A hydraulic lifting control system for a container transport semi-trailer

Abstract

The present application relates to the technical fields of hydraulic lifting system, and proposes a hydraulic lifting control system of container transport semi-trailer, which comprises a main control unit and an electromagnetic reversing valve control circuit, the electromagnetic reversing valve control circuit comprises an operational amplifier U1, a resistor R25, a switch tube Q2, a resistor R9 and a switch tube Q3, the same phase input end of the operational amplifier U1 is connected with the main control unit, the output end of the operational amplifier U1 is connected with the opposite phase input end of the operational amplifier U1 through the resistor R25, the output end of the operational amplifier U1 is connected with the control end of the switch tube Q2, the first end of the switch tube Q2 is connected with a 24V power supply through the resistor R9, the second end of the switch tube Q2 is grounded, the first end of the switch tube Q2 is connected with the control end of the switch tube Q3, the first end of the switch tube Q3 is connected with the 24V power supply, the second end of the switch tube Q3 is connected with the first end of an electromagnetic reversing valve coil L1, and the second end of the electromagnetic reversing valve coil L1 is grounded, through the above technical scheme, the problem of unstable current of the electromagnetic reversing valve control circuit in the prior art during operation is solved.

Description

Technical Field

[0001] This invention relates to the field of hydraulic lifting system technology, specifically to a hydraulic lifting control system for a container transport semi-trailer. Background Technology

[0002] Currently, after ordinary container semi-trailers transport containers to designated locations, most are lifted and unloaded together by hydraulic lifting platforms. However, this is problematic because lifting platforms occupy too much space, resulting in low factory utilization, difficulty in unloading, and equipment malfunctions that can cause the entire transport chain to halt. With the development and advancement of automation technology, container semi-trailers with a rear-tipping function have been developed to solve the problem of unloading difficulties. These rear-tipping container semi-trailers are essentially semi-trailer chassis with an added hydraulic lifting mechanism. The engine drives a hydraulic pump via a transmission and power take-off, delivering high-pressure oil through a reversing valve and oil pipes to the lifting hydraulic cylinder. To better control the extension and retraction of the hydraulic cylinder, an electromagnetic reversing valve is used to change the oil circuit, thereby controlling the cylinder's extension and retraction. The control circuit of the existing solenoid directional valve has an unstable current during operation. If the current flowing through the solenoid directional valve is too small, the driving capability is insufficient and the solenoid directional valve cannot start normally. If the current flowing through the solenoid directional valve is too large, the coil temperature in the solenoid directional valve will be too high, which will easily lead to the solenoid directional valve burning out over time. Summary of the Invention

[0003] This invention proposes a hydraulic lifting control system for container semi-trailers, which solves the problem of unstable current in the electromagnetic directional valve control circuit during operation in the prior art.

[0004] The technical solution of the present invention is as follows: A hydraulic lifting control system for a container semi-trailer includes an electromagnetic directional valve for changing the oil circuit, a main control unit, and an electromagnetic directional valve control circuit. The electromagnetic directional valve control circuit is connected to the main control unit. The electromagnetic directional valve control circuit includes resistor R3, operational amplifier U1, resistor R25, resistor R5, switching transistor Q2, resistor R9, relay K1, switching transistor Q3, resistor R8, resistor R6, resistor R4, and operational amplifier U2. The first end of resistor R3 is connected to the first output terminal of the main control unit, and the second end of resistor R3 is connected to the non-inverting input terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to the inverting input terminal of operational amplifier U1 through resistor R25. The output terminal of operational amplifier U1 is connected to the control terminal of switching transistor Q2 through resistor R5. The first end of switching transistor Q2 is connected to a 24V power supply through resistor R9, and the second end of switching transistor Q2 is grounded. The first end of switching transistor Q2 is connected to the control terminal of switching transistor Q3. The first end of switching transistor Q3 is connected to a 24V power supply through the normally closed contact of relay K1. The second end of switching transistor Q3 is connected to the first end of electromagnetic commutator coil L1, and the second end of electromagnetic commutator coil L1 is grounded through resistor R8. The second end of the electromagnetic commutation valve coil L1 is connected to the non-inverting input of the operational amplifier U2. The inverting input of the operational amplifier U2 is grounded through the resistor R6. The output of the operational amplifier U2 is connected to the output of the operational amplifier U2 through the resistor R4. The output of the operational amplifier U2 is connected to the inverting input of the operational amplifier U1.

[0005] Furthermore, the electromagnetic reversing valve control circuit of the present invention also includes a resistor R1, a switching transistor Q1, and an optocoupler U6. The first end of the resistor R1 is connected to the first output terminal of the main control unit, the second end of the resistor R1 is connected to the control terminal of the switching transistor Q1, the first end of the switching transistor Q1 is connected to a 5V power supply, the second end of the switching transistor Q1 is connected to the first input terminal of the optocoupler U6, the second input terminal of the optocoupler U6 is grounded, the first output terminal of the optocoupler U6 is connected to a 5V power supply, and the second output terminal of the optocoupler U6 is connected to the first end of the resistor R3.

[0006] Furthermore, the present invention also includes a current detection circuit, which includes a resistor R11, an operational amplifier U3, resistors R12, R10, R13, an operational amplifier U4, a resistor R15, and a resistor R16. The first end of the resistor R11 is connected to the second end of the electromagnetic commutation valve coil, and the second end of the resistor R11 is connected to the non-inverting input terminal of the operational amplifier U3. The inverting input terminal of the operational amplifier U3 is grounded through the resistor R12. The output terminal of the operational amplifier U3 is connected to the inverting input terminal of the operational amplifier U3 through the resistor R10. The output terminal of the operational amplifier U3 is connected to the inverting input terminal of the operational amplifier U4 through the resistor R13. The non-inverting input terminal of the operational amplifier U4 is connected to a 5V power supply through the resistor R16. The non-inverting input terminal of the operational amplifier U4 is grounded through the resistor R15. The output terminal of the operational amplifier U4 is connected to the first input terminal of the main control unit.

[0007] Furthermore, the present invention also includes a temperature detection circuit, which includes a temperature sensor P1, a resistor R17, an operational amplifier U5, a resistor R19, a variable resistor RP1, a resistor R18, and a resistor R20. The non-inverting input terminal of the operational amplifier U5 is connected to the first terminal of the temperature sensor P1 through the resistor R17, and the second terminal of the temperature sensor P1 is grounded. The inverting input terminal of the operational amplifier U5 is connected to the sliding terminal of the variable resistor RP1. The first terminal of the variable resistor RP1 is connected to a 5V power supply through the resistor R19, and the second terminal of the variable resistor RP1 is grounded. The output terminal of the operational amplifier U5 is connected to the inverting input terminal of the operational amplifier U5 through the resistor R18, and the output terminal of the operational amplifier U5 is connected to the second input terminal of the main control unit through the resistor R20.

[0008] Furthermore, the present invention also includes a protection circuit, which includes resistors R23 and R24, switching transistors Q4 and Q5, light-emitting diodes LED2 and LED3, optocoupler U7, NOT gate U8, and NOT gate U9. The control terminal of switching transistor Q4 is connected to the second output terminal of the main control unit through resistor R23. The first terminal of switching transistor Q4 is connected to the first input terminal of optocoupler U7, and the second terminal of switching transistor Q4 is connected to the anode of light-emitting diode LED2. The cathode of light-emitting diode LED2 is grounded. The control terminal of switching transistor Q5 is connected to the main control unit through resistor R24. The third output terminal of the main control unit is connected as follows: the first terminal of the switching transistor Q5 is connected to the first input terminal of the optocoupler U7; the second terminal of the switching transistor Q5 is connected to the anode of the light-emitting diode LED3; the cathode of the light-emitting diode LED3 is grounded; the second input terminal of the optocoupler U7 is connected to a 5V power supply; the first output terminal of the optocoupler U7 is connected to a 12V power supply; the second output terminal of the optocoupler U7 is connected to the input terminal of the NOT gate U8; the output terminal of the NOT gate U8 is connected to the input terminal of the NOT gate U9; the output terminal of the NOT gate U9 is connected to the first input terminal of the relay K1; and the second input terminal of the relay K1 is grounded.

[0009] The working principle and beneficial effects of this invention are as follows: In this invention, the electromagnetic directional valve control circuit changes the direction of the oil circuit by comparing and controlling the electromagnetic directional valve, thereby realizing the extension and retraction of the hydraulic cylinder.

[0010] Specifically, the working principle of the electromagnetic directional valve control circuit is as follows: When the semi-trailer is unloading, the main control unit outputs a PWM control signal to the non-inverting input of operational amplifier U1. When the PWM control signal is high, the output of operational amplifier U1 is high, switching transistor Q2 is turned on, switching transistor Q3 is turned off, and the electromagnetic directional valve does not operate. When the PWM control signal becomes low, the output of operational amplifier U1 is 0, switching transistor Q2 is turned off, the control terminal of switching transistor Q3 changes from low to high, switching transistor Q3 is turned on, current passes through the electromagnetic directional valve, the valve core of the electromagnetic directional valve is displaced, and hydraulic oil enters the lifting hydraulic cylinder through the electromagnetic directional valve and oil pipe. The hydraulic cylinder extends, thereby realizing the rear tipping function. During this process, if the current flowing through the solenoid commutator coil L1 is too low, the voltage across resistor R8 will be low, causing the voltage at the inverting input terminal of operational amplifier U1 to decrease. Operational amplifier U1 forms a subtraction circuit, which in turn causes the output voltage of operational amplifier U1 to increase, the control current of switching transistor Q2 to increase, and the control current of switching transistor Q3 to increase. Therefore, the current flowing through the solenoid commutator coil L1 increases. Conversely, if the current flowing through the solenoid commutator coil L1 is too high, the voltage across resistor R8 will increase, the voltage at the inverting input terminal of operational amplifier U1 to increase, causing the output voltage of operational amplifier U1 to decrease. This will cause the control current of switching transistor Q2 to decrease, and the control current of switching transistor Q3 to also decrease, thus reducing the increase in the current flowing through the solenoid commutator coil.

[0011] In this invention, the current in the electromagnetic reversing valve coil L1 can be maintained in a relatively stable state, thereby avoiding the problem that the electromagnetic reversing valve cannot start normally due to too small a current in the electromagnetic reversing valve coil L1, or that the electromagnetic reversing valve burns out due to too large a current flowing through the electromagnetic reversing valve coil L1.

[0012] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0013] Figure 1 This is a circuit diagram of the electromagnetic directional valve control circuit in this invention; Figure 2 This is a circuit diagram of the current detection circuit in this invention; Figure 3 This is a circuit diagram of the temperature detection circuit in this invention; Figure 4 This is a circuit diagram of the protection circuit in this invention. Detailed Implementation

[0014] 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.

[0015] Example 1 like Figure 1 As shown, this embodiment proposes a hydraulic lifting control system for a container transport semi-trailer, including an electromagnetic directional valve for changing the oil circuit, a main control unit, and an electromagnetic directional valve control circuit. The electromagnetic directional valve control circuit is connected to the main control unit. The electromagnetic directional valve control circuit includes resistor R3, operational amplifier U1, resistor R25, resistor R5, switching transistor Q2, resistor R9, relay K1, switching transistor Q3, resistor R8, resistor R6, resistor R4, and operational amplifier U2. The first end of resistor R3 is connected to the first output terminal of the main control unit, and the second end of resistor R3 is connected to the non-inverting input terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to the inverting input terminal of operational amplifier U1 through resistor R25. The output terminal of operational amplifier U1 is connected to the non-inverting input terminal of operational amplifier U1 through resistor R25. Resistor R5 is connected to the control terminal of switch Q2. The first terminal of switch Q2 is connected to the 24V power supply through resistor R9. The second terminal of switch Q2 is grounded. The first terminal of switch Q2 is connected to the control terminal of switch Q3. The first terminal of switch Q3 is connected to the 24V power supply through the normally closed contact of relay K1. The second terminal of switch Q3 is connected to the first terminal of electromagnetic commutator coil L1. The second terminal of electromagnetic commutator coil L1 is grounded through resistor R8. The second terminal of electromagnetic commutator coil L1 is connected to the non-inverting input terminal of operational amplifier U2. The inverting input terminal of operational amplifier U2 is grounded through resistor R6. The output terminal of operational amplifier U2 is connected to the output terminal of operational amplifier U2 through resistor R4. The output terminal of operational amplifier U2 is connected to the inverting input terminal of operational amplifier U1.

[0016] A container semi-trailer with a rear-tipping function is constructed by adding a hydraulic lifting mechanism to an existing semi-trailer chassis. The vehicle's engine drives this mechanism to tilt the cargo box at a certain angle for unloading, and the cargo box returns to its original position under its own weight after unloading. The engine drives a hydraulic pump via the transmission and power take-off (PTO), which then supplies hydraulic oil to the lifting hydraulic cylinders through a solenoid directional valve and oil pipes. The solenoid directional valve control circuit changes the direction of the oil flow, thereby controlling the extension and retraction of the hydraulic cylinders.

[0017] Specifically, the working principle of the electromagnetic directional valve control circuit is as follows: When the semi-trailer is unloading, the main control unit outputs a PWM control signal to the non-inverting input of operational amplifier U1. When the PWM control signal is high, the output of operational amplifier U1 is high, switching transistor Q2 is turned on, switching transistor Q3 is turned off, and the electromagnetic directional valve does not operate. When the PWM control signal becomes low, the output of operational amplifier U1 is 0, switching transistor Q2 is turned off, the control terminal of switching transistor Q3 changes from low to high, switching transistor Q3 is turned on, and the current passes through the electromagnetic directional valve coil L1. The valve core of the electromagnetic directional valve is displaced, and the hydraulic oil enters the lifting hydraulic cylinder through the electromagnetic directional valve and the oil pipe. The hydraulic cylinder extends, thereby realizing the rear tilting function. During this process, if the current flowing through the solenoid commutator coil L1 is too low, the voltage across resistor R8 will be low. This voltage will be sent to the non-inverting input of operational amplifier U2, which will form an amplifier circuit. The amplified voltage will then be sent to the inverting input of operational amplifier U1, which will form a subtraction circuit. Due to the decrease in voltage across resistor R8, the voltage at the inverting input of operational amplifier U1 will decrease, leading to an increase in the output voltage of operational amplifier U1. This will increase the current at the control terminal of switching transistor Q2, which in turn will increase the current at the control terminal of switching transistor Q3. Consequently, the current flowing through the solenoid commutator coil L1 will increase. Similarly, if the current flowing through the solenoid commutator coil L1 is too high, the voltage across resistor R8 will increase, leading to an increase in the voltage at the inverting input of operational amplifier U1. This will decrease the output voltage of operational amplifier U1, resulting in a decrease in the control terminal current of switching transistor Q2 and the control terminal current of switching transistor Q3. Consequently, the increase in the current flowing through the solenoid commutator coil L1 will decrease. This maintains the current in the solenoid directional valve coil L1 at a relatively stable state, thus avoiding the problem of the solenoid directional valve burning out due to either insufficient current in the coil L1 or excessive current.

[0018] In this embodiment, an NPN transistor is used as the switch Q2, and an N-channel enhancement-mode MOSFET is used as the switch Q3.

[0019] like Figure 1 As shown, the electromagnetic reversing valve control circuit in this embodiment also includes a resistor R1, a switching transistor Q1, and an optocoupler U6. The first end of the resistor R1 is connected to the first output terminal of the main control unit, the second end of the resistor R1 is connected to the control terminal of the switching transistor Q1, the first end of the switching transistor Q1 is connected to a 5V power supply, the second end of the switching transistor Q1 is connected to the first input terminal of the optocoupler U6, the second input terminal of the optocoupler U6 is grounded, the first output terminal of the optocoupler U6 is connected to a 5V power supply, and the second output terminal of the optocoupler U6 is connected to the first end of the resistor R3.

[0020] During the control of the electromagnetic reversing valve, very strong transient pulse interference is often generated. This interference signal will affect the main control unit and may even directly damage the main control unit. Therefore, in this embodiment, an isolation circuit is added between the main control unit and the resistor R3. The isolation circuit is composed of optocoupler U6, which plays the role of signal isolation. Transistor Q1 is used to improve the driving capability. When the PWM control signal is low, the switching transistor Q1 is turned on and the optocoupler U6 is also turned on. Therefore, the optocoupler U6 outputs a high-level signal. When the PWM control signal is high, the switching transistor Q1 is turned off and the optocoupler U6 is also turned off. The optocoupler U6 outputs a low-level signal.

[0021] like Figure 2 As shown, this embodiment also includes a current detection circuit, which includes resistor R11, operational amplifier U3, resistors R12, R10, R13, operational amplifier U4, resistors R15 and R16. The first end of resistor R11 is connected to the second end of the electromagnetic commutation valve coil, and the second end of resistor R11 is connected to the non-inverting input of operational amplifier U3. The inverting input of operational amplifier U3 is grounded through resistor R12. The output of operational amplifier U3 is connected to the inverting input of operational amplifier U3 through resistor R10. The output of operational amplifier U3 is connected to the inverting input of operational amplifier U4 through resistor R13. The non-inverting input of operational amplifier U4 is connected to a 5V power supply through resistor R16. The non-inverting input of operational amplifier U4 is grounded through resistor R15. The output of operational amplifier U4 is connected to the first input of the main control unit.

[0022] If the current flowing through the solenoid directional valve coil L1 is too high during the self-unloading process of a semi-trailer, it will cause the coil to heat up. Over time, this will affect the service life of the solenoid directional valve and the normal operation of the entire hydraulic lifting mechanism. Therefore, this embodiment uses a current detection circuit to collect the current of the solenoid directional valve coil L1 in real time and send it to the main control unit. If the current of the solenoid directional valve coil L1 exceeds the set value, corresponding measures can be taken.

[0023] Specifically, the current detection circuit works as follows: While the current flows through the electromagnetic commutator coil L1, it also passes through resistor R8, generating a voltage across R8. This voltage changes with the current. Therefore, by measuring the voltage across R8, the magnitude of the current in the electromagnetic commutator coil L1 can be determined. The current through R8 is then applied to the non-inverting input of operational amplifier U3 via resistor R11. Operational amplifier U3 forms an amplifier circuit. Since the sampled voltage is small, it needs to be amplified. The amplified voltage signal is then applied to the inverting input of operational amplifier U4 via resistor R13. Capacitor C9 is used to filter out high-frequency interference. Operational amplifier U4 forms a comparator circuit. The non-inverting input of operational amplifier U4 serves as a reference voltage. When the sampled voltage is lower than the set value, operational amplifier U4 outputs a high-level signal. When the sampled voltage is higher than the set value, operational amplifier U4 outputs a low-level signal and sends it to the main control unit. When the main control unit receives this low-level signal, it indicates that the current flowing through the electromagnetic commutator coil L1 is too high.

[0024] like Figure 3 As shown, this embodiment also includes a temperature detection circuit, which includes a temperature sensor P1, a resistor R17, an operational amplifier U5, a resistor R19, a variable resistor RP1, a resistor R18, and a resistor R20. The non-inverting input terminal of the operational amplifier U5 is connected to the first terminal of the temperature sensor P1 through the resistor R17, and the second terminal of the temperature sensor P1 is grounded. The inverting input terminal of the operational amplifier U5 is connected to the sliding terminal of the variable resistor RP1. The first terminal of the variable resistor RP1 is connected to a 5V power supply through the resistor R19, and the second terminal of the variable resistor RP1 is grounded. The output terminal of the operational amplifier U5 is connected to the inverting input terminal of the operational amplifier U5 through the resistor R18, and the output terminal of the operational amplifier U5 is connected to the second input terminal of the main control unit through the resistor R20.

[0025] If the temperature of the solenoid directional valve coil L1 is too high, it will also affect the normal operation of the solenoid directional valve. In order to ensure the normal operation of the entire hydraulic lifting mechanism, this embodiment uses a temperature detection circuit to monitor the temperature of the solenoid directional valve in real time.

[0026] Temperature sensor P1 is used to detect the temperature signal of the solenoid directional valve and convert the detected temperature signal into an electrical signal, which is output to the non-inverting input of operational amplifier U5. The electrical signal output by temperature sensor P1 is relatively weak and needs to be amplified. Operational amplifier U5 forms an amplification circuit to send the amplified electrical signal to the main control unit. Resistor R20 and capacitor C11 form a low-pass filter circuit to remove interference signals from the amplified electrical signal. Finally, the filtered electrical signal is sent to the main control unit.

[0027] like Figure 4As shown, this embodiment also includes a protection circuit, which includes resistors R23 and R24, switching transistors Q4 and Q5, LED2 and LED3, optocoupler U7, NOT gate U8 and NOT gate U9. The control terminal of switching transistor Q4 is connected to the second output terminal of the main control unit through resistor R23. The first terminal of switching transistor Q4 is connected to the first input terminal of optocoupler U7, and the second terminal of switching transistor Q4 is connected to the anode of LED2. The cathode of LED2 is grounded. The control terminal of switching transistor Q5 is connected to resistor R24 ​​through resistor R25. 4. Connect the third output terminal of the main control unit. Connect the first terminal of the switching transistor Q5 to the first input terminal of the optocoupler U7. Connect the second terminal of the switching transistor Q5 to the anode of the light-emitting diode LED3. The cathode of the light-emitting diode LED3 is grounded. Connect the second input terminal of the optocoupler U7 to a 5V power supply. Connect the first output terminal of the optocoupler U7 to a 12V power supply. Connect the second output terminal of the optocoupler U7 to the input terminal of the NOT gate U8. Connect the output terminal of the NOT gate U8 to the input terminal of the NOT gate U9. Connect the output terminal of the NOT gate U9 to the first input terminal of the relay K1. The second input terminal of the relay K1 is grounded.

[0028] To prevent the current or temperature of the solenoid directional valve coil L1 from becoming too high, this embodiment includes a protection circuit. When the current or temperature of the solenoid directional valve coil L1 becomes too high, the power supply to the solenoid directional valve coil L1 should be immediately disconnected to prevent the solenoid directional valve from burning out.

[0029] When the current in the solenoid directional valve coil L1 exceeds the set value, the main control unit outputs a high-level signal to the control terminal of the switching transistor Q4, turning on Q4 and the optocoupler U7. The optocoupler U7 outputs a high-level signal, which, after being inverted by NOT gates U8 and U9, is applied to the input terminal of relay K1. Relay K1 is energized and its normally closed contact opens, while LED2 illuminates. When the temperature of the solenoid directional valve exceeds the set value, the main control unit sends a high-level signal to the control terminal of the switching transistor Q5, turning on Q5 and the optocoupler U7. Relay K1 is energized and its normally closed contact opens, while LED3 illuminates. This embodiment can disconnect the power supply to the solenoid directional valve coil L1 when the current or temperature is too high, providing protection. Simultaneously, the opening and closing of LEDs LED2 and LED3 can be observed to determine the cause of the normally open contact opening of relay K1.

[0030] 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 hydraulic lifting control system for a container semi-trailer, comprising an electromagnetic directional valve, said electromagnetic directional valve being used to change the oil circuit, characterized in that, It also includes a main control unit and an electromagnetic directional valve control circuit. The electromagnetic directional valve control circuit is connected to the main control unit. The electromagnetic directional valve control circuit includes resistor R3, operational amplifier U1, resistor R25, resistor R5, switching transistor Q2, resistor R9, relay K1, switching transistor Q3, resistor R8, resistor R6, resistor R4, and operational amplifier U2. The first end of resistor R3 is connected to the first output terminal of the main control unit, and the second end of resistor R3 is connected to the non-inverting input terminal of operational amplifier U1. The output terminal of operational amplifier U1 is connected to the inverting input terminal of operational amplifier U1 through resistor R25. The output terminal of operational amplifier U1 is connected to the control terminal of switching transistor Q2 through resistor R5. The first end of switching transistor Q2 is connected to a 24V power supply through resistor R9, and the second end of switching transistor Q2 is grounded. The first end of switching transistor Q2 is connected to the control terminal of switching transistor Q3. The first end of switching transistor Q3 is connected to a 24V power supply through the normally closed contact of relay K1. The second end of switching transistor Q3 is connected to the first end of electromagnetic commutator coil L1, and the second end of electromagnetic commutator coil L1 is grounded through resistor R8. The second end of the electromagnetic commutation valve coil L1 is connected to the non-inverting input terminal of the operational amplifier U2, the inverting input terminal of the operational amplifier U2 is grounded through the resistor R6, the output terminal of the operational amplifier U2 is connected to the inverting input terminal of the operational amplifier U2 through the resistor R4, and the output terminal of the operational amplifier U2 is connected to the inverting input terminal of the operational amplifier U1. The electromagnetic reversing valve control circuit also includes a resistor R1, a switching transistor Q1, and an optocoupler U6. The first end of the resistor R1 is connected to the first output terminal of the main control unit, the second end of the resistor R1 is connected to the control terminal of the switching transistor Q1, the first end of the switching transistor Q1 is connected to a 5V power supply, the second end of the switching transistor Q1 is connected to the first input terminal of the optocoupler U6, the second input terminal of the optocoupler U6 is grounded, the first output terminal of the optocoupler U6 is connected to a 5V power supply, and the second output terminal of the optocoupler U6 is connected to the first end of the resistor R3.

2. The hydraulic lifting control system for a container transport semi-trailer according to claim 1, characterized in that, It also includes a current detection circuit, which comprises resistor R11, operational amplifier U3, resistors R12, R10, R13, operational amplifier U4, resistors R15 and R16. The first end of resistor R11 is connected to the second end of the electromagnetic commutation valve coil, and the second end of resistor R11 is connected to the non-inverting input of operational amplifier U3. The inverting input of operational amplifier U3 is grounded through resistor R12. The output of operational amplifier U3 is connected to the inverting input of operational amplifier U3 through resistor R10. The output of operational amplifier U3 is connected to the inverting input of operational amplifier U4 through resistor R13. The non-inverting input of operational amplifier U4 is connected to a 5V power supply through resistor R16. The non-inverting input of operational amplifier U4 is grounded through resistor R15. The output of operational amplifier U4 is connected to the first input of the main control unit.

3. The hydraulic lifting control system for a container transport semi-trailer according to claim 1, characterized in that, It also includes a temperature detection circuit, which includes a temperature sensor P1, a resistor R17, an operational amplifier U5, a resistor R19, a variable resistor RP1, a resistor R18, and a resistor R20. The non-inverting input terminal of the operational amplifier U5 is connected to the first terminal of the temperature sensor P1 through the resistor R17, and the second terminal of the temperature sensor P1 is grounded. The inverting input terminal of the operational amplifier U5 is connected to the sliding terminal of the variable resistor RP1. The first terminal of the variable resistor RP1 is connected to a 5V power supply through the resistor R19, and the second terminal of the variable resistor RP1 is grounded. The output terminal of the operational amplifier U5 is connected to the inverting input terminal of the operational amplifier U5 through the resistor R18, and the output terminal of the operational amplifier U5 is connected to the second input terminal of the main control unit through the resistor R20.

4. The hydraulic lifting control system for a container transport semi-trailer according to claim 1, characterized in that, It also includes a protection circuit, which comprises resistors R23 and R24, switching transistors Q4 and Q5, LED2 and LED3, optocoupler U7, NOT gate U8 and NOT gate U9. The control terminal of switching transistor Q4 is connected to the second output terminal of the main control unit through resistor R23. The first terminal of switching transistor Q4 is connected to the first input terminal of optocoupler U7. The second terminal of switching transistor Q4 is connected to the anode of LED2. The cathode of LED2 is grounded. The control terminal of switching transistor Q5 is connected to the main control unit through resistor R24. The third output terminal of the unit, the first terminal of the switching transistor Q5 is connected to the first input terminal of the optocoupler U7, the second terminal of the switching transistor Q5 is connected to the anode of the light-emitting diode LED3, the cathode of the light-emitting diode LED3 is grounded, the second input terminal of the optocoupler U7 is connected to a 5V power supply, the first output terminal of the optocoupler U7 is connected to a 12V power supply, the second output terminal of the optocoupler U7 is connected to the input terminal of the NOT gate U8, the output terminal of the NOT gate U8 is connected to the input terminal of the NOT gate U9, the output terminal of the NOT gate U9 is connected to the first input terminal of the relay K1, and the second input terminal of the relay K1 is grounded.

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