CN103499270A - Piston position detection processing method for free piston internal combustion engine generator - Google Patents

Abstract

The invention discloses a piston position detection processing method for a free piston internal combustion engine generator. According to the method, the free piston internal combustion engine generator is provided with two static magnetic heads in the axial direction of a rotor; two paths of signals output by the two static magnetic heads are enabled to be orthorhombic. During the detection, the signals output by the two static magnetic heads are input into a single chip microcomputer after the conversion, the single chip microcomputer calculates the piston displacement according to the signals, and further, the moving direction can also be determined. The piston position detection processing method has the advantages that the additional installation of a displacement sensor is not needed, the static magnetic heads are adopted for measuring the flux change in the rotor moving process, and the piston displacement is indirectly obtained, so the position detection problem is solved, the redundant installation is avoided, and the system space is saved.

Description

A kind of piston position Check processing method of free-piston internal combustion engine generator

Technical field

The present invention relates to free-piston internal combustion engine generator technology, relate in particular to a kind of piston position Check processing method of free-piston internal combustion engine generator.

Background technology

A kind of novel power device that grow up the thirties 20th century of free-piston type internal-combustion engine, it has cancelled toggle, piston is only done linear reciprocating motion, and stroke is not subject to mechanical constraint, combine engine and linear induction motor technical characterstic each other, receive much concern as a kind of novel electricity generator theory.The structure of this device as shown in Figure 1, utilizes linear electric motors to be fixedly connected with 2 engines.In left cylinder, burn while doing expansion stroke, the piston right lateral, carry out pressure stroke to right cylinder; When piston reaches the top dead centre of this circulation, right cylinder starts to carry out ignition and does expansion stroke; In this way, piston moves back and forth in linear electric motors, and the magnetic line of force in the cutting generator produces induction electromotive force, externally exports electric energy.

For whole system, no matter start or uncertain operation process in, the ignition timing of each circulation, fuel delivery will directly affect the running frequency, efficiency, output power, load capacity of system etc.And the free piston IC generator be different from traditional combustion engine can be by the displacement that rotatablely moves to demarcate piston of crank end, therefore to a kind of new-type control system of position of piston of its design and realize the accurate judgement of piston position particularly necessary.Only have the accurate piston position that obtained, could further realize the control to system input parameter.

Summary of the invention

In view of this, the present invention contains the actual conditions of magnetic-grid-type mover forever in conjunction with linear electric motors, a kind of piston position Check processing method of free-piston internal combustion engine generator is provided, without extra installation position displacement sensor, utilization is arranged on the static head on the free-piston internal combustion engine generator, measure the flux change in the mover motion process, then obtain piston displacement.

This Check processing method comprises the steps:

Step 1, at the free-piston internal combustion engine generator along axial arranged two static heads of mover, guarantee described two static heads output two paths of signals quadrature;

Simulation Sin/Cos scrambler output two-way Sin signal and the two-way Cos signal of step 2, static head, be designated as respectively Sin+, Sin-, Cos+, Cos-, Sin+, Sin-signal and Cos+, Cos-signal are carried out respectively to differential amplification, acquisition-1.5V～+ Sin of 1.5V, Cos signal, then adopt the homophase adding circuit Sin, Cos signal to be transformed to Sin, the Cos signal of the discernible 1V～4V of single-chip microcomputer, the input single-chip microcomputer;

Step 3, single-chip microcomputer in (1,1) interval, make the Sin signal=a after normalization by the Sin that receives, Cos signal normalization, and Cos signal=b, as a>0 the time, adopt formula

solve electric angle θ corresponding to current displacement, otherwise, formula adopted

solve electric angle θ corresponding to current displacement;

Adopt following formula to calculate piston displacement S:

$S=\frac{\mathrm{\θ}}{360}\×U$

Wherein, the pole pitch that U is free-piston internal combustion engine generator cathetus motor coaxle magnetic grid.

In above-mentioned steps three, can further according to the Sin signal after normalization, Cos signal, determine the piston movement direction:

As a > 0 the time, judge whether to meet current time and upper and compare the condition that b value increases constantly, if so, definite piston movement direction is descending, otherwise is up;

When a≤0, judge whether to meet current time and upper and compare the little condition of b value increase and decrease constantly, if so, definite piston movement direction is descending, otherwise is up.

Beneficial effect: without extra installation position displacement sensor, adopt static head to measure flux change in the mover motion process, indirectly obtain piston displacement, thereby solved the problem of position probing, avoided the redundancy installation, saved system space.

The accompanying drawing explanation

The structural drawing that Fig. 1 is the free-piston internal combustion engine generator.

Fig. 2 is the static head structure diagram.

Fig. 3 is the signal processing method sketch.

Fig. 4 is static head output signal schematic diagram.

Fig. 5 is displacement process flow figure.

Fig. 6 is the moving direction processing flow chart.

Embodiment

On principle, say, the piston mover in the free-piston internal combustion engine generator is done rectilinear motion, can pass through the installation position displacement sensor, realizes the detection of piston position.But this needs extra sensor installation.In fact, linear electric motors in the free-piston internal combustion engine generator include magnet movement part (contained bar magnet as routine as this) and can be considered permanent magnetism grid formula mover, by being equipped with static head (the static head structure as shown in Figure 2), form magnetic flux transducer with magnetic-grid-type mover forever, can measure the flux change in the mover motion process, the magnetic flux feedback signal, through conversion process, obtains piston position then.

Based on this, the present invention is along axial arranged two static heads of free-piston internal combustion engine generator mover, guarantee two static heads output two paths of signals quadratures (spacing of magnetic head is relevant to pole pitch, and to be pole pitch can guarantee 1/4 time that two static heads are exported the two paths of signals quadratures when the spacing of magnetic head).And, adopt two static heads during configuration, make in the situation that there is no relative motion, static head also has signal output.Adopt two static heads, can judge displacement and the direction of motion of piston simultaneously, thereby solve the position probing problem, avoided the redundancy installation, saved system space.

Wherein, according to the concrete principle of displacement of flux change judgement piston, be:

The principle of static head read output signal is that magnetic grid utilizes the variation of its leakage flux to produce induced potential.Leakage flux Φ between magnetic grid and magnetic head ₀be divided into two parts through magnetic head, a part of Φ ₂iron core by magnetic head; Another part Φ ₃by air gap, have

${\mathrm{\Φ}}_2={\mathrm{\Φ}}_0\·\frac{R_{\mathrm{\δ}}}{R_{\mathrm{\δ}}+R_T}---\left(1\right)$

In formula, R _δfor air-gap reluctance; R _tfor magnetic resistance unshakable in one's determination;

Generally can think R _δconstant, and R _tthe magnetizing flux Φ produced with drive coil ₁relevant, because the sectional area at P unshakable in one's determination, Q two ends is very little, excitation voltage u changes one-period, unshakable in one's determination saturated twice, R _tchange two cycles.Therefore, can be similar to and think

Φ ₂＝Φ ₀(a ₀+a ₂sin2ωt) (2)

In formula, a ₀, a ₂for the constant with the magnetic head structure relating to parameters; The angular frequency that ω is excitation power supply voltage.

When magnetic grid and magnetic head do not have relative motion, because of Φ ₀be a constant, the induced potential that the output winding produces is

$u_0=N_2\frac{d{\mathrm{\Φ}}_2}{\mathrm{dt}}=N_2\·\frac{d}{\mathrm{dt}}\left[{\mathrm{\Φ}}_0(a_0+a_2\sin 2\mathrm{\ωt})\right]=2N_2{\mathrm{\Φ}}_0{a}_2\mathrm{\ω}\cos 2\mathrm{\ωt}=k{\mathrm{\Φ}}_0\cos 2\mathrm{\ωt}---\left(3\right)$

In formula, k=2N ₂ω is constant; N2 is the output umber of turn.

When magnetic grid and magnetic head have relative motion, because leakage flux is the periodic function of magnetic grid position, magnetic grid and head relative move a pitch W, and leakage flux just changes one-period, and leakage flux is approximately

${\mathrm{\Φ}}_0={\mathrm{\Φ}}_m\sin \frac{2\mathrm{\πx}}{W}---\left(4\right)$

By formula (2), had

${\mathrm{\Φ}}_2={\mathrm{\Φ}}_m\sin \frac{2\mathrm{\πx}}{W}(a_0+a_2\sin 2\mathrm{\ωt})---\left(5\right)$

The induced potential of exporting the winding generation is

$u_0=N_2\frac{d{\mathrm{\Φ}}_2}{\mathrm{dt}}=k{\mathrm{\Φ}}_m\sin \frac{2\mathrm{\πx}}{W}\cos 2\mathrm{\ωt}---\left(6\right)$

In formula, x is the displacement of magnetic grid head relative; Φ _mpeak value for leakage flux.

From formula (6), the static head output signal is a modulation waveform, and its amplitude is

$U_m=k{\mathrm{\Φ}}_m\sin \frac{2\mathrm{\πx}}{W}---\left(7\right)$

From above formula, static head output signal voltage amplitude is varies with sinusoidal function with x, and it is the envelope of Balance Amplitude Modulation Wave, and frequency is 2 times of excitation voltage frequency.

As shown in Figure 3, the Displacement Feedback of static head adopts simulation Sin/Cos scrambler, and its output signal is Sin+, Sin-, Cos+, Cos-, take this 4 road differential signal as basis, the displacement of calculating piston component.At first Sin+, Sin-signal and Cos+, Cos-signal are carried out respectively to differential amplification, acquisition-1.5V～+ Sin of 1.5V, Cos signal.Then by the homophase adding circuit, it is transformed to Sin, the Cos signal of with a high credibility and the discernible 1V～4V of single-chip microcomputer, the input single-chip microcomputer.

Single-chip microcomputer is responsible for according to Sin, the piston displacement of Cos calculated signals.Specifically, magnetic grid pole pitch U=71.2mm, corresponding 360 degree electric angles, angle is linear corresponding with displacement.Throw of poston D=50mm, so the displacement signal of signal processing circuit output is complete cosine and sine signal, as shown in Figure 4.The COS signal, about the minimum point rotational symmetry, utilizes the SIN signal to carry out segmentation to calculating, utilizes the monotonic nature of COS signal in piecewise interval to solve electric angle, and then solves displacement.As shown in Figure 5, at first by Sin, Cos signal normalization in (1,1) interval, make Sin signal=a, Cos signal=b, as a>0 the time, adopt formula

solve electric angle θ corresponding to current displacement, otherwise, formula adopted

solve electric angle θ corresponding to current displacement.Then adopt following formula to calculate piston displacement S:

$S=\frac{\mathrm{\θ}}{360}\×U=\frac{\mathrm{\θ}}{360}\×71.2$

Can also further judge the piston movement direction according to above-mentioned Sin signal and Cos signal, specifically:

Can see that by Fig. 4 the Cos signal changes in 20mm place monotonicity in whole stroke 50mm.Therefore the point that the point of easily knowing the variation of cos pitch of signal note is a=0, establishing the position that a=0 order is s1, when 0<S<s1, a > 0, Cos pitch of signal note descending branch namely, b is along with the time reduces to mean that S increases, and b is along with the time increase means that S reduces; Otherwise, when s1<S<50, a≤0, Cos pitch of signal note ascent stage namely, b is along with the time reduces to mean that S reduces, and b increased and means that S increases along with the time.So as shown in Figure 6, the determination flow of piston movement direction is:

After to Sin signal, Cos signal normalization, further according to the value of a, b, judged;

As a>0 the time, judge whether to meet the condition that current time and upper is compared the increase of b value constantly, i.e. b _n+1-b _n0, if so, determine that the piston movement direction is descending, otherwise be up;

When a≤0, judge whether to meet current time and upper and compare b value constantly and increase and decrease little condition, i.e. b _n+1-b _n<0, if so, determine that the piston movement direction is descending, otherwise be up;

Wherein, b _n+1and b _nsubscript mean constantly; Up is that displacement increases, and descending is that displacement reduces.

In sum, these are only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.Within the spirit and principles in the present invention all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.

Claims (2)

1. the piston position Check processing method of a free-piston internal combustion engine generator, is characterized in that, comprising:

Step 1, at the free-piston internal combustion engine generator along axial arranged two static heads of mover, guarantee described two static heads output two paths of signals quadrature;

Simulation Sin/Cos scrambler output two-way Sin signal and the two-way Cos signal of step 2, static head, be designated as respectively Sin+, Sin-, Cos+, Cos-, Sin+, Sin-signal and Cos+, Cos-signal are carried out respectively to differential amplification, acquisition-1.5V～+ Sin of 1.5V, Cos signal, then adopt the homophase adding circuit Sin, Cos signal to be transformed to Sin, the Cos signal of the discernible 1V～4V of single-chip microcomputer, the input single-chip microcomputer;

Step 3, single-chip microcomputer in (1,1) interval, make the Sin signal=a after normalization by the Sin that receives, Cos signal normalization, and Cos signal=b, as a>0 the time, adopt formula

solve electric angle θ corresponding to current displacement, otherwise, formula adopted

solve electric angle θ corresponding to current displacement;

Adopt following formula to calculate piston displacement S:

$S=\frac{\mathrm{\&theta;}}{360}\&times;U$

Wherein, the pole pitch that U is free-piston internal combustion engine generator cathetus motor coaxle magnetic grid.

2. the method for claim 1, is characterized in that, described step 3 is further determined the piston movement direction according to the Sin signal after normalization, Cos signal:

As a > 0 the time, judge whether to meet current time and upper and compare the condition that b value increases constantly, if so, definite piston movement direction is descending, otherwise is up;

When a≤0, judge whether to meet current time and upper and compare the little condition of b value increase and decrease constantly, if so, definite piston movement direction is descending, otherwise is up.

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