Automatic water meter cover screwing device and method thereof

Abstract

The invention discloses an automatic water meter cover screwing device and method, and belongs to the technical field of automatic assembly.The method comprises the steps that S1, a positioning and feeding unit is arranged, and a motor, a speed reducer, a torque sensor and a gripper are installed in series; s2, three-point centering clamping is conducted on the shell through a V-shaped block and a lateral air cylinder; s3, the gripper descends, abrupt change is monitored through low-speed reverse rotation to judge a tooth entering point, and forward rotation is conducted after the zero point is recorded; s4, constant-speed screwing-in is conducted, the rotating rigidity is calculated through torque data, and a sealing starting point is recognized; and S5, continuously rotating to set an increment angle by taking the starting point as a reference, and completing fixed-compression-amount screwing. According to the invention, no matter how the friction force of the thread fluctuates, the compression thickness of the sealing ring of each water meter is strictly locked by a physical geometrical relationship, so that the sealing reliability of the product is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automatic assembly, in particular to an automatic water meter cover tightening device and method thereof. BACKGROUND

[0002] Water meter cover tightening refers to generating torque by means of tightening equipment of an assembly station to overcome friction of a threaded pair and a sealing assembly, and through threaded connection, the cover is screwed into the housing according to the designed depth and the sealing compression is completed, which is a precise assembly process. The principle is to use the thrust of the rotary drive mechanism and the vertical feed mechanism to screw the cover into the housing from the top of the positioning and push it to the set tightening position. The sealing ring is compressed between the cover and the housing along with the cover.

[0003] In order to ensure product quality, a plurality of sensors are usually installed on the tightening equipment to detect the tightening process state detection data in real time. The purpose of the detection is usually to ensure the sealing safety of the water meter. Under the influence of the machining environment, thread tolerance, surface roughness and material hardness, the tightening process may be prone to torque fluctuation, inconsistent sealing compression, loose teeth or false tightening, etc. In the prior art, detection data is obtained after tightening operation, and quality is judged according to the detection data. However, in actual situations, there is a lot of mechanical transmission noise in the detection data, such as gear meshing friction and some data that have little effect on the sealing compression state, such as the background friction that increases linearly with the increase of the screwing depth. If the quality is directly judged according to the detection data, the sealing starting point may not be accurately identified, and there may be a large product sealing failure risk. SUMMARY

[0004] The purpose of the present application is to provide an automatic water meter cover tightening device and method to solve the problems in the background art. The technical solution of the present application is as follows: An automatic water meter cover tightening method, comprising: S1, a positioning platform, a vertical feed unit and a rotary drive and sensing unit are provided. The rotary drive and sensing unit is installed on the vertical feed unit, and is connected in sequence from top to bottom with a rotary servo motor, a precision planetary reducer, a dynamic torque sensor and a three-jaw pneumatic gripper. The dynamic torque sensor is connected in series between the output end of the precision planetary reducer and the three-jaw pneumatic gripper. S2, the water meter housing is pressed on the V-shaped positioning block of the positioning platform, and three-point centering clamping is formed by a lateral clamping cylinder; S3, the three-jaw pneumatic gripper is controlled to descend, the rotary servo motor is controlled to rotate in reverse at low speed, and the vertical position feedback data of the vertical feed unit is monitored in real time. When vertical drop or current surge is monitored, it is determined that the thread entry point is reached, the reverse rotation is stopped and the zero point is recorded, and the rotation is switched to forward. S4. Control the forward constant speed screwing in, collect data through the dynamic torque sensor, calculate the differential rate of change of torque with respect to angle to obtain instantaneous rotational stiffness, and identify the sealing start point; S5. Using the sealing starting point as a reference, control the rotary servo motor to continue rotating by the set incremental angle to complete the constant compression tightening.

[0005] Preferably, the process of identifying the sealing start point in step S4 includes: S4.1 Perform statistical analysis on the torque data collected during the screw-in stage, and calculate the standard deviation of the instantaneous rotational stiffness data to quantify the random vibration noise level of the mechanical transmission chain during operation. S4.2 Perform linear regression on the data of the spiraling phase to extract the natural growth rate of the background torque; S4.3 Perform dynamic gradient compensation calculation, subtract the natural growth rate of the background torque from the instantaneous rotational stiffness to obtain the net sealing stiffness. When the net sealing stiffness continuously shows positive abrupt changes and the value exceeds the sensitivity coefficient set based on the random vibration noise level, it is determined to be the sealing start point.

[0006] Preferably, step S5 is followed by: S6. Obtain the final peak torque and total rotation angle at the moment of tightening and stopping; S7. Check whether the final peak torque is within the qualified torque window, and at the same time check whether the incremental angle from the sealing start point to the end point is within the qualified angle window. Only when both parameters meet the window requirements at the same time is the tightening qualified.

[0007] An automated water meter cover tightening device includes: Cast iron base with T-slots machined on the surface; The positioning platform is set on the cast iron base and includes a V-shaped positioning block fixed to the center of the cast iron base and a lateral clamping cylinder located on the opposite side of the geometric center of the V-shaped positioning block. The vertical feed unit includes a column vertically fixed to the rear of the cast iron base, a linear guide rail disposed on the front surface of the column, a lifting slide plate moving along the linear guide rail, and a lifting servo motor and a ball screw driving the lifting slide plate to rise and fall. The rotary drive and sensing unit, mounted on the lifting slide plate, includes a rotary servo motor, a precision planetary reducer, a dynamic torque sensor, and a three-jaw pneumatic gripper.

[0008] Preferably, the dynamic torque sensor is equipped with or integrated with a gas-electric hybrid rotary slip ring, which includes a conductive loop and a rotary gas path channel for transmitting an external gas source to the three-jaw pneumatic gripper below.

[0009] Preferably, the three-jaw pneumatic gripper is connected with the dynamic torque sensor through a gripper mounting seat, a circular positioning stop is arranged between the connecting surface of the dynamic torque sensor and the gripper mounting seat with H7 fitting accuracy, and a radial fine adjustment jackscrew is arranged on the side surface of the gripper mounting seat.

[0010] Preferably, the reduction ratio of the precision planetary reducer is set to 10:1, and a polyurethane gasket is embedded in the inner side of the claw of the three-jaw pneumatic gripper.

[0011] Preferably, the end of the piston rod of the lateral clamping cylinder is connected with a circular arc-shaped pressing block, and the included angle of the V-shaped positioning block is designed to be 120 degrees.

[0012] Compared with the prior art, the present application has the following improvements and advantages: 1. The present scheme identifies the sealing starting point by introducing the second-order physical quantity instantaneous rotational stiffness, and performs incremental angle control based on the sealing starting point, effectively solving the problem that single torque control cannot guarantee the consistency of sealing compression amount. Through subtraction operation, the friction resistance component linearly accumulated with the increase of the rotation depth is dynamically stripped, so that the pure sealing stiffness reflecting the contact characteristics of the sealing ring is obtained. When the system detects that the net sealing stiffness appears a significant positive mutation, it can accurately determine the moment when the sealing ring starts to contact the metal end face, and then switch to angle control. This method ensures that the sealing ring compression thickness of each water meter is strictly locked by physical geometric relationship regardless of the fluctuation of thread friction force, significantly improving the sealing reliability of the product; 2. The present scheme introduces a low-speed reverse rotation cooperation Z-axis floating monitoring tooth searching step before rotation, effectively solving the problem that the automatic equipment is prone to thread misalignment and forced rotation. The present scheme requires that the final peak torque must be within the qualified torque window and the incremental angle from the sealing starting point to the end point must be within the qualified angle window when the tightening is completed. If the angle is qualified but the torque is low, the system can identify that the sealing ring is missing or the material is too soft; if the torque is qualified but the angle is small, the system can identify that the thread is slipping or foreign matter is stuck. This logic interlocking mechanism realizes the ultimate judgment of the tightening quality, ensuring that the offline product has a certain physical performance; 3. This solution connects a dynamic torque sensor in series between the output of a precision planetary reducer and a three-jaw pneumatic gripper, and integrates a pneumatic-electric hybrid rotary slip ring inside the sensor. This effectively improves the accuracy of the measurement data. The layout of this solution allows the sensor to directly sense the end load, reducing interference within the reducer. At the same time, the cableless design of the pneumatic-electric hybrid rotary slip ring cuts off the parasitic interference of external air tube stiffness on weak torque changes, ensuring that the system can capture weak physical signal changes during tooth drop and sealing contact, providing a clean data foundation for the operation of high-precision algorithms. Attached Figure Description

[0013] The present invention will be further explained below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the overall external structure of the device; Figure 2 This is a schematic diagram of the connection structure between the lifting servo motor and the rotary servo motor. Figure 3 This is a schematic diagram of the cast iron base structure; Figure 4 This is a schematic diagram of the process flow of the method of the present invention.

[0014] In the diagram: 100, cast iron base; 110, V-shaped positioning block; 120, side clamping cylinder; 200, column; 210, lifting servo motor; 220, ball screw; 230, linear guide rail; 240, lifting slide plate; 310, rotary servo motor; 320, precision planetary reducer; 330, dynamic torque sensor; 340, gripper mounting base; 350, three-jaw pneumatic gripper. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Example 1

[0016] Please see Figures 1-4 This invention provides an automated water meter cover tightening method, comprising: S1. Set up a positioning platform, a vertical feed unit, and a rotary drive and sensing unit; the rotary drive and sensing unit is installed on the vertical feed unit and is connected from top to bottom to a rotary servo motor 310, a precision planetary reducer 320, a dynamic torque sensor 330, and a three-jaw pneumatic gripper 350. The dynamic torque sensor 330 is connected in series between the output end of the precision planetary reducer 320 and the three-jaw pneumatic gripper 350. S2. Press the water meter housing onto the V-shaped positioning block 110 of the positioning platform, and form a three-point centering clamp by the lateral clamping cylinder 120. S3. Control the three-jaw pneumatic gripper 350 to descend, control the rotary servo motor 310 to rotate in the reverse direction at low speed and monitor the vertical position feedback data of the vertical feed unit in real time; when a vertical drop or current change is detected, it is determined to be the thread entry point, the reverse rotation is stopped and the zero point is recorded, and the forward rotation is switched. S4. Control the forward constant speed screwing in, collect data through dynamic torque sensor 330, calculate the differential rate of change of torque with respect to angle to obtain instantaneous rotational stiffness, and identify the sealing start point. S5. Using the sealing start point as a reference, control the rotary servo motor 310 to continue rotating by the set incremental angle to complete the constant compression tightening.

[0017] In this embodiment, the automated water meter cover tightening method addresses the shortcomings of existing technologies, such as difficulty in accurately controlling the sealing compression amount and the tendency for misaligned threads or false tightening, by proposing an operation process based on multi-dimensional sensing and precision control.

[0018] This method relies on a specific hardware architecture. The positioning platform serves as the operational foundation, establishing the workpiece's spatial reference through a V-shaped positioning block 110 and a lateral clamping cylinder 120 (specifically, standard cylinders from brands such as SMC or Festo can be used). The vertical feed unit, specifically a ball screw 220 driven by a servo motor, is responsible for precise Z-axis feeding. The rotary drive and sensing unit is the core actuator, where a dynamic torque sensor 330 (either from brands such as HBM or NCTE) is specifically connected in series between the reducer and the gripper. This layout allows the sensor to directly sense the end-load, reducing interference from gear meshing friction within the reducer on the measurement data, thereby obtaining a high signal-to-noise ratio raw torque signal.

[0019] During the thread-finding phase (S2 to S3), the method utilizes the natural drop characteristic generated by the physical structure when the starting ends of the threads cross each other. A controller, such as a Siemens PLC or Beckhoff IPC, instructs the rotary servo motor 310 to reverse at low speed, while closely monitoring the position deviation of the servo motor's current feedback or encoder feedback in the vertical feed unit. When the three-jaw pneumatic gripper 350 experiences a slight vertical displacement due to the thread crossing, the system immediately detects this mechanical abrupt change and locks it at a physical zero point. To ensure that the physical drop occurs, the servo motor controlling the vertical feed unit is set to torque-limiting mode or soft-floating mode during this phase. In this mode, the axial holding force output by the lifting servo motor 210 is set by the no-load automatic calibration program and is slightly less than the sum of the gravity and friction of the slide plate and gripper assembly, so that the three-jaw pneumatic gripper 350 is in a microgravity suspension state. When the starting ends of the threads cross each other, at the moment the end face support is lost, the gravity component will drive the gripper assembly to produce a physical falling displacement that can be detected by the encoder; In this mode, the Z-axis output torque only maintains the gripper's gravity balance and a slight downward preload, allowing the Z-axis to generate passive axial displacement under the action of the axial component force of thread misalignment, which is then keenly detected by the encoder.

[0020] This process transforms the uncertain thread phase into a definite control origin, effectively avoiding the risk of thread damage that may be caused by traditional forced screwing, and providing a safety guarantee for subsequent high-speed screwing.

[0021] Before calculating the differential rate of change, the system prioritizes smoothing the raw torque data by using a moving average filtering algorithm or a low-pass filtering algorithm. For example, a moving average filter with a window size of 5 to 10 sampling points is used to filter out high-frequency electromagnetic noise and mechanical vibration interference, ensuring the convergence and stability of subsequent differential calculations.

[0022] During the tightening phase from S4 to S5, the method no longer relies solely on the torque threshold but introduces the second-order physical quantity of instantaneous rotational stiffness. By calculating the differential of torque with respect to angle in real time, the system can perceive changes in the stiffness of the mechanical connection. Upon identifying a sudden change in stiffness caused by the contact face of the sealing ring, and after recognizing the sealing initiation point, the system switches to angle-based incremental control. Since the compression deformation of the sealing ring is geometrically linearly related to the rotation angle, controlling the incremental angle essentially directly locks the compression thickness of the sealing ring. This control strategy overcomes the influence of fluctuations in the thread friction coefficient on the tightening quality, ensuring consistent sealing compression for each water meter, thereby guaranteeing the long-term sealing reliability of the product.

[0023] The process for identifying the seal initiation point in step S4 includes: S4.1 Perform statistical analysis on the torque data collected during the screw-in stage, and calculate the standard deviation of the instantaneous rotational stiffness data to quantify the random vibration noise level of the mechanical transmission chain during operation. S4.2 Perform linear regression on the data of the spiraling phase to extract the natural growth rate of the background torque; S4.3 Perform dynamic gradient compensation calculation, subtract the natural growth rate of the background torque from the instantaneous rotational stiffness to obtain the net sealing stiffness. When the net sealing stiffness continuously shows positive abrupt changes and the value exceeds the sensitivity coefficient set based on the random vibration noise level, it is determined to be the sealing start point.

[0024] In this embodiment, the process of identifying the sealing start point is refined into a dynamic gradient compensation algorithm, which aims to accurately extract the weak signal of the sealing ring contact from complex mechanical friction noise.

[0025] In step S4.1, the controller performs statistical processing on the data from the free-screwing stage, where the threads are engaged but the seals have not yet made contact. The system collects a continuous range of torque data, calculates its arithmetic mean to quantify the underlying frictional force of the current workpiece assembly, i.e., the system resistance background value, and simultaneously calculates the standard deviation of the instantaneous rotational stiffness data. This step quantifies the random vibration and noise level of the mechanical transmission chain during operation; it completes the fingerprint extraction of the current working state and equipment operation status, and establishes a dynamic benchmark for subsequent signal discrimination.

[0026] In step S4.2, considering that the contact area between threads increases or there is a slight interference as the insertion depth increases, the frictional torque often exhibits a linear increasing trend. The system performs linear regression analysis on the buffered data sequence to extract the slope of torque as the angle increases, i.e., the natural growth rate of background torque. This parameter characterizes the rate of change of resistance caused solely by mechanical structural factors.

[0027] The specific calculation process is as follows: Step 1, the system extracts the torque data sequence before the seal ring contacts during the screw-in stage. With the corresponding angle data sequence The specific cut-off range is 10% to 80% of the total stroke from the start of forward screwing in to the theoretical sealing contact point preset based on the workpiece dimension chain, in order to avoid the influence of starting inertia and nonlinear effects before contact; Step 2, establish linear equations The data sequence is fitted using the least squares method; in step three, the slope of the fitted line is extracted as the natural growth rate of the background torque. , namely background linear stiffness, which quantifies the torque increment caused by friction of the threaded pair per unit rotation angle; In step S4.3, the system performs the core dynamic gradient compensation calculation. The controller calculates the current instantaneous rotational stiffness in real time and subtracts the aforementioned natural growth rate of the background torque from it, thereby eliminating the interference from thread friction and obtaining a pure net sealing stiffness that reflects the sealing contact characteristics. Specifically, the calculation logic of the net sealing stiffness follows the formula: in, Represents net sealing stiffness. This represents the instantaneous rotational stiffness calculated at the current sampling moment, which is the differential value of the torque with respect to the angle after filtering. Represents the natural growth rate of the background torque extracted in step S4.2, a constant; this operation aims to eliminate the thread friction resistance component that accumulates linearly with increasing insertion depth in real time.

[0028] This computational model logically constructs a virtual pure stiffness observer, which eliminates the linear friction stiffness components caused by thread tolerance fit and lubrication conditions in real time, thus ensuring the net sealing stiffness output by the system. It is sensitive only to the elastic compression characteristics of the sealing ring, thereby achieving physical-level isolation and identification of sealing contact events; Meanwhile, the system uses the random vibration noise level obtained in S4.1 to construct an adaptive threshold and sensitivity coefficient; in addition, for sealing ring materials with different Shore hardness grades, the sensitivity coefficient can be stored as an adjustable parameter in the system formula.

[0029] Sensitivity coefficient The computational logic is defined as follows: ,in The standard deviation calculated in step S4.1, i.e., the random vibration noise level, This is the signal-to-noise ratio factor, typically ranging from 3 to 6, used to ensure that the trigger signal is significantly distinguishable from background mechanical noise; For softer sealing materials, the sensitivity threshold should be appropriately reduced to accommodate their gentler stiffness ramp-up curve; for harder materials, the threshold should be increased to prevent false triggering.

[0030] The system only confirms the sealing start point when the net sealing stiffness not only undergoes a positive abrupt change, but the magnitude of the change is significantly higher than the background noise level. This algorithm strips away the interference of basic friction, deep cumulative friction, and random vibration, enabling the system to accurately capture the moment when the sealing ring contacts the metal end face, even under conditions of large workpiece machining errors or inconsistent lubrication conditions.

[0031] The steps following S5 include: S6. Obtain the final peak torque and total rotation angle at the moment of tightening and stopping; S7. Check whether the final peak torque is within the qualified torque window, and at the same time check whether the incremental angle from the sealing start point to the end point is within the qualified angle window. Only when both parameters meet the window requirements at the same time is the tightening qualified.

[0032] In this embodiment, the process following step S5 establishes a two-dimensional quality verification mechanism for the final determination of the tightening result.

[0033] In steps S6 and S7, the system does not stop at the completion of the action but enters the quality logic verification stage. The controller reads the final position feedback from the servo motor encoder and the peak data feedback from the dynamic torque sensor 330. The system sets two independent qualification windows for torque and angle. The final peak torque reflects the tightness of the tightened connection and the sum of mechanical resistance, while the incremental angle, from the sealing start point to the stop point, directly corresponds to the physical compression of the sealing ring.

[0034] This dual-parameter simultaneous satisfaction judgment logic has clear fault diagnosis significance. If the monitored angle data is within the qualified range, but the torque data is below the lower limit, the system can infer that the sealing ring is missing, lacking compression reaction force, or the sealing ring material is too soft. Conversely, if the torque data has reached the qualified range, but the incremental angle is much smaller than the set lower limit, the system infers that the thread is stripped, misaligned, or jammed by foreign objects, resulting in a falsely high torque without actual tightening. Through this logical interlock, this method effectively eliminates hidden defects such as false tightening or missing parts, ensuring that every product leaving the production line has definite physical properties.

[0035] Example 2: Please see Figures 1-3 An automated water meter cover tightening device includes: The cast iron base is 100mm, with T-slots machined on its surface; The positioning platform is set on the cast iron base 100 and includes a V-shaped positioning block 110 fixed to the center of the cast iron base 100 and a lateral clamping cylinder 120 located on the opposite side of the geometric center of the V-shaped positioning block 110. The vertical feed unit includes a column 200 vertically fixed to the rear of the cast iron base 100, a linear guide rail 230 disposed on the front surface of the column 200, a lifting slide plate 240 moving along the linear guide rail 230, and a lifting servo motor 210 and a ball screw 220 for driving the lifting slide plate 240 to rise and fall. The rotary drive and sensing unit, mounted on the lifting slide plate 240, includes a rotary servo motor 310, a precision planetary reducer 320, a dynamic torque sensor 330, and a three-jaw pneumatic gripper 350.

[0036] In this embodiment, the automatic water meter cover tightening device serves as the physical carrier for executing the aforementioned process, and its structural rigidity and motion accuracy directly determine the effectiveness of the algorithm.

[0037] The cast iron base 100, preferably made of HT250 or higher grade cast iron, provides a high shock absorption and thermal stability mounting base through natural aging treatment. The T-slots on its surface provide a uniform reference surface for all components, ensuring assembly accuracy.

[0038] It should be noted that the base material is not limited to cast iron, but can also be marble, welded steel structure or polymer mineral casting, as long as it has sufficient mass to provide torsional stiffness and shock absorption performance, it falls within the protection scope of this invention. The positioning platform is designed to eliminate the influence of tightening reaction force on the workpiece posture. The V-shaped positioning block 110 utilizes the principle of geometric self-centering to adapt to water meter housings of different diameters, and together with the lateral clamping cylinder 120 on the opposite side, it constructs a stable triangular mechanical constraint on the horizontal plane. This rigid clamping ensures that the water meter housing will not move at all when subjected to high torque tightening, guaranteeing the uniqueness of the reference for angle measurement.

[0039] The vertical feed unit, via the column 200, can be constructed using a combination of thick-walled square steel welded or cast parts and linear guide rails 230, such as those from THK or HIWIN brands, to create a high-rigidity Z-axis channel. The lifting slide 240 moves along the guide rail under the drive of a servo motor. Its high-rigidity guiding structure effectively resists the lateral overturning torque generated by the rotating unit during start-up and stop, ensuring that the rotation axis is always perpendicular to the workpiece plane—a prerequisite for achieving precision thread insertion.

[0040] The rotary drive and sensing unit integrates power output and signal acquisition functions. The rotary servo motor 310 provides a controllable speed and torque source, while the precision planetary gearbox 320 converts the motor's high speed into high torque output and matches the load inertia. The key lies in the integration of the dynamic torque sensor 330 and the three-jaw pneumatic gripper 350. This end-sensing structure reduces signal attenuation in intermediate transmission links, enabling the device to sense subtle physical changes, such as tooth drops or sealing contacts.

[0041] The dynamic torque sensor 330 is equipped with or integrated with a pneumatic-electric hybrid rotary slip ring, which includes a conductive loop and a rotary air passage for transmitting external air to the three-jaw pneumatic gripper 350 below.

[0042] In this embodiment, the dynamic torque sensor 330 is given the function of medium transmission, which solves the final transmission problem of the rotary actuator.

[0043] During automated tightening, the gripper below requires compressed air to open and close, while the rotating unit may need to rotate continuously for multiple turns. If an external cable chain is used, it is prone to tangling or even breakage, and the drag force of the chain will be directly superimposed on the torque sensor, resulting in serious parasitic measurement errors. Therefore, the sensor integrates or is connected in combination with a pneumatic-electric hybrid rotary slip ring.

[0044] The slip ring structure includes a precision conductive loop for transmitting the sensor's own electrical signals, and a rotating air passage for transmitting compressed air. An external static air source is connected through the slip ring's stator-side interface, transmitted to the rotor side via an internal sealed flow channel, and then directly to the three-jaw pneumatic gripper 350 below. This cableless design not only eliminates the physical risk of pipe entanglement, but more importantly, it completely cuts off the interference of external pipe stiffness on torque measurement, ensuring that every Newton-meter value output by the sensor accurately reflects the current tightening condition.

[0045] In terms of specific hardware implementation, there are two main ways to integrate the pneumatic-electric hybrid rotary slip ring inside the dynamic torque sensor 330: The first option is to use a through-hole type dynamic torque sensor, and to coaxially nest an independent micro pneumatic-electric slip ring unit inside its hollow shaft, and rigidly connect the stator and rotor of both respectively; The second option is to directly use a modular torque sensor product that has integrated slip ring function on the market.

[0046] The three-jaw pneumatic gripper 350 is connected to the dynamic torque sensor 330 via the gripper mounting base 340. A circular positioning stop with an H7 fit accuracy is provided between the connection surfaces of the gripper mounting base 340 and the dynamic torque sensor 330. Radial fine-tuning set screws are provided on the side of the gripper mounting base 340.

[0047] In this embodiment, the connection structure between the three-jaw pneumatic gripper 350 and the sensor has been precisely designed to achieve excellent coaxiality.

[0048] The gripper mounting base 340 serves as an intermediate connector, with its upper surface connected to the sensor flange. To ensure strict alignment between the rotation center and the gripper's geometric center, the connecting surface is designed with a circular locating stop with an H7 fit precision. This high-precision mechanical fit forcibly constrains the radial degree of freedom, achieving basic passive alignment.

[0049] More importantly, the mounting base features evenly distributed radial fine-tuning screws on its sides. During assembly and debugging, technicians can monitor the rotational runout of the gripper using a dial indicator and fine-tune the gripper's position radially with the screws at the micrometer level, thereby eliminating eccentricity caused by the accumulation of machining errors and assembly clearances. This structural design eliminates the centrifugal force caused by eccentricity during rotation, preventing periodic vibration noise caused by eccentricity from coupling into the torque signal, thus providing a clean physical signal source for the algorithm. The connection method is not limited to flange bolt connections; any rigid connection structure that can achieve the above-mentioned stop positioning and fine-tuning functions, such as clamp-type or expansion sleeve-type, can be used as an implementation method.

[0050] The reduction ratio of the precision planetary reducer 320 is set to 10:1, and the inner side of the claws of the three-jaw pneumatic gripper 350 is inlaid with polyurethane gaskets.

[0051] In this embodiment, the specific parameter settings of the precision planetary reducer 320 and the three-jaw pneumatic gripper 350 reflect a deep adaptation to the process object.

[0052] The reduction ratio of the precision planetary gearbox 320 is selected as 10:1. This speed ratio is not chosen arbitrarily, but to find a balance between the rated speed of the servo motor and the process speed required for tightening. At the same time, the square effect of the reduction ratio is used to optimize the load inertia ratio, making the system more agile in its dynamic response to load changes.

[0053] The 350 three-jaw pneumatic gripper features polyurethane gaskets embedded on the inner sides of its jaws. Polyurethane material boasts high wear resistance and a high coefficient of friction, while also possessing a certain elastic modulus. When the gripper clamps the water meter cover, the gaskets undergo slight elastic deformation, tightly conforming to the outer surface of the cover. This soft-contact design provides sufficient static friction to transmit the tightening torque while preventing damage or scratches to the cover's appearance caused by direct metal jaw clamping, achieving a balance between high torque transmission and non-destructive operation.

[0054] Because the high coefficient of friction of the polyurethane gasket avoids slippage during the tightening process, it ensures that the encoder angle data of the rotary servo motor 310 can accurately reflect the actual screw-in angle of the cover. This is the physical prerequisite for achieving high-precision angle incremental control. The piston rod end of the lateral clamping cylinder 120 is connected to an arc-shaped pressure block, and the included angle of the V-shaped positioning block 110 is designed to be 120 degrees.

[0055] In this embodiment, the lateral clamping cylinder 120 and the V-shaped positioning block 110 constitute a highly adaptable clamping unit.

[0056] The included angle of the V-shaped positioning block 110 is specifically designed to be 120 degrees. This angle conforms to the geometric principle of three points defining a circle, enabling it to adapt to water meter housings with different diameter tolerances and always keeping the workpiece center on the Y-axis symmetry plane. The lateral clamping cylinder 120, as the power actuator, has an arc-shaped pressure block connected to the end of its piston rod. The concave curvature of this pressure block is designed to fit the outer diameter of a standard water meter housing. When the cylinder actuates, the arc-shaped pressure block pushes the workpiece tightly against the two inclined surfaces of the V-shaped block, forming a stable three-point contact. This layout not only achieves rapid clamping but also utilizes the stability of a triangle to resist the huge reverse torque generated during tightening, preventing the workpiece from slipping or rotating within the fixture and ensuring that all tightening torque is effectively applied to the threaded pair.

[0057] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for tightening an automated water meter cover, characterized in that, include: S1. A positioning platform, a vertical feed unit, and a rotary drive and sensing unit are set up. The rotary drive and sensing unit is installed on the vertical feed unit and is connected in sequence from top to bottom to a rotary servo motor (310), a precision planetary reducer (320), a dynamic torque sensor (330), and a three-jaw pneumatic gripper (350). The dynamic torque sensor (330) is connected in series between the output end of the precision planetary reducer (320) and the three-jaw pneumatic gripper (350). S2. Press the water meter housing onto the V-shaped positioning block (110) of the positioning platform, and form a three-point centering clamp by the lateral clamping cylinder (120); S3. Control the three-jaw pneumatic gripper (350) to descend, control the rotary servo motor (310) to rotate in the reverse direction at low speed and monitor the vertical position feedback data of the vertical feed unit in real time; when a vertical drop or current change is detected, it is determined to be the thread entry point, stop the reverse rotation and record the zero point, and switch to forward rotation. S4. Control the forward constant speed screwing in, collect data through the dynamic torque sensor (330), calculate the differential rate of change of torque with respect to angle to obtain instantaneous rotational stiffness, and identify the sealing start point; S5. Using the sealing starting point as a reference, control the rotary servo motor (310) to continue rotating by the set incremental angle to complete the constant compression tightening.

2. The method for tightening an automated water meter cover according to claim 1, characterized in that, The process of identifying the sealing start point in step S4 includes: S4.1 Perform statistical analysis on the torque data collected during the screw-in stage, and calculate the standard deviation of the instantaneous rotational stiffness data to quantify the random vibration noise level of the mechanical transmission chain during operation. S4.2 Perform linear regression on the data of the spiraling phase to extract the natural growth rate of the background torque; S4.3 Perform dynamic gradient compensation calculation, subtract the natural growth rate of the background torque from the instantaneous rotational stiffness to obtain the net sealing stiffness. When the net sealing stiffness continuously shows positive abrupt changes and the value exceeds the sensitivity coefficient set based on the random vibration noise level, it is determined to be the sealing start point.

3. The method for tightening an automated water meter cover according to claim 1, characterized in that, Step S5 is followed by: S6. Obtain the final peak torque and total rotation angle at the moment of tightening and stopping; S7. Check whether the final peak torque is within the qualified torque window, and at the same time check whether the incremental angle from the sealing start point to the end point is within the qualified angle window. Only when both parameters meet the window requirements at the same time is the tightening qualified.

4. An automated water meter cover tightening device, used to implement the automated water meter cover tightening method according to any one of claims 1 to 3, characterized in that, include: Cast iron base (100) with T-slots machined on the surface; The positioning platform is set on the cast iron base (100) and includes a V-shaped positioning block (110) fixed to the center of the cast iron base (100) and a lateral clamping cylinder (120) located on the opposite side of the geometric center of the V-shaped positioning block (110). The vertical feed unit includes a column (200) vertically fixed behind the cast iron base (100), a linear guide rail (230) disposed on the front surface of the column (200), a lifting slide plate (240) moving along the linear guide rail (230), and a lifting servo motor (210) and a ball screw (220) for driving the lifting slide plate (240) to rise and fall. The rotary drive and sensing unit is mounted on the lifting slide plate (240) and includes a rotary servo motor (310), a precision planetary reducer (320), a dynamic torque sensor (330), and a three-jaw pneumatic gripper (350). A control unit, which is electrically connected to the vertical feed unit and the rotary drive and sensing unit respectively, is used to control each unit to perform the method as described in any one of claims 1 to 3.

5. The automatic water meter cover tightening device according to claim 4, characterized in that, The dynamic torque sensor (330) is equipped with or integrated with a pneumatic-electric hybrid rotary slip ring, which includes a conductive loop and a rotating air passage for transmitting an external air source to the three-jaw pneumatic gripper (350) below.

6. The automated water meter cover tightening device according to claim 4, characterized in that, The three-jaw pneumatic gripper (350) is connected to the dynamic torque sensor (330) through a gripper mounting base (340). A circular positioning stop with an H7 fit accuracy is provided between the connection surfaces of the gripper mounting base (340) and the dynamic torque sensor (330). A radial fine-adjustment set screw is provided on the side of the gripper mounting base (340).

7. The automatic water meter cover tightening device according to claim 4, characterized in that, The reduction ratio of the precision planetary reducer (320) is set to 10:1, and the inner side of the claw of the three-jaw pneumatic gripper (350) is inlaid with a polyurethane gasket.

8. The automated water meter cover tightening device according to claim 4, characterized in that, The piston rod end of the lateral clamping cylinder (120) is connected to an arc-shaped pressure block, and the included angle of the V-shaped positioning block (110) is designed to be 120 degrees.

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