RU2524687C2 - Space incremental velocity gauge - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: invention relates to a spacecraft (SC) instrumentation and can be used for high-accuracy determination of minor incremental velocity of the SC progressive motion. The gauge has a hollow spherical body (1) on the outer surface whereof electric magnets (2) are positioned. Position on the body (1) is a network of targeted photoreceivers with an inertial mass (5) contained inside the body. The mass electromagnetic suspension (5) is designed in the form of embedded electric magnets (6) interacting with the electric magnets (2). The mass position sensor (5) represents an optocoupler composed of three optocouples. The radiators in the optocouples are represented by LEDs inside the mass (5) with optic axes (27). Radiation along the said axes falls onto the said photoreceivers of the body. The LEDs are powered from a helium battery embedded into the mass (5). It is charged from currents in the electric magnets (6) windings. The device operation modes are set by the operator (10) via the software (9) control and administration unit (7). Power is supplied from the source (8).

EFFECT: invention technical effect consists in creation of a high precision device (error less than 6%) for measurement of incremental velocity with acceleration of non-gravitational nature in effect equal to approximately (10^-6-10^-10) m/s².

2 cl, 6 dwg

Description

The invention relates to space technology and is intended to measure the increment of the speed of translational motion in zero gravity conditions in on-board navigation and spacecraft motion control systems.

The present invention is intended for reliable and accurate measurement of the increment of the speed of the spacecraft. A speed increment meter in navigation is a device that, given the knowledge of the application time of the pulse, can be considered an accelerometer.

Many accelerometer device circuits are known. As the main areas of development, for comparison with the proposed device, the following can be cited:

1. Known integrated micromechanical field emission accelerometer (RU 2390031 C1) containing a substrate, four stationary electrodes rigidly fixed relative to the substrate, an inertial mass located with a gap relative to the substrate, four movable electrodes rigidly connected to the inertial mass, forming four pairs with stationary electrodes tunnel contacts used as displacement transducers, an anchor region rigidly fixed relative to the substrate, four auxiliary fixed the electrode, rigidly fixed relative to the substrate, four auxiliary movable electrodes, located with a gap above the auxiliary fixed electrodes, forming four flat capacitors with them, additionally containing a cross-shaped suspension, the central part of which is fixed relative to the anchor region, and a support frame connected to the cross-shaped suspension and fixed relative to the inertial mass, while the auxiliary movable electrodes are fixed at the corners of the supporting frame, the substrate and the inertial m PAS made of a dielectric material, and movable and fixed electrodes fixed auxiliary electrodes are made of metal, and the anchor region, the cross-shaped hanger, the support frame and supporting the movable electrodes are made of a single element semiconductor material. When acceleration of the substrate in the direction of one of the axes occurs, the support frame, together with the inertial mass and the movable electrodes fixed on it, moves along this axis under the action of inertia forces, which leads to deformation of the cross suspension. The tunneling currents flowing between the movable electrodes and the stationary electrodes receive equal increments due to the simultaneous change in the width of all the gaps, characterizing the magnitude of the acceleration. When operating in the compensation mode, the force acting on the support frame with an inertial mass fixed on it, caused by measured acceleration, is balanced with the help of auxiliary stationary electrodes and auxiliary mobile electrodes, which makes it possible to maintain constant tunnel currents flowing between movable and fixed electrodes. The output signal in this case is the magnitude of the voltage applied between the auxiliary electrodes. This analogue uses the fact that “due to the smallness of the gap separating the regions of the movable and fixed electrodes, electrons that have a sufficient probability of passing through the potential barriers formed by the gaps tunnel from the stationary electrodes into the corresponding movable electrodes and thereby create tunneling currents that are output device signals. "

The disadvantage of this device is its low sensitivity, which is difficult to raise in this area of technology, since the theory of the tunneling effect is complicated, and the density and current formulas have a coefficient and power-specific form for each substance, the degree of the external electric field strength and the magnitude of the same units, which includes a lot of non-linear specificity related to the properties of an electron. It follows that the function of changing the current strength (which can be interpreted as acceleration from external forces) is also not linear - the same experimental conditions do not guarantee the quality of determining the acceleration.

2. Known three-axis accelerometer with variable axial sensitivity (RU 2390030 C2), containing an inertial mass and a support system for inertial mass, and the support system contains a base and many support elements passing between the base and inertial mass to suspend the inertial mass in orthogonal directions, providing statically indefinite design, voltage sensors designed to measure the acceleration due to voltage in the supporting elements by determining pairs tra mass acceleration. Instead of strain gauges, it is possible to use other sensors, for example, beam resonator systems, in which the oscillation frequencies change when the load changes in proportion to the acceleration, forming the corresponding output signal.

In this analogue, it is possible to use a wide range of various sensitive elements, the parameters of which vary in proportion to the acceleration from the load, such as strain gages, crystal dielectrics, resonator systems. The disadvantage of this device is that not a single modification of this technical solution brings the accuracy of determining acceleration closer to the accuracy of the readings of a single good sensor, say, 2-3%, as this is prevented by the presence of a long chain of sensor equipment, converter circuits, and clocks from external force to result.

In relation to load cells. They usually work in the field of elastic deformations at ε · 10 ^-3 , changing their resistance in proportion to the initial, e and the coefficient of strain sensitivity k = 2-200, while in the region of small loads (k are units), which occurs when the correction motors are switched on space, the effect itself disappears against the background of a temperature change in resistance even when the temperature changes by several degrees. Such thermal insulation in space is problematic.

With regard to piezoelectric sensors. Under the action of pressure, electrical signals arise (the total EMF is proportional to the pressure) due to the polarization of the dielectric, which is proportional to a certain coefficient (for quartz, for example, 3 · 10 ^-8 ), which greatly depends on the operating conditions. In general, the effect, on the one hand, is subtle (a small amount of polarization), on the other hand, it is gross - (large external loads). And most importantly, due to the fact that at relatively constant pressure (acceleration), which is required in space conditions when determining the acceleration of the motion of the center of mass of the spacecraft, the effect quickly disappears, because electric charges "drain". Therefore, piezosensors are not applicable in principle.

Regarding the use of resonator systems. This technical solution is based on the fact that the tuning fork element, subject to oscillation from the frequency generator, under the influence of tension-compression from the action of inertial mass changes the frequency of its oscillations in proportion to acceleration. Proportionality is possible even with the oscillatory motion of the inertial mass and is unlikely with translational motion. In any case, the accuracy of determining the change in the resulting oscillation of the resonator is very low or technically difficult.

3. The closest known technical solutions is an angular accelerometer (RU 2399915 C1) containing an inertial mass on elastic suspensions, a position sensor, a base and a cover, two permanent magnets, a comparator, a key and a direct current source, the inertial mass is made of monocrystalline silicon in in the form of a disk with optical slots and placed in the gap between the permanent magnets with the possibility of angular movement, the magnets are fixed on the base and the cover, the position sensor is made of two emitters and two photodetectors the optical axes of which pass through the optical slots and are fixed in the holes on the base and the cover, conductive tracks are radially sprayed on the surface of the inertial mass, the beginnings and ends of which are interconnected by sprayed conductive rings, and each of the rings is connected through the elastic suspensions to the outputs of the key, to the first input of which a DC source is connected, and the output of a comparator is connected to the second input, the outputs of photodetectors are connected to its input, and the emitters are connected to the source Iku of a direct current. This technical solution is taken as a prototype.

We omit the consideration of purely mechanical all kinds of spring systems with arrows - they are obviously unsuitable for such a delicate matter as determining acceleration from weak factors perturbing the motion of the center of mass of the spacecraft.

The prototype, in principle, gives good results and has acceptable weight and size characteristics, however, the device is designed strictly to determine angular accelerations from external forces and should be in the center of inertia, deviation from which introduces significant errors in determining angular acceleration. This is a big disadvantage of this solution. And this technical solution in its functionality is unsuitable for the above task of determining translational acceleration.

The task is to create a device that measures the increment of speed or the acceleration of translational motion, depending on the nature of the action of disturbance factors of non-gravitational nature of the order of 10 ^-6 -10 ^-10 ohmmeters per second per second [1]. The error of the device (see justification of methodological accuracy) must be deliberately less than 6%, at any level of acceleration or increment of speed. At present, there are no devices of this class in the Russian Federation; moreover, there is no system for metrological support of measurements of this magnitude. However, the approach to creating a space velocity increment meter (CIPS) removes the relevance of the issue of metrological support.

The goal is achieved in that the CIPS, which contains an inertial mass (MI), a position sensor, has a body in the form of a hollow ball, a network of photodetectors fixed to digital equipment outside the ball is fixed on the inner surface of the body, four identical external electromagnets are uniformly spaced in space (VEM), while the VEM axes intersect in the center of the sphere and are strictly “attached” to the satellite orbital coordinate system (OSK), inside the case there is an IM - a hollow ball is not a ferromagnet with three holes, it is equipped lenses whose main optical axes are the main axes of the moving coordinate system (ICS) with the origin in the center of mass of the ball, inside the ball: four identical electromagnets (EM) uniformly spaced in space so that the axis of the EM intersect in the center of mass of the ball; three emitters (light emitting diodes) according to the number of main axes of the moving coordinate system, installed in the main focal points of the lenses; source of power; switching unit (BC); inductive recharging circuit of a power source (IP) from a VEM; SP charge sensor; mass balance;

an epoxy filler of a ball with channels for the passage of rays from emitters to lenses, the position sensor is made as an optocoupler of three optocouplers, emitters and radiation emitters in which are respectively the LEDs inside the MI and the network of addressable photodetectors on the inner surface of the housing.

The technical result is achieved due to the fact that before the start of the work cycle, the MI is pulled to the start with the subsequent transfer of the IM to the KIPS center and the switching off of all KIPS EMs. Knowing the initial binding of the UCS to the CSC and the hodograph — the nature of the display of the movement of rays from the CSC along the surface of the sphere (the inner surface of the CIPS housing) through a network of addressable photodetectors, each of which has its own nominal coordinates in the CSC, therefore, knowing the distance that the inertial mass travels inside the sphere projection of this distance on the axis of the USC and the travel time of these distances, we will have the value of the resulting increment of velocity from weak perturbing factors in the projections on the axis of the USC with a relative error Tew less than 7%. The travel time of the inertial mass is:

$$\Delta t=t_{\mathrm{one}}-t_0,\text{(one)}$$

where t ₁ - step of the operating cycle of the device, s;

t ₀ - the moment of shutdown of all electromagnets, s.

Times t ₁ and t _{0 are} read on the on-board time scale - in seconds from the beginning of the reference year with the highest possible accuracy (0.25 s).

During the operation of all CIPS EMs at the beginning of measurements, the projection of each of the geometric axes of the EM MI on the sphere is equidistant from the centers of the VEM seats closest to them. This is how magnetic fields of EM KIPS interact - this is how stable fixation of PSC axes in space is achieved at the beginning of the working cycle.

The invention is illustrated by drawings. Figure 1 presents the electrokinematic diagram of KIPS, figure 2 shows the device of inertial mass, figure 3 shows the circuit diagram of the BC IM, figure 4, figure 5, figure 6 shows the circuit diagram of the active MI, respectively, in modes :

- measurements;

- initial and accurate arrest (direct current);

- charge.

A description of all CIPS operating modes is given below.

The following notation is introduced:

1 - screen-vacuum thermal insulation;

2 - external electromagnets (VEM);

3 - KIPS case;

4 - rays from LEDs;

5 - body inertial mass;

6, 11 - electromagnets of inertial mass (EM IM);

7 - control and management unit (BKU);

8 - external power source (VIP);

9 - on-board software KIPS;

10 - operator at the command and measurement point;

12 - power source - rechargeable battery (AB);

13 - switching unit (BC);

14 - lens;

15 - mass balance;

16 - epoxy filler;

17 - channel passage of rays from the emitters;

18 - emitter - LED;

19-24 - inputs and outputs to the BK from the BK;

25 - rectifier;

26 - battery charge sensor;

27 - axis CPM.

The cell size of the network of photodetectors (0.9 ÷ 1) mm ² . The network of photodetectors is combined with a spherical array that protects against accidental mechanical damage with a height of (0.1-0.3) mm above the active surface of the photodetector, the cell of which has the same size as the cell of the network of photodetectors ((0.9 ÷ 1) mm ² ) . Lattice wall thickness 1 mm. Thus, the distance between the centers of the photodetectors on the sphere will be about 2 mm, depending on the adopted cell regularization scheme.

MI with all its equipment, with the exception of the small central region where the emitter connectors are located, is filled with an epoxy opaque composition 16, which, when solidified, creates ideal operating conditions for the MI.

VIP works in two modes:

- creates a direct current;

- creates alternating current.

In fact, a VIP is a set of two current sources: a spacecraft battery charging from solar panels, and an alternator.

KIPS has six operating modes and works as follows:

1. The mode of initial arrest of MI:

- include AB 12;

- disconnect all VEM 2 from VIP 8;

- one of the VEM 2 is supplied with direct current in the same direction as in all EM 6;

- the position of the light spot on the grid of photodetectors fix the adjacency of one of the EM IM to the VEM. Thus, they set the MI on the start for a “shot” in the central region of KIPS;

- change the direction of the direct current in the VEM, thereby making a "shot" in the central region of the KIPS;

- after the estimated (known) time, direct current is supplied to all VEM. This time depends on the repulsive force between the VEM and the EM. IM arrest occurs during the interaction of the magnetic fields of all VEM and EM IM in the variant of mutual repulsion as the most effective m (see Fig. 5).

2. IM arrest mode:

- turn off the battery;

- connect all VEM to VIP from alternating current.

In the future, the MI will be located in the center of the KIPS in the variant of mutual attraction due to the phenomenon of mutual induction under the influence of alternating magnetic fluxes of the VEM passing through the EM of the IM, or it will be joined to one of the VEM.

3. The mode of accurate arrest of MI:

- turn on the LEDs 18;

- the operator 10 (or software program 9) records the onset of stability of the position of light spots on the grid of photodetectors;

- go to the measurement mode.

4. Measurement mode:

- turn off all (eight) EM 2.6 KIPS. The MI begins its movement inside the KIPS case, highlighting one or another numbered photodetector-photodiode on the spherical surface of the internal wall of the KIPS case (see Fig. 4).

All external factors, with the exception of those from which disturbances are measured, are excluded.

5. AB charging mode:

- turn off the LEDs 18;

- if the CIPS was in the measurement mode, then work is performed on the initial arrest of the MI, then the arrest of the MI, while the AB remains in the on position. AB receives a charge due to the phenomenon of mutual induction under the influence of alternating magnetic fluxes of VEM passing through EM EM (see Fig.6).

Charging mode is used when discharging the battery to the lower level.

6. Standby time:

AB is off. This mode is necessary due to possible long interruptions in the operation of CIPS for its intended purpose. KIPS is in the mode of arrest.

So, VEMs are always in working condition, with the exception of periods when the CIPS is in the measurement mode — a constant or smoothed alternating current passes through them. The exact arrest mode (when direct current is used) always precedes the measurement mode, the arrest mode (standby mode; when alternating current is used) always follows the measurement mode and precedes the initial arrest mode, the initial arrest mode precedes the exact arrest mode.

BKU 7 has an electrical connection with the VEM, radio communication with the BK 13 IM and with the sensor of the level of charge-discharge AB IM. BKU is connected telemetrically with the operator 10 at the command and measurement point and (or) information - with the corresponding on-board software 9 KIPS.

KIPS software includes the following programs:

- a program for calculating the velocity increment vector;

- a program for calculating the distance traveled by the MI for activation of photodetectors in conjunction with the USC;

- a program for monitoring the duration of initial arrest and accurate arrest according to the state of activation of photodetectors;

- a program for recommending a plan for compensating the resulting increment of the spacecraft speed from disturbing factors smaller than the solar pressure and the eccentricity of the spacecraft’s orbit by turning on small thrust engines.

Justification of the methodological accuracy of the proposed solution

If we fix only the relative distance traveled by the MI (spacecraft) and time, then we obtain the magnitude of the increment of speed - an important value for estimates and navigation. If it is reliably known that the perturbing factor (perturbing factors) has (have) a permanent character, then we obtain the value of the acceleration (resulting acceleration).

1. The speed increment, due to the negligible duration of the disturbing pulse compared to the operating cycle of the CIPS measurements (when the disturbances are constant, see Section 2), is calculated by the formula for uniform motion in the absence of the initial speed:

$$\Delta V=\frac{S}{\Delta t},\text{(2)}$$

where S is the distance traveled, m

We number the coordinate axes of the UCS:

$$i,j=\left(\mathrm{1,2,3}\right)\equiv \left(X,Y,Z\right)\text{(3)}$$

$$ij\equiv \mathrm{12,13,23.}\text{(3`)}$$

The projection (П _Sij ) of the distance traveled by the center of the MI in the measurement process

CIPS, to the selected coordinate plane of the UCS at the initial moment of the measurement working cycle (NPSC), fixed at the beginning of the working cycle, is determined by the ratio:

$$P_{Sij}=R\cdot \sin \left(\frac{L_i}{R}\right),\text{(four)}$$

where R is the radius of the inner sphere of KIPS (0,075-0,125) m;

L _i - projection onto the internal sphere of CIPS traveled by the center of the MI path, highlighted by a beam from the i-th LED and recorded by addressable photodetectors, m

It should be borne in mind that the numbering of the rays (l _i ) (or coordinate axes of the UCS) is related to the numbering of P _s as follows: (l ₁ -P _S23 ); (l ₂ -P _S13 ); (l ₃ -P _S12 ). Since speech

We are talking about the parallel transfer of the IMCS IM at the current time relative to the IMCS IM and the latter has a strict reference to the USC through the matrix of cosines of the set rotation angles in the modes of initial and accurate arrest of the IM, you can always have any data set related to the position of the IM in inertial space. The targeting of the photodetectors removes all the questions of determining the position of the MI in the space of CIPS at any time.

It would be possible to dispense with two emitters that give radiation only along two coordinate axes, because at the time the measurement cycle ends, we always obtain the coordinates of the end of the MI path through the addressing of the photodetectors. However, excessive independent measurement makes it possible to identify systematic errors in the settings of the emitters, i.e. systematic deviations of the rays l ₁ , l ₂ and l ₃ from the nominal directions. Equation (4) allows us to find linear, and through them, angular residuals. Adjustment of KIPS is not included in the distinguishing features of the invention - the device - only the idea of the operability of a technical solution is important.

We differentiate (2) and go to the equation of independent errors:

$$\delta V=\frac{\mathrm{one}}{\Delta t}\delta S+\frac{S}{\Delta t^2}\delta t,\text{(5)}$$

and

$$\delta V_{\mathrm{one}}=\frac{\delta S}{\Delta t},\text{(6)}$$

$$\delta V_2=\frac{\delta S}{\Delta t^2}.\text{(7)}$$

We assume that the distance that the center of the MI can travel inside the CIPS (more precisely, the spacecraft that is relatively motionless in the inertial space of the MI) is (0.05-0.10) m. Let us assume that the travel time of this distance is in the real range [360- 36000] s, i.e. [6 minutes - 10 hours]. Then the velocity increment ΔV will be (1.4 · 10 ^-4 -2.8 · 10 ^-6 ) m / s, which, in the presence of constant acceleration, will be respectively (3.9-10 ^-7 -7.7-10 ^{- 11} ) m / s ² .

The value of δV ₁ is the component of the error of the increment of speed from the factors acting on the distance traveled: the density of the photodetectors (δS ₁ ); operation of the orientation and stabilization system (SOS) of the spacecraft (δS ₂ ); and accuracy of initial MI arrest (δS ₃ ). The last two factors determine the accuracy of binding UCS to USC.

The density of the photodetector network, taking into account the safety grating, is 1 photodetector per 4 mm ² area, or the centers of the photodetectors are separated by 2 mm from each other. This is the component δS ₁ .

The spacecraft during operation produces evolution around the center of mass according to the logic of the SOS. CIPS can be located from the center of mass of the spacecraft at a distance guaranteed not to exceed 1 m. The error in maintaining the orientation of the spacecraft in space does not exceed 0.1 ⁰ . This means that in the limiting case, the point of contact of the MI with the KIPS wall can be separated from the point of radial direction at a distance not exceeding l = 1000 · sin (0.1 ⁰ ) = 1.75 mm, which, in turn, means an error in knowledge of the distance traveled:

$$\delta S_2=\left(R-r\right)\cdot [\mathrm{one}-\cos \left(\arcsin (\frac{l}{R-r})\right)],\text{(8)}$$

where r is the radius of the outer surface of the MI, 0,025 m

Then δS ₂ = (0.012-0.031) mm.

So, δS _1.2 = 2.031 mm.

The accuracy of IM arrest (δS ₃ ) as a completely effective action is estimated at 1 mm at r = 25 mm.

So, δS = 3.031 mm. Then, δV ₁ = 0.003031 / 360 = 8.4 · 10 ^-6 m / s at 6 min of the full working cycle of measurements - when the MI touches the array with photodetectors, and 8.4 · 10 ^-8 m / s - at 10 h full duty cycle.

Consider the second term (7) in equation (5) - the component of the acceleration error from the accuracy of event binding, i.e. on the accuracy of fixing times t ₁ and t ₀ . This accuracy is determined by the error of the onboard time taking, which is about 0.25 s onboard the spacecraft (δt = 0.25). Then δV ₂ is equal to 9.6 · 10 ^-8 m / s and 1.9 · 10 ^-11 m / s at 6 minutes and 10 hours, respectively, of the full working cycle of the measurements. The values of δV _{2 are} two orders of magnitude smaller than the values of δV ₁ ; therefore, the values of δV ₂ can always be neglected.

The ratio δV / ΔV, regardless of the gradation of the degrees of speed increment in percent, is from 3% to 6%.

2. Reliable acceleration constantly acting on the interval of the measurement work cycle, which is of purely theoretical interest, is determined from the equation of uniformly accelerated motion in the absence of the initial body velocity:

$$a=\frac{2S}{\Delta t^2},\text{(9)}$$

where S is the distance traveled, m;

Δt = t ₁ -t ₀ , s.

We differentiate (9) and proceed to the equation of independent errors:

$$\delta a=\frac{2}{\Delta t^2}\delta S+\frac{\mathrm{four}S}{\Delta t^3}\delta t.\text{(10)}$$

The set of factors affecting the accuracy of CIPS measurements is the same, the extreme values of the measurement duration (Δt) and the distance that the center of the MI inside CIPS (Rr) can go are the same as in item 1. We have δa = 2 · 0.003031 / (360) ² = 4.7 · 10 ^-8 m / s ² , at 6 min of the full working cycle of measurements, and 4.7 · 10 ^-12 m / s ² - at 10 h full duty cycle. The ratio δа / а, regardless of the gradations of the degrees of disturbing accelerations in percent, is also from 3% to 6%.

KIPS is precisely space technology, since it cannot work under gravity conditions, which allows us to call this meter space.

It should be noted that in order to isolate a factor disturbing the orbital motion of the spacecraft, it is necessary to exclude or responsibly take into account in the motion forecast all other disturbing factors of the same order of influence.

Claims (2)

1. A space speed increment meter containing an inertial mass and a position sensor, characterized in that the meter body is a hollow ball, on the inner surface of which a network of photodetectors is fixed, closed to digital equipment outside the ball, four identical external electromagnet, while the axis of the electromagnets intersect in the center of the sphere and are strictly attached to the satellite orbital coordinate system, the inertia is inside the case mass - a hollow ball, not a ferromagnet, with three holes equipped with lenses, the main optical axes of which are the main axes of the moving coordinate system with the origin in the center of mass of the ball, inside the ball are: four identical electromagnets uniformly spaced so that their axes intersect at the center of mass of the ball, three emitters (LEDs) in the number of main axes of the moving coordinate system, installed in the main foci of the lenses, power supply, switching unit, inductive charging circuit power source from external electromagnets, power source charge sensor, mass balance; an epoxy filler of a ball with channels for transmitting rays from emitters to lenses, while the position sensor is made as an optocoupler of three optocouplers, emitters and radiation emitters in which are respectively the LEDs inside the inertial mass and the network of addressable photodetectors on the inner surface of the housing. 2. The meter according to claim 1, characterized in that the function of the charge sensor of the power source is performed by a milliammeter in the external circuit through which the photocurrent passes.

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