PLC-based hydraulic station oil temperature automatic control system

Abstract

The present application relates to the technical fields of hydraulic system control, and discloses a kind of hydraulic station oil temperature automatic control system based on PLC, including hydraulic station ontology, oil temperature sensor, PLC controller, man-machine interface, electric ball valve, alarm module and intermediate relay.Oil temperature sensor collects temperature and is converted into 0-20mA standard current signal transmission to PLC;PLC uses first-in first-out data queue to filter original signal, and is converted into real-time temperature value by linear interpolation.The PLC executes double-position control logic according to the cooling start temperature and the hysteresis temperature parameters, drives the intermediate relay to act to control the power supply loop of electric ball valve, so as to adjust the cooling waterway.The present application constructs control dead zone through algorithm linkage, effectively avoids the frequent oscillation of actuator caused by signal fluctuation, and realizes the accurate, stable and safe control of hydraulic station oil temperature by combining input loop signal diagnosis and fault interlocking mechanism.

Description

Technical Field

[0001] This invention relates to the field of hydraulic system control technology, specifically to a PLC-based automatic oil temperature control system for a hydraulic station. Background Technology

[0002] As the power core of modern industrial machinery, hydraulic power units inevitably convert some mechanical energy into heat energy during long-term continuous operation due to mechanical friction of pump and valve components and pressure loss of hydraulic oil flowing through throttling orifices, leading to an increase in hydraulic oil temperature. Excessively high oil temperature reduces hydraulic oil viscosity, weakens oil film strength, and accelerates seal aging and component wear, even causing system pressure build-up failure. Therefore, hydraulic systems are typically equipped with forced cooling devices, using plate or tubular heat exchangers to introduce external circulating water as the cooling medium. The hydraulic oil temperature is regulated by controlling the on / off state or flow rate of the cooling water, ensuring the system maintains a suitable thermal equilibrium operating state.

[0003] In existing industrial applications, hydraulic power station oil temperature control systems generally use a programmable logic controller (PLC) as the control core, in conjunction with temperature sensors installed on the oil tank or return oil line for monitoring. The typical operation is as follows: the temperature sensor converts the collected physical temperature into an analog voltage or current signal, which is transmitted to the PLC's analog input module. The PLC's internal program quantizes this signal into a digital value and performs real-time logical operations to compare it with a pre-set target temperature parameter. When the detected current temperature value is higher than the set threshold, the PLC outputs a control signal to drive the solenoid valve or electric actuator installed on the heat exchanger's inlet water line to open, thus initiating cooling water circulation. When the temperature value drops below the set value, the PLC cancels the output signal and closes the valve to stop cooling.

[0004] However, existing control logic has significant limitations in processing sensor signals. Due to the complex industrial environment, the analog signals transmitted by temperature sensors are easily interfered with by electromagnetic noise generated by high-powered equipment such as frequency converters and motors. At the same time, the turbulence of fluid in the hydraulic tank can also cause instantaneous fluctuations in local temperature. Most existing technologies directly use a single threshold comparison logic, lacking effective filtering and smoothing of the raw acquired signals and hysteresis settings for the executed actions. When the monitored temperature value is near the critical point of the start-up threshold, the tiny noise or fluctuations superimposed on the real signal can cause the logic judgment result to jump rapidly between meeting and not meeting the conditions. This leads to frequent opening and closing oscillations of the cooling water valves in a short period of time. This phenomenon not only fails to maintain a stable oil temperature but also causes mechanical fatigue and premature damage to the electric actuators and switching devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a PLC-based automatic oil temperature control system for hydraulic stations, which solves the problems mentioned in the background section.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: a PLC-based automatic oil temperature control system for hydraulic stations, which aims to solve the problems of low oil temperature control accuracy, slow hardware response, and lack of effective fault interlock protection in traditional hydraulic stations.

[0007] The system mainly consists of a hydraulic power unit, an oil temperature sensor, a PLC controller, a human-machine interface, an electric ball valve, an alarm module, and an intermediate relay. In terms of hardware architecture, the oil temperature sensor is installed on the hydraulic power unit and is responsible for converting the collected physical temperature into a 0-20mA standard current signal and transmitting it to the analog input port of the PLC controller. The electric ball valve is installed on the inlet pipe of the hydraulic power unit's heat exchanger and is used to regulate the flow of cooling water. The first digital output port of the PLC controller is connected to the coil of the intermediate relay, and the normally open contact of the intermediate relay is connected in series in the power supply circuit of the electric ball valve.

[0008] The system executes core logic operations through a PLC controller, receiving 0-20mA standard current signals from sensors and converting them into digital real-time temperature values ​​through an internal calculation program. The PLC controller then controls the on / off state of an intermediate relay coil based on this real-time temperature value, thereby using the normally open contacts of the intermediate relay to control the high-voltage circuit of the electric ball valve, achieving electrical isolation between low-voltage and high-voltage control and automatic oil temperature regulation. The human-machine interface (HMI) is connected to the PLC controller via an Ethernet communication cable and follows the S7 communication protocol. As the master station of the communication network, the HMI periodically reads data registers to update the display and writes temperature setpoint parameters to the PLC controller's holding register.

[0009] The second aspect of this invention relates to a data processing method and temperature control logic configured within the aforementioned system, which improves the system's anti-interference capability and control stability through first-in-first-out queue filtering, linear interpolation transformation, and hysteresis control algorithms.

[0010] Specifically, the PLC controller is internally configured with a first-in-first-out (FIFO) data queue. Before performing numerical conversion, the PLC controller quantizes the 0-20mA standard current signal acquired from the analog input port into a raw digital quantity and performs digital filtering. The processing steps are as follows: in each scan cycle, the latest sampled value is stored and the oldest sampled value stored in the FIFO data queue is removed. The arithmetic mean of all data in the queue is calculated, and this arithmetic mean is used as the valid real-time sampled digital quantity.

[0011] Subsequently, the PLC controller converts the real-time sampled digital value into a real-time temperature value in the physical dimension using linear interpolation logic. This linear interpolation logic performs calculations based on pre-stored lower and upper temperature detection limits, as well as the maximum digital value corresponding to the hardware resolution of the analog input module. The calculation formula for the real-time temperature value is as follows: In the formula, This is a real-time temperature value. To sample digital quantities in real time, The maximum numerical value. This is the upper limit of temperature detection. This is the lower limit for temperature detection.

[0012] After obtaining accurate real-time temperature values, the PLC controller executes two-position control logic with hysteresis characteristics to avoid frequent oscillations in the actuator. The system presets cooling start-up temperature parameters and hysteresis temperature parameters, and the control logic is as follows: When the real-time temperature value is greater than or equal to the cooling start temperature parameter, the PLC controller executes a set command to drive the intermediate relay to engage, thereby opening the electric ball valve. When the real-time temperature value drops to the stop threshold, the PLC controller executes a reset command, which drives the intermediate relay to disconnect, thereby closing the electric ball valve; The stop threshold is set as the calculated value of the cooling start temperature parameter minus the hysteresis temperature parameter.

[0013] Furthermore, the system integrates signal diagnostic logic and safety interlocking mechanisms for the input circuit. The PLC controller monitors the raw digital values ​​of the analog input channels in real time. When the value indicates hardware overflow or exceeds the preset physical signal linearity range, it determines that there is a hardware fault in the oil temperature sensor or its signal transmission cable. Once a fault is detected, the PLC controller immediately executes the fault safety interlock, forcibly cutting off the power supply to the intermediate relay coil. Regardless of the current temperature value, it forces the electric ball valve to reset to the closed state, preventing the cooling water circuit from being mis-connected due to signal distortion. Simultaneously, when the real-time temperature value exceeds the preset alarm threshold parameter, the PLC controller drives the alarm module connected to the second digital output port to issue an audible and visual warning signal, and provides feedback through alarm status indicator lights in the equipment status indication area of ​​the HMI. The HMI also integrates user security management logic, restricting modification permissions to the parameter holding register through a password verification mechanism to ensure the security of the system's operating parameters.

[0014] This invention provides a PLC-based automatic oil temperature control system for a hydraulic power station. It offers the following advantages: 1. This invention uses a first-in-first-out (FIFO) data queue to digitally filter the acquired analog current signal, eliminating numerical fluctuations caused by electromagnetic interference in industrial environments. Then, based on linear interpolation logic, the smoothed digital value is accurately converted into a physical temperature value. On this basis, the control program combines cooling start-up temperature and hysteresis temperature parameters to construct a two-position control model, setting the start and stop points of valve action. This algorithmic linkage mechanism effectively solves the problem of frequent start-stop oscillations of the actuator caused by instantaneous signal jumps, significantly extending the mechanical service life of the electric ball valve and intermediate relay while ensuring oil temperature control accuracy.

[0015] 2. This invention monitors the raw numerical status of the analog input channel in real time by executing signal diagnostic logic in the input circuit. When a numerical indication hardware overflow or exceeding the preset physical signal linearity range is detected, the system automatically determines that there is a hardware fault in the sensor or transmission cable. Once the fault is confirmed, the control program immediately triggers the fault-safe interlock mechanism, ignoring the current temperature calculation results and forcibly cutting off the power supply to the intermediate relay coil. This logic ensures that in extreme conditions such as sensor failure or signal distortion, the cooling water circuit can automatically reset to the off state, preventing the system from misleading the water circuit based on erroneous data and avoiding potential water waste or equipment damage risks.

[0016] 3. This invention constructs a strong-weak current isolated output circuit using an intermediate relay, utilizing a low-voltage DC signal to control a high-voltage AC load, effectively shielding the core logic circuit of the controller from electrical switch noise. Combined with the human-machine interface's communication master station architecture and hierarchical access control logic, the system achieves real-time visual interaction of data and secure parameter writing. Only after password verification can critical control parameters be modified. This hardware and software integration design not only ensures the electrical system's anti-interference capability but also avoids the risk of unauthorized personnel misoperation leading to abnormal process parameters, improving the standardization and security of the hydraulic station's automated management. Attached Figure Description

[0017] Figure 1 This is a structural diagram of the automatic oil temperature control system for a PLC-based hydraulic station. Figure 2 This is a schematic diagram of the control flow of the present invention.

[0018] The components include: 1. Hydraulic station body; 2. Oil temperature sensor; 3. PLC controller; 4. Human-machine interface; 5. Electric ball valve; and 6. Alarm module. Detailed Implementation

[0019] 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.

[0020] Example: Please see the appendix Figure 1 -Appendix Figure 2 This invention provides a PLC-based automatic oil temperature control system for a hydraulic station, whose main hardware components include: a hydraulic station body 1, an oil temperature sensor 2, a PLC controller 3, a human-machine interface 4, an electric ball valve 5, and an alarm module 6.

[0021] The hydraulic station body 1 is equipped with an oil circuit and a heat exchanger for cooling hydraulic oil. The heat exchanger has an inlet pipe for connecting to an external water source and an outlet pipe for discharging wastewater.

[0022] The oil temperature sensor 2 is installed at the bottom of the oil tank or in the oil outlet pipeline of the hydraulic station body 1. This position allows it to contact the circulating hydraulic oil to reflect the real-time average oil temperature of the system. The signal output terminal of the oil temperature sensor 2 is connected to the analog input terminal of the PLC controller 3 via a shielded cable to convert the collected temperature physical quantity into a 0-20mA standard current signal for transmission.

[0023] The electric ball valve 5 is installed on the inlet pipe of the heat exchanger via a flange, and is an on / off type electric ball valve. The control terminal of the electric ball valve 5 is connected to the digital output terminal of the PLC controller 3, receives the control level signal output by the PLC controller 3, and executes the valve opening or closing action, thereby controlling the on / off of the cooling water circuit.

[0024] PLC controller 3 is an industrial-grade programmable logic controller, which stores the temperature control program internally. PLC controller 3 is electrically connected to oil temperature sensor 2, electric ball valve 5 and alarm module 6, respectively, and is used to perform signal acquisition, logic comparison calculation and control command output.

[0025] The human-machine interface 4 is installed on the surface of the control cabinet of the hydraulic station and is connected to the PLC controller 3 via a communication bus. The human-machine interface 4 is used to display the real-time oil temperature value and the on / off status of the equipment, and allows the user to input the cooling start temperature and alarm threshold parameters.

[0026] The alarm module 6 is connected to the output of the PLC controller 3. When the PLC controller 3 determines that the oil temperature data exceeds the preset safety value, it drives the alarm module 6 to issue an audible and visual alarm signal.

[0027] The oil temperature sensor 2 is screwed into the bottom of the oil tank of the hydraulic station body 1 for sealing, or installed in the circulation pipeline at the outlet of the hydraulic pump, ensuring that the temperature probe is completely immersed in the oil medium to obtain accurate oil temperature data. The signal output terminal of the oil temperature sensor 2 is connected to a shielded twisted-pair cable, which is connected to the analog input port of the PLC controller 3. The shielding layer of the shielded twisted-pair cable is grounded at one end on the control cabinet side where the PLC controller 3 is located to eliminate the influence of high-frequency electromagnetic interference in the industrial environment on the weak current signal.

[0028] The electric ball valve 5 is connected to the inlet pipe of the heat exchanger via a standard flange, and its installation direction is consistent with the water flow direction. The drive actuator of the electric ball valve 5 is connected to the digital output port of the PLC controller 3 via a control cable. In this embodiment, if the electric ball valve 5 is powered by DC24V, the PLC controller 3 directly outputs a control signal; if the electric ball valve 5 is powered by AC220V, the output port of the PLC controller 3 is connected to the electric ball valve 5 through an intermediate relay, and the normally open contact of the intermediate relay controls the on / off of the high-voltage circuit of the electric ball valve 5, realizing electrical isolation between low-voltage control and high-voltage control.

[0029] The human-machine interface 4 is connected to the communication port of the PLC controller 3 via an Ethernet communication cable. Both are configured with the same IP network segment to establish a data exchange channel using the S7 communication protocol. The control terminal of the alarm module 6 is connected to the preset alarm output point of the PLC controller 3.

[0030] In terms of system power supply, an AC220V to DC24V switching power supply module is provided. The DC output terminal of the switching power supply module is connected to the power input terminals of the PLC controller 3, the oil temperature sensor 2 and the human-machine interface 4 respectively, so as to realize the common ground connection of each low-voltage control component.

[0031] After the system is powered on and initialized, the operator inputs the cooling start temperature parameter Tset and the alarm threshold parameter Tlimit through the human-machine interface 4. The human-machine interface 4 writes the above-mentioned set parameters into the holding register of the PLC controller 3 for storage via the S7 communication protocol, so that the control program can call them.

[0032] The oil temperature sensor 2 collects the oil temperature in the hydraulic circuit in real time and converts the physical temperature into a 0-20mA standard current signal, which is then transmitted to the PLC controller 3. The analog input module of the PLC controller 3 reads this current signal and converts it into a digital real-time temperature value Tmeas through its internal calculation program.

[0033] PLC controller 3 performs a logical comparison between the real-time temperature value Tmeas and the cooling start-up temperature parameter Tset according to a preset scan cycle. When the real-time temperature value Tmeas is greater than or equal to the cooling start-up temperature parameter Tset, PLC controller 3 determines that the cooling condition is met and outputs an open signal to drive electric ball valve 5. Electric ball valve 5 responds and opens its valve core, opening the cooling water path of the heat exchanger, allowing cooling water to flow through the heat exchanger to cool the hydraulic oil.

[0034] When the real-time temperature value Tmeas drops below the cooling start-up temperature parameter Tset, PLC controller 3 outputs a shutdown signal. Electric ball valve 5 responds and closes its valve core, cutting off the cooling water circuit, and the system enters standby monitoring mode. PLC controller 3 cyclically executes the above sampling and control steps to achieve automatic oil temperature regulation.

[0035] Meanwhile, PLC controller 3 independently runs the safety monitoring program. If the real-time temperature value Tmeas rises above the alarm threshold parameter Tlimit, PLC controller 3 immediately triggers an alarm output, driving alarm module 6 to issue an audible and visual warning until the oil temperature drops back to the allowable range.

[0036] The hydraulic power unit 1 includes an oil storage tank, a hydraulic pump unit, and a plate heat exchanger. The plate heat exchanger is connected in series in the return oil pipeline of the hydraulic power unit 1, and has a cooling water inlet and a cooling water outlet on its side. The inlet is connected to an external industrial circulating water pipeline through a standard flange interface.

[0037] The oil temperature sensor 2 is an integrated temperature sensor with a transmitter module, and its core temperature sensing element is a PT100 platinum resistance thermometer. The transmitter circuit integrated inside the sensor linearly converts the resistance value of the PT100 temperature sensing element as it changes with temperature into a 0-20mA standard analog current signal. In this embodiment, the range of the oil temperature sensor 2 is set to 0℃ to 100℃, corresponding to an output current of 0mA to 20mA.

[0038] In one installation configuration, the oil temperature sensor 2 is vertically screwed into the lower side wall of the oil reservoir via a G1 / 2 threaded interface. The installation point is positioned 100mm to 150mm above the bottom of the reservoir. This installation height ensures that the temperature sensor is within the effective circulation layer of the hydraulic oil, avoiding obstruction from deposited impurities at the bottom of the reservoir and guaranteeing that the sensor remains submerged in the oil during fluid level fluctuations, thereby obtaining accurate average oil temperature data.

[0039] In another installation configuration, the oil temperature sensor 2 is installed on the main return oil pipeline of the hydraulic station body 1, upstream of the oil inlet of the plate heat exchanger. At this location, the oil temperature sensor 2 is sealed and fixed via a pipeline tee joint, enabling direct detection of the real-time oil temperature returning from the system. During installation, PTFE tape is wrapped around the threaded connection or an O-ring is added to ensure high-pressure sealing performance.

[0040] The hardware components of the control and interaction unit and its signal interaction methods include the following: Electric ball valve 5 is installed on the inlet pipe of the plate heat exchanger, located between the cooling water source and the heat exchanger inlet. Electric ball valve 5 is a switch-type stainless steel electric ball valve adapted to the pipe diameter, with a nominal pressure rating of PN1.6MPa. Electric ball valve 5 consists of two parts: an electric actuator and a ball valve body, which are mechanically connected by a bracket and a coupling.

[0041] The ball valve body has standard flanges at both ends, which are bolted to the mating flanges on the inlet pipe. Rubber gaskets are placed between the flange connection surfaces to ensure the pipeline's sealing under high-pressure water flow. The valve core of the ball valve body has a spherical structure with a 90-degree rotation stroke. When the valve core rotates to the point where the through hole is parallel to the pipe axis, the water flow is connected; when the valve core rotates 90 degrees to the point where the through hole is perpendicular to the pipe axis, the water flow is cut off.

[0042] The electric actuator integrates a drive motor and a reduction gearbox. The control input of the electric actuator is connected to the output circuit of the PLC controller 3. In this embodiment, the electric actuator uses a three-wire control method or a two-wire method with a reset function. When the PLC controller 3 outputs an open signal, the drive motor rotates forward, causing the valve core to rotate to the fully open position and triggering the limit switch to stop the machine. When the PLC controller 3 outputs a close signal or cancels the open signal, the drive motor reverses or relies on the reset spring to rotate the valve core to the fully closed position.

[0043] In addition, the electric ball valve 5 is also equipped with a manual operating handle. In case of system power failure or electric actuator malfunction, the operator can manually rotate the valve core through this handle to forcibly open or close the cooling water circuit, ensuring the system's emergency operation capability.

[0044] PLC controller 3 is an industrial-grade miniature programmable logic controller, installed on a standard DIN rail inside the hydraulic station's electrical control cabinet. PLC controller 3 integrates a central processing unit, memory, 220V power supply circuit, and input / output interface circuits, serving as the core of the entire system's logic operations.

[0045] The analog input terminal AI of PLC controller 3 is configured for current signal acquisition mode, adapting to 0-20mA standard signals, and is used to receive real-time sampling data transmitted by oil temperature sensor 2. The analog-to-digital converter (A / D) module inside PLC controller 3 converts the acquired analog current signal into a digital quantity and maps it to the internal data register.

[0046] The digital output port DO of PLC controller 3 can be either transistor output or relay output type. The first digital output port is connected to the intermediate relay coil in the electric ball valve control circuit or directly to the control terminal to output valve opening and closing commands; the second digital output port is connected to alarm module 6 to output alarm drive levels. The output ports are isolated from the internal circuitry via optocouplers to improve the system's anti-interference capability.

[0047] The HMI 4 uses an embedded touch screen, which is embedded in the door panel of the electrical control cabinet, with the screen facing outwards. The back of the HMI 4 has a power interface and a communication interface, and is powered by a DC 24V switching power supply.

[0048] The HMI 4 and PLC controller 3 are connected via an Ethernet communication cable. The communication ports of both devices follow the S7 communication protocol and are configured to use the same IP network segment. In this communication network, the HMI 4 acts as a slave, periodically reading data from designated registers within the PLC controller 3 to update the temperature value displayed on the screen, and responding to user touch operations by writing temperature setting thresholds to the parameter holding register of the PLC controller 3.

[0049] The method for digital conversion and linear calibration of temperature signals processed internally by a PLC controller includes the following steps: The analog input channel of PLC controller 3 acquires a 0-20mA standard analog current signal from oil temperature sensor 2 in real time. The analog-to-digital converter (A / D) module inside PLC controller 3 quantizes this analog signal into a digital integer value. The quantization range of this digital integer value is determined by the hardware resolution of the analog input module; in this example, the digital range is defined as 0 to... Where 0 corresponds to 0mA input, It corresponds to a 20mA full-scale input.

[0050] To eliminate signal fluctuations caused by electromagnetic interference in industrial environments and ensure the stability of temperature readings, PLC controller 3 performs digital filtering on the acquired raw digital values ​​before performing numerical conversion. The control program allocates a first-in, first-out (FIFO) data queue of length N in memory, for example, N=10. In each scan cycle, the program stores the latest sampled value and removes the oldest sampled value from the queue, calculates the arithmetic mean of all data in the queue, and uses this average as the valid real-time sampled digital value. .

[0051] The control program internally stores physical range parameters that match those of oil temperature sensor 2. The lower limit for temperature detection is set. Set the upper limit of temperature detection to 0℃. The temperature is 100℃.

[0052] PLC controller 3 executes the linear interpolation calculation program to convert the filtered sampled digital quantity Convert to physical temperature value. The program uses floating-point data format for intermediate calculations to ensure accuracy; the actual temperature value is... The calculation formula is as follows: For example, in this embodiment, if a 12-bit resolution analog module is selected, or if the Siemens standard analog protocol is selected, then... Typically defined as 27648, when the sampled digital value after filtering... When the value is 13824, PLC controller 3 calculates the current real-time oil temperature according to the above formula. The temperature is 50.0℃.

[0053] The logic comparison and output control strategy of the PLC controller based on real-time temperature values ​​includes the following: The PLC controller 3's internal data register pre-stores the cooling start-up temperature parameter. Hysteresis temperature parameters and alarm threshold parameters Based on the above parameters, PLC controller 3 constructs a two-position control model with hysteresis characteristics to define the action switching boundary of electric ball valve 5.

[0054] PLC controller 3 executes the control program cyclically according to a preset scan cycle. Within each scan cycle, the program calls numerical comparison instructions to process the real-time temperature value after linear transformation. .

[0055] Entering the cooling control logic segment: PLC controller 3 first determines the real-time temperature value. Is it greater than or equal to the cooling start temperature parameter? If the comparison condition is met, PLC controller 3 executes a Set instruction, latching the corresponding digital output bit of electric ball valve 5 to a high level. At this time, electric ball valve 5 is opened under control, and the cooling water circuit is connected.

[0056] Subsequently, PLC controller 3 determines the real-time temperature value. Has it fallen to the stopping threshold (i.e.) and (The difference). If the real-time temperature value Less than or equal to the stopping threshold ( When PLC controller 3 executes a reset command, it toggles the digital output bit of the corresponding electric ball valve 5 to a low level. At this time, electric ball valve 5 is closed, and the cooling water circuit is cut off. This is achieved by introducing a hysteresis temperature parameter. The system creates a control dead zone between the start and stop points, preventing frequent start-stop oscillations of the electric ball valve 5 caused by fluctuations in the sampling signal.

[0057] After executing the cooling logic described above, PLC controller 3 continues to execute the over-temperature alarm monitoring logic. The program will display the real-time temperature value. With alarm threshold parameters Compare the values. If the real-time temperature value... Greater than or equal to alarm threshold parameter The PLC controller 3 sets the alarm output port, driving the alarm module 6 to issue a warning signal; when the real-time temperature value... Falling back to a safe range, for example When the preset hysteresis is subtracted, the PLC controller 3 resets the alarm output port.

[0058] The system's fault diagnosis and safety protection execution process under abnormal operating conditions includes the following steps: Within each scan cycle of the main control program, PLC controller 3 independently calls the alarm handling subroutine. This subroutine reads the real-time temperature value after filtering and linear transformation. and compare it with the alarm threshold parameter stored in the parameter holding register. Perform numerical comparison.

[0059] When the real-time temperature value Greater than or equal to alarm threshold parameter When the temperature exceeds the set value, the over-temperature alarm soft element inside the PLC controller 3, such as the internal auxiliary relay M, is set. Based on the logic state of this soft element, the PLC controller 3 drives the digital output port connected to the alarm module 6 to close. This output port connects to the external power supply circuit of the alarm module 6 via an intermediate relay, causing it to emit an audible and visual warning signal.

[0060] While executing the hardware output, the PLC controller 3 writes the corresponding fault code into the status register mapped to the HMI 4. The HMI 4 polls the value of this register via the S7 communication protocol, and upon detecting a fault code, invokes the internal alarm script. The HMI 4 then displays an alarm window on the screen containing the fault name and current value, and automatically saves the timestamp and type of the fault to the historical database.

[0061] In addition, PLC controller 3 executes signal diagnostic logic for the input circuit. The program monitors the raw digital values ​​of the analog input channels in real time. When the raw digital value indicates hardware overflow or exceeds the preset physical signal linearity range, PLC controller 3 determines that there is a hardware fault in oil temperature sensor 2 or its signal transmission cable.

[0062] Once a sensor malfunction is detected, PLC controller 3 triggers a sensor malfunction alarm and immediately executes the fault safety interlock. The control program forcibly cuts off the control output signal of electric ball valve 5, regardless of the current calculated temperature value, and forces electric ball valve 5 to reset to the closed state to prevent the controller from misleadingly opening the cooling water circuit based on distorted sensor signals.

[0063] The layout of the human-computer interface 4 and the distribution of its interactive function areas are as follows: The HMI 4's operating screen is divided into three logical functional areas: a real-time monitoring area, a parameter setting area, and a device status indication area. These areas are distinguished by graphical dividing lines or background color blocks to clearly define the boundaries between data display and operational control.

[0064] The real-time monitoring area is located at the core of the screen and is equipped with a numerical display control. The read address of this control is mapped to the real-time temperature value stored internally in PLC controller 3. The data register. The human-machine interface 4 periodically reads the value of this register via the S7 communication protocol and refreshes the display of the current hydraulic oil temperature in a floating-point format with one decimal place. A static text label is configured next to the numerical display control to display the temperature unit symbol "C".

[0065] The parameter setting area is equipped with multiple numerical input controls, each corresponding to the cooling start-up temperature parameter. Hysteresis temperature parameters and alarm threshold parameters Each numeric input control's write address is associated with a designated parameter holding register within the PLC controller 3. When an operator touches a numeric input control, the HMI 4 invokes a pop-up numeric keypad window. After the operator inputs and confirms the set value, the HMI 4 writes the value to the corresponding register in the PLC controller 3, completing the parameter update.

[0066] The equipment status indicator area is equipped with multi-state indicator lights to provide feedback on the system's execution actions and alarm status. The valve status indicator lights are associated with the digital output address of the PLC controller 3, which controls the electric ball valve 5. When the digital output address is "1", the valve status indicator light displays the open state color, such as green, indicating that the cooling water circuit is open; when the digital output address is "0", the indicator light displays the closed state color, such as gray.

[0067] The alarm status indicator light is linked to the over-temperature alarm software or fault code register inside the PLC controller 3. Under normal operating conditions, the alarm status indicator light remains hidden or displays the normal status color; when the PLC controller 3 determines that an over-temperature fault or sensor fault has occurred, the alarm status indicator light flips to the alarm status color, such as red, and flashes, while the alarm bar component at the bottom of the interface displays the specific fault text information.

[0068] Furthermore, the human-machine interface 4 integrates user security management logic. The numerical input controls in the parameter setting area are assigned operation permission levels. The system is in a locked state by default; operators must enter a preset administrator password through the login window. Only after the system verifies that the permission level matches can write access to the parameter setting area be unlocked, preventing unauthorized personnel from accidentally modifying critical control parameters.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PLC-based automatic oil temperature control system for a hydraulic station, characterized in that, It includes the following modules: hydraulic station body 1, oil temperature sensor 2, PLC controller 3, human-machine interface 4, electric ball valve 5, alarm module 6, and intermediate relay; The oil temperature sensor 2 is installed on the hydraulic station body 1 and is used to convert the collected temperature physical quantity into a 0-20mA standard current signal and transmit it. The oil temperature sensor 2 is electrically connected to the analog input port of the PLC controller 3. The electric ball valve 5 is installed on the inlet pipe of the heat exchanger of the hydraulic station body 1; The first digital output port of the PLC controller 3 is connected to the coil of the intermediate relay; The normally open contact of the intermediate relay is connected in series in the power supply circuit of the electric ball valve 5, and the normally open contact of the intermediate relay is used to control the on / off of the power supply circuit of the electric ball valve 5. The alarm module 6 is connected to the second digital output port of the PLC controller 3; The human-machine interface 4 is electrically connected to the communication port of the PLC controller 3; The PLC controller 3 is configured to: receive the 0-20mA standard current signal, convert the 0-20mA standard current signal into a digital real-time temperature value through an internal calculation program, and control the on / off state of the intermediate relay coil according to the real-time temperature value, thereby adjusting the on / off state of the electric ball valve 5.

2. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 1, characterized in that, The human-machine interface 4 and the PLC controller 3 are connected via an Ethernet communication cable, and the human-machine interface 4 and the PLC controller 3 follow the S7 communication protocol. The human-machine interface 4 is configured as a slave station of the communication network, periodically reading the data register of the PLC controller 3 to update the temperature value displayed on the screen, and writing the temperature setting parameter to the holding register of the PLC controller 3.

3. The automatic oil temperature control system for a hydraulic station based on PLC according to claim 1, characterized in that, The PLC controller 3 is configured to drive the alarm module 6 to issue an audible and visual warning signal when it determines that the real-time temperature value is greater than or equal to a preset alarm threshold parameter.

4. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 1, characterized in that, The PLC controller 3 is internally configured with a first-in-first-out data queue; Before performing numerical conversion, the PLC controller 3 quantizes the 0-20mA standard current signal acquired by the analog input port into a raw digital quantity, and performs digital filtering processing on the raw digital quantity. The PLC controller 3 stores the latest sampled value in each scan cycle and removes the oldest sampled value stored in the first-in-first-out data queue. It calculates the arithmetic mean of all data in the first-in-first-out data queue and uses the calculated arithmetic mean as the effective real-time sampled digital quantity.

5. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 4, characterized in that, The PLC controller 3 stores the lower limit value of temperature detection, the upper limit value of temperature detection, and the maximum digital value corresponding to the hardware resolution of the analog input module. The PLC controller 3 converts the real-time sampled digital quantity into the real-time temperature value according to linear interpolation logic. The linear interpolation logic is specifically as follows: The real-time sampled digital value is divided by the maximum digital value to obtain a ratio. This ratio is then multiplied by the difference between the upper and lower temperature detection limits. Finally, the lower temperature detection limit is added to obtain the real-time temperature value.

6. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 5, characterized in that, The PLC controller 3 has its internal data register pre-stored cooling start-up temperature parameters and hysteresis temperature parameters. The PLC controller 3 executes the following temperature control logic: When the real-time temperature value is greater than or equal to the cooling start temperature parameter, the PLC controller 3 executes a set command to drive the intermediate relay to activate and open the electric ball valve 5. When the real-time temperature value drops to the stop threshold, the PLC controller 3 executes a reset command to drive the intermediate relay to disconnect and close the electric ball valve 5; The stop threshold is the calculated value of the cooling start temperature parameter minus the hysteresis temperature parameter.

7. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 4, characterized in that, The PLC controller 3 is configured to execute signal diagnostic logic for the input loop; When the PLC controller 3 detects that the original digital value of the analog input channel indicates hardware overflow or exceeds the preset physical signal linear range, the PLC controller 3 determines that there is a hardware fault in the oil temperature sensor 2 or the signal transmission cable of the oil temperature sensor 2. After determining that the oil temperature sensor 2 has a hardware fault, the PLC controller 3 immediately executes the fault safety interlock, forcibly cutting off the power supply to the coil of the intermediate relay, so that the electric ball valve 5 is reset to the closed state.

8. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 1, characterized in that, The human-machine interface 4 has a device status indicator area on its operating screen; The equipment status indication area includes multi-state indicator lights, and the valve status indicator light in the multi-state indicator lights is associated with the digital output bit address of the PLC controller 3 controlling the electric ball valve 5; When the state of the digital output bit address is 1, the valve status indicator light displays the open state color; when the state of the digital output bit address is 0, the valve status indicator light displays the closed state color.

9. The automatic oil temperature control system for a hydraulic station based on PLC according to claim 8, characterized in that, The device status indication area includes alarm status indicator lights; The alarm status indicator light is associated with the over-temperature alarm soft element inside the PLC controller 3; When the PLC controller 3 determines that an over-temperature fault has occurred, the alarm status indicator light will display the alarm status color and flash.

10. The PLC-based automatic oil temperature control system for a hydraulic station according to claim 2, characterized in that, The human-machine interface 4 integrates user security management logic; The parameter setting area of ​​the human-machine interface 4 is equipped with a numerical input control, and the write address of the numerical input control is associated with the holding register of the PLC controller 3. The numerical input control is set with an operation permission level. When the operator enters the preset administrator password through the login window and the system verifies that the permission level matches, the human-machine interface 4 unlocks the write permission of the parameter setting area, allowing the operator to modify the data in the holding register.

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