RU2191988C2 - Two-coordinate inclination angle-data transmitter - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: given invention can be used in systems determining inclination angle of various devices and object for example, safety systems of various platforms, cranes, cars, excavators operating under conditions of complex terrain features. Principle of operation of transmitter is based on measurement of displacement of ball caused by inclinations of transmitter relative to horizon along two coordinates by capacitive converters. Transmitter comprises physical pendulum formed by current-conducting ball and thrust bearing with concave spherical surface. Oscillations of pendulum are damped by dielectric liquid filling case of transmitter. Transmitter provides for uninterrupted measurement of inclination angle in range from 0 to 30 degrees with increased accuracy and for reliability of measurement in wide temperature range. EFFECT: increased accuracy and reliability of measurement of inclinations angle in wide temperature range. 4 dwg

Description

 The invention relates to measuring equipment and can be used in systems for determining the angle of inclination of various devices and objects, in security systems of various platforms and specifically powerful cranes, excavators, wagons operating in difficult terrain, and can be used in any field of technology for measuring tilt angles.

 Gyroscopic angular displacement sensors are known for measuring the tilt angles of various objects, the principle of operation of which is based on the property of a free gyro with three degrees of freedom to keep the position of the axis of proper rotation in space unchanged.

 The disadvantage of these sensors is the complexity of their design and operation, as well as their high cost.

 A device is known - a capacitive tilt angle sensor - (AS USSR 1737260 dated 02.27.90), which comprises a housing with a sealed chamber made of insulating material half filled with an electrically conductive liquid, two electrically conductive hemispherical plates isolated from one another and from the housing and adjacent to the outer surface of the insulating wall of the chamber, and an electrical conductor in constant contact with the electrically conductive liquid, the chamber being made in the form of two concentric spherical shells check of different diameters, and an electrical conductor is in the form of six electrically interconnected rods, arranged in pairs symmetrically about the center of spherical shells in three mutually perpendicular planes.

However, this sensor has the following disadvantages:
- the sensor determines the current value of the angle of inclination, but without specific reference in determining the plane of the slope and the sign of the slope, which requires additional technical means to eliminate uncertainty;
- due to the difference in temperature coefficients of the volume expansion of the conductive liquid (in our case, mercury) and the insulating material of the shells, the “zero” of the sensor will shift when the temperature changes - and this reduces the measurement accuracy;
- rather complicated construction for this type of sensors and considerable laboriousness in manufacturing.

 A device is known - a tilt angle sensor (AS USSR 1751643 from 04.04.90), containing an ampoule partially filled with magnetic fluid, on which the primary winding and secondary windings connected in opposite directions are placed, the magnetic fluid being enclosed in an elastic dielectric sheath diamagnetic material.

However, this device has the following disadvantages:
- due to the used principle of determining the angle of inclination - the use of magnetic fluid - there is a significant delay in obtaining the measurement results (at least 2 min), which in real conditions is equivalent to a sensor failure and can lead to undesirable consequences, including an accident and possible failure complex equipment;
- instability of the zero of the sensor due to the instability (uncertainty) of the geometric dimensions of the elastic shell significantly reduces the accuracy of measuring the angle of inclination and requires, at best, periodic calibration;
- a narrow temperature range for the use of the sensor due to the dependence of the physico-mechanical parameters of the magnetic fluid on temperature;
- insignificant range of measurement of tilt angles (no more than 360 s).

 A device is known - a tilt angle sensor (ed. St. USSR 1752195 from 07.25.90), comprising a housing, a main and additional curved ampoule of non-magnetic material with a moving body with a permanent magnet and at least two fixed magnetically controlled contacts uniformly distributed along the ampoules, the ampoules being mounted perpendicular to each other, in each of the ampoules the movable body is made of non-magnetic material in the form of a rolling disk with a hole in the central part in which a permanent magnet is rigidly fixed, magnetically controlled contacts are located along the side walls of the ampoules, the distances between them are larger than the diameter of the magnet and smaller than the diameter of the disk, and the cross section of the ampoule is equidistant to the cross section of the disk, and the ampoules are filled with a liquid of the required viscosity (for example, glycerol with alcohol).

However, this sensor has the following disadvantages:
- does not provide continuity of measurement of tilt angles - tilt angles are determined discretely;
- low accuracy and instability of measuring the angle of inclination due to the instability of the position of the disk with a magnet in the ampoule due to the presence of backlash, changes in the characteristics of the magnet during operation and the instability of the fixation of ampoules with magnetically controlled contacts.

 A device is known - a sensor of the maximum angle of inclination of the object (ed. St. USSR 1795280 dated 10.10.90), comprising a body of insulated material, first and second contact plates located with a gap relative to each other, and a sensitive element in the form of a ball, limiter , the first contact plate is made U-shaped from an elastic material and the upper, rectilinear part is installed in the upper part of the housing, and the second contact plate is made flat and fixed in the lower part of the housing, while the diameter of the ball is less than the distance e between the rectilinear parts of the first contact plate, and the limiter is located above the lower, rectilinear part of the first contact plate at a distance of not less than the radius of the ball from the end of the straight wall of the housing.

However, this device has the following disadvantages:
- there is no continuous measurement of the angle of inclination, only the limiting angle of one sign and one plane is fixed;
- to fix the deviation of the object on the horizon plane in an arbitrary direction, the presence of 4 such devices is necessary;
- due to the lack of damping of ball movements in the presence of slight vibrations, malfunctions are possible and thereby the measurement accuracy is reduced;
- low reliability of the device due to the presence of a contact pair operating in conditions of low contact pressure;
- special adjustment of the system is required: contact pair 1 - contact pair 2 - ball, even when using a single material in the manufacture of plates and the ball, and this reduces the accuracy of measurements.

A device is known - a liquid pendulum (or an electrolytic sensor) used as a sensitive element for measuring deviation angles from the horizon plane (see "Details and Elements of Gyroscopic Instruments", State Union Publishing House of the Shipbuilding Industry, Leningrad, 1962, p. 293- 296, Fig. U.10), which contains a sealed enclosure filled with an electrolytic liquid, which is used as an electrolyte, while the conductive liquid is filled in the amount necessary to create air a bubble, which in an upright position approximately halfway covers the contact surface, two pairs of contacts located at an angle of 90 ^o , respectively, two pairs of terminals, and the contact surface of the housing is made in the form of a sphere. Electric current is supplied to the sensor through the terminals and the housing. When the pendulum case is rotated, the contact surface area with which the electrolyte is in contact changes, and, as a result of this, the resistance between the case and contacts changes.

However, this electrolytic sensor has the following disadvantages:
- a narrow range of measurement of tilt angles (tens of minutes);
- narrow temperature range due to the difference in volumetric expansion coefficients of the electrolytic liquid, the material of the casing and air.

 Closest to the technical nature and design of the proposed sensor is a tilt angle sensor (ed. St. USSR 954809 from 07/11/78), containing a sealed enclosure filled with dielectric fluid, fixed contacts mounted flush with the inner surface of the enclosure and made in the form of insulated one from the other tires, separated by recesses, and an electrically conductive ball, which is made with a specific gravity less than the specific gravity of the dielectric fluid, and the inner surface of the body has the shape of a body of revolution with curved generatrix.

However, this device has the following disadvantages:
- continuous measurement of the angle of inclination is not provided, only the maximum angle of inclination allowed for this design is recorded, and until the maximum angle of inclination is reached, there is no information about the current actual angle of inclination;
- low reliability of the measurement results due to the presence of weak electrical contact between the ball (with a lower specific gravity than the dielectric fluid) and the tires due to the low downforce;
- low dynamic accuracy of the sensor with possible sharp changes in the angle of inclination;
- a narrow temperature range of operability due to the difference in volumetric expansion coefficients of the dielectric fluid, ball and housing, which indirectly reduces the accuracy of measuring the angle of inclination;
- this design does not allow to determine the sign and plane of the angle of inclination.

 The purpose of the invention is the provision of continuous measurement of the angle of inclination while increasing the accuracy and reliability of measurement in a wide temperature range.

 This goal is achieved by the fact that two pairs of electrically conductive plates and an electrically conductive axisymmetric thrust bearing having a concave spherical surface, the radius of which is larger than the radius of the ball, which is mounted on this, are introduced into the angle sensor containing an electrically conductive ball placed in a sealed enclosure filled with dielectric fluid a thrust bearing, while a ball with a thrust bearing form a physical pendulum and the ball covers two pairs of electrically conductive plates whose symmetry planes are mutually orthogonal and go through the axis of symmetry of the thrust bearing, on which also lies the center of the concave spherical surface of the plates.

The essence of the invention lies in the fact that two pairs of plates are introduced into the sensor, each located relatively close together at an angle of 90 ^o , which allows you to determine the sign and plane of the angle of inclination without involving additional technical means - this ensures the certainty, reliability and accuracy of angle measurements tilt.

 Continuity of measurement is ensured by the fact that the principle of measuring capacitance is used: plates - ball - (thrust bearing - case). Moreover, at every current moment, the sensor provides information about the current angle of inclination, which is recorded.

 The increase in accuracy is determined by the chosen design: ball - thrust bearing (with a radius of a concave spherical surface greater than the radius of the ball), which allows reliably ensuring the operation of the physical pendulum (ball - thrust bearing) for functioning in the system: plates - dielectric fluid - ball - thrust bearing - housing.

 The increase in accuracy is also determined by the design of the spherically concave surfaces of the plates, repeating the spherical surface of the ball and located at the same distance from the surface of the ball in the zero initial position. The slightest change - the movement of the ball relative to the plates and the thrust bearing is immediately recorded as a change in the sensor’s capacitance, while the sign and plane of the angle of inclination are clearly determined - due to the presence of 4 plates located in mutually perpendicular planes.

 The increase in reliability is determined by the proposed rigid structure: body - plates - ball - thrust bearing, as well as the presence of dielectric damping fluid, which allows for a long time to ensure the accuracy of the sensor and reliability in a wide range of changes in ambient temperature. This is enhanced by the fact that most often the body, the thrust bearing, the plates and the ball are made of the same material.

 In FIG. 1 shows a general view of the design of the proposed sensor, FIG. 2 is a schematic diagram of the proposed physical pendulum; FIG. 3 is a kinematic diagram of the proposed physical pendulum when installing the sensor on a platform, the angle of which you want to measure, Fig. 4 is a diagram explaining the change in the gaps between the spheres of the sensor plates and the ball.

 In accordance with FIG. 1 sensor contains: ball 1, thrust bearing 2, case 3, cover (s) 4, insulator 5, dielectric fluid 6.

Эти колебания будут затухать из-за наличия силы трения качения и сил жидкостного демпфирования (наличия диэлектрической жидкости в корпусе датчика).The fundamentally proposed physical pendulum works as follows (see figure 2). When the ball 1 deviates from the vertical by an angle φ, a force equal to mgsinφ will act on the ball (where m is the mass of the ball, g is the acceleration of gravity) and causes the ball to move to the vertical. In contrast to the usual physical pendulum, the ball will rotate not only around the gain point - the center "O" of the thrust bearing of radius R _o , but because of the adhesion force F _sc around the center "O" of the ball with radius R _w . As a result of the restoring force, the ball will oscillate relative to the vertical of the place with a period equal to for small deflection angles:

These vibrations will damp due to the presence of rolling friction forces and liquid damping forces (the presence of dielectric fluid in the sensor housing).

, где δ - коэффициент трения качения, R_ш - радиус шара. Например, для δ = 1•10^-3 см, R_ш=1,5 см чувствительность составляет φ_min=2,3 дуг. мин. И это определяет достаточно высокую точность измерений угла наклона. А при увеличении диаметра шара и уменьшении коэффициента трения качения чувствительность датчика увеличивается, и тем самым увеличивается и точность измерения угла наклона.The sensitivity of the proposed sensor angle is determined by the expression:

where δ is the rolling friction coefficient, R _W is the radius of the ball. For example, for δ = 1 • 10 ^-3 cm, R _W = 1.5 cm, the sensitivity is φ _min = 2.3 arcs. min And this determines a sufficiently high accuracy of measurements of the angle of inclination. And with an increase in the diameter of the ball and a decrease in the coefficient of rolling friction, the sensitivity of the sensor increases, and thereby the accuracy of measuring the angle of inclination also increases.

 The sensor operates as follows (see figure 3).

When tilting the base, on which the angle sensor is mounted, by an angle φ ₁ relative to the vertical, the ball rolls along the thrust bearing, while the center of the ball moves from point O ₁ to point O ' ₁ (see Fig. 3). The displacement of the center of the ball in a plane perpendicular to the axis of symmetry of the thrust bearing will be Δy = - (R _o -R _W ) • sinφ ₁ . The offset along the axis of symmetry of the thrust bearing is ΔZ = (R _o -R _W ) (1-cosφ ₁ ).

 The displacement of the center of the ball in a plane perpendicular to the axis of symmetry of the thrust bearing is measured using two pairs of capacitive sensors, one of the plates of which is the ball itself, and the other two pairs of plates are isolated from the body and are concave spherical surfaces whose symmetry planes are mutually orthogonal and pass through axis of symmetry of the thrust bearing.

 When the center of the ball moves along the Y axis, the capacities C1 and C2 change, while the capacities C3 and C4 practically remain unchanged (see Fig. 4). In this case, the capacitance C2, formed by the lining, to which the ball has approached, increases, and the capacitance C1, formed by the lining, from which the ball is removed, decreases. This allows us to determine not only the value of the angle of inclination (by the change in capacities), but also the direction (sign) of the inclination (by the ratio of capacities C1 (3) and C2 (4)). Since the proposed angle sensor is designed for use in modern security systems (for example, heavy lifting cranes), the conversion of the output signals of capacitive sensors to the angle of inclination is carried out using special schemes for switching on two pairs of variable capacities as part of a special adapter (interface device), which connected to a microprocessor, in which the angle of inclination is determined by the appropriate algorithm, and in this case, you can take into account the existing nonlinear dependence in the value of the capacitance from the angle of inclination.

 Therefore, the proposed sensor provides a continuous change in the angle of inclination with high accuracy and reliability of measurements in a wide temperature range.

Claims (1)

 A two-coordinate tilt angle sensor containing an electrically conductive ball housed in a sealed enclosure filled with dielectric fluid, characterized in that the ball is mounted on an electrically conductive axisymmetric thrust bearing having a concave spherical surface with a radius greater than the radius of the ball, and the ball and thrust ball form a physical pendulum and ball cover two pairs of electrically conductive plates isolated from the body, the symmetry planes of which are mutually orthogonal and pass through the axis of symmetry of the thrust bearing, to Torah is also the center of the concave spherical surface of the plates.

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