Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C21/00—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00
  • G01C21/10—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration
  • G01C21/12—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning
  • G01C21/16—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation
  • G01C21/165—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments
  • G01C21/1654—Navigation; Navigational instruments not provided for in groups G01C1/00 - G01C19/00 by using measurements of speed or acceleration executed aboard the object being navigated; Dead reckoning by integrating acceleration or speed, i.e. inertial navigation combined with non-inertial navigation instruments with electromagnetic compass
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C17/00—Compasses; Devices for ascertaining true or magnetic north for navigation or surveying purposes
  • G01C17/38—Testing, calibrating, or compensating of compasses
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
  • G01C25/00—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass
  • G01C25/005—Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass initial alignment, calibration or starting-up of inertial devices

Definitions

• the invention relates to a system and a method for determining parameters representative of the orientation of a moving solid subjected to two vector fields.
• motion capture systems of a solid have applications in various fields such as health, multimedia, or geophysics.
• a user's movements can be used to control virtual reality systems.
• the movements of a player can be recorded to control the evolution of a virtual character in a synthesis scene.
• motion capture devices allow devices to adapt to the context of use. They allow, for example, to optimize the reception of a mobile phone by the knowledge of its orientation, or to improve the interfaces of the personal assistants.
• such systems can be used to position surgical tools, or to monitor the movement of elderly people or those with health problems resulting in reduced mobility.
• Motion sensors and more precisely angular position sensors, are highly miniaturized and researched to give them robustness and cost compatible with applications aimed at the general public.
• the position of a solid in space is entirely determined by the knowledge of six magnitudes. Among these are three sizes that can translate translations and three other sizes likely to translate rotations. The last three magnitudes correspond to angular positions, called attitude angles, that can be used to determine motions.
• a rotation can be defined by a quaternion.
• FR 2 838 185 Commissariat à l'Energie
• Atomic discloses a device for capturing the orientation of a solid comprising at least one angular position sensor that can be made integral with the solid and to deliver at least one measurement data representative of the orientation of the solid, a means for generator of test data representative of an estimated orientation of the solid, and means for modifying the estimated orientation of the solid by confronting the measurement data and test data. After one or more modifications of the estimated orientation, it converges towards the effective orientation of the solid, or, more precisely, towards the measured orientation.
• This device does not require calculation means to establish the orientation or the inclination of the solid on the basis of a function of the measurement data of the sensors, and makes it possible to overcome the non-linear behaviors of these.
• Such a device requires many calculations and can not, or hardly, be embedded on a system of reduced size. Such a device is also sensitive to the proper acceleration of the solid.
• the present invention aims to solve the problems mentioned above.
• Said system comprises a first triaxial sensor and a second triaxial sensor integral with said solid to measure the components of said respective vector fields along the axes of said sensors, and means for determining the rotation matrix of the solid.
• Said means for determining said rotation matrix comprise: correction means, deactivatable on command, adapted to correct the influence exerted on the measurements of at least one of said sensors by an additional vector field of the same nature as said measured vector field and to deliver at least one vector corrected vector field ; and
• first means for calculating a third vector adapted to calculate said third non-coplanar vector to the plane formed by the two vectors delivered by said correction means, and such that the angles of the trihedron formed by the third vector and the two vectors delivered by said correction means remain constant.
• said means for determining said rotation matrix further include means for orthogonalizing and centering the measurements transmitted by said triaxial sensors.
• said means for determining said rotation matrix further comprise control means adapted to deactivate said correction means at a time taken for reference, while said first calculation means calculate a third vector of reference.
• the user can thus choose his reference.
• system further comprises automatic activation means adapted to activate said correction means when a standard of one of said vector fields transmitted by said triaxial sensors is greater than a reference threshold and for deactivating said correction means when said standard is less than or equal to said reference threshold.
• said means for determining said rotation matrix further comprise second means for calculating an intermediate matrix whose successive columns are the components of said third vector, the components of said first vector field measured and possibly corrected by said correction means, and the components of said second vector field measured and possibly corrected by said correction means.
• said means for determining said rotation matrix further comprise third matrix inversion calculating means adapted to be activated by said control means when calculating the third reference vector and for calculating the inverse matrix of said intermediate matrix corresponding to the third reference vector and named reference inverse matrix.
• said means for determining said rotation matrix further comprise storage means for storing said reference inverse matrix.
• said means for determining said rotation matrix further comprise a multiplier for multiplying said intermediate matrix and said stored reference inverse matrix and outputting said rotation matrix.
• the matrix of rotation of the solid is obtained directly in a simple manner.
• the system further comprises means for determining said parameters representative of the orientation of the solid from the coefficients of said rotation matrix.
• attitude angles of the solid or the quaternion representative of the orientation of the solid from the rotation matrix of the solid are then immediately deduced.
• said third vector is the vector product of the first measured and possibly corrected vector field and the second vector field measured and possibly corrected.
• the vector product is a third vector that fulfills the above conditions and is simple to compute.
• said first vector field is the terrestrial gravitational field and said second field is the terrestrial magnetic field.
• the invention applies in a non-limiting manner to gravitational and magnetic terrestrial fields.
• said correction means are adapted to correct the measured gravitational field in a corrected gravitational field by adding to the measured gravitational vector a vector proportional to the measured terrestrial magnetic vector so that the corrected gravitational vector forms with the terrestrial magnetic vector measured at an angle equal to a reference angle equal to the substantially constant angle between the terrestrial gravitational field and the terrestrial magnetic field in said fixed frame not bound to solid, and adapted to center the corrected gravitational vector.
• said parameters representative of the orientation of the solid comprise attitude angles such as Cardan angles or Euler angles, or a quaternion.
• the influence exerted on the measurements of at least one of said sensors by an additional vector field of the same nature as said measured vector field is corrected and at least one vector corrected vector vector is corrected.
• a third non-coplanar vector is calculated from the plane formed by the two vectors delivered at the correction output, and such that the angles of the trihedron formed by the third vector and the two vectors delivered at the correction output remain substantially constant.
• the measurements of the first and second vector fields are orthogonalized and centered, and said correction is deactivated at an instant taken for reference during the calculation of a third reference vector.
• FIG. 1 schematically illustrates an embodiment of a system according to an aspect of FIG. the invention.
• FIG. 2 diagrammatically illustrates a mode of implementation of the method according to one aspect of the invention.
• attitude angles of a solid In the description which follows, reference is made to the attitude angles of a solid. However, the solid is not part of the attitude angle determination system, which corresponds more precisely to those sensors that can be attached to the solid.
• orientation and angular position are used as synonyms.
• the two vector fields are the terrestrial gravitational field and the terrestrial magnetic field.
• the invention also applies to any two arbitrary vector fields that are substantially constant in a non-solid fixed reference frame.
• the system comprises a triaxial accelerometer CAPT1 which measures, in a reference frame linked to the solid, the gravitational field A and a triaxial magnetometer CAPT2 which measures in the reference frame the magnetic field M.
• the measurements transmitted by the triaxial accelerometer CAPT1 and the triaxial magnetometer CAPT2 are transmitted to a DETROT module for determining the rotation matrix ROT are orthogonalized and centered by an ORTHOC module.
• the orthogonalization and the centering of the measurements transmitted by the triaxial sensors CAPT1 and CAPT2 can be directly carried out within the sensors themselves.
• Orthogonalization means measurements delivered by a triaxial sensor, a posterior correction of the perpendicularity defects of the sensor, and by centering the measurements delivered by a sensor, a correction of the offset of the sensor so that it has a zero response. for a null stimulus.
• a correction module CORR which can be deactivated on command by a user of the system, via a command module CONTROL, makes it possible to correct the influence exerted on the measurements of at least one of the sensors by an additional vector field of the same nature as that measured.
• an acceleration proper to the solid is measured by the triaxial accelerometer CAPT1 in addition to the reference gravitational field A1.
• the correction module CORR adds to the measurement vector A a vector parallel to the measurement vector M: A + tM, which is called A PP , t being a determined scalar of so that the angle formed by A PP and M is equal to the angle between the gravitational and magnetic terrestrial fields of substantially constant directions in a fixed reference unrelated to the solid.
• an ACTAUTO automatic activation module tests whether a standard of one of said vector fields is greater than a reference threshold, and, if the standard of one of said vector fields is greater than this reference threshold, active automatically the correction module CORR, and to disable it otherwise.
• a first calculation module CALC1 calculates a third vector U which is not coplanar with the plane formed by the two vectors delivered by the correction module CORR, and such that the angles of the trihedron formed by the third vector U and the two vectors A PP and M delivered by the correction module remain constant.
• a second calculation module CALC2 forms an intermediate matrix (UA PP M) whose successive columns are formed by the components of the third vector U, the corrected measurement vector A PP , and the measurement vector M.
• the second calculation module CALC2 elaborates an intermediate matrix (U- I A- I M- I ) corresponding to the third reference vector Ui.
• a third calculation module CALC3 is activated by the command module CONTROL allowing a user to define the reference of the system.
• This inversion reference matrix inv ((U- ⁇ A- ⁇ M- ⁇ )) is calculated once.
• the correction module CORR is activated, and the third calculation module CALC3 is deactivated.
• a multiplication module MULT receives as input the intermediate matrix (UAp P M) and the inverted reference inverse matrix inv ((U- ⁇ A- ⁇ M- ⁇ )), respectively of the second calculation module CALC2 and of the memory module MEM, and outputs the matrix product of these two matrices, equal to the rotational matrix ROT representative of the rotation of the solid.
• a determination module DET determines the parameters representative of the orientation of the solid.
• the parameters representative of the orientation of the solid may be, for example, the attitude angles of the solid, such as yaw, roll and pitch angles.
• the parameters representative of the orientation of the solid may be, for example, a quaternion.
• Similar identifications may be used.
• FIG. 2 illustrates the operation of a system according to FIG.
• the CAPT1 and CAPT2 triaxial sensors perform measurements (step 1)
• step 22 The influence exerted on the measurements of at least one of the sensors by an additional field of the same nature as that measured, in this case an acceleration proper to the solid, is measured by the triaxial accelerometer CAPT1 in addition to the reference gravitational field A1 , is corrected (step 22) by the CORR correction module as previously described.
• This step may be deactivated, or in other words not carried out, on temporary command (step 23) of a user of the system, especially when he wants to define a reference of the system.
• An optional automatic test (step 21 a) comparing whether the norm of one of the orthogonalized and centered vectors A or M, delivered by the ORTHOC orthogonalization and centering module, is greater than a reference threshold, and, if this condition is verified, the ACTAUTO automatic activation module activates the correction module CORR.
• a third vector U is then calculated (step 24) so that it is non-coplanar with the plane formed by the two vectors delivered by the correction module CORR, and such that the angles of the trihedron formed by the third vector U and the two vectors A PP and M delivered by the correction module remain constant.
• U may be the vector product of the vectors A PP and M delivered by the correction module CORR, calculated by the first calculation module CALC1.
• the second calculation module CALC2 then calculates (step 25) an intermediate matrix (UA PP M) whose successive columns are formed by the components of the third vector U, the corrected measurement vector A PP , and the measurement vector M.
• the command module COMMAND also activates the third calculation module CALC3 (step 26) to calculate the inverse reference matrix inv ( (UiA 1 M 1 )) previously defined.
• This inverse reference matrix inv ((UiAiM- ⁇ )) is stored (step 27) in the memory module MEM.
• the multiplication module MULT performs the matrix product or multiplication (step 28) of the intermediate matrix (UA PP M) and the stored reference inverse matrix inv ((U- ⁇ A- ⁇ M- ⁇ )) for outputting the rotation matrix ROT of the rotation of the solid.
• the determination module DET determines (step 29) the attitude angles of the solid or the quaternion from the rotation matrix ROT, for example as previously described for the DET module.
• the present invention thus makes it possible, with a reduced number of computations providing the attitude angles of a moving solid or a quaternion from the rotation matrix, to produce a small portable system allowing the motion capture of a solid.

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• Engineering & Computer Science (AREA)
• Radar, Positioning & Navigation (AREA)
• Remote Sensing (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Automation & Control Theory (AREA)
• Manufacturing & Machinery (AREA)
• Electromagnetism (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)
• Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

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• 2008
  • 2008-04-18 FR FR0802172A patent/FR2930335B1/fr not_active Expired - Fee Related
• 2009
  • 2009-04-08 EP EP09732406A patent/EP2268999A1/de not_active Withdrawn
  • 2009-04-08 US US12/937,797 patent/US9297660B2/en active Active
  • 2009-04-08 WO PCT/EP2009/054185 patent/WO2009127561A1/fr active Application Filing

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