CN108645556A - A kind of tractor resistance detection device - Google Patents
A kind of tractor resistance detection device Download PDFInfo
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- CN108645556A CN108645556A CN201810911532.9A CN201810911532A CN108645556A CN 108645556 A CN108645556 A CN 108645556A CN 201810911532 A CN201810911532 A CN 201810911532A CN 108645556 A CN108645556 A CN 108645556A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/12—Measuring force or stress, in general by measuring variations in the magnetic properties of materials resulting from the application of stress
- G01L1/127—Measuring force or stress, in general by measuring variations in the magnetic properties of materials resulting from the application of stress by using inductive means
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Abstract
The invention discloses a kind of tractor resistance detection devices, incude shell including shearing force, the shearing force induction enclosure is provided with electrical signal conversion device, and the electrical signal conversion device is set as piezomagnetic force snesor, and the piezomagnetic force snesor is connected with electric signal output control circuit.Tractor resistance detection device provided by the invention can accurately incude the resistance suffered by tractor, and feedback is more accurately realized in resistance control system, and then keep electrohydraulic hitch system sensitiveer and accurately realize control.
Description
Technical field
The present invention relates to field of agricultural machinery, more particularly to a kind of tractor resistance detection device.
Background technology
In order to adapt to various farm implements and its different operating conditions, three are generally used on current most of wheeled tractors
Kind regulative mode：Power is adjusted, position is adjusted, height is adjusted, Tractor Abroad additionally used torque adjusting in recent years, pressure is adjusted,
Comprehensive adjustment.Power adjusting is for the purpose of maintaining tractor engine load steady, and the tractive force for adjusting farm implements is to pass through
For resistance control system come what is realized, resistance control system is a very important subsystem of electrohydraulic hitch system.Traditional
Tractor uses the power that simple hydraulic device is promoted as farm implements, and control section is mechanical, passes through manipulation by driver
Handle and a set of rod piece mechanism input signal in the form of displacement, output quantity are then to adjust thick stick by spring, cam and power, position
The displacement that linkage is converted into, to realize the adjustment for manipulating main control valve to farm implements position.The hydraulic suspension of Mechanical course
System uses rod piece and elastic element, and structure is more complicated, and sluggishness, mechanical friction and the breathing of rod piece of elastic element can influence
Regulation performance, and due to being influenced by the uncertain factors such as non-linear of the changing of edaphic condition, hydraulic lift mechanism, traditional liquid
Press the work quality of suspension mechanism not high, therefore the precise control model for causing system is established relatively difficult, and is unfavorable for
Realize the automation and intelligence of tractor set operation.Currently, the hydraulic suspension that electrohydraulic hitch system has replaced tractor traditional
Suspension mechanism.
But the most important problem of setting of electrohydraulic hitch system is how to establish mechanical displacement and tractor at present
Resistance situation lacks a kind of tractor resistance detection device to the conversion of electric signal, can accurately incude suffered by tractor
Resistance, feedback is more accurately realized in resistance control system, and then keep electrohydraulic hitch system sensitiveer and accurately
Realize control.
Therefore those skilled in the art are dedicated to developing a kind of tractor resistance detection device, can accurately incude tractor
Suffered resistance, more accurately in resistance control system realize feedback, and then make electrohydraulic hitch system it is sensitiveer and
Accurately realize control.
Invention content
In view of the drawbacks described above of the prior art, technical problem to be solved by the invention is to provide a kind of tractor resistances
Detection device can accurately incude the resistance suffered by tractor, and feedback is more accurately realized in resistance control system, into
And keeps electrohydraulic hitch system sensitiveer and accurately realize control.
To achieve the above object, the present invention provides a kind of tractor resistance detection devices, including shearing force to incude shell,
The shearing force induction enclosure is provided with electrical signal conversion device, and the electrical signal conversion device is set as piezomagnetic power biography
Sensor, the piezomagnetic force snesor are connected with electric signal output control circuit.
Preferably, the shearing force induction shell is set as round pin shape；
The shearing force induction shell is internally provided with endoporus；It is provided with pressure sensor in the endoporus；
The pressure sensor includes excitation magnetic core, and excitation magnetic core setting is sheared described in face inside the endoporus
The position of concentration zones, the excitation magnetic core left and right sides are provided with induction magnetic core, longitudinal profile where the induction magnetic core magnetic pole
It is in 90 ° with longitudinal profile where the magnetic pole of induction magnetic core；The magnetic pole of the induction magnetic core is located at shearing concentration zones；The excitation magnetic
Core and induction magnetic core form cylindrical entirety, are fitted close with the endoporus；Setting is fluted in the middle part of the shearing force shell；Institute
It states and is provided with fixing device between the induction magnetic core outside excitation magnetic core, the fixing device includes excitation magnetic core enclosure
And fixed part, the fixed part are matched with the fixed groove of the shearing force shell initiating terminal；The shearing force casing ends
It is provided with chamfering.
Preferably, the electric signal output control circuit include master controller, power system circuit, communication system circuit,
Clock system circuit resets circuit system, signal amplification and signal effective value transformation circuit system.
Preferably, the power system circuit includes prime power circuit and final stage power circuit；The front stage circuits are real
Existing conversion of the 24V voltages to 5V voltages；The final circuit realizes conversion of the 5V voltages to 3.3V voltages.
The front stage circuits, which are also realized, converts 24V voltages to 15V；The final circuit, which is also realized, converts+15V voltages
For -15V voltages.
Preferably, the front stage circuits include three proper voltage voltage stabilizing chips and output voltage chip；Described three rectify electricity
Voltage stabilizing chip is pressed to use L7815；The output voltage chip uses DCDC_S5；The final circuit includes that charge pump voltage is anti-
Turn device and low voltage difference analog power；The charge pump voltage inversion device is set as ICL7662CPA；The low voltage difference analog power
It is set as SPX1117；The power system circuit further includes AD conversion a reference source potential circuit, including a reference source voltage output core
Piece, a reference source voltage output chip are set as AD530ART.
Preferably, the clock system circuit includes the external crystal-controlled oscillation that crystal oscillator frequency is 11.0592MHz；The reset system
Circuit of uniting includes reset chip, and the reset chip is set as CAT1021；The signal amplification and effective value transformation circuit system
Including instrumentation amplifier；The instrumentation amplifier is set as INA114；The signal amplification and effective value transformation circuit system packet
Include A/D converter；The A/D converter is set as AD736.
Preferably, the communication system circuit includes one or more below, serial communication circuit, CAN communication circuit.
The serial communication circuit includes level translator, signal transmitting and receiving chip；The level translator uses RS-232；
The signal transmitting and receiving chip uses SP3232；The CAN communication circuit includes CAN controller, and the CAN controller is integrated to be followed
The CAN protocol of CAN specifications V2.0B；The CAN controller uses LPC2378.
The beneficial effects of the invention are as follows：Tractor resistance detection device provided by the invention, can accurately incude tractor
Suffered resistance, more accurately in resistance control system realize feedback, and then make electrohydraulic hitch system it is sensitiveer and
Accurately realize control.
Description of the drawings
Fig. 1 is the structural schematic diagram of the embodiment of the invention.
Fig. 2 be in Fig. 1 B to sectional view.
Fig. 3 is installation site figure of the resistance detection device in electrohydraulic hitch system of Fig. 1.
Fig. 4 is the equivalent circuit diagram of resistance detection device.
Fig. 5 is electric signal output control circuit composition figure.
Fig. 6 is front stage circuits hardware elementary diagram in electric signal output control circuit.
Fig. 7 is final circuit hardware elementary diagram in electric signal output control circuit.
Fig. 8 is a reference source potential circuit hardware elementary diagram in electric signal output control circuit.
Fig. 9 is reset and storage circuit hardware elementary diagram in electric signal output control circuit.
Figure 10 is signal amplification and effective value transformation hardware circuit principle figure in electric signal output control circuit.
Figure 11 is CAN message transmission flow figure.
Figure 12 is that CAN message receives flow chart.
Figure 13 is the receive process figure of CAN data.
Figure 14 is the initialization of CAN communication link.
Figure 15 is the transmitting-receiving flow chart of serial communication.
Specific implementation mode
The invention will be further described with reference to the accompanying drawings and examples：
As shown in Figure 1 to Figure 2, a kind of tractor resistance detection device, including shearing force incude shell 1, shearing force induction
Shell 1 is internally provided with electrical signal conversion device 2, and electrical signal conversion device 2 is set as piezomagnetic force snesor, and piezomagnetic power passes
Sensor is connected with electric signal output control circuit.
Further, shearing force induction shell 1 is set as round pin shape；Being internally provided with for shearing force induction shell 1 is interior
Hole 4；Pressure sensor 5 is provided in endoporus 4；Pressure sensor 5 includes excitation magnetic core 6, and excitation magnetic core 6 is arranged inside endoporus
Face shears the position of concentration zones 3, and 6 left and right sides of excitation magnetic core is provided with induction magnetic core 7, and 7 magnetic pole of induction magnetic core place is longitudinal
Section and longitudinal profile where the magnetic pole of induction magnetic core are in 90 °；The magnetic pole for incuding magnetic core 7 is located at shearing concentration zones；Excitation magnetic core 6
Cylindrical entirety is formed with induction magnetic core 7, is fitted close with endoporus 4；The 1 middle part setting fluted 8 of shearing force shell；Excitation magnetic core
Fixing device 9 is provided between 6 outsides and induction magnetic core 7, fixing device 9 includes excitation magnetic core enclosure 91 and fixed part 92,
Fixed part 92 is matched with the fixed groove 10 of 1 initiating terminal of shearing force shell；1 end of shearing force shell is provided with chamfering.
Since the output signal of sensor is related with the variation of magnetic flux in magnetic circuit, so the direct shadow of the rational design of magnetic circuit
Ring the size of sensor output signal.Magnetic Circuit Design seeks to reduce magnetic dispersion to the greatest extent, improves electricity-magnetic transfer efficiency, keeps away as possible
Exempt to generate the eddy current magnetism etc. that stray magnetic fields such as current vortex generates in device operation, improves the equal of magnetic field residing for magnetic material
Even property etc..So the mechanism of piezomagnetic force snesor should be close, material magnetic characteristic variation should be apparent.
The selection of the intensity of magnetization will influence the sensitivity of sensor, so according to the typical magnetization characteristic of ferromagnetic material
With the relationship of magnetic conductivity and magnetic field intensity, the region for selecting magnetization characteristic more sensitive is more conducive to sensor.Due in sensor
In the course of work, by shearing force, the magnetic conductivity of measured material is existing under tension and compression state to be increased and has reduction area sensor
Domain, and according to the magnetization characteristic of ferromagnetic material, the additional excitation intensity of magnetization had better not be more than the saturation magnetization of material,
Otherwise, material embodies the telescopic deformation of volume.So the selection of magnetic field intensity should be between minimum magnetic conductivity and maximum magnetic conductance
And positioned at the big ascent stage of permeability curcve variation tendency in figure.Increase the tolerable bigger exciting current of coil line footpath to pass through,
The intensity of magnetization can then be increased by increasing coil turn.
But due to the limitation of permeability magnetic material physical arrangement, by magnetic flux can not possibly infinitely increase, pass through certain body
The magnetic flux of product permeability magnetic material is greatly to after certain amount, no matter being further added by electric current or the number of turns, magnetic flux is not further added by, at this moment
Permeability magnetic material has reached magnetic saturation.So when selecting the core material of sensor, be considered as high with magnetic permeability, loss is small,
Material of the line segment of magnetization curve compared with performances such as wide, the big, magnetic stabilities of resistivity.Magnetic core uses stacked magnetic core, between two layers
Appropriate gap can reduce the inductance value of coil, avoid direct current cable order magnetic core from being saturated, while stacked high resistivity magnetic core can
Energy loss caused by prevent the generation of vortex or reduce vortex.
Core material can influence the magnetic induction intensity in magnetic field, so selecting suitable core material for output signal
Power has a certain impact.After preliminary screening, the common magnetic core high resistivity material iron of the domestic performance stabilization of core material selection
Nickel alloy and silicon steel sheet, by the further comparison of two kinds of materials, the advantages of iron-nickel alloy is that have high magnetic under downfield
Conductance and very low coercivity.The processability of iron-nickel alloy is good, and variously-shaped complicated, size can be made and require accurate member
Part.Compared to silicon steel sheet B30P110, iron-nickel alloy 1J85 have very high initial permeability, high resistivity, extremely low coercivity and
Very high maximum permeability, is quick on the draw to small-signal, and saturation induction density is low.According to the comparison of two kinds of materials, this reality
Applying example can select permalloy 1J85 as core material.
Since the coil wound on sensor magnetic pole will produce magnetic flux edge effect during the work time, i.e., closer to coil
The region at both ends, magnetic induction line more dissipate.Magnetic induction line diverging is unfavorable for the variation of induction coil induced flux, in order to reduce magnetic flux side
The influence of edge effect should increase magnetic pole face size as possible, reduce magnetic pole pitch.So the internal structure of piezomagnetic force snesor
It should coordinate between external structure closely, distance is unsuitable too far between excitation pole and induction magnetic pole.
According to the above analysis, the basic structure size and pictorial diagram of excitation magnetic core are as shown in Fig. 3-3.It is wound on excitation magnetic core
The enameled wire of a diameter of 0.21mm, totally 240 circle.When exciting current passes through magnet exciting coil, a size will be generated with excitation electricity
Changing magnetic field is flowed, the magnetomotive force in this magnetic field is
e0=N0I0 (3-1)
N in formula0For magnet exciting coil the number of turns；I0For exciting current.
Basic structure size and the pictorial diagram for incuding magnetic core are as shown in Figure 3-4.It is twined on each of induction magnetic core induction magnetic pole
Around the enamel wire coil that 90 circle line footpaths are 0.11mm.When magnetic field changes, the variation of induction coil induced flux generates sense
Answer electromotive force.
Sensor internal mechanism is packaged into an entirety with duroplasts, such as both fixed relative position, such as Fig. 1 to Fig. 2
Shown, longitudinal profile where excitation magnetic core magnetic pole and longitudinal profile where the magnetic pole of induction magnetic core are in 90 °, and internal structure is integrally done
It at cylinder, is fitted close with centrepin endoporus, installation diagram is as schemed；The magnetic pole of internal excitation magnetic core is located at shearing concentration zones,
Induction magnetic pole is located at shearing concentration zones both sides.Fixing device in figure, the hard plastic body head for encapsulating internal element are stretched out
In one positioning protrusion insertion centrepin head edge positioning groove.
Such as Fig. 2, when non-stress, a symmetric magnetic field, each section of magnetic resistance phase of pin surfaces are formed between primary coil the two poles of the earth
Deng, equal by the magnetic flux of induction coil, since coil E1, E2 are reversely concatenated, E3, E4 are reversely concatenated, two groups of positive concatenations again,
Differential connection is formed, so magnetic flux is cancelled out each other, sensor output is zero；When axis is by shearing force, intrinsic isotropism
The magnetism of magnetic material will change, and then magnetic field reforms into asymmetry, generate to draw in 45 ° and 135 ° of its surface direction and answer
Power and compression.According to ferromagnetics, as the saturation magnetostriction constant λ of steel materialS＞ 0, then in the magnetic bullet in tensile stress direction
Performance is minimum, is direction of easy axis, i.e., magnetic conductivity increases, and magnetic resistance reduces；And in compression direction, magnetic conductivity reduces, and magnetic resistance increases
Greatly.Therefore, the Φ values variation at E1, E2, E3, E4, then sensor has induction voltage output, can by the calibration to sensor
The relationship for obtaining induced voltage and stress, so as to which lifter is promoted or reduced according to the size of tractive resistance and variation,
To keep the stabilization of engine load.
Red line indicates that tension, magnetic conductivity increase, and magnetic resistance reduces, and magnetic flux increases；Blue line indicates to be pressurized, and magnetic conductivity reduces, magnetic
Resistance increases, and magnetic flux reduces.
As the magnetic circuit of sensor can be equivalent to shown in Fig. 4 equivalent by Fig. 4 according to the principle Analysis of force snesor
Magnetic circuit.R1, R2, R3, R4 be respectively magnetic flux flow through four induction magnetic pole magnetic resistance (including induction core reluctance, induction magnetic pole with
Measured surface air-gap reluctance and corresponding measured surface section magnetic resistance), R5 be measured material surface without induction magnetic pole that
It is the resistance that magnetic flux flows through excitation pole to divide the magnetic resistance of magnetic flux, R0.In calculating process, because the magnetic flux Φ 5 for flowing through R5 is comparatively small,
So ignoring.
Not to centrepin applied force or it is static when, by magnetic circuit symmetrically known to Φ 1=Φ 2=Φ 3=Φ 4, connected according to magnetic flux
Continuous property principle has Φ 0=Φ 1+ Φ 2+ Φ 3+ Φ 4, for taking a closed magnetic circuit.According to Ampère circuital theorem and magnetic circuit ohm
Law has
e0=N0I0=R0φ0+R1φ1=(4R0+R1)φ1 (3-19)
In formula
E0-magnetomotive force；
R0, r1-are respectively excitation pole and incude the air-gap reluctance of magnetic pole E1；
The magnetic resistance of excitation pole in R0-loop；
The equivalent magnetic resistance of magnetic core is incuded in RE1-loop；
Measured surface E1-O2 sections of magnetic resistance in RC1O-loop；
Measured surface O1-E2 sections of magnetic resistance in RCO1-loop.
The magnetic conductivity relationship of magnetic resistance and material is
In formula
L-is the length of magnetic path of magnetic core and measured material；
μ-is the magnetic conductivity of magnetic core or measured material；
S-is the magnetic circuit sectional area of magnetic core or measured material.
Formula 3-21 is substituted into formula 3-20 and is obtained
In formula
Air gap under 0-excitation poles of δ；
δ 1-incudes the air gap under magnetic pole E1；
μ 0, μM, μ C-be respectively air, magnetic core, measured material absolute permeability；
S0-excitation pole end on projection and magnetic flux are in each area of section of excitation pole；
S1-induction magnetic pole end on projection and magnetic flux are in induction each area of section of magnetic pole；
The area of section that SC1O-magnetic flux is flowed through to the ends excitation pole O2 in measured surface from induction magnetic pole；
The area of section that SCO1-magnetic flux is flowed through from the ends excitation pole O1 to induction magnetic pole in measured surface；
N0-magnet exciting coil the number of turns；
L0, l1-are respectively excitation magnetic core in closed magnetic path, incude the length of magnetic path of magnetic core；
The length of magnetic path that lC1O-magnetic flux is flowed through to the ends excitation pole O2 in measured surface from induction magnetic pole；
The length of magnetic path that lCO1-magnetic flux is flowed through from the ends excitation pole O1 to induction magnetic pole in measured surface；
According to the symmetry of magnetic circuit, lCO1 ≈ lC1O, SCO1 ≈ SC1O, δ0≈δ1, enable Then
Then
φ1=KMe0=KMN0I0 (3-24)
When centrepin bears shearing force, 45 ° and 135 ° of surface direction generates tension and compression stress, the magnetic conductivity on corresponding surface
It increases separately Δ μ C or reduces Δ μ C, then four induction coils output induced voltage is respectively+Δ U and-Δ U.
Flow through Φ 1 and Φ 2 according to the symmetry of induction magnetic core, at E1 coils, Φ 1,2 directions Φ on the contrary, and active force such as
When figure, μ C1=μ C- Δ μ C, μ C2=μ C+ Δ μ C, Φ 1 is reduced, Φ 2 increases, then
Since tension and compression stress absolute value is equal,And magnetic core and axis are transition matching relationship, magnetic gap becomes
It is comparatively small to change influence, it can be by δ0Regard constant as, then the induced electromotive force that E1 coils generate is：
Similarly
Because induction coil is differential connection, so the output voltage of sensor is：
When loading static force
At this point,It is related with the variation of the magnetic conductivity of measured material and derivative of current.When sensor exciting current is sinusoidal letter
Number I0=i0When sin ω t, sensor output voltage is：
Further, electric signal output control circuit include master controller, power system circuit, communication system circuit, when
Master slave system circuit resets the amplification of circuit system signal and signal effective value transformation circuit system.
Further, power system circuit includes prime power circuit and final stage power circuit；Front stage circuits realize 24V electricity
Press to the conversion of 5V voltages；Final circuit realizes conversion of the 5V voltages to 3.3V voltages.
Front stage circuits, which are also realized, converts 24V voltages to 15V；Final circuit is also realized is converted to -15V electricity by+15V voltages
Pressure.
Further, front stage circuits include three proper voltage voltage stabilizing chips and output voltage chip；Three proper voltage voltage stabilizings
Chip uses L7815；Output voltage chip uses DCDC_S5；Final circuit includes charge pump voltage inversion device and low pressure differential mode
Quasi- power supply；Charge pump voltage inversion device is set as ICL7662CPA；Low voltage difference analog power is set as SPX1117；Power-supply system
Circuit further includes AD conversion a reference source potential circuit, including a reference source voltage output chip, the setting of a reference source voltage output chip
For AD530ART.
Further, clock system circuit includes the external crystal-controlled oscillation that crystal oscillator frequency is 11.0592MHz；Reset circuit system
Including reset chip, reset chip is set as CAT1021；Signal amplifies and effective value transformation circuit system includes instrument amplification
Device；Instrumentation amplifier is set as INA114；Signal amplifies and effective value transformation circuit system includes A/D converter；A/D converter
It is set as AD736.
Further, communication system circuit includes one or more below, serial communication circuit, CAN communication circuit.
Serial communication circuit includes level translator, signal transmitting and receiving chip；Level translator uses RS-232；Signal transmitting and receiving
Chip uses SP3232；CAN communication circuit includes CAN controller, the integrated CAN associations for following CAN specifications V2.0B of CAN controller
View；CAN controller uses LPC2378.Serial communication circuit and CAN communication circuit can utilize conventional circuit to realize, here
It repeats no more.
This system design uses the ARM7-LPC2378 microcontrollers of Philips companies as main control chip, the chip
Control and the human-computer interaction demand of acquisition system can not only be met, and there is powerful network function, can realize that system is wanted
The various communication protocols asked, while its good reliability, greatly ensure that the requirement of the application of industry spot.
The control system hardware circuit design of intelligent piezomagnetic resistive force sensor mainly include power-supply system, clock system,
The design of design, the signal amplification and signal effective value transformation system of reset system and debugging interface, the design of communication system, control
System hardware system composition processed is as figure 5 illustrates.
Power system circuit：Since input power is directly from the 24V Vehicular accumulator cells on tractor, additional two on circuit
Pole pipe is to protect battery polar.By chip transformation, voltage 5V, 3.3V are provided, wherein 3.3V is that the CPU of LPC2378 chips is grasped
Make the operating voltage of voltage and I/O operation voltage and level translator SP3232, the 5V of isolation uses for peripheral interface circuit.
Signal amplification circuit and signal effective value transformation circuit are required for the reference voltage an of ± 15V, so also to be designed in system
The power circuit of one ± 15V, in addition A/D conversion circuits set a 3V reference voltage.LPC2378 chip pin interface portions
Point power supply take the scheme on total ground, and digitally, simulation and signal ground first separate respective cabling, then with 0 Ohmic resistance
Series connection is effectively reduced high-frequency noise on digitally to simulation and the interference of signal ground for ground.
This system mainly uses two-stage power supply mode, i.e. prime power circuit and final stage power circuit, prime power circuit
Function be the 24VDC supply voltages that accumulator provides to be converted to the voltage of 5VDC, for next step voltage conversion be ready,
Simultaneously also to need the component of 5VDC to provide power supply in system, while 24VDC supply voltages are converted to+15VDC；Final stage power supply
The function of circuit is that the supply voltage of 5VDC is converted to 3.3VDC to be converted to -15VDC for system power supply and+15VDC voltages
The reference voltage of ± 15VDC is provided for signal amplification circuit.
The DCDC_ of the three proper voltage voltage stabilizing chip L7815 and output 5V of output+15VDC are selected in prime power circuit
S5.LM7805 is a kind of three terminal integrated voltage stabilizer, it improves the reliability of entire control system.So-called integrated regulator is general
It refer to the integrated circuit for the unstable constant voltage through over commutation being converted into stable output voltage.This kind of device has preferable
Voltage regulation characteristic, adjustment of load characteristic, inhibit input voltage alternating component characteristic, temperature stability and overheat, overcurrent and
Safety operation area automatic protection functions.The schematic diagram of prime power circuit is as shown in Figure 6.
Select charge pump voltage inversion device ICL7662CPA that+15VDC is converted into -15VDC, low pressure differential mode in final circuit
5VDC is converted into 3.3VDC by quasi- power supply SPX1117, as shown in Figure 7.Because requirement of the system to supply voltage is relatively high, and
Power consumption is not very big, this system power supply selection low voltage difference analog power SPX1117, and feature is：Output current is big, output voltage
Precision is high, and stability is high, and has some substitute products that can directly be replaced with it, can reduce procurement risk.Although SPX1117 permits
Perhaps input voltage is up to 20V, but excessively high voltage makes the calorific value of chip rise, and the bad design of cooling system influences simultaneously
The performance of chip.In this way, it is necessary to which front stage circuits adjust, and the output of prime is selected as 5V.Select 5V as preceding step voltage
There are two reasons for output, first, this voltage meets the requirement of SPX1117, second is that many devices need 5V to power at present, and this
5V can also serve as prime and final stage.
Clock circuit：The clock circuit of system selects the frequency of external crystal-controlled oscillation for 11.0592MHz.Use 11.0592MHz
Crystal oscillator can make serial port baud rate more accurate, while can support the PLL functions inside ARM7 microcontroller chips and ISP work(
Energy.
Reset circuit system：Since the high speed of ARM chips, low-power consumption and low-work voltage cause its noise margin relatively low,
All various aspects such as the ripple of power supply, transient response performance, the stability of clock source and Power Supply Monitoring reliability also proposed more
High requirement.In order to ensure that any situation generates reliable and stable reset signal, this system selects CAT1021 reset chips, such as
Shown in Fig. 9, it has the function of that hand-reset, wherein WP allow to read and write when being low/empty.CAT1021 includes 1 accurate Vcc
Monitor slowdown monitoring circuit and 2 open-drain outputs：RESET andWhen Vcc is less than threshold voltage is resetted, RESET pins will become
For high level,It will become low level.CAT1021 contains write-protect pin (WP), if WP connection high level, writes behaviour
Work is prohibited.
JTAG debugging interfaces：Many problems are can be potentially encountered in the system development stage, need to debug program, hardware
Test.In order to facilitate exploitation, system debug circuit is devised.It is connected with ULINK by the interface circuit and can be carried out emulating
It debugs.The pull down resistor that a 10K is met on RTCK pins keeps the inside ULINK interfaces of LPC2378 after system reset enabled,
It can direct ULINK artificial debuggings.
Signal amplifies and effective value transformation circuit system：Since force snesor differential wave adjusts the simulation electricity of circuit output
It is voltage difference to press signal, very small, and the measurement range of LPC2378A/D modules is 0~3.3V, so defeated to sensor
The analog voltage signal gone out carries out signal enhanced processing and output signal range is amplified within controller measurement range.Such as
Fruit using standard operational amplifier can not only amplified signal both ends voltage, and any direct current signal, noise can be amplified
With other common-mode voltages, therefore useful measuring signal can be submerged in DC offset voltages and noise.And instrument is used to amplify
Device can well solve this problem.The main function of instrumentation amplifier is exactly to inhibit amplification common-mode DC voltage or inhibition pair
Any other voltage of two input terminal common modes simultaneously amplifies differential signal voltage, i.e. voltage difference between two input terminals.The design
The accurate instrumentation amplifier INA114 released using BURR-BROWN companies of the U.S., INA114 sizes are small, and precision is high, and price is low
Honest and clean, offset voltage is low (50 μ V), drifts about small (0.25 μ V/ DEG C), and common-mode rejection ratio is high (being 50dB when G=1000), only needs one
Non-essential resistance RG can be arranged the arbitarygainvalue G between 1 to 10000, and the relational expression of yield value and non-essential resistance is public affairs
Formula 4-1.The output signal range of sensor is proportionally amplified to 0~3V by regulation resistance RG.
Amplified signal is sent into LPC2378 after effective value transformation circuit and is handled in the design.Measure exchange
A kind of common method of signal virtual value is using the AC/DC conversion circuits of average value response, and this circuit uses integrated transporting discharging
The conversion of AC/DC is realized with diode composition precision linear rectification circuit, circuit is simple, at low cost.In scientific experiment and engineering
In practice, a large amount of non-sinusoidal waveform can be encountered.In order to realize the accurate measurement to arbitrary AC signal voltage effective value, without
Consider the parameter for being tested waveform.RMS conversion technology may be used, this method is the definition according to real effective, is led to
Obtained from oversampling circuit carries out input ac voltage the operation of " square-average-extract square root ", i.e., do not pass through average folding
It calculates but the virtual value of AC signal is directly converted into direct current signal in proportion.The low price real effective-of AT companies of the U.S.
DC converter AD736 is very typical a kind of, and AD736 uses the averaging integrated after signal square that can directly measure
The authentic and valid value of waveform, and measurement sensitivity, accuracy also substantially improve.AD736 conversion accuracies are 0.3%
(AD736K is through external circuit adjustment up to 0.1%), full range voltage 200mV, supply voltage be+2.8V (- 3.2V)~±
16.5V, 200 μ A of quiescent power supply current in semiconductor integrated circuit.
The connection circuit of AD736 is as shown in Figure 10, and when working sensor, core can be arranged by adjusting the resistance value of sliding variable resistance R9
Piece INA114 is from the arbitarygainvalue between 1 to 10000, and differential wave is after INA114 amplifies, through capacitance C23 blockings, into
Enter progress AC value conversion in AD736 chips, is finally fed in LPC2378 chips with direct current output.R20, VD1, VD2 group
At protection circuit.R20 values are bigger, and protective value is better, but frequency characteristic will be made to degenerate, and it is 33K Ω to take R20.C24 is
AD736 is used for necessary external capacitance when AC measurment.The value of average capacitance C25 directly affects the low frequency characteristic of AD736, here
Select C25=33 μ F.
ARM-LPC2378 is internally integrated the successive approximation type a/d converter of 10bit, needs external offer reference voltage
VREF.Channel 7 is selected in A/D conversions, and analog signal is accessed from LPC2378 pins AD0.7.Piezomagnetic intelligent force sensor exports
Analog signal be directly accessed after amplification, rectification, filtering microprocessor carry out digital-to-analogue conversion, need not increase new A/D turn
Change chip.
Communication system circuit：Communication system shares two schemes, is serial communication mode and CAN communication mode respectively.With
Family selects corresponding communication mode according to host computer signal communication type.Scheme one is that intelligent piezomagnetic resistive force sensor passes through string
Port communications mode is communicated with other host computers.When intelligence sensor is communicated with other controllers, it is also possible to which UART is direct
Data exchange.When intelligence sensor needs are communicated with PC machine, since PC machine serial ports is RS-232 level, then need RS-232 electric
Flat turn parallel operation SP3232 meets communicating requirement, and there are one efficient charge pump, operating voltages only to need 0.1 μ F capacitances when being 3.3V for it
It can be operated, charge pump allows to send the signal for meeting RS-232 under some voltage of SP3232 in+3.3V to+5V.
SP3232 chips have 2 drivers and 2 receivers, and only 1 driver and 1 receiver need to be used in the design.SP3232 cores
The ESD of piece is protected so that the pin of driver and receiver can bear ± 15KV human-body models and IEC1000-4-2 air gaps
Discharge mode.Meanwhile it includes a kind of low-power consumption shutdown mode, the driving output of device and charge pump are prohibited under the pattern,
Under off state, source current is less than 1 μ A.Scheme is second is that the communication of intelligence sensor and other controllers passes through CAN interface reality
It is existing.Bus is the channel of CPU connection external equipments, generally includes data/address bus (DataBus), address bus (AddressBus)
With controlling bus (ControlBus).Address bus is responsible for sending address information to external equipment；Controlling bus is responsible for sending letter
Number control external equipment read or write-in information；Controlling bus is responsible for sending signal control external equipment.Bus is advised
Communication standard of the model between CPU and peripheral hardware, simplifies the design of external devices.It can effectively be reduced out using general bus
Send out cost.The CAN controller of LPC2378 is integrated with a complete CAN protocol (following CAN specification V2.0B), can complete object
The institute for managing layer and data link layer is functional.The pin CAN1RXD and CAN1TXD of CAN controller 1, pass through as built in LPC2378
Isolation bus transceiver CTM1050T is connected with CAN physical bus, it is integrated with all necessary electrical equipments in inside, including
Isolation circuit, CAN transceiver, power circuit and esd bus protect device, can more avoid drawing due to surge, interference
The bus error or element fault risen.The logic level transition of CAN controller is the differential level of CAN bus by CTM1050T,
And with (DC2500V) isolation features, ESD defencive functions and the anti-bus overvoltage of TVS pipe.
This control system is selected using two sets of communication modes for user：Serial ports direct communication and CAN communication, application range is more
Extensively.CAN communication program includes：Initialization (as shown in figure 14), the reception of CAN, the transmission of CAN of CAN controller.
LPC2378CAN controllers are one with sending and receiving the serial line interface of buffer, but it and without containing checking and accepting filter.
It is an independent module to check and accept filter, can carry out CAN identifier filterings to all channels CAN.CAN controller initializes
The messaging parameter of CAN is mainly set.The CAN control registers initialized are needed to have：Mode register, connects time-division register
Receive code register, mask register, bus timing register, output control register etc..It is worth noting that：This register
It can only just can write access in the case where CAN controller is in reset state.Initialization subroutine is substantially carried out to CAN built in LPC2378
The setting of controller and the initialization for receiving buffering area.According to the communication protocol of regulation, program is arranged bus baud rate, matches first
Set extension frame mode.
CAN DRP data reception process is as shown in figure 13, when CAN transceiver, which detects, has data in CAN bus, CAN transmitting-receivings
Differential level signal in CAN bus is converted into bit stream data by device, is aligned by error manager and bit timing logic unit
Data flow and sequential are checked, bit stream data is converted into byte data using bit stream manager and is stored in reception buffering
In device, is then interrupted by reception buffer generation data receiver after frame data reception has been expired and (CPU is notified to have been received one
Frame new data), and the various states of generation are indicated by changing the value of status register.
It is as shown that CAN message receives flow Figure 12.The reception of message uses interrupt mode, complete in CAN initialization programs
It is received at CAN after interrupting initialization, so that it may to receive message by interrupt service routine.When receiving a frame, buffer
When area is filled, interrupt；Or it when having sent a frame, interrupts.Interrupt address must be eliminated when exiting interruption,
It removes and receives interrupt flag bit, and software reset receives interrupt flag bit.When reading the data, reception buffering area is emptied,
Otherwise interruption can be continuously generated.Interrupt service routine flow chart please refers to hereafter task design part.
CAN transmission flows are as shown in figure 11, and transmission data program takes out data to be sent in data storage area, composition
Information frame, and by the addresses ID of host, frame head is inserted, then information frame is sent to the transmission buffering area of CAN controller.Then it opens
The transmission of dynamic CAN controller is enabled, and the data of transmission (become the binary system sent in bus by bit stream manager respectively
Code), mistake manages logic (be responsible for detection bus state and send whether there is mistake) and bit timing logic (management data total
Transmission timing on line), CAN transceiver (be responsible for bit stream data be converted into the differential level that CAN bus can be transmitted), in this way
Just complete the transmission of a frame CAN data.Information is sent to bus from CAN controller and is automatically performed by CAN controller.
Serial communication refers to that one ground sequence of data transmits, its main feature is that communication line is simple, as long as a pair of of transmission
Line can realize two-way communication, thus greatly reduce cost.LPC2378 series As RM has 4 and meets 16C550 industry marks
Accurate asynchronous serial port UART0~3.UART Universal Asynchronous Receiver Transmitter (UART) is exactly the crucial mould that equipment room carries out asynchronous serial communication
Block.Its important function is as follows：
1. handling serial/parallel, the parallel/serial conversion between data/address bus and serial port；
As long as 2. communicating pair using identical frame format and baud rate, can in the case of not shared clock signal,
Communication process only can be completed with two signal wires (RX and TX).
The program of serial ports Direct Communication includes：Initialization of (a) serial ports, rs 232 serial interface signal send and receive.Serial ports receives and dispatches flow as schemed
Shown in 15, in the design, setting baud rate function enables slave computer synchronous with host computer, then, judges whether serial ports receives
The data that host computer is sent, how serial ports receives new data, then generates reception and interrupt, and receives data and carries out respective handling,
If not receiving the data of host computer transmission, using FIFO is sent, the A/D of signal processing is converted in a manner of inquiry
Data are sent in the form of character string.
Intelligent Sensorsystem is controlled using microcontroller, so that performance is greatly improved, has especially been also equipped with flexible adaptation
The ability of various different application occasions.When application environment or requirement change, such as set according to live feature different
Datum mark or change output signal type select different signal processing algorithms etc., due to micro-processor controlled flexibility, usually
Without changing hardware design and control program, and only the setting of the system configuration of sensor and certain running parameters work are repaiied accordingly
Change, sensor can be made to meet the requirements well].Such characteristic makes the scope of application of sensor and versatility greatly improve,
Micro-processor controlled flexible characteristic is further embodied.
This project realizes the reconfiguration of intelligent displacement sensing system using external hanging type man-machine conversation mode.Made using ECU
For external hanging type people-machine Interface of intelligence sensor, number can be exchanged by CAN communication between the two or serial communication
According to realization sensor carries out system configuration with man-machine conversation mode.In addition, it is also expansible auxiliary with ECU is carried out to sensor
Digitalized calibration function is helped, more greatly improves system configuration ability.
When needing the system configuration (baud rate, the range ability of such as serial communication) to sensor to modify, it
It is established and is communicated with ECU by the communication mode of selection, the setting of the original system configuration of sensor, which is then sent to ECU, shows, grasps
Author can change these settings repeatedly on ECU.Configuration modification finishes, then new configuration setting is passed back sensor and is preserved
System configuration setting area in nonvolatile memory.It such as also needs to demarcate, then ECU compounding practices person command sensor is gradually completing
Calibration, and nominal data is stored in nonvolatile memory.Then sensor by the new system configuration pattern and will work as
Preceding calibration setting work is until changing system configuration or calibration next time.
The reset circuit of this project minimum system, the chip of selection be CAT1021, and CAT1021 is embedded, and there are one 2K
Serial EEPROM, the various system configuration definition of sensor are just stored in here, and the relation curve that rating test obtains is with grid
Form be stored in the inside, calculated for the data fusion extension in later measurement process.
As shown in figure 3, when tractor works, lower pull rod 13 exerts a force to centrepin, and centrepin is in lower pull rod and fulcrum bearing
Maximum shear force effect is born in 11 parting surface region, groove 8 is used for amplifying the deformation that shear stress bears shell 1.Meanwhile
The magnet exciting coil for inputting exciting current generates magnetic field, according to the pass between the variation of the relative permeability of magnetic material and mechanical stress
System, magnetic conductivity changes when centrepin stress, and magnetic flux also changes, and the variation of induction coil induced flux generates induction
Electromotive force.
When work, pin-shaped sensor is assembled under farm implements between pull rod and tractor-drawn shell, when tractor is run,
Soil forms shearing force by pull rod under tractor to the resistances of farm implements to sensor concentration zones, it is made to generate shearing force and curved
Square, shearing force and moment of flexure here make its magnetic conductivity change, and magnetic flux also changes, induction coil and induced flux
Variation generates induced electromotive force, and to generate electric signal, the electric signal of generation is transmitted and is handled by control signal circuit,
And then realize the detection of tractor resistance, it can accurately incude the resistance suffered by tractor, and more accurately hindering
Feedback is realized in Force control system.
The preferred embodiment of the present invention has been described in detail above.It should be appreciated that those skilled in the art without
It needs creative work according to the present invention can conceive and makes many modifications and variations.Therefore, all technologies in the art
Personnel are available by logical analysis, reasoning, or a limited experiment on the basis of existing technology under this invention's idea
Technical solution, all should be in the protection domain being defined in the patent claims.
Claims (7)
1. a kind of tractor resistance detection device, it is characterized in that：Including shearing force induction shell (1), the shearing force induction is outer
Shell (1) is internally provided with electrical signal conversion device, and the electrical signal conversion device is set as piezomagnetic force snesor, the pressure magnetic
Formula force snesor is connected with electric signal output control circuit.
2. tractor resistance detection device as described in claim 1, it is characterized in that：The shearing force induction shell (1) is arranged
For round pin shape；
The shearing force induction shell (1) is internally provided with endoporus (4)；It is provided with pressure sensor in the endoporus (4)
(5)；
The pressure sensor (5) includes excitation magnetic core (6), and face institute is arranged inside the endoporus in the excitation magnetic core (6)
The position of shearing concentration zones (3) is stated, induction magnetic core (7), the induction magnetic core are provided at left and right sides of the excitation magnetic core (6)
(7) longitudinal profile where magnetic pole and longitudinal profile where the magnetic pole of induction magnetic core are in 90 °；The magnetic pole position of the induction magnetic core (7)
In shearing concentration zones；
The excitation magnetic core (6) and induction magnetic core (7) form cylindrical entirety, are fitted close with the endoporus (4)；
Fluted (8) are set in the middle part of the shearing force shell (1)；The excitation magnetic core (6) it is external with the induction magnetic core (7) it
Between be provided with fixing device (9), the fixing device (9) includes excitation magnetic core enclosure (91) and fixed part (92), described solid
Determine portion (92) to match with the fixed groove (10) of shearing force shell (1) initiating terminal；
Shearing force shell (1) end is provided with chamfering.
3. tractor resistance detection device as described in claim 1, it is characterized in that：The electric signal output control circuit includes master
Controller, power system circuit, communication system circuit, clock system circuit, reset circuit system, signal amplification and signal are effective
It is worth transformation system circuit.
4. tractor resistance detection device as described in claim 1, it is characterized in that：The power system circuit includes preceding level power supply
Circuit and final stage power circuit；The front stage circuits realize conversion of the 24V voltages to 5V voltages；The final circuit realizes 5V electricity
Press to the conversion of 3.3V voltages；
The front stage circuits, which are also realized, converts 24V voltages to 15V；The final circuit also realize+15V voltages are converted to-
15V voltages.
5. tractor resistance detection device as described in claim 1, it is characterized in that：The front stage circuits include that three proper voltages are steady
Press chip and output voltage chip；
The three proper voltage voltage stabilizing chip uses L7815；
The output voltage chip uses DCDC_S5；
The final circuit includes charge pump voltage inversion device and low voltage difference analog power；
The charge pump voltage inversion device is set as ICL7662CPA；
The low voltage difference analog power is set as SPX1117；
The power system circuit further includes AD conversion a reference source potential circuit, including a reference source voltage output chip, the base
Quasi- source voltage output chip is set as AD530ART.
6. tractor resistance detection device as described in claim 1, it is characterized in that：The clock system circuit includes crystal oscillator frequency
For the external crystal-controlled oscillation of 11.0592MHz；
The reset circuit system includes reset chip, and the reset chip is set as CAT1021；
The signal amplification and effective value transformation circuit system include instrumentation amplifier；
The instrumentation amplifier is set as INA114；
The signal amplification and effective value transformation circuit system include A/D converter；The A/D converter is set as AD736.
7. tractor resistance detection device as described in claim 1, it is characterized in that：The communication system circuit includes below one
Kind or several, serial communication circuit, CAN communication circuit；
The serial communication circuit includes level translator, signal transmitting and receiving chip；
The level translator uses RS-232；The signal transmitting and receiving chip uses SP3232；
The CAN communication circuit includes CAN controller, the integrated CAN protocol for following CAN specifications V2.0B of the CAN controller；
The CAN controller uses LPC2378.
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