Abstract:
A multifunctional wrist orthotic comprising an electromyography (EMG) sensor having at least two electrodes for attachment to a wrist of a user, an intertial measurement sensor (IMU), a microcontroller unit (e.g., a Arduino® Mini) connected to the IMU, a power supply unit. The microcontroller unit is configured to perform two-tiered gesture recognition, with the first tier comprising a fine gesture sensed by the EMG sensor and the second tier comprising a gross gesture sensed by the IMU sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to and claims the priority benefit of U.S. Provisional Patent Application Ser. No. 62/362,011, filed Jul. 13, 2016, the contents of which are hereby incorporated by reference in their entirety into this disclosure. 
     
    
     TECHNICAL FIELD 
       [0002]    The present application relates to orthotics, and more specifically, to a motor-activated wrist orthotic to assist Individuals with Cervical Spinal Cord Injuries with activities of daily living. 
       BACKGROUND 
       [0003]    There are approximately 12,500 new cases of Spinal cord injuries (SCI) every year in the United States alone. 53.9% of SCI are in the cervical region (C1-C7) and approximately 44% of these individuals have injuries in the C3-C6 region of the spinal cord (NSCISC, 2014). Daily manual activities such as unlocking doors with keys, holding utensils, writing, typing, using pointing devices, and swiping credit cards are extremely difficult for individuals with mid-cervical SCIs due to paralysis in the hand muscles preventing grasping and releasing and paralysis or weakness of wrist flexors and extensors. In order to stabilize a flaccid wrist, wrist orthoses or splints can be used to maintain the normal position of the hand and wrist. Wrist orthotics have often been used in rehabilitation of individuals with SCI to allow for the correct positioning of joints in the wrist, in order to maintain optimal muscle tone and structure. Tenodesis splints can be used for specific tasks such as assisting in picking up small objects by providing support to the thumb and forefinger. However, the limited motion of wrist braces for quadriplegics without the ability to flex or extend their wrists principally provides support. With the addition of a pocket in the palm strap, mid-cervical quadriplegics are able to insert dining utensils, pencils, pens, toothbrushes, or other tools to accomplish certain activities of daily living (ADL) independently. 
         [0004]    For individuals with mid-level SCI (i.e. C4-05), common devices include surface Functional Electrical Stimulation (FES) systems in the form of a forearm sleeve which are applied during early rehabilitation to control voluntary wrist extension for grasping and flexion. Alternatively, several electromechanical exoskeletons have been constructed to provide basic support with hard metal hinges as manipulators. Most current systems assist individuals with SCIs through mechanical actuators or ratchet systems activated by existing functional muscles. The drawbacks of these devices are that they are bulky and cause fatigue to the individual. Common ways to control actuators on these systems include speech recognition and gesture recognition. Gesture recognition is often achieved through acceleration sensors or electromyography (EMG) signals. Unfortunately, EMG and accelerometer signals by themselves tend to be very noisy and can often lead to false positives. While improvements in speech recognition technology provide accurate control of actions during steady state, performance is significantly reduced in noisy environments. Therefore, improvements are needed in the field. 
       SUMMARY 
       [0005]    According to one aspect, the present disclosure provides a wearable multifunctional wrist orthotic (MFWO) which is activated by the user&#39;s limited motor function including EMG signals from the pronator teris (wrist muscle) and customized switch activation methods and concurrently performs distinct functions based on the recognition of different individualized gestures through an Inertial Measurement Unit (IMU). The microcontroller unit may be configured to perform two-tiered gesture recognition. The first tier comprises a fine gesture sensed by the EMG sensor and the second tier comprises a gross gesture sensed by the IMU sensor. 
         [0006]    According to another aspect, a wrist orthotic is provided, comprising a rigid housing formed to fit around a portion of a forearm, wrist, and a portion of a hand of a user, a plurality of flexible straps for securing the housing to the user, an electromyography (EMG) sensor mounted to the housing and having at least two electrodes for attachment to the wrist of the user, an interial measurement unit (IMU) mounted to the housing, a microcontroller unit mounted to the housing and connected to the IMU, and a power supply unit mounted to the housing. The microcontroller may operate a device connected to the orthotic, such as an actuatable device, in response to recognized gestures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In the following description and drawings, identical reference numerals have been used, where possible, to designate identical features that are common to the drawings. 
           [0008]      FIG. 1  is a diagram showing a motor-activated wrist orthotic being worn by a user according to one embodiment. 
           [0009]      FIG. 2  is a rigid housing for the wrist orthotic of  FIG. 1  according to one embodiment. 
           [0010]      FIG. 3  is a system diagram showing the control components of the orthotic of  FIG. 1 . 
           [0011]      FIG. 4  is a diagram illustrating four gross gestures. 
       
    
    
       [0012]    The attached drawings are for purposes of illustration and are not necessarily to scale 
       DETAILED DESCRIPTION 
       [0013]    In the following description, some aspects will be described in terms that would ordinarily be implemented as software programs. Those skilled in the art will readily recognize that the equivalent of such software can also be constructed in hardware, firmware, or micro-code. Because data-manipulation algorithms and systems are well known, the present description will be directed in particular to algorithms and systems forming part of, or cooperating more directly with, systems and methods described herein. Other aspects of such algorithms and systems, and hardware or software for producing and otherwise processing the signals involved therewith, not specifically shown or described herein, are selected from such systems, algorithms, components, and elements known in the art. Given the systems and methods as described herein, software not specifically shown, suggested, or described herein that is useful for implementation of any aspect is conventional and within the ordinary skill in such arts. 
         [0014]      FIG. 1  shows a wrist orthotic  100  according to one embodiment. The wrist orthotic  100  includes an elongated rigid housing  102  (a further embodiment of the housing  102  shown in  FIG. 2 ) formed to fit around a portion of a forearm and wrist of a user, and may optionally extend around a portion of the user&#39;s hand. The housing  102  may be formed from plastic or other suitable material to provide stability and support to the user&#39;s wrist. A plurality of flexible attachment straps  104  are attached to the housing  102  for securing the housing to the user as shown in  FIG. 1 . The orthotic  100  is designed to provide comfortable support and adheres to the design of current orthotics by including a wrap-around framework to support the sides of the hand to secure the correct positioning. 
         [0015]    As shown in  FIG. 1 , and further in the system diagram  300  of  FIG. 3 , the wrist orthotic  100  includes an electromyography (EMG) sensor  106  mounted to the housing  102  and having electrodes  108  which attach to the surface of the user&#39;s arm and an intertial measurement unit (IMU)  110 . The EMG sensor  106  and IMU  108  are connected to a microcontroller unit  112  (e.g., a Arduino® Mini) which receives output signals from the EMG sensor  106  and IMU  110  for processing and gesture recognition. Voltage booster  113  may be provided to increase the output voltage of the battery, sensors  106   114  or the microcontroller  112  as needed. The orthotic  100  may also include one or more actuators, such as a servo motor which manipulates an arm holding a key/card or a laser pointer. The sensors and microcontroller are powered by battery  114  (e.g., a recharable lithium ion or nicad battery). Buzzer  116  may be optionally included to provide auditory feedback to the user. Laser pointer  118  may also be optionally provided as shown and connected to the microcontroller  112 . The orthotic  100  is designed to be lightweight (on the order of 300 grams), presenting an insignificant load to users and providing significant structural improvement over the commercially available options. 
         [0016]    The wrist orthotic of  FIG. 1  may be used to perform gesture recognition based on input from an EMG sensor  106  or touch-activated switch and IMU  110 . To minimize the occurrence of false positives, a two-tier gesture recognition approach is implemented to control the system. The first tier is based on input received from the EMG sensor  106  or touch-activated sensor which detects a fine gesture allowing the activation of the second tier. The second tier is based on input from the IMU  110  which detects one of four or more gross gestures to perform the desired task as shown in Table 1 below. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Gesture 
                 Motion 
               
               
                   
                   
               
             
             
               
                   
                 In-Out 
                 Moving hand toward body (In) then 
               
               
                   
                   
                 away from body (Out) 
               
               
                   
                 Out-In 
                 Moving hand away from body (Out) 
               
               
                   
                   
                 then toward body (In) 
               
               
                   
                 In-Hold 
                 Moving hand toward body (In) and 
               
               
                   
                   
                 holding position (Hold) 
               
               
                   
                 Out-Hold 
                 Moving hand away from body (Out) 
               
               
                   
                   
                 and holding position (Hold) 
               
               
                   
                   
               
             
          
         
       
     
         [0017]    The EMG sensor  106  may comprise a light-weight sensor which measures action potentials from adhesive surface electrodes placed on top of the pronator teris (wrist muscle) of the user. The sensor  106  identifies a pattern of rapid supination-pronation of the wrist by the orthotic wearer, which then allows for appropriate activation of the IMU  110  during a preset time period. A touch-activated sensor may comprise a switch which is activated by contacting another surface in a specific position or providing close proximity to other body parts. To improve the accuracy of the gesture recognition, a dynamic time warping (DTW) based machine learning process is implemented by the microcontroller  112  in certain embodiments. The DTW process two time dependent sequences and identifies the similarities in them. In certain embodiments, after sensing a fine gesture from the EMG sensor  106 , the IMU  110  recognizes four distinct gross gestures—In-Out, Out-In, In-Hold and Out-Hold, as shown in  FIG. 4 . These gestures were chosen for their comfort and ease of execution by individuals with cervical spinal cord injuries. Each of the gestures allows the control of one of the actuators (laser/servo) of the wrist orthotic. It shall be understood that more or less than four gross gestures may be recognized by the system  100 . 
         [0018]    The microcontroller  112 , sensors  106  and  110 , and other components recited herein may include one or more computer processors and memory which are communicatively connected and programmed to perform the data processing and control functionality recited herein. The program code includes computer program instructions that can be loaded into the processor, and that, when loaded into processor cause functions, acts, or operational steps of various aspects herein to be performed by the processor. Computer program code for carrying out operations for various aspects described herein can be written in any combination of one or more programming language(s), and can be loaded into memory for execution. The processors and memory may further be communicatively connected to external devices via a wired or wireless computer network for sending and receiving data. 
         [0019]    The invention is inclusive of combinations of the aspects described herein. References to “a particular aspect” and the like refer to features that are present in at least one aspect of the invention. Separate references to “an aspect” (or “embodiment”) or “particular aspects” or the like do not necessarily refer to the same aspect or aspects; however, such aspects are not mutually exclusive, unless so indicated or as are readily apparent to one of skill in the art. The use of singular or plural in referring to “method” or “methods” and the like is not limiting. The word “or” is used in this disclosure in a non-exclusive sense, unless otherwise explicitly noted. 
         [0020]    The invention has been described in detail with particular reference to certain preferred aspects thereof, but it will be understood that variations, combinations, and modifications can be effected by a person of ordinary skill in the art within the spirit and scope of the invention.