WO1993008614A1 - Procede et systeme de stabilisation mecanique - Google Patents

Procede et systeme de stabilisation mecanique Download PDF

Info

Publication number
WO1993008614A1
WO1993008614A1 PCT/FI1992/000245 FI9200245W WO9308614A1 WO 1993008614 A1 WO1993008614 A1 WO 1993008614A1 FI 9200245 W FI9200245 W FI 9200245W WO 9308614 A1 WO9308614 A1 WO 9308614A1
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WO
WIPO (PCT)
Prior art keywords
contact
support base
effectively
free force
relation
Prior art date
Application number
PCT/FI1992/000245
Other languages
English (en)
Inventor
Markku Sarjala
Original Assignee
Markku Sarjala
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Markku Sarjala filed Critical Markku Sarjala
Publication of WO1993008614A1 publication Critical patent/WO1993008614A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/18—Means for stabilising antennas on an unstable platform

Definitions

  • the invention relates to a method according to the introductory part of claim 1 for stabilization of a mechanical body irrespective of the movements of the bearer.
  • the body remains and can be maintained at a desired position in relation to the earth gravity field, although the bearer carrying the body is tilted and/or moves in different directions.
  • An embodiment in which applica ⁇ tion of the method is very useful, is the satellite antenna of a ship.
  • a problem with this method is the limited rate of stabilization. As the rates of acceleration and the kinetic velocities of the bearer exceed the maximum response rate of the actuator and its control devices, the body is moved from the desired position. Further ⁇ more, the expensive cost of actuators and detectors limits the field of use of stabilization.
  • Another currently used method of stabilization is based on utilizing the gyratory force maintaining the position of the rotation axis of a balancing wheel.
  • the body is thus supported above its mass centre, whereby the body is gravitated into the desired position.
  • Problems with this method include the change in position caused by high acceleration rates sideways as well as turning of the gyroscopic axis caused by the accelerations directed to the gyroscope.
  • the method of the invention is mainly characterized in that the body is supported substantially and effectively at its mass centre in a way that the total torque induced by the inertial forces caused by accelerations effective on the body is eliminated, the kinetic state of the body and/or the support base is measured for maintaining the position of the body in relation to the earth gravity field and for removing the effect of forces, par ⁇ ticularly friction, changing the position of the body, and that on the basis of the measuring results, the position of the body is maintained by forces acting substantially and effectively on a contact- free principle which forces are generated on the basis of the measuring results when needed.
  • the method of the invention is thus based on supporting the active body to be stabilized, such as a satellite antenna, at its mass centre or close to its mass centre with minimized friction.
  • the mass centre can therefore be transferred to a point which is suitable for applying the method and particularly required by the uses of the active body by providing the ⁇ active body with at least one counterweight.
  • the said in- tegrated body can thus be supported by a support frame connected to the bearer, whereby the mass centre of the integrated body is elevated from the surface of the bearer.
  • the integrated body being thus sup- ported, the total torque induced by the inertial forces caused by accelerations in all directions in the integrated body is eliminated.
  • the integrated body refers to a combination which, due to practical requirements, is composed of an active body, such as a satellite antenna, the direction of which must be maintained at the level of precision of less than one degree towards the satellite direction irrespective of movements of the bearer, and of one or several counterweights structurally required for achieving the said uses of the active body.
  • an active body such as a satellite antenna
  • the method of the invention is based on the fact that although the body is supported at the mass centre or close to it with minimized friction, forces are induced at the bearing point by friction, Coriolis force etc. which tend to change the position of the body; i.e. the method is used for correcting the inching, or creeping, which tends to change the position of the body. This is achieved by using forces which are induced on the contact-free principle. This is particularly advantageous because — after correct ⁇ ing the position of the body, the effect of forces changing the position of the body being eliminated— the said body is subjected to no support reactions caused by actuators used for the said correction which would affect the position of the body, e.g. by forces of support reactions between the said body and the bearer.
  • a force caused by the movement of a fluidized medium a force induced by a change in the electromagnetic field, a force based on the change in the relative position and/or in the kinetic energy, particular a rotating means placed in connection with the body, such as a balancing wheel, can be used.
  • a force presented above, induced on the contact-free principle when needed do not induce forces of support reactions between the body and the bearer when it is not necessary to use the said forces to change the position of the body e.g.
  • the fluidized medium refers in this context to fluids, gases and/or particles brought by at least one actuator connected to the body into a kinetic state in which the said correction of the position of the body is carried out by forces induced by changes in the kinetic state of the fluidized medium. Conse ⁇ quently, the body is subjected to a reaction force and/or a collision force induced by the kinetic state of the fluidized medium.
  • a particularly advantageous medium is air.
  • the method of the invention makes it possible to use a so-called slow control system, whereby the stabilizing devices applying the method are consider ⁇ ably less expensive to manufacture than the present systems which are based on the utilization of active actuators of different types.
  • the slow control system corrects the creeping of the position of the body by controlling the function of the actuators in a way that the correction of the position is achieved.
  • the slow control system refers in this context to a system with a response rate which is at least one decade lower than the maximum kinetic velocity of the support frame. For example, if the frame of a ship rolls max. 2°/s around its longitudinal axis, the response rate of the slow control system is smaller or equal to 0.2°/s.
  • Fig. l shows a schematic side view of an embodi ⁇ ment of the method according to the invention for stabilizing a satellite 15 receiving antenna in a ship
  • Fig. 2 shows schematically different kinetic states of a ship, particularly in a situa ⁇ tion of placing the satellite receiving 20 antenna as shown in Fig. 1, for illus ⁇ trating the forces effective on the satellite receiving antenna,
  • Fig. 3 shows an embodiment for a schematic diagram 25 of the control system of actuators func ⁇ tioning on the contact-free principle and placed in the satellite receiving antenna,
  • Fig. 4 shows an example of a fan arrangement 30 placed in connectionwith the counterweight of the satellite antenna shown in Fig. 1, whereby the force induced by a change in the kinetic state of a fluidized medium, in this case air, is generated for elimin- 35 ating the effect of forces tending to change the position of the body (satellite antenna)
  • Fig. 5 is a cross-sectional view (line V-V) of
  • Fig. 1 illustrating the utilization of an electromagnetic field for eliminating the effect of forces tending to change the position of the body on the contact-free principle
  • Fig. 6 illustrates the utilization of kinetic energy by a balancing wheel arrangement for eliminating the effect of forces tending to change the position of the body on the contact-free principle
  • Fig. 7 shows a second embodiment modified of the illustration of Fig. 1.
  • Figure 1 shows schematically an antenna arrangement 1 to be mounted on a ship 5 as the support base and forming the active body, particularly a TV satellite receiving antenna.
  • a rotating mechanism 2 for turning and tilting the antenna arrangement l.
  • a counterweight 7 is connected to the antenna arrangement 1 in a way that the mass centre of the integrated body is not changed as a result of rotating and tilting required by the function of the antenna arrangement 1.
  • a counterweight 3 is fixed to the active body which is composed of parts l, 2 and 7 and to be stabilized.
  • the integrated body 1, 2, 7, 3 thus formed is supported at its mass centre by support 4 with small friction on a support frame 5a ixed on the deck of the ship 5 in a way that the mass centre and the bearing point is placed substan ⁇ tially and effectively above the deck of the ship 5 in a way that the counterweight 3 is at its lower part apart from the deck of the ship 5.
  • the support is made so that the operational body, i.e. particularly the antenna arrangement 1 maintains its direction with the horizontal heading line of the ship 5. In other respects, the support allows the free turning of the body in relation to the support frame 5a and thus to the ship 5.
  • Creeping of the position of the integrated body caused by friction, Coriolis force or for other reasons, such as a change of the position of the active body 1, 2 and 7 in relation to the integrated body, is corrected by actuators 6 connected to the slow control system (Fig. 3), i.e. in this embodiment (Fig. 1) by fans arranged in connection with the counterweight 3, particularly in its lower part, as shown in Fig. 4.
  • the in- tegrated body 1, 2, 7, 3 and its support frame 5a are mounted inside a fairing, i.e. a so-called radome 8 being part of the support base and/or mounted thereto.
  • a fairing i.e. a so-called radome 8 being part of the support base and/or mounted thereto.
  • the ship 5 is in several different kinetic states simultaneously.
  • the ship rolls with a certain natural frequency f 1 .
  • This movement causes crosswise accelera ⁇ tions which are repeated at the said natural frequency.
  • the ship rolls also in the longitudinal direction with a natural frequency f 2 . This movement causes accelerations which are repeated at the frequency f 2 .
  • a change in the speed of the ship 5 results in an ac ⁇ celeration/deceleration a y parallel to the course of the ship.
  • the schematic diagram of the control system is shown in Fig. 3.
  • the position of the body to be stabilized (in this case, of the integrated body 1, 2, 7, 3 in connection of the ship 5) is measured in relation to two horizontal axes deviating from each other.
  • the measuring is performed with two inclinometers 8, 9 which measure the momentary total acceleration in relation to their measuring axis.
  • the inclinometer used as the sensors, gives measuring signals x 1 and y, .
  • the gyroscopic compass 10 of the ship gives the heading line h of the vessel.
  • the cruising speed of the ship is obtained from the log sensor of the ship or from a positioning device 11 (e.g. GPS) .
  • the measuring signal in the direction of the crosswise axis of the ship 5 is , (inclinometer 8) . If the antenna is not on the longitudinal axis of the ship 5, the signal is corrected with regard to deviations caused by accelerations due to changes in the heading line of the ship by adding (means 14) to the signal the square 12 of the angular velocity w derived from the heading line h, multiplied by the component r x (means 13) in the crosswise direction of the dis- tance r., (Fig. 2) .
  • the new signal x 2 is corrected with regard to lateral accelerations caused by changes in the course of the ship by adding (means 15) thereto the angular velocity w of the ship's heading line multiplied by the ship's velocity v.
  • the signal x 3 thus obtained is passed through a low pass filter (means 17) with a long time constant adjusted (by means 18) to be a multiple of the cycle length of the frequency f., of the pitching movement of the vessel in the crosswise direction, whereby the effect of this pitching on the measuring result is minimized.
  • the cycle length is obtained e.g. from the signal of the acceleration sensor (means 18) measuring the accelera- tion in the crosswise direction, or it is fixed as a constant on the basis of the properties of the ship.
  • the low-pass filtered signal x 4 is fed to a regula ⁇ tor 19 controlling at least one actuator 20 functioning in direction X (Figs. 4-6) .
  • the measuring signal parallel to the heading line of the ship is y, (inclinometer 9) . If the antenna is not on the crosswise axis of the ship, the deviations caused by the accelerations due to changes in the heading line of the ship are corrected in the signal y 1 by adding (by means 21) thereto the component r y (means 22) of the distance r, (Fig. 2) in the longi ⁇ tudinal direction of the ship, multiplied by the square of the angular velocity w derived from the heading line h.
  • the corrected signal y 2 is corrected
  • the signal y 3 obtained hereby is passed through a low pass filter (means 25) with a long time constant adjusted to be a multiple of the cycle length of the frequency f 2 of the pitching of the ship in the longitudinal direction, whereby the effect of this pitching on the measuring result is minimized.
  • the cycle length is obtained e.g. from the measuring signal of the acceleration sensor (means 26) measuring the acceleration in the longitudinal direc ⁇ tion, or it is fixed as a constant on the basis of the properties of the ship.
  • the low-pass filtered signal y 4 is fed to a regulator 27 controlling at least one actuator 28 functioning in direction Y (Figs. 4-6).
  • actuators 20, 28, e.g. four mechanical fans 20a, 20b; 28a, 28b are used (two in each direction X and Y) which are mounted in connection with the counter ⁇ weight 3, at its lower part, as shown in Fig. 4.
  • the control system explained in connection with Fig. 3, controls the fans 20a, 20b; 28a, 28b in a way that the correction movement is started by directing the fans for a certain time. Upon approaching the desired position, the fans are directed to the opposite direction for a certain time, until the correcting movement is stopped.
  • the ratio of these accelerating and decelerating times is controlled according to the D term of the PD regulator, i.e.
  • the movement of the body is being stopped and- further by the P term of the PD regulator, the time between the acceleration and the deceleration phases is adjusted (these actions being obvious concepts for a man skilled in the art, not described in this context) .
  • the low-pass filtering of the measuring signal is taken into account by setting a decay time. Consequent ⁇ ly, the fans are used to achieve forces effective on the body 1, 2, 1 , 3 on reaction and/or collision principles.
  • the control system used can consist of analog means, using digital signal processing by a microprocessor, or a combination of these.
  • the choice of components is part of the know-how of a man skilled in the art, and it is thus not described in more detail in this context.
  • the directions X and Y are arranged at right angles to each other. It is clear that also other angles are feasible between the directions, and this is even a necessity if there are more than two directions.
  • the fans are placed in a
  • Figure 5 illustrates an embodiment of the invention using a principle analogous to that shown in Fig. 4.
  • actuators 6 are used as actuators 6 in directions X a and Y (in pairs opposite each other acting in both
  • 32b; 33a, 33b is composed (e.g. pair 32a, direction X in Fig. 5) of a permanent magnet 34 (first means) and an electromagnet 35 (second means) which is arranged in connection therewith for achieving a contact-free force.
  • a permanent magnet 34 first means
  • an electromagnet 35 second means
  • Figure 6 illustrates a perspective view of an embodi ⁇ ment of the invention based on utilizing kinetic energy. It consists of two pairs (in analogy to Figs. 4 and 5) of balancing wheels 36a, 36b; 37a, 37b used as actuators 6, whose relative position and/or kinetic energy (speed of rotation) is changed to achieve a desired change in the position of the body.
  • the radome 8 is connected with a sublevel 5b being part of the elevated support frame 5a.
  • the counterweight 3 is thus in free contact with fresh air between the ship's 5 deck and the sublevel 5b.
  • the embodiment shown in Fig. 4 can be modified in a way that e.g. water can be used as the fluidized medium, which is then removed along the deck of the ship 5.
  • the method and the arrange ⁇ ment are based firstly on a statioinary supported mass center of the body, secondly on continuous measurements of the kinetic state of the body, and thirdly on controlling the adjusting of the position of the body, especially by means of a slow control system.

Landscapes

  • Variable-Direction Aerials And Aerial Arrays (AREA)
  • Control Of Position, Course, Altitude, Or Attitude Of Moving Bodies (AREA)

Abstract

Procédé et système de stabilisation de corps mécaniques. Selon le procédé, le corps à stabiliser (1, 2, 7, 3) est porté au niveau de son centre de masse (4) afin qu'aucune accélération dans quelque sens que ce soit ne crée un couple de rotation dû aux forces d'inertie dans le corps. De ce fait, le corps garde sa position par rapport au champ de gravitation de la Terre, même lorsque les accélérations et les divers états cinétiques agissent au niveau du point d'appui (4). L'écartement lent et progressif du corps de la position voulue est compensé par un système de commande lente employant des actuateurs (6) fonctionnant sans contact. Selon un mode tout particulièrement avantageux de réalisation, on peut assurer la stabilisation des corps fixés à des objets en mouvement.
PCT/FI1992/000245 1991-10-21 1992-09-21 Procede et systeme de stabilisation mecanique WO1993008614A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI914944A FI91198C (fi) 1991-10-21 1991-10-21 Menetelmä mekaaniseen stabilointiin
FI914944 1991-10-21

Publications (1)

Publication Number Publication Date
WO1993008614A1 true WO1993008614A1 (fr) 1993-04-29

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ID=8533326

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/FI1992/000245 WO1993008614A1 (fr) 1991-10-21 1992-09-21 Procede et systeme de stabilisation mecanique

Country Status (3)

Country Link
AU (1) AU2580592A (fr)
FI (1) FI91198C (fr)
WO (1) WO1993008614A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10897072B2 (en) * 2018-09-28 2021-01-19 Robert N. Iannuzzi Balance platform for mobile antenna

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3747418A (en) * 1971-06-08 1973-07-24 Singer Co Fluidic inertial platform
US4020491A (en) * 1974-10-07 1977-04-26 B E Industries Combination gyro and pendulum weight passive antenna platform stabilization system
US4596989A (en) * 1983-02-14 1986-06-24 Tracor Bei, Inc. Stabilized antenna system having an acceleration displaceable mass

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3747418A (en) * 1971-06-08 1973-07-24 Singer Co Fluidic inertial platform
US4020491A (en) * 1974-10-07 1977-04-26 B E Industries Combination gyro and pendulum weight passive antenna platform stabilization system
US4596989A (en) * 1983-02-14 1986-06-24 Tracor Bei, Inc. Stabilized antenna system having an acceleration displaceable mass

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10897072B2 (en) * 2018-09-28 2021-01-19 Robert N. Iannuzzi Balance platform for mobile antenna

Also Published As

Publication number Publication date
AU2580592A (en) 1993-05-21
FI91198B (fi) 1994-02-15
FI914944A (fi) 1993-04-22
FI914944A0 (fi) 1991-10-21
FI91198C (fi) 1994-05-25

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