RU2005991C1 - Two-coordinate pickup of angular position - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: with turn of lever around one axis change of value of light flux occurs which is partially screened with control element. This leads to change of signal across output of one photodetector. Same result is obtained with turn of lever around other axis 5. Signal at output of other photodetector also changes. There are different versions of manufacture of control element including its fabrication in the form of two opaque plates interconnected so that they coincide with two side faces of tetrahedral isosceles pyramid with right angles confined between two side faces. EFFECT: increased reliability due to exclusion of additional kinematic couplings between lever intended for fastening with inspection object and control elements of two pickups of angle of turn. 4 cl, 2 dwg

Description

 The invention relates to devices for determining the angular position of an object relative to two independent axes using optical measurement methods. This sensor can, in particular, be used to create systems for manual control of computers and actuators.

 A known linear position sensor [1], containing a radiation source that creates a parallel light beam, a radiation receiver and an opaque control element that partially or completely blocks the radiation flux depending on its position. The output signal of the receiver determines the linear displacement of the control element relative to the axis perpendicular to the optical axis of the sensor.

 The specified sensor, being single-channel, is able to determine only the linear position of the object and does not provide the ability to determine the angular position of the object simultaneously from two coordinates.

 Known two-coordinate angle sensor [2], adopted for the prototype, comprising a housing, a lever fastened to the housing by a hinge with the possibility of angular displacements relative to two mutually perpendicular axes, two angle sensors installed so that their optical axes are mutually perpendicular, each rotation angle sensors is made in the form of a sequentially installed radiation source, a control element associated with a lever, and a radiation receiver. The sensor also contains two arcs installed in the housing perpendicular to each other on the axes with the possibility of rotation of the arcs in two mutually perpendicular directions. Slots are made in the arcs, which, at the indicated arrangement of the arcs relative to each other, form an opening through which the lever is passed. A control element is fixed on the axis of each arc, made in the form of a translucent sector with a given distribution of the transmittance of radiation along the arc of the sector. The transmittance of radiation monotonically increases from one end of the arc of the translucent sector to the other end. When the control lever is rotated in a ball joint in a certain direction, it rotates the arc installed in the perpendicular direction, with which the translucent sector attached to it rotates. The latter, depending on the angle of rotation of the lever, changes the radiation flux incident on the receiver.

 The disadvantage of this sensor is the presence in it of a mechanical assembly in the form of two arcs intersecting at right angles, through which the rotation of the control lever is transmitted to the control element, that is, a translucent sector. The presence of such a mechanical assembly in the design of the sensor may introduce additional error in its readings due to backlash and friction in this assembly, which reduces the reliability of the sensor. The execution of the control element in the form of a translucent sector with a given distribution of the transmittance of radiation along the arc can also reduce the reliability of the sensor, since the occurrence of local pollution on the surface of the translucent sector can lead to sharp jumps in the output signal and, consequently, to a significant error in the control system. In addition, the presence of the indicated mechanical assembly in the sensor design, as well as the need for a separate control element in each angle sensor, complicates the sensor design.

 The aim of the invention is to increase the reliability of the sensor through the use of one control element common to both sensors of the angle of rotation and directly attached to the lever without an intermediate transmission.

 This goal is achieved in that, in contrast to the prototype, each rotation angle sensor is equipped with a diaphragm with a hole of a given configuration installed between the radiation source and the radiation receiver, rotation angle sensors are installed so that their optical axes intersect each other, and a control element common to both rotation angle sensors, fastened with a lever and installed in the zone of intersection of the optical axes of the rotation angle sensor. The properties of the control element common to both sensors of the rotation angle - its shape and distribution of the transmittance of radiation can be chosen very arbitrarily. The configuration of the aperture opening is set in accordance with the selected properties of the specified control element in such a way as to obtain the desired dependence of the radiation flux to the receiver from the position of the lever.

It is also advantageous that the control element, the total angle of rotation for the two sensors may be configured as two opaque plates connected to each other so that they coincide with two side faces of tetrahedral isosceles pyramid with an angle between the side faces equal to ^90, the rib pyramids combined with the axis of the lever, and the top of the pyramid is aligned with the center of rotation of the lever. The specified form of the control element is the simplest.

A

(ρ²(Ψ)-ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ )d

= K·φ+a , где R - зависимость выходного сигнала приемника излучения от падающего потока излучения;
φ- угол отклонения рычага;
К и а - постоянные параметры;
A - плотность потока излучения.It is also advisable that the holes in each diaphragm be limited by two straight lines passing through the point of intersection of the diaphragm plane, the axis of rotation of the lever parallel to the optical axis of the angle sensor, and two curves, one of them is an arc of a circle of radius ρ ₀ , and the other is a curve with a variable radius of curvature ρ (Ψ) with centers at the indicated intersection point of the diaphragm plane, the rotation axis, ρ (Ψ) must satisfy the condition ρ (Ψ)> ρ ₀ and is determined from the solution of the equation R

A

(ρ ² (Ψ) -ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ ) d

= K · φ + a, where R is the dependence of the output signal of the radiation receiver on the incident radiation flux;
φ is the angle of deviation of the lever;
K and a are constant parameters;
A is the radiation flux density.

 The indicated shape of the hole in the diaphragms makes it possible to obtain a linear dependence of the output signal of the two-coordinate sensor on the angle of deviation of the lever when using a radiation receiver with an arbitrary dependence of the output signal on the incident radiation flux.

 It is also advisable that the control element common to both sensors of the rotation angle can be made in the form of an opaque cone, mounted so that its top is aligned with the center of rotation of the lever, and the axis coincides with the axis of the lever. The specified form of the control element allows you to determine the angular position of the part, fixed in a two-coordinate sensor and rotating around its axis of symmetry.

 In FIG. 1 shows a sensor circuit with a control element common to both angle sensors in the form of an isosceles pyramid; in FIG. 2 - options for the shape of the diaphragm in the angle sensor for cases of linear and nonlinear radiation receivers.

The two-coordinate angle position sensor (Fig. 1) contains two identical mutually perpendicular rotation angle sensors with optical axes 1 and 2. The lever 3 is mounted on the suspension with a possibility of rotation relative to mutually perpendicular axes 4 and 5. As such a suspension, a rotation axis fixed in two bearings mounted on the housing (not shown in FIG. 1). In the middle of this axis, perpendicular to it, the second axis of rotation is fixed, on which the lever is fixed. The lever 3 can be rotated around the second axis and independently, together with the second axis, around the first axis. A control element 6 is fixed on the lever 3, which is common for both rotation angle sensors. Among the many possible options for the control element 6, the most simple will be two opaque plates fastened together at an angle less than or equal to 90 ^about (Fig. 1).

 Also, a ball joint with the possibility of an additional lever 3 around its axis can be used as a suspension. In this case, the control element 6 should be a body of revolution, so that its projections on the plane perpendicular to the optical axes 1 and 2, do not depend on the rotation of the lever around its axis. The simplest such control element 6 will be an opaque cone, the axis of which is aligned with the axis of the lever 3, and the vertex coincides with the center of rotation of the lever 3.

 The radiation sources consist of LEDs 7 and 8 located at the focus of the lenses 9 and 10, forming two parallel light beams. Flat lenses 11 and 12 are fixed on the lenses, forming bundles of a given configuration. Behind the control element 6, common to both angle sensors, collecting lenses 13 and 14 are installed, focusing the transmitted radiation on radiation detectors 15 and 16. Photodiodes or photoresistors can be used as radiation detectors. It is possible to install diffuse diffusers in front of the radiation receivers to weaken the requirements for the accuracy of combining the light flux with the sensitive area of the radiation receiver.

 The position of the lever 3 determines the degree of overlap of the light beams by the control element 6, and the output signals from the radiation receivers uniquely determine the angular position of the lever relative to each of the two mutually perpendicular axes.

 The spatial distribution of the transmittance of radiation by the diaphragms 11, 12 and the control element 6 can be very diverse, but coordinated with each other to obtain a given output characteristic of the angular position sensor. In particular, for the above simplest versions of the opaque control element 6 and the radiation receiver 5 with a linear characteristic, the hole in the opaque diaphragm 11 in FIG. 2 is limited by two segments of lines 17-19 and 18-20 passing through the point of intersection of the diaphragm 11 plane 21 with the axis of rotation 5 of the lever parallel to the optical axis 1 of the angle sensor; and two curves 17-18 and 19-20, which are arcs of a circle with centers at point 21.

^A

, где R - зависимость выходного сигнала приемника излучения от падающего потока излучения;
φ- угол отклонения рычага;
К и a - постоянные параметры;
A - плотность потока излучения.For a radiation receiver 5 with a non-linear characteristic (for example, a photoresistor), the hole in the opaque diaphragm 11 in FIG. 2 is limited by two segments of lines 22-25 and 23-26 passing through the point 24 of intersection of the plane of the diaphragm 11 with the axis of rotation 5 of the lever parallel to the optical axis 1 of the angle sensor; and two curves 25-26 and 22-23, one of them being an arc of a circle of radius ρ ₀ , and the other curve with a variable radius of curvature ρ (Ψ) centered at 24. ρ (Ψ) is determined from the solution of equation ^R

^A

where R is the dependence of the output signal of the radiation receiver from the incident radiation flux;
φ is the angle of deviation of the lever;
K and a are constant parameters;
A is the radiation flux density.

 The initial working point of the radiation receiver is set due to the additional transparent region 27 on the diaphragm 11, which is not blocked by the control element 6 at all positions of the lever 3.

 The output electrical signals with a radiation receiver are then used in analog form or converted into a digital code as the results of measuring the lever deviation angles with respect to two independent axes.

 The use of one control element, common to both sensors of the angle of rotation and directly attached to the lever without an intermediate transmission, eliminates friction and play in the transmission elements, reduces the number of these elements and thus increases reliability and simplifies the design of the sensor. (56) 1. Vorontsov L.I. Photovoltaic control systems for linear quantities. M.: Mechanical Engineering, 1965, p. 48, FIG. 23.

 2. US patent N 4731530, CL. G 01 D 5/34, 1988.

Claims (4)

 A TWO-ORDER ANGULAR SENSOR, comprising a housing, a lever fastened to the housing by a hinge with the possibility of angular displacements relative to two mutually perpendicular axes, two rotation angle sensors installed so that their optical axes are mutually perpendicular, each of the rotation angle sensors is made in the form of sequentially installed a radiation source bonded to the housing, a control element coupled to the lever, and a radiation receiver bonded to the housing, characterized in that, for the purpose of for reliability, each rotation angle sensor is equipped with a diaphragm with a hole of a given configuration installed between the radiation source and the radiation receiver, rotation angle sensors are installed so that their optical axes intersect each other, and the control element common to both rotation angle sensors is fastened with lever and installed in the zone of intersection of the optical axes of the angle sensors. 2. The sensor according to claim 1, characterized in that the control element common to both sensors of the rotation angle is made in the form of two opaque plates fastened together so that they coincide with two side faces of a tetrahedral isosceles pyramid with an angle between the side faces 90 ^o С, the edge of the pyramid is aligned with the axis of the lever, and the top of the pyramid is aligned with the center of rotation of the arm. 3. The sensor according to claim 1, characterized in that the hole in each of the diaphragms is limited by two straight lines passing through the point of intersection of the diaphragm plane with the axis of rotation of the lever parallel to the optical axis of the angle sensor and two curves, one of them is an arc of a circle of radius ρ ₀ , and the other is a curve with a variable radius of curvature ρ (Ψ) with centers at the point of intersection of the diaphragm plane with the rotation axis, ρ (Ψ) must satisfy the condition ρ (Ψ)> ρ ₀ and is determined from the equation
R

A

(ρ ² (Ψ) -ρ $\genfrac{}{}{0ex}{}{\text{2}}{\text{0}}$ ) d

= K
where R is the dependence of the output signal of the radiation receiver from the incident radiation flux;
φ is the angle of deviation of the lever;
K and a are constant parameters;
A is the radiation flux density.  4. The sensor according to claim 1, characterized in that the control element common to both rotation angle sensors is made in the form of an opaque cone mounted so that its top is aligned with the center of rotation of the lever, and the axis coincides with the axis of the lever.

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