CN1081326C - Laser on-line testing and checking apparatus for rubber element outline - Google Patents

Abstract

The present invention relates to a laser on-line detector for the outline of a rubber component. A laser beam is used as a probe, and diffuse reflection light spots formed on the surface of a detected object by the irradiation of the laser beam are used as sensing signals. An optical image-forming principle is used for converging collected diffuse reflection light to an electrical coupling device CCD to realize photoelectric conversion. When incident light moves along the surface of the detected object, an imaging point moves correspondingly, and a standard curve is obtained on a standard thickness board according to the magnitude of image drift to work out accurate a thickness value and a width value. The present invention can be widely used for the real-time measurement of the thickness, the width and the outline of components in rubber industry.

Description

Laser on-line detection device for the contour of rubber parts

The present invention relates to the measurement of length, thickness and similar linear dimensions, and especially relates to laser detection technology.

There are many methods for online thickness measurement, such as eddy current method, capacitance method, X-ray diffraction method, X-ray contrast method, β-ray transmission method, α-ray transmission method, ultrasonic method, microwave method, laser scanning method, Laser detector displacement method. Among these on-line thickness measurement methods, except for laser thickness measurement methods, other methods have disadvantages such as low precision, easy drift, poor linearity, complicated equipment, some rays are harmful to human body, and large measurement errors after the half-life of radioactive sources. See Attachment 1 for details

Principle Range Accuracy Resolution advantage shortcoming Eddy current ＜10mm (1～3)% (0.3～1)％ non-contact oil resistance The accuracy is not high and easy to drift capacitance 200um (0.5～1)％ 0.01um  Non-contact high precision High environmental requirements X-ray diffraction 0.1～1um (0.2～1)％ 1% non contact Linear difference equipment is complex X-ray contrast 1～100mm 1% 0.1% Non-contact fast Rays are harmful to the human body beta ray transmission 6～100mm (0.2～0.75)％ 0.1% Non-contact wide range The radiation is harmful to the human body, and the error is large after the half-life of the radioactive source gamma ray transmission ＞100mm 1% Non-contact wide range and strong penetrating ability The radiation is harmful to the human body, and the error is large after the half-life of the radioactive source Ultrasound 1～100mm (0.1～1)％ non contact Media uniformity affects accuracy microwave 0.1～6mm 1% 0.08 non contact   High environmental requirements laser scanning several meters 0.6% 0.2% Non-contact wide range   Scan linear difference Laser detector displacement Microns to several meters 0.1% 0.02% High resolution and high precision Wide dynamic range Protective measures should be taken for complex optical components of equipment

There is a patent No. 91102933 titled "Laser Microcomputer Online Length Measurement Method and Device", which discloses a method that utilizes the high coherence of the laser to form interference fringes in the measurement area, and accumulates the number of pulses and equidistant fringes generated when the moving body passes. The length of the moving body passing through the measuring point can be obtained. This invention uses laser interference fringes to measure the length of an object online. It uses a He-Ne tube gas laser with a wavelength of 6328nm. It uses a photomultiplier tube as a detection element, and the output signal is analog. It is suitable for the measurement of metals and non-metals on the production line. length.

The object of the present invention is to provide a laser on-line detection device for the outline of rubber parts with good measurement resolution, wide application range, fast response speed and high precision.

The working principle of the present invention is: use the laser beam as a mechanical probe during contact measurement, use the diffuse reflection spot formed by the laser beam on the surface of the measured part as the sensing signal, and use the principle of optical imaging to converge the collected diffuse reflection light to the On the charge-coupled device CCD, photoelectric conversion is realized. When the incident light moves with the surface of the measured object, the imaging point moves correspondingly according to a certain rule. According to the size of the image movement, the standard thickness plate obtained by the national metrology department is used Standard curve to convert accurate thickness and width values.

Fig. 1 is a structural block diagram of the present invention;

Figure 2 is a mechanical scanning structure diagram; in the figure:

1. Left vertical plate; 2. Upper ball screw; 3. Ball head lever; 4. Upper rolling guide; 5. Upper laser measuring head; 6. Standard block; 7. Lower laser measuring head; 8. Lower rolling guide ;9, lower ball screw; 10, synchronous pulley; 11, synchronous belt; 12, right vertical plate; 13, motor base; 14, stepping motor; 1, photoelectric switch; 1~2, travel switch; 1~3, solenoid valve; 1~4, pressure reducing valve filter.

Figure 3 is a signal processing and current loop circuit;

Fig. 4 is a CCD driving circuit diagram;

Fig. 5 is a computer interface board block diagram;

Figure 6 is a flow chart of the system software.

The overall structure of the present invention is as described in accompanying drawing 1, mainly by laser light source, photoelectric reception, computer data collection, processing and high-speed data communication, several major parts such as measuring head mechanical scanning drive.

1. Laser light source: the present invention adopts a red light semiconductor laser with a wavelength of 670nm, and uses a collimating lens and a focusing lens to improve the beam quality; automatic power control is adopted in the design of the laser power supply, that is, the photoelectric detection inside the semiconductor laser is used The current signal proportional to the output power output by the diode is controlled by negative feedback, so that the output power of the laser is stable at ±1% at room temperature, so as to overcome the fluctuation of light intensity caused by temperature and other factors and improve the measurement accuracy.

2. Optical signal reception: The diffuse reflection formed by the laser irradiating the surface of the object enters the imaging lens. The relative aperture of the imaging lens is 1:1.2 and the focal length is 50mm. In order to prevent the influence of water vapor and dust, the measuring head adopts a fully enclosed structure. Coated glass and high-pressure gas air curtain are installed in front of the lens to protect the lens.

3. Photoelectric conversion (reception): CCD charge-coupled device used in photoelectric detection elements: ① Number of pixels: 2048; pixel size: 13um×13um; operating frequency: 5M; dynamic range: 7500:1; peak wavelength: 700nm ;② Number of pixels: 5340; Pixel size: 7um×7um; Working frequency: 5MHZ;

CCD drive and signal processing: main vibration frequency: 8MHZ; scanning frequency: (2 ~ 4) MHZ optional; integration time: (2.2 ~ 4) ms optional. Signal processing adopts odd and even signal compounding and amplification; low-pass filtering; peak signal integration; floating threshold comparison; photoelectric isolation output and other measures, which greatly improves the measurement accuracy and enhances the anti-interference ability.

4. Mechanical scanning: Since the maximum moving speed of the measured tread is 250mm/s, the transmission time of each tread (3 meters) is 12 seconds. The driving device is shown in Figure 2. It adopts a gate-shaped structure, and the stepper motor 14 passes through the synchronous pulley. 16 and synchronous belt 11 drive the upper and lower ball screws 2 and 8 to rotate, and then drive the measuring head mounted on the rolling slider 6 to move bidirectionally along the guide rail through the ball screw nuts 2 and 8 and the ball head lever 3, and the upper and lower ball screws are controlled by the computer. 1. The lower measuring head moves back and forth continuously. Since a single motor is used to drive the upper and lower measuring heads simultaneously to ensure the accuracy of the measurement position, the operating frequency is high and the mechanical moment of inertia is large. It is difficult for ordinary stepping motor drivers to meet the requirements. The present invention uses New IGBT high-frequency, high-voltage, constant-current, chopper driver, small size, light weight, large high-frequency drive torque, high efficiency, low power consumption, in order to prevent the motor from running out of control and collide with the precise positioning of the measuring head and width, the motor drive signal adopts The photoelectric switch and the mechanical limit switch are two-stage linkage mode. When the switch operates, the drive signal is cut off in time. If the mechanical limit switch operates, the limit switch can be controlled by the computer to reset the relay action and reverse the manual departure from the protection position.

5. Width measurement: the speed of the stepper motor used in the present invention is variable, the highest drive frequency is 6K, and the conversion rate of the CCD is as mentioned above, and different parameters are selected according to the resolution and precision requirements of the system. When the scattered light of an object with a certain width gathers on the CCD, there are corresponding multiple electrical signals, so that a certain number of electrical signals corresponds to a certain width.

6. Signal processing and transmission:

Since the electrical signal output by the photoelectric conversion device is relatively weak and has poor anti-interference ability, it must be processed on a certain circuit before it can become an effective signal, and this signal is generated as a detection device in the foreground. There is a certain distance from the main computer. In the industrial field environment, the present invention transmits the signal generated by the CCD to the interface circuit of the main computer in the form of a current loop after certain processing, so that the rubber thickness signal is actually transmitted to the main computer. The computer completes the signal conversion and reception.

The CCD driving circuit of the present invention is shown in accompanying drawing 4, and its circuit is that the crystal oscillator start-up circuit connects the frequency division circuit by two, then connects to the frequency division circuit by four, then connects to the voltage conversion circuit, and connects to the CCD hour hand signal pulse; wherein the frequency division circuit Also connected to the graded frequency division circuit, connected to the CCD frame signal circuit, connected to the voltage conversion circuit, connected to the CCD frame signal pulse.

Accompanying drawing 3 is signal processing and current loop circuit:

The line from the CCD is connected to the CCD even signal sampling circuit and the CCD odd signal sampling circuit. Both circuits are connected to the CCD signal composite circuit, and connected to the peak value circuit and sample signal circuit, then connected to the signal comparison circuit, and then connected to the pulse The output shaping circuit is finally connected to the current loop output circuit.

7. Computer interface circuit: see accompanying drawing 5, its structure is: Parallel interface circuit, motor control circuit, signal counter circuit connects with the system bus of host computer through address bus and data bus, clock circuit then provides motor control and signal counting circuit required clock signal. The switching output and motor control signal provided by the parallel port are output through optocoupler isolation.

The measurement signal is sent to the signal counter after being processed by the signal processing circuit through the isolated input.

This interface circuit completes the control of the host computer to the detection device of the foreground, such as the switch of each signal power supply, the control of the mechanical scanning drive device, and collects the signal transmitted from the foreground in the form of a current loop. This acquisition actually completes the thickness signal of the main computer. collection.

8. Data communication:

The upper and lower microcomputer control structure is adopted, and the three production lines are controlled and measured by three lower computers. The computer in the general control room is used as the upper computer in addition to the measurement of standard samples. The measurement data of the lower computer can be transmitted to the upper computer for related display. Processing, storage, printing, etc. The data transmission distance between the control room and each production line is about 100 meters. The computer uses the photoelectric isolation RS-485 industrial standard serial interface to transmit data. The transmission rate is 36.8Kb/s. The data communication volume is large, the transmission speed is fast, and the interference ability is strong.

9. Control computer:

The computer in the main control room and the computer in the production line adopt the upper and lower computer control structure.

The computer software flowchart of the present invention is shown in accompanying drawing 6.

After booting, the system automatically loads the control program.

After the program starts to execute, it first displays Chinese characters and initializes the input module so that the system can display prompt information and the user can input various operating parameters, and then conduct a self-test of the system. The self-test can find software and some hardware faults. After the self-test is correct, the system Start to set the interrupt vectors required by the software and transfer the default initial setting parameters of the system. After the setting is completed, when the corresponding interrupt occurs, the corresponding interrupt service program can be called to process. At this point, the software enters the key scanning program. If a key is pressed, the software will enter the command table query module according to the corresponding key value, and execute the corresponding function module according to the key value.

System reset: clear all parameters and buffer data, and restore the initial setting value of the system;

System self-inspection: find the system failure point;

Parameter setting: set tire type, measurement method, operator and other data;

Manual measurement: you can manually measure raw data such as single point, multi-point, upper tread, lower tread, etc.;

Automatic measurement: according to the set parameters, automatically scan and measure, and automatically display, store, and alarm for out-of-tolerance, etc.

Data processing: display the real-time tread data of each shift; print the required record data.

System calibration: to calibrate the measurement accuracy;

Default command: Ignore if not a normal command, and clear it from the command value sequence.

After the execution of the above functional modules is completed, they all return to the key scanning state in order to execute the next command of the user.

If it is found to be an exit command during key scanning, after the current working state is saved, the interrupt vector of the system is restored to the state before the system software is transferred, and the program is exited.

10. Standard calibration and dust removal gas path

The transmission drum drives the standard block to move up and down by 40mm through a precision screw rod and a nut. The drum scale is 0.01mm per grid, 100 grids per circle, and the movement error is not greater than ±0.05mm. 2～3) Kg/cm ² , high-pressure gas passes through the delivery pipeline to form a 60° conical air curtain in front of the laser and imaging window of the measuring head to prevent dust and dirt pollution.

11. Data processing method:

A. Measurement method: Since the rubber parts will fluctuate up and down during the moving process, the present invention adopts the upper and lower double optical path compensation method for measurement. See accompanying drawing 4, D=Do+D up+D down

B. Error Correction:

1). Static error: Calibrate with a standard plate, measure the reference Do first each time, when the reference Do has a △D change, the measurement also has a △D change, but △Di remains unchanged.

2). Nonlinear correction: Two methods are used according to the needs

Broken line method: According to the object image displacement curve, set standard plates with different thicknesses to measure the Dpn value. Correction coefficient Kn=standard plate thickness Lpn/(Dpn-Do), store Dpn and Kn in the computer, and take the corresponding Kn correction according to the value range of Di, that is, Di=Kpn up×Di up+KpnT×Di down+Do .

Curve fitting: According to the object image displacement curve, set standard plates of different thicknesses to measure the Dpn value, and use the curve fitting algorithm to calculate the standard fitting curve. Measure the thickness of the point.

3). Dynamic correction:

Since the diffuse reflection signal of the rubber part is very weak, the unevenness of the surface and the special shape will cause the detection signal to change or even cause the signal to be lost. Correction.

When in use, the device of the present invention is installed in the middle or last position of the rubber parts production line, the steel wire pressing and grinding production line, and is used for the measurement of the intermediate process or the final product of the parts, providing intuitive and reliable measurement data for production. During measurement, computer control The high-speed stepper motor driver drives the upper and lower signal measuring heads to scan back and forth synchronously along the width direction of the component through two ball screws. The upper and lower measuring heads are respectively equipped with a laser light source, an imaging lens, a drive for a charge-coupled device, and a measurement processing circuit. Using the differential measurement of the upper and lower measurement signals can effectively overcome the influence of the up and down jitter on the thickness during the moving process of the part. The measurement circuit amplifies the thickness signal, compares the variable threshold, reshape and buffers, and after photoelectric isolation, it is sent to the computer for further processing. Data processing, display, storage, printing.

The device of the present invention has been applied in the truck tire factory of Shanghai Rubber Group Co., Ltd. The truck tire factory of Shanghai Rubber Tire Co., Ltd. is the largest manufacturer of steel wire radial tires in China. It has the most advanced production equipment in China, with an annual output of 1 million tires and an output value of 1 billion, this device has been installed in the standard die room, two imported production lines and one domestic production line, and has been actually used. Get very good results. Main Specifications:

1. Real-time detection of the width and thickness of the production line components, and display the profile and data. And adopt the upper and lower computer structure to process, display, store and print the data.

2. The maximum width of the tested part is <700mm, the static error of width measurement is <±0.2mm, and the dynamic error is <±1mm.

3. The thickness range of the tested part is 0 ~ 30mm, and the measurement error is <±0.2mm.

4. The moving speed of the tested part is less than 15m/min, and the scanning head speed is more than 60mm/s.

The invention can be widely used in the real-time measurement of the thickness, width and contour of parts in the rubber industry. It has the characteristics of non-contact measurement, no surface damage, no environmental pollution, strong anti-interference ability, high precision, and data acquisition and processing functions. Important equipment for product quality control in the industry production line.

Example:

1. The laser light source adopts a red light semiconductor laser with a wavelength of 670nm, the relative aperture of the imaging lens is 1:1.2, and the focal length is 50mm. The photoelectric detection element uses a CCD charge-coupled device: ①The number of pixels is 2048; the pixel size: 13um×13um; the working frequency: 20MHZ; dynamic range: 7500:1; peak wavelength: 700nm; the maximum moving speed of the tested tread is 250mm/s, each tread is 3 meters long, and the transmission time is 12 seconds; the computer adopts photoelectric isolation RS-485 industry standard serial interface Transmission data, the transmission rate is 36.8Kb/s; the standard block moves up and down 40mm, the drum scale is 0.01mm per grid, 100 grids per circle, and the movement error is not greater than ±0.005mm. The dust removal air path adopts a filter pressure reducing valve to adjust the output air pressure ( 2～3) Kg/cm ² , the high-pressure gas forms a 60° key-shaped gas band in front of the laser imaging window of the measuring head through the delivery pipeline.

2. The photoelectric detection element uses Toshiba TCD1500C. Pixel size: 7um×7um; working frequency: 5MHZ, the rest is the same as example 1, the resolution and measurement range of the system can be doubled.

Claims (8)

1. A laser on-line detection device for the outline of rubber parts, including a measurement head of a charge-coupled device CCD with a laser source and a front imaging lens, a driving part that drives the measurement head, and a laser source, a charge-coupled device CCD, and a driving part An electrically connected control and data processing unit, characterized in that: the measuring head is also provided with a signal processing unit electrically connected to the charge-coupled device CCD, said measuring head is an upper measuring head (5) and a lower measuring head (7) , the upper and lower measuring heads (5, 7) are placed on both sides of the moving rubber part to be tested, and are respectively connected to the interface circuit and the driving part, wherein, 1.1 The laser source is a red light semiconductor laser with a collimating lens and a focusing lens sequentially arranged on the output optical path, and an output power negative feedback device is installed in the input circuit of the said laser, 1.2 The signal processing unit is a CCD even signal sampling circuit and a CCD odd signal sampling circuit. The input end of the CCD odd signal sampling circuit is connected to the charge-coupled device CCD, the output end is connected to the CCD signal compound circuit, and the input end of the peak value circuit and the sampling signal circuit is connected to the CCD signal compound circuit. Connection, the output terminal is connected with the current loop output circuit after the pulse output shaping circuit, 1.3 The interface circuit is a parallel interface circuit, a motor control circuit, and a signal counter circuit, which are connected to the system bus of the integrated industrial control workstation through address lines and data lines. Connection, the output terminal of the motor control circuit is connected with the isolated output circuit connected with the stepper motor power supply of the driving part, and the signal isolated input circuit connected with the current loop output circuit in the signal processing unit is connected with the clock circuit after the signal processing circuit Connect the signal counter circuit together, the clock circuit is connected with the motor control circuit, 1.4 The driving parts are the upper ball screw (2) and the lower ball screw on the frame formed by the left vertical plate (1), the right vertical plate (12), the upper rolling guide rail (4) and the lower rolling guide rail (8). (9) and stepper motor (14), said upper and lower rolling guide rails (4, 8) are equipped with upper and lower measuring heads (5, 7) that are rolled in contact with it, and said upper and lower ball wires Bar (2,9) is connected with upper and lower measuring head (5,7) through ball head driving lever (3), and said stepper motor (14) is connected with upper and lower ball screw ( 2,9) winding. 2. The device according to claim 1, characterized in that the upper and lower measuring heads (5, 7) are cylindrical closed bodies, and coated glass and high-pressure gas curtains are placed at the measuring ends. 3. The device according to claim 1, characterized in that the relative aperture of the front imaging lens of the CCD is 1:1.2, and the focal length is 50 mm. 4. The device according to claim 1, characterized in that the drive circuit of the charge-coupled device (CCD) is that the input terminal of the two-frequency division circuit is connected to the crystal oscillator start-up circuit, and the output terminal is connected to the four-frequency division circuit and the multi-stage frequency division circuit. The input terminal of the voltage conversion circuit is connected with a four-frequency division circuit, the output terminal is connected with a CCD clock signal pulse, the input terminal of the CCD frame signal circuit is connected with a multi-level frequency division circuit, and the output terminal is connected with a CCD frame signal pulse after the voltage conversion circuit. 5. The device according to claim 1, characterized in that the connection between the integrated industrial control workstation and the upper microcomputer, the stepper motor power supply of the drive components, and the current loop output circuit in the signal processing unit is constituted as a photoelectric isolation coupling. 6. The device according to claim 1, characterized in that paired photoelectric switches (1-1) are distributed on the upper rolling guide rail (4) and the upper measuring head (5). 7. The device according to claim 1, characterized in that the left and right vertical plates (1, 12) are provided with travel switches (1-2) matched with the upper measuring head (5). 8. The device according to claim 1, characterized in that the pressure reducing valve filter (1-4) and the electromagnetic valve (1-3) matched with it are arranged on the left vertical plate (1). The outlets of the valves (1-3) are connected to the high-pressure gas curtain generators at the ends of the upper and lower measuring heads (5, 7) through pipelines.

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