PLC-based water conservancy cofferdam gate control system

Abstract

The application relates to the technical field of water conservancy control, and discloses a water conservancy project cofferdam gate control system based on PLC, which comprises a hydraulic drive and detection assembly and a controller. The controller is configured with a discrete state observation module, a disturbance feature identification module, a virtual shaft parameter scheduling module and a control law synthesis module. The discrete state observation module reconstructs the system state and estimates the total disturbance; the disturbance feature identification module determines normal, jamming or turbulent working conditions according to the disturbance features; the virtual shaft parameter scheduling module adjusts the virtual stiffness and damping coefficient in real time according to the working conditions, or executes an asymmetric auxiliary escape strategy; and the control law synthesis module generates a control voltage in combination with state feedback and feedforward compensation. Through multi-modal parameter scheduling, the application effectively overcomes the water flow impact and nonlinear friction disturbance, realizes decoupling under the turbulent working condition and flexible protection and auxiliary escape under the jamming working condition, and improves the synchronization accuracy and safety of the gate control.

Description

Technical Field

[0001] This invention relates to the field of water conservancy control technology, specifically to a PLC-based control system for cofferdam gates in water conservancy projects. Background Technology

[0002] In large-scale water conservancy projects, cofferdam gates typically employ a dual-hydraulic-cylinder driven opening and closing method, meaning a hydraulic drive unit is installed on each of the left and right sides of the gate. Due to the large span and limited structural rigidity of the gate, it is crucial to ensure that the displacement height of the two hydraulic cylinders is synchronized during the lifting and lowering process. If the two hydraulic cylinders are out of sync, it can lead to gate jamming, or even cause distortion and deformation of the gate's metal structure, and may even damage the guide rails and sealing components.

[0003] Current cofferdam gate control systems mostly employ PLC-based electro-hydraulic proportional control technology. Common synchronization strategies include master-slave control, cross-coupling control, or equivalent control. Control algorithms are typically based on the PID (proportional-integral-derivative) principle, using fixed control parameters to eliminate position errors. However, the physical environment faced by cofferdam gates in actual operation is quite complex. Hydraulic systems inherently possess nonlinear characteristics; for example, the dynamic and static friction forces experienced by hydraulic cylinders change significantly at low speeds, easily causing a "creeping" phenomenon that affects low-speed tracking accuracy.

[0004] More importantly, most existing synchronous control strategies assume that the system is in an ideal or quasi-static environment, lacking adaptability to complex external conditions. In actual operation, gates are often subjected to irregular water flow impacts. When encountering strong turbulence, if the synchronous coupling strength of the control system is too high (i.e., pursuing absolute rigid synchronization), the instantaneous water flow impact on one side of the hydraulic cylinder will be rapidly transmitted to the other side through the control algorithm, causing the system to oscillate back and forth between the two sides, affecting operational stability.

[0005] Furthermore, rivers often contain floating debris such as branches and silt. If unilateral mechanical obstruction occurs (e.g., a foreign object gets stuck in the guide rail), traditional synchronization control logic often cannot distinguish between external resistance interference and mechanical failure, and will still attempt to increase output force to maintain synchronization. In this situation, the hydraulic cylinder on the unobstructed side will continue to forcefully push the gate, while the obstructed side cannot move. This results in enormous shearing forces acting on the gate body, easily causing permanent damage to the mechanical structure. Existing technologies struggle to balance maintaining high-precision synchronization with achieving flexible protection, and lack a classification and handling mechanism for turbulent impacts and mechanical obstruction. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a PLC-based control system for cofferdam gates in water conservancy projects. This system solves the problem that the hydraulic cylinder on the unobstructed side will continue to forcefully push the gate while the obstructed side cannot move, which will result in huge shearing forces acting on the gate body and easily cause permanent damage to the mechanical structure.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a PLC-based control system for a cofferdam gate in a hydraulic engineering project, comprising a hydraulic drive and detection component and a controller. The hydraulic drive and detection component includes a left hydraulic cylinder and a right hydraulic cylinder respectively installed on both sides of the gate, a left electro-hydraulic proportional valve and a right electro-hydraulic proportional valve respectively controlling the left and right hydraulic cylinders, and a left displacement sensor and a right displacement sensor respectively detecting the displacement of the left and right hydraulic cylinders. The controller is electrically connected to the left and right electro-hydraulic proportional valves, the left displacement sensor, and the right displacement sensor. The controller internally includes a logic operation unit, which performs functions including a discrete state observation module, a disturbance feature identification module, a virtual axis parameter scheduling module, and a control law synthesis module.

[0008] Preferably, the discrete state observation module is used to construct an extended state model of the system, observing the internal state of the system without velocity and disturbance sensors. This module receives the target position trajectory and detection values ​​from the displacement sensors on both sides, for the first... side( For a hydraulic cylinder (representing the left or right side), iterative calculations are performed using the following discrete state equations to output a position estimate. Speed ​​estimates and total disturbance estimate

[0009] ;

[0010] in, This is the displacement detection value at the current moment. The control voltage at the previous moment. The sampling period is This is the system's nominal control gain. Correct the observer gain. The total disturbance estimate. It characterizes the total disturbance of the system, including friction, load changes, and water flow impact.

[0011] Preferably, the disturbance feature identification module is used to determine the physical operating conditions of the system. This module is configured with a sliding data window to collect the total disturbance estimate within a set time period and calculate the disturbance fluctuation index. and motion direction factor Disturbance volatility indicator The standard deviation or coefficient of variation of the data within the sliding window is used to characterize the dispersion of the disturbance amplitude. Motion direction factor. The determination is based on whether the direction of the total disturbance estimate is opposite to the direction of the velocity estimate. This module determines the operating condition based on the following logic: when the disturbance fluctuation index... When the turbulence threshold is exceeded, it is determined to be a turbulence impact condition; when the disturbance fluctuation index does not exceed the turbulence threshold, and the motion direction factor indicates that the disturbance is in the direction of resistance, and the amplitude of the total disturbance estimate exceeds the preset steady-state threshold, it is determined to be a single-sided jamming condition; otherwise, it is determined to be a normal operating condition.

[0012] Preferably, the virtual shaft parameter scheduling module is used to establish a virtual synchronous coupling relationship between the two hydraulic cylinders and dynamically adjust the control parameters according to the determined working condition. Under normal operating conditions, this module will adjust the virtual stiffness coefficient. and virtual damping coefficient Configured with preset high stiffness and high damping values, this module maintains the rigid synchronous movement of the hydraulic cylinders on both sides. Under turbulent impact conditions, this module will virtualize the stiffness coefficient. and virtual damping coefficient The system is configured with preset low values ​​for high stiffness and high damping, reducing the coupling strength between the two hydraulic cylinders and suppressing the transmission of water flow impact from one side to the other. In unilateral jamming conditions, the module executes an asymmetric parameter scheduling strategy: for the side experiencing jamming, the virtual stiffness coefficient remains constant, and a non-zero high-frequency auxiliary excitation signal is generated. For the normal side where no jamming occurs, the virtual stiffness coefficient is reduced to a preset low stiffness threshold, and no auxiliary excitation signal is generated.

[0013] Preferably, the control law synthesis module is used to calculate the final control voltage output to the electro-hydraulic proportional valve. For the first... Side hydraulic cylinder, control voltage The calculation formula is:

[0014] ;

[0015] in:

[0016] To eliminate the linear feedback control input for trajectory tracking error, a proportional-derivative (PD) strategy is used for calculation: ;

[0017] This is a virtual coupling correction term, based on the virtual stiffness coefficient. Virtual damping coefficient The difference in position estimation and the difference in speed estimation between the two hydraulic cylinders are calculated. This is the total disturbance estimate used for feedforward compensation; As an auxiliary excitation signal; sat This is an amplitude limiting function used to limit the output to the maximum allowable control voltage. and minimum allowable control voltage between.

[0018] This invention provides a PLC-based control system for cofferdam gates in hydraulic engineering. It offers the following advantages:

[0019] 1. This invention constructs an extended state model through a discrete state observation module, enabling real-time acquisition of the system's velocity state and total disturbance state even without the configuration of velocity and disturbance sensors. The observed total disturbance is introduced into the control law synthesis module for feedforward compensation, directly canceling external interference at the voltage output terminal. This improves the tracking accuracy of the hydraulic cylinder for the target position trajectory and reduces the impact of nonlinear friction and water flow force on control performance.

[0020] 2. This invention combines disturbance feature identification with a virtual axis parameter scheduling mechanism, enabling adjustment of the coupling relationship between the hydraulic cylinders on both sides according to the working conditions. When the system is subjected to turbulent impact, the virtual stiffness coefficient and virtual damping coefficient are automatically reduced to weaken the control coupling strength between the actuators on both sides, preventing random impact loads on one side from being transmitted to the other side through the synchronization algorithm, thus avoiding unnecessary oscillations in the system.

[0021] 3. This invention employs an asymmetric control strategy for unilateral jamming conditions, improving system safety and fault tolerance. After determining unilateral jamming, the system reduces the virtual stiffness of the normal side to decrease mechanical stress on the gate body and prevent structural distortion; simultaneously, a high-frequency auxiliary excitation signal is superimposed on the jammed side to reduce static friction resistance using the flutter effect, assisting the hydraulic cylinder in overcoming the jamming state. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the hardware architecture of the dual-cylinder hydraulic synchronous control system of the present invention;

[0023] Figure 2 This is a block diagram of the overall logic structure of the control system of the present invention;

[0024] Figure 3 This is a flowchart illustrating the logic determination of the disturbance feature identification module of the present invention.

[0025] Among them, 100 is a programmable logic controller; 110 is a discrete state observation module; 120 is a disturbance feature identification module; 130 is a virtual axis parameter scheduling module; 140 is a control law synthesis module; 200 is a left drive assembly; 201 is a left hydraulic cylinder; 202 is a left electro-hydraulic proportional valve; 203 is a left displacement sensor; 300 is a right drive assembly; 301 is a right hydraulic cylinder; 302 is a right electro-hydraulic proportional valve; 303 is a right displacement sensor. Detailed Implementation

[0026] The technical solutions in 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, and 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.

[0027] Example:

[0028] Please see the appendix Figure 1 - Appendix Figure 3 This invention provides a PLC-based control system for cofferdam gates in water conservancy projects, including a programmable logic controller 100, a left-side drive component 200, and a right-side drive component 300. The programmable logic controller 100 serves as the core control unit, establishing electrical connections and signal communication with the left-side drive component 200 and the right-side drive component 300, respectively.

[0029] The left-side drive assembly 200 is configured on one side of the gate and includes a left hydraulic cylinder 201, a left electro-hydraulic proportional valve 202, and a left displacement sensor 203. The piston rod end of the left hydraulic cylinder 201 is mechanically connected to the left-side lifting point of the gate to provide the left-side lifting drive force. The left electro-hydraulic proportional valve 202 is located in the hydraulic oil supply circuit of the left hydraulic cylinder 201, and its signal input terminal is connected to the analog output port of the programmable logic controller 100 to receive control voltage signals and adjust the hydraulic oil flow rate input to the left hydraulic cylinder 201. The left displacement sensor 203 is installed on the left hydraulic cylinder 201 or the left-side guide rail of the gate, and it collects the actual position signal of the left gate in real time and feeds back the position signal to the signal input port of the programmable logic controller 100.

[0030] The right-side drive assembly 300 is located on the other side of the gate, and its structure is symmetrical to that of the left-side drive assembly 200. The right-side drive assembly 300 includes a right hydraulic cylinder 301, a right electro-hydraulic proportional valve 302, and a right displacement sensor 303. The right hydraulic cylinder 301 drives the right-side lifting point of the gate, the right electro-hydraulic proportional valve 302 receives control commands from the programmable logic controller 100 to adjust the flow rate of the right-side oil circuit, and the right displacement sensor 303 collects the actual position signal of the right-side gate and feeds it back to the programmable logic controller 100.

[0031] The programmable logic controller 100 is internally configured with a memory and a processor. The memory stores computer-executable instructions, and the processor executes the instructions to implement control logic. From the perspective of functional module division, the programmable logic controller 100 internally includes a discrete state observation module 110, a disturbance feature identification module 120, a virtual axis parameter scheduling module 130, and a control law synthesis module 140. These modules interact with each other via internal registers or a data bus.

[0032] The discrete state observation module 110 is configured to receive the left position signal fed back by the left displacement sensor 203 and the right position signal fed back by the right displacement sensor 303. Based on the input control voltage and the actual feedback position, the discrete state observation module 110 uses a discretized extended state observer algorithm to calculate and output the system state estimate and total disturbance estimate of each hydraulic cylinder in real time. The total disturbance estimate includes the perturbation of internal parameters of the hydraulic system and the resultant force interference exerted on the gate by the external environment.

[0033] The disturbance feature identification module 120 is connected to the discrete state observation module 110 and is configured to receive the total disturbance estimate. The disturbance feature identification module 120 analyzes the time-domain and frequency-domain characteristics of the total disturbance estimate and, in conjunction with the direction of the velocity state, decouples and identifies the current load condition type. The load condition type includes at least viscous stagnation, fluid impact, and normal operation. The disturbance feature identification module 120 outputs independent condition status flag signals for the left and right sides respectively.

[0034] The virtual axis parameter scheduling module 130 is connected to the disturbance feature identification module 120. Based on the operating condition flag signal, the virtual axis parameter scheduling module 130 calculates the stiffness coefficient, damping coefficient, and auxiliary excitation parameters of the virtual flexible axis for both the left and right sides using a preset asymmetric parameter mapping strategy. When the operating conditions on both sides are inconsistent, the virtual axis parameter scheduling module 130 assigns different stiffness coefficients and damping coefficients to both sides.

[0035] The control law synthesis module 140 is connected to both the discrete state observation module 110 and the virtual axis parameter scheduling module 130. The control law synthesis module 140 integrates the target position command, the state estimate and total disturbance estimate output by the discrete state observation module 110, and the stiffness coefficient and damping coefficient output by the virtual axis parameter scheduling module 130 to calculate the control voltage signals finally applied to the left electro-hydraulic proportional valve 202 and the right electro-hydraulic proportional valve 302. These control voltage signals drive the corresponding electro-hydraulic proportional valves to operate, thereby controlling the gate to complete its lifting and lowering motion.

[0036] The programmable logic controller 100 performs periodic scanning operations during operation, completing a full data acquisition, algorithm calculation, and control output within each scanning cycle h. The logic processing flow of the control system includes steps S210 to S250.

[0037] Step S210: Data Acquisition and Signal Preprocessing. The programmable logic controller 100 synchronously acquires the real-time position signals fed back by the left displacement sensor 203 and the right displacement sensor 303 through its analog input port. During the sampling process, the original analog electrical signals undergo analog-to-digital conversion (A / D) and digital filtering to obtain the current position signal. The actual displacement of the left gate and the actual displacement of the right gate The digital filtering process can employ moving average filtering or Butterworth low-pass filtering to remove high-frequency electrical noise interference and ensure the numerical stability of subsequent differential operations.

[0038] Step S220: Discrete state observation and total disturbance estimation. The discrete state observation module 110 reads the previous time step... Output control voltage , and the actual displacement at the current moment , The discrete state observation module 110 runs the discrete linear extended state observer algorithm for both the left and right sides. This step reconstructs the system's internal state variables at the current moment, including the position estimate, through differential iteration of the state-space equations. Speed ​​estimates and total disturbance estimate Subscript These represent the left and right sides, respectively. The total disturbance estimate... As an extended state variable, its value represents in real time the combined forces acting on the hydraulic cylinder, including fluid resistance, friction, and model parameter perturbations.

[0039] Step S230: Disturbance feature decoupling and operating condition identification. The disturbance feature identification module 120 receives the total disturbance estimate. and speed estimates In this step, the system analyzes the time-domain fluctuation characteristics of the total disturbance signal. Specifically, it quantifies the frequency domain characteristics of the disturbance by calculating the statistical magnitude of the change in the estimated total disturbance value within a set time window; simultaneously, it determines the current load characteristics by combining the correlation between the disturbance direction and the velocity direction. The disturbance feature identification module 120 determines the current operating status flag of each hydraulic cylinder based on a preset threshold logic. The operating condition status flag It is used to distinguish at least three states: viscous stagnation condition with large disturbance amplitude and low rate of change; fluid shock condition with disturbance rate of change exceeding a set threshold; and normal operation condition with parameters within the nominal range. Through this step, complex continuous physical disturbances are mapped into discrete operating condition signals.

[0040] Step S240, asymmetric virtual parameter scheduling. The virtual axis parameter scheduling module 130 is based on the left-side working condition status flag output in step S230. and the operating status indicator on the right side Virtual physical parameters are generated for both the left and right control loops. This step determines the virtual stiffness coefficient for the left side based on a preset asymmetric mapping strategy. Left virtual damping coefficient virtual stiffness coefficient on the right side and the virtual damping coefficient on the right side .when and When the indicated operating condition types are inconsistent, the system calculates... and They are not equal, or and They are not equal. If either side is determined to be in a viscous, stagnant condition, this step also simultaneously generates the corresponding high-frequency auxiliary excitation parameters. The virtual parameters can be generated using a lookup table method or a calculation method based on continuous functions.

[0041] Step S250: Control law synthesis and execution output. The control law synthesis module 140 is based on the target trajectory. The state estimate obtained in step S220 , , And using the virtual parameters determined in step S240, calculate the final control voltage. The control voltage The synthesis logic employs a linear superposition approach, comprising three main components and their corresponding gain coefficients: a feedback control component to eliminate position tracking errors, a feedforward compensation component to offset total disturbances, and a virtual coupling component to maintain dual-cylinder coordination. The feedforward compensation component directly utilizes the estimated total disturbance. Perform reverse cancellation. The virtual coupling component is based on... and The correction torque generated by the virtual axis is calculated. If auxiliary excitation parameters exist, a high-frequency sine wave signal is superimposed on the control voltage. The final calculated digital control quantity is converted from digital to analog (D / A) and output to the left electro-hydraulic proportional valve 202 and the right electro-hydraulic proportional valve 302 to drive the hydraulic valve core to move, thereby completing the closed-loop regulation of the gate's motion state within one scan cycle.

[0042] The discrete state observation module 110, as the state sensing unit of the control system, does not rely on the precise physical parameter model of the hydraulic gate, but instead adopts an extended state observation technology based on input and output data. To adapt to the cyclic scanning working mechanism of the programmable logic controller (PLC), the algorithm within this module is designed as an iterative operation in the discrete time domain. The specific implementation process of the discrete state observation module 110 includes steps S310 to S330.

[0043] Step S310: Establish a discretized extended state-space model of the controlled object. For the left hydraulic cylinder 201 and the right hydraulic cylinder 301, the system is considered a second-order dynamic system. At any time t, the motion equation of a single-sided hydraulic cylinder is defined as:

[0044] ;

[0045] in, For gate displacement, For the gate speed, The control voltage applied to the electro-hydraulic proportional valve, This represents the nominal control gain of the system. (Symbol) This represents the total disturbance acting on the system, which includes unmodeled dynamics within the system (including changes in the bulk modulus of hydraulic oil, internal leakage in the cylinder, and frictional forces of the seals) as well as unknown external disturbances (including water flow impact, wind load, and sediment resistance).

[0046] To achieve real-time estimation of the total disturbance, the present invention will Expand it into a new state variable. Considering the PLC's sampling period is... The continuous system is discretized using the Euler approximation method. Discrete time intervals are defined. The state variables are as follows: Indicates the actual displacement. Indicates actual speed. This represents the total disturbance. The discretized state equations of the system are expressed as:

[0047] ;

[0048] in, Let be the rate of change of the total disturbance, which is assumed to be bounded in engineering design. This model forms the mathematical basis for observer design.

[0049] Step S320: Construct the Discrete Linear Extended State Observer (LESO).

[0050] The discrete state observation module 110 runs the observer algorithm in each scan cycle of the PLC to generate estimated values ​​of the aforementioned state variables. Definition , , They are time points The estimated position, velocity, and total disturbance values.

[0051] The algorithm first calculates the observation error. That is, the position estimate output by the observer and the displacement value actually collected by the sensor. Deviation between:

[0052] ;

[0053] Subsequently, based on the estimated state from the previous moment and the current control input... Update the estimated state for the next time step. The observer's state iteration equation is as follows:

[0054] ;

[0055] in, , , These are the observer's correction gain coefficients. These coefficients determine the observer's speed of tracking the system state and its ability to suppress measurement noise. The total disturbance estimate is... The error is continuously corrected through integration until the observation error is corrected. Approaching zero, thus achieving a true total perturbation. Real-time approximation. This process enables the programmable logic controller to acquire and quantify disturbances that cannot be directly measured by physical sensors.

[0056] Step S330: Configure the observer gain parameters. To ensure stable convergence of the observer, the gain coefficient... , , Configure the observer based on the observer bandwidth parameterization method. Set the desired bandwidth of the observer to... The gain coefficients satisfy the following correspondence:

[0057] ;

[0058] In actual engineering implementation, The value is limited by the sampling period. and sensor noise levels. To ensure the numerical stability of the discrete system, and The product must satisfy convergence constraints (usually requiring...). Under the premise of satisfying this constraint, the following is usually selected. The rad / s is set to ensure the observation speed is faster than the system's dynamic response speed, while avoiding excessive amplification of the high-frequency noise of the displacement sensor. With this parameterized configuration, those skilled in the art only need to adjust... The observer's performance can be tuned with a single parameter, eliminating the need for tedious independent adjustments to three parameters.

[0059] After the above steps, the discrete state observation module 110 outputs independent state vectors for the left and right hydraulic cylinders respectively. and This data is then transmitted in real time to the subsequent disturbance feature identification module 120 and control law synthesis module 140. Among these, the velocity estimate... It is calculated through a mathematical model, and compared to directly performing differential operations on the displacement signal, it has a higher signal-to-noise ratio and smoothness; the total disturbance estimate is... This provides a quantitative basis for subsequent disturbance rejection control and operating condition identification.

[0060] The disturbance feature identification module 120, based on the state estimation data output by the discrete state observation module 110, maps continuously changing physical disturbance quantities into discrete operating condition indicators through time-domain statistical analysis and logical discrimination algorithms. The operation process of this module mainly includes steps S410 to S430.

[0061] Step S410: Extraction of time-domain features of the disturbance signal. The disturbance feature identification module 120 establishes a length of... A sliding window is used to store the most recent time frame. The total disturbance estimate sequence for each sampling period Based on this sequence, the system calculates the fluctuation characteristic index of the disturbance signal. It is used to quantify the drastic changes in the total disturbance over a short period of time. The specific calculation formula is defined as the average absolute deviation of the disturbance increment at adjacent time points within the sliding window:

[0062] ;

[0063] in, Indicates the left or right passage. This is the window length, and its value is set according to the sampling frequency, typically covering 0.5 to 1 second of sampled data to ensure the effectiveness of the statistical features. If... A smaller value indicates that the total disturbance changes gradually, mainly consisting of low-frequency components, such as constant frictional force or slowly changing viscous resistance; if A large value indicates that there are violent high-frequency oscillations in the total disturbance, which is consistent with the random characteristics of fluid turbulent impact.

[0064] ;

[0065] Among them, sgn For sign functions. When When the direction of the total disturbance is opposite to the direction of the velocity, the total disturbance exhibits damping or frictional characteristics, meaning the system is moving against resistance. When the direction of the total disturbance is the same as the direction of the velocity, the total disturbance exhibits thrust characteristics and is usually generated by the forward flow of water or the gravitational component.

[0066] Step S430: Multi-dimensional working condition logic judgment and status output.

[0067] The disturbance feature identification module 120 integrates the fluctuation feature index obtained in step S410. The direction discrimination factor obtained in step S420 It uses preset physical thresholds to classify and determine the operating condition, and outputs operating condition status flags. The decision logic is as follows:

[0068] First, the viscous stagnation condition is determined. The system determines it is currently in a viscous stagnation condition and assigns a value when the following logical conditions are met. :

[0069] ;

[0070] The physical meaning of this logic is: the direction of the disturbance is opposite to the direction of motion, and the rate of change of the disturbance is lower than the preset steady-state fluctuation threshold. At the same time, the resistance value exceeded the maximum allowable load threshold set by the system. This corresponds to the physical behavior of a gate when it gets stuck in silt or encounters rigid jamming.

[0071] Regarding the determination of fluid impact conditions, the system determines that it is currently in a fluid impact condition and assigns a value when the following logical conditions are met. :

[0072] ;

[0073] The physical meaning of this logic is: the disturbance signal contains a large number of high-frequency components, and the fluctuation amplitude exceeds the preset turbulence threshold. At this point, the system is primarily affected by irregular hydrodynamic forces, rather than mechanical obstruction. If none of the above conditions are met, the system is determined to be in normal operating condition and a value is assigned. Through the above steps, the disturbance feature identification module 120 decouples complex environmental forces that cannot be directly measured by position sensors into discrete state signals that can be invoked by subsequent control strategies. The data is transmitted in real time to the virtual axis parameter scheduling module 130 as the basis for decision-making on switching control modes.

[0074] The virtual axis parameter scheduling module 130 is the core decision-making unit for realizing dual-cylinder coordination and flexible obstacle avoidance. This module receives operating status flags from the disturbance feature identification module 120. and The virtual physical parameters used for dual-cylinder synchronous control are dynamically adjusted according to a preset asymmetric scheduling strategy. The operation of this module includes steps S510 to S530.

[0075] Step S510: Construct a coupling model of the virtual flexible shaft. The system constructs a virtual physical connection shaft between the left and right hydraulic cylinders using an algorithm. Unlike traditional rigid synchronous control, the virtual shaft defined in this invention has variable stiffness and damping characteristics. Define the virtual coupling control quantity. Its physical meaning is that a virtual axis is applied to the first... The correction control component for the side-mounted hydraulic cylinder. This control quantity is calculated based on the position and velocity differences between the two sides:

[0076] ;

[0077] in, and . and These represent the actual displacements on this side and the opposite side, respectively. and These are the velocity estimates for this side and the opposite side, respectively. In this model, Defined as the first The virtual stiffness coefficient on the side characterizes the strength of the system's correction to synchronization errors; Defined as the first The virtual damping coefficient on the side characterizes the system's ability to suppress relative motion oscillations. A key feature of this invention lies in the independence and time-varying nature of the parameters: that is, at the same time... The parameters used by the left-side controller Parameters used with the right-side controller They can be unequal. This decoupling design allows the system to actively reduce the transmission gain of the synchronization control force when it is blocked on one side, thereby avoiding excessive internal stress in the gate structure caused by pursuing position synchronization.

[0078] Step S520: Perform asymmetric parameter lookup and scheduling. The virtual axis parameter scheduling module 130 internally stores a parameter mapping table or a parameter function generator. Based on the input working condition combination... The system matches the optimal virtual parameters for both the left and right sides respectively. The specific scheduling logic is as follows: if in normal synchronization mode on both sides ( and The system is currently in standard operating condition. The module outputs a high stiffness coefficient. With moderate damping coefficient and The high stiffness coefficient under this configuration Ensure that the hydraulic cylinders on both sides maintain strict position synchronization, and simulate the effect of rigid mechanical shaft connection at the algorithm level to ensure smooth gate lifting and lowering.

[0079] If in a unilateral sticky or stuck escape mode (with the left side obstructed) The right side is normal. For example): At this point, the system determines that a unilateral fault has occurred. The module performs asymmetric scheduling: for the obstructed side (left side), maintain medium stiffness to maintain the tracking trend of the target trajectory; for the normal side (right side), adjust the virtual stiffness coefficient... Step reduction to relaxation stiffness Simultaneously increase the virtual damping coefficient Maximum damping value Wherein, the relaxation stiffness The value range is the nominal stiffness. 10% to 20%. This strategy involves significantly reducing... The control logic increases the tolerance of the right side to the positional deviation of the left side. When the left side is stuck, the right side no longer generates a large synchronous corrective force, thus avoiding pulling on the gate body; at the same time, the increased damping... This ensures the stability of the motion on the right side in the absence of synchronization constraints and prevents overshoot.

[0080] If in fluid impact or turbulence mode (either side) At this point, the system detects water flow disturbance. The module outputs a low stiffness coefficient. With high damping coefficient Reducing stiffness allows the gate to adapt to water flow fluctuations within a small range, avoiding actuator oscillations caused by frequent adjustments; increasing damping absorbs the impact energy of the water flow, increasing the dynamic stability of the system.

[0081] Step S530: Generate auxiliary excitation signal.

[0082] When the operating status indicator on either side When the condition is determined to be viscous and stagnant, the virtual axis parameter scheduling module 130 activates the auxiliary excitation function. The system generates a high-frequency sinusoidal dithering signal.

[0083] ;

[0084] in, For the excitation amplitude, The excitation frequency (usually set to or near the natural frequency of the electro-hydraulic proportional valve, such as 50Hz-100Hz). The sampling period is specified. This signal does not directly drive the gate to move significantly, but is superimposed on the control voltage, causing the hydraulic valve core and oil to vibrate slightly. This slight vibration significantly reduces the static friction coefficient of the system, using the vibration effect to assist the hydraulic cylinder in overcoming the critical value of static friction. For the unobstructed side, the signal remains zero. Through the above steps S510 to S530, the virtual axis parameter scheduling module 130 completes the transformation from condition perception to strategy decision-making, outputting specific physical control parameters. and auxiliary signals To the next level of control law synthesis module 140.

[0085] The control law synthesis module 140, as the execution layer of the control system, is responsible for comprehensively calculating the target instructions planned by the upper layer, the system state perceived by the observation layer, and the virtual parameters scheduled by the decision layer into the final control voltage signal that drives the electro-hydraulic proportional valve. The calculation process of this module includes steps S610 to S640.

[0086] Step S610: Calculate the trajectory tracking error.

[0087] The control law synthesis module 140 receives the target position trajectory set by the system. and the position estimate output by the discrete state observation module 110 Regarding the left side and the right side Calculate the position tracking error for each hydraulic cylinder. :

[0088] ;

[0089] The location estimate of the observer is used here. Displacement value measured directly instead of sensor Participated in error calculation. Because... After internal integration correction by the observer, the noise level is lower than that of the original measurement signal, thus achieving low-pass filtering of measurement noise at the physical level and preventing high-frequency noise from entering the control loop and causing high-frequency chattering of the actuator.

[0090] Step S620: Generate linear feedback control quantity. To ensure that the hydraulic cylinder can quickly and without overshoot track the target trajectory, the system uses a proportional-derivative (PD) control strategy to generate the basic linear feedback control quantity. This control variable represents the desired acceleration required for the driven object to reach the target state under an ideal, undisturbed model. Its calculation formula is:

[0091] ;

[0092] in, For position feedback gain, For speed feedback gain, This is a speed estimate. To simplify the parameter tuning process, this invention uses a bandwidth parameterization method to set the gain. The controller bandwidth is set to... The gain configuration then satisfies To ensure the stability of the closed-loop control system, the controller bandwidth... The value should be less than the observation bandwidth of the discrete state observation module 110. The value range usually satisfies This is to ensure that the observer can converge to the true state before the controller.

[0093] Step S630: Synthesize the final control voltage.

[0094] This step linearly superimposes the signals from feedback control, disturbance compensation, virtual synchronization coupling, and auxiliary excitation to generate the final control law. The control law synthesis module 140 uses the system's nominal control gain... Calculate the first Side hydraulic cylinder at all times control voltage :

[0095] ;

[0096] The definitions and functions of each physical quantity in the formula are as follows:

[0097] The linear feedback term from step S620 is used to eliminate tracking errors; The virtual coupling correction term from the virtual axis parameter scheduling module 130 has physical dimensions that are... Consistency (at the acceleration level) is used to introduce tension or thrust into the virtual axis, forcing the two cylinders to remain synchronized; : The total disturbance estimate from discrete state observation module 110. Subtraction is used in the formula ( This mathematically achieves feedforward compensation for the total disturbance, including nonlinear friction, water flow impact, and model errors. This compensation linearizes the complex nonlinear controlled object into an integral-series system under closed-loop dynamics. The nominal value of the system control gain, used as a normalization factor, converts speed-level control requirements into voltage-level control commands. The auxiliary excitation signal from the virtual axis parameter scheduling module 130 is directly superimposed on the final voltage to generate high-frequency chatter to reduce static friction.

[0098] Step S640: Control amplitude limiting and physical output.

[0099] The calculated theoretical control voltage It may exceed the physical tolerance of the electro-hydraulic proportional valve, so saturation limiting treatment must be performed.

[0100] definition For the maximum allowable control voltage, This is the minimum allowable control voltage. The output voltage after limiting. The calculation is as follows:

[0101] ;

[0102] Digital quantity after amplitude limiting The digital-to-analog converter (D / A) module of the programmable logic controller converts the signal into an analog current or voltage signal, which is then sent to the drive coils of the left electro-hydraulic proportional valve 202 and the right electro-hydraulic proportional valve 302, thereby completing the closed-loop regulation of the gate's motion state within one scan cycle.

Claims

1. A PLC-based control system for cofferdam gates in water conservancy projects, characterized in that, include: The hydraulic drive and detection assembly includes a left hydraulic cylinder and a right hydraulic cylinder respectively installed on both sides of the gate, a left electro-hydraulic proportional valve and a right electro-hydraulic proportional valve respectively controlling the left hydraulic cylinder and the right hydraulic cylinder, and a left displacement sensor and a right displacement sensor respectively detecting the displacement of the left hydraulic cylinder and the right hydraulic cylinder. The controller is electrically connected to the left electro-hydraulic proportional valve, the right electro-hydraulic proportional valve, the left displacement sensor, and the right displacement sensor; the controller is internally configured with a logic operation unit, which performs functions including the following modules: The discrete state observation module is used to receive the target position trajectory and the detection values ​​of the left displacement sensor and the right displacement sensor, and to estimate the position, velocity and total disturbance of the hydraulic cylinders on both sides using the state observation algorithm. The disturbance feature identification module is used to calculate the disturbance fluctuation index and motion direction factor based on the velocity estimate and the total disturbance estimate, and determine the current operating condition of the system accordingly; the operating condition includes at least normal operation condition, unilateral jamming condition and turbulent impact condition. The virtual shaft parameter scheduling module is used to establish a virtual synchronous coupling relationship between the two hydraulic cylinders, and adjust the virtual stiffness coefficient and virtual damping coefficient of the virtual synchronous coupling relationship in real time according to the working condition, as well as generate an auxiliary excitation signal. The control law synthesis module is used to calculate and output control voltage to the left electro-hydraulic proportional valve and the right electro-hydraulic proportional valve based on the position estimate, the velocity estimate, the total disturbance estimate, the virtual stiffness coefficient, the virtual damping coefficient and the auxiliary excitation signal.

2. The PLC-based water conservancy project cofferdam gate control system according to claim 1, characterized in that, The discrete state observation module constructs an extended state model that includes position state, velocity state, and disturbance state. The discrete state observation module calculates the tracking error between the position estimate and the detected value, and uses the tracking error to correct and update the disturbance state, the velocity state, and the position state; wherein, the total disturbance estimate is used to characterize the total system disturbance, including friction, water flow impact force, and model uncertainty.

3. The PLC-based water conservancy project cofferdam gate control system according to claim 1, characterized in that, The disturbance feature identification module is equipped with a sliding data window for collecting the total disturbance estimate within a set time period. The disturbance feature identification module obtains the disturbance fluctuation index by calculating the standard deviation or coefficient of variation of the data within the sliding data window, and determines the motion direction factor by judging whether the direction of the total disturbance estimate is opposite to the direction of the velocity estimate.

4. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 3, characterized in that, The specific logic for the disturbance feature identification module to determine the operating condition is as follows: When the disturbance fluctuation index exceeds the preset turbulence threshold, it is determined to be the turbulence impact condition; When the disturbance fluctuation index does not exceed the turbulence threshold, and the motion direction factor indicates that the disturbance direction is opposite to the motion direction, and the amplitude of the total disturbance estimate exceeds the preset steady-state threshold, it is determined to be the single-sided jamming condition. Except for the above situations, it is determined to be the normal operating condition.

5. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 1, characterized in that, Under normal operating conditions, the virtual shaft parameter scheduling module configures the virtual stiffness coefficient and the virtual damping coefficient to preset high stiffness values ​​and high damping values ​​to maintain the rigidity synchronization of the hydraulic cylinders on both sides. Under the turbulent impact condition, the virtual stiffness coefficient and the virtual damping coefficient are configured to be lower than the preset low values ​​of the high stiffness value and the high damping value, so as to reduce the coupling strength between the two hydraulic cylinders.

6. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 1, characterized in that, The virtual axis parameter scheduling module executes an asymmetric parameter scheduling strategy under the single-sided jamming condition: For the hydraulic cylinder on the side where jamming occurs, the virtual stiffness coefficient is kept constant, and a non-zero auxiliary excitation signal is generated. For the normal hydraulic cylinder on the side that is not jammed, the virtual stiffness coefficient is reduced to a preset relaxation threshold, and the auxiliary excitation signal is not generated.

7. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 1, characterized in that, The process by which the control law synthesis module calculates the control voltage of any hydraulic cylinder includes: Calculate the linear feedback control quantity used to eliminate trajectory tracking error; Based on the virtual stiffness coefficient, the virtual damping coefficient, and the position estimation difference and velocity estimation difference of the two hydraulic cylinders, a virtual coupling correction term is calculated; The linear feedback control quantity and the virtual coupling correction term are summed, and the total disturbance estimate is subtracted to perform feedforward compensation, thus obtaining the intermediate control quantity. The intermediate control quantity is normalized using the system's nominal control gain, and then superimposed with the auxiliary excitation signal to obtain the control voltage.

8. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 7, characterized in that, The control law synthesis module uses a proportional-derivative control strategy to calculate the linear feedback control quantity. The specific calculation method is as follows: Calculate the product of the position feedback gain and the position tracking error, and use it as a proportional term; Calculate the product of the speed feedback gain and the speed estimate, and use it as the differential term; The difference between the proportional term and the derivative term is calculated and used as the linear feedback control quantity; The position tracking error is the difference between the target position trajectory and the position estimate.

9. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 8, characterized in that, The position feedback gain and the velocity feedback gain are parameterized based on the controller bandwidth; The position feedback gain is configured as the square of the controller bandwidth, and the speed feedback gain is configured as twice the controller bandwidth. Furthermore, the range of the controller bandwidth is configured to be less than one-fifth to one-third of the observation bandwidth of the discrete state observation module.

10. A PLC-based control system for cofferdam gates in water conservancy projects according to claim 7, characterized in that, The control law synthesis module also includes an amplitude limiting step: Preset the maximum and minimum allowable control voltage; The calculated control voltage is compared with the maximum allowable control voltage and the minimum allowable control voltage; If the control voltage is greater than the maximum allowable control voltage, then the maximum allowable control voltage is output; If the control voltage is less than the minimum allowable control voltage, then the minimum allowable control voltage is output; Otherwise, the calculated control voltage is output directly.

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