Patent Publication Number: US-2021169373-A1

Title: Gait profiler system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefits of U.S. provisional patent application No. 62/286,902 filed on Jan. 25, 2016, which is herein incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a gait profiler system and method for determining the gait profile of a user. 
     BACKGROUND 
     Assistive mobility device, such as actuated orthoses, providing optimal knee assistance (i.e. energy injection during more than 99% of the user&#39;s activities) require knowledge of the state of the leg of the user, that is either a) in a stance state (i.e. in contact with the ground or b) in a swing state. 
     A common method of accomplishing this is using pressure sensors. However, this method has drawbacks, mainly:
         pressure sensors have to be placed into the sole of the user&#39;s shoe or create a sole that can be adapted to fit all shoes;   the accuracy of the pressure sensors is sensitive to the user&#39;s specific stance, (depends on which part of the foot is pressed when engaged to the ground), unless a plurality of pressure sensors are used; and   pressure sensors can be brittle and break after a short use.       

     Accordingly, there is a need for a gait profiler system and method for determining the gait profile of a user that overcomes the pressure sensor&#39;s drawbacks. 
     SUMMARY 
     The present disclosure provides a gait profiler system for determining the gait profile of a user, comprising:
         a first sensing system associated with a right foot of the user, including:   a first inertial sensor;   a first securing mechanism configured to secure the first sensing system to the right foot of the user;   a first set of external sensors observing a right shank, thigh and trunk spatial orientation;   a second sensing system associated with a left foot of the user, including:   a second inertial sensor;   a second securing mechanism configured to secure the second sensing system to the left foot of the user;   a second set of external sensors observing a left shank, thigh and trunk spatial orientation;   at least one processor in communication with the first and second inertial sensors and the first and second sets of external sensors, the at least one processor having an associated memory comprising instructions stored thereon, that when executed on the processor perform the steps of:   receiving biomechanics information about the user from the first and second inertial sensors;   receiving biomechanics information from the first and second sets of external sensors;   generating locomotion-related information for the right foot of the user using the biomechanics information from the first inertial sensor and the first set of external sensors;   generating locomotion-related information for the left foot of the user using the biomechanics information from the second inertial sensor and the second set of external sensors;   calculating a locomotion state of the user (for example stance state or swing state) by merging the locomotion-related information of the right foot and left foot; and   generating the gait profile of the user using the locomotion state of the user.       

     The present disclosure also provides a gait profiler system as described above, wherein the first and second sets of external sensors include a pair of inertial sensors configured to be positioned at respective right and left leg-knee or thigh-hip structures and a plurality of sensors providing information indicative of the angular positions of the right and left knee and thigh of the user. 
     The present disclosure further provides a gait profiler system as described above, wherein the various sensors are provided by an exoskeleton or orthotic devices worn by the user. 
     The present disclosure further provides a gait profiler system as described above, wherein the step of merging the locomotion-related information of the right foot and of the left foot of the user is performed using a sensor fusion algorithm comprising the sub-steps of:
         determining a static state of each of the right foot and of the left foot of the user using the locomotion-related information of the right foot and of the left foot;   determining a dynamic state of each of the right foot and of the left foot of the user using the locomotion-related information of the right foot and of the left foot; and   determining the locomotion state of the user using the static state and the dynamic state of each of the right foot and of the left foot of the user.       

     The present disclosure still further provides a gait profiler system as described above, wherein the step of generating the gait profile of the user includes the sub-steps of:
         calculating secondary gait information using at least one of the biomechanics information about the user from the first and second inertial sensors and the biomechanics information from the first and second sets of external sensors;   calculating the gait profile based on the locomotion state of the user, the locomotion state having an associated model gait profile; and   optimizing the gait profile based on the secondary gait information.       

    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       Embodiments of the disclosure will be described by way of examples only with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic representation of a gait profiler system; 
         FIG. 2  is a schematic representation of the gait profiler system in accordance with an illustrative embodiment of the present disclosure; 
         FIG. 3  is a flow diagram of the state calculation process in accordance with the illustrative embodiment of the present disclosure; 
         FIG. 4  is a flow diagram of the sensor fusion algorithm sub-steps of the state calculation process of  FIG. 3 ; and 
         FIG. 5  is a flow diagram of the gait profile calculation process in accordance with the illustrative embodiment of the present disclosure. 
     
    
    
     Similar references used in different Figures denote similar components. 
     DETAILED DESCRIPTION 
     Generally stated, the non-limitative illustrative embodiment of the present disclosure provides a system and method for determining the gait profile of a user. The gait profiler system uses sensing systems that include inertial sensors configured to be positioned at the right and left foot-ankle structure, as well as spatial orientation of lower extremity body segments (shanks, thighs, and trunk) of the person for which the gait profile is to be determined. In an illustrative embodiment, the gait profiler system uses two additional inertial sensors at the left and right leg-knee or thigh-hip structure as well as sensors providing information indicative of the angular positions of the left and right knee and thigh, which may be provided by an exoskeleton or orthotic devices worn by the user, such as described, for example, in U.S. Pat. No. 9,370,439 entitled “LOAD DISTRIBUTION DEVICE FOR HUMAN JOINTS”. This determination of the gait profile of the user is performed using biomechanics information about the user from the inertial sensors combined with the knee and hip angles. 
     Referring to  FIG. 1 , the gait profiler system  10  includes one or more processor  12  with an associated memory  14  comprising instructions stored thereon, that when executed on the processor  12 , perform the steps of the state calculation process  100  and the gait profile calculation process  200 , which processes will be further described below, and an input/output (I/O) interface  16  for communication with a right foot  20   a  and a left foot  20   b  sensing systems and external sensors observing the right  30   a  and left  30   b  shank, thigh and trunk spatial orientation through communication link  18 , which may be wired, wireless or a combination of both. 
     Each of the sensing systems  20   a ,  20   b  includes, respectively, an associated inertial sensor  22   a ,  22   b  (providing biomechanics information about a respective foot of the user) and a securing mechanism  24   a ,  24   b  configured to secure the sensing systems  20   a ,  20   b , for example, right below the medial malleolus of an associated foot of the user. 
     In an illustrative embodiment of the gait profiler system  10 , shown in  FIG. 2 , the external sensors  30   a ,  30   b  take the form of right  30 ′ a  and left  30 ′ b  knee or thigh inertial and knee and hip angular positions sensors. 
     It is to be understood that the knee and hip angular position sensors  30 ′ a ,  30 ′ b  may take the form of any sensors providing information indicative of angular position or from which angular position may be generated as the knee and hip angles may be determine by direct measurement or deduced from biomechanics information provided by a variety of types of sensors. 
     Referring to  FIG. 3 , there is shown a flow diagram of the state calculation process  100  executed by the one or more processor  12  (see  FIGS. 1 and 2 ) in accordance with the illustrative embodiment of the present disclosure. Steps of the process  100  are indicated by blocks  102  to  110 . 
     The process  100  starts at block  102  where the biomechanics information and knee and hip angles from the associated inertial sensors  20   a ,  20   b  and the external sensors  30   a ,  30   b  are provided to the one or more processor  12 . 
     At block  104 , optionally, the velocity is calculated by integrating the acceleration expressed in the global coordinates system. 
     At block  106 , optionally, the velocity is corrected and integrated to obtain the position since the last step. 
     Then, at block  108 , the position and velocity (if optional steps  104  and  106  are performed), acceleration, rotation and orientation are merged with a sensor fusion algorithm in order to calculate the locomotion state (i.e. stance or swing state) of the user. 
     Finally, at block  110 , the process  100  provides the stance or swing state of the user and the the locomotion-related information of each foot of the user to the gait profile calculation process  200 . 
     Referring to  FIG. 4 , there is shown a flow diagram of the sensor fusion algorithm sub-steps used in step  108  of the state calculation process  100  of  FIG. 3 . The sensor fusion algorithm sub-steps are indicated by blocks  1082  to  1086 . 
     At block  1082 , the static state of each of the right foot and left foot of the user is determined using the biomechanics information, i.e. is the foot in contact with the ground and is motionless or not, etc. 
     Then, at block  1084 , the dynamic state of each of the right and left foot of the user is determined using the biomechanics information, i.e. is the foot in motion, is it part of a locomotion cycle or not, etc. 
     Finally, at block  1086 , the algorithm determines the locomotion state (i.e. stance or swing state) of the user. To this end, the static and dynamic states of the right foot and the left foot are used (i.e. static right foot, static left foot, dynamic right foot, dynamic left foot), the various combinations of the right foot and left foot states determining if the user is in a stance or swing state. It is to be understood that other biomechanics information may be used to complement the static and dynamic states of the right foot and the left foot. 
     Referring now to  FIG. 5 , there is shown a flow diagram of the gait profile calculation process  200  executed by the one or more processor  12  (see  FIGS. 1 and 2 ) in accordance with the illustrative embodiment of the present disclosure. Steps of the process  200  are indicated by blocks  202  to  210 . 
     The process  200  starts at block  202  where the locomotion state (i.e. stance or swing state) of the user and the the locomotion-related information of each foot of the user is obtained from the state calculation process  100  (see  FIG. 3 ). 
     At block  204 , the secondary gait information such as user activity, slope, cadence, etc., is calculated from the biomechanics information and knee and hip angles. 
     At block  206 , a torque profile is calculated based on the stance or swing state of the user. Each state is provided with a model torque profile, i.e. stance state torque and swing state torque profiles 
     Then, at block  208 , the torque profile is optimized based on the user secondary gait information. This means that when a change of locomotion state and/or secondary gait information is detected, the torque profile is adjusted in order to limit the effects of those changes on the gait of the user. 
     Finally, at block  210 , the process  200  provides the torque profile (i.e. gait profile) of the user. 
     It is to be understood that in alternative embodiments the state calculation process  100  and the gait profile calculation process  200  may be executed on a single or separate processors  12  and that the state calculation process  100  may be executed on separate processors  12  for the right and left foot of the user, the inertial sensors  20   a ,  20   b  and external sensors  30   a ,  30   b  providing their information directly to their associated processor  12 . 
     Although the present disclosure has been described by way of particular non-limiting illustrative embodiments and examples thereof, it should be noted that it will be apparent to persons skilled in the art that modifications may be applied to the present particular embodiment without departing from the scope of the present disclosure as hereinafter claimed.