Patent Publication Number: US-2023158663-A1

Title: Support foot for an exoskeleton for carrying loads, exoskeleton comprising said support foot and method of controlling an exoskeleton

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to Italian Patent Application no. 102021000029327 filed on Nov. 19, 2021, the entire contents of which is incorporated herein by reference. 
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The disclosure relates to a support foot for an exoskeleton to be worn to carry loads and to an exoskeleton comprising said support foot. 
     The disclosure further relates to a method for controlling an exoskeleton. 
     2. Description of Related Art 
     As it is known, wearable exoskeletons are used to increase a user&#39;s moving capacities. An exoskeleton typically comprises two support feet, each capable of being coupled to a foot of a user of the exoskeleton so as to support the user&#39;s weight; a plurality of movable parts, each capable of being coupled to a limb or to the trunk of the user; and a plurality of joints, which connect two or more movable parts to one another and can be active, semi-active or passive. 
     Each joint is configured to control the relative movement of the movable parts, which it connects so as to affect the dynamic behaviour of a given articulation of the user and assist the user while moving said articulation. 
     By way of example, in case the exoskeleton is used to support the user while carrying a load, the exoskeleton comprises a plurality of mechanical joints, which are configured to act upon the dynamic behaviour of the knee and hip articulations of the user and are provided with respective actuators to provide and operating torque so as to relieve the legs of the user from the weight of the carried load and follow the movement of said articulations. 
     In known exoskeletons, active and semi-active mechanical joints are controlled by a control unit, which is configured to receive, as an input, control parameters detected by sensors and to control the actuation of said mechanical joints. 
     By way of example, the control parameters comprise the relative position and/or acceleration of the movable parts connected by each mechanical joint and forces/torques exerted upon the mechanical joints and upon the movable parts of the exoskeleton. 
     In order to best control the mechanical joints of the exoskeleton, the control unit needs to receive, as an input, numerous control parameters and, as a consequence, the exoskeleton needs to be provided with a large number of sensors. 
     However, the large quantity of sensors makes the exoskeleton bulky and increases the manufacturing costs thereof. 
     SUMMARY OF THE DISCLOSURE 
     An object of the disclosure is to provide a support foot for an exoskeleton capable of overcoming the drawbacks of the prior art. 
     In particular, an object of the disclosure is to provide a support foot for an exoskeleton, which is ergonomic, not bulky and economic to be manufactured. 
     According to the disclosure, there is provided a support foot for an exoskeleton for carrying loads configured to house a foot of a user of the exoskeleton; the support foot comprising:
         a front support assembly, which is configured to support a front portion of the foot of the user of the exoskeleton;   a rear support assembly, which is configured to support a rear portion of the foot of the user of the exoskeleton;   a flexible plate, which connects the front support assembly and the rear support assembly;   at least one first sensor, which is arranged in the front support assembly and is configured to detect a pressure exerted by the foot of the user upon the front support assembly; and   a second sensor, which is arranged in the rear support assembly and is configured to detect components of at least one force and/or components of at least one torque exerted by the foot of the user upon the rear support assembly along three Cartesian axes.       

     Thanks to the disclosure, the user of the exoskeleton can easily move on each kind of ground. In particular, the flexibility of the plate allows the user to bend the sole of the foot so as to comfortably and effectively walk on inclined surfaces and adjust to uneven grounds. 
     Furthermore, thanks to the first and the second sensor, it is possible to detect a distribution of the forces and of the torques exerted by the foot of the user of the exoskeleton, ensuring, at the same time, the ergonomics of the support foot. The special configuration of the first and of the second sensor limits the dimensions as well as the manufacturing costs of the support foot. 
     More in detail, the first sensor helps reduce the costs and the dimensions of the support foot, whereas the second sensor allows for a more precise detection of the forces and of the torques exerted by the foot of the user upon the rear support assembly. 
     In this way, the moving state of the user of the exoskeleton can be identified as a function of the distribution of the pressures detected by the first sensor and of the forces/torques detected by the second sensor and the active mechanical joints can be controlled as a function of the pressures and of said detected forces/torques, using different strategies. 
     Hereinafter, the terms “front” and “rear” are referred to an advancing direction, which is defined by the forward walk of the user of the exoskeleton. In other words, the term “front” indicates that the element to which it relates is in a more forward position along the advancing direction than a further element to which the term “rear” relates. A further object of the disclosure is to provide method for controlling an exoskeleton for carrying loads capable of overcoming the drawbacks of the prior art. 
     According to the disclosure, there is provided a method for controlling an exoskeleton for carrying loads, the method comprising the steps of:
         detecting pressures exerted by a foot of the user upon a front support assembly of a support foot of the exoskeleton;   detecting force and/or torque components exerted by the foot of the user along three Cartesian axes upon a rear support assembly of the support foot; and   controlling at least one mechanical joint of the exoskeleton as a function of the detected pressures and of the detected force and/or torque components.       

     By so doing, the exoskeleton can be controlled in an ideal manner so as to relieve the legs of the user of the exoskeleton from the weight of the carried load, at the same time following the movement of the articulations of the lower limns of the user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the disclosure are defined in the appended dependent claims and will be best understood upon perusal of the following description of a non-limiting embodiment, with reference to the accompanying figures. 
         FIG.  1    is a perspective view of an exoskeleton for carrying loads according to the disclosure; 
         FIG.  2    is a perspective view of a support foot of the exoskeleton of  FIG.  1   ; 
         FIG.  3    is a side elevation view of the support foot of  FIG.  2   ; 
         FIG.  4    is a cross-sectional view of the support foot of  FIG.  2   ; 
         FIG.  5    is a cross-sectional view, on a larger scale, of a detail of  FIG.  4   ; 
         FIG.  6    is a perspective view, with parts removed for greater clarity, of the support foot of  FIG.  2   ; and 
         FIG.  7    is perspective view of the support foot of the exoskeleton of  FIG.  1    according to a further embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     With reference to  FIG.  1   , reference number  1  indicates, as a whole, an exoskeleton for carrying loads, which can be worn by a user to increase his/her moving capacities. 
     In particular, the exoskeleton  1  is configured to assist the movement of the lower limbs of a user. 
     The exoskeleton  1  comprises a pelvic portion  2 , two mechanical legs  3  connected to the pelvic portion  2  and a bearing portion  4  configured to house a load to be carried, which is not shown in the accompanying figures. 
     In particular, the exoskeleton  1  comprises two mechanical joints  5 , each integrated in the respective mechanical leg  3  in order to control the flexion/extension movement of the knee articulation of a user; two mechanical joints  6 , each arranged between the pelvic portion  2  and the respective mechanical leg  3  in order to control the adduction/abduction movement of the hip articulation of a user; two mechanical joints  7 , each arranged between the pelvic portion  2  and the respective mechanical leg  3  in order to control the flexion/extension movement of the hip articulation of a user; and two mechanical joints  8 , each arranged between the pelvic portion  2  and the respective mechanical leg  3  in order to control the internal/external rotation movement of the hip articulation of a user. 
     Furthermore, the exoskeleton  1  comprises two support feet  9 , each coupled to a respective mechanical leg  3  and configured to house a foot of a user of the exoskeleton  1 . 
     In particular, the exoskeleton  1  comprises two coupling portions  35  to connect each support foot  9  to the respective mechanical leg  3 . Each coupling portion  35  comprises a passive joint  10  arranged between the respective support foot  9  and the respective mechanical leg  3  so as to allow for the dorsiflexion/plantar flexion of the foot of a user; and a passive joint  11  arranged between the respective support foot  9  and the respective mechanical leg  3  so as to allow for the supination/pronation of the foot of a user. 
     Furthermore, each mechanical joint  5 ,  6 ,  7 ,  8  and each passive joint  10 ,  11  comprise a respective angular position sensor  34 , which is configured to detect the relative angular position between the movable bodies connecting them. 
     In particular, the passive joint  11  is located in a zone arranged above the instep of the user, when the exoskeleton  1  is worn by the user. 
     More in detail, the bearing portion  4  is configured to be arranged behind the back of a user of the exoskeleton  1  and comprises at least one power storage device, which is not shown in the accompanying figures, to power each mechanical joint  5 ,  6 ,  7  and  8  and a control unit  33  ( FIG.  6   ) to control each mechanical joint  5 ,  6 ,  7  and  8 . 
     With reference to  FIGS.  2  and  3   , each support foot  9  comprises a front support assembly  12 , which is configured to support a front portion of a foot of a user of the exoskeleton  1 ; a rear support assembly  13 , which is configured to support a rear portion of the foot of a user of the exoskeleton  1 ; and a flexible plate  14 , which connects the front support assembly  12  and the rear support assembly  13 . 
     In particular, the flexible plate  14  is attached to the front support assembly  12  and to the rear support assembly  13  so as to spread the front support assembly  12  apart from the rear support assembly  13 . 
     More in detail, the flexible plate  14  is made of harmonic steel. 
     The front support assembly  12  comprises a front support base  15  configured to rest on a ground and the rear support assembly  13  comprises a rear support base  16  configured to rest on a ground. 
     In the specific case described and shown herein, the front support base  15  and the rear support base  16  are substantially flat and are made of a rigid material. 
     According to an alternative embodiment, the front support base  15  and the rear support base  16  are made of a deformable or flexible material. 
     In particular, the front support assembly  12  comprises a rigid plate  17  attached to a front portion of the flexible plate  14 . 
     According to an embodiment, each support foot  9  comprises a coupling mechanism  19  configured to be arranged around the foot of the user of the exoskeleton  1  so as to lock the foot of the user against the rear support assembly  13 . In particular, the coupling mechanism  19  is coupled to the rear support assembly  13 . 
     Furthermore, the rear support assembly  13  comprises a fixing flange  25 , which is attached to an end portion of the respective mechanical leg  3 . 
     The front support assembly  12  comprises a front strap  23 , which is coupled to the front support assembly  12  and is configured to be placed around a front portion of the foot of the user so as to lock the foot of the user against the front support assembly  12 . 
     In the specific case described and shown herein, which is not limiting for the disclosure, the front support assembly  12  comprises a connection plate  24 , which is arranged between the front portion of the flexible plate  14  and the rigid plate  17  and is connected to the front strap  23 . 
     With reference to  FIG.  3   , the rear support assembly  13  comprises a rigid plate  18  attached to a rear portion of the flexible plate  14 . 
     Furthermore, the coupling mechanism  19  comprises an adjustable latch  26 , preferably a ratchet latch. 
     With reference to  FIG.  4   , the rear support assembly  13  comprises a fixing flange  20 , which is provided with a base wall  21 , which is attached between the rear portion of the flexible plate  14  and the rigid plate  18 , and with two connection walls  22 , each of which extends along a plane transverse to the base wall  21  and is fixed to the coupling mechanism  19 . 
     Each support foot  9  comprises at least one sensor  27 , which is arranged in the front support assembly  12  and is configured to detect a pressure exerted by the foot of the user upon the front support assembly  12 ; and a sensor  28 , which is arranged in the rear support assembly  13  and is configured to detect the components of at least one force and/or the components of at least one torque exerted by the foot of the user upon the rear support assembly  13  along three Cartesian axes. 
     In particular, the sensor  27  is arranged between the flexible plate  14  and the front support base  15 . The sensor  28  is arranged between the flexible plate  14  and the rear support base  16 . 
     More in detail, the flexible plate  14  extends between the front support assembly  12  and the rear support assembly  13  so as to be arranged above the sensor  27  and the sensor  28 . 
     With reference to  FIG.  5   , each support foot  9  comprises a plurality of sensors  27  distributed in the front support assembly  12  in order to detect a distribution of pressures exerted by the foot of the user upon the front support assembly  12 . 
     Each sensor  27  has a mainly planar shape and extends along a plane substantially parallel to the flexible plate  14 . 
     In particular, each sensor  27  is coupled to the front portion of the flexible plate  14 , on the opposite side relative to the rigid plate  17 . 
     According to an embodiment, each sensor  27  is a capacitive sensor. In particular, each sensor  27  comprises ten pressure detection points. 
     According to an embodiment, which is not limiting for the disclosure, each sensor  27  is configured to only detect a pressure exerted by the foot of the user upon the front support assembly  12  in a direction substantially perpendicular to the front support base  15 . 
     With reference to  FIG.  4   , the sensor  28  is a force/torque sensor with six degrees of freedom. In particular, the sensor  28  comprises a plurality of strain gauges connected so as to form an electrical circuit of the Wheatstone bridge kind. 
     According to an embodiment, which is not limiting for the disclosure, the sensor  28  comprises 12 semiconductor strain gauges arranged in a configuration with 6 Wheatstone half-bridge. 
     In particular, the rear support assembly  13  comprises an intermediate plate  29  arranged between the flexible plate  14  and the rear support base  16 . The sensor  28  is arranged between the flexible plate  14  and the intermediate plate  29 . 
     Furthermore, the rear support assembly  13  comprises at least one contact sensor  30 , which is arranged in the rear support assembly  13  and is configured to detect a contact of the rear support assembly  13  with the ground. 
     In the specific case described and shown herein, the rear support assembly  13  comprises a plurality of contact sensors  30  distributed between the intermediate plate  29  and the rear support base  16 . 
     In particular, each contact sensor  30  comprises a switch configured to be selectively activated when the intermediate plate  29  is pushed towards the rear support base  16  due to the weight force of the user of the exoskeleton  1 . 
     The rear support assembly  13  further comprises a plurality of limit stop elements  31 , each arranged between the flexible plate  14  and the rear support base  16  and provided with an elastic element  32  so as to limit the movement of the flexible plate  14  towards the rear support base  16 . 
     With reference to  FIG.  6   , each support foot  9  comprises seven sensors  27 , each with a triangular shape. 
     In particular, the sensors  27  are arranged along a same plane. More in detail, three sensors  27  are arranged in a front portion of the front support assembly  12  and four sensors  27  are arranged in a rear portion of the front support assembly  12 . 
     The number and the distribution of the sensors  27  in the front support assembly  12  can change depending on the specific application of the support foot  9  and are not limiting for the disclosure. 
     The control unit  33  is connected to the sensors  27  in order to receive pressure signals indicative of the pressures detected by the sensors  27  and to the sensor  28  in order to receive force/torque signals indicative of the force and torque components detected by the sensor  28  and is configured to control the mechanical joints  5 ,  6 ,  7  and  8  as a function of the pressure signals and of the force/torque signals received. 
     Furthermore, the control unit  33  is connected to each contact sensor  30  in order to receive contact signals indicative of a contact of the rear support assembly  13  with the ground. 
     In particular, the control unit  33  is configured to estimate a phase of a walk of the user of the exoskeleton  1  as a function of the pressure signals received from the sensors  27 , of the force/torque signals received from the sensor  28  and of the contact signals received from the contact sensors  30 . 
     With reference to  FIG.  7   , a second embodiment of the disclosure is shown, wherein the exoskeleton  1  comprises two coupling portions  36  to couple each support foot  9  to the respective mechanical leg  3 . Each coupling portion  36  comprises a passive joint  37  arranged between the respective support foot  9  and the respective mechanical leg  3  so as to allow for the dorsiflexion/plantar flexion of the foot of a user; and a passive joint  38  arranged between the respective support foot  9  and the respective mechanical leg  3  so as to allow for the supination/pronation of the foot of a user. 
     In particular, the passive joint  38  is located in a zone arranged behind the heel of the user, when the exoskeleton  1  is worn by the user. 
     In use and with reference to  FIG.  4   , when the user of the exoskeleton  1  is in a standing straight position, said user rests the foot on the front support assembly  12  and on the rear support assembly  13 . 
     Under these circumstances, the contact sensors  30  detect that the heel of the user is in contact with the ground. 
     When the user of the exoskeleton  1  moves by walking, the user lifts the heel from the ground, at first keeping the tip of the foot on the ground, thus determining the bending of the flexible plate  14 . Under these circumstances the contact sensors  30  detect that the heel of the user is lifted from the ground. 
     During the use of the exoskeleton  1  by the user, the sensors  27  and  28  of each support foot  9  detect the distribution of the forces and of the torques exerted by the feet of the user upon the respective support feet  9 . 
     The control unit  33  receives, as an input, pressure signals detected by the sensors  27  and force/torque signals detected by the sensor  28  and controls the mechanical joints  5 ,  6 ,  7  and  8  as a function of the pressure signals and of the force/torque signals received. 
     In particular, the control unit  33  estimates in real time a phase of a walk of the user of the exoskeleton  1  as a function of the pressure signals and of the force/torque signals received in order to control the mechanical joints  5 ,  6 ,  7  and  8  so as to follow the movements of the lower limbs of the user of the exoskeleton  1 . 
     More in detail, the control unit  33  estimates in real time the distribution of the forces as a function of the pressure signals and of the force/torque signals received in order to calculate the position of the centre of gravity of the user of the exoskeleton  1  and adjust the commands given to the mechanical joints  5 ,  6 ,  7  and  8  as a function of said calculated position. 
     Finally, the disclosure can evidently be subjected to variants to the embodiment described herein, though without going beyond the scope of protection set forth by the appended claims.