Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
  • A61B5/1116—Determining posture transitions
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
  • A61B5/1121—Determining geometric values, e.g. centre of rotation or angular range of movement
  • A61B5/1122—Determining geometric values, e.g. centre of rotation or angular range of movement of movement trajectories
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/11—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb
  • A61B5/1126—Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb using a particular sensing technique
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
  • G01P15/00—Measuring acceleration; Measuring deceleration; Measuring shock, i.e. sudden change of acceleration
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06F—ELECTRIC DIGITAL DATA PROCESSING
  • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
  • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
  • G06F3/011—Arrangements for interaction with the human body, e.g. for user immersion in virtual reality
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0219—Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
  • F04C2270/00—Control; Monitoring or safety arrangements
  • F04C2270/04—Force
  • F04C2270/041—Controlled or regulated

Definitions

• the present invention relates to a method for identifying the geometric parameters of an articulated structure and a set of reference marks arranged on said structure, using a suitable measurement system.
• the evaluated information is as follows:
• the biomechanical parameters of the articulated structure eg lengths of segments.
• the invention is applicable, for example, without this list being limited to the following functions:
• Benchmarks of interest are usually points where one is interested in kinetic parameters.
• the present invention proposes to treat both these problems together without resorting to the methods of the prior art which consist mainly of directly measuring the lengths of the segments of the articulated structure (for example, using a tape measure or the using a complex optical system, ...), to take into account a morphological model making it possible to simulate the dynamics of said structure articulated and to locate the markers of interest on the segments also by direct measurement of their position and their orientation.
• the method comprises associating a distributed measurement system on said structure, system comprising sensors fixed integrally to the segment of said structure instead of the points of the landmarks of interest to extract the desired information described above.
• the articulated structure is biomechanical and one wishes to evaluate the length of its segments
• a motion measurement system is disposed on the articulated structure and it is desired to identify their position and orientation, the previously defined reference points of interest are those of each measuring element of the system; this system serves both the measurement of the movement and the identification of the geometrical parameters making it possible to characterize the segments of the structure and the position of reference marks of interest with respect thereto;
• - Said measurement system comprises at least one accelerometer.
• the invention discloses a method for determining the position of a set of sensors in a frame linked to a segment of an articulated chain, said set of sensors comprising at least one accelerometer and being integral with said articulated chain.
• said method being characterized in that it comprises: a first step of determining the orientation of a marker linked to the set of sensors relative to the marker linked to said segment for at least one selected configuration of said articulated chain; a second step of estimating the movement of said marker linked to the set of sensors in the terrestrial frame during at least one movement of said segment; a third step of calculating said position of said set of sensors in the frame linked to said segment, said third stage receiving as input the estimation of the movement of said marker linked to the sensor at the output of the second stage and the measurements of said accelerometer during said less a movement.
• the first step comprises a first sub-step of calculating a first matrix of passage of said reference frame linked to the set of sensors to a grounded reference frame and a second substep of calculating a second matrix of passage of said land-bound mark to a mark related to said segment.
• the first calculation sub-step uses at least one measurement of at least one second sensor of said set of sensors, said second sensor being able to provide measurements of at least one physical field that is substantially uniform in time and in time. space or speed of rotation.
• the first calculation step further comprises a substep of computation prior to said first substep during which a third transition matrix is calculated between a moving marker and said marker linked to the earth, said third matrix
• the passageway is either selected or determined from measurements of at least one substantially uniform physical field in time and space or measurements of the rotational speed of said moving mark relative to said earth-bound mark.
• the first step is performed for at least two configurations of said articulated chain.
• a first substep of determining a substantially invariant axis of rotation of said segment is carried out prior to the first step.
• the second step uses the outputs of at least one sensor selected from the group comprising the accelerometer and a second sensor of said set of sensors, said second sensor being able to provide measurements of at least one substantially uniform physical field in time and space or speed of rotation.
• said at least one movement of the segment is a rotation of substantially invariant axis.
• a predictive model is used of the outputs of the accelerometer chosen as a function of the type of movement of said segment and the position of said set of sensors on said output segment is calculated. an algorithm that minimizes errors between measured values and predicted values.
• said articulated chain comprises at least N segments, N being greater than or equal to two.
• the method of the invention further comprises a step during which the length of at least one segment of said articulated chain is calculated.
• the calculation of a segment i inserted in an articulated chain comprising j segments, j being greater than 1 and i is performed by solving the equation in which:
• said articulated chain is a part of a human body or a humanoid structure.
• the configurations of said articulated chain are determined by executing at least N predefined successive gestures, each gesture allowing only a rotation of all or part of the segments of said chain in a single plane around a single passing axis. by an articulation connecting two segments, the segments other than the two said segments remaining aligned during said rotation, so that rotations of segments are performed around at least N distinct axes.
• N> 3, a first segment corresponding to a shoulder, a second segment corresponding to an arm connected to the shoulder and a third segment corresponding to a forearm connected to the arm by an elbow
• the execution of predefined gestures including, in order: a rotation of the entire body about a vertical axis (105) comparable to the axis of the body, the shoulder-arm-forearm assembly being held taut in a horizontal plane during the rotation of the body about said axis, and; a rotating the arm-forearm assembly about a horizontal axis (205) and passing through the joint connecting the shoulder to the arm, the arm-forearm assembly being held taut during said rotation, and; a rotation of the forearm about a horizontal axis (305) and passing through the elbow connecting the arm to the forearm, the shoulder-arm assembly being held taut during said rotation.
• each rotation of segments is performed around an axis passing through an articulation.
• the invention also discloses a system for determining the position of a set of sensors in a frame linked to a segment of an articulated chain, said set of sensors comprising at least one accelerometer and being integral with said articulated chain, said system characterized in that it comprises a first module for determining the orientation of a marker linked to the set of sensors to said marker linked to said segment for at least one configuration of said articulated chain; a second module for estimating the movement of said marker linked to the set of sensors in the terrestrial frame during at least one movement of said segment; a third module for calculating said position of said set of sensors in the frame linked to said segment, said third module receiving as input the estimation of the movement of said reference frame linked to the sensor at the output of the second module and the measurements of said accelerometer during said at least a movement.
• the present invention has the main advantage of accurately and automatically identifying, fast and practical critical geometric parameters of an articulated structure and a plurality of reference marks.
• the invention is particularly advantageous because it expresses the estimation of said parameters in the form of a linear least squares problem, the calculation of the estimate is therefore explicit and optimal.
• FIG. 1 specifies the pins used in the description of the present invention
• FIG. 2 represents a general flowchart of the treatments in several embodiments of the invention
• FIGS. 3a to 3e represent different variants of the invention in several of its embodiments
• FIG. 4 illustrates the articulated structure (human being in the figure) equipped with a set of devices and the associated measurement system which will make it possible to identify the geometrical parameters of the structure and the devices whose markers are the reference marks of interest;
• FIG. 5 illustrates a first movement of a human being carrying sensors of a measuring system whose markers are the reference marks of interest, in one embodiment of the invention
• FIG. 6 illustrates a second movement of a human being carrying sensors of a measuring system whose markers are the reference marks of interest, in one embodiment of the invention. ;
• FIG. 7 illustrates a third movement of a human being carrying sensors of a measuring system whose markers are the reference marks of interest, in one embodiment of the invention.
• the articulated structure is composed of at least one first segment that can be movable in space.
• the following segments are attached one after the other in the form of a tree that can have several branches.
• the measurement system comprises sensors, arranged on the segments of the articulated structure, whose marks are the reference points of interest.
• the present invention aims a method using:
• the sensors of the fitted measurement system comprising at least one accelerometer
• FIG. 1 specifies the pins used in the description of the present invention.
• R D is the index of interest, 101.
• the sensors used to perform the measurements will be placed on the reference of interest, at least for the time of the measurement.
• the terms "reference of interest” or “reference linked to the set of sensors” will be alternately used to designate the reference 101.
• Rs is the segment-related landmark, 02.
• Rg is the landmark linked to the center of gravity of the body, 103.
• R T is the fixed marker, 104.
• the fixed marker is for example linked to the Earth.
• FIG. 2 shows a general flowchart of the treatments in several embodiments of the invention.
• This orientation can be a directly accessible datum or it can be determined in one or more configurations of the articulated structure, as illustrated later in the description.
• the articulated structure is also made to perform at least one more or less simple movement, in order to obtain measurements of the orientation and position parameters of the reference frame linked to the set of sensors that are available, so as to solve the equation of the movements that are made and to deduce the estimate of the parameters that characterize the position of the set of sensors in the frame of the segment.
• either the orientation of the sensor assembly is directly fixed in the segment marker 103, or the orientation of the sensor assembly is determined.
• the references 401, 401a, 402, 402a, 403, 403a of Figure 4 in the reference fixed reference, 104, making the articulated structure take one or more configurations, which determine said orientation, and thus a matrix of passage between the reference mark 101 and the mark 104, then a marker matrix 104 is determined at mark 102.
• the structure is made to articulated at least one movement for which it is possible to determine a predictive model of the measurements of the sensors belonging to the set of sensors 401, 401a, 402, 402a, 403, 403a.
• Figure 3a is shown the flowchart of the treatments of Figure 2 in a first embodiment.
• the set of sensors comprises a means for measuring the orientation Benchmarks of interest 101 relative to the fixed land-bound landmark (RT, 104).
• Different sensors are able to provide measurements with respect to substantially invariant fields in time and space (gravity, the earth's magnetic field) or with respect to a fixed reference in the reference numeral 104, such as magnetic sensors optical, acoustic or radiofrequency positioned in the set of sensors or on a fixed base in connection with a fixed base relative to the mark 104 or with sensors positioned in the set of sensors.
• gyrometers are able to provide this information.
• Magnetometers are also capable of playing this role, as well as optical, acoustic or radiofrequency means.
• the first step 201, 202 that identifies the target matrix consists of adopting predefined postures or poses and therefore, known as and therefore, by transitivity of the matrices of rotations the matrix
• the second step 203 consists in taking gestures and analyzing the accelerometric measurement by exploiting the knowledge of in order to estimate the parameters of lengths and distances, by relying on the law of composition of the movements which links the accelerations of the various points concerned.
• the third step 204 of estimating the position parameters of the set of sensors on the segment is explained later in the description.
• FIG. 3d represents the flowchart of the treatments of an embodiment in which the orientation of the reference mark 101 is already available in the reference mark 102, where a means is available. to measure said orientation. A matrix is then determined which makes it possible to go directly from the reference of interest to the mark of the segment,
• the second step 203 consists of performing protocol movements, for which the trajectory of all the segments equipped ( ⁇ , ⁇ , ⁇ ) must be imposed independently of the time or the speed profile of execution.
• the accelerometric data measured over time during this gesture is then elastically approximated (elastic time deformation) of the expected measurement model linked to the predefined trajectory, for example by an error minimization or maximization of the likelihood ratio operation having as variables the desired parameters.
• the third step 204 (which may optionally be simultaneous in step 203) for estimating the position parameters of the set of sensors on the segment is explained later in the description.
• Figure 3e shows the flowchart of processing of a 4 th embodiment of the invention in which has a means to measure the orientation
• the same means as used in the embodiment of FIG. 3a may be suitable, for example, for optical systems, ultrasonic systems or any other system which has fixed base in the land reference.
• the first step 201, 202 consists in making protocol movements, with a substantially invariant axis of rotation, so that using a measuring system comprising at least one accelerometer, the rotation matrix can be identified and thus reduced to in the first case above.
• the third step 204 of estimating the position parameters of the set of sensors on the segment is explained later in the description.
• Figure 4 illustrates a particular case where the articulated structure (400) is a human being who is equipped on only part of his body: left shoulder and arms.
• the shoulder as well as the arm and forearm are respectively equipped with the devices (401a, 402b, 403b) and at the same locations the sensors of said measurement system (401, 402, 403).
• Figure 5 illustrates a first movement of a human carrying sensors (401, 402, 403) of a measurement system, in one embodiment of the invention.
• all the devices shown in FIG. 4 and the measurement system are combined and consist of sensors associating accelerometers and magnetometers (Embodiment illustrated in FIG. 3b).
• the applicants used sensors 401, 402 and 403 marketed by one of the applicants under the trade name MotionPod and which each combine a triax accelerometer with a triaxial magnetometer.
• MotionPod marketed by one of the applicants under the trade name MotionPod and which each combine a triax accelerometer with a triaxial magnetometer.
• Motion Controller a box commonly called Motion Controller, this box being connected to a computer via a USB link. The case and the computer are not shown in the figure.
• the data is usable on the computer through a programming interface that the applicants market under the trade name Smart Motion Development Kit (SMDK).
• SMDK Smart Motion Development Kit
• the SMDK programming interface allows to obtain raw and calibrated measurements of a MotionPod, or to obtain an estimation of the orientation of a MotionPod.
• the method for identifying geometric parameters comprises a step of evaluating the orientation of the sensors.
• this exemplary embodiment (FIGS. 5, 6, 7)
• the larger the series the better the accuracy. Only one measurement is sufficient if the magnetic field is perfectly known and if the orientation of the segment is determined exactly, but this is not the case in human movements.
• the body is first placed in a posture called "posture 1" which corresponds to the reference posture, that is to say with all angles to 0. Then it is turned (for example) 90 ° clockwise to reach the posture called "posture 2". It is then known that the sensors 401, 402 and 403 measure (the equations being valid for all these sensors):
• Or refers to a measurement taken by the accelerometer when the body occupies the posture ;
• o denotes the Earth's magnetic field
• o is the angle between ; designate the values of the fields
• the first expression is an average of the vector products of the measurements of the sensors used and that the second expression (cos (GH)) is an average of the dot products. measurements of the sensors used.
• the rotation matrix is determined by:
• This data is then included in the measurement model of the sensors in the form of angle triplet.
• a step is made to evaluate the lengths of the segments and the positions of the sensors on the segments by means of a gesture protocol. This step relies in particular on an algorithm aiming at reducing the number of degrees of freedom by allowing only plane rotations along constant axes, in order to exploit the a priori knowledge of the constant vector to solve the system.
• the method for detecting a substantially invariant axis of rotation described in the patent EP1985233 already cited makes it possible, using only the measurements of the magnetometers under the condition of plane motion to which the structure of the sensors is constrained, to find the movement, that is to say to deduce the axis of rotation in the magnetometer and the accelerometer, as well as to deduce the angle of rotation.
• This makes it possible to validate the evaluation of the orientation of the sensors carried out in the previous step and even to refine it.
• This also makes it possible to verify that the orientation of the different sensors is the same, that is to say that the axis of rotation calculated from the measurements of the accelerometer is identical to that calculated from the measurements of the magnetometer. undergoing the same movement plan. If this is not the case, it is necessary to carry out an identification of the box geometric parameters, that is to say an identification of the relative geometrical parameters of the relative orientation of the magnetometer and the accelerometer.
• the accelerometer measurements are used to determine the distance of each sensor to the axis of rotation.
• the measurements are transformed in the expected reference thanks to the orientation matrices evaluated during the previous step, in order to work with respect to the segments of the body and not with respect to the sensors.
• the identification of the geometrical parameters must be made in the order in which they are described in the present exemplary embodiment.
• the axes of rotation naturally pass through the joints of the body. It is therefore necessary to define a protocol to excite enough axes to determine the three components of the vectors lengths and positions.
• FIG. 5 illustrates a rotation of the entire body about a vertical axis 505 assimilable to the axis of the body, the shoulder-arm-forearm assembly being held taut in a horizontal plane during the rotation of the body around the body.
• o is the measurement taken by the sensor magnetometer ;
• o denotes a function that returns the axis of rotation obtained by the method described in patent EP1985233 already cited;
• o denotes a function that returns the arithmetic mean.
• FIG. 6 illustrates a rotation of the arm-forearm assembly about a horizontal axis 605, perpendicular to the plane of the figure and passing through the articulation connecting the shoulder to the arm, the arm-forearm assembly being held taut during rotation.
• FIG. 7 illustrates a rotation of the forearm about a horizontal axis 705, perpendicular to the plane of the figure and passing through the articulation connecting the arm to the forearm, that is to say the elbow, the shoulder-arm assembly being held taut during rotation.
• This method is advantageous because it expresses the estimate as a linear least squares problem, so calculating the estimate is explicit and optimal.
• the measurement model is advantageously solved, even if only a small number of gyrometers are available to complete the measurements of accelerometers and magnetometers, by calculating pseudo-static states which can to be substituted, each time the system is in a pseudo-static state, with the values calculated by a state observer of the Kalman type.

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