Patent Publication Number: US-10758394-B2

Title: Powered orthotic device and method of using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of U.S. Provisional Patent Application No. 62/175,765 filed Jun. 15, 2015. The disclosure of this provisional application is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure generally relates to orthotic devices and, more particularly, the disclosure relates to powered orthotic devices and methods of using the same for rehabilitation or functional aids. 
     BACKGROUND 
     Stroke, brain injury, and other neuromuscular trauma survivors are often left with hemiparesis, or severe weakness in certain parts of the body. The result can be impaired or lost function in one or more limbs. It has been shown that people can rehabilitate significantly from many of the impairments following such neurological traumas. Further, it has been shown that rehabilitation is much more effective, and motor patterns re-learned more quickly, if the rehabilitative exercise regime includes the execution of familiar and functional tasks. Following neuromuscular trauma, however, the control or strength in the afflicted limb or limbs may be so severely diminished that the patient may have difficulty (or be unable) performing constructive, functional rehabilitation exercises without assistance. 
     SUMMARY OF THE EMBODIMENTS 
     One embodiment of the invention includes a powered orthotic device for use with a limb having at least two joints. The device includes a brace system including at least two brace sub-assemblies. The first brace sub-assembly is operative with respect to a first one of the joints and a second brace sub-assembly is operative with respect to a second one of the joints. The first brace sub-assembly includes a first section and a second section, and the first section and the second section are configured for relative motion with respect to one another about the first one of the joints. The first brace sub-assembly is configured to removably attach its first section and its second section to a corresponding limb segment. The first brace sub-assembly includes a first powered actuator assembly that is configured to receive a first sensor signal from an electromyographic sensor, and that is also mechanically coupled to the first brace sub-assembly so as to apply a first force for driving the first and second sections of the first brace sub-assembly to move relative to one another. The first force based on the first sensor signal. 
     The second brace sub-assembly includes a first section and a second section, and the first section and the second section are configured for relative motion with respect to one another about the second one of the joints. The second brace sub-assembly is configured to removably attach its first section and its second section to a corresponding limb segment. The second powered actuator assembly is configured to receive a second sensor signal from a sensor selected from a group consisting of an electromyographic sensor, an inertial measurement unit, and combinations thereof. The second powered actuator assembly is also configured to be mechanically coupled to the second brace sub-assembly so as to apply a second force for driving the first and second sections of the second brace sub-assembly to move relative to one another. The second force is based on the first sensor signal or the second sensor signal. The brace system and the first and second actuator assemblies form a wearable component. 
     In some embodiments, the first brace sub-assembly includes the electromyographic sensor. In various embodiments, the second brace sub-assembly includes the sensor. The first brace sub-assembly may include an inertial measurement unit that outputs a third sensor signal, and the first force may be based on the first sensor signal and the third sensor signal. 
     In some embodiments, the second section of the first brace sub-assembly and the first section of the second brace sub-assembly may be the same section. In some of these embodiments, the first brace sub-assembly may be configured to removably attach its second section to a forearm, and the second brace sub-assembly may be configured to removably attach its first section to a forearm and its second section to a hand. The first force may be based additionally on the second sensor signal. The second force may be based on the first and second sensor signals. 
     The second actuator assembly may be configured to be positioned along the second brace sub-assembly and proximate to the second one of the joints. The second actuator assembly may be configured to be positioned on the second brace sub-assembly such that the second actuator assembly is positioned remotely from the second one of the joints when the device is removably attached to a user. The first actuator assembly may include a motor in a housing and a drive assembly coupled to the motor as well as the first and second sections of the first brace sub-assembly. The motor may be positioned proximate to a juncture between the first and second sections of the first brace sub-assembly. The juncture may be proximate to an elbow or a wrist when the first brace sub-assembly is configured to be removably attached to a forearm. 
     The second actuator assembly may include a motor in a housing and a drive assembly coupled to the motor as well as the first and second sections of the second brace sub-assembly. The motor may be positioned proximate to a juncture between the first and second sections of the second brace sub-assembly. The juncture may be proximate to a finger joint when the second brace sub-assembly is configured to be removably attached to a hand. 
     The second actuator assembly may be a linear actuator assembly or a rotary actuator assembly. The second actuator assembly may be a cable-based actuator assembly or a tendon-based actuator assembly. The first actuator assembly and the second actuator assembly may communicate regarding the first force applied to the first brace sub-assembly and the second force applied to the second brace sub-assembly. 
     In some embodiments, the device includes a controller system in communication with the first and second brace sub-assemblies. The controller system may include a processing system that receives the first and second sensor signals and generates output signals to the first and second actuator assemblies. The controller system may include a user interface through which a user interacts with the device. The controller system may automatically self-adjust one or more parameters selected from the group consisting of brace strength, system gains, system sensitivities, virtual spring parameters, EMG threshold values, maximum and minimum torques, operational range of motion, damping parameters, user feedback modes, data logging parameters, and any combination thereof. The controller system may be coupled to the second brace sub-assembly via a cable or wireless system. The controller system may be coupled to the Internet, so that the device is able to communicate with a remotely located computing device. The controller system may include a data management system for storing data received from the device, from a user or both. The wearable component may include a battery coupled to the first and second powered actuator assemblies. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which: 
         FIG. 1  shows an isometric view of a powered orthotic device including a brace system with two brace sub-assemblies that are removably attached to a limb of a subject; 
         FIG. 2  shows the powered orthotic device of  FIG. 1 , as detached from the limb; 
         FIG. 3  shows an isometric view of a powered orthotic device including a brace system with two brace sub-assemblies that are removably attached to a limb of a subject; 
         FIG. 4  shows the powered orthotic device of  FIG. 3 , as detached from the limb; 
         FIGS. 5-7  show isometric views of a powered orthotic device including a brace system with two brace sub-assemblies that are removably attached to a limb of a subject, wherein the second brace sub-assembly further includes an inertial measurement unit; 
         FIGS. 8 and 9  show isometric views of a powered orthotic device including a brace system with two brace sub-assemblies that are removably attached to a limb of a subject, wherein the first brace sub-assembly further includes an inertial measurement unit; 
         FIG. 10  shows an isometric view of part of a second brace sub-assembly of a powered orthotic device, with the first section of the second brace sub-assembly removably attached to a limb segment; 
         FIG. 11  shows an isometric view of a second brace sub-assembly of a powered orthotic device, with the first and second sections of the second brace sub-assembly removably attached to corresponding limb segments; 
         FIG. 12  shows an isometric view of a second brace sub-assembly, as detached from any limbs; 
         FIGS. 13-15  show exploded views of the actuator assembly of the second brace sub-assembly; 
         FIGS. 16 and 17  show elevation and isometric views, respectively, of the first brace sub-assembly; 
         FIG. 18  shows an exemplary electromyographic sensor for use with the first and second brace sub-assemblies; 
         FIG. 19  shows an exemplary control algorithm according to exemplary embodiments of the present invention; 
         FIG. 20  shows a graph of EMG signal vs. output signal according to exemplary embodiments of the present invention; 
         FIG. 21-24  show different graphs of EMG signal vs. output signal according to various exemplary embodiments of the present invention; 
         FIG. 25  shows a graph of other parameters vs. output signal according to exemplary embodiments of the present invention; 
         FIG. 26  shows a graph of time or temperature parameters vs. output signal according to exemplary embodiments of the present invention; 
         FIG. 27  shows a graph of EMG signal vs. output signal according to exemplary embodiments of the present invention; 
         FIG. 28  shows a graph of position vs. output signal according to exemplary embodiments of the present invention; and 
         FIG. 29  shows a graph of temperature vs. output signal and a control algorithm according to exemplary embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Definitions. As used in this description and the accompanying claims, the following terms shall have the meanings indicated, unless the context otherwise requires: 
     An “orthotic device” is a support or brace for weak or ineffective joints or muscles. An orthotic device is worn over existing body parts to support and/or restore function to a weakened or malformed body part. 
     A “limb” is an arm or a leg, wherein a portion, up to the whole thereof, of the arm or leg optionally includes a prosthesis. 
     A “prosthesis” is an artificial device to replace a missing part of the body. 
     A “limb segment” is a portion of a limb. 
     A “joint” is a coupling between adjacent limb segments. 
     “User” is defined by context and refers to anyone who is interacting with the device at the moment. For example, user includes the patient or wearer of the device while the device is functioning, and a clinician, trained professional, or anyone else who is interacting with the device at the moment via the user interface. 
     People afflicted with neuromuscular conditions often exhibit diminished fine and gross motor skills. For example, even if a person retains symmetric control over a joint, the person may be left with reduced control over muscle groups on opposite sides of the joint. Not only may the person be incapable of achieving the full range of motion that the joint would normally permit, the person may also be incapable of controlling the joint so that the associated limb segments exert desired amounts of force on surrounding objects. For example, if the person wants to pinch an object between his or her index finger and thumb, the person must use at least the adductor pollicis, first dorsal interosseous, and flexor pollicis brevis muscles to position the fingers around the object and then grasp accordingly. When the person cannot move his or her fingers to the proper positions, or apply the required force, the person will be unable to hold objects. 
     In another example, a person may be capable of only asymmetric control of a particular joint. In these situations, the person may be capable of flexing or extending the joint, but not both. The user may be able to control the muscle group responsible for flexion about the joint, but his or her control over the muscle group responsible for extension may be impaired. Similarly, the opposite may be true, e.g., the user may have control in the extension direction, but not the flexion direction. As an example, the task of reaching by extending an arm may require relaxing the flexors (e.g., biceps, brachioradialis) and allowing tension in the extensors (e.g., triceps) to dominate. However, if a person cannot exert his or her triceps or release a hyperactive bicep, the person will fail to complete the task. 
     Embodiments of the present invention enable their users to achieve more natural gross and fine motion. When users wear the powered orthotic devices described herein, the devices enhance the users&#39; functional capacities. In particular, various embodiments of the present invention may use control algorithms that mimic, in real time, the natural patterns of motion and force about multiple joints, even in the absence of the user&#39;s impaired ability to control one or more of the major muscle groups that effect force and motion about the joint. The powered orthotic devices each include a brace system with at least two brace sub-assemblies, each of which attaches to two of the user&#39;s limb segments and operates with respect to a different joint. At least one of the brace sub-assemblies includes at least one electromyographic (EMG) sensor. When the user removably attaches the device to his or her limb, at least one EMG sensor becomes coupled to one of the user&#39;s muscle groups. As the user attempts to move a limb, the EMG sensor detects activity in the user&#39;s muscles. Based on the outputs of at least one sensor, the device applies a torque to one, or both, of the brace sub-assemblies to assist the user&#39;s motion. 
     In some embodiments, at least one of the brace sub-assemblies of the orthotic device includes an inertial measurement unit (IMU). The orthotic device may determine the torque to apply to at least one of the brace sub-assemblies based on the outputs of the IMU and EMG sensor(s). As a result, the combination of the IMU and EMG sensor(s) may enable the orthotic device to provide more refined assistance to the user than devices that rely solely on the EMG sensor(s). 
     Exemplary Embodiments of the Powered Orthotic Device 
       FIGS. 1 and 3  show isometric views of a powered orthotic device  100  including a brace system with two brace sub-assemblies  110 ,  150  that are removably attached to a limb of a subject, and  FIGS. 2 and 4  show the device  100 , from the respective views, as detached from the limb. Both brace sub-assemblies  110 ,  150  may be wearable components that are configured to be removably attached to limb segments of a user. 
     In this embodiment, the second brace sub-assembly  110  of the device  100  is configured to be coupled to the hand and forearm of a user. To removably attach the second brace sub-assembly  110  to the user, the user inserts a wrist into the cuff  111  and positions the back of his or her hand under a molding  112  that supports an actuator assembly  130 . The user also inserts one or more fingers into a splint  113  of a first section  114  of the second brace sub-assembly  110 , as well as a thumb into a splint  115  of a second section  116 . In some embodiments, a strap  124  may be attached to the second brace sub-assembly  110 , and to further secure the second brace sub-assembly  110  to the user&#39;s limb, the user may wrap the strap  124  around his or her forearm, and clasp the ends of the strap  124  together. In this embodiment, in which two EMG sensors  120 ,  121  are affixed to the strap  124 , attaching the second brace sub-assembly  110  to the user couples the EMG sensors  120 ,  121  to at least one muscle group in the user&#39;s forearm. 
     The actuator assembly  130  includes a processor, and a motor and drive assembly coupled to the first and section sections  114 ,  116 . The actuator assembly  130  receives output from the EMG sensors  120 ,  121 , and based on at least these signals, the actuator assembly  130  determines the torque to apply to the first and second sections  114 ,  116  of the second brace sub-assembly  110  so that the sections  114 ,  116  move relative to one another. The processor outputs a signal to the motor and drive assembly to move the sections  114 ,  116  accordingly. 
     For example, one side of the actuator assembly  130  may connect to a beam  117  attached to the splint  113  of the first section  114 , and the other side may connect to a hinge  118  attached to the splint  115  of the second section  116 . By driving the beam  117 , the hinge  118 , or both, by extension, the actuator assembly  130  drives the first and/or second sections  114 ,  116  to move relative to one another. Since the splints  113 ,  115  engage the user&#39;s finger(s) and thumb, the actuator assembly  130  supplements the user&#39;s control over these digits to achieve fine motion via, for example, radial and ulnar deviation. 
     The first brace sub-assembly  150  of the device  100  is configured to be coupled to the forearm and upper arm of a user. To attach the first brace sub-assembly  150  to the user&#39;s limb, the user may wrap a strap  157  attached to the first section  158  of the first brace sub-assembly  150  around the user&#39;s upper arm to secure the first section  158  to the user&#39;s limb. In some embodiments, the user may place his or her forearm into a curved recess of the second section  155  of the first brace sub-assembly  150 . In further embodiments, a strap  124  is attached to the second section  155  of the first brace sub-assembly  150 , and the user may further secure the first brace sub-assembly  150  to the user&#39;s forearm by wrapping the strap  124  around his or her forearm and clasping the ends of the strap  124  together. In various embodiments, the second section  155  may include one or more additional straps to wrap around the user&#39;s forearm. 
     As with the second brace sub-assembly  110 , the strap  157  for the first brace sub-assembly  150  includes one or more EMG sensors  160 ,  161 . When the user wraps the strap  157  around his or her upper arm, the EMG sensors  160 ,  161  become coupled to at least one muscle group in the user&#39;s upper arm. Further, the first brace sub-assembly  150  includes a powered actuator assembly  165  inside a housing  166 . The actuator assembly includes a processor (not shown), and receives output from the one or more EMG sensors  160 ,  161 . Based on at least these signals, the actuator assembly  165  drives the first and second sections  158 ,  155  of the first brace sub-assembly  150  to move relative to one another. By controlling the flexion and extension between the user&#39;s forearm and upper arm, the actuator assembly supplements the user&#39;s control over these limb segments to achieve gross motion for the limb. 
     The first brace sub-assembly  150  includes a user interface  170  on the housing  166  through which a user interacts with the device  100 . In this embodiment, the user interface  170  includes a power button for turning the device on and off and a mode button for selecting the device&#39;s  100  mode of operation. In various embodiments, the user interface  170  may include other inputs for user input and feedback, such as single or multiple knobs, buttons, switches, touch sensors, touch screens, or combinations thereof. The user interface  170  may include outputs, such as audio and/or visual devices, e.g., speakers, lights, LEDs, tactile sensors or transmitters, visual displays, such as LCD screens. Additionally, the first brace sub-assembly  150  may include a data storage and management system (not shown) within the same housing  166  that covers the actuator assembly  165 . 
     In various embodiments, the housing  166  on the first brace sub-assembly  150  may include a controller system  167  that interacts with the actuator assemblies  130 ,  165  of the first and second brace sub-assemblies  150 ,  110 . In some embodiments, each brace sub-assembly  150 ,  110  includes a processor that receives outputs from its respective EMG sensors  160 ,  161 , or  120 ,  121 , processes the outputs according to control algorithms, and drives its respective actuator assembly  165  or  130  accordingly. However, in further embodiments, the EMG sensors  120 ,  121 ,  160 , and  161  may all send their outputs to the controller system  167 . Based on these outputs, the processing system in the controller system  167  may determine the torques to apply to the first and second sections of each brace sub-assembly  150 ,  110 . Moreover, in some embodiments, the processing system may determine the torque to apply to the second brace sub-assembly  110  based on signals from EMG sensors  160 ,  161  in the first brace sub-assembly  150 , as well as the EMG sensors  120 ,  121  and/or one or more inertial measurement units  180  (as described in more detail below in  FIGS. 5-7 ) in its own second brace sub-assembly  110 . Likewise, the processing system may determine the torque to apply to the first brace sub-assembly  150  based on signals from EMG sensors  160 , and  161  as well as the EMG sensors  120 ,  121  and/or the inertial measurement units  180  in both the first and second brace sub-assemblies  150 ,  110 . 
     Turning now to  FIGS. 5-9 , the figures show isometric views of a powered orthotic device  100  that includes the features described with respect to  FIGS. 1-4 , and also includes at least one inertial measurement unit (IMU)  180 . In the embodiment depicted in  FIG. 5 , the IMU  180  is attached to the molding  12  of the second brace sub-assembly  110  and is thus configured to be coupled to a user&#39;s hand. The IMU  180  may send its output to the actuator assembly  130  of the second brace sub-assembly  110 . In the embodiments depicted in  FIGS. 6 and 7 , the IMU  180  is attached to the strap  124  configured to be wrapped around the user&#39;s forearm, and the IMU  180  may send its output to the actuator assembly  130  of the second brace sub-assembly  110 . In any of these embodiments, the actuator assembly  130  determines the torque for driving the first and second sections  114 ,  116  based solely on the output of the IMU  180 , and in other, additional embodiments, the actuator assembly  130  determines the torque based on outputs from both the IMU  180  and the EMG sensors  120 ,  121  of the strap  124 . 
     In the embodiments depicted in  FIGS. 8 and 9 , the IMU  180  attaches to the strap  157  of the first brace sub-assembly  150 , and the strap  157  is configured to be wrapped around the user&#39;s upper arm. In this embodiment, the output of the IMU  180  is still used to drive the second brace sub-assembly  110 . In particular, the IMU  180  may send its output to the actuator assembly  130  in the housing  131  of the second brace sub-assembly  110 . As with the embodiments of  FIGS. 5-7 , the actuator assembly  130  may determine the torque for driving the first and second sections  114 ,  116  based solely on the output of the IMU  180  or a combination of outputs from the IMU  180  and EMG sensors  120 ,  121  attached to the strap  124 . 
     Turning now to  FIG. 10 , the figure shows an isometric view of part of the second brace sub-assembly  110  of a powered orthotic device  100 . This figure depicts the molding  112 , the actuator assembly  130 , and the first section  114  of the second brace sub-assembly  110 . As this embodiment drives the first section  114  to move, the embodiment may be used for persons who have diminished control over the joints in their index and second fingers, but who retain control over the joints in their thumbs. 
     Further, this embodiment includes an adjustable splint  113 . Both the splint  113  and the beam  117  may include two or more holes, and a user may align different holes in the splint  113  and the beam  117  to position the splint  113  on the user&#39;s fingers. The user may secure the splint  113  by inserting a screw or other fastener into the aligned holes, although other mechanisms of securing the components may be used. 
     By changing the position of the splint  113  on the user&#39;s fingers, the second brace sub-assembly  110  may create different ranges of motion for the user. Moreover, by allowing the splint  113  to be detached, the user  113  may apply different splints  113  to the second brace sub-assembly  110 , as desired. For example, the user may select a splint  113  whose size matches the user&#39;s own fingers. Additionally, the user may choose a splint  113  that engages either the user&#39;s index finger alone, or the user&#39;s index finger with one or more additional fingers. 
       FIG. 11  shows an isometric view of the second brace sub-assembly  110  with both the first and second sections  114 ,  116  ( FIG. 12  depicts a second brace sub-assembly  110  that includes the features of the second brace sub-assembly  110  of  FIG. 11 , as well as a cuff  111 , but detached from the user&#39;s hand). This second brace sub-assembly  110  includes the components of the first section  114  described in reference to  FIG. 10 . Moreover, this figure depicts a splint  115  configured to engage a user&#39;s thumb, as well as a hinge  118  attached to the splint  115 . The hinge  118  is also attached to the actuator assembly  130 , which drives the hinge  118  to move the user&#39;s thumb via the second section  116 . As with the first section  114 , the splint  115  and the hinge  118  may include multiple holes for aligning the former on the latter at different positions, or for changing splints  115  according to the needs of the user. 
     The second section  116  may also include a beam  119  attached to the actuator assembly  130  and the hinge  118 . Although the actuator assembly  130  does not drive the beam  119 , the positions where the beam  119  attaches to the actuator assembly  130  and the hinge  118  enable the beam  119  to modify the movement of the hinge  118 , and thus, the position of the splint  115 . Further, the beam  119  may be adjustably attached to different positions on the hinge  118 , and from each position, the beam  119  may modify the movement of the hinge  118  and splint  115  in a different manner. As a result, the second brace sub-assembly  110  may be configured to mimic different natural motions of the hand, depending on the setting of the beam  119 . In this embodiment, the hinge  118  includes three notches to which the beam  119  may be attached. The beam  119  may have a hole at one end, and the user may align the hole with one of the notches and insert a screw to secure the beam  119  to the hinge  118 . However, other embodiments of the beam  119  and hinge  118  may use alternate means of fastening (e.g., the beam  119  may include a hook to insert into a notch). 
     Although the actuator assembly  130  may drive the hinge  118  and not the beam  119 , in various embodiments, the actuator assembly  130  may drive solely the beam  119 . Alternatively, the actuator assembly  130  may drive both the hinge  118  and the beam  119 . 
       FIGS. 13-15  show exploded views of the actuator assembly  130  of the second brace sub-assembly  110 .  FIG. 13  depicts the entire actuator assembly  130 ,  FIG. 14  depicts components of the assembly  130  positioned on one side of the hinge  118 , and  FIG. 15  depicts components of the assembly  130  positioned on the opposite side of the hinge  118 . 
       FIGS. 16 and 17  show elevation and isometric views, respectively, of the first brace sub-assembly  150 . The first brace sub-assembly  150  includes the first and second sections  158 ,  155  and the actuator assembly  165  that drives the sections  158 ,  155  to move relative to one another. The first brace sub-assembly  150  also includes the strap  157  for removably attaching the first brace sub-assembly  150  to the user&#39;s upper arm. In this embodiment, the strap  124  with EMG sensors  120 ,  121  that send their outputs to the second brace sub-assembly  110  is attached to the second section  155  of the first brace sub-assembly  150 . Thus, the user may use straps  124  and  157  to secure the first brace sub-assembly  150  to the user&#39;s forearm and upper arm, while the second brace sub-assembly  110  may be removably attached to the user&#39;s limb via the cuff  111 . 
       FIG. 18  shows an exemplary electromyographic (EMG) sensor  1701  for use with the first and second brace sub-assemblies  150 ,  110 . This EMG sensor includes a three-button array  1705 , as well as a cable  1710  that receives output from the array  1705  and transmits the signals to another component. 
     Exemplary Embodiments of the Control Algorithm for Operating the Powered Orthotic Device 
       FIGS. 19-29  show various exemplary control algorithms for driving the first or second brace sub-assemblies  150 ,  110 .  FIG. 19  shows an exemplary control algorithm and the variables upon which the algorithm is based that may be used in an orthotic device  100  in accordance with embodiments of the present invention. The control output signal is the command that is sent to the actuator assembly  130 ,  165 .  FIG. 19  depicts ways in which the various control output signal relationships may be combined to provide one command signal which commands the actuator assembly  130 ,  165 . As shown, a simple arithmetic combination may be used ( 1 ′), in which the output signals from the various relationships (some of which are shown in  FIGS. 21-27  below) are added, subtracted, multiplied, divided, or any combination (linear or non-linear ( 2 ′)) thereof, to generate the command signal to the actuator assembly  130 ,  165 . A conditional relationship may be used ( 3 ′,  4 ′), in which the algorithm for combining the various output signals is dependent on certain conditions being met. Boolean combinations of such conditional relationships ( 4 ′) may also be used. Also, any combination of the above mentioned techniques may also be used to combine the various output signals to generate one command signal. 
       FIG. 20  shows a graph depicting features of a control algorithm, namely the relationship between the control output signal and the measured EMG signal from a user&#39;s muscle (EMG 1 ). In  FIGS. 20-24 , the axes have the following meaning: positive output signal correlates to actuator torque, velocity or motion in a first direction about the joint; negative output signal correlates to actuator torque, velocity or motion in a second direction about the joint; and EMG 1  is the filtered absolute value of the EMG signal in the first direction. In  FIG. 20 , the y-intercept ( 1 ′) is the maximum output signal in the second direction. This is the output signal that the system will give when the value of EMG 1  is zero. The correlation between the output signal and EMG 1  may be linear or non-linear, and may be considered in two separate regions: the first direction ( 4 ′,  5 ′,  6 ′), and the second direction ( 2 ′). The zero-crossing point ( 3 ′) is the value of EMG 1  at which the output signal changes direction. There may be break points ( 4 ′) in any region, at which the slope of the relationship changes, or at which the relationship may change from linear to non-linear. There may be saturation limits ( 6 ′) where the slope of the relationship goes to zero, meaning the output signal reaches a minimum or maximum “floor” or “ceiling” which it will not surpass, regardless of the value of EMG 1 . This may serve as a safety mechanism to prevent excessive torques in the case of abnormally high spikes in muscle activity. 
       FIG. 21  shows a graph depicting features of another control algorithm. In this scenario, there may be output signal saturation in the second direction ( 1 ′), as well as in the first direction ( 4 ′).  FIG. 21  also depicts a non-linear relationship between EMG 1  and output signal in both the first ( 2 ′) and second ( 3 ′) directions, with a break point coinciding with the zero-crossing. 
       FIG. 22  shows a graph depicting features of another control algorithm. As shown, the relationship between output signal and EMG 1  is not necessarily monotonic, but may have inflection points, where the slope changes from decreasing to increasing ( 1 ′), or vice versa ( 2 ′). For example, the maximum absolute output signal value for each direction may be reached before the output signal saturates, or before EMG 1  reaches zero. 
       FIG. 23  shows a graph depicting features of another control algorithm. As shown, there may be regions of zero slope ( 1 ′), regions of infinite slope ( 2 ′), or discontinuities ( 3 ′) in the relationship between output signal and EMG 1 . For example, the output signal may be constant for low values of EMG 1  and then the value may jump to zero at a certain value of EMG 1 . Also, the output signal may not change direction (and cause torque in the first direction) until the value of EMG 1  reaches yet another, higher value. This may be thought of as a “dead band” ( 3 ′), which may act to minimize the sensitivity of the output signal to small perturbations in EMG 1  about some nominal value. 
       FIG. 24  shows a graph depicting features of another control algorithm. As shown, there may be hysteresis in the relationship between output signal and EMG 1 . The relationship may follow a certain path if EMG 1  is increasing, and may follow a different path if EMG 1  is decreasing. For example, the output signal may follow curve ( 1 ′) if EMG 1  is increasing, and the output signal may follow curve ( 2 ′) if EMG 1  is decreasing. Alternatively, the output signal may follow a hysteretic path ( 3 ′) which departs directly from the “EMG 1  increasing” or “EMG 1  decreasing” curve, when EMG 1  changes direction (rather than making a discontinuous jump from one curve to another, as in ( 2 ′)). 
       FIG. 25  shows a graph depicting features of another control algorithm, showing the potential relationship between a control output signal and other measured parameters such as joint position, joint velocity, current and various measured forces or torques. As shown, the relationships may be linear ( 1 ′) or non-linear ( 2 ′,  3 ′), increasing or decreasing ( 3 ′) or both. The relationship may be continuous or discontinuous ( 1 ′), and may have positive and negative components. The relationship may also be asymptotic, and may have saturation limits ( 2 ′). 
       FIG. 26  shows a graph depicting features of another control algorithm, showing the potential relationship between a control output signal and other measured or unmeasured parameters such as temperature or time. As shown, the relationship may be linear or non-linear ( 1 ′,  2 ′,  3 ′), increasing or decreasing ( 3 ′) or both. The relationship may be continuous or discontinuous ( 1 ′), and may have positive and negative components. The relationship may also be asymptotic, and may have saturation limits ( 2 ′). They may have regions of zero slope, and regions of infinite slope ( 1 ′). 
       FIGS. 27-29  show graphs depicting features of a control algorithm. The equation for the command output to the actuator assembly  130 ,  165  is shown in  FIG. 29 . As shown, the slope of the line ( 1 ′), and the values of the constants (A, B, C, D, E, F, G) are adjustable via the user interface. 
     Any of the control algorithms described herein may be adjusted based on the output of the IMU  180 . For example, when the IMU  180  detects that the user has lowered his or her forearm, the device  100  may operate according to the default control algorithm(s). However, once the user raises his or her forearm, the device  100  may change one or more slopes in the control algorithm(s). Since the user may wish to maintain his or her forearm in an upright position, but have difficulty doing so as a result of their impaired muscle control, the device  100  may require stronger signals from the EMG sensors  120 ,  121  before the device  100  will lower the user&#39;s forearm. The device  100  may similarly increase slope(s) in the control algorithm(s) when the IMU  180  output indicates that the user has lifted his or her upper arm. 
     Other Features of or Used with, the Powered Orthotic Device 
     In the embodiments depicted in  FIGS. 1-15 , the first and second sections  114 ,  116  of the second brace sub-assembly  110  are configured to be removably detached to the user&#39;s fingers and thumb. Although these embodiments drive the second brace sub-assembly  110  to move the user&#39;s fingers and thumb to effect radial and ulnar deviation, in other embodiments, the first and second sections  114 ,  116  may be configured to be removably detached to other limb segments, or the same limb segment, so that the second brace sub-assembly  110  operates with respect to different joints and achieves different types of motion. 
     For example, the first section  114  may be configured to be attached to the user&#39;s hand, and the second section  116  may be configured to be attached to the user&#39;s forearm. In this manner, the second brace sub-assembly  110  may operate with respect to a joint in the user&#39;s wrist. Based on the EMG sensors  120 ,  121  and/or the IMU  180 , the actuator assembly may drive the first and second sections  114 ,  116  to move to effect flexion and extension in the user&#39;s wrist. 
     In another example, the first and second sections  114 ,  116  may be configured to be attached to the same limb segment, and the first section  114  may be configured to rotate relative to the second section  116 . For example, the cuff  111  shown in  FIG. 1  may be removably attachable to a user&#39;s wrist. An outer, second section  116  of the cuff  111  may be attached to the second section  155  of the first brace sub-assembly  150  in a fixed manner, and an inner, first section  114  may rotate relative to the outer, second section  116 . In this manner, the second brace sub-assembly  110  may operate with respect to a different joint in the user&#39;s wrist. In this embodiment, based on the EMG sensors  120 ,  121  and/or the IMU  180 , the actuator assembly may drive the first section  114  to rotate relative to the second section  116  to effect pronation and supination around the user&#39;s wrist. 
     In various embodiments, the orthotic device  100  may include multiple brace sub-assemblies, and each brace sub-assembly may operate with respect to a different joint on the user&#39;s limb. For example, a single device may include one brace sub-assembly that achieves flexion and extension between the user&#39;s upper arm and forearm, another brace sub-assembly that achieves flexion and extension between the user&#39;s forearm and hand, another brace sub-assembly that achieves pronation and supination around the user&#39;s wrist, and a final brace sub-assembly that achieves radial and ulnar deviation for a user&#39;s fingers. In these devices, brace sub-assemblies may share sections. For example, a single section may be removably attached to the user&#39;s forearm, but this section may belong to the brace sub-assembly achieving flexion and extension between the user&#39;s upper arm and forearm, and the brace sub-assembly achieving the same type of motion between the user&#39;s forearm and hand. 
     Embodiments depicted in the figures show cable systems coupling the controller system  167  to the first and/or second brace sub-assemblies  150 ,  110  using cables. However, the controller system  167  and first and/or second brace sub-assemblies  150 ,  110  may be configured to communicate via wireless systems. 
     Although the embodiments described herein include EMG sensors and/or IMUs attached to the straps  124  or  157 , in some embodiments, the orthotic device  100  may not include any sensors at all. Instead, EMG sensors, IMUs, or any other type of sensor may be implanted in a user, and the orthotic device  100  may include at least one receiver that receives signals from the implanted sensor. For example, a user may have an EMG sensor implanted in his or her finger, and signals from this implanted sensor may be transmitted to a receiver on the second brace sub-assembly  110 . In another example, a user may have an EMG sensor implanted in his or her forearm, and signals from this sensor may be transmitted to a receiver on either the first and/or second brace sub-assembly  150 ,  110 . In some embodiments, the orthotic device  100  may include both sensors configured to be coupled to the surface of limb segments and receivers that receive signals from implanted sensors in the user. For example, the orthotic device  100  may include an EMG sensor configured to be coupled to the user&#39;s forearm, as well as a receiver that receives signals from an EMG sensor implanted in the user&#39;s finger. 
     The orthotic device  100  may include other types of sensors, and the outputs from the sensors may be used to adjust the control algorithms described herein. Exemplary additional sensors may include kinematic sensors, RFID readers obtaining information related to environmental awareness, electroencephalographic sensors, electrocorticographical (e.g., intracranial electroencephalographical) sensors, on-nerve sensors (e.g., implantable cuff electrodes), peripheral nerve sensors, temperature sensors, humidity sensors, proximity sensors, contact sensors, and force or torque sensors. 
     Additionally, the controller system  167  of the orthotic device  100  may be configured to be coupled to the Internet so that the device  100  may communicate with remotely located computing devices. For example, the remotely located devices may include a data management system that stores data received from the orthotic device  100 , among other sources of data. In this manner, the orthotic device  100  may be configured to transmit data about the user&#39;s performance to other computing devices. 
     Moreover, to determine the force to apply to the first or second brace sub-assembly  150 ,  110 , the orthotic device  100  may receive data from other computing devices that collect data regarding the user. For example, the orthotic device  100  may receive data from applications running on the user&#39;s mobile computing devices (e.g., smartphones, smartwatches). In further examples, the orthotic device  100  may receive data from personal devices, such as activity trackers, devices with global positioning systems (GPS), or any other device that obtains information about the user&#39;s physical state or location. The orthotic device  100  may also receive data from remote data management systems. The data management system may transmit information regarding the user&#39;s own medical records and information gleaned from other patient records, and the controller system  167  may analyze this data, in conjunction with other data, to determine the force to apply to the first and/or second brace sub-assemblies  150 ,  110 . 
     In some embodiments, the orthotic device  100  includes a battery. The device  100  may be configured for wired or wireless charging for the battery. For example, the device  100  may include an interface in a housing configured to receive a cable that may be plugged into an outlet. The device  100  may include an inductive coil that receives an electromagnetic field from an inductive charger and converts the power back into electrical current to charge the battery. However, any other method for charging the battery, either through wired or wireless approaches, may be used. Moreover, the device  100  may include more than one battery. In various embodiments, all of the batteries may be wirelessly charged or charged through wires. In some embodiments, a subset of the batteries may be wirelessly charged, whereas the remaining batteries may be charged via wires. 
     In various embodiments, any of the actuator assemblies of the device  100  may be a linear actuator assembly or a rotary actuator assembly. 
     In some embodiments, the powered orthotic device  100  includes motion limits coupled to one of the drive assemblies in one of the actuator assemblies. The motion limits may be configured to limit a range of motion of the first and second sections of the first or second brace sub-assembly about one of the joints. The motion limits may be provided by mechanical stops, by software controlled by input from sensors, or both. 
     U.S. Pat. No. 8,585,620, entitled “Powered Orthotic Device and Method of Using Same” and issued Nov. 19, 2013, describes additional features that may be used in the orthotic device  100  described herein. Some features may be directly incorporated into the device  100 , whereas other features may be adapted to be used in the device  100 . The contents of the application are hereby incorporated by reference in their entirety. 
     The embodiments of the present invention described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims.