Method for locating a device which is moved in a three-dimensional space
First Claim
1. A method comprising locating a device that has been displaced inside a three-dimensional space, wherein said device comprisesan inertial platform,an electronic locating-unit, anda bus,wherein said electronic locating-unit comprises a programmable electronic computer and a memory,wherein said programmable electronic computer is capable of executing instructions stored in said memory,wherein said inertial platform comprises sensors that are onboard said displaced device, wherein said sensors comprise an accelerometer,wherein said bus connects said inertial platform to said electronic locating-unit,wherein said electronic-locating unit is configured to detect, based at least in part on measurements provided by said accelerometer and provided to said electronic locating-unit by said bus, movement of said inertial platform, said movement being indicative of said displacement of said device,wherein said memory stores a map of said three-dimensional space and instructions for execution by said programmable electronic computer,wherein said method comprisesexecuting a first step,executing a second step,repeating a sequence of steps, said sequence comprisinga third step,a fourth step, anda fifth step,wherein said first step comprises providing said map of said three-dimensional space and of predefined constraints on displacements of said device in said three-dimensional space,wherein said second step comprises generating a number of distinct particles, said number depending on initial knowledge about a location of said device, wherein each of said distinct particles is associated with coordinates that code a position of said particle in said map and a weight that represents a probability that said device is situated at said position,wherein said third step comprises receiving measurements representative of a magnitude and direction of displacement of said device from a previous position thereof, said measurements having been carried out by said sensors onboard said displaced device,wherein said fourth step comprises executing a transformation of each particle, wherein executing a transformation comprises updating coordinates of positions of each particle as a function of said measurements received during said third step with the aid of a predetermined displacement law, said predetermined displacement law being a law for displacing said particle from a previous position to a new position in a manner that is correlated with said measured displacement of said device, each displacement law comprising a first measured-variable and a second measured-variable, said first measured-variable having a value that depends on said measurement of said direction of displacement received during said third step and said second measured-variable having a value that depends on said measurement of said amplitude of said displacement received during said third step,wherein said fifth step comprises, for each particle, if a latest displacement of said particle from said previous position to said new position satisfies said predefined constraints, increasing said weight associated with said particle relative to weights of said particles whose latest displacement fails to satisfy said predefined constraints, said weights comprising highest weights and lowest weights,wherein said fifth step comprises estimating said position of said device on said basis of said positions of said particles and of said weights associated with said particles,wherein estimating said position of said device comprises allotting more importance to positions of particles associated with said highest weights,wherein said displacement law comprises using an arithmetical operation to combine a corrective factor with one of said measured variables, said corrective factor being corrective of a bias,wherein each particle is associated with a current value of said corrective factor, said current value of said corrective factor being constructed at each iteration of said fourth step based on a previous current-value of said corrective factor that was computed during a previous iteration of said fourth step and to which is added a random variable drawn according to a predefined probability law, said current values of various particles having been initialized to corresponding initial values before said first execution of said fourth step, andwherein, during said fourth step, for each particle whose coordinates are updated with said aid of said displacement law, said value of said corrective factor in said displacement law is set equal to said current value of said corrective factor associated with said particle, after several iterations of said sequence of steps, re-sampling said particles,wherein resampling said particles comprises carrying out another transformation on said set of particles,wherein said another transformation comprises eliminating particles that are associated with said lowest weights, automatically generating new particles to replace said eliminated particles, and assigning a new current-value of said corrective factor to each new particle, each new value of said corrective factor being dependent on one or more of said corrective factor'"'"'s current values associated with said particles that have not been eliminated and independent of said corrective factor'"'"'s current values associated with said particles that have been eliminated.
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Abstract
A method of location of a device includes a displacement law containing a corrective factor of a bias combined by an arithmetical operation with a measured variable, and particles, each particle being associated with a current value of the corrective factor. The current value of the corrective factor being constructed at each iteration on the basis of a previous current value of the corrective factor, computed during a previous iteration, to which is added a random variable drawn according to a predefined probability law. The current values of various particles are initialized, before the first iteration, to various initial values, and during each iteration, for each particle whose coordinates are updated with the aid of this displacement law, the value of the corrective factor in the displacement law is taken equal to this corrective factor'"'"'s current value associated with the particle.
11 Citations
11 Claims
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1. A method comprising locating a device that has been displaced inside a three-dimensional space, wherein said device comprises
an inertial platform, an electronic locating-unit, and a bus, wherein said electronic locating-unit comprises a programmable electronic computer and a memory, wherein said programmable electronic computer is capable of executing instructions stored in said memory, wherein said inertial platform comprises sensors that are onboard said displaced device, wherein said sensors comprise an accelerometer, wherein said bus connects said inertial platform to said electronic locating-unit, wherein said electronic-locating unit is configured to detect, based at least in part on measurements provided by said accelerometer and provided to said electronic locating-unit by said bus, movement of said inertial platform, said movement being indicative of said displacement of said device, wherein said memory stores a map of said three-dimensional space and instructions for execution by said programmable electronic computer, wherein said method comprises executing a first step, executing a second step, repeating a sequence of steps, said sequence comprising a third step, a fourth step, and a fifth step, wherein said first step comprises providing said map of said three-dimensional space and of predefined constraints on displacements of said device in said three-dimensional space, wherein said second step comprises generating a number of distinct particles, said number depending on initial knowledge about a location of said device, wherein each of said distinct particles is associated with coordinates that code a position of said particle in said map and a weight that represents a probability that said device is situated at said position, wherein said third step comprises receiving measurements representative of a magnitude and direction of displacement of said device from a previous position thereof, said measurements having been carried out by said sensors onboard said displaced device, wherein said fourth step comprises executing a transformation of each particle, wherein executing a transformation comprises updating coordinates of positions of each particle as a function of said measurements received during said third step with the aid of a predetermined displacement law, said predetermined displacement law being a law for displacing said particle from a previous position to a new position in a manner that is correlated with said measured displacement of said device, each displacement law comprising a first measured-variable and a second measured-variable, said first measured-variable having a value that depends on said measurement of said direction of displacement received during said third step and said second measured-variable having a value that depends on said measurement of said amplitude of said displacement received during said third step, wherein said fifth step comprises, for each particle, if a latest displacement of said particle from said previous position to said new position satisfies said predefined constraints, increasing said weight associated with said particle relative to weights of said particles whose latest displacement fails to satisfy said predefined constraints, said weights comprising highest weights and lowest weights, wherein said fifth step comprises estimating said position of said device on said basis of said positions of said particles and of said weights associated with said particles, wherein estimating said position of said device comprises allotting more importance to positions of particles associated with said highest weights, wherein said displacement law comprises using an arithmetical operation to combine a corrective factor with one of said measured variables, said corrective factor being corrective of a bias, wherein each particle is associated with a current value of said corrective factor, said current value of said corrective factor being constructed at each iteration of said fourth step based on a previous current-value of said corrective factor that was computed during a previous iteration of said fourth step and to which is added a random variable drawn according to a predefined probability law, said current values of various particles having been initialized to corresponding initial values before said first execution of said fourth step, and wherein, during said fourth step, for each particle whose coordinates are updated with said aid of said displacement law, said value of said corrective factor in said displacement law is set equal to said current value of said corrective factor associated with said particle, after several iterations of said sequence of steps, re-sampling said particles, wherein resampling said particles comprises carrying out another transformation on said set of particles, wherein said another transformation comprises eliminating particles that are associated with said lowest weights, automatically generating new particles to replace said eliminated particles, and assigning a new current-value of said corrective factor to each new particle, each new value of said corrective factor being dependent on one or more of said corrective factor'"'"'s current values associated with said particles that have not been eliminated and independent of said corrective factor'"'"'s current values associated with said particles that have been eliminated.
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10. An apparatus for locating a device displaceable inside a three-dimensional space, the apparatus comprising
a memory and a processor, wherein the memory contains a map of the three-dimensional space and predefined constraints on the displacements of the device in the three-dimensional space, and wherein the processor is configured to execute a first step, execute a second step, repeat a sequence of steps, the sequence comprising a third step, a fourth step, and a fifth step, wherein the first step comprises providing the map of the three-dimensional space and of predefined constraints on displacements of the device in the three-dimensional space, wherein the second step comprises generating distinct particles, each of the distinct particles being associated with coordinates that code a position of the particle in the map and with a weight that represents a probability that the device is situated at the position, wherein the third step comprises receiving measurements representative of a magnitude and direction of displacement of the device from a previous position thereof, the measurements having been carried out by sensors onboard the displaced device, wherein the fourth step comprises updating coordinates of positions of each particle as a function of the measurements received during the third step with the aid of a predetermined displacement law, the displacement law being a law for displacing the particle from a previous position to a new position in a manner that is correlated with the measured displacement of the device, each predetermined displacement law comprising a first measured-variable and a second measured-variable, the first measured-variable having a value that depends on the measurement of the direction of displacement received during the third step and the second measured-variable having a value that depends on the measurement of the amplitude of the displacement received during the third step, wherein the fifth step comprises, for each particle, if the latest displacement of the particle from the previous position to the new position satisfies the predefined constraints, increasing the weight associated with the particle relative to weights of the particles whose latest displacement fails to satisfy the predefined constraints, the weights comprising highest weights and lowest weights, wherein the fifth step comprises estimating the position of the device on the basis of the positions of the particles and of the weights associated with the particles, wherein estimating the position of the device comprises allotting more importance to positions of particles associated with the highest weights, wherein the displacement law comprises using an arithmetical operation to combine a corrective factor with one of the measured variables, the corrective factor being corrective of a bias, wherein each particle is associated with a current value of the corrective factor, the current value of the corrective factor being constructed at each iteration of the fourth step based on a previous current-value of the corrective factor that was computed during a previous iteration of the fourth step and to which is added a random variable drawn according to a predefined probability law, the current values of various particles having been initialized to corresponding initial values before the first execution of the fourth step, and wherein, during the fourth step, for each particle whose coordinates are updated with the aid of the displacement law, the value of the corrective factor in the displacement law is set equal to the current value of the corrective factor associated with the particle, after several iterations of said sequence of steps, re-sampling the particles, wherein resampling the particles comprises eliminating particles that are associated with the lowest weights, automatically generating new particles to replace the eliminated particles, and assigning a new current-value of the corrective factor to each new particle, each new value of the corrective factor being dependent on one or more of the corrective factor'"'"'s current values associated with the particles that have not been eliminated and independent of the corrective factor'"'"'s current values associated with the particles that have been eliminated.
Specification