In industries involving paper testing, such as papermaking and cigarette industry, high-precision measurement of paper tensile and compression is required. The traditional method to improve the measurement accuracy of force value only improves the accuracy of the sensor and the number of digits of the A / D converter. Although it has a certain effect, it is difficult to achieve a certain accuracy due to the influence of many factors such as circuit structure and noise interference. Increased, unable to reach the level 0 (0.5%) accuracy specified in its industry standard (QB / T1670-92 "Microcontrol Electronic Tensile Strength Testing Machine").
The current intelligent micro-control electronic paper tensile and compressive testing machine not only solves the low accuracy of the current force value of the product, but also grasps the similar characteristics of the mechanical and electronic parts of the tensile testing machine and the tensile testing machine. Organic integration, combined to save a lot of costs for users and enterprises. The performance and accuracy requirements of the electronic paper tensile and compression testing machine meet the highest precision level of the above standards: level 0 (0.5%)
System Solution and Principle System Architecture
A system with high-performance DSP chip TMS320LF2407A as the core for motion control and detection operation, and a dual CPU system with keyboard and LCD module based on SST89C58. The two CPUs communicated in a serial manner, and developed a three-party communication protocol with the host computer. Practice has proved that the protocol is efficient and practical. That is, the DSP is connected to the host computer (PC) through the USB interface to realize the switching control of the host computer and the keyboard, and the speed data or curve is printed by the host computer or the DSP, respectively.
Function realization
The function of the system mainly includes the following parts:
Motion system control and accurate measurement of displacement
In the detection and control part, the existing single-chip system is abandoned, and a more integrated DSP TMS320LF2407A is adopted as the core detection control chip. Its good hardware support for the motion control system, with hardware QEP, PWM and other modules, and the use of precision photoelectric encoder (2500p / r), AC servo drive, make the speed range of this product wider than the existing products (0.1 ～ 200.0mm / min stepless adjustable), the displacement is more accurate (0.01mm).
Detection and Collection of Weak Signal of Force Sensor
Using high-precision pull pressure sensor. Accuracy: 1.9585mv / v (compressive), 3.0025mv / v (tensile), to ensure the sensitivity of the signal source. Using 16-bit D / A converter to provide force sensor with 16-bit dynamic resolution and adjustable amplitude excitation voltage reduces the impact of voltage fluctuation on the sensor and fundamentally improves system accuracy. The use of Σ-Δ24-bit A / D converter (CS5532) ensures that accurate sensor signals can be effectively converted into accurate digital signals. In addition, the Σ-Δ structure has stronger anti-interference ability against the white noise of the system than the A / D of the double integral structure, making the system's high precision a reality. The 16-bit DSP2407A fully supports various data types of Standard C, avoids calculation errors within the accuracy range, and uses piecewise linear interpolation technology to further improve the linearity of the sensor. That is to further improve the detection accuracy of the system force value to 0.2%. Practice has proved that the detection method of this system is significantly better than the 1% force value accuracy of existing market products.
Data communication
The data communication of this system is more, and it is also one of the parts with larger engineering volume in software writing. A complete and efficient three-party communication protocol is defined. That is to realize the data sharing, instruction transfer and switching control between the host computer, DSP and SST89C58. Because the PC does not support 485 communication, the data volume of communication is moderate, and the distance is short, so the connection between the data acquisition DSP part and the host computer adopts a USB structure. The connection between DSP and SST89C58 uses 485 communication.
Human-computer interaction
Adopt independent module, namely 4 × 4 rows and columns scanning keyboard with SST89C58 as the core, 320 × 240 graphic LCD display. Real-time data display with DSP through serial communication.
Host computer
The host computer performs real-time data exchange with USB in USB mode, can realize all keyboard display module functions, and can realize independent control.
Block diagram and description of the system solution
The system is composed of several subsystems such as motion control subsystem, measurement and acquisition subsystem, human-computer interaction subsystem, and host computer. The constant speed measurement method is adopted.
Motion control subsystem
Because the constant speed measurement method is used, the smoothness of speed is the key and the premise of force value acquisition; it is the link between the motion control system and the measurement acquisition system.
In the motion control part, the existing single-chip system is abandoned, and the more integrated DSP TMS320LF2407A is adopted as the core detection control chip. The PWM signal is sent by the DSP to the AC servo motor driver. The AC servo motor driver drives the motor and performs closed-loop speed regulation, and the DSP does not manage it. At the same time, the servo sends the quadrature-encoded pulse signal of the photoelectric encoder to the QEP module of the DSP to trigger the timer to count the pulses, thereby accurately measuring the displacement of the chuck. And the catching module monitors the encoder ZERO for abnormal motor rotation.
Due to the adoption of Panasonic AC servo motor driver and motor, it not only makes the speed adjustment range wider and the speed more accurate (up to 1% accuracy), but also makes the speed adjustment easier to control and the speed smoothness is higher. The easy speed control only allows the DSP more time to process data.
Measurement and Acquisition Subsystem
A large range of high-precision force sensors (with an accuracy of 0.001mv) are used. The accuracy of the existing load cell is the same. The original system has been effectively improved under the same conditions of the sensor, that is, the 16-bit D / A converter is used to provide a 16-bit dynamic precision amplitude adjustable excitation voltage for the force sensor, which reduces the impact of voltage fluctuations on the sensor, and This excitation voltage supply method is very versatile. Practice has proved that the system accuracy has been greatly improved. The existing instruments mostly use double-integral A / D converters, the conversion accuracy is not high, and the ability to suppress common mode interference is not high. This system uses DSP + Σ-Δ24-bit A / D conversion (CS5532), which not only ensures that the sensor signal can be effectively converted into an accurate digital signal, but also the DSP has good support for high-level languages ​​(full support for standard C A variety of data types) makes the operation accuracy much higher than the measurement accuracy of the system. This makes the product greatly improve the accuracy of system force detection. This product uses DSP's powerful instruction processing ability and applies piecewise linear interpolation technology to further improve the linearity of the sensor. That further improves the system accuracy.
Human-computer interaction
Adopt 4 × 4 rows and columns scanning keyboard, 320 × 240 graphic interface liquid crystal display part is realized by SST89C58. Because the graphical interface requires a lot of storage space and 89C58 integrates 32K FLASH internally, and can write FLASH during operation, so human-computer interaction is mainly achieved through SST89C58. The host computer operation interface, data display, curve display and printing jointly realize human-computer interaction.
System innovation in key technologies
Existing small-scale tensile and compression testing machine products are independent products, and integration into one machine is rare. Because the mechanical part of the tensile and compression testers is similar and the electronic part is similar, this product not only integrates the mechanical part, that is, the double-screw beam structure, but also discards the existing single-chip system in the detection and control part, and adopts the integration degree The higher DSP TMS320LF2407A is the core detection control chip. Therefore, the organic integration of the two can save a lot of costs, and add a greater cost to improve the accuracy of the system.
The existing instruments of this kind pioneered the use of a more integrated DSP TMS320LF2407A as the core detection control chip, which has good hardware support for the motion control system, has hardware QEP, PWM and other modules, and uses Panasonic AC servo motor drivers Servo motor, precision photoelectric encoder (2500p / r). Make the speed range of this product wider, the actual stepless adjustment is 0.1 ～ 200.0mm / min, and the current products are mostly stepless adjustable 2 ～ 200mm / min; the displacement is more accurate (the highest standard specified by the national standard of 0.01mm); Smoother. Velocity smoothness is the prerequisite for measuring the force of tensile and compressive material testing machines, and also the link between the motion control system and the measurement and detection system.
A large range of high-precision force sensors (with an accuracy of 0.001mv) are used, which are the same as those of existing products. However, this product has effectively improved the use of the sensor under the same conditions of the sensor, that is, using a 16-bit D / A converter (LT1655) + high-precision power amplifier (LT1010) to provide 16-bit dynamic accuracy amplitude value for the force sensor. Adjusting the excitation voltage reduces the impact of excitation voltage fluctuation on the sensor, which not only makes it possible to improve the accuracy of the system, but also strengthens the system's ability to support different sensors.
The existing instruments mostly use 8-bit MCU + multi-dual integral 12-bit A / D converter, the conversion accuracy and anti-common mode interference ability is not high, and because the single-chip computer is single-byte calculation, the calculation accuracy and calculation speed The trade-off is difficult. This system uses DSP + Σ-Δ24-bit A / D converter (CS5532). Not only does it ensure that accurate sensor signals can be effectively converted into accurate digital signals, but DSP has good support for high-level languages ​​(full support for various data types of Standard C), making the calculation accuracy much higher than the measurement accuracy of the system. This makes the product greatly improve the accuracy of system force detection. This product uses DSP's powerful instruction processing ability and applies piecewise linear interpolation technology to further improve the linearity of the sensor. That further improves the system accuracy. In terms of system reliability, this product uses a DSP system architecture to remove a large number of peripheral devices compared to the existing single-chip system architecture, improving the reliability of the system. In actual debugging, the anti-interference ability is obviously better than that of ordinary single-chip system.
This product also has a lot of intelligent and humanized design in function
Automatic calibration
According to the regulations of the metrology industry, the inspection instruments must be inspected regularly. This system proposes the automatic calibration function for the first time and applies it to the product. The principle is as follows: the system stores the calibration-related parameters in the rewritable FLASH, the DSP reads the weight of 50% of the full-scale weight, uses the measured value as a reference, re-calibrates, and stores the calibrated parameters in the FLASH . The automatic calibration is completed.
Automatic measurement
When measuring existing products, first of all, it is required to use the up and down keys to fine-tune the paper to a critical state that is not tight, that is, to measure displacement. This product is processed on the software and does not need to be operated as above.
FEATURE:
- Food Contact is safe, FDA & LFGB certified.
- Dishwasher is safe.
- Many kinds of flower shape can make.
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You just need to squeeze once and beautiful flowers appear-just like magic.
- Piping tips are used for filling desserts, tarts shells and for frosting cakes and cupcakes.
You will need a pastry bag and a fixator,put the cream into pastry bag,attach a fixator to the tip of the pastry bag and then attach the decorating nozzles.you can make the flower or other pattern on the cake or biscuits.
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YANGJIANG SHENGHAI INDUSTRIAL&TRADING CO., LTD , https://www.shenghaiyj.com