Intelligent lubrication system for port gantry crane

Abstract

This invention relates to the field of lubrication system technology and proposes an intelligent lubrication system for dock gantry cranes. The system includes an oil pump control circuit comprising an operational amplifier U1, a NAND gate U2, a NOT gate U3, switching transistors Q1 and Q2, and a resistor R4. The non-inverting input of operational amplifier U1 is connected to a reference voltage Vref. The output of operational amplifier U1 is connected to the first input of NAND gate U2. The input of NOT gate U3 is connected to the main control unit, and the input of NOT gate U3 is connected to the second input of NAND gate U2. The output of NAND gate U2 is connected to the control terminal of switching transistor Q1, and the output of NOT gate U3 is connected to the control terminal of switching transistor Q2. The first terminal of switching transistor Q1 is connected to a 24V power supply, and the second terminal of switching transistor Q1 is connected to the first terminal of the oil pump. The first terminal of switching transistor Q2 is connected to the second terminal of the oil pump, and the second terminal of switching transistor Q2 is grounded through resistor R4. The second terminal of switching transistor Q2 is connected to the inverting input of operational amplifier U1. This technical solution solves the problem of unstable power supply operation of the oil pump in related technologies.

Description

Technical Field

[0001] This invention relates to the field of lubrication system technology, and more specifically, to an intelligent lubrication system for dock gantry cranes. Background Technology

[0002] Gantry cranes play a crucial role in port transportation. A gantry crane is a type of rotating, rail-mounted crane whose rotating mechanism causes the hoisted cargo to rotate around its center of rotation, enabling horizontal transport of goods. As the most frequently used part of the gantry crane, the rotating structure must meet the requirements of low-speed forward and reverse rotation, smooth braking, and high reliability. Its operational stability directly affects the overall performance and efficiency of the equipment. Therefore, the rotating mechanism of the gantry crane must have comprehensive lubrication, maintenance, upkeep, and monitoring measures to ensure efficient and stable operation, thereby extending equipment lifespan, reducing operating costs, and improving equipment safety and reliability. Due to the complex working environment at the port, the existing lubrication system of the gantry crane's rotating mechanism frequently experiences problems such as the oil pump failing to start properly due to unstable power supply, leading to unreliable lubrication system operation. Summary of the Invention

[0003] This invention proposes an intelligent lubrication system for dock gantry cranes, which solves the problem of unstable power supply to oil pumps in related technologies.

[0004] The technical solution of the present invention is as follows:

[0005] The intelligent lubrication system for the dock gantry crane includes an oil pump control circuit and a main control unit. The oil pump control circuit is connected to the main control unit. The oil pump control circuit includes an operational amplifier U1, a NAND gate U2, a NOT gate U3, a switching transistor Q1, a switching transistor Q2, a transistor Q5, resistors R1 and R4.

[0006] The non-inverting input of operational amplifier U1 is connected to the reference voltage Vref. The output of operational amplifier U1 is connected to the first input of NAND gate U2. The input of NOT gate U3 is connected to the first output of the main control unit. The output of NAND gate U2 is connected to the control terminal of switching transistor Q1. The output of NOT gate U3 is connected to the second input of NAND gate U2. The output of NOT gate U3 is connected to the control terminal of switching transistor Q2. The first terminal of switching transistor Q1 is connected to a 24V power supply. The second terminal of switching transistor Q1 is connected to the first terminal of the oil pump. The first terminal of switching transistor Q2 is connected to the second terminal of the oil pump. The second terminal of switching transistor Q2 is grounded through resistor R4. The second terminal of switching transistor Q2 is connected to the inverting input of operational amplifier U1.

[0007] The base of transistor Q5 is connected to the second terminal of switching transistor Q2, the emitter of transistor Q5 is connected to the control terminal of switching transistor Q2, and the collector of transistor Q5 is grounded through resistor R1.

[0008] Furthermore, the present invention also includes a valve control circuit, which includes a resistor R2, a switching transistor Q3, a resistor R3, a resistor R5, a switching transistor Q4, and a resistor R6. The first end of the resistor R2 is connected to the second output terminal of the main control unit, and the second end of the resistor R2 is connected to the control terminal of the switching transistor Q3. The first end of the switching transistor Q3 is connected to a 12V power supply, and the second end of the switching transistor Q3 is grounded through the resistor R3. The second end of the switching transistor Q3 is connected to the control terminal of the switching transistor Q4 through the resistor R5. The first end of the switching transistor Q4 is connected to a 12V power supply through the resistor R6. The first end of the switching transistor Q4 is connected to the first end of the solenoid valve coil L2, and the second end of the solenoid valve coil L2 is connected to a 12V power supply. The second end of the switching transistor Q4 is grounded.

[0009] Furthermore, the present invention also includes an oil level detection circuit, which includes a first electrode J1, a second electrode J2, resistors R7, R8, and R9, a capacitor C2, an operational amplifier U4, resistors R10 and R11, and a NOT gate U5.

[0010] The first end of resistor R7 is connected to a 5V power supply. The second end of resistor R7 is connected to the inverting input of operational amplifier U4 through capacitor C2. The second end of resistor R7 is connected to the non-inverting input of operational amplifier U4 through resistor R9. The second end of resistor R7 is grounded through resistor R8. The inverting input of operational amplifier U4 is connected to the first electrode J1. The output of operational amplifier U4 is connected to the non-inverting input of operational amplifier U4 through resistor R10. The output of operational amplifier U4 is connected to the second electrode J2 through resistor R11. The output of operational amplifier U4 is connected to the input of NOT gate U5. The output of NOT gate U5 is connected to the first input of the main control unit.

[0011] Furthermore, the present invention also includes a pressure detection circuit, which includes an operational amplifier U6, a resistor R12, a pressure sensor H1, resistors R13 and R14, an operational amplifier U7, and a resistor R15. The non-inverting input terminal of the operational amplifier U6 is connected to the Vref reference voltage, and the inverting input terminal of the operational amplifier U6 is grounded through the resistor R12. The output terminal of the operational amplifier U6 is connected to the first power supply terminal of the pressure sensor H1, and the second power supply terminal of the pressure sensor H1 is connected to the inverting input terminal of the operational amplifier U6. The first output terminal of the pressure sensor H1 is connected to the non-inverting input terminal of the operational amplifier U7 through the resistor R13, and the second output terminal of the pressure sensor H1 is connected to the inverting input terminal of the operational amplifier U7 through the resistor R14. The output terminal of the operational amplifier U7 is connected to the inverting input terminal of the operational amplifier U7 through the resistor R15, and the output terminal of the operational amplifier U7 is connected to the second input terminal of the main control unit.

[0012] Furthermore, the pressure detection circuit described in this invention also includes a thermistor RT and a variable resistor RP1. The first end of the thermistor RT is connected to a 5V power supply, the second end of the thermistor RT is connected to the first end of the variable resistor RP1, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the non-inverting input of the operational amplifier U7.

[0013] Furthermore, a filter circuit is provided between the output terminal of the operational amplifier U7 and the second input terminal of the main control unit in this invention. The filter circuit includes a resistor R16, a capacitor C3, a resistor R17, a capacitor C4, a resistor R18, an operational amplifier U8, a resistor R19, and a resistor R20. The first end of the resistor R16 is connected to the output terminal of the operational amplifier U7, and the second end of the resistor R16 is grounded through the capacitor C3. The second end of the resistor R16 is connected to the first end of the capacitor C4, and the second end of the capacitor C4 is grounded through the resistor R18. The second end of the capacitor C4 is connected to the non-inverting input terminal of the operational amplifier U8, and the inverting input terminal of the operational amplifier U8 is grounded through the resistor R19. The output terminal of the operational amplifier U8 is connected to the inverting input terminal of the operational amplifier U8 through the resistor R20, and the output terminal of the operational amplifier U8 is connected to the second end of the resistor R16 through the resistor R17. The output terminal of the operational amplifier U8 is connected to the second input terminal of the main control unit.

[0014] The working principle and beneficial effects of this invention are as follows:

[0015] In this invention, the oil pump control circuit is used to control the opening and closing of the oil pump in the gantry crane lubrication system. The working principle of the oil pump control circuit is as follows:

[0016] When the rotating mechanism of the gantry crane requires lubrication, the first output terminal of the main control unit sends a low-level signal to the input terminal of the NOT gate U3, and the NOT gate U3 outputs a high-level signal. During normal operation, the operational amplifier U1 outputs a high level, the NAND gate U2 outputs a low level, and both switching transistors Q1 and Q2 are turned on. The 24V power supply passes through switching transistor Q1, the oil pump's power supply coil L1, switching transistor Q2, and resistor R4 before reaching ground. The oil pump's power supply coil L1 is powered on, and the oil pump starts to draw grease to lubricate the rotating mechanism of the gantry crane, ensuring efficient and stable operation. When the gantry crane finishes operation or the grease addition time is over, the first output terminal of the main control unit outputs a high-level signal, the NOT gate U3 outputs a low level, the switching transistor Q2 is turned off, and the oil pump's power supply coil L1 is de-energized. Due to the complex working environment at the dock, the power supply to the oil pump's power supply coil L1 is unstable. When the current is too high, the oil pump's power supply coil L1 will overheat severely, which will affect the service life of the oil pump in the long run. If the current exceeds the rated value of the power supply coil L1, the oil pump may burn out directly. When the current is too low, the oil pump may fail to start normally, affecting the normal lubrication and maintenance of the gantry crane's rotating mechanism.

[0017] When the oil pump starts normally, a voltage is generated across resistor R4. If the current flowing through the power supply coil L1 increases, the voltage across resistor R4 will also increase, leading to a larger base current in transistor Q5 and a smaller collector current. This results in a smaller voltage across resistor R1 and a smaller control voltage for the switching transistor Q2, thus suppressing the increase in current flowing through the power supply coil L1. Conversely, if the current flowing through the power supply coil L1 decreases, the voltage across resistor R4 will decrease, leading to a smaller base current in transistor Q5 and a larger collector current. This again reduces the voltage across resistor R1 and increases the control voltage for the switching transistor Q2, thus suppressing the decrease in current flowing through the power supply coil L1. Therefore, in this invention, the oil pump's power supply coil L1 can operate in a constant current state, unaffected by environmental conditions. When the current flowing through the power supply coil L1 is too large, the voltage at the inverting input terminal of the operational amplifier U1 will exceed the reference voltage at the non-inverting input terminal of the operational amplifier U1. The operational amplifier U1 forms a comparator and outputs a low level. Therefore, the NAND gate U2 outputs a high level, and the switching transistor Q1 is cut off. At this time, the power supply coil L1 of the oil pump is de-energized to prevent damage to the oil pump due to excessive current.

[0018] Therefore, the oil pump control circuit in this invention not only ensures the stability of the current when the oil pump is working, but also plays a role in overcurrent protection, thereby improving the stability of oil pump control. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a circuit diagram of the oil pump control circuit in this invention;

[0021] Figure 2 This is a circuit diagram of the valve control circuit in this invention;

[0022] Figure 3 This is a circuit diagram of the oil level detection circuit in this invention;

[0023] Figure 4 This is a circuit diagram of the pressure detection circuit in this invention;

[0024] Figure 5 This is a circuit diagram of the filter circuit in this invention. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0026] Example 1

[0027] like Figure 1 As shown, this embodiment proposes an intelligent lubrication system for a dock gantry crane, including an oil pump control circuit and a main control unit. The oil pump control circuit is connected to the main control unit. The oil pump control circuit includes an operational amplifier U1, a NAND gate U2, a NOT gate U3, a switching transistor Q1, a switching transistor Q2, a transistor Q5, resistors R1 and R4. The non-inverting input of operational amplifier U1 is connected to the reference voltage Vref, and the output of operational amplifier U1 is connected to the first input of NAND gate U2. The input of NOT gate U3 is connected to the first output of the main control unit, and the output of NAND gate U2 is connected to the control terminal of switching transistor Q1. The output of NOT gate U3 is connected to the control terminal of switching transistor Q1. The output terminal is connected to the second input terminal of NAND gate U2, the output terminal of NOT gate U3 is connected to the control terminal of switch transistor Q2, the first terminal of switch transistor Q1 is connected to the 24V power supply, the second terminal of switch transistor Q1 is connected to the first terminal of oil pump, the first terminal of switch transistor Q2 is connected to the second terminal of oil pump, the second terminal of switch transistor Q2 is grounded through resistor R4, the second terminal of switch transistor Q2 is connected to the inverting input terminal of operational amplifier U1, the base of transistor Q5 is connected to the second terminal of switch transistor Q2, the emitter of transistor Q5 is connected to the control terminal of switch transistor Q2, and the collector of transistor Q5 is grounded through resistor R1.

[0028] In this embodiment, the oil pump control circuit is used to control the opening and closing of the oil pump in the gantry crane lubrication system. Specifically, the working principle of the oil pump control circuit is as follows:

[0029] When the rotating mechanism of the gantry crane requires lubrication, the first output terminal of the main control unit sends a low-level signal to the input terminal of the NOT gate U3, and the NOT gate U3 outputs a high-level signal. During normal operation, the operational amplifier U1 outputs a high level, the NAND gate U2 outputs a low level, and both switching transistors Q1 and Q2 are turned on. The 24V power supply passes through switching transistor Q1, the oil pump's power supply coil L1, switching transistor Q2, and resistor R4 before reaching ground. The oil pump's power supply coil L1 is powered on, and the oil pump starts to draw grease to lubricate the rotating mechanism of the gantry crane, ensuring efficient and stable operation. When the gantry crane finishes operation or the grease addition time is over, the first output terminal of the main control unit outputs a high-level signal, the NOT gate U3 outputs a low level, the switching transistor Q2 is turned off, and the oil pump's power supply coil L1 is de-energized.

[0030] Due to the complex working environment at the dock, the power supply to the oil pump's power supply coil L1 is unstable. When the current is too high, the oil pump's power supply coil L1 will overheat severely, which will affect the service life of the oil pump in the long run. If the current exceeds the rated value of the power supply coil L1, the oil pump may burn out directly. When the current is too low, the oil pump may fail to start normally, affecting the normal lubrication and maintenance of the gantry crane's rotating mechanism.

[0031] When the oil pump starts normally, a voltage is generated across resistor R4. If the current flowing through the power supply coil L1 increases, the voltage across resistor R4 will also increase, leading to a larger base current in transistor Q5 and a smaller collector current. This results in a smaller voltage across resistor R1 and a smaller control voltage for the switching transistor Q2, thus suppressing the increase in current flowing through the power supply coil L1. Conversely, if the current flowing through the power supply coil L1 decreases, the voltage across resistor R4 will decrease, leading to a smaller base current in transistor Q5 and a larger collector current. This again reduces the voltage across resistor R1 and increases the control voltage for the switching transistor Q2, thus suppressing the decrease in current flowing through the power supply coil L1. Therefore, in this embodiment, the oil pump's power supply coil L1 can operate in a constant current state, unaffected by environmental conditions.

[0032] When the current flowing through the power supply coil L1 is too large, the voltage at the inverting input terminal of the operational amplifier U1 will exceed the reference voltage at the non-inverting input terminal of the operational amplifier U1. The operational amplifier U1 forms a comparator and outputs a low level. Therefore, the NAND gate U2 outputs a high level, and the switching transistor Q1 is cut off. At this time, the power supply coil L1 of the oil pump is de-energized to prevent damage to the oil pump due to excessive current.

[0033] like Figure 2As shown, this embodiment also includes a valve control circuit, which includes a resistor R2, a switching transistor Q3, a resistor R3, a resistor R5, a switching transistor Q4, and a resistor R6. The first end of the resistor R2 is connected to the second output terminal of the main control unit, and the second end of the resistor R2 is connected to the control terminal of the switching transistor Q3. The first end of the switching transistor Q3 is connected to a 12V power supply, and the second end of the switching transistor Q3 is grounded through the resistor R3. The second end of the switching transistor Q3 is connected to the control terminal of the switching transistor Q4 through the resistor R5, and the first end of the switching transistor Q4 is connected to a 12V power supply through the resistor R6. The first end of the switching transistor Q4 is connected to the first end of the solenoid valve coil L2, and the second end of the solenoid valve coil L2 is connected to a 12V power supply. The second end of the switching transistor Q4 is grounded.

[0034] The gantry crane's rotating mechanism has multiple lubrication points, each requiring different lubrication intervals and grease amounts. Existing rotating mechanism lubrication systems are mostly single-line or double-line centralized lubrication methods. Their biggest drawback is the inability to adjust lubrication according to the actual conditions of each lubrication point, easily leading to over-lubrication (waste), under-lubrication, or even interruption of lubrication resulting in grease deficiency. Furthermore, the lack of a monitoring system can easily cause equipment failure over time. Therefore, this embodiment employs a single-point lubrication method. Each lubrication point is equipped with a solenoid valve, and each solenoid valve corresponds to a valve control circuit. When lubrication is needed at that point, the main control unit sends a control command to the valve control circuit to open the solenoid valve at that point, and then activates the oil pump to add grease to the rotating mechanism at that point.

[0035] Specifically, the working principle of the valve control circuit is as follows: When the rotating mechanism at a certain point needs lubrication, the second output terminal of the main control unit outputs a low-level control signal to the control terminal of the switching transistor Q3. The switching transistor Q3 is turned on, a voltage is generated across the resistor R3, and the switching transistor Q4 is also turned on. At this time, the first terminal of the switching transistor Q4 is approximately grounded, the solenoid valve coil L2 is energized, and the valve opens. When the grease addition is completed, the second output terminal of the main control unit outputs a high level, the switching transistor Q3 is turned off, the switching transistor Q4 is also turned off, and the valve closes.

[0036] like Figure 3As shown, this embodiment also includes an oil level detection circuit. The oil level detection circuit includes a first electrode J1, a second electrode J2, resistors R7, R8, and R9, a capacitor C2, an operational amplifier U4, resistors R10 and R11, and a NOT gate U5. The first end of resistor R7 is connected to a 5V power supply. The second end of resistor R7 is connected to the inverting input of operational amplifier U4 through capacitor C2. The second end of resistor R7 is connected to the non-inverting input of operational amplifier U4 through resistor R9. The second end of resistor R7 is grounded through resistor R8. The inverting input of operational amplifier U4 is connected to the first electrode J1. The output of operational amplifier U4 is connected to the non-inverting input of operational amplifier U4 through resistor R10. The output of operational amplifier U4 is connected to the second electrode J2 through resistor R11. The output of operational amplifier U4 is connected to the input of NOT gate U5. The output of NOT gate U5 is connected to the first input of the main control unit.

[0037] When the lubrication system is working, the grease in the storage device needs to be extracted. When the grease in the storage device is low, grease should be added to the storage device in a timely manner to avoid affecting the normal operation of the gate machine. In this embodiment, the remaining amount of grease in the storage device is detected by the oil level detection circuit. When the remaining amount of grease is lower than the set value, the staff should be reminded to add grease.

[0038] Specifically, the working principle of the oil level detection circuit is as follows: The first electrode J1 and the second electrode J2 are both electrode rods, which are vertically fixed in the grease. Since the grease has a certain conductivity, the resistance of the grease will be different depending on the amount of grease remaining. Thus, the resistor R7, capacitor C2, operational amplifier U4, and the resistance of the grease constitute an RC oscillator. Depending on the amount of grease remaining, the frequency output by operational amplifier U4 will be different. The main control unit can determine the amount of grease remaining based on the number of pulses received per unit time. The NOT gate U5 can play a shaping role, making the pulse waveform received by the main control unit more stable, thereby improving the detection accuracy of the oil level.

[0039] like Figure 4 As shown, this embodiment also includes a pressure detection circuit, which includes operational amplifier U6, resistor R12, pressure sensor H1, resistors R13 and R14, operational amplifier U7, and resistor R15. The non-inverting input of operational amplifier U6 is connected to the Vref reference voltage, and the inverting input of operational amplifier U6 is grounded through resistor R12. The output of operational amplifier U6 is connected to the first power supply terminal of pressure sensor H1, and the second power supply terminal of pressure sensor H1 is connected to the inverting input terminal of operational amplifier U6. The first output of pressure sensor H1 is connected to the non-inverting input of operational amplifier U7 through resistor R13, and the second output of pressure sensor H1 is connected to the inverting input terminal of operational amplifier U7 through resistor R14. The output of operational amplifier U7 is connected to the inverting input terminal of operational amplifier U7 through resistor R15, and the output of operational amplifier U7 is connected to the second input terminal of the main control unit.

[0040] During long-term operation, the lubrication system of the gantry crane may experience blockage of the grease nipple or leakage of the oil pipe. When such faults occur, the rotating mechanism of the gantry crane will not achieve a good lubrication effect. Therefore, a pressure detection circuit is installed on the oil pipe. When the grease nipple is blocked or the oil pipe leaks, the pressure in the oil pipe will change. The lubrication system is judged based on the pressure in the oil pipe.

[0041] Specifically, the working principle of the pressure detection circuit is as follows: Operational amplifier U6 and pressure sensor H1 constitute a constant voltage source circuit. Because the working environment is relatively complex, the operating voltage of pressure sensor H1 will be affected. When the voltage of pressure sensor H1 increases, the voltage at the inverting input terminal of operational amplifier U6 increases. Operational amplifier U6 constitutes a subtraction circuit. When the voltage at the inverting input terminal of operational amplifier U6 increases, the output voltage of operational amplifier U6 will decrease; when the voltage of pressure sensor H1 decreases, the voltage at the inverting input terminal of operational amplifier U6 decreases, and the output voltage of operational amplifier U6 will increase. Therefore, pressure sensor H1 can operate in a constant voltage state, ensuring that the operation of pressure sensor H1 is more stable.

[0042] Pressure sensor H1 is used to convert pressure signal into electrical signal output. However, the electrical signal output by pressure sensor H1 is relatively weak and needs to be amplified. Therefore, operational amplifier U7 forms an amplifier circuit to amplify the electrical signal output by pressure sensor H1, and then the amplified signal is sent to the main control unit.

[0043] like Figure 4 As shown, the pressure detection circuit in this embodiment also includes a thermistor RT and a variable resistor RP1. The first end of the thermistor RT is connected to a 5V power supply, the second end of the thermistor RT is connected to the first end of the variable resistor RP1, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the non-inverting input of the operational amplifier U7.

[0044] In addition to being affected by voltage, pressure sensor H1 is also affected by ambient temperature. Therefore, the thermistor RT and the variable resistor RP1 form a temperature compensation circuit, which is applied to the non-inverting input of operational amplifier U7 to reduce the influence of temperature on pressure sensor H1.

[0045] like Figure 5As shown, in this embodiment, a filter circuit is also provided between the output terminal of operational amplifier U7 and the second input terminal of the main control unit. The filter circuit includes resistor R16, capacitor C3, resistor R17, capacitor C4, resistor R18, operational amplifier U8, resistor R19, and resistor R20. The first end of resistor R16 is connected to the output terminal of operational amplifier U7, and the second end of resistor R16 is grounded through capacitor C3. The second end of resistor R16 is connected to the first end of capacitor C4, and the second end of capacitor C4 is grounded through resistor R18. The second end of capacitor C4 is connected to the non-inverting input terminal of operational amplifier U8, and the inverting input terminal of operational amplifier U8 is grounded through resistor R19. The output terminal of operational amplifier U8 is connected to the inverting input terminal of operational amplifier U8 through resistor R20, and the output terminal of operational amplifier U8 is connected to the second end of resistor R16 through resistor R17. The output terminal of operational amplifier U8 is connected to the second input terminal of the main control unit.

[0046] The electrical signal output by operational amplifier U7 contains interference signals, which will seriously affect the accuracy of pressure detection. Therefore, it is necessary to filter out these interference signals. In this embodiment, a filtering circuit is added between the output terminal of operational amplifier U7 and the second input terminal of the main control unit.

[0047] The filter circuit consists of resistor R16, capacitor C3, resistor R17, capacitor C4, resistor R18, operational amplifier U8, resistor R19, and resistor R20. It is used to filter out high-frequency interference and noise signals in the output signal of operational amplifier U7, and finally send the filtered electrical signal to the main control unit.

[0048] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A smart lubrication system for a dock gantry crane, characterized in that, The system includes an oil pump control circuit and a main control unit. The oil pump control circuit is connected to the main control unit. The oil pump control circuit includes an operational amplifier U1, a NAND gate U2, a NOT gate U3, a switching transistor Q1, a switching transistor Q2, a transistor Q5, resistors R1 and R4. The non-inverting input of operational amplifier U1 is connected to the reference voltage Vref. The output of operational amplifier U1 is connected to the first input of NAND gate U2. The input of NOT gate U3 is connected to the first output of the main control unit. The output of NAND gate U2 is connected to the control terminal of switching transistor Q1. The output of NOT gate U3 is connected to the second input of NAND gate U2. The output of NOT gate U3 is connected to the control terminal of switching transistor Q2. The first terminal of switching transistor Q1 is connected to a 24V power supply. The second terminal of switching transistor Q1 is connected to the first terminal of the oil pump. The first terminal of switching transistor Q2 is connected to the second terminal of the oil pump. The second terminal of switching transistor Q2 is grounded through resistor R4. The second terminal of switching transistor Q2 is connected to the inverting input of operational amplifier U1. The base of transistor Q5 is connected to the second terminal of switching transistor Q2, the emitter of transistor Q5 is connected to the control terminal of switching transistor Q2, and the collector of transistor Q5 is grounded through resistor R1.

2. The intelligent lubrication system for gantry cranes according to claim 1, characterized in that, It also includes a valve control circuit, which includes a resistor R2, a switching transistor Q3, a resistor R3, a resistor R5, a switching transistor Q4, and a resistor R6. The first end of the resistor R2 is connected to the second output terminal of the main control unit, and the second end of the resistor R2 is connected to the control terminal of the switching transistor Q3. The first end of the switching transistor Q3 is connected to a 12V power supply, and the second end of the switching transistor Q3 is grounded through the resistor R3. The second end of the switching transistor Q3 is connected to the control terminal of the switching transistor Q4 through the resistor R5. The first end of the switching transistor Q4 is connected to a 12V power supply through the resistor R6. The first end of the switching transistor Q4 is connected to the first end of the solenoid valve coil L2, and the second end of the solenoid valve coil L2 is connected to a 12V power supply. The second end of the switching transistor Q4 is grounded.

3. The intelligent lubrication system for gantry cranes according to claim 1, characterized in that, It also includes an oil level detection circuit, which comprises a first electrode J1, a second electrode J2, resistors R7, R8, and R9, a capacitor C2, an operational amplifier U4, resistors R10 and R11, and a NOT gate U5. The first end of resistor R7 is connected to a 5V power supply. The second end of resistor R7 is connected to the inverting input of operational amplifier U4 through capacitor C2. The second end of resistor R7 is connected to the non-inverting input of operational amplifier U4 through resistor R9. The second end of resistor R7 is grounded through resistor R8. The inverting input of operational amplifier U4 is connected to the first electrode J1. The output of operational amplifier U4 is connected to the non-inverting input of operational amplifier U4 through resistor R10. The output of operational amplifier U4 is connected to the second electrode J2 through resistor R11. The output of operational amplifier U4 is connected to the input of NOT gate U5. The output of NOT gate U5 is connected to the first input of the main control unit.

4. The intelligent lubrication system for dock gantry cranes according to claim 1, characterized in that, It also includes a pressure detection circuit, which comprises an operational amplifier U6, a resistor R12, a pressure sensor H1, resistors R13 and R14, an operational amplifier U7, and a resistor R15. The non-inverting input of the operational amplifier U6 is connected to the Vref reference voltage, and the inverting input of the operational amplifier U6 is grounded through the resistor R12. The output of the operational amplifier U6 is connected to the first power supply terminal of the pressure sensor H1, and the second power supply terminal of the pressure sensor H1 is connected to the inverting input terminal of the operational amplifier U6. The first output terminal of the pressure sensor H1 is connected to the non-inverting input terminal of the operational amplifier U7 through the resistor R13, and the second output terminal of the pressure sensor H1 is connected to the inverting input terminal of the operational amplifier U7 through the resistor R14. The output terminal of the operational amplifier U7 is connected to the inverting input terminal of the operational amplifier U7 through the resistor R15, and the output terminal of the operational amplifier U7 is connected to the second input terminal of the main control unit.

5. The intelligent lubrication system for dock gantry cranes according to claim 4, characterized in that, The pressure detection circuit also includes a thermistor RT and a variable resistor RP1. The first end of the thermistor RT is connected to a 5V power supply, the second end of the thermistor RT is connected to the first end of the variable resistor RP1, the second end of the variable resistor RP1 is grounded, and the sliding end of the variable resistor RP1 is connected to the non-inverting input of the operational amplifier U7.

6. The intelligent lubrication system for gantry cranes according to claim 4, characterized in that, A filter circuit is also provided between the output terminal of the operational amplifier U7 and the second input terminal of the main control unit. The filter circuit includes a resistor R16, a capacitor C3, a resistor R17, a capacitor C4, a resistor R18, an operational amplifier U8, a resistor R19, and a resistor R20. The first end of the resistor R16 is connected to the output terminal of the operational amplifier U7, and the second end of the resistor R16 is grounded through the capacitor C3. The second end of the resistor R16 is connected to the first end of the capacitor C4, and the second end of the capacitor C4 is grounded through the resistor R18. The second end of the capacitor C4 is connected to the non-inverting input terminal of the operational amplifier U8, and the inverting input terminal of the operational amplifier U8 is grounded through the resistor R19. The output terminal of the operational amplifier U8 is connected to the inverting input terminal of the operational amplifier U8 through the resistor R20, and the output terminal of the operational amplifier U8 is connected to the second end of the resistor R16 through the resistor R17. The output terminal of the operational amplifier U8 is connected to the second input terminal of the main control unit.

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