DE102011106986B3 - Orientation sensor for space probe for determination of orientation of sensor housing in gravitational field in aerospace industry, has evaluation unit i.e. microprocessor, determining position of ball in inner side of sensor housing - Google Patents

Abstract

The sensor (100) has an electrical conductive ball (109) changing a switching state of contacts (101, 102) in a position (114b) by an electrical conductive connection between the contacts over the electrical conductive ball. An evaluation unit (111) i.e. microprocessor, determines the position of the ball in an inner side of a sensor housing (113). The contacts and other contacts (103-108) are checked for applying voltage. The switching state of all the contacts is changed such that the ball is moved from a direction of gravitational force (110) on the inner side of the sensor housing. Independent claims are also included for the following: (1) a space probe (2) a method for determining an orientation of a sensor housing in a gravitational field.

Description

The invention relates to a sensor and a method for determining an orientation of a sensor housing in a gravitational field acting on the sensor. Furthermore, the invention relates to a space probe with a similar sensor. The invention finds application in the space industry.

To explore space, numerous space probes have been and are being built to perform different tasks. It is known that in (large) space probes, which are to be targeted, for example, landed on planets, devices for determining the orientation of the spacecraft in the gravitational field of the planet are required, for example, a landing of the spacecraft on the planet in the correct orientation guarantee. For this purpose, a large number of technically advanced active position sensors and orientation sensors are known. Due to their complexity, these sensors are very expensive, prone to failure and must be protected against radiation. Furthermore, they require a lot of space in the spacecraft and have a high power requirement.

From the DE 43 41 918 C2 An electro-mechanical position change switch is known, which under the influence of the change position of its central axis in a gravitational field and under the influence of mechanical forces, by means of acting as an electrical anchor between funnel-shaped mass contacts and a plurality of directional contacts ball made of smooth, electrically conductive material and under influence a center axis position change against the gravitational direction and / or an acceleration is variable in position.

From the DE 10 2006 016 523 A1 is a tilt sensor with at least one body is known, which is movable along a predetermined path, and an optoelectronic unit for determining the position of the body, wherein the tilt sensor is surface mountable.

From the DE 102 61 961 A1 For example, there is known a tilt sensor comprising a sheet of injection molded polymer plastic, a member movable along the sheet, a position of the movable member along the sheet being dependent on a slope of the sheet with respect to a reference position, and detecting means for detecting the position of the movable member along the track and / or a temporal change in position of the movable member along the track.

From the EP 0 587 618 B1 For example, there is known a position sensor consisting of a housing containing a liquid, a substantially circular ball which floats freely in the fluid, and means for avoiding direct contact of the ball with the housing, being ensured by active means in that the ball is neutral with respect to the liquid and means for detecting and transmitting the orientation of the ball are present.

From the WO2004 / 020943 A1 is a tilt sensor with a moving in an interior of the tilt sensor ball is known, which moves by the action of a gravitational force between two positions as long as the tilt sensor is rotated about an axis with a certain torque.

Finally, out of the JP 11 351 845 A a tilt sensor for four or more directions, wherein the tilt sensor comprises an interior in the form of a polyhedron with a metal ball movable therein. The determination of the inclination of the sensor in a gravitational field is based on the determination of the position of the metal ball in the interior. For this purpose, the interior is scanned by means of light rays emanating from several light sources and receiving a plurality of light sensors.

For (small) space probes, which are to land on small celestial bodies, such as comets or asteroids, the known position and orientation sensors are not suitable because they are too heavy and too expensive, and have too large a space requirement. However, it is also necessary for such small space probes, depending on the application, to know the orientation of the space probe with respect to the heavenly body in order to be able to assess, for example, the measurement results recorded by the spacecraft.

The invention presented here describes a method of how a passive position sensor can be realized in a compact and radiation-resistant manner, so that it can be used for small compact exploration systems.

The object of the invention is to provide a sensor and a method which allow a simple, not susceptible to interference determination of any three-dimensional orientation of the sensor in a gravitational field. The sensor should be inexpensive to manufacture, have a low mass, a low overall volume, work reliably, have low energy consumption and be suitable in particular as an orientation sensor for space probes.

The invention results from the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims. Other features, applications and advantages of the invention will become apparent from the following description, and the explanation of embodiments of the invention, which are illustrated in the figures.

The device-related aspect of the object is achieved with a sensor for determining an orientation of a sensor housing in a gravitational field acting on the sensor. The term "gravitational field" in the present case, the field of gravitational acceleration, d. H. understood the acceleration acting on the sensor at the respective location of the sensor as the vector sum of gravitational acceleration and centrifugal acceleration. The term "orientation" is understood here to mean the alignment / rotation, in particular of the sensor housing, with respect to a reference system or an excellent direction (of gravity). The term "sphere" is used here in addition to the usual meaning "sphere": surface of revolution or special surface second order, described as the set of all points in the three-dimensional Euclidean space whose distance from a fixed point of space equal to a given positive real number r , also polyhedra, especially Catalan body understood.

The sensor according to the invention comprises at least the sensor housing having a housing interior in the form of a sphere, a ball movable within the housing interior with a conductive surface, a multiplicity of electrical contacts spaced apart from one another and distributed on an inner side of the sensor housing, each being spaced from one another and from the sensor housing are electrically isolated, and an evaluation unit connected to the electrical contacts, which is designed and arranged such that the orientation of the sensor housing in the gravitational field can be determined by an evaluation of an electrical switching state of the contacts. The switching state of the electrical contacts is changeable in that the ball is moved by a force acting on this gravity to a dependent of a direction of gravity position on the inside of the sensor housing and there establishes an electrically conductive connection between at least two electrical contacts on the conductive ball surface , Through this conductive connection between the at least two contacts, the switching state of these at least two contacts is changed, d. H. they are then conductively connected. Since the positions of the individual electrical contacts on / on the inside of the housing interior are known, the direction of the force acting on the sensor gravity and thus the orientation of the sensor housing in the gravitational field can be determined from the determination of those contacts whose switching state has changed.

The ball is preferably in contact with the sensor housing only via the electrical contacts arranged there. For this purpose, the electrical contacts are distributed in such a manner in the inside of the sensor housing that, for each layer in which the ball is in contact with the sensor housing, the ball connects at least two electrical contacts to one another in an electrically conductive manner. The ball diameter, the volume and the shape of the volume inside the housing in which the ball can move freely, are further coordinated so that the ball in at least one position in this volume has no contact with one of the electrical contacts and on the other hand, the volume in which the ball can move freely without being in contact with the at least two contacts is minimal, so that the sensor has a short reaction time and damage to the sensor due to accelerations occurring and thus high speeds of the ball is prevented.

A preferred embodiment of the sensor according to the invention is characterized in that the housing interior has the shape of a sphere, a cuboid or a regular polyhedron. The electrical contacts preferably have a contact surface in the form of a circle, a rectangle or a regular polygon. To damp the movement of the ball in the housing interior, the housing interior preferably has an electrically non-conductive liquid. As a result, with strong accelerations applied to the sensor, the resulting velocity of the ball does not become so great as to damage or destroy the sensor.

A further preferred development is characterized in that the housing interior is evacuated. This causes a particularly short reaction time of the sensor. Preferably, the ball is further formed as a hollow body and / or made of a material having a low specific weight.

The sensor according to the invention is further distinguished by the fact that the evaluation unit is a microprocessor with which a voltage can be applied cyclically to each of the electrical contacts to determine the position of the ball on the inside of the sensor housing and adjacent or all other contacts to the presence of a voltage being checked. If this voltage is applied to a contact which is in electrically conductive connection with the ball, then this voltage can be tapped at all other electrical contacts, with which there is also an electrically conductive contact via the ball.

The procedural aspect of the object is achieved by a method for determining an orientation of a sensor housing in a gravitational field acting on the sensor, wherein the Sensor the sensor housing having a housing interior in the form of a sphere, a movable within the housing interior ball with a conductive surface, a plurality of on / on an inside of the housing, spaced from each other and distributed electrical contacts, which are electrically isolated from each other and from the sensor housing, and an evaluation unit connected to the electrical contacts, which determines the orientation of the sensor housing in the gravitational field by evaluating an electrical switching state of the contacts. In this case, the acting switching state of the contacts is changed by the ball is moved by a gravity on this dependent on a direction of gravity position on the inside of the sensor housing, and the ball at the position by an electrically conductive connection between at least two of Contacts via the electrically conductive ball changes the switching state of the at least two contacts and further the evaluation unit is a microprocessor with which a voltage is applied to determine the position of the ball on the inside of the sensor housing, cyclically to each of the electrical contacts and adjacent or all others Contacts are checked for the presence of a voltage.

Further preferred embodiments of the method according to the invention result from an analogous application of the statements made above for the sensor according to the invention to the method according to the invention.

Finally, the invention relates to a spacecraft with a sensor according to the invention described above, wherein an orientation of the spacecraft based on the determined orientation of the sensor housing in the gravitational field and a known positional arrangement of the sensor on the spacecraft can be determined. The sensor according to the invention is simple in design, maintenance-free, cost-effective and with low sensor mass. The angular resolution of the detectable with the sensor orientation is u. a. depending on the surface density of the arranged on the inside of the sensor housing electrical contacts. The larger the surface density, the greater the angular resolution of the orientation that can be determined with the sensor.

Further advantages, features and details will become apparent from the following description in which an embodiment is described in detail, in conjunction with the drawings.

Show it:

1 a schematic representation of a cross section through a sensor according to the invention, and

2 a principle circuit for evaluating the switching state of the electrical contacts.

1 shows a schematic representation of a cross section through a sensor according to the invention. The illustrated embodiment includes the conductive ball 109 in a closed housing 113 , The housing 113 has on all inner sides in the direction of the housing interior protruding ribs 1 - 8th on, in turn, each electrically conductive contacts 101 - 108 exhibit. The contacts 101 - 108 are opposite the case 113 and the other ribs 1 - 8th electrically isolated. The electrical contacts 101 - 108 are with the evaluation tool 111 via electrical lines 112 connected. The electrical contacts 101 - 108 are present from the evaluation 111 so electrically connected, that always an active, under tension contact, eg. 101 . 103 . 105 . 107 , in addition to a non-energized contact, eg. 102 . 104 . 106 . 108 to come to rest.

2 shows a principle circuit for evaluating the switching state for such a pair of electrical contacts 101 . 102 , The functioning of the present sensor is based on the fact that even with the slightest gravity, the conductive ball 109 in the direction of gravity 110 is moved so an electrically conductive connection between the contacts 101 and 102 is produced, which leads to a switching state change of the contacts, which in turn can be evaluated by the evaluation means for determining the orientation in the gravitational field.

In the 1 this is illustrated by the fact that the center of the sphere 109 from the position 104a by the action of gravity 110 , For example, after landing a equipped with the sensor spacecraft on a comet, is moved down in the picture, so that on the electrically conductive surface of the ball, an electrical connection between the contact 101 and the contact 102 comes about. This ensures that a voltage is cycled by the evaluation means 111 , a microcontroller, DSP or FPGA, to each contact 101 . 103 . 106 . 107 is created, is detected via a corresponding digital evaluation. By the association between the powered contact 101 . 103 . 106 . 107 and reactive contact can thus the position of the ball 109 inside the housing or the position 114b be determined with sufficient accuracy.

When sizing the inside of the housing, in which the ball 109 should move freely should be noted that the distance between the individual ribs 1 - 8th in terms of the ball 109 so great is that there is no inadvertent contact between bullet 109 and the electrical contacts 101 - 108 comes about. Furthermore, the distance should be chosen so small that a desired contact between ball 109 and the electrical contacts 101 - 108 closed securely. Furthermore, it should be noted that the inside of the housing in which the ball 109 can move freely, the ball 109 does not allow much freedom of movement to a) allow a quick indication and b) in case of strong accelerations the resulting velocity of the ball does not become so great as to destroy the chamber. For this purpose, the housing interior may be filled with a non-conductive liquid (eg oil) to control the movement of the ball 109 to dampen.

For use of the present sensor in small light space probes, where the system weight is greatly reduced, there is the possibility of the ball 109 to realize as a hollow body and to evacuate the housing interior. Thus, an undamped system is realized in the last consequence, but that by the greatly reduced mass of the ball 109 remains uncritical.

If the position resolution and thus the achievable angular resolution of the orientation of the arrangement shown are not sufficient, becomes the ball 109 Instead of the ribbed square, a polyhedron with several contact surfaces 101 - 108 or contact points used. This is preferably designed such that the ball 109 in the general spatial case on three different contact elements 101 - 108 stably supports and connects them electrically. Each resulting triplet of contact elements 101 - 108 describes a clear spatial direction with respect to the polyhedron. Not every combination of contact elements 101 - 108 is possible, but only immediately adjacent contacts 101 - 108 through the ball 109 can be connected, it is possible several sufficiently far away from each other contact elements 101 - 108 in a group with a common connection to the number of required connection cables 112 to the evaluation means 111 keep as low as possible. In this variant, it only needs to be taken care that due to the neighborhood relations each tripartite combination of contact groups remains unambiguous, ie that three groups only at one point in the polyhedron form a triangle of neighboring contacts 101 - 108 span. As already described above, in this more general case too, the evaluation is carried out by stimulating individual contact groups and evaluating the responses of the others. Since the stimulation and evaluation of all circuits preferably takes place in a digital component (microcontroller, DSP or FPGA), the sensor according to the invention requires no interface circuitry to adapt signal levels. Only the number of contact surfaces 101 - 108 , which is given by the desired spatial resolution, determines the electrical properties of the interface.

When using the described sensor on board a spacecraft, the location, ie the location and orientation of the sensor on the spacecraft, with respect to the spacecraft known. With the orientation determined by the sensor, the orientation of the spacecraft with respect to the gravity field acting on the spacecraft as well as the sensor can be uniquely determined. In the illustrated configuration of the sensor, layers of 45 degrees with respect to the direction of gravity 110 appear as the ball 109 in this case, the electrical contacts via a room corner of the housing interior 101 - 108 can close.

LIST OF REFERENCE NUMBERS

1-8

Contact socket

100

sensor

101-108

electrical contacts, each electrically isolated from the housing

109

Sphere, polyhedron, catalan body with electrically conductive surface

110

Gravity = sum of gravitational force and centrifugal force

111

evaluation

112

electric lines

113

sensor housing

114a

Position of the ball, without touching any of the electrical contacts

114b

Position of the ball on the inside of the sensor housing, which results from a gravitational force acting on the ball, depending on the direction of gravity

Claims (7)

Sensor ( 100 ) for determining an orientation of a sensor housing ( 113 ) in a gravitational field acting on the sensor, wherein the sensor ( 100 ) at least comprises: - the sensor housing ( 113 ) with a housing interior in the form of a sphere, - a ball which is movable within the interior of the housing ( 109 ) having a conductive surface, - a plurality of on / on an inner side of the sensor housing ( 113 ) spaced apart and distributed electrical contacts ( 101 - 108 ), each from each other and from the sensor housing ( 113 ) are electrically isolated, and - one with the electrical contacts ( 101 - 108 ) associated evaluation unit ( 111 ) which is designed and arranged such that the orientation of the sensor housing ( 113 ) in the gravitational field by an evaluation of an electrical switching state of the contacts ( 101 - 108 ) is determinable, wherein the Switching state of the contacts ( 101 - 108 ) is changeable by the fact that the ball ( 109 ) by a force of gravity ( 110 ) to one of a direction of gravity ( 110 ) dependent position ( 114b ) on the inside of the sensor housing ( 113 ) is movable and the ball ( 109 ) at the position ( 114b ) by an electrically conductive connection between at least two of the contacts ( 101 - 108 ) via the electrically conductive ball ( 109 ) the switching state of the at least two contacts ( 101 . 102 ), and the evaluation unit ( 111 ) is a microprocessor with which to determine the position ( 114b ) the ball ( 109 ) on the inside of the sensor housing ( 113 ), cyclically to each of the contacts ( 101 - 108 ) a voltage is applied and adjacent contacts ( 101 - 108 ) or all other contacts ( 101 - 108 ) are checked for the presence of a voltage. Sensor ( 100 ) according to claim 1, characterized in that contact surfaces of the contacts ( 101 - 108 ) have the shape of a circle, a rectangle or a regular polygon. Sensor ( 100 ) according to one of claims 1 or 2, characterized in that the housing interior has an electrically non-conductive liquid. Sensor ( 100 ) according to one of claims 1 to 3, characterized in that the housing interior is evacuated. Sensor ( 100 ) according to one of claims 1 to 4, characterized in that the ball ( 109 ) is designed as a hollow body. Spacecraft with a sensor ( 100 ) according to one of claims 1 to 6, wherein an orientation of the spacecraft based on the determined orientation of the sensor housing ( 113 ) in the gravitational field and a known positional arrangement of the sensor ( 100 ) can be determined on the spacecraft. Method for determining an orientation of a sensor housing ( 113 ) in one on the sensor ( 100 ) acting gravitational field, wherein the sensor ( 100 ) the sensor housing ( 113 ) with a housing interior in the form of a sphere, a ball movable within the interior of the housing ( 109 ) having a conductive surface, a plurality of on / on an inside of the housing, spaced from each other and distributed electrical contacts ( 101 - 108 ), from each other and from the sensor housing ( 113 ) are electrically isolated, and one with the electrical contacts ( 101 - 108 ) associated evaluation unit ( 111 ), which determines the orientation of the sensor housing ( 113 ) in the gravitational field by evaluating an electrical switching state of the contacts ( 101 - 108 ), wherein the switching state of the contacts ( 101 - 108 ) is changed by the ball ( 109 ) by a force of gravity ( 110 ) to one of a direction of gravity ( 110 ) dependent position ( 114b ) on the inside of the sensor housing ( 113 ) and the ball ( 109 ) at the position ( 114b ) by an electrically conductive connection between at least two of the contacts ( 101 - 108 ) via the electrically conductive ball ( 109 ) the switching state of the at least two contacts ( 101 . 102 ) and the evaluation unit ( 111 ) is a microprocessor with which to determine the position ( 114b ) the ball ( 109 ) on the inside of the sensor housing ( 113 ), cyclically to each of the contacts ( 101 - 108 ) a voltage is applied and adjacent contacts ( 101 - 108 ) or all other contacts ( 101 - 108 ) are checked for the presence of a voltage.

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