CN103196988A

CN103196988A - Comprehensive test method for thermomagnetic effect under multi-field coupling

Info

Publication number: CN103196988A
Application number: CN2013101315729A
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: 2013-07-10
Anticipated expiration: 2033-04-16
Also published as: CN103196988B

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 couplings of thermic magnetic effect integrated test facility

Technical field

The present invention relates to many couplings of a kind of thermic magnetic effect integrated test facility.

Background technology

Studies show that, when defective superpolymer stretches with certain speed, can around breach, produce certain temperature rise, the magnetic field of the certain intensity of association simultaneously.Relation between the temperature rise that produces during for further this magnetic field of research and stretching, need be when controlling draw speed automatically, temperature rise and magnetic induction density to test specimen carry out synchro measure, and preserve all measurement data with time synchronizing method: pulling force, displacement, magnetic induction density, temperature (view data), with research and determine relation between them.

Though existing equipment is measured a certain physical quantity (as temperature, or displacement, or magnetic field) separately, but, can't realize the accurately synchronous of various detection meanss, namely can't realize many composite measurements under the coupling situation, thereby can't study the incidence relation of each physical quantity objectively.

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.

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

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

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

Therefore, be necessary to design many couplings of a kind of brand-new thermic magnetic effect integrated test facility.

Summary of the invention

Technical matters to be solved by this invention provides many couplings of a kind of thermic magnetic effect integrated test facility, many of this thermic magnetic effects coupling integrated test facility is 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 the automaticity height.Be easy to control, easy to implement.

The technical solution of invention is as follows:

Many couplings of a kind of thermic magnetic effect integrated test facility is characterized in that, sample holder is contained between the upper grip and lower chuck of hydraulic extension test machine; The centre of sample has a hole; Adopt host computer and lower computer mode 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 with communicate to connect as the controller of slave computer,

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 by three-dimensional magnetic field measurement mechanism, tension measuring device and displacement measuring device respectively; The check-out console of three-dimensional magnetic field measurement mechanism is positioned at the rear side of sample; Controller also moves by the upper grip of hydraulic control device control hydraulic extension test machine;

Test process is:

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

Finally obtain temperature field in sample is stretched process and the synchronous delta data in magnetic field.

Adopt sectional type PID control strategy control draw speed;

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

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

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

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

Employing is implemented integration test based on many coupling integrated test systems of thermic magnetic effect;

Described many coupling integrated test systems based on the thermic magnetic 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 all are connected with controller;

Clamp the tabular sample of strip and make sample produce deformation to applying pulling force on the sample by the hydraulic extension test machine;

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

The 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 that is stretched;

Hydraulic control device drives the hydraulic extension test machine;

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

Controller and host computer communicate to connect;

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 last 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 with the pulling force of indirect measurement clamping part to sample by strain pressure transducer; Strain pressure transducer is cylinder mode, and the strain pressure transducer main body is a cylinder that has an axial blind hole, and the openend of cylinder is provided with for the external thread that connects 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, and 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: namely R1 and R4 connect the back successively with direct supply and connect; R2 and R3 connect the back successively with direct supply and connect, and the tie point of R1 and R4 is the c point, and the tie point of R2 and R3 is the d point, and the voltage between c point and d point is the output voltage of sensor, and this output voltage has namely reflected the pressure that tension measuring device need 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 the lower chuck, and fixed pulley (5) and the coaxial pulley of photoelectric encoder (2) are installed on the 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) is sagging naturally; 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 the magnetic induction signal of X, Y, three directions of Z respectively;

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

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

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

Described Magnetic Sensor adopts the HMC2003 chip, described MUX comprises 3 multi-way switchs: i.e. first multi-way switch, 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; The 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 first multi-way switch respectively;

The Y-signal output channel of 5 Magnetic Sensors is joined with 5 signal input channels of 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;

The three number word selecting sides (being A, B, C) of 3 multi-way switchs are corresponding in parallel;

Hysteresis effect elimination circuit is the pulse-generating circuit based on power MOSFET tube, and power MOSFET tube adopts the IRF7106 chip;

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

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 first resistance (R81); The emitter grounding of triode (Q18), the collector of triode (Q18) meets VCC1 by second resistance (R82); The collector of triode (Q18) also connects 4 pin (G2 end) of IRF7106 chip by second electric capacity (C81); Be connected to the 3rd resistance (R83) between 4 pin of IRF7106 chip and the VCC1; Be connected to the 3rd electric capacity (C82) between VCC1 and the ground;

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

The described switch board that also comprises integral type based on many coupling integrated test systems of thermic magnetic effect, be integrated with described host computer and controller in the described switch board, described host computer is industrial computer, described controller is the ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, be provided with plug-type finger-board in the switch 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; The ARM embedded control system has for the interface that connects 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.

Controller is as follows by the method that the three-dimensional magnetic field measurement mechanism detects the three-dimensional magnetic field:

5 some positions at surveyed area arrange 5 Magnetic Sensors that can export three-dimensional magnetic induction signal respectively; 15 road signals of Magnetic Sensor output are after MUX is selected, and the three-dimensional magnetic induction signal of a Magnetic Sensor of output in each sampling period forms digital signal by analog to digital converter again and sends in the single-chip microcomputer; Be uploaded to host computer after by single-chip microcomputer all data of gathering being handled at last, finish 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, and Magnetic Sensor is magnetized in the magnetic-field measurement process to eliminate; Measuring process is:

Step 1: the magnetic-field measurement to 5 some positions is finished in circulation successively;

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

Step 2: when the three-dimensional magnetic field of 5 some positions measure all finish after, just finished the measurement of frame data, and returned step 1 and circulate next time;

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

Before the A/D conversion beginning, single-chip microcomputer asserts signal SET of output earlier makes sensor obtain the forward polarization, then start analog to digital converter and carry out the A/D conversion, in order to prevent that random disturbance from causing the 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, start analog to digital converter 100 sampled values of reentrying then, and trying to achieve mean value AVG2, mean value AVG1 and the AVG2 with twice acquisition passes through numerical evaluation V then _OUT=(AVG1+AVG2)/2, obtain a numerical value as this unidirectional magnetic-field measurement value;

Described and folk prescription to referring 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 per 0.5 second once sampling.

Beneficial effect:

The invention solves following technical matters:

1, based on original hand-hydraulic testing machine, designs automatically controlled Hydrauservo System, to make things convenient for computer control;

The rack below is hydraulic system, comprise oil pump and integrated hydraulic control system, embedded computer is gathered the oil cylinder travelling speed by photoelectric encoder, by with the travelling speed comparison operation that arranges after, the output control signal, the control hydraulic proportion valve is regulated flow rate of hydraulic system, with the travelling speed of control oil cylinder with that speed is set is consistent.Gather pressure, the displacement of oil cylinder simultaneously, and send to industrial control computer by the USB mouth.

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

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

The originality of many couplings of thermic magnetic effect of the present invention integrated test facility is embodied in:

1, first the measuring system in hydraulic tensioning system, temperature field, the design of measuring system of magnetic induction density field are become a unified pilot system, can realize the synchronous collection of all parameters like this, the research of a plurality of parameters and coupling mechanism thereof provides pacing items when stretching breakage for superpolymer.The pilot system of existing market be owing to can't gather whole test figures synchronously, thereby can only analyze the variation of the single parameter in the damaged process that stretches, and can't analyze the coupling mechanism between a plurality of parameters.

2, control and the temperature pattern collection of heat being released infrared instrument merged, and the data integrity ground of gathering synchronously will test the time, temperature field preserves, for the coupled relation of studying temperature and other parameter.

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

4. the displacement detector structure is ingenious, and can satisfy 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, and is 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 based on the multi-channel analog multi-way switch of 74HC4051 chip and realize the data switching, adopt analog to digital converter to become digital signal to output in the single-chip microcomputer analog signal conversion again, finish the collection of three-dimensional magnetic field, multiple spot position data.

Wherein, adopt multi-way switch can effectively simplify circuit design, and take full advantage of the port of single-chip microcomputer, and control is convenient, once can gather one group of three-dimensional magnetic field data of a Magnetic Sensor output synchronously.

In addition, the present invention has also designed hysteresis effect and has eliminated circuit to eliminate magnetic hysteresis, to improve the 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 multiple spot position, three-dimensional magnetic field detection, simple in structure, be easy to control, easy to implement, and after adopting hysteresis effect to eliminate circuit, can further improve the Device Testing precision.

In sum, integrated level height of the present invention, automaticity height, control accuracy height are 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 thermic magnetic effect of accurately studying under many coupling conditions for science provides solid foundation.

Description of drawings

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 the 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 the multi-channel sampling process flow diagram;

Fig. 5 is constant-current source circuit figure;

Fig. 6 is set/reset pulse synoptic 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 The general frame based on many of thermic magnetic effect coupling integrated test systems 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 the photoelectric encoder scheme of installation;

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

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

Figure 16 is control software interface synoptic diagram;

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

Label declaration: 1-stay cord; The coaxial pulley of 2-photoelectric encoder; 3-photoelectric encoder axle; The 4-support; The 5-fixed pulley; The 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 couplings of a kind of thermic magnetic effect integrated test facility is characterized in that, sample holder is 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, guarantees when sheet material stretches from porose position fracture, to make things convenient for each sensor image data]; Adopt host computer and lower computer mode 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 with communicate to connect as the controller of slave computer,

Test process is:

Adopt sectional type PID control strategy control draw speed;

Hydraulic control device drives the hydraulic extension test machine;

Controller and host computer communicate to connect;

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 thermic magnetic effect, be integrated with described host computer and controller in the described switch board, described host computer is industrial computer, described controller is the ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, be provided with plug-type finger-board in the switch 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 used for hydraulic oil is pressurizeed, high-pressure and hydraulic oil after the pressurization is used for driving oil cylinder, control block hydraulic unit with comprises that oil pump and drive motor and some are used for switching control pilots of control hydraulic oil, proportional control valve etc. among the figure] the ARM embedded control system has be used to the interface that is connected 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 of connection temperature measuring equipment.

Described and folk prescription to referring to x, y or z direction.

Embodiment 1:

As Figure 10-15, whole hardware system is transformed at a tension tester, adopt the upper and lower computer structure: host computer is made up of industrial control computer system, and major function is to carry out the speed closed loop control of drawing process, the thermal infrared data acquisition in temperature field, the data acquisition of magnetic induction density field and demonstration and the preservation of all data.Slave computer is made up of embedded (ARM) system, mainly finishes data acquisition and the command interpretation execution to passing under the host computer.The upper and lower machine adopts USB interface to connect.

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

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

Embedded control system

Embedded control system is as slave computer, and the data of finishing the collection of pulling force, displacement data and receive Magnetic Sensor in native system together are transferred to the function of host computer.Simultaneously host computer receives controlled quentity controlled variable that the computing of back by control strategy generate with these data and returns to machine down again, and slave computer is controlled hydraulic system again and finished 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 have stronger arithmetic capability and abundant peripheral component for controller.Specifically used following function at this control system:

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

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

● the controlled quentity controlled variable of host computer is carried out in PWM output, and the control electro-hydraulic proportional valve is adjusted hydraulic pressure to reach the purpose of control pulling force.

● usb function has replaced upper and lower computer serial communication mode commonly used in the past.Its advantage is that data rate is fast, highly versatile.Be particularly suitable for not having the notebook computer of serial ports, make things convenient for field adjustable.

Speed control:

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

Sample: material: pure Polyvinylchloride (PVC) hardboard

Thickness δ=10mm

Tension measurement

Oil pressure in the oil cylinder has reflected the size of tensile force simultaneously.Therefore record the oil pressure in the oil cylinder, can obtain the size of tensile force.In the oil cylinder bottom opening, the setting pressure sensor is to measure oil pressure in the 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.Then 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, satisfies the requirement of system.Strain gauge transducer is made up of flexible member and foil gauge, and oil pressure makes flexible member produce distortion, with foil gauge distortion is converted to electric signal output again.

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

The sensor construction form is drum type brake.It is the thin cylinder that an end has blind hole, and blind hole depth is that nose end has screw thread to be connected with oil hydraulic system about high half of tube.Respectively be pasted with two foil gauges on the hollow parts of circular hole and the outer wall of solid section, sensitive grid direction and axis normal, and be connected into bridge circuit by Figure 12 (b).When the inner chamber oil pressure increased, thin cylinder produced dolioform distortion, and foil gauge R2 and R4 are stretched, and R1 and R3 are constant, only played temperature compensation function.During work, a, the b termination power, then at c, the output voltage signal of d end is directly proportional direct ratio with deflection, thereby also is directly proportional with pressure.

Because testing machine in the course of the work, the temperature of oil can raise, and therefore, sensor should can be stablized in certain temperature range, operate as normal.

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 when particularly measuring big the load, more seems small and exquisite easy.Its shortcoming be precision less than the load sensor height, the dynamometry error ratio is bigger when the friction force between piston and oil cylinder is big ^[8]In order to reduce the measuring error of pressure transducer as far as possible, need when the power of demarcation value, get calibration point as much as possible, especially in the small value force section.

The fuel injection pressure signal actual measurement be pressure, structure according to testing machine, the actual pressure that should be the 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 magnitude of voltage after the signal process of pressure transducer output is amplified, k and g ask method: adopt 2 different values of thrust: the F1 of tension tester (non-tension measuring device of the present invention, but the tension measurement instrument of standard) actual measurement and the F2 that have calibrated, record this two value of thrust corresponding voltage value V1 and V2 again, with this 2 class value substitution F=kV-g, can try to achieve k and g.

Displacement measurement

In test, the superpolymer test specimen is stretched and will ruptures behind about 30-80mm.Therefore the measurement range of system requirements displacement is that 0-100mm and resolution are 0.1mm.Though accuracy requirement is not very high, the general linear displacement transducer still can not meet the demands.Though the grating chi can satisfy the requirement of range and measuring accuracy, it is not too convenient to install in transformation.Therefore adopt photoelectric encoder to realize the measurement of displacement in the native system.

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

According to scale method and the signal output form that light is deleted 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 mutually; A, B two group pulse phase differential 90 degree, thus can judge sense of rotation easily, and Z is pulse of revolution mutually, is used for the reference point location.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 the reliability height is suitable for long Distance Transmission.Its shortcoming is the absolute location information of can't output shaft rotating.

(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 the disk, lighttight bargraphs, and absolute encoder can have some codings, according to the coding of reading on the code-disc, detect the absolute position.

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

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

Photoelectric encoder is selected HTR-3A-1000 type photoelectric encoder [10] for use, and its resolution can reach 1000 pulse/circles.It is 15.92mm that the pulley of installing on the photoelectric encoder output shaft obtains its value footpath D through Precision Machining, and then 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 satisfies resolution greater than the designing requirement of 0.1mm.

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

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

2, with the hydraulic oil pump switch opens of testing machine, when temperature is lower than 10 ℃, need preheating to begin test after 10 minutes again; The opening control power supply;

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

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

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

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

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

8, after test specimen is broken, click test and stop, then test is finished;

9, in the entire test, can click time-out, begin to control the time-out of test or restart test.

The three number word selecting sides (being A, B, C) of 3 multi-way switchs corresponding [namely 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, has 3 number word selecting sides (S0 to S2 also is A, B, C end), 1 low effective Enable Pin (E), 8 independent I/O ends (Y0 to Y7) and 1 public I/O end (Z).When E is low, one of them of 8 switches will be chosen (low resistance state) by S0 to S2.When E was high, all switches all entered high-impedance state, directly ignored S0 to S2.VCC1＝20V

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

53 D weak magnetic field sensor groups that HMC2003 among the figure (1-5) is made up of 5 HMC2003, this is the core cell of whole sensor, its arrangement mode is as shown in Figure 2; MUX is made up 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 enters 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, and it selects control to be carried out by single-chip microcomputer, and single-chip microcomputer adopts the STC89C54RD+ 8-bit microcontroller, change A, B, the state of C, can realize any one sensors X, Y switches in the time of the Z signal, i.e. each sensors X, Y, the Z output signal is to arrive analog to digital converter simultaneously, and analog to digital converter is ADS7825 sixteen bit A/D converter, and four input end IN0 are arranged, IN1, IN2, as long as IN3 is four passages of timesharing gating, just can realize the conversion of input analog amount, native system is selected IN0 for use, IN1, and three input ends of IN2 are respectively as X, Y, the signal input part of Z 3 D weak magnetic field.

It is that sensor is magnetized and reduces forward and reverse polarization pulse generation circuit of measuring sensitivity and arranging in the magnetic-field measurement process in order to eliminate 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 that is sent by single-chip microcomputer, the RESET signal controlling.

Before the A/D conversion beginning, export a SET signal earlier, make sensor obtain the forward polarization, then start A/D converter and carry out the A/D conversion, in order to prevent that random disturbance from causing the 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 100 A/D conversions again, and average, then the mean value of twice acquisition is obtained a numerical value as a measured value through numerical evaluation VOUT=(AVG1+AVG2)/2, when the three dimensional signal of a sensor all disposes, then finished the three-dimensional magnetic field of a point and measured, after all finish the three-dimensional magnetic field of 5 sensors, just finished the measurement of frame data.After single-chip microcomputer is finished 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, then form sends frame data by appointment, finish after the data transmission, single-chip microcomputer enters the next employing cycle.Serial communication is made of private communication device MAX232.

HMC2003 is three-dimensional high sensitivity magnetic field survey sensor among the figure, 5 HMC2003 are according to arrangement shown in Figure 2, hysteresis effect is eliminated peripheral circuit and is cooperated with HMC2003 internal pulses degaussing circuit, finishes 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 constitute, multi-way switch is the three-dimension sensor channel selector switch, X with 5 three-dimension sensors, Y, the 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.

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

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

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

Three-dimensional precision instrument amplifier amplifies output with 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 the most highly sensitive state that bridge is in no hysteresis effect all the time, is used for eliminating hysteresis effect to measuring the influence of sensitivity.

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

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

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

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

That the giant magnetoresistance sensor among the design is selected for use is HMC2003, this class magnetoresistive transducer is by 4 element wheat stone bridge configuration, have integrated set/reset band, can reduce temperature drift effect, nonlinearity erron and because the existence of highfield, the losing of the output signal that causes.And have integrated biasing band, can eliminate the influence that hard iron disturbs.Three-D magnetic field sensor HMC2003 can measure three-dimensional (x, y, z) direction of Weak magentic-field.

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

The background magnetic field cancellation techniques

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

Apply the compensating field and eliminate background magnetic field and bring by bias current and compensate, the bias current band can also drive current by the 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 the magnetic field equidirectional.The electric current band of HMC2003 whenever can provide the magnetic field of 10e by the 50mA electric current, the electric current band of HMC2003 whenever can provide the magnetic field of 10e by the 5mA electric current.(1 Gauss in the air=10e).The bias current band appear to one the biasing+and biasing-pin between nominal resistance.

The bias current band can be as the feedback element in the closed loop circuit.Utilize the bias current band in the current feedback loop can measure expectation value.If will reach this purpose, the output terminal of amplifier of electrical bridge is connected to the current source that drives the bias current band.Utilize high-gain and reverse feedback in the loop.This will make the magnetic resistance bridge circuit be output as 0 (output +=output-).This method can provide the splendid linearity and temperature characterisitic, operates magnetoresistive bridge with the resistance mode of balance all the time.That is, no matter measure which type of magnetic field, all can be with 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.

The forward polarization is eliminated hysteresis effect with reverse polarization

Most of downfield sensors can be subjected to big magnetic interference (＞4～20 Gauss's) influence, may cause the decay of output signal.In order to reduce the output of this influence and maximum signal, can use the magnetic switch handoff technique in magnetoresistive bridge, eliminated the influence 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 big pulsation of current by S/R electric current band.S/R electric current band looks like a resistance that is added between SR+ and the SR-pin.This electric current band is different with the bias current band, because it is magnetically coupled on the magnetoresistive transducer with Z-axis or insensitive direction.In case sensor is set (or resetting), can realize low noise and highly sensitive magnetic-field measurement.

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

S/R in the 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 average power consumption is less than 1mA (DC) during continuous impulse.Can be chosen to be every 50ms has the pulse of 2 μ s pulsewidths, perhaps longer, with 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 then impulse attenuation should not be lower than 0 electric current.Any negative (being lower than rated current) current pulse signal all can cause " can't set " sensor, and can not obtain best sensitivity.

Utilize S/R electric current band, can eliminate or reduce many influences, comprising: temperature drift, non-linear mistake, intersecting axle influence and because the existence of highfield losing of causing that signal exports.

The principle of 3 D weak magnetic field is to utilize the giant magnetoresistance resistance to change along with the variation in magnetic field, and the variation that will record resistance, the variation that can survey its output voltage then for particular current of resistance, because what we surveyed is voltage, so electric current is a steady state value preferably, so could not influence the linear changing relation between voltage and the resistance, and to constant current source of resistance, just can avoid electric current to be subjected to the influence of resistance variations, thereby avoid the influence of power-supply fluctuation to 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 the A point voltage is unaffected, so constant, corresponding B point voltage is also constant, so obviously can get electric current I _CConstant output.Field effect transistor in the 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 eliminate circuit for magnetic field effect 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 by Single-chip Controlling output, to be converted into pulse signal by peripheral circuit then.Be exactly the set/reset pulsing circuit that utilizes IRF7106 to produce as shown in Figure 7.

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

As the i.e. set8 among the figure of set[] when 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) also are low levels, the conducting of P-channel field-effect transistor (PEFT) pipe, the D2 end has inverse current output, and when capacitor C 81 chargings finished, 4 pins of IRF7106 became high level again, the P-channel field-effect transistor (PEFT) pipe ends, no current output is so when set put 1, SR+8 had the output of reverse impulse electric current.

As the i.e. reset8 among the figure of reset[] when putting 1 (high level), the conducting of N channel field-effect pipe, the D1 end has forward current output (being assumed to be 1), and again because output terminal has capacitor C 83, so have only 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 satisfied 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, and three giant magnetoresistance sensors are arranged in the three-D magnetic field sensor, only analyzes the peripheral circuit of a giant magnetoresistance sensor here.

When DC current in the bias current band by the time bias current band multiple mode of operation can be arranged.

(1) balances outside unwanted magnetic field.

(2) the electric bridge biasing is set to zero.

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

The bridge circuit gain can be calibrated in the system automatically when (4) receiving order.

The bias current band will produce a magnetic field opposite with tested magnetic direction when the electric current of specific size is tided over the bias current band, so can eliminate any environmental magnetic field.The bias current band whenever can provide the magnetic field of 10e by the 50m electric current.

Based on the characteristic of above bias current band, the biasing band can be as the feedback element in the closed loop circuit.In this kind application, the output terminal of amplifier of electrical bridge is connected on the drive current source of biasing band, utilizes high-gain and negative feedback in one tunnel to make electric bridge be output as zero.No matter measure which type of magnetic field, all can be with 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 the external magnetic field is one of this magnetic field directly tolerance, and can be directly changed into magnetic field value.

The bias current band can also be used to calibrating automatically magnetoresistive bridge, and it is very useful to proofreading the electric bridge gain once in a while or adjusting in big temperature pendulum scope.Can power on or normal running during whenever carry out.Its principle is: get 2 points along a circuit, and determine the gradient of this line, be i.e. gain.When electric bridge was being measured stable external magnetic field, output was handed over and is kept constant.The reading of record stabilizing magnetic field is designated as H1. and applies specific currents at this moment by the bias current band, records this reading then, is 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), the magnetoresistive transducer gain can followingly be calculated:

Gain＝(H2-H1)/ΔHa.

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

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

The output port of these two voltage followers is received the HMC2003 background magnetic field respectively to two ends Xoff+1 and the Xoff-1 of 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 effect of voltage follower be buffer compartment from, so background magnetic field can not be subjected to influence circuit to the voltage at canceling coil two ends, so just can provide stable " compensating field " to giant magnetoresistance sensor.

The data acquisition system (DAS) explanation

The design mainly finishes sensor and periphery circuit design, but the 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 control principle and the work schedule of sensor, now data collection and control section are briefly introduced, make the thinking of design more clear.

It is collection control, the A/D conversion and the mini system of communicating by letter of core with the single-chip microcomputer that data acquisition system (DAS) among the design is one.

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

This data acquisition circuit figure comprises following three parts.

The A/D analog to digital converter

In the design, select for use 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 by the power supply of list-5V power supply, can import-aanalogvoltage of 10V～10V.Data after the A/D conversion are line output also, also serializable output, and data transfer module also can be set to the continuous cyclic transformation of 4 interchannels, and it is extremely convenient to use.

When using the ADS7825 chip, will

Put 0, give then

Pin adds a negative edge namely can start the AD conversion.At this moment,

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

Before pin is output as high level,

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

Since the ADS7825 data converted can and line output, also serializable output is so reading of data also must divide parallel and the serial dual mode is discussed.Among the design be with

Be set to high level, select the parallel way of output for use, so will when data read

Pin is put low level, namely choose the ADS7825 chip after, give

Pin is imported a negative pulse, starts the AD conversion.AD conversion and the data time of latching are 25 μ s.Detect

The output level of pin can the judgment data transition status, works as state flag bit

The time, data-switching is still being carried out, and not can read data this moment.

The time, showing that data-switching has finished and data have entered output register, can read data this moment.Make parallel data output select position BYTE=0, can read the most-significant byte data, BYTE=1 reads the least-significant byte data.

Simulating signal by mode and the address of ADR0, ADR1 and CONTC pin affirmation conversion, when CONTC=1, is selected continuous translative mode respectively from IN0, IN1, the input of IN2 pin, when When being low level with the PWRD end, AD conversion and reading will circulate continuously at four interchannels of IN0～IN3 and carry out.When

After this EOC transfers high level to, A0 and A1 pin will be exported the used channel address of sampling next time, from which input channel begin to carry out cyclic transformation actually, depend on that CONTC is set to before the high level, the input value of A0 and A1 pin.The output of A0 and A1 pin and the relation that is sampled between the passage are listed as 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 as table 5.1.2 are listed

Among the design, ADR0, ADR1, CONTC,

Pin all is by the control of single-chip microcomputer output signal, so its conversion regime should also be 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 circulate continuously at IN0, IN1, three interchannels of IN2 to carry out.So should select continuous translative mode, and the initial value of A1, A0 is set to 01 before each circulation, so that circulate when beginning, data begin conversion from the AIN0 passage.When AIN2 passage EOC, immediately will

Put lowly, stop conversion, and next time circulation of beginning.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 the microcomputer.This system is by CPU, access data storer, read-only program memory, imput output circuit (I/O mouth) immediately, might comprise that also circuit such as Timer, serial communication port, display driver circuit (LCD and led drive circuit), pulse-width modulation circuit, analog multiplexer and A/D converter are integrated on the monolithic chip, have constituted a minimum but perfect computer task.Single-chip microcomputer will use specific group to translate and the composing software program compiler, with keiluvision2 program is being downloaded in the single-chip microcomputer.

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

Wherein P0 is one group of two-way I/O mouth of 8 open-drain types, also is multiplexing mouthful of address/data bus.Here as the digital signal acquiring mouth.The P1 mouth is 8 two-way I/O mouths of a band internal pull-up resistor, and the output buffer stage of P1 can drive 4 TTL logic gates.In the design, the P1 mouth is that wherein P1.0～P1.5 is to analog-to-digital control as the control delivery outlet, 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 the serial input/output port,

RST is the input that resets.When oscillator is worked, two above high level of machine cycle appear in the RST pin will make single-chip microcomputer reset.

When visit external program memory or data-carrier store, ALE output pulse is used for the least-significant byte byte of latch address.Generally speaking, the pulse signal that ALE still fixes with 1/6 output of oscillation frequency clock, so it can externally be exported clock or be used for regularly purpose.

Program stores and allows

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

Effectively, namely export two pulses.

For external reference allows.Desire to make CPU only to visit 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 for use this serial port, and it is level and Transistor-Transistor Logic level conversion driving circuit.Chip commonly used is MAX232, and the advantage of MAX2321 is:

(1) a slice chip can be finished 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.

The MAX232 chip is that U.S. letter company is the interface circuit of the rs-232 standard serial ports design of computer specially, and use+5V single power supply can be realized 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 used for the supply voltage conversion, as long as externally insert corresponding electrochemical capacitor; Pin 7-10 and pin 11-14 constitute the change-over circuit of two groups of TTL signal levels and RS-232 signal level, and corresponding pin can directly link to each other 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 of gathering three-dimensional, so when sampling, should gather the data of X, Y, Z-direction respectively, 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, the conversion of passage 3 gatings.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 be 8 circulations, controlled so will export three bytes of ABC by single-chip microcomputer.

4 sensors of four jiaos, it is horizontal, and longitudinal pitch should be arranged in the maximum zone of sheet material drawing process distortion in theory, and the design obtains according to experimental summary, gets laterally=40mm, vertically=35mm

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

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

Claims

1. many couplings of thermic magnetic effect integrated test facility is characterized in that, sample holder is contained between the upper grip and lower chuck of hydraulic extension test machine; The centre of sample has a hole; Adopt host computer and lower computer mode 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 with communicate to connect as the controller of slave computer,

Test process is:

2. many couplings of thermic magnetic effect according to claim 1 integrated test facility is characterized in that, adopts sectional type PID control strategy control draw speed;

3. many couplings of thermic magnetic effect according to claim 1 and 2 integrated test facility is characterized in that, adopts based on many coupling integrated test systems of thermic magnetic effect and implements integration test;

Hydraulic control device drives the hydraulic extension test machine;

Controller and host computer communicate to connect;

4. many of thermic magnetic effects according to claim 3 coupling integrated test facility is characterized in that, tension measuring device is measured in the oil cylinder of hydraulic extension test oil pressure with the pulling force of indirect measurement clamping part to sample by strain pressure transducer; Strain pressure transducer is cylinder mode, and the strain pressure transducer main body is a cylinder that has an axial blind hole, and the openend of cylinder is provided with for the external thread that connects 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, and R2 and R4 are laterally concordant and be positioned at the blind hole section outside of cylinder, laterally refer to cylinder radially;

Three number word 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 thermic magnetic effect, be integrated with described host computer and controller in the described switch board, described host computer is industrial computer, described controller is the ARM embedded control system, the top of switch board is provided with the display that connects industrial computer, be provided with plug-type finger-board in the switch 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 have be used to the interface that is connected 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 couplings of thermic magnetic effect according to claim 4 integrated test facility is characterized in that, controller is as follows by the method that the three-dimensional magnetic field measurement mechanism detects the three-dimensional magnetic field:

Described and folk prescription to referring to x, y or z direction.

6. many couplings of thermic magnetic effect according to claim 5 integrated test facility 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 per 0.5 second once sampling.