position during each first interruption cycle, using this as the target position for synchronization when tilt control suddenly stops. This system continuously calculates the remaining desired travel and the desired piston velocity, continuously updating the information.

[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. During 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 multiple second interruption periods. The piston is discretely sampled, and the feedback speed of the piston is calculated based on the measured second cycle distance of the piston's movement within a single second interruption period. 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 motion is the reverse process of the aforementioned tilting motion, which ensures the consistency of the subsequent tilting motion. 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 realize the zero return movement after the forward tilting movement of the spreader 300, the Figure 1The second piston and the third piston extend, 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 piston travel includes a tilting travel and a nacelle safety travel. When the piston extends to the maximum extension of the tilting travel, the piston is controlled to stop moving. When the piston retracts to the maximum retraction of the tilting travel but does not reach the desired piston position, the piston is controlled to continue retracting using the nacelle safety travel. When the piston load decreases, the piston is controlled to move out of the nacelle safety travel and back to the tilting travel.

[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 point position of the piston is 750mm.

[0089] Spreader 300 lifts the container and tilts it, placing it on the heavy truck. Some of the cylinder pistons retract. If the desired position is not reached after retraction to -250mm, they can be retracted further to -300mm to reach the desired position. When the piston load decreases, the tilting movement is complete, and the piston is controlled to extend, positioning it within the range of -250mm to 0mm.

[0090] By setting a safe travel range, the hoist 300 can avoid collisions or snags with ship hatches or other obstacles during the lifting process, potentially causing safety accidents. By limiting the piston's extension and retraction travel, this prevents accidents and improves safety. Furthermore, by utilizing the safe travel range for the piston's retraction, special tilting motions can be achieved, and safety can be ensured by promptly exiting the safe travel range.

[0091] Furthermore, there are four hydraulic cylinders, each of which drives the four corners of the spreader 300. During the tilting motion, when the piston reaches the tilting stroke and the spreader 300 has not yet reached the predetermined tilting angle, the retracting piston is controlled to continue retracting to the nacelle safety stroke, so that the spreader 300 reaches the predetermined tilting angle. When the tilting motion ends, the spreader 300 promptly leaves the nacelle safety stroke.

[0092] For example, four cylinders drive the spreader 300 to tilt forward and backward, with two pistons retracting and the other two extending. If the spreader 300's tilt angle has not yet reached the predetermined tilt angle, and the pistons are already at their maximum tilting travel, the two retracting pistons continue to retract, bringing them within the hanger's safe travel range. This allows the spreader 300 to reach the predetermined tilt angle, and the two retracting pistons to extend promptly, thus leaving the hanger's safe travel range. This enables the spreader 300 to tilt at a large angle with increased 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] Next, a cascade PID control system 1000 for an oil cylinder of a quay crane according to an embodiment of the present invention is described. 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 can coordinate the movements of the various pistons to stabilize the tilting of the spreader 300 .

[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 replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection 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, wherein the pistons of the plurality of cylinders are linked to 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; 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; Obtaining the zero position of the piston, at which the pistons of all the oil cylinders can keep the spreader straight; 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 desired position is obtained based on a target position reached by the piston after completing a predetermined movement and a current position, wherein the predetermined movement includes a tilting movement, and the tilting movement includes a forward and backward tilting movement, a left and right tilting movement, and a rotational movement, and the spreader causes the piston to be located at the zero position before the tilting movement; An oil pump is used to supply oil to the multiple cylinders so that the multiple cylinders move synchronously. During the tilting movement, A 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 a first expected time of the piston, where the stroke distance is the difference between the expected position of the piston and the zero position; dividing the first expected time into a plurality of first interruption 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.

2. The cascade PID control method for the oil cylinder of a quay crane according to claim 1, 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 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. 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.

3. The cascade PID control method for the oil cylinder of a quay crane according to claim 2, characterized in that: The desired speed of the piston is obtained based on the stroke distance of the piston of the cylinder divided by the first desired time.

4. The cascade PID control method for the oil cylinder of a quay crane according to claim 3, characterized in that: After completing one first interruption cycle, the desired position and 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.

5. The cascade PID control method for the oil cylinder of a quay crane according to claim 4, characterized in that: 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. During the return-to-zero movement, the desired position of the piston is the zero position. A second total volume is obtained by adding the product of the cross-sectional area of ​​each cylinder and the zeroing distance of the cylinder, and the second total volume is divided by the flow rate of the oil pump to obtain a second expected time of the piston, where the zeroing distance is the difference between the zero position of the piston and the current position of the piston; dividing the second expected time into a plurality of second interruption periods; performing discrete sampling on 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.

6. The cascade PID control method for the oil cylinder of a quay crane according to claim 1, characterized in that: The piston stroke includes a tilting stroke and a cabin safety stroke. When the piston extends to the maximum extension stroke of the tilting stroke, controlling the piston 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 nacelle safety stroke, and when the load of the piston is reduced, the piston is controlled to disengage from the nacelle safety stroke to the tilting stroke.

7. The cascade PID control method for the oil cylinder of a quay crane according to claim 6, 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 spreader 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 spreader reaches the predetermined tilting angle, and when the tilting movement ends, it promptly leaves the nacelle safety stroke.

8. 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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