CN103196988B

CN103196988B - Comprehensive test method for thermomagnetic effect under multi-field coupling

Info

Publication number: CN103196988B
Application number: CN201310131572.9A
Authority: CN
Inventors: 罗迎社; 陈胜铭; 罗树凌; 邓瑞基; 邓彪; 李卉; 张永忠; 任嘉
Original assignee: Central South University of Forestry and Technology
Current assignee: Central South University of Forestry and Technology
Priority date: 2013-04-16
Filing date: 2013-04-16
Publication date: 2014-02-26
Anticipated expiration: 2033-04-16
Also published as: CN103196988A

Abstract

The invention discloses a comprehensive test method for a thermomagnetic effect under multi-field coupling. The method is characterized in that a comprehensive test is carried out by modes of an upper computer and a lower computer, wherein the upper computer is connected with an infrared camera to detect a temperature change field of a sample, and a three-dimensional magnetic field, pull force applied to the sample by an upper clamp head of a hydraulic stretching test machine and the displacement of the upper clamp head when the sample is stretched are respectively tested through a three-dimensional magnetic field measurement device, a pull force measurement device and a displacement measurement device by a controller. The comprehensive test method integrates the measurement modules of the three-dimensional magnetic field, the temperature and the pressure/the displacement, so that a plurality of physical quantity can be synchronously and comprehensively acquired, and the test method is high in automaticity. The test method is high in integration level, high in control precision and easy to operate and control, can be used for measuring the temperature, pull force and magnetic induction intensity synchronously and comprehensively, is a bran-new test method, and lays a foundation for scientifically and exactly researching the thermomagnetic effect under the multi-field coupling condition.

Description

Many coupling integrated test facilities of pyromagetic effect

Technical field

The present invention relates to many coupling integrated test facilities of a kind of pyromagetic effect.

Background technology

Research shows, when defective superpolymer stretches with certain speed, can produce certain temperature rise around at breach, the magnetic field of the some strength of association simultaneously.Relation between the temperature rise producing during for further this magnetic field of research and stretching, need to be in automatic restrained stretching speed, the temperature rise of test specimen and magnetic induction density are carried out to synchro measure, and preserve all measurement data with time synchronizing method: pulling force, displacement, magnetic induction density, temperature (view data), to study and to determine the relation between them.

Although existing equipment is measured a certain physical quantity (as temperature, or displacement, or magnetic field) separately, but, cannot realize the precise synchronization of various detection meanss, cannot realize many composite measurements in coupling situation, thereby cannot study objectively the incidence relation of each physical quantity.

In addition, existing hand-hydraulic testing machine, adopts button to come controlled pressure size and loading velocity, not only set pressure size and loading velocity flexibly, and also control accuracy is poor, troublesome poeration.

The patent [its name is called defective rheid pyromagnetic collection and test macro (application number is 200810031098)] that is CN101261245A as publication number can only realize the detection in magnetic field.

Thereby the comprehensive synchro measure under many coupling conditions, is a key issue of this area, it is also a technical matters urgently to be resolved hurrily.

In addition, publication number is the patent of CN101261245A, a kind of magnetic field detection scheme has been proposed, to gather magnetic field data based on Hall sensor array, the greatest problem that this scheme exists is complex structure, need structure sensor array, and need to complicated feed circuit and control circuit be sensor service; This sensor can only be measured the magnetic field data of a direction in addition, cannot detect Three-Dimensional Magnetic sensed data, so limitation is large.

Therefore, be necessary to design many coupling integrated test facilities of a kind of brand-new pyromagetic effect.

Summary of the invention

Technical matters to be solved by this invention is to provide many coupling integrated test facilities of a kind of pyromagetic effect, many of this pyromagetic effects coupling integrated test facilities are integrated three-dimensional magnetic field, temperature and pressure the measurement module of displacement, can realize synchronous, the synthetical collection of a plurality of physical quantitys, and automaticity is high.Be easy to control, easy to implement.

The technical solution of invention is as follows:

Many coupling integrated test facilities of pyromagetic effect, is characterized in that, sample holder are contained between the upper grip and lower chuck of hydraulic extension test machine; The centre of sample has a hole; Adopt the pattern of host computer and slave computer to implement comprehensive detection, wherein host computer connects infrared camera with the temperature variation field of test samples; The camera lens of infrared camera is over against the middle part in sample front; Host computer communicates to connect with the controller as slave computer,

By three-dimensional magnetic field measurement mechanism, tension measuring device and displacement measuring device, the three-dimensional magnetic field of test samples in drawing process, the upper grip of hydraulic extension test machine impose on the pulling force of sample and the displacement of upper grip to controller respectively respectively; The check-out console of three-dimensional magnetic field measurement mechanism is positioned at the rear side of sample; The upper grip that controller is also controlled hydraulic extension test machine by hydraulic control device moves;

Test process is:

Starting hydraulic pressure cupping machine makes seaming chuck apply pulling force to sample, and control pulling force size that seaming chuck applies and the ascending velocity of upper pull head, by host computer, synchronously start infrared camera, three-dimensional magnetic field measurement mechanism, tension measuring device and the three-dimensional magnetic field of the displacement measuring device temperature field in drawing process, multi-point with Real-time Collection sample, the upper grip of hydraulic extension test machine imposes on the pulling force of sample and the displacement of upper grip;

Final acquisition at sample be stretched temperature field in process and the synchronous delta data in magnetic field.

Adopt sectional type PID control strategy restrained stretching speed;

(1), when tensile force is less than 50KN, pid parameter is Kp=100, Ti=1000, Td=0;

(2), when pulling force is more than or equal to 50KN, pid parameter is Kp=500, Ki=100, Kd=20;

(3), when pulling force starts to decline, pid parameter is Kp=300, Ki=1000, Kd=0;

The corresponding closed-loop control system of described sectional type PID control strategy, by controlling the proportional control valve of hydraulic system with the flow of control hydraulic oil, final restrained stretching speed; Controller is output as the proportional magnitude of voltage of flow to hydraulic system; Feedback quantity is the stretching displacement amount that displacement measuring device gathers; Draw speed value is preset in being given as of closed-loop control system.

Many the coupling integrated test systems of employing based on pyromagetic effect are implemented integration test;

Described many coupling integrated test systems based on pyromagetic effect comprise hydraulic extension test machine, temperature measuring equipment, three-dimensional magnetic field measurement mechanism, tension measuring device, displacement measuring device, hydraulic control device, controller and host computer;

Temperature measuring equipment is the temperature measuring equipment based on infrared camera; Temperature measuring equipment is connected with host computer (being industrial computer); The camera lens of infrared camera is over against the middle part in sample front;

Three-dimensional magnetic field measurement mechanism, tension measuring device, displacement measuring device and hydraulic control device are all connected with controller;

By hydraulic extension test machine, being clamped the tabular sample of strip and sample upper end is applied to pulling force makes sample produce deformation;

The camera lens of infrared camera over against the front of sample to measure the real time temperature data of sample;

Three-dimensional magnetic field measurement mechanism is arranged on the real-time three-dimensional magnetic field data of the back side to check that sample produces in the process being stretched;

Hydraulic control device drives hydraulic extension test machine;

Tension measuring device and displacement measuring device detect respectively the real-time displacement that the upper clamping part of pulling force that hydraulic extension test machine applies sample and hydraulic extension test machine produces;

Controller and host computer communication connection;

PC control hydraulic extension test machine, temperature measuring equipment and three-dimensional magnetic field measurement mechanism start simultaneously, and by host computer synchronous collection real time data, described real time data comprises: the real-time displacement data that the upper clamping part of real time temperature data, three-dimensional magnetic field data, pulling force and hydraulic extension test machine produces.

Tension measuring device is measured in the oil cylinder of hydraulic extension test oil pressure indirectly to measure the pulling force of clamping part to sample by strain pressure transducer; Strain pressure transducer is cylinder mode, strain pressure transducer main body be one with the cylinder of an axial blind hole, the openend of cylinder is provided with for connecting the external thread of oil cylinder; The outer wall of cylinder is provided with 4 foil gauge: R1～R4; Wherein R1 and R2 are being arranged on a side of cylinder outer wall, and R3 and R4 are arranged on the relative opposite side of cylinder outer wall; And R1 and R3 are laterally concordant and be positioned at the outside of solid section (non-blind hole section) of cylinder, R2 and R4 are laterally concordant and be positioned at the blind hole section outside of cylinder, laterally refer to cylinder radially;

R1～R4 connects into bridge detection circuit: R1 and R4 connect successively after with direct supply and connect; After R2 and R3 connect successively, with direct supply and connect, the tie point of R1 and R4 is c point, and the tie point of R2 and R3 is d point, and the voltage between c point and d point is the output voltage of sensor, and this output voltage has reflected the pressure that tension measuring device need to detect;

Displacement measuring device is the displacement measuring device based on incremental encoder, comprises support (4), fixed pulley (5), the coaxial pulley of photoelectric encoder (2), stay cord (1) and weight (6); Support (4) is fixed on lower chuck, and fixed pulley (5) and the coaxial pulley of photoelectric encoder (2) are installed on support (4); The upper end of stay cord (1) is fixed on the upper grip of hydraulic extension test machine, and the lower end of stay cord (1) is lifted with described weight (6), and weight (6) naturally droops; The coaxial pulley of photoelectric encoder and fixed pulley are walked around in the stage casing of stretching (1); The coaxial pulley of photoelectric encoder is installed as fixed pulley; The pulse signal of photoelectric encoder axle (3) output reflection displacement;

Described three-dimensional magnetic field measurement mechanism is three-dimensional magnetic field, 5 positions measurement mechanism, comprises single-chip microcomputer, Magnetic Sensor, MUX, analog to digital converter, hysteresis effect elimination circuit and serial communication circuit;

Described Magnetic Sensor is 5, is symmetricly set on 5 some positions in PCB front, and 4 Si Jiaochu that are arranged on pcb board wherein, another is arranged on the central authorities of pcb board; Each Magnetic Sensor has 3 signal output channels, exports respectively the magnetic induction signal of X, Y, tri-directions of Z;

Magnetic Sensor is connected with the input interface of single-chip microcomputer with analog to digital converter by MUX successively; The output port of the channel selecting termination single-chip microcomputer of MUX;

Two input ends of hysteresis effect elimination circuit connect respectively reset terminal and the set end (set8 and reset8) of single-chip microcomputer; Reset terminal and set end are the IO port of single-chip microcomputer; The output terminal that hysteresis effect is eliminated circuit is connected with the impulse polarization circuit in Magnetic Sensor;

Single-chip microcomputer is connected with host computer by described serial communication circuit;

Described Magnetic Sensor adopts HMC2003 chip, described MUX comprises 3 multi-way switchs: i.e. the first multi-way switch, the second multi-way switch and the 3rd multi-way switch, and analog multichannel switch adopts the 74HC4051 chip with 8 road signal input channels and 1 signal output channels; Analog to digital converter adopts the ADS7825 chip of sixteen bit; ADS7825 chip has four input end of analog signal;

The X signal output channels of 5 Magnetic Sensors joins with 5 signal input channels of the first multi-way switch respectively;

The Y-signal output channel of 5 Magnetic Sensors is joined with 5 signal input channels of the second multi-way switch respectively;

The Z signal output channels of 5 Magnetic Sensors joins with 5 signal input channels of the 3rd multi-way switch respectively;

3 signal output channels of 3 multi-way switchs join with 3 input end of analog signal of analog to digital converter respectively;

Three digital selecting sides of 3 multi-way switchs (being A, B, C) are corresponding in parallel;

It is the pulse-generating circuit based on power MOSFET tube that hysteresis effect is eliminated circuit, and power MOSFET tube adopts IRF7106 chip;

After the 5-8 pin short circuit of IRF7106 chip, by the first electric capacity (C83) and the impulse polarization circuit in Magnetic Sensor, join;

1 pin of IRF7106 chip and 3 pin are ground connection and direct supply anode VCC1 respectively;

2 pin (G1) of IRF7106 chip connect described reset terminal (reset8);

Another IO port of single-chip microcomputer is as set end (set8), and set end (set8) connects the base stage of the triode (Q18) of NPN type by the first resistance (R81); The emitter grounding of triode (Q18), the collector of triode (Q18) meets VCC1 by the second resistance (R82); The collector of triode (Q18) also connects 4 pin (G2 end) of IRF7106 chip by the second electric capacity (C81); Between 4 pin of IRF7106 chip and VCC1, be connected to the 3rd resistance (R83); Between VCC1 and ground, be connected to the 3rd electric capacity (C82);

Serial communication circuit adopts private communication device MAX232, and single-chip microcomputer adopts STC89C54RD chip;

The described switch board that also comprises integral type based on many coupling integrated test systems of pyromagetic effect, in described switch board, be integrated with described host computer and controller, described host computer is industrial computer, described controller is ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, in switch board, be provided with plug-type finger-board, finger-board is provided with keyboard and the mouse that connects industrial computer; The bottom of switch board is provided with hydraulic control device and hydraulic pump; ARM embedded control system has for connecting the interface of three-dimensional magnetic field measurement mechanism, tension measuring device, displacement measuring device and hydraulic control device, and industrial computer is provided with the USB interface that connects temperature measuring equipment.

The method that controller detects three-dimensional magnetic field by three-dimensional magnetic field measurement mechanism is as follows:

5 some positions at surveyed area arrange respectively 5 Magnetic Sensors that can export Three-Dimensional Magnetic induced signal; Magnetic Sensor output 15 road signal after MUX is selected, the Three-Dimensional Magnetic induced signal of a Magnetic Sensor of output in each sampling period, then form digital signal by analog to digital converter and send in single-chip microcomputer; Finally by single-chip microcomputer, be uploaded to host computer after to all data processings that gather, complete the measurement of three-dimensional magnetic field;

In described measuring process, single-chip microcomputer is eliminated circuit by hysteresis effect and is produced forward and reverse polarization pulse and export to Magnetic Sensor, to eliminate Magnetic Sensor in magnetic-field measurement process, is magnetized; Measuring process is:

Step 1: the magnetic-field measurement having circulated successively to 5 some positions;

The magnetic-field measurement of each some position comprises the magnetic field of measuring successively x, y and z direction;

Step 2: after the three-dimensional magnetic field of 5 some positions is measured and all completed, just completed the measurement of frame data, and returned to step 1 and circulate next time;

The unidirectional magnetic-field measurement process of Magnetic Sensor at each place, some position is:

Before A/D conversion starts, single-chip microcomputer is first exported an asserts signal SET makes sensor obtain forward polarization, then start analog to digital converter and carry out A/D conversion, in order to prevent that random disturbance from causing A/D transformed error, adopt 100 sampled values AVG1 that averages, then reset signal RESET of single-chip microcomputer output makes Magnetic Sensor obtain reverse polarization, then start analog to digital converter 100 sampled values of reentrying, and try to achieve mean value AVG2, then by the mean value AVG1 of twice acquisition and AVG2 process numerical evaluation V _oUT=(AVG1+AVG2)/2, obtain a numerical value as this unidirectional magnetic-field measurement value;

Described and one direction refer to x, y or z direction.

The size of sample: long 800mm, wide 85mm, center-hole diameter 5mm, middle segment length 100mm, stage casing width 75mm, the transition portion of stage casing and end adopts fillet, and the radius of fillet is 5mm; Draw speed is 3-40mm/min, and sample rate is set to every 0.5 second once sampling.

Beneficial effect:

The invention solves following technical matters:

1, take original hand-hydraulic testing machine as basis, design automatically controlled Hydrauservo System, to facilitate computer control;

Rack below is hydraulic system, comprise oil pump and integration hydraulic control system, embedded computer gathers oil cylinder travelling speed by photoelectric encoder, after the travelling speed comparison operation with arranging, output control signal, control hydraulic proportion valve, regulate flow rate of hydraulic system, with the travelling speed of controlling oil cylinder with that speed is set is consistent.Gather pressure, the displacement of oil cylinder simultaneously, and send to industrial control computer by USB mouth.

2, design array of magnetic sensors, for gathering near magnetic induction density superpolymer sheet material, and gives embedded control system by image data by serial port;

3, adopt ARM embedded type CPU to design a set of control system, realize when hydraulic system is controlled by constant stretch speed, gather pulling force and magnetic field, and by certain format, by USB interface, give computing machine by image data;

The originality of many coupling integrated test facilities of pyromagetic effect of the present invention is embodied in:

1, first the design of measuring system of the measuring system in hydraulic tensioning system, temperature field, magnetic induction density field is become to a unified pilot system, can realize the synchronous acquisition of all parameters like this, while stretching breakage for superpolymer, the research of a plurality of parameters and coupling mechanism thereof provides pacing items.The pilot system of existing market is due to cannot the whole test figure of synchronous acquisition, thereby can only analyze the variation of the single parameter in stretching Breakage Processes, cannot analyze the coupling mechanism between a plurality of parameters.

2, control and the temperature pattern collection of heat being released to infrared instrument are merged, and during by test synchronous acquisition temperature field data integrity preserve, for studying the coupled relation of temperature and other parameter.

3. switch board compact conformation, level is reasonable, easy to operate.

4. displacement detector structure is ingenious, and can meet the precision of measuring and controlling, and easy to implement, cost is low.

5. tension measuring device adopts indirect metering system to measure pulling force, is skillfully constructed, easy to implement.

6. three-dimensional magnetic field, 5 positions measurement mechanism, 5 Three-Dimensional Magnetic sensors (HMC2003 chip) that employing is distributed in place, difference position detect field signal, and adopt the multi-channel analog multi-way switch based on 74HC4051 chip to realize data exchange, adopt again analog to digital converter to convert simulating signal to digital signal and output in single-chip microcomputer, complete the collection of multi-point three-dimensional magnetic field data.

Wherein, adopt multi-way switch can effectively simplify circuit design, and make full use of the port of single-chip microcomputer, and control convenient, one group of three-dimensional magnetic field data that once can a Magnetic Sensor output of synchronous acquisition.

In addition, the present invention has also designed hysteresis effect and has eliminated circuit to eliminate magnetic hysteresis, to improve magnetic field detection precision.

Adopt a plurality of sensors with three-dimensional magnetic field signal output, and under the cooperation of MUX and analog to digital converter, realize multi-point, three-dimensional magnetic field detection, simple in structure, be easy to control, easy to implement, and adopt hysteresis effect to eliminate after circuit, can further improve the accuracy of detection of device.

In sum, integrated level of the present invention is high, automaticity is high, control accuracy is high, is easy to control, and can realize synchronous, the composite measurement of temperature-pulling force-magnetic induction density, be a kind of brand-new experimental system, the pyromagetic effect of accurately studying under many coupling conditions for science provides solid foundation.

Accompanying drawing explanation

Fig. 1 is the general principles block diagram of three-dimensional magnetic field, 5 positions measurement mechanism;

Fig. 2 is that five Magnetic Sensors are arranged in the position view on pcb board;

Fig. 3 is the multichannel selection of three-dimensional magnetic field, 5 positions measurement mechanism and the schematic diagram of analog to digital conversion circuit;

Fig. 4 is multi-channel sampling process flow diagram;

Fig. 5 is constant-current source circuit figure;

Fig. 6 is set/reset pulse schematic diagram;

Fig. 7 is set/reset pulsing circuit schematic diagram.

Fig. 8 be bias current band peripheral circuit (one of);

Fig. 9 is bias current band peripheral circuit (two);

Figure 10 is the general frame of many coupling integrated test systems based on pyromagetic effect of the present invention;

Figure 11 is the structural representation of switch board;

Figure 12 is that the structural drawing of strain pressure transducer (is schemed a) and circuit diagram (figure b);

Figure 13 is photoelectric encoder scheme of installation;

Figure 14 is the Facad structure schematic diagram of test specimen.

Figure 15 is the thermic magnetic induction density-time history on test specimen surface under 20mm/min speed.

Figure 16 is for controlling software interface schematic diagram;

Figure 17 is the experimental result interface of the curve of each detection limit of containing experimental system.

Label declaration: 1-stay cord; The coaxial pulley of 2-photoelectric encoder; 3-photoelectric encoder axle; 4-support; 5-fixed pulley; 6-weight.

Embodiment

Below with reference to the drawings and specific embodiments, the present invention is described in further details:

As Fig. 1-16, many coupling integrated test facilities of a kind of pyromagetic effect, is characterized in that, sample holder are contained between the upper grip and lower chuck of hydraulic extension test machine; The centre of sample has a hole [acting as of this hole uses stress to concentrate principle, ruptures, to facilitate each sensor image data while guaranteeing plate stretch from porose position]; Adopt the pattern of host computer and slave computer to implement comprehensive detection, wherein host computer connects infrared camera with the temperature variation field of test samples; The camera lens of infrared camera is over against the middle part in sample front; Host computer communicates to connect with the controller as slave computer,

Test process is:

Adopt sectional type PID control strategy restrained stretching speed;

Hydraulic control device drives hydraulic extension test machine;

Controller and host computer communication connection;

2 pin (G1) of IRF7106 chip connect described reset terminal (reset8);

The described switch board that also comprises integral type based on many coupling integrated test systems of pyromagetic effect, in described switch board, be integrated with described host computer and controller, described host computer is industrial computer, described controller is ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, in switch board, be provided with plug-type finger-board, finger-board is provided with keyboard and the mouse that connects industrial computer; The bottom of switch board is provided with hydraulic control device and hydraulic pump, and [oil cylinder is on tension tester, oil pump is for pressurizeing hydraulic oil, high pressure liquid force feed after pressurization is used for driving oil cylinder, in figure control block hydraulic unit with comprise oil pump and drive motor with some for controlling the switching control pilot, proportional control valve etc. of hydraulic oil] ARM embedded control system has for being connected the interface of three-dimensional magnetic field measurement mechanism, tension measuring device, displacement measuring device and hydraulic control device, industrial computer is provided with the USB interface that connects temperature measuring equipment.

Described and one direction refer to x, y or z direction.

Embodiment 1:

As Figure 10-15, whole hardware system is transformed on a tension tester, adopt upper and lower computer structure: host computer is comprised of industrial control computer system, major function is that the speed closed loop that carries out drawing process is controlled, Thermal Infrared Data collection, the data acquisition of magnetic induction density field and the demonstration of all data and the preservation in temperature field.Slave computer is comprised of embedded (ARM) system, and main data acquisition and the command interpretation that host computer is passed are down carried out.Upper and lower machine adopts USB interface to connect.

The parameter of hydraulic test system is set by host computer, and by USB mouth send to control parameter with steering order to embedded control system, by USB mouth, receive the various image data that embedded control system sends, and show and preservation; By another USB mouth, regularly receive the temperature field data that thermal infrared imager is sent, and show with temperature infrared picture format, with picture format, preserve;

The function of host computer is processing controls, and deal with data file: user can select arbitrarily four collection capacities in all image data, and 4 collection capacities are presented on time shaft, like this just can analyze the relation between stretching displacement, temperature, magnetic induction density and draw speed. simultaneously(it is prior art that program realizes part)

Embedded control system

Embedded control system is as slave computer, and the data that complete the collection of pulling force, displacement data and receive Magnetic Sensor in native system are together transferred to the function of host computer.Simultaneously host computer returns to lower machine again by the controlled quentity controlled variable that after these data receivers, the computing by control strategy generates, and slave computer is controlled hydraulic system again and completed the action that at the uniform velocity stretches.

Native system has adopted the embedded microcontroller LPC1765 based on ARM Cortex-M3 kernel of grace intelligence Pu (NXP) company.Should there is stronger arithmetic capability and abundant peripheral component for controller.Specifically for this control system following function:

● the AD of 12 conversion in sheet, resolution and sample rate meet the needs of pulling force sampling.

● orthogonal encoder interface can not taken by the decoding work of the direct completion bit shift measurement of hardware scrambler the calculation resources of processor.

● the controlled quentity controlled variable of host computer is carried out in PWM output, controls electro-hydraulic proportional valve and adjusts hydraulic pressure to reach the object of controlling pulling force.

● usb function, has replaced the serial communication mode that upper and lower computer is conventional in the past.Its advantage is that data rate is fast, highly versatile.The notebook computer that is particularly suitable for not having serial ports, facilitates field adjustable.

Speed is controlled:

In order to study conveniently, during stretching, speed control range is per minute 0-40mm, and concrete test speed is set controlling software interface by user, and to require be at the uniform velocity to stretch, so adopt PID to control when normal stretching.But test is found: the initial period stretching, starting inertia due to proportioning valve and hydraulic system, can cause this stage control control accuracy very poor, overshoot is very large, so during our working control, adopt segmentation PID to control: when tensile force is less than 50KN, illustrate and draw in initial period, at this moment due to the inertia of proportioning valve, and there is interlock process in chuck, cause inputting obvious postpone, so, control parameter and take scale parameter as main, through overtesting, adopt the control parameter (Kp=100 of first set PID, Ti=1000, Td=0), and output is increased to amplitude limit function.When tensile force is greater than 50KN, while showing that test specimen starts to enter normal draw stage, at this moment should start at the uniform velocity to stretch by the speed of setting,, at this moment, should be by adopting the second cover pid parameter (Kp=500, Ki=100, Kd=20).When pulling force starts to decline, show to stretch in plastic period, at this moment adopt the 3rd cover pid control parameter (Kp=300, Ki=1000, Kd=0).Through test, this segmentation PID controls, and can effectively guarantee, in the whole drawing process of superpolymer sheet material, can keep all the time the consistance of draw speed.

Sample: material: pure Polyvinylchloride (PVC) hardboard

Thickness δ=10mm

Tension measurement

Oil pressure in oil cylinder has reflected the size of tensile force simultaneously.Therefore record the oil pressure in oil cylinder, can obtain the size of tensile force.In oil cylinder bottom opening, setting pressure sensor is to measure oil pressure in oil cylinder.The oil cylinder piston diameter of former WE-30 type universal testing machine is D=140mm, can be regarded as to such an extent that the area of oil cylinder piston is:

S＝π(D/2) ²＝3.14×(0.14/2) ²＝0.015m ² (2.1)

The maximum load of testing machine is 30 tons, is roughly equal to 300KN.In-oil cylinder maximum pressure is:

3×10 ⁵/0.015＝2×10 ⁷Pa＝20MPa (2.2)

Consider the situation of overload, native system adopts SM25Y01 type strain pressure transducer, and its maximum range is 25MPa, meets the requirement of system.Strain gauge transducer is comprised of flexible member and foil gauge, and oil pressure makes flexible member produce distortion, then with foil gauge, distortion is converted to electric signal output.

Sensor construction sketch, as shown in Figure 12 (a), reflects the size of when test pulling force indirectly by sensor measurement oil pressure.

Sensor construction form is drum type brake.It is the thin cylinder that there is blind hole an one end, and blind hole depth is half left and right that cylinder is high, and nose end has screw thread to be connected with oil hydraulic system.On the hollow parts of circular hole and the outer wall of solid section, be respectively pasted with two foil gauges, sensitive grid direction is vertical with axis, and is connected into bridge road by Figure 12 (b).When inner chamber oil pressure increases, thin cylinder produces dolioform distortion, foil gauge R2 and R4 Tensile, and R1 and R3 are constant, only play temperature compensation function.During work, a, b termination power, at c, the output voltage signal of d end is directly proportional direct ratio to deflection, thereby is also directly proportional to pressure.

Due to testing machine in the course of the work, oil temperature can raise, therefore, sensor should can be stablized, work in certain temperature range.

SM25Y01 type strain pressure transducer main performance index is as follows:

● range 25MPa

● temperature drift≤0.03%FS/ ℃

● nonlinearity≤0.3%FS

● hysteresis error≤0.3%FS

● reproducibility error≤0.15%FS not

● precision 0.3%FS

Generally speaking, the advantage that adopts strain pressure transducer to measure is easy to install, and highly versatile, while particularly measuring large load, more seems small and exquisite easy.Its shortcoming is that precision is high less than load sensor, and when the friction force between piston and oil cylinder is larger, dynamometry error ratio is larger ^[8].In order to reduce the measuring error of pressure transducer as far as possible, many label taking fixed points of need to trying one's best when the power of demarcation value, especially in small value force section.

Fuel injection pressure signal actual measurement be pressure, according to the structure of testing machine, the actual pressure that should be hydraulic jack generation of pulling force deducts the deadweight of chuck and oil cylinder, tensile force f=kV-g, wherein k and g are constant, g is the deadweight of chuck and oil cylinder, K is the coefficient relevant with whole hardware system, V is the signal of the pressure transducer output magnitude of voltage after amplifying, k and g ask method: adopt tension tester (the non-tension measuring device of the present invention of having calibrated, but the tension measurement instrument of standard) survey 2 different values of thrust: F1 and F2, record again magnitude of voltage V1 and V2 that these two values of thrust are corresponding, by this 2 class value substitution F=kV-g, can try to achieve k and g.

Displacement measurement

In test, superpolymer test specimen is stretched after about 30-80mm and will ruptures.Therefore the measurement range of system requirements displacement is that 0-100mm and resolution are 0.1mm.Although not being very high, general Linear displacement transducer, accuracy requirement still can not meet the demands.Although grating scale can meet the requirement of range and measuring accuracy, not too convenient on improvement and installation.Therefore in native system, adopt photoelectric encoder to realize the measurement of displacement.

Photoelectric encoder is a kind of sensor of pulse or digital quantity that geometry of machinery displacement on output shaft converted to by opto-electronic conversion.This is one of maximum sensor of application at present.Photoelectric encoder is mainly comprised of grating disc and photoelectric detection system two large divisions.Grating disc is on the plectane of certain diameter, to open several rectangle light holes decile.During detection, the synchronized rotation of grating disc and motor, the pick-up unit forming through electronic components such as light emitting diodes detects the some pulse signals of output, by calculating the number of photoelectric encoder output pulse per second, just can reflect measured corner or rotating speed.

According to light, delete scale method and the signal output form of dish, photoelectric encoder can be divided into increment type, absolute type and hybrid three kinds:

(1) incremental encoder is directly to utilize photoelectricity transformation principle to export three prescription wave impulse A, B and Z phase; A, B two group pulse phase differential 90 degree, thus can judge easily sense of rotation, and Z is mutually for often turning a pulse, for reference point, locates.Its advantage is that principles of construction is simple, and mechanical mean lifetime can be more than several ten thousand hours, and antijamming capability is strong, and reliability is high, is suitable for long Distance Transmission.Its shortcoming be cannot output shaft rotation absolute location information.

(2) absolute type encoder utilizes natural binary or circulation scale-of-two (Gray code) mode to carry out opto-electronic conversion.Absolute type encoder and incremental encoder difference are printing opacity on disk, lighttight bargraphs, and absolute encoder can have some codings, according to the coding of reading on code-disc, detect absolute position.

(3) hybrid absolute value encoder, it exports two groups of information: one group of information is for detection of position of magnetic pole, with absolute information function; Another group is the complete output information with incremental encoder.

Consider that native system only need to measure the stretching displacement situation of superpolymer, therefore in native system, adopt incremental encoder.The installation of photoelectric encoder as shown in figure 13.Support is arranged on lower chuck, and upper grip is fixed in stay cord upper end, and weight naturally droops.When two chuck generation relative displacements, can drive photoelectric encoder rotation to record by stay cord.

Photoelectric encoder is selected HTR-3A-1000 type photoelectric encoder [10], its resolution 1000 pulses/circle.It is 15.92mm that the pulley of installing on photoelectric encoder output shaft obtains its value footpath D through Precision Machining, and its perimeter L is: L=π D=3.14 * 15.92mm=49.98mm.Therefore the resolution of this displacement measurement mechanism is: 49.98mm/1000 < 0.05mm meets the designing requirement that resolution is greater than 0.1mm.

Whole measuring process automatically completes under the coordination of industrial control computer, user only need to click and start test after installing test specimen, and computing machine just will gather all data simultaneously, and show in good time, preserve with curve form, to further study the relation between each data.

1, PVC sheet material (being pure Polyvinylchloride hard plate) is processed into sample by Figure 14 mode, and makes a call in center the circular hole that a diameter is 5mm;

2,, by the hydraulic oil pump switch opens of testing machine, when temperature is during lower than 10 ℃, need preheating after 10 minutes, to start again test; Opening control power supply;

3, with controlling the upper and lower chuck of software operation, move, make the distance of upper and lower chuck be about 620mm;

4, by sample holder between upper and lower chuck, and will in the center pit of sample and Magnetic Sensor, think alike;

5, infrared thermal releasing instrument (being infrared camera) is set, aligned central holes, connects infrared thermal releasing instrument to controlling computing machine by USB mouth;

6, draw speed being set is 10mm/min, and sample rate is set to every 0.5 second once sampling, then starts to stretch; At temperature pattern window, 4 points for measuring temperature are set, in whole process of the test, the temperature of these 4 positions will be as representative temperature with temperature---and time mode shows real time temperature curve;

7, click on-test, controlling software will require user to input test specimen numbering, this numbering also will be the filename that test figure is preserved, user inputs after numbering, control system will start test by setup parameter, and in drawing process, embedded computer is by speed restrained stretching speed is set, by sample rate, gather all data, and displacement, two groups of data of pulling force were presented in hydraulic pressure curve by the sampling time; Meanwhile, also, by data such as the temperature in the whole process of collection, magnetic induction density, with curve map form, show, so and image data is preserved simultaneously

8, after test specimen is broken, click test and stop, having tested;

9, in whole process of the test, can click time-out, start to come the time-out of Control experiment or restart test.

Three digital selecting sides of 3 multi-way switchs (being A, B, C) corresponding [the A of 3 multi-way switchs end is in parallel, and the B end of 3 multi-way switchs is in parallel, and the C end of 3 multi-way switchs is in parallel] in parallel.

74HC4051 is 8 tunnels analogy MUX/demultplexers, with 3 digital selecting side (S0 to S2, also be A, B, C end), 1 low effective Enable Pin (E), 8 independent input/output terminals (Y0 to Y7) and 1 public input/output terminal (Z).When E is low, one of them of 8 switches will be chosen by S0 to S2 (low resistance state).When E is high, all switches all enter high-impedance state, directly ignore S0 to S2.VCC1＝20V

Three-dimensional magnetic field, 5 positions measurement mechanism based on plate stretch pyromagetic effect measures plate by five point sensors and multi-channel data acquisition plate two parts are laminated, five point sensors are measured plate sensors and are arranged as shown in Figure 2, and adopting this arrangement is according to the PVC sheet material location positioning that maximum thermic magnetic field produces in drawing process.Five three-dimension sensors are arranged in polymer plate and in drawing process, most possibly occur the position of magnetic field intensity maximum; 5 three-dimension sensor electricity theory diagrams as shown in Figure 1.

53 D weak magnetic field sensor groups that HMC2003 in figure (1-5) is comprised of 5 HMC2003, this is the core cell of whole sensor, its arrangement mode is as shown in Figure 2, MUX is comprised of three 74HC4051 analog multichannel switches, the X of 5 HMC2003 of three 74HC4051 analog multichannel switch difference gatings, Y, the three-dimensional output signal of Z, enter three input end IN0 of analog to digital converter, IN1, IN2, the selection control end A of three 74HC4051 analog multichannel switches, B, C is in parallel, it is selected to control and is carried out by single-chip microcomputer, single-chip microcomputer adopts STC89C54RD+ 8-bit microcontroller, change A, B, the state of C, can realize any one sensors X, Y, in the time of Z signal, switch, it is each sensors X, Y, Z output signal is to arrive analog to digital converter simultaneously, analog to digital converter is ADS7825 sixteen bit A/D converter, there are four input end IN0, IN1, IN2, IN3, as long as four passages of timesharing gating, just can realize the conversion of input analog amount, native system is selected IN0, IN1, tri-input ends of IN2 are respectively as X, Y, the signal input part of Z 3 D weak magnetic field.

It is to be magnetized and to reduce forward and reverse polarization pulse generation circuit of measuring sensitivity and arranging in order to eliminate sensor in magnetic-field measurement process that hysteresis effect is eliminated peripheral circuit, can produce forward and reverse peak point current and reach the transient peak pulse of 4A, this pulse action is in the impulse polarization circuit of HMC2003 inside, realize the moment polarization of giant magnetoresistance, to improve the measurement sensitivity of giant magnetoresistance, forward and reverse polarization pulse is the SET being sent by single-chip microcomputer, RESET signal controlling.

Before A/D conversion starts, first export a SET signal, make sensor obtain forward polarization, then start A/D converter and carry out A/D conversion, in order to prevent that random disturbance from causing A/D transformed error, the method that adopts 100 sampled values to average is carried out digital filtering, then single-chip microcomputer is exported a RESET signal, make sensor obtain reverse polarization, then start A/D converter and carry out again 100 A/D conversions, and average, then the mean value of twice acquisition is obtained to a numerical value as a measured value through numerical evaluation VOUT=(AVG1+AVG2)/2, when the three dimensional signal of a sensor is all disposed, the three-dimensional magnetic field that has completed a point is measured, after the three-dimensional magnetic field of 5 sensors all completes, just completed the measurement of frame data.After single-chip microcomputer completes a frame data collection, detect the data request signal that serial communication has or not host computer to send, if the request signal that has host computer to send sends frame data according to agreement form, after completing data transmission, single-chip microcomputer enters the next employing cycle.Serial communication consists of private communication device MAX232.

In figure, HMC2003 is three-dimensional high sensitivity magnetic field survey sensor, 5 HMC2003 arrange according to shown in Fig. 2, hysteresis effect is eliminated peripheral circuit and is coordinated with HMC2003 internal pulses degaussing circuit, completes the forward and reverse polarization of giant magnetoresistance, makes sensor have highest measurement sensitivity; Data acquisition board is by MUX, analog to digital converter and single-chip microcomputer form, multi-way switch is three-dimension sensor channel selector switch, by the X of 5 three-dimension sensors, Y, timesharing gating is to three input channels of A/D converter ADS7825 respectively for Z, and ADS7825 is 16 A/D converters, and single-chip microcomputer is 8 STC single-chip microcomputers.

HMC2003 chip internal comprises three-dimensional giant magnetoresistance measurement bridge, bridge road constant current-supplying power supply, accurate reference voltage, three-dimensional precision instrument amplifier, pulse degaussing circuit and background magnetic field are to canceling coil, its effect is the variable quantity of Weak magentic-field to be converted into the variable quantity of output voltage at zero magnetic field state, extrapolates the variation value of Weak magentic-field according to the corresponding relation of magnetic field and voltage.

Wherein to measure bridge be the base unit of measuring Weak magentic-field for three-dimensional giant magnetoresistance, and Weak magentic-field is exactly by giant magnetoresistance, to measure bridge to be converted to differential output voltage.

The permanent power supply in bridge road, for three-dimensional magnetic field measurement provides constant current source, to reduce the impact of power-supply fluctuation on signal source, has reduced systematic error.

Accurate reference voltage is to canceling coil, to provide a reference voltage for background magnetic field.

Three-dimensional precision instrument amplifier amplifies output by faint differential voltage signal, so that the transmission of voltage signal and conversion.

The two eliminates circuit in conjunction with forming hysteresis effect pulse degaussing circuit and hysteresis effect peripheral circuit, makes giant magnetoresistance measure bridge all the time in the most highly sensitive state without hysteresis effect, is used for eliminating hysteresis effect to measuring the impact of sensitivity.

Background magnetic field offsets coil circuit and background magnetic field peripheral circuit forms background magnetic field elimination circuit, is used for eliminating working environment background magnetic field, makes sensor real work in zero magnetic field environment, realizes the precision measurement of Weak magentic-field.

The effect of MUX be by 5 measurement points the analog signal voltage of totally 15 unit survey sensor outputs be transferred to an A/D converter, realize the conversion that is completed 15 tunnel simulating signals by an A/D converter.

Single-chip microcomputer is as system control unit, the coordination of data acquisition and various functions.

GMR sensor is a kind of element of measuring magnetic field intensity, different from a lot of other devices, and it is directly measured magnetic field intensity and is not the rate of change of induced field, so measure Weak magentic-field, is very easily.GMR sensor has that volume is little, highly sensitive, the range of linearity is wide, and serviceability temperature is high, low cost and other advantages

That the giant magnetoresistance sensor in the design is selected is HMC2003, this class magnetoresistive transducer is by 4 element wheat stone bridge configuration, there is integrated set/reset band, can reduce temperature drift effect, nonlinearity erron and due to the existence of highfield, the loss of the output signal causing.And there is integrated biasing band, can eliminate the impact of hard iron interference.Three-D magnetic field sensor HMC2003, can measure three-dimensional (x, y, the z) direction of Weak magentic-field.

The amplifying circuit of HMC2003 periphery is prior art, at this, does not elaborate.

Background magnetic field cancellation techniques

Under the giant magnetoresistance impact of hot-wire coil and terrestrial magnetic field around, giant magnetoresistance has very strong background magnetic field around, background magnetic field has had a strong impact on the measurement of giant magnetoresistance to Weak magentic-field, for improving giant magnetoresistance sensor, detect the faint definition that changes field in magnetic field, on giant magnetoresistance around on a circle coil, " compensating field " and background magnetic field identical to size of giant magnetoresistance sensor by coil, opposite direction offset, and make giant magnetoresistance work in zero magnetic field state.

Apply compensating field and eliminate background magnetic field and bring and compensate by bias current, bias current band can also drive current by electric current band, offset measurement magnetic field accurately, this is known as closed loop configuration.Magnetic field biasing band (biasing+and setover-) can generate one with the just measured magnetic field that applies magnetic field equidirectional.The electric current band of HMC2003 often can provide the magnetic field of 10e by 50mA electric current, the electric current band of HMC2003 often can provide the magnetic field of 10e by 5mA electric current.(1 Gauss=10e in air).Bias current band appear to one biasing+and biasing-pin between nominal resistance.

Bias current band can be as the feedback element in closed loop circuit.Utilize the bias current band in current feedback loop can measure expectation value.If reach this object, the output terminal of amplifier of electrical bridge is connected to the current source that drives bias current band.Utilize high-gain and reverse feedback in loop.This will make magnetoresistive bridge road be output as 0 (output +=output-).This method can provide the splendid linearity and temperature characterisitic, and the resistance mode with balance operates magnetoresistive bridge all the time.That is, no matter measure which type of magnetic field, all can be by it elimination by the electric current of bias current band.Electric bridge " is seen " zero magnetic field condition all the time, and being used for eliminating the resultant current that applies magnetic field is a direct examination question of this magnetic field intensity, and can be converted into magnetic field value.

Forward polarization is eliminated hysteresis effect with reverse polarization

Most of downfield sensors can be subject to large magnetic interference (> 4～20 Gausses') impact, may cause the decay of output signal.In order to reduce this impact and maximum signal output, can in magnetoresistive bridge, apply magnetic switch handoff technique, eliminated the impact of degaussing history.The order ground of set/reset electric current band is exactly that magnetoresistive transducer is returned to the high sensitivity state of measuring magnetic field.This can be by realizing large pulsation of current by S/R electric current band.S/R electric current band looks like the resistance being added between SR+ and SR-pin.This electric current band is different from bias current band, because it is magnetically coupled on magnetoresistive transducer with Z-axis or insensitive direction.Once sensor is set (or reset), can realize low noise and highly sensitive magnetic-field measurement.

When magnetoresistive transducer is exposed in disturbing magnetic field, sensor element can be divided into the random magnetic area of some directions, thereby causes sensitivity decay.Peak point current will generate a high-intensity magnetic field higher than the pulse current (set) of minimum requirements electric current by set/reset electric current band, and this magnetic field can be again aimed at magnetic area unified on a direction, will guarantee like this high sensitivity and reading repeatably.Reverse impulse (reset) can be with the direction of contrary direction rotation magnetic area, and changes the polarity of sensor output.If there is not disturbing magnetic field, the state of this magnetic area can keep the several years.

S/R in chip should aim at again by pulse current, or the magnetic area in " upset " sensor.This pulsewidth can be as short as 2 microseconds, and during continuous impulse, average power consumption is less than 1mA (DC).Can be chosen to be every 50ms has the pulse of 2 μ s pulsewidths, or longer, to economize on electricity.Unique requirement is that each pulse only applies in one direction.That is, if+pulse of 3.5A is used to " set " sensor, and impulse attenuation should be lower than 0 electric current.Any negative (lower than rated current) current pulse signal all can cause " cannot set " sensor, and can not obtain best sensitivity.

Utilize S/R electric current band, can eliminate or reduce many impacts, comprising: temperature drift, non-linear mistake, intersecting axle impact and because the existence of highfield causes the loss of signal output.

The principle of 3 D weak magnetic field is to utilize giant magnetoresistance resistance to change along with the variation in magnetic field, and the variation that will record resistance, the variation that can then survey its output voltage to specific electric current of resistance, because what we surveyed is voltage, so electric current is a steady state value preferably, so could not affect the linear changing relation between voltage and resistance, and to constant current source of resistance, just can avoid electric current to be subject to the impact of resistance variations, thereby avoid the impact of power-supply fluctuation on signal source. Fig. 5 is the constant-current source circuit that utilizes operational amplifier to form.

Because desirable operational amplifier input both end voltage equates, and A point voltage is unaffected, so constant, corresponding B point voltage is also constant, so obviously can obtain electric current I _cconstant output.Field effect transistor in circuit plays the effect of a fixed pressure drop.

Set/reset pulsing circuit (being that hysteresis effect is eliminated circuit)

In order to eliminate background magnetic field, must for magnetic field effect, eliminate circuit by peripheral circuit a set/reset pulse is provided, require its oscillogram as shown in Figure 6.

Set in the design/and reset signal be to be exported by Single-chip Controlling, then to be converted into pulse signal by peripheral circuit.Be exactly the set/reset pulsing circuit that utilizes IRF7106 to produce as shown in Figure 7.

There are two field effect transistor IRF7106 the inside, and one is N channel enhancement field effect transistor, and one is P-channel enhancement type field effect transistor, as Fig. 7, when set end [i.e. set8 in figure] is low level, triode Q18 cut-off, capacitor C 81 two ends are all high level, 4 pins of IRF7106 are also high level, no-voltage between s2 and G2, thus the output of D2 end no current, when reset end [i.e. reset8 in figure] is low level, no-voltage between s1 and G1, so D1 holds also no current output.In sum, because when set end and reset hold while being low level, D1 holds and D2 holds equal no current output, and set holds and reset end is alternating set/reset, so only need to analyze when we analyze, set holds and reset holds that field effect transistor that sets high level.

As the i.e. set8 in figure of set[] while putting 1 (high level), triode Q18 conducting, the left end of capacitor C 81 sports low level, in the moment of this sudden change, capacitor C 81 is also uncharged, so capacitor C 81 right-hand members (4 pins of IRF7106) are also low levels, the conducting of P-channel field-effect transistor (PEFT) pipe, D2 end has inverse current output, and when capacitor C 81 chargings are when complete, 4 pins of IRF7106 become again high level, the cut-off of P-channel field-effect transistor (PEFT) pipe, no current output, so when set puts 1, SR+8 has the output of reverse impulse electric current.

As the i.e. reset8 in figure of reset[] while putting 1 (high level), the conducting of N channel field-effect pipe, D1 end has forward current output (being assumed to be 1), again because output terminal has capacitor C 83, so only have when electric current is 1 from 0 saltus step, SR+8 has the output of direct impulse electric current.

Described in combining, this circuit has met the requirement of hysteresis effect elimination circuit aaset bit/reset pulse.

The design of magnetic field cancellation bias current control circuit

The effect of bias current band is exactly to eliminate background magnetic field, has three giant magnetoresistance sensors in three-D magnetic field sensor, only analyzes the peripheral circuit of a giant magnetoresistance sensor here.

When DC current in bias current band by time bias current band can have multiple-working mode.

(1) balance outside unwanted magnetic field.

(2) electric bridge biasing is set to zero.

(3) electric bridge output can drive bias current to bring the magnetic field of eliminating in closed loop.

(4) receiving the gain of order Shi Qiao road can the interior automatic calibration of system.

When the electric current of specific size is tided over bias current band, bias current band is by producing a magnetic field contrary with tested magnetic direction, so can eliminate any environmental magnetic field.Bias current band often can provide the magnetic field of 10e by 50m electric current.

Characteristic based on above bias current band, biasing band can be as the feedback element in closed loop circuit.In this kind of application, the output terminal of amplifier of electrical bridge is connected in the drive current source of biasing band, utilizes high-gain and negative feedback in a road to make electric bridge be output as zero.No matter measure which type of magnetic field, all can be by it elimination by the electric current of bias current band, electric bridge is seen zero magnetic field condition all the time.This method has the good linearity and temperature characterisitic.The electric current that is used for eliminating external magnetic field is one of this magnetic field directly tolerance, and can be directly changed into magnetic field value.

Bias current band can also be used to automatic calibration magnetoresistive bridge, and it is very useful to proofreading once in a while electric bridge gain or adjusting within the scope of large temperature pendulum.Can power on or normal running during whenever carry out.Its principle is: along a circuit, get 2 points, and determine the gradient of this line, be i.e. gain.When electric bridge is just during the external magnetic field at Measurement sensibility, output is handed over and is kept constant.Record the reading of stabilizing magnetic field, be designated as H1. and now apply specific currents by bias current band, then record this reading, be designated as H2.Cause the variation in the magnetic field of magnetoresistive transducer measurement to be referred to as to apply magnetic field increment (Δ Ha), magnetoresistive transducer gain can be calculated as follows:

Gain＝(H2-H1)/ΔHa.

Except the above, bias current band also has many other purposes, and key is that external environment condition magnetic field and bias magnetic field can superpose simply mutually, by magnetoresistive transducer, as single magnetic field, is measured.

Be exactly the peripheral circuit of bias current band as shown in Figure 8 and Figure 9, these two voltage followers be mainly play buffer compartment from effect.

The output port of these two voltage followers is received respectively two ends Xoff+1 and the Xoff-1 of HMC2003 background magnetic field to canceling coil.One of them voltage follower input port connects accurate reference voltage, another voltage follower input is controlled by single-chip microcomputer, because the Main Function of voltage follower be buffer compartment from, so background magnetic field can not affected by circuit on the voltage at canceling coil two ends, so just can provide stable " compensating field " to giant magnetoresistance sensor.

Data acquisition system (DAS) explanation

The design mainly completes sensor and periphery circuit design, but sensor check must have the cooperation of peripheral circuit, and the control of peripheral circuit is realized by single-chip data acquisition system, in order to illustrate that single-chip microcomputer is to the control principle of sensor and work schedule, now data data acquisition and controlling is partly briefly introduced, make the thinking of design more clear.

Data acquisition system (DAS) in the design be one take that the collection that single-chip microcomputer is core is controlled, A/D conversion and the mini system of communicating by letter.

In data acquisition system (DAS), need analog quantity to be converted to data volume, and A/D is converted to analog quantity the device of digital quantity, the index that he need to consider has: resolution, switching time, transformed error etc.And single-chip microcomputer is the basic microprocessing systems of this system, it completes, and data read, processing and logic control, a series of task such as data transmission.In this system, we adopt the single-chip microcomputer of 89C52 series.

This data acquisition circuit figure comprises following three parts.

A/D analog to digital converter

In the design, select ADS7825 as analog to digital converter.ADS7825 is 4 passages that U.S. B-B company produces, 16 analog to digital converters.It is no more than data sampling and switching time 25 μ s, the analog voltage of can input-10V～10V by list-5V Power supply.Data after A/D conversion can parallel output, also serializable output, and data transfer module also can be set to 4 interchannel continuous circulations conversions, and it is extremely convenient to use.

While using ADS7825 chip, will

set to 0, then give pin adds a negative edge can start AD conversion.Now,

the output of pin keeps low level, until data-switching is complete and the content of inner output register is updated.During this period, ADS7825 no longer responds new conversion command.Must be noted that, pin is output as before high level,

must be set to high level, otherwise can cause data not yet to run through, new conversion just starts, thereby makes loss of data.

Because the data of ADS7825 conversion get final product parallel output, also serializable output, so reading of data also must divide parallel and two kinds of modes of serial to discuss.In the design, be by

be set to high level, select parallel output mode, so will when data read

pin sets low level, chooses after ADS7825 chip, gives

pin is inputted a negative pulse, starts AD conversion.AD changes and data latch the time into 25 μ s.Detect the output level of pin can judge data-switching state, works as state flag bit

time, data-switching is still being carried out, now readable data not.

time, show that data-switching has finished and data have entered output register, now can reading out data.Make parallel data output select position BYTE=0, can read most-significant byte data, BYTE=1, reads least-significant byte data.

Simulating signal, respectively from IN0, IN1, the input of IN2 pin, is confirmed mode and the address of conversion by ADR0, ADR1 and CONTC pin, when CONTC=1, select continuous translative mode, when

while being low level with PWRD end, AD conversion and reading will carry out at tetra-interchannel continuous circulations of IN0～IN3.When

at this EOC, transfer to after high level, A0 and A1 pin will output next time sampling channel address used, actually from the conversion that starts to circulate of which input channel, and before depending on that CONTC is set to high level, the input value of A0 and A1 pin.The output of A0 and A1 pin and the relation being sampled between passage are as listed in table 5.1.1.

When CONTC is set to low level, adopt intermittently translative mode.A0 and A1 pin are as input end, and its input value and sampling channel relation are as listed in table 5.1.2

In the design, ADR0, ADR1, CONTC,

pin is all to be controlled by single-chip microcomputer output signal, so its conversion regime should be also to be controlled by single-chip microcomputer.

Channel selecting when table 5.1.1 changes continuously

Channel selecting when table 5.1.2 intermittently changes

This designing requirement conversion regime should be to carry out at IN0, IN1, tri-interchannel continuous circulations of IN2.So should select continuous translative mode, and the initial value of A1, A0 is set to 01 before each circulation, so that circulate while starting, data start conversion from AIN0 passage.When AIN2 Channel-shifted finishes, immediately will

set low, stop conversion, and start circulation next time.So just, realized all data timesharing packet switched storages.

Single-chip microcomputer

Single-chip microcomputer is a kind of towards large-scale integrated circuit (IC) chip, is an important branch in microcomputer.This system is by CPU, random accesP data-carrier store, read-only program memory, imput output circuit (I/O mouth), also likely comprise that the circuit such as Timer/Counter, serial communication port, display driver circuit (LCD and LED drive circuit), pulse-width modulation circuit, analog multiplexer and A/D converter are integrated on a monolithic chip, have formed a minimum but perfect computer task.Single-chip microcomputer will use specific group to translate and composing software program compiler, with keiluvision2, program is being downloaded in single-chip microcomputer.

And the design selects, it is P89C52X2BN single-chip microcomputer, P89C52X2BN is low-voltage, 8 single-chip microcomputers of high-performance CMOS, sheet include 8k bytes can be repeatedly erasable read-only program memory (PEROM) and the Random Access Data storer (RAM) of 256bytes, device adopts high density, nonvolatile storage technologies to produce, compatible with standard MCS-51 order set and 8052 pins of products, 8 central processing units of sheet built-in general-purpose (CPU) and Flash storage unit, powerful, P89C52X2BN single-chip microcomputer is suitable for many comparatively complex controls application scenario.

Wherein P0 is one group of two-way I/O mouth of 8 open-drain types, is also multiplexing mouthful of address/data bus.Here as digital signal acquiring mouth.P1 mouth be one with 8 two-way I/O mouths of internal pull-up resistor, the output buffer stage of P1 can drive 4 TTL logic gates.In the design, P1 mouth is as controlling delivery outlet, and wherein P1.0～P1.5 is for to analog-to-digital control, and P1.6 and P1.7 are used for the control of aaset bit/reseting pulse circuit, and P2.0～P2.2 is used for controlling the timesharing gating of data.P3.0 and P3.1 mouth are as serial input delivery outlet,

RST is the input that resets.When oscillator is worked, RST pin occurs that two above high level of machine cycle will make monolithic processor resetting.

When access external program memory or data-carrier store, ALE output pulse is for the least-significant byte byte of latch address.Generally, ALE is still with the fixing pulse signal of 1/6 output of oscillation frequency clock, so its external output clock or for timing object.

Program stores and allows

output is the read strobe signal of external program memory, when single-chip microcomputer is during by external program memory instruction fetch, and twice of each machine cycle

effectively,, export two pulses.

for external reference allows.Want to make CPU only to access external program memory,

end must keep low level.

XTAL1 is the input end of the internal clock generator of oscillator inverting amplifier.

XTAL2 is the output terminal of oscillator inverting amplifier.

Serial-port communication

I have selected standard RS-232 interface this serial port, and it is level and Transistor-Transistor Logic level conversion driving circuit.Conventional chip is MAX232, and the advantage of MAX2321 is:

(1) a slice chip can complete the dual-use function that sends conversion and receive conversion.

(2) single power supply+5V power supply

(3) its circuit design be connected fairly simple and multiple functional.

MAX232 chip is that Maxim is the interface circuit of the rs-232 standard serial ports design of computer specially, and use+5V single power supply, can realize the IC chip that Transistor-Transistor Logic level and RS-232 level are changed mutually.

Wherein pin 1-6 (C1+, V+, C1, C2+, C2-, V-) is for supply voltage conversion, as long as externally access corresponding electrochemical capacitor; Pin 7-10 and pin 11-14 form the change-over circuit of two groups of TTL signal levels and RS-232 signal level, and corresponding pin can directly be connected with the Transistor-Transistor Logic level pin of serial port of single chip computer and the RS-232C level pin of PC.

The design is the data that gather three-dimensional, so when sampling, should gather respectively the data of X, Y, Z axis direction, in four conversion input channels in A/D converter, passage 1 sampling directions X data, passage 2 sampling Y-direction data, passage 3 sampling Z directional datas.So during analog to digital conversion, should be respectively to passage 1, passage 2, passage 3 gating conversions.Sampling routine is realized block diagram as shown in Figure 4.

Because the data of 8 points that the design has used 83 D weak magnetic field sensor measurements, so a circulation will be set, make an A/D converter can change the data that 8 three-dimension sensors are measured.Owing to being 8 circulations, so will export tri-bytes of ABC by single-chip microcomputer, controlled.

4 sensors of four jiaos, it is horizontal, and longitudinal pitch should be arranged in theory plate stretch process and be out of shape maximum region, and the design obtains according to experimental summary, gets laterally=40mm, longitudinally=35mm

Figure 17 has provided the data and curves of experimental system, curve below has been set the different Show Color that needs 4 image data successively, (in Figure 17, selected the numerical value (being magnetic field 2Y) of temperature, the displacement in drawing process, the pulling force in drawing process and second magnetic induction density sensor Y-direction that C orders, the upper right corner shows the infrared temperature image in whole process of the test, user can select arbitrarily 4 temperature observation point in this image, and shows with curve form.In curve from the graph, can find out: displacement was directly proportional substantially to the time, namely draw speed substantially at the uniform velocity, pulling force starts while reaching certain value to decline, show that test specimen starts fracture, the temperature that C is ordered sharply rises when starting to rupture, and when temperature rises, magnetic induction density rises also obviously.

The synchronous change curve of each detection limit of Figure 17 shows: the scheme that adopts the present embodiment, can realize the synchronous of temperature (multi-point), pulling force, displacement and magnetic inductor intensity (5 three-dimensional magnetic fields) accurately detects, thoroughly solved the difficulty that prior art cannot guarantee synchro measure, for the pyromagetic effect of studying under many coupling conditions provides an outstanding experiment porch.

Claims

1. many coupling integrated test facilities of pyromagetic effect, are contained in sample holder between the upper grip and lower chuck of hydraulic extension test machine; The centre of sample has a hole;

It is characterized in that, adopt the pattern of host computer and slave computer to implement comprehensive detection, wherein host computer connects infrared camera with the temperature variation field of test samples; The camera lens of infrared camera is over against the middle part in sample front;

Host computer and controller communication connection as slave computer, by three-dimensional magnetic field measurement mechanism, tension measuring device and displacement measuring device, the three-dimensional magnetic field of test samples in drawing process, the upper grip of hydraulic extension test machine impose on the pulling force of sample and the displacement of upper grip to controller respectively respectively; The check-out console of three-dimensional magnetic field measurement mechanism is positioned at the rear side of sample; The upper grip that controller is also controlled hydraulic extension test machine by hydraulic control device moves;

Test process is:

2. many coupling integrated test facilities of pyromagetic effect according to claim 1, is characterized in that, adopt sectional type PID control strategy restrained stretching speed;

3. many coupling integrated test facilities of pyromagetic effect according to claim 1 and 2, is characterized in that, adopt many coupling integrated test systems based on pyromagetic effect to implement integration test;

Temperature measuring equipment is the temperature measuring equipment based on infrared camera; Temperature measuring equipment is connected with host computer; The camera lens of infrared camera is over against the middle part in sample front;

Hydraulic control device drives hydraulic extension test machine;

Controller and host computer communication connection;

4. many of pyromagetic effects according to claim 3 coupling integrated test facilities, is characterized in that, tension measuring device is measured in the oil cylinder of hydraulic extension test oil pressure indirectly to measure the pulling force of clamping part to sample by strain pressure transducer; Strain pressure transducer is cylinder mode, strain pressure transducer main body be one with the cylinder of an axial blind hole, the openend of cylinder is provided with for connecting the external thread of oil cylinder; The outer wall of cylinder is provided with 4 foil gauge: R1～R4; Wherein R1 and R2 are being arranged on a side of cylinder outer wall, and R3 and R4 are arranged on the relative opposite side of cylinder outer wall; And R1 and R3 are laterally concordant and be positioned at the outside of solid section of cylinder, R2 and R4 are laterally concordant and be positioned at the blind hole section outside of cylinder, laterally refer to cylinder radially;

Displacement measuring device is the displacement measuring device based on incremental encoder, comprises support (4), fixed pulley (5), the coaxial pulley of photoelectric encoder (2), stay cord (1) and weight (6); Support (4) is fixed on lower chuck, and fixed pulley (5) and the coaxial pulley of photoelectric encoder (2) are installed on support (4); The upper end of stay cord (1) is fixed on the upper grip of hydraulic extension test machine, and the lower end of stay cord (1) is lifted with described weight (6), and weight (6) naturally droops; The coaxial pulley of photoelectric encoder and fixed pulley are walked around in the stage casing of stay cord (1); The coaxial pulley of photoelectric encoder is installed in the mode of fixed pulley; The pulse signal of photoelectric encoder axle (3) output reflection displacement;

Three digital selecting sides of 3 multi-way switchs are corresponding in parallel;

2 pin (G1) of IRF7106 chip connect described reset terminal (reset8);

The described switch board that also comprises integral type based on many coupling integrated test systems of pyromagetic effect, in described switch board, be integrated with described host computer and controller, described host computer is industrial computer, described controller is ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, in switch board, be provided with plug-type finger-board, finger-board is provided with keyboard and the mouse that connects industrial computer; The bottom of switch board is provided with hydraulic control device to be had for being connected the interface of three-dimensional magnetic field measurement mechanism, tension measuring device, displacement measuring device and hydraulic control device with hydraulic pump ARM embedded control system, and industrial computer is provided with the USB interface that connects temperature measuring equipment.

5. many coupling integrated test facilities of pyromagetic effect according to claim 4, is characterized in that, the method that controller detects three-dimensional magnetic field by three-dimensional magnetic field measurement mechanism is as follows:

Described and one direction refer to x, y or z direction.

6. many coupling integrated test facilities of pyromagetic effect according to claim 5, is characterized in that the size of sample: long 800mm, wide 85mm, center-hole diameter 5mm, middle segment length 100mm, stage casing width 75mm, the transition portion of stage casing and end adopts fillet, and the radius of fillet is 5mm; Draw speed is 3-40mm/min, and sample rate is set to every 0.5 second once sampling.