Excavator filling visualization system and control method

Abstract

The invention discloses an excavator filling visualization system and a control method, belongs to the field of engineering machinery, and aims to solve the problems that an ultra-large mining excavator is high in oil filling manpower dependence, low in accuracy and poor in observation environment. According to the system, a complete machine controller serves as a core and is connected with a liquid level sensor, a centralized filling platform camera, an instrument, a breathing lamp, a buzzer and the like, and the instrument and a video monitor communicate with the controller through a CAN communication line; the control method comprises the following three stages: when the platform descends, automatically lightening the maintenance lamp, and jumping to a monitoring picture and a filling information interface; during filling, the sensor transmits data in real time, the instrument dynamically displays the liquid level percentage, the breathing lamp develops color according to liquid level grading, and acousto-optic warning is triggered; after the platform ascends in place, the equipment state is automatically reset. Extra personnel are not needed, the detection precision and the filling efficiency are improved, meanwhile, a foundation is laid for remotely controlling filling of the excavator, and the method is suitable for the oil filling scene of the ultra-large mining excavator.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery, specifically to a visual system and control method for refueling excavators, which is particularly suitable for refueling scenarios of ultra-large mining excavators. It can realize real-time monitoring, precise control and safety warning of the refueling process, and improve refueling efficiency and equipment operation and maintenance safety. Background Technology

[0002] As core equipment in mining operations, ultra-large mining excavators require frequent replenishment of various oils such as hydraulic oil, fuel oil, engine oil, and gear oil during daily operation and maintenance. Currently, the industry generally adopts a centralized refueling method—that is, reserving multiple oil refueling ports on a manually lifting refueling platform to achieve refueling of multiple types of oils for the entire machine at the same location; however, the existing technical solution has the following problems: 1. Information asymmetry and reliance on manpower: The status of the refueling platform cannot be directly observed from the cab. An additional observer is required to be on duty at the liquid level observation port of each oil tank. When the liquid level reaches a specific mark, the observer is reminded to stop the operation by voice or signal. In addition, the observation ports of different oil types are scattered, and the observer needs to frequently change positions when switching refueling types, which is cumbersome.

[0003] 2. Harsh observation environment: Some liquid level observation ports are limited by the equipment structure, with small space and lack of lighting, resulting in poor visibility and making it easy for observers to misjudge the liquid level, increasing the risk of filling errors.

[0004] 3. Low accuracy and efficiency of refueling: Refueling personnel rely entirely on the prompts of observers to determine when to stop, lacking local warning devices on the refueling platform; without personnel cooperation, two extreme situations are likely to occur: first, overfilling, resulting in excessive pressure in the pipeline, affecting the normal operation of the hydraulic, fuel and other systems of the whole machine, and even causing malfunctions such as seal damage and oil leakage; second, insufficient refueling, requiring repeated shutdowns for replenishment, significantly reducing the operating efficiency of the equipment. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a visual system and control method for excavator refueling. By integrating technologies such as the machine controller, liquid level sensor, video monitoring, and audible and visual warnings, a two-way information interaction and automatic control system between the "cabin" and the refueling platform is constructed to achieve the following objectives: 1. No additional observers are required. Liquid level data is automatically collected and processed through sensors and controllers and displayed in real time in the cockpit, reducing labor costs; 2. Establish real-time video monitoring of the refueling platform from the cockpit to solve the problem of information asymmetry; 3. Design a multi-level sound and light warning mechanism to ensure that the refueling personnel accurately grasp the timing of stopping and avoid exceeding or falling short of limits; 4. Improve refueling efficiency and equipment safety, laying the foundation for remote-controlled refueling operations of mining excavators in the future.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an excavator refueling visualization system, comprising: an instrument, a video monitor, a machine controller, a centralized refueling platform camera, a liquid level sensor, a maintenance light, a breathing light, a buzzer, a centralized refueling switch, a centralized refueling lifting valve, a centralized refueling port detection switch, and a centralized refueling platform upper limit proximity switch; The liquid level sensor, centralized filling switch, centralized filling port detection switch, and centralized filling platform upper limit proximity switch are connected to the input port of the whole machine controller; The centralized filling lifting valve, inspection light, breathing light, and buzzer are connected to the output port of the whole machine controller; The centralized refueling platform camera is connected to a video monitor. The communication ports of the instrument and video monitor are connected to the communication port of the overall controller via a CAN communication line.

[0007] Furthermore, the overall controller is the core logic operation component, which receives signals from the liquid level sensor, the centralized filling switch, the centralized filling port detection switch, and the upper limit proximity switch of the centralized filling platform. After logic operation, the signals are output to the centralized filling lifting valve, instruments, video monitor, inspection light, breathing light, and buzzer.

[0008] Furthermore, the instruments, video monitor, and centralized refueling switch are located in the cockpit; the refueling platform camera is located in front of the refueling platform so that it can observe the status of the refueling port; the inspection light and buzzer are located on one side of the refueling platform; the breathing light and centralized refueling port detection switch are located on the refueling port; the centralized refueling platform upper limit proximity switch is located on the other side of the refueling platform; the liquid level sensor is installed in the fuel tank; and all the above components are connected through electrical control circuits.

[0009] Furthermore, the display status of the breathing light is set according to the signal transmitted from the liquid level sensor to the whole machine controller: red light is on when the liquid level is below 10%; yellow light is on when the liquid level is between 10% and 30%; and white light is on when the liquid level is above 30%.

[0010] Furthermore, the instrument's filling information interface includes: hydraulic oil information, fuel information, engine oil information, gear oil information, lubricating grease information, and cooling water information. Each type of information includes liquid level, pressure, and temperature data.

[0011] Furthermore, the buzzer's prompts include: a "Please note, refilling is descending" prompt when the refilling platform descends; a "Please note, refilling is ascending" prompt when the refilling platform ascends; and a "Refilling is complete" prompt when refilling is finished.

[0012] A refueling control method for an excavator, implemented based on the aforementioned excavator refueling visualization system, the control method comprising: (1) When the whole machine controller detects the upper limit proximity switch signal of the centralized filling platform, press the centralized filling switch, and the whole machine controller outputs a logic signal to the centralized filling lifting valve to control the filling platform to descend. At the same time, the instrument and the buzzer of the filling platform issue a reminder. (2) When the whole machine controller does not receive the upper limit proximity switch signal of the centralized refueling platform, it outputs a signal to the video monitor and the inspection light. The video monitor jumps out of the camera display interface of the centralized refueling platform, the inspection light is lit, and the instrument interface jumps to the refueling information interface. (3) When the filling gun is inserted into the corresponding filling port, the whole machine controller controls the instrument to display the dynamic liquid level percentage of the corresponding oil according to the signal of the centralized filling port detection switch, and the breathing light flashes; (4) The liquid level sensor collects the liquid level signal of the oil tank in real time and transmits it to the whole machine controller. After processing, the whole machine controller outputs the signal to the instrument, and the instrument updates the real-time dynamic liquid level percentage. (5) When the filler reaches the specified mark, the breathing light will switch to constant light and the buzzer will sound a warning sound; after the filler gun is pulled out, the instrument interface will return to the filler information interface. (6) Press the centralized filling switch, and the whole machine controller outputs a logic signal to the centralized filling lifting valve to control the filling platform to rise. The buzzer sounds a reminder. When the whole machine controller receives the signal of the upper limit proximity switch of the centralized filling platform, the video monitor closes the display interface of the centralized filling platform camera, the maintenance light turns off, and the instrument interface returns to the desktop.

[0013] Furthermore, in (2), the centralized refueling platform camera display interface that pops up on the video monitor can provide real-time feedback on the working status of the refueling platform. The driver can communicate with the refueling personnel in real time through this interface and handle any abnormal situations during the refueling process in a timely manner.

[0014] Furthermore, in (3), the whole machine controller accurately matches the corresponding oil type by identifying different signals of the centralized filling port detection switch. Each filling port corresponds to a unique detection switch signal code, ensuring that the liquid level percentage displayed by the instrument is completely consistent with the current filling oil.

[0015] Furthermore, in (4), the signal acquisition frequency of the liquid level sensor is real-time continuous acquisition, and the processing delay of the whole machine controller for the signal does not exceed 100ms, ensuring that the deviation between the liquid level data displayed by the instrument and the actual liquid level in the tank does not exceed ±1%, thus meeting the high-precision filling requirements.

[0016] Furthermore, during the descent of the refueling platform, if the controller does not receive feedback that the signal of the upper limit proximity switch of the centralized refueling platform has disappeared after a set time, the buzzer will emit a continuous fault warning sound, and at the same time, the instrument interface will display a "Refueling platform descent abnormal" prompt box to remind the operator to check the platform lifting mechanism to prevent mechanical failure from causing safety hazards. If the controller does not receive feedback from the upper limit proximity switch of the centralized refueling platform after a set time during the refueling platform's ascent, the buzzer will emit a continuous fault warning sound, and the instrument interface will display a "Refueling Platform Ascent Abnormal" prompt box, reminding the operator to check the platform lifting mechanism to prevent mechanical failure from causing safety hazards.

[0017] Compared with existing oil filling technologies for ultra-large mining excavators, this invention has the following significant advantages: 1) Reduce labor costs and solve pain points in the observation environment. Innovation: Automatic data collection through liquid level sensors + cockpit video monitoring replaces traditional manual observation; Effect: No additional observation personnel are required, avoiding the need for observation personnel to stand guard in narrow, unlit observation ports, reducing labor costs while eliminating the risk of misjudgment caused by harsh environments; 2) Innovation in achieving a closed-loop information system between the cockpit and the refueling platform: CAN bus communication + automatic interface switching to build two-way information interaction; Effect: The driver can view various oil levels, pressures, and temperatures in real time through the instruments without leaving the cockpit, and observe the operating status of the refueling platform through the video monitor, solving the problem of "information asymmetry"; Moreover, the interface automatically switches when the platform is raised or lowered or the refueling status changes, without the need for manual operation, improving convenience; 3) Multi-level audio-visual warnings ensure accurate filling. Innovation: Color-coded breathing light + customized buzzer sounds cover all scenarios from "liquid level range" to "filling status" to "abnormal malfunctions". Effect: Filling personnel can intuitively judge the liquid level by the color of the breathing light (red / yellow / white corresponds to low / medium / high) and distinguish between "platform lifting / lowering" and "filling completion" and "malfunction" by the prompt sounds, avoiding reliance on subjective judgment; and preventing repeated shutdowns caused by excessive or insufficient pipeline pressure due to exceeding limits, reducing equipment failure rate, and improving the accuracy of the filling process and the efficiency of subsequent maintenance. 4) Laying the foundation for remote control and adapting to the trend of intelligent innovation: Full-process automatic control + self-diagnosis of abnormal faults, reducing manual intervention; Effect: The "sensor-controller-actuator" architecture of this system can be directly connected to the remote control system of mining excavators, and the local operation in the cab can be replaced by the remote terminal to realize "unattended" refueling; In addition, in case of abnormal faults (such as platform descent jamming, sensor failure), the system will automatically warn and record fault codes, which will facilitate maintenance personnel to quickly troubleshoot and improve the level of equipment intelligence; 5) Innovations in improving refueling efficiency and equipment safety: The platform lifting and lowering are linked with the refueling preparation and finishing actions, reducing unnecessary waiting time; Effects: The platform automatically lights up and switches the monitoring interface when it descends, and automatically resets after refueling is completed, reducing the overall refueling process time compared to existing technologies; At the same time, it avoids excessive pipeline pressure caused by over-refueling, protects the hydraulic and fuel system seals, extends the service life of the equipment, and reduces maintenance costs. Attached Figure Description

[0018] Figure 1 This is the electrical schematic diagram of the present invention; Figure 2 This is a diagram showing the arrangement of instruments and other components in the cockpit of the present invention; Figure 3 This is a diagram showing the arrangement of components on the platform for this invention. Figure 4 This is a diagram showing the arrangement of the liquid level sensor of the present invention; In the diagram: A1, Instrument; A2, Video Monitor; ECU1, Unit Controller; CAM, Centralized Filling Platform Camera; B1, Liquid Level Sensor; E1, Inspection Light; E2, Breathing Light; P1, Buzzer; S1, Centralized Filling Switch; YK1, Centralized Filling Lifting Valve; BG1, Centralized Filling Port Detection Switch; BG2, Centralized Filling Platform Upper Limit Proximity Switch. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention.

[0021] like Figure 1As shown, an excavator refueling visualization system includes an instrument A1, a video monitor A2, a CAN communication line, a machine controller ECU1, a centralized refueling platform camera CAM, a liquid level sensor B1, an inspection light E1, a breathing light E2, a buzzer P1, a centralized refueling switch S1, a centralized refueling lifting valve YK1, a centralized refueling port detection switch BG1, and a centralized refueling platform upper limit proximity switch BG2. The machine controller ECU1 acts as the core logic processing unit, receiving signals from the liquid level sensor B1, the centralized refueling switch S1, the centralized refueling port detection switch BG1, and the centralized refueling platform upper limit proximity switch BG2. After logic processing, the signals are output to the centralized refueling lifting valve YK1, the instrument A1, the video monitor A2, the inspection light E1, the breathing light E2, and the buzzer P1.

[0022] like Figure 2 As shown, the cockpit is equipped with instrument A1, video monitor A2, and centralized refueling switch S1; Figure 3 As shown, a centralized refueling platform camera (CAM) is located directly in front of the refueling platform. An inspection light (E1) and a buzzer (P1) are configured on the right side. A breathing light (E2) and a centralized refueling port detection switch (BG1) are installed on the refueling port. An upper limit proximity switch (BG2) for the centralized refueling platform is installed on the left side to detect changes in the status of the front sensor plate. Figure 4 As shown, a liquid level sensor B1 is installed on the fuel tank; all components are connected via electrical control circuits, and the instrument A1 and video monitor A2 are connected to the main controller ECU1 via a CAN communication line.

[0023] The YK1 filling lifting valve is an electro-hydraulic filling lifting valve. The filling platform is installed on the excavator via a hydraulic lifting frame. The hydraulic cylinder of the hydraulic lifting frame is connected to the hydraulic equipment through the centralized filling lifting valve YK1. The filling platform is raised and lowered by the filling lifting valve YK1. The filling platform is equipped with filling pipelines for hydraulic oil tank, fuel tank, engine oil tank, gear oil tank, grease tank and coolant tank.

[0024] The ECU1 controller outputs the signal from the B1 level sensor to the breathing light E2 on the filling platform. The breathing light E2 is set on the ECU1 controller according to the level sensor B1 level. When the level is below 10%, it is constantly lit in red; when it is between 10% and 30%, it is constantly lit in yellow; and when the level is above 30%, it is constantly lit in white.

[0025] The instrument A1 filling information interface includes: hydraulic oil information, fuel information, engine oil information, gear oil information, grease and coolant information.

[0026] A refueling control method for an excavator, implemented based on the aforementioned excavator refueling visualization system, includes the following control methods: When the ECU1 of the whole machine detects the signal of the upper limit proximity switch BG2 of the centralized filling platform, the filling platform is in the upper limit position; when the centralized filling switch S1 is pressed, the logic output of the ECU1 of the whole machine is sent to the centralized filling lifting valve YK1, the filling platform descends, and at the same time the instrument A1 and the buzzer P1 of the filling platform emit a "Please note, filling is descending" prompt sound; When the ECU1 controller does not detect the signal from the BG2 upper limit proximity switch of the centralized refueling platform, the inspection light E1 is turned on. The video monitor A2 receives the output signal from the ECU1 controller and exits the display interface of the CAM camera on the centralized refueling platform. The instrument A1 interface jumps to the refueling information interface. When the refueling platform is observed to have descended to the correct position on the video monitor interface, the centralized refueling switch S1 is turned off, and the "Please note, refueling descent" prompt sound of the instrument A1 and the refueling platform buzzer P1 is turned off. When the filling gun is inserted into the corresponding filling port, the whole machine controller will display the corresponding oil level percentage on the instrument A1 according to the signal of the centralized filling port detection switch BG1, and the breathing light E2 will flash white at the same time. As oil is added, the signal from the corresponding level sensor B1 in the oil tank is input to the main controller ECU1. After processing, the main controller ECU1 outputs a signal to the communication port of instrument A1, and the real-time dynamic liquid level percentage of the corresponding oil tank on the instrument A1 interface changes continuously. When the refill reaches the set value, the breathing light E2 will remain constantly white, and at the same time, the instrument A1 and the buzzer P1 of the refilling platform will emit a "refilling complete" prompt sound; when the refilling gun is pulled out, the controller ECU1 loses the signal from the centralized refill port detection switch BG1, and the instrument A1 interface returns to the refilling information interface. When the video monitor A2 confirms that there are no abnormalities, press the centralized filling switch S1. The logic output of the whole machine controller ECU1 is sent to the centralized filling lifting valve YK1, the filling platform rises, and the instrument A1 and the filling platform buzzer P1 emit a "Please note, filling is rising" prompt sound; when it rises to the point that the whole machine controller ECU1 receives the signal of the upper limit proximity switch BG2, the instrument A1 interface returns to the desktop and the inspection light E1 turns off.

[0027] The above-described filling process only applies to hydraulic oil, engine oil, gear oil, grease, and coolant. When adding fuel, the engine must be turned off before the fuel filling operation can be performed.

[0028] If the ECU1 controller does not receive feedback that the signal of the BG2 upper limit proximity switch of the centralized refueling platform has disappeared after a set time during the refueling platform descent, the buzzer P1 will emit a continuous fault warning sound, and at the same time, the instrument A1 interface will pop up a "Refueling platform descent abnormal" prompt box to remind the operator to check the platform lifting mechanism to prevent mechanical failure from causing safety hazards. If the ECU1 controller does not receive feedback from the BG2 signal of the upper limit proximity switch of the centralized refueling platform after a set time during the refueling platform as it rises, the buzzer P1 will emit a continuous fault warning sound. At the same time, the instrument A1 interface will display a "Refueling Platform Rising Abnormal" prompt box, reminding the operator to check the platform lifting mechanism to prevent mechanical failure from causing safety hazards.

[0029] Inside the cab, the liquid level and filling platform status are monitored in real time via instrument A1 and video monitor A2. Signals are simultaneously transmitted to the filling platform, and the breathing light E2 and buzzer P1 alert the filling personnel to take appropriate action at the appropriate time, ensuring that different types of oil are filled to the required level in one go. This improves the accuracy of the filling process, avoiding overfilling, excessive pressure in the pipeline, or the need for repeated shutdowns for filling when insufficient oil is added. This provides a strong guarantee for the efficient maintenance and repair of ultra-large excavating machinery. The control method allows the operator to monitor the filling platform status from the cab via a monitoring screen. In case of special circumstances, timely communication with the filling personnel is possible, laying the foundation for reliable filling of mining excavating machinery with remote control capabilities. Simultaneously, it eliminates the need for additional personnel to visually observe, saving manpower while making the liquid level data visible and accurately reflecting real-time liquid level data.

[0030] The liquid level sensor mentioned above is one of the following: resistive liquid level sensor, capacitive liquid level sensor, or ultrasonic liquid level sensor.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A backhoe fill visualization system, characterized by, The system comprises: an instrument, a video monitor, a whole-machine controller, a centralized refueling platform camera, a liquid level sensor, a maintenance lamp, a breathing lamp, a buzzer, a centralized refueling switch, a centralized refueling lift valve, a centralized refueling port detection switch, and a limit proximity switch on the centralized refueling platform; the liquid level sensor, the centralized refueling switch, the centralized refueling port detection switch, and the limit proximity switch on the centralized refueling platform are connected to the input port of the whole-machine controller; the centralized refueling lift valve, the maintenance lamp, the breathing lamp, and the buzzer are connected to the output port of the whole-machine controller; the centralized refueling platform camera is connected to the video monitor; the communication port of the instrument and the video monitor is connected to the communication port of the whole-machine controller through a CAN communication line.

2. A loader fill visualization system as claimed in claim 1, characterized in that, The whole-machine controller is a core logic operation component, receives signals input by the liquid level sensor, the centralized refueling switch, the centralized refueling port detection switch, and the limit proximity switch on the centralized refueling platform, and outputs the signals to the centralized refueling lift valve, the instrument, the video monitor, the maintenance lamp, the breathing lamp, and the buzzer after logic operation.

3. The excavator refueling visualization system of claim 1, wherein, The instrument, the video monitor, and the centralized refueling switch are arranged in the cockpit; the refueling platform camera is arranged in front of the refueling platform so as to observe the refueling port; the maintenance lamp and the buzzer are arranged on one side of the refueling platform; the breathing lamp and the centralized refueling port detection switch are arranged on the refueling port; the limit proximity switch on the centralized refueling platform is arranged on the other side of the refueling platform; and the liquid level sensor is arranged in the fuel tank. All the components are connected through an electrical control line.

4. The excavator refueling visualization system of claim 1, wherein, The display state of the breathing lamp is set according to the signal transmitted by the liquid level sensor to the whole-machine controller: red constant light when the liquid level is lower than 10%; yellow constant light when the liquid level is between 10% and 30%; and white constant light when the liquid level is higher than 30%.

5. The excavator refueling visualization system of claim 1, wherein, The refueling information interface of the instrument comprises: hydraulic oil information, fuel information, engine oil information, gear oil information, lubricating grease information, and cooling water information, each type of information containing liquid level, pressure, and temperature data.

6. The excavator refueling visualization system of claim 1, wherein, The prompt sound of the buzzer comprises: "please pay attention, refueling is descending" prompt sound when the refueling platform is descending; "please pay attention, refueling is ascending" prompt sound when the refueling platform is ascending; and "refueling is completed" prompt sound when refueling is completed.

7. A method of refueling control of an excavator, characterized by, The control method of the refueling visualization system of the excavator according to claim 1 comprises: (1) when the whole-machine controller detects the limit proximity switch signal on the centralized refueling platform, the centralized refueling switch is pressed, the whole-machine controller outputs a logic signal to the centralized refueling lift valve to control the refueling platform to descend, and the instrument and the refueling platform buzzer issue a prompt; (2) when the whole-machine controller cannot receive the limit proximity switch signal on the centralized refueling platform, the signal is output to the video monitor and the maintenance lamp, the video monitor jumps out of the centralized refueling platform camera display interface, the maintenance lamp is lit, and the instrument interface jumps to the refueling information interface; (3) when the refueling gun is inserted into the corresponding refueling port, the whole-machine controller controls the instrument to display the dynamic liquid level percentage of the corresponding oil according to the signal of the centralized refueling port detection switch, and the breathing lamp flashes. (4) The liquid level sensor collects the oil tank liquid level signal in real time and transmits it to the whole machine controller. The whole machine controller processes the signal and outputs it to the instrument. The instrument updates the real-time dynamic liquid level percentage. (5) When the filling reaches the specified scale, the breathing light switches to constant light, and the buzzer emits a prompt sound. After the filling gun is pulled out, the instrument interface returns to the filling information interface. (6) Press the centralized filling switch. The whole machine controller outputs a logic signal to the centralized filling lifting valve to control the filling platform to rise, and the buzzer emits a reminder. When the whole machine controller receives the centralized filling platform upper limit proximity switch signal, the video monitor closes the centralized filling platform camera display interface, the maintenance light is off, and the instrument interface returns to the desktop.

8. A method of filling control for an excavator according to claim 7, wherein In the (2), the centralized filling platform camera display interface jumped out by the video monitor can real-time feedback the working state of the filling platform. The driver communicates with the filling personnel in real time through the interface and handles the abnormal situation in the filling process in time.

9. The method of claim 7, wherein, In the (3), the whole machine controller accurately matches the corresponding oil type by identifying different signals of the centralized filling port detection switch. Each filling port corresponds to a unique detection switch signal code to ensure that the liquid level percentage displayed by the instrument is completely consistent with the current filling oil.

10. The method of claim 7, wherein, In the (4), the signal collection frequency of the liquid level sensor is real-time continuous collection. The whole machine controller processes the signal with a delay of not more than 100 ms to ensure that the deviation between the liquid level data displayed by the instrument and the actual liquid level of the oil tank is not more than ±1%, meeting the high-precision filling demand.

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