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    • 专利摘要:
    Thrust measurement device for plasma engines comprising a bed (1), a frame (2), a displacement sensor (7), two mechanisms (3a, 3b) of bars (31, 32, 33, 34, 35 , 36), at least four joints (41, 42, 43, 44) of articulation between the frame (2) and the mechanisms (3a, 3b), where each mechanism (3) together with the frame (2) forms an assembly articulated as a four-bar mechanism by Chebyshev and where the device is configured to measure a thrust exerted by the plasma motor (5) from the measurement of the displacement of said plasma motor (5). (Machine-translation by Google Translate, not legally binding)
    公开号:ES2668787A1
    申请号:ES201830135
    申请日:2018-02-15
    公开日:2018-05-22
    发明作者:Cintia BARAJAS FERNANDEZ；Miguel BERZAL RUBIO；Rodrigo HERNANDEZ CIFUENTES
    申请人:Universidad Politecnica de Madrid；
    IPC主号:
    专利说明:

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    DESCRIPTION
    Thrust measurement device for plasma motors
    Object of the invention
    The present invention relates to a scale or thrust measuring device for plasma motors. By means of the device of the invention, the thrusts generated by small plasma motors can be measured inside vacuum chambers of small dimensions.
    The thrust measuring device for plasma motors object of the present invention has application in the field of Metrology, especially within the academic field, for testing prototypes of small-sized plasma motors with electric drive, which are used primarily in the aerospace industry.
    Technical problem to be solved and Background of the invention
    Plasma propellers, and particularly low power plasma propellers, have very small thrusts, of the order of mN. Contrary to chemical rocket engines, which provide a very high thrust (they are useful for reaching escape velocity and leaving the Earth's atmosphere).
    Plasma propellers are suitable for small thrusts in the interplanetary environment (correct satellite orbits due to the uneven gravitational effect of the earth or deposit the satellite in an orbit destined for waste outside its useful life, or disintegrate the satellite by forcing its reentry into Earth's atmosphere).
    While chemical rocket engines are experienced in atmospheric conditions, plasma propellers must be experienced in vacuum chambers, as these are their nominal working conditions: the interplanetary vacuum environment.
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    It is imperative to know the performance of the motor (relationship between the energy consumed and the energy dedicated to moving). The energy that is dedicated to the movement of the motor or propeller is the thrust. And you need to measure directly on the propeller.
    The plasma propellant is characterized by ionizing, through electron collisions, the atoms of the propellant inert gas (usually a noble gas, such as Xenon). Once these atoms have ceased to be neutral, they can be subjected to an electrostatic field and accelerated out of the propellant. When they are out of the propeller, the electron is supplied again, which neutralizes them.
    In this process, an energy exchange has been promoted. Through an electrostatic field, there has been an exchange of amount of movement between the ionized gas and the propellant. This is what causes the thrust (which is the object of characterization / measurement by the device of the present invention).
    It is therefore necessary to create some type of mechanism that moves when the propeller begins to work. This mechanism that moves is called a push scale (or thrust stand, in English).
    The preponderant configurations of thrust scales for plasma propellers are those based on the pendulums.
    There are essentially three types of pendulums to be used in thrust scales: torsional pendulum, inverted pendulum and hanging pendulum.
    The torsion pendulum (TP) requires a counterweight, and therefore, greater friction in the joint. It requires a camera of very large dimensions, since the arms (on each side of the pivot) must be wide enough to locate the counterweight and the plasma motor whose thrust is to be measured.
    The inverted pendulum (IT) requires PID electronic and automatic control systems to prevent complete deflection (or overturning of the pendulum) and loss of control over the single system equilibrium point (unstable equilibrium point: "Repulsor").
    The hanging pendulum (HT), for its part, offers little control over motor movement and allows much smaller displacement for small vacuum chambers.
    5 Some balances or thrust measurement devices for known plasma motors are listed below.
    Those listed below are a selection of the scales considered as most representative of their species.
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    These are reflected in the following table.
     Institution  Type Propeller Range Tolerance
     TASI / INMT / PT  HP Micro <1 mN 0.1 | ^ N
     NIAIST / KIT  HP CGT 0.14 - 1.25 N -
     SSC / EADSA  HP / IP HCT / HDLT 1.2 - 10 / 0.8 - 4.2 mN
     IU / ANU / EADSA / SSC  HP PM-HDLT 0 - 3 mN 0.034 mN
     PU / NASA  TP QSMPDT 20 | ^ N - 10 N 10 | ^ N
     USC / AFRL  TP Micro 88.8 nN - 1 ^ N -
     GSFC  TP CIE 4.4 | ^ N - 222 mN 5%
     UH / UM / AA / NASA  PMFS VASIMR 0 - 1,000 mN 0.1 mN
    The acronyms used in the column headed by "Institution" mean:
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    TASI / INMT / PT: Thales Alenia Space Italia - Italian National Metrology Institute - Polytechnic of Turin.
    NIAIST / KIT: National Institute of Advanced Industrial Science and Technology - 20 Kyusyu Institute of Technology (Department of Mechanical Engineering).
    SSC / EADSA: Surrey Space Center - EADS Astrium.
    IU / ANU / EADSA / SSC: Iwate University - Australian National University (Space 25 Plasma, Power and Propulsion Group, Research School of Physics and Engineering) - EADS Astrium - Surrey Space Center.
    PU / NASA: Princeton University - NASA.
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    USC / AFRL: University of Souther California (Department of Aerospace and Mechanical Engineering) - Air Force Research Laboratory, Propulsion Directorate.
    The acronyms shown in the "Type" column refer to the existence, as already mentioned above, of three main traditional configurations (HP, IP, TP) possible when measuring the forces or thrusts exerted by electric thrusters (James E Polk, Anthony Pancotti, Thomas Haag, Scott King, Mitchell Walker, Joseph Blakely, and John Ziemer. Recommended practices in thrust measurements. Technical report, DTIC Document, 2013.).
    In addition, two additional types have been added to those traditionally studied, which are the fourth (M) and fifth items (PMFS) that follow:
    1. Pendulums:
    - Hanging pendulum (HP)
    - Inverted pendulum (IP)
    - Torsional pendulum (TP)
    2. Mechanism (M)
    3. Plasma flow momentum sensor (PMFS)
    The acronyms shown in the "Propeller" column refer to:
    Micro: Microthruster (see LISA-Pathfinder, Microscope and GAIA programs).
    CGT: Cold Gas Thruster
    HCT: Hollow Cathode Thruster
    HDLT: Helicon Double Layer Thruster
    PM-HDLT: Permanent Magnet Helicon Double Layer Thruster
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    QSMPDT: Quasi-steady Magnetoplasma Dynamic Thruster
    CIE: Cesium Ion Engine
    VASIMR: Variable Specific Impulse Magnetoplasma Rocket
    The constructive aspects of these devices of the prior art are developed below.
    TASI / INMT / PT balance:
    It is a precision nanobalance for electric thrusters created by Thales Alenia Space Italia in cooperation with the National Institute of Metrology of Italy and the Polytechnic of Turin (Stefano Cesare, Fabio Musso, Filippo DAngelo, Giuseppe Castorina, Marco Bisi, Paolo Cordiale, Enrico Canuto , Davide Nicolini, Eliseo Balaguer, and Pierre-Etienne Frigot. Nanobalance: the european balance for micro-propulsion. In 31st International Electric Propulsion Conference, pages 1-20, 2009.). Some features of this precision tool are:
    - Propeller support: consists of two deflector plates, made of copper and beryllium alloy, each connected through an elastic joint to a rigid spacer made of Zerodur®. On the rigid spacer is the inclinometer.
    - Inner diameter of the vacuum chamber: 1.2 m. Rest on four pneumatic insulators
    - Metrological and measurement system: It is a Fabry-Perot laser interferometer and an optomechanical configuration.
    This is an example of a highly sensitive precision balance made with specialized processing materials, sophisticated control systems and signal noise filtration.
    NIAIST Balance / KIT:
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    An example of an ordinary hanging pendulum is Kakami's Thrust Stand (Akira Kakami, R Hiyamizu, S Masaki, and T Tachibana. A preliminary study on an active- controlled thrust stand for thrust variation measurement. In PROCEEDINGS OF THE INTERNATIONAL SYMPOSIUM ON SPACE TECHNOLOGY AND SCIENCE, volume 25, page 212, 2006.).
    Although it is not a scale created specifically for a plasma propeller (but for a cold gas propeller), it has been determined to include it in this background section.
    The big difference between this model and the rest of the instruments mentioned in the previous table is the magnitude of the nominal thrusts it measures. The Kakami apparatus is capable of satisfactorily measuring 1.25 N forces. Some features of this balance are:
    - Electromagnetic cylindrical actuator, designed for active thrust control (which varies over time).
    - PID and RTAI control system (real application interface); the last one created by the Polytechnic of Milan.
    - Mechanical joints: frictionless joints such as flexor pivots. SSC / EADSA balance:
    Another publication that should be noted is the following, by Pottinger, Lamprou, Knoll and Lappas (SJ Pottinger, D Lamprou, AK Knoll, and VJ Lappas. Impact of plasma noise on a direct thrust measurement system. Review of Scientific Instruments, 83 ( 3): 033504, 2012.). These authors add another tool to compare each measurement they obtain through an opto-mechanical sensor. What they use is an LVDT (linear variable differential transformer).
    This publication focuses on how plasma noise can create disturbances in this type of electromagnetic sensors.
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    Comparing the measurements made by an LVDT and a laser, when the inert gas is introduced into the system, there is no significant difference in the two readings, but once the gas is ionized and a plasma flow is generated, there is no comparison. with the results obtained by these two sensors.
    The plasma flow creates a lot of noise in the signal given by the LVDT. If an LVDT is required, it is completely mandatory to filter the signal. Anyway, it is not the best sensor to work with. Although it can be useful for the characterization of the inert gas still not ionized, or perhaps for the calibration process.
    The inside diameter of the vacuum chamber is 1.2 m.
    Balance IU / ANU / EADSA / SSC:
    The following double pendulum configuration can be found in an experiment led by the Australian National University and the University of Iwate, in cooperation with Astrium-EADS and the Surrey Space Center. Some of its prerequisites were:
    - Vacuum chamber: the Irukandji chamber simulates the conditions of the interplanetary space and has a diameter of 1m.
    - Laser sensor: high sensitivity, with a Micro-Epsilon radio frequency shield, laser displacement sensor.
    - Simple calibration process. Equivalence: 340 mN / mm. Resolution: 0.034 mN.
    PU / NASA balance:
    The Princeton University Electric and Dynamic Plasma Propulsion Laboratory has designed and studied the behavior of a torsional pendulum (EA Cubbin, JK Ziemer, EY Choueiri, and RG Jahn. Pulsed thrust measurements using laser interferometry. Review of Scientific Instruments, 68 (6): 2339-2346, 1997.). The internal diameter of the chamber is 2 m. The publication also gives us information about the frictionless joints that these researchers used: 6016 Bendix free-flex pivots.
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    With respect to the calibration system, the multiple similarities of PIPTS11 (Princeton Inverted Pendulum Thrust Stand) with the prototype made by the Australian National University and the University of Iwate stand out.
    They use a mechanical calibration system based on a pair of weight and pulley, optimal from the point of view of simplicity, and efficient with a view to obtaining a calibration curve. In this same text, the adverse effects of thermal management and its evacuation to avoid damage to the joints stand out. They also mention how the temperature rise causes a change in the sensitivity of the measuring device.
    USC / AFRL balance:
    The pulley weight calibration system is not always effective. The Department of Aerospace and Mechanical Engineering at the University of Southern California (USC) faced several challenges in the development and calibration of its nanobalance. The friction of the pulley had a very significant role in this aspect, becoming something not negligible. Its main features are:
    - Torsional pendulum balance.
    - Sensor: LVDT.
    - Internal diameter of the vacuum chamber: 3 m.
    - For thrust measurements greater than 1 pN, the thrust balance arms are 25 cm long from the center of rotation.
    - Flexor pivot located at the midpoint of the ends of the arms.
    - For thrust measurements below 1 pN, ”the calibration uses hole thrust measurements with thin walls, under-expanded, in free molecule flow regime, corrected with the DSMC (Direct Simulation Monte Carlo) simulation analytical results”.
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    Measuring range: 88.8 nN to 1 pN nN.
    GSFC Balance:
    Regarding how prototypes evolve over time, in 1970, Stark and McHugh, in Goddard Space Flight Center (NASA) made a relevant publication (T Dennis, GODDARD SPACEFLIGHT Center, MD Greenbelt, et al. Design and development of a micropound extended range thrust stand / merts In 8th Electric Propulsion Conference, page 1111, 1970.), where very suitable suggestions are found for a correct practice of thrust measurement in various thrusters. The following strength points were based on their previous unsatisfactory experiences. His designs evolved to the final prototype, with the following characteristics:
    - Measuring range: from 4.4 pN to 222 mN.
    - Propeller weights supported, up to 133 N.
    - System without friction based on flexor pivots.
    - Power supply for the propeller through the flexor pivot.
    - Calibration in situ.
    UH / UM / AA / NASA plasma flow moment sensor:
    Although this method of thrust analysis moves away from the technical field of the present invention, the following two publications are worth mentioning due to its incipient interest for auxiliary or comparative systems between the thrust made by the propellant and the amount of plasma flow movement:
    Benjamin W Longmier, Edgar A Bering, JP Squire, TW Glover, FR Chang-Díaz, and M Brukardt. Hall thruster and vasimr vx-100 force measurements using a plasma momentum flux sensor. In 47th AIAA aerospace sciences meeting including the new horizons forum and aerospace exposition, AIAA-246, Orlando, 2009;
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    Y,
    Benjamin W Longmier, Bryan M Reid, Alec D Gallimore, Franklin R Chang-Diaz, Jared P Squire, Tim W Glover, Greg Chavers, and Edgar A Bering. Validating a plasma momentum flux sensor to an inverted pendulum thrust stand. Journal of Propulsion and Power, 25 (3): 746-752, 2009.
    The positive point of this type of sensors is its cost efficiency and the simplicity associated with its construction. It serves perfectly for propellers that are very heavy. They show a relative error, with respect to inverted pendulums of an average of 2% for a wide range of forces.
    In view of the different systems of the prior art, the following technical problems have been observed:
    - Many of these systems require complex electronic equipment (such as LVDT) to provide an adequate level of sensitivity and accuracy to the extent that, apart from having a relatively high cost, they are vulnerable to interference caused by ionized plasma;
    - The prior art systems need to be implemented in large vacuum chambers, generally of dimensions around one meter in diameter, or greater.
    Description of the invention
    In order to provide a solution to the aforementioned problems, the following thrust measurement device for plasma motors is presented.
    The thrust measuring device for plasma motors object of the present invention incorporates: a bench, a frame, a displacement sensor, at least two mechanisms, and at least four articulation joints between the frame and the mechanisms.
    Each mechanism includes:
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    - a first bar configured to be connected with a crazy rotation by means of a pivotal connection to a plasma motor, where the pivot connection is located in correspondence with an intermediate point of the first bar;
    - a second bar, connected with a crazy turn to a first end of the first bar, and also connected with a crazy turn to a first joint joint with the frame;
    - a third bar, connected with a crazy turn to a second end of the first bar, and also connected with a crazy turn to a second joint joint with the frame.
    The device is configured to measure a thrust exerted by the plasma engine from the measurement of the displacement of said plasma engine.
    Preferably, the thrust measurement device for plasma motors incorporates a support configured to accommodate and hold the plasma motor and configured to intermediate between the respective first bars of the mechanisms and the plasma motor. In this way, each first bar is configured to join with a crazy rotation by means of its respective pivoting connection to the plasma motor support.
    Preferably, the displacement sensor is an optomechanical sensor. More preferably, said optomechanical displacement sensor is a laser sensor and, even more preferably, said optomechanical laser displacement sensor is a triangulation sensor.
    According to a possible embodiment of the device, the frame is articulated with respect to the bench. This makes it possible to add degrees of freedom to the movement of the plasma engine during the tests.
    Alternatively, the frame can be fixedly connected with respect to the bench.
    Preferably, at least one of the articulated joints comprises a torsion spring or flexor pivot. By means of this torsion spring, at least the second bar or third bar of at least one of the mechanisms has a limitation in the rotation that it is capable of carrying out with respect to the frame. This limits the movement of the
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    device (that is, it limits the total displacement that the plasma motor can present once mounted on the device of the invention) and minimizes the friction of the initial static position.
    Brief description of the figures
    As part of the explanation of at least one preferred embodiment of the thrust measurement device for plasma motors, the following figure has been included, where the following is illustrated and not limited to.
    Figure 1: Shows a simplified schematic representation of three types of plasma motor thrust measurement balances in the state of the art, each of the three types of scales based respectively on a torsion pendulum (TP), an inverted pendulum (IP) and a hanging pendulum (HP).
    Figure 2: Shows a simplified schematic representation of a first embodiment of the thrust measuring device for plasma motors object of the present invention.
    Figure 3: Shows a simplified diagram of the operation of the device of the invention, according to the first embodiment of the device.
    Figure 4: shows a schematic representation of the headers experienced by the plasma engine when a device with a single mechanism is used, the thrust being applied on a line that does not pass through the center of mass of the plasma engine.
    Detailed description
    The present invention relates, as already mentioned above, to a thrust measuring device for plasma motors (5).
    Figure 1, as already mentioned, shows a simplified schematic representation of three types of thrust measurement scale, E, of plasma motors, existing in the state of the art, each of said scales based
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    respectively in a torsion pendulum (TP), an inverted pendulum (IP) and a hanging pendulum (HP). A weight mass, P, is incorporated into said pendulum, and a counterweight is applied, C. For the thrust measurement, E, a displacement, 5, of the mass is typically measured.
    The thrust measuring device for plasma motors (5) object of the present invention comprises a bed (1), a frame (2), at least two bar mechanisms (3a, 3b) (31, 32, 33, 34 , 35, 36), at least four joints (41, 42, 43, 44) articulated (or kinematic pairs) between the frame (2) and the mechanisms (3a, 3b), where the mechanisms (3a, 3b) are configured to join a plasma motor (5) by at least one pivoting joint (61, 62).
    Preferably, at least one articulated joint (41) is a flexor / torsion spring pivot. The rest of articulated joints (42, 43, 44) can be made, for example, as a lubrication bearing (in this case it would be dry lubrication bearings, since they have to work in vacuum conditions inside the chamber of empty).
    According to a possible embodiment, the frame (2) is articulated with respect to the bed (1), so as to allow more degrees of freedom in the movement of the plasma motor (5) when the thrust is applied.
    According to another possible embodiment, the frame (2) is anchored to the bed (1), so that the frame (2) does not provide degrees of freedom to the movement of the plasma motor (5).
    The device comprises a displacement sensor (7), preferably optomechanical, and more preferably a displacement sensor (7) configured to emit a laser beam focused on the plasma motor (5) and detect displacements by triangulation.
    According to a first embodiment of the device, a first mechanism (3a) is constituted by three bars (31, 32, 33) which, together with the frame (2) that joins the at least four joints (41, 42, 43, 44) articulated, constitutes a mechanism of four Chebyshev bars.
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    According to this first embodiment of the device, a second mechanism (3b) is constituted by three bars (34, 35, 36) which, together with the frame (2) that joins the at least four joints (41, 42, 43, 44) articulated, constitutes a mechanism of four Chebyshev bars.
    According to this first embodiment, each mechanism (3a, 3b) consists of a first bar (31, 34) connected with a crazy rotation by means of a pivotal joint (61, 62) to the plasma motor (5). The pivot joint (61, 62) is located in correspondence with an intermediate point of the first bar (31, 34), preferably in correspondence with its midpoint. Each mechanism (3a, 3b) comprises a second bar (32, 35), connected with a crazy turn to a first end of the first bar (31, 34), and also connected with a crazy turn to a first joint (41, 43) articulated Each mechanism (3a, 3b) also incorporates a third bar (33, 36), connected with a crazy turn to a second end of the first bar (31, 34), and also connected with a crazy turn to a second joint (42, 44 ) articulated.
    Figure 2 shows a simplified schematic representation of a thrust measurement device for a plasma motor (5), according to the first embodiment.
    According to other embodiments (not shown in the figures), the device incorporates more than two mechanisms, each of them connected by their respective pivotal connection with the plasma motor.
    Preferably, the device comprises a support (8) configured to accommodate and hold the plasma motor (5), such that the support (8) mediates between each mechanism (3a, 3b) and the motor (5) of plasma.
    Compared to the configurations of existing balances in the state of the art, based primarily on the three types of pendulum (torsion, inverted, hanging), the main novelty of the present invention is the use of the mechanisms (3) described, each of them considered as a mechanism of four bars of approximately straight line of Chebyshev.
    The Chebyshev mechanism presents the possibility of an approximate rectilinear path at the center point of the coupling bars. It is known as straight line
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    approximate because the trajectory presents a slight displacement perpendicular to the degree of freedom. The effect is so insignificant (at least in the present invention) that the vertical displacement error is neglected, and can be considered as a real straight line and not approximate.
    The bars (31, 32, 33, 34, 35, 36) of the mechanisms (3a, 3b) rotate so that the linear displacement of the motor (5) is given in a straight line (see the dashed straight line in Figure 2) , taking into account that all the displacement made is due to a coaxial thrust to the motor (5) (1 degree of freedom). If there were vertical components of the thrust, they would not be taken into account (or considered negligible for 1 degree of freedom).
    Figure 3 shows a plasma motor (5) mounted on a thrust measurement device, according to the first embodiment of the invention. An arrow is observed indicating the direction of the thrust exerted by the plasma motor (5), as well as the initial (top) positions before applying the thrust (t = 0), and final (bottom) after applying the thrust ( t = At). In the center of Figure 3 the displacement, 5x, unidirectional experienced by the plasma motor (5) when applying the thrust is observed, and in broken lines the configuration of the bars (31, 32, 33, 34, 35) is observed , 36) of each mechanism (3a, 3b) in each of the initial and final positions.
    By means of a balanced configuration of two mechanisms (3a, 3b) as the one corresponding to the first embodiment of the device, possible headings of the plasma motor (5) are avoided during the application of the thrust.
    Figure 4 shows a small scheme of the headers that the plasma motor (5) would experience if a device with a single mechanism (3) was used, the thrust being applied on a line that does not pass through the center of mass of the motor ( 5) plasma.
    By means of the first embodiment of the device, a mechanical balancing of the plasma motor (5) is achieved by duplicating the mechanism (3) of the device.
    The modular nature of the device activates the possibility of adding more degrees of freedom to the device, allowing the movement of the frame (2) or introducing more
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    racks, it is possible that the device of the invention can measure displacements not necessarily unidirectional.
    The laser displacement sensor (7) by triangulation provides measurement sensitivities of 1 pm or less.
    The thrust measuring device for plasma motors (5) object of the present invention is preferably configured to measure thrusts of the order of 1 mN, with a sensitivity of 0.1 mN.
    The point on which the displacement measurement is made is arbitrary, although it is preferable that the displacement sensor (7) is not located at the rear of the plasma motor (5), since the plasma jet generated by the Engine (5) can be highly damaging to the displacement sensor (7).
    The location of the displacement sensor (7) or any other secondary sensor will preferably be far from the plasma flow of the motor (5) due to its high temperature and its character of ionized gas, which is the source of undesirable electromagnetic interactions with electronic devices, such as an LVDT (in case you decided to use an LVDT in combination with the device of the invention).
    The thrust measuring device for plasma motors (5) object of the present invention is configured to operate inside a vacuum chamber (not shown), which simulates the actual vacuum conditions in which the motors operate ( 5) Plasma from artificial satellites.
    The device can be carried out in small dimensions (depending on the size of the plasma engine to be tested), being able to operate in vacuum chambers of different sizes, preferably vacuum chambers of 500 mm diameter or less.
    In order to size the device, the size of the plasma motor (5) and the initial resting position to stabilize the plasma motor (5) will preferably be taken into account.
    The ability of the device to be used in vacuum chambers of reduced dimensions makes it possible for the device of the invention to be very useful for academic institutions, which sometimes have a limited budget, and cannot afford high acquisition and handling costs. a large 5-chamber vacuum chamber.
    Likewise, the bars (31, 32, 33, 34, 35, 36) of the mechanisms (3a, 3b) of the device are preferably manufactured by laser cutting, the bars (31, 32, 33, 34, 35, 36 ) preferably aluminum sheets. This fact ensures an easily marketable character of the device, since it is estimated that the total cost of the device of the invention is approximately one tenth that other thrust measurement scales of the prior art.
    The use of a displacement sensor (7) of the optomechanical type (preferably 15 laser) to measure displacements of the plasma motor (5) provides (as opposed to other measurement systems such as the LVDT mentioned in the background section) the differential advantage of that it is possible to be able to carry out measurements in the absence of noise created by the interference that the ionized gas (plasma) in motion (with the consequent induced electromagnetic field) creates on a sensor like the LVDT 20 that is based on the variation of electromagnetic fields with the displacement of a core that induces a variable magnetic field (by an alternating current that circulates in a primary coil). Likewise, any type of sensor or electronic motor (which eventually decided to be used) would be affected by the presence of a moving ionized gas, which generates uncontrolled electromagnetic fields, in short, noise in the measurable signal.
    权利要求:
    Claims (7)
    [1]
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    1. Thrust measuring device for plasma motors characterized in that it comprises: a bench (1), a frame (2), a displacement sensor (7), at least two mechanisms (3a, 3b), at least four joints (41, 42, 43, 44) of articulation between the frame (2) and the mechanisms (3a, 3b), where each mechanism (3a, 3b) comprises:
    - a first bar (31, 34) configured to be connected with a crazy rotation by means of a pivotal joint (61, 62) to a plasma motor (5), where the pivot joint (61, 62) is located in correspondence with an intermediate point from the first bar (31, 34);
    - a second bar (32, 35), connected with a crazy turn to a first end of the first bar (31, 34), and also connected with a crazy turn to a first joint (41, 43) for articulation with the frame (2 );
    - a third bar (33, 36), connected with a crazy turn to a second end of the first bar (31, 34), and also connected with a crazy turn to a second joint (42, 44) of articulation with the frame (2 );
    wherein the device is configured to measure a thrust exerted by the plasma motor (5) from the measurement of the displacement of said plasma motor (5).
    [2]
    2. Thrust measuring device for plasma motors according to claim 1, characterized in that it comprises a support (8) configured to accommodate and hold the plasma motor (5) and configured to intermediate between the respective first bars (31 , 34) of the mechanisms (3a, 3b) and the plasma motor (5), so that each first bar (31, 34) is configured to be connected with a crazy rotation by means of its respective pivoting connection (61, 62) to the support (8) engine (5) plasma.
    [3]
    3. Thrust measurement device for plasma motors according to any of the preceding claims, characterized in that the displacement sensor (7) is an optomechanical sensor.
    [4]
    4. Thrust measuring device for plasma motors according to claim 3, characterized in that the optomechanical displacement sensor (7) is a laser sensor.
    5 5. Thrust measuring device for plasma motors according to the
    claim 4, characterized in that the laser optomechanical displacement sensor (7) is a triangulation sensor.
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    [6]
    6. Thrust measuring device for plasma motors according to any of the preceding claims, characterized in that the frame (2) is articulated with respect to the bed (1).
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    [7]
    7. Thrust measuring device for plasma motors according to any one of claims 1 to 5, characterized in that the frame (2) is fixedly connected with respect to the bed (1).
    [8]
    8. Thrust measuring device for plasma motors according to any of the preceding claims, characterized in that at least one of the articulated joints (41, 42, 43, 44) comprises a torsion spring.
    twenty
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN101745915A|2008-12-19|2010-06-23|中国科学院沈阳自动化研究所|Rectilinear translation planar nine-bar mechanism and method for constructing a rectilinear translation motion mechanism|
    CN102537250A|2011-12-29|2012-07-04|浙江万向系统有限公司|2-RRR mechanism with function of linear movement|
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