LEGGED MOBILITY EXOSKELTON DEVICE

Related Applications This application claims the benefit of U.S. Provisional Application No.

62/255,549 filed November 16, 2015, which is incorporated herein by reference.

Field of Invention

The present invention relates generally to fall mitigation safety methods, including detection, behavior, and recovery, for a legged mobility device or

"exoskeleton" device.

Background of the Invention

There are currently on the order of several hundred thousand spinal cord injured (SCI) individuals in the United States, with roughly 12,000 new injuries sustained each year at an average age of injury of 40.2 years. Of these,

approximately 44% (approximately 5300 cases per year) result in paraplegia. One of the most significant impairments resulting from paraplegia is the loss of mobility, particularly given the relatively young age at which such injuries occur. Surveys of users with paraplegia indicate that mobility concerns are among the most prevalent, and that chief among mobility desires is the ability to walk and stand. In addition to impaired mobility, the inability to stand and walk entails severe physiological effects, including muscular atrophy, loss of bone mineral content, frequent skin breakdown problems, increased incidence of urinary tract infection, muscle spasticity, impaired lymphatic and vascular circulation, impaired digestive operation, and reduced respiratory and cardiovascular capacities.

In an effort to restore some degree of legged mobility to individuals with paraplegia, several lower limb orthoses have been developed. The simplest form of such devices is passive orthotics with long-leg braces that incorporate a pair of ankle-foot orthoses (AFOs) to provide support at the ankles, which are coupled with leg braces that lock the knee joints in full extension. The hips are typically stabilized by the tension in the ligaments and musculature on the anterior aspect of the pelvis. Since almost all energy for movement is provided by the upper body, these passive orthoses require considerable upper body strength and a high level of physical exertion, and provide very slow walking speeds. The hip guidance orthosis (HGO), which is a variation on long-leg braces, incorporates hip joints that rigidly resist hip adduction and abduction, and rigid shoe plates that provide increased center of gravity elevation at toe-off, thus enabling a greater degree of forward progression per stride. Another variation on the long-leg orthosis, the reciprocating gait orthosis (RGO), incorporates a kinematic constraint that links hip flexion of one leg with hip extension of the other, typically by means of a push-pull cable assembly. As with other passive orthoses, the user leans forward against a stability aid (e.g., bracing crutches or a walker) while un-weighting the swing leg and utilizing gravity to provide hip extension of the stance leg. Since motion of the hip joints is reciprocally coupled through the reciprocating mechanism, the gravity-induced hip extension also provides contralateral hip flexion (of the swing leg), such that the stride length of gait is increased. One variation on the RGO incorporates a hydraulic-circuit-based variable coupling between the left and right hip joints. Experiments with this variation indicate improved hip kinematics with the modulated hydraulic coupling. To decrease the high level of exertion associated with passive orthoses, the use of powered orthoses has been under development, which incorporate actuators and drive motors associated with a power supply to assist with locomotion. These powered orthoses have been shown to increase gait speed and decrease

compensatory motions, relative to walking without powered assistance. One issue with both passive or powered orthoses is that injuries can occur in the event of falling. Depending upon the direction or nature of a fall, the locked or released state of portions of the orthoses can be determinative of the nature or extent of injury. The use of powered orthoses presents an opportunity for electronic control of the orthoses. There now exists, however, no methods that can adequately detect the precise nature of a fall in progress, and adjust the orthoses by locking and/or releasing different portions of the orthoses as may be warranted by a given stage of a fall in progress to mitigate potential injuries from falling. Examples of powered orthoses are known. WO/2010/044087, US 2010/0094188, and US 8,096,965 disclose a powered exoskeleton bracing system/exoskeleton bracing system. These prior art devices, however, have been insufficient for full protection and control in the event of falling. The conventional methods associated with these devices in particular do not generate alerts in response to falling or changing stance, although these conditions may be indicated. Instead, the safety features generate alerts that tend to be in response to a defective nature or state of the exoskeleton device or its components. Alerts, for example, may be provided as to such conditions as sensor fault(s), detection of "high" temperature(s), detection of battery charger (High Severity Alerts accompanied by Solid Red LEDs), detection of "medium" temperature(s), detection of "critical" battery levels (Medium Severity Alerts accompanied by Flashing Red LEDs), detection of low temperature(s), and detection of "low" battery levels (Low Severity Alerts accompanied by Flashing Yellow LEDs). Detection of High Severity Alerts in particular may result in a control response whereby actuation of the exoskeleton device is halted. Halting actuation, however, can be undesirable in the context of falling depending upon the characteristics of the fall (e.g., the direction, type, or extent of the fall).

There have been attempts to provide at least generalized detection and alerts in connection with falling. For example, US 8,348,875 discloses a method of controlling an exoskeleton bracing system to walk forward comprising operating an alerting device to generate an alert in response to a sensed condition, wherein the sensed condition comprises falling. US 8,905,955 B2 discloses a method of controlling an exoskeleton bracing system comprising halting actuation of the motorized joints when a signal that is received from a tilt sensor indicates falling. These methods are described entirely within the context of standing and sitting transitions. More generally, conventional detection and control methods have proven to be insufficient for full mitigation in response to a sensed fall. Different directions, types, extents, and related fall characteristics are not ascertained with precision by conventional methods, and the conventional methods thus do not provide control of the exoskeleton device for fall mitigation to reduce potential for injury as may occur for any given specific fall, nor enhance recovery from a fall. Summary of the Invention

The present invention provides exoskeleton control methods for fall mitigation for a legged mobility device or "exoskeleton" device, including detection/sensing and classifying a fall, and determining, effecting and controlling a corresponding mitigation and/or recovery behavior of the exoskeleton device. The safety methods described herein may halt actuation in response to High Severity Alerts as referenced above, but do not automatically halt actuation as a response to falling as done in conventional methods. Rather, the control methods of the present invention respond to falling as a staged process, wherein actuators of the exoskeleton or portions thereof are either actively seeking a nominal configuration or passively allowing motion to occur.

Furthermore, the control methods of the present invention control protective behavior that the exoskeleton will exhibit beyond a mere indication or alert should a fall occur in an attempt to prevent harm. Advantageously, the control methods described here apply generally to all states and do not need to rely on the use of force plate sensors as in the current state of the art. These control methods also facilitate the home use of the device by allowing the wearer to recover unassisted from a fall under various circumstances.

A method of controlling an exoskeleton device of a user performs fall mitigation operations. The control method may be performed by executing program code stored on a non-transitory computer readable medium. The control method may be applied generally to an orthotic device including a drive component that drives a joint component, and the control method may include detecting a fall state including a direction and extend of a fall, and controlling the drive component to selectively modulate the joint component to perform a fall mitigation operation.

In exemplary embodiments, the orthotic device is an exoskeleton device that is a powered legged mobility device including a plurality of drive components that drive joint components including at least knee joint components and hip joint components. The control method includes detecting a fall state including a direction and an extent of a fall; classifying the fall state based on the direction and the extent of the fall; and controlling the drive components of the exoskeleton device to selectively modulate the knee and hip joint components in accordance with the fall classification to perform a fall mitigation operation. Selectively modulating any given joint component or joint components may include applying torque, locking, releasing or otherwise effecting the position or movement of the joint component.

For example, falls may be classified based on direction, such as a forward or backward. Falls may also be classified based on extent, such as near, far, or terminal. Depending upon the fall classification based both on the direction and extent of a the fall, the drive components are controlled so as to selectively modulate the knee and hip joint components, the result being that the exoskeleton device is controlled to have different responses for different fall circumstances. In this manner, fall mitigation may be tailored to specific fall circumstances, thereby minimizing the potential for injury during a fall. The control method further may include controlling the drive components to perform a recovery operation to aid the user in returning to standing position after the fall.

These and further features of the present invention will be apparent with reference to the following description and attached drawings. In the description and drawings, particular embodiments of the invention have been disclosed in detail as being indicative of some of the ways in which the principles of the invention may be employed, but it is understood that the invention is not limited correspondingly in scope. Rather, the invention includes all changes, modifications and equivalents coming within the spirit and terms of the claims appended hereto. Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in

combination with or instead of the features of the other embodiments.

Brief Description of the Drawings

Fig. 1 is a drawing depicting an exemplary exoskeleton device as being worn by a user.

Fig. 2 is a drawing depicting a perspective view of an exemplary exoskeleton device in a standing position.

Fig. 3 is a drawing depicting a perspective view of the exemplary exoskeleton device in a seated position. Fig. 4 is a drawing depicting a front view of the exemplary exoskeleton device in a standing position.

Fig. 5 is a drawing depicting a side view of the exemplary exoskeleton device in a standing position. Fig. 6 is a drawing depicting a back view of the exemplary exoskeleton device in a standing position.

Fig. 7 is a drawing depicting a perspective view of an exemplary thigh assembly having two exemplary actuator cassettes installed therein.

Fig. 8 is a drawing depicting a front exploded view of the exemplary thigh assembly having two exemplary actuator cassettes installed therein.

Fig. 9 is a drawing depicting a perspective exploded view of the exemplary thigh assembly having two exemplary actuator cassettes installed therein.

Fig. 10 is a drawing depicting a top view of an exemplary actuator cassette.

Fig. 1 1 is a drawing depicting a bottom view of an exemplary actuator cassette.

Fig. 12 is a drawing depicting a perspective view of an exemplary actuator cassette.

Fig. 13 is a drawing depicting a cross-sectional view of an exemplary actuator cassette taken along the longitudinal direction. Fig. 14 is a drawing depicting a conceptual illustration of fall classification based on direction and extent.

Fig. 15 is a drawing depicting a conceptual illustration of forward fall progression in accordance with embodiments of the present invention.

Fig. 16 is a drawing depicting a conceptual illustration of backward fall progression in accordance with embodiments of the present invention.

Fig. 17 is a drawing depicting a conceptual illustration of prone and kneeling recovery in accordance with embodiments of the present invention.

Fig. 18 is a drawing depicting a conceptual illustration of prone recovery in accordance with embodiments of the present invention. Detailed Description

Embodiments of the present invention will now be described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. It will be understood that the figures are not necessarily to scale. For context, Figs. 1 -13 depict various views of an exemplary exoskeleton device that may be used in connection with the fall mitigation and recovery control methods of the present invention. A somewhat generalized description of such exoskeleton device is provided here for illustration purposes. A more detailed description of such device may be found in Applicant's International Patent Appl. No. PCT/US2015/023624 filed on March 3, 2015, which is incorporated here in its entirely by reference. It will be appreciated, however, that the described exoskeleton device presents an example usage, and that the fall mitigation and recovery control methods of the present invention are not limited to any particular configuration of an exoskeleton device. Variations may be made to the exoskeleton device, while the features of the present invention remain applicable. In addition, the principles of this invention may be applied generally to orthotic devices, which aid in mobility for persons without use or limited use of a certain body portion. The principles of this invention also may be applied generally to prosthetic devices, which essentially provide an electro-mechanical replacement of a body part that is not present, such as may be used by an amputee or a person congenitally missing a body portion.

As show in Fig. 1 , an exoskeleton device 10, which also may be referred to in the art as a "wearable robotic device", can be worn by a user. To attach the device to the user, the device 10 can include attachment devices 1 1 for attachment of the device to the user via belts, loops, straps, or the like. Furthermore, for comfort of the user, the device 10 can include padding 12 disposed along any surface likely to come into contact with the user. The device 10 can be used with a stability aid 13, such as crutches, a walker, or the like.

An exemplary legged mobbilty exoskeleton device is illustrated as a powered lower limb orthosis 100 in Figs. 2-6. Specifically, the orthosis 100 shown in Figs. 2-6 may incorporate four drive components configured as electro-motive devices (for example, electric motors), which impose sagittal plane torques at each knee and hip joint components including (right and left) hip joint components 102R, 102L and knee joint components 104R, 104L. Fig. 2 shows the orthosis 100 in a standing position while Fig. 3 shows the orthosis 100 in a seated position.

As seen in the figures, the orthosis contains five assemblies or modules, although one or more of these modules may be omitted and further modules may be added (for example, arm modules), which are: two lower (right and left) leg assemblies (modules) 106R and 106L, two (left and right) thigh assemblies 108R and 108L, and one hip assembly 1 10. Each thigh assembly 108R and 108L includes a respective thigh assembly housing 109R and 109L, and link, connector, or coupler 1 12R and 1 12L extending from each of the knee joints 104R and 104L and configured for moving in accordance with the operation of the knee joints 104R and 104L to provide sagittal plane torque at the knee joints 104R and 104L.

The connectors 1 12R and 1 12L further may be configured for releasably mechanically coupling each of thigh assembly 108R and 108L to respective ones of the lower leg assemblies 106R and 106L. Furthermore, each thigh assembly 108R and 108L also includes a link, connector, or coupler 1 14R and 1 14L, respectively, extending from each of the hip joint components 102R and 102L and moving in accordance with the operation of the hip joint components 102R and 102L to provide sagittal plane torque at the knee joint components 104R and 104L. The connectors 1 14R and 1 14L further may be configured for releasably mechanically coupling each of thigh assemblies 108R and 108L to the hip assembly 1 10.

In some embodiments, the various components of device 100 can be dimensioned for the user. However, in other embodiments the components can be configured to accommodate a variety of users. For example, in some embodiments one or more extension elements can be disposed between the lower leg assemblies 106R and 106L and the thigh assemblies 108R and 108L to accommodate users with longer limbs. In other configurations, the lengths of the two lower leg assemblies 106R and 106L, two thigh assemblies 108R and 108L, and one hip assembly 1 10 can be adjustable. That is, thigh assembly housings 109R, 109L, the lower leg assembly housings 107R and 107L for the lower leg assemblies 106R, 106L, respectively, and the hip assembly housing 1 13 for the hip assembly 1 10 can be configured to allow the user or medical professional to adjust the length of these components in the field. For example, these components can consist of slidable or movable sections that can be held in one or more positions using screws, clips, or any other types of fasteners. In view of the foregoing, the two lower leg assemblies 106R and 106L, two thigh assemblies 108R and 108L, and one hip assembly 1 10 can form a modular system allowing for one or more of the components of the orthosis 100 to be selectively replaced and for allowing an orthosis to be created for a user without requiring customized components. Such modularity can also greatly facilitate the procedure for donning and doffing the device.

In orthosis 100, each thigh assembly housing 109R, 109L may include substantially all the drive components for operating and driving corresponding ones of the knee joint components 104R, 104L and the hip joint components 102R, 102L. In particular, each of thigh assembly housings 109R, 109L may include drive components configured as two motive devices (e.g., electric motors) which are used to drive the hip and knee joint component articulations. However, the various embodiments are not limited in this regard, and some drive components can be located in the hip assembly 1 10 and/or the lower leg assemblies 106R, 106L. A battery 1 1 1 for providing power to the orthosis can be located within hip assembly housing 1 13 and connectors 1 14R and 1 14L can also provide means for connecting the battery 1 1 1 to any drive components within either of thigh assemblies 108R and 108L. For example, the connectors 1 14R and 1 14L can include wires, contacts, or any other types of electrical elements for electrically connecting battery 1 1 1 to electrically powered components in thigh assemblies 108R and 108L. In the various embodiments, the placement of battery 1 1 1 is not limited to being within hip assembly housing 1 13. Rather, the battery can be one or more batteries located within any of the assemblies of orthosis 100.

The referenced drive components may incorporate suitable sensors and related electronic controller or control devices for use in embodiments of the present invention. Embodiments of the present invention involve detecting a direction and an extent of falls through, for example, the use of accelerometers, gyroscopes, inertial measurement, and other sensors to detect and observe the upper leg orientation or angle and angular velocity, and to classify the fall according to direction and extent of the fall. The electronic control device may then selectively control the drive

components to modulate the joint components, and particularly the knee and hip joint components, to apply torque, implement locked or released states, or otherwise effect positioning or movement of the joint components for fall mitigation so as to reduce potential for injury as a result of a fall. The electronic control device further may exercise control of the drive components to modulate the joint components for fall recovery to return the user to a desirable position, and particularly standing, following a fall. To implement the features of the present invention, the electronic control device may include one or processor devices that are configured to execute program code stored on a non-transitory computer readable medium embodying the control methods associated with the present invention. It will be apparent to a person having ordinary skill in the art of computer programming of electronic devices how to program the electronic control device to operate and carry out logical functions associated with present invention. Accordingly, details as to specific programming code have been left out for the sake of brevity. Also, controller functionality could be carried out via dedicated hardware, firmware, software, or any combinations thereof, without departing from the scope of the invention. As will be understood by one of ordinary skill in the art, therefore, the electronic control device may have various implementations. For example, the electronic control device may be configured as any suitable processor device, such as a programmable circuit, integrated circuit, memory and I/O circuits, an application specific integrated circuit, microcontroller, complex programmable logic device, other programmable circuits, or the like. The electronic control device may also include a non-transitory computer readable medium, such as random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), or any other suitable medium. Instructions for performing the methods described below may be stored in the non-transitory computer readable medium and executed by the processor device.

In the various embodiments, to maintain a low weight for orthosis and a reduced profile for the various components, the drive components may include a substantially planar drive system that is used to drive the hip and knee articulations of the joint components. For example, each motor can respectively drive an associated joint component through a speed-reduction transmission using an arrangement of sprocket gears and chains substantially parallel to the plane of sagittal motion. Referring to Figs. 7-13, consolidating the moveable parts into self- contained units, referred to herein as "cassettes," allow for ease of maintenance and replacement because cassettes are swappable, making them easier to service or requiring less of a variety in spare components. As used herein, "self-contained" means that the cassette includes everything necessary to operate in a fully functional manner if supplied with power. Thus, for example, if power is supplied to electrical contacts of the cassette, the cassette would actuate.

In the illustrated embodiment of the drive components, the motor is integrated onto a common baseplate along with sprockets that control the motion of a joint link. Bearings and chains, with and/or without tensioners provide smooth and efficient transfer of motion from the motor to the joint angle. Integrating the motor into the cassette allows for a thinner overall package configuration and provides consistent alignment among parts. Moreover, integrating the motor also creates a larger surface area to transfer and emit heat generated by the motor. In the instance of a mobility assistance device, these cassettes may pertain to a specific joint or set of joints on the device. Each may have a unique actuation unit or share an actuation unit. They may include actuators, with or without a power source, and/or a method of transmitting movement. The illustrated embodiment includes a brushless DC motor with chains and sprockets to create and transmit motion, although other embodiments may utilize electric motors, linear actuators, piezoelectric actuators, belts, ball screws, harmonic drive, gear drive (bevel or planetary), or any

combination thereof. The cassettes may also house the electronic control device, and further may contain the referenced sensor elements such as the

accelerometers, gyroscopes, inertial measurement, and other sensors to detect and observe the upper leg orientation or angle and angular velocity. The self-contained cassette units can be preassembled to aid in manufacturing the broader device. This allows for quick servicing of the device since individual cassettes can be swapped out and serviced.

Therefore, a removable, self-contained, ovular actuator cassette 500 may be receivable in a receptacle of a wearable robotic device. The cassette 500 may include a first circular portion 520 housing a motive device (e.g., an electric motor) 502. A second circular portion 522 may be longitudinally offset and longitudinally overlapping the first circular portion and may house a first portion of a drivetrain 514, 516 operatively coupled to and driven by the motive device 502. A third circular portion 524 may be longitudinally offset from the first and second circular portions and longitudinally overlapping the second circular portion and may house a second portion of the drivetrain 504. These three overlapping circular portions make an ovular shape, which may include the referenced sensors and electronic control devices. Therefore, an ovular housing 530 may support the motive device 502 and drivetrain 502, 514, 516. Long sides of the ovular housing are straight and parallel with each other and tangentially terminate as curved end surfaces of the ovular housing.

Referring to Figs. 7-13, with Fig. 13 of the right side being representative, the powered joints may be implemented by disposing a joint sprocket gear 504 at one end of thigh assembly housing 109R parallel to the sagittal plane and configuring the joint sprocket gear 504 to rotate parallel to the sagittal plane. To provide the sagittal plane torque for knee joint component 102R, the connector 1 12R can extend from the joint sprocket gear 504 and be mechanically connected, so that rotation of the joint sprocket gear 504 results in application of torque to the lower leg assembly 106. A slot or receiving element can be provided for the connector 1 12R to link the thigh assembly 108R and lower leg assembly 106R. The receiving element and the connector 1 12R can be configured such that the connector can removably connect the thigh assembly 108R and lower leg assembly 106R. In the various embodiments, clips, screws, or any other types of fastener arrangements can be used to provide a permanent or a removable connection. In some embodiments, quick connect or "snap-in" devices can be provided for providing the connection. That is, these quick connect devices allow connections to be made without the need of tools. These types of quick connect devices can not only be used for mechanically coupling, but for electrical coupling with the sensors and control electronics. In some

embodiments, a single quick connect device can be used to provide both electrical and mechanical coupling. However, the various embodiments are not limited in this regard and separate quick connect devices can be provided for the electrical and mechanical coupling. It is worth noting that with quick disconnect devices at each joint, the orthosis can be easily separated into three or five modular components - right thigh, left thigh, right lower leg, left lower leg, and hip assemblies - for ease of donning and doffing and also for increased portability.

The knee joint component 104R may be actuated via operation of a motor 502, as discussed above. The motor 502 can be an electric motor that drives the knee joint 104R (i.e., joint sprocket gear 504) using a two-stage chain drive transmission. For example, as shown in Fig. 13, a first stage can include the motor 502 driving, either directly or via a first chain, a first drive sprocket gear 514. The first drive sprocket gear 514 is mechanically coupled to a second drive sprocket gear 516 so that they rotate together about the same axis based on the power applied by motor 502 to first drive sprocket gear 514. The second drive sprocket gear 516 can be arranged so that it is disposed in the same plane as the joint gear 504. Thus, a second chain can then be used to drive joint sprocket gear 504 using the second drive sprocket gear 516 and actuate the knee joint 104R. The gear ratios for the various components described above can be selected based on a needed amount of torque for a joint, power constraints, and space constraints.

Each stage of the chain drive transmission can include tensioners, which can remove slack from a chain and mitigate shock loading. Such tensioners can be adjustable or spring loaded. In addition, a brake 570 can be provided for motor 502. For example, a solenoid brake may be provided which engages a brake pad against the rotor 524 of the motor 502 in one state, and disengages the brake pad in another state. However, the various embodiments are not limited to this particular brake arrangement and any other methods for providing a brake for motor 502 can be used without limitation. The configuration illustrated in Fig. 13 has been discussed above with respect to an arrangement of sprocket gears and chains. However, the various embodiments are not limited in this regard. That is, any other arrangement of gears, with or without chains, and providing a reduced profile can be used. Furthermore, the various embodiments disclosed herein are not limited to an arrangement of gears and/or chains. For example, in some configurations, a belt and pulley arrangement could be used in place of the chain and sprocket arrangement. Furthermore, a friction drive arrangement can also be used. Also, any combination of the arrangements discussed above can be used as well. Additionally, different joints can employ different arrangements. In the various embodiments of the drive components, a motor for each of the hip and knee joint components 102R, 102L, 104R, 104L can be configured to provide a baseline amount of continuous torque and a higher amount of torque for shorter periods of time. For example, in one configuration, at least 10 Nm of continuous torque and at least 25 Nm of torque for shorter (i.e., 2-sec) durations are provided. In another example, up to 12 Nm of continuous torque and 40 Nm of torque for shorter (i.e., 2-sec) durations. As a safety measure, both knee joints 104R and 104L can include normally locked brakes, as discussed above, in order to preclude knee buckling in the event of a power failure.

The described exoskeleton device can be controlled in a manner that provides (1 ) fall mitigation by staged fall progression, and (2) fall recovery. In embodiments of the present invention, detected falls are classified by direction and extent. While conventional configurations have suggested fall detection through observation of force or tilt sensors, classification of the fall according to direction and/or extent has not been employed in connection with fall detection and recovery. Control methods are described for controlling joints and various components of an exoskeleton device based on fall detection and classification for a fall mitigation operation, and further for controlling components of the exoskeleton device to execute a fall recovery operation. Although the exemplary control methods are described below as a specific order of executing functional logic steps, the order of executing the steps may be changed relative to the order described. Also, two or more steps described in succession may be executed concurrently or with partial concurrence. It is understood that all such variations are within the scope of the present invention. Fig. 14 is a drawing depicting a conceptual illustration of fall classification based on direction and extent. As shown in Fig. 14, falls may be classified according to direction as being either a forward fall or a backward fall. Falls further may be classified according to extent as being near, far, or terminal in accordance with the regions shown in Fig. 14. Sideways falls may be classified similarly based on direction (left or right) and extent (near, far, or terminal). It will be appreciated that the fall classification of Fig. 14 depicts approximate ranges and may be varied depending upon circumstances. In addition, although fall extent in Fig. 14 is broadly classified as near, far, or terminal, intermediate classifications or multiple stages within one or more of the broad categories may be employed in the fall mitigation methods described herein.

An aspect of the present invention includes fall mitigation control methods to generate staged falling control of the joint components, related drive components, and motors of the exoskeleton device, which provide fall mitigation in an attempt to protect the user as the user falls, and/or allow the user to come to an intermediate or terminal position from which the user can recover. In general, the staged falling control methods for fall mitigation may include the steps of: (1 ) detecting a fall state including a direction and extent of a fall; (2) classifying the fall state based on a direction and an extent of the fall; and (3) controlling the exoskeleton device to selectively modulate exoskeleton components in accordance with the fall

classification. The control method may be applied to an exoskeleton device generally including a drive component that drives a joint component, and the control method may include detecting a fall state including a direction and extend of a fall, and controlling the drive component to modulate the joint component to perform a fall mitigation operation. Accordingly, the methods of the present invention may be employed on a relatively simple orthotic device including only one joint component (e.g., a singular knee orthotic), or more complex exoskeleton devices that include a plurality of joint components, such as a legged mobility device having left and right knee and hip joint components such as the exoskeleton device described above. As used throughout, modulating any given joint component or joint components may include applying torque, locking, releasing or otherwise effecting the position or movement of the joint component. In general, the staged falling methods enable the user's torso to remain upright as the user falls. With such control, the user's head is less exposed to the environment because the head will be led to the ground by following either the buttocks or the knees, and thus the head will travel at lower speeds particularly because the upper body is not rotating and other portions of the body absorb initial impacts. This in turn reduces the likelihood and severity of head injury should a fall occur. The present invention, therefore, provides a method of controlling an orthotic device of a user for fall mitigation. In exemplary embodiments, the orthotic device is an exoskeleton device that is a powered legged mobility device comprising a plurality of drive components that drive joint components including at least knee joint components and hip joint components. The control method may include the steps of: detecting with one or more sensors a fall state including a direction and an extent of a fall; classifying with an electronic control device the fall state based on the direction and the extent of the fall; and controlling the drive components of the exoskeleton device with the electronic control device to selectively modulate the knee and hip joint components in accordance with the fall classification to perform a fall mitigation operation. Additional features of the control methods are described in detail below. Although the exemplary methods may be described below as a specific order of executing functional logic steps, the order of executing the steps may be changed relative to the order described. Also, two or more steps described in succession may be executed concurrently or with partial concurrence. It is understood that all such variations are within the scope of the present invention. The various control methods may be performed by the electronic control device executing program code stored on a non-transitory computer readable medium. Fig. 15 is a drawing depicting a conceptual illustration of forward fall progression in accordance with embodiments of the present invention. As referenced above, the first and second steps in a staged falling control method may be detecting a fall state and classifying the fall state based on a direction and an extent of the fall. As shown in Fig. 15, in a first example fall mitigation control method, in a typical forward fall progression, a near forward fall would be detected and classified, with the detected direction being forward and the extent determined as being within the near range. Such a classification would be representative of a commonly initiated forward fall. The third general step of a staged falling method may be controlling the exoskeleton device to selectively modulate exoskeleton components in accordance with the fall classification. In exemplary embodiments of the present invention, when the classification step results in a near forward fall classification, the exoskeleton components are controlled by controlling the drive components to (1 ) apply torque to the knee joint components and the hip joint components such that leg components of the exoskeleton device (and thus the legs of the user) are straightened and brought together, and (2) lock the knee and hip joint components, thereby permitting the user to stand. When the fall stage corresponds to a near fall, the fall angle is minimal, and the system acts in a manner that would permit immediate recovery to standing without continued falling. By controlling the exoskeleton components to straighten and bring the legs together, a user may potentially return to a standing position. Such control operation further ensures that in the event falling continues, the fall should continue in the same forward direction, thereby avoiding falling to the side insofar as a sideways fall becomes substantially less likely if the feet are together as viewed in the sagittal plane. The staged falling control method steps of detection and classification of falling based on direction and extent are continuously operative. Accordingly, in the event forward falling continues, as shown in Fig. 15 the classification step will next result in a determination of a far forward fall, as the user enters such far range shown in Fig. 15. In exemplary embodiments of the present invention, when the classification step results in a far forward fall classification, the exoskeleton components are controlled by controlling the drive components to release the knee joint components to perform passive or active flexion of the knees. With the release of the knee joint components, the knees are thus permitted to begin to give and buckle. In this manner, the exoskeleton components are controlled to permit passive flexion of the knees, which enables an upright torso. As shown in Fig. 15, under certain circumstances this can permit the user to come to a kneeling position if the user is able to stabilize himself, such as by using a stability aid or the environment. A kneeling position is desirable because, as further detailed below, the user may recover from kneeling to standing. Reaching a kneeling position further is desirable because the potential of injury to the head or torso from further falling from the kneeling position is significantly less than if a user were to fall fully from standing erect, and possibly striking the head or torso on the ground or an object in the environment from the standing position. Again, the staged falling control method steps of detection and classification of falling based on direction and extent are continuously operative. It may occur that a user is unable to stabilize himself to a kneeling position, and the forward fall continues. Accordingly, in the event forward falling continues, as shown in Fig. 15 the classification step will next result in a determination of a terminal forward fall classification, as the user enters such terminal range shown in Fig 15. In exemplary embodiments of the present invention, when the classification step results in a terminal forward fall, the exoskeleton components are controlled by controlling the drive components to release the various exoskeleton components, including the knee joint components and the hip joint components, thereby permitting the user to fall progressively to a prone position. By releasing the exoskeleton joint components, including the knee joint components and the hip joint components, this allows the user and device to fall more smoothly to the prone position shown in the right-most panel of Fig. 15. When a full fall is imminent at the terminal stage, the user's upper legs are close to horizontal. The exoskeleton components are controlled to enter a default state in which all joints are free to move, so that the exoskeleton device and the user move together to the greatest extent possible as they meet the ground. Given the previous knee flexion permitted during the far forward stage, the user will tend to hit the ground in a progressive manner, with the torso following the knees, and the head following the torso, rather than as a single straight impact with all portions of the body impacting at once. With the progressive impact, the impact force is lessened resulting in a substantially reduced potential for injury.

A fall mitigation control method may be performed comparably for a backward wall as performed for a forward fall. Fig. 16 is a drawing depicting a conceptual illustration of backward fall progression in accordance with embodiments of the present invention. As referenced above, the first and second steps in a staged falling control method again may be detecting a fall state and classifying the fall state based on a direction and an extent of the fall. As shown in Fig. 16, in another example control method, in a typical backward fall progression, a near backward fall would be detected and classified, with the detected direction being backward and the extent determined as being within the near range. Such a classification would be

representative of a commonly initiated backward fall. The third general step of a staged falling method may be controlling the exoskeleton device to selectively modulate exoskeleton components in accordance with the fall classification. In exemplary embodiments of the present invention, when the classification step results in a near backward fall classification, the exoskeleton components are controlled by controlling the drive components, similarly as in the near forward fall to (1 ) apply torque to the knee joint components and the hip joint components such that leg components of the exoskeleton device (and thus the legs of the user) are

straightened and brought together, and (2) lock the knee and hip joint components, thereby permitting the user to stand. In the backward fall situation as well, when the fall stage corresponds to a near fall, the fall angle is minimal, and the system acts in a manner that would permit immediate recovery to standing without continued falling. Similarly as with the near forward fall, by controlling the exoskeleton components to straighten and bring the legs together during a near backward fall, a user may potentially return to the standing position. Such control operation further ensures that in the event falling continues, the fall should continue in the same backward direction, thereby avoiding falling to the side insofar as a sideways fall becomes substantially less likely if the feet are together as viewed in the sagittal plane. The exoskeleton components further may be controlled to flex the hip joint components during a near backward fall, so that the torso may remain upright in the event the backward fall continues.

Again, the staged falling control method steps of detection and classification of falling based on direction and extent are continuously operative. Accordingly, in the event backward falling continues, as shown in Fig. 16 the classification step will next result in a determination of a far backward fall classification, as the user enters such far range shown in Fig. 16. In exemplary embodiments of the present invention, when the classification step results in a far backward fall classification, the exoskeleton components are controlled to best ensure that the torso remains upright. In particular, the exoskeleton components may be controlled to drive the joint components to perform active flexion of the hip joint components to maintain an upright torso, which ultimately is intended to result in the full fall to a sitting position, concentrating the impact at the buttocks.

Again, the staged falling control method steps of detection and classification of falling based on direction and extent are continuously operative. As the backward falling continues, as shown in Fig. 16 the classification step will next result in a determination of a terminal backward fall classification, as the user enters such terminal range shown in Fig 16. Similarly as with the terminal forward fall, the exoskeleton joints, including the knee joint components and the hip joint

components, are released to allow the user and device to fall more smoothly, which in the backward fall situation should result in the user falling to the position shown in the right-most panel of Fig. 16. When a full fall is imminent at the terminal stage, the user's upper legs are close to horizontal. The exoskeleton components are controlled such that the exoskeleton joints enter the referenced default a state in which such joints are free to move, so that the exoskeleton device and the user move together to the greatest extent possible as they meet the ground. With the torso upright from the far fall position, the user will tend to hit the ground largely in a sitting position. Even if the impact were to propel the user backward from sitting, the user again will tend to impact the ground in a progressive manner, with the torso following the buttocks, and the head following the torso, rather than as a single straight impact with all portions of the body impacting at once. In the backward fall also, therefore, with the progressive impact the impact force is lessened resulting in a substantially reduced potential for injury.

The present invention improves over conventional systems, which largely have operated to fully halt actuation in response to detecting a fall. In contrast, in the present invention the exoskeleton components are controlled distinctly at each stage of the fall as detected and classified based on the direction and extent of the fall. In this manner, the exoskeleton motors and related drive components provide active flexion/extension, passive support, or are completely free according to the direction and extent of a fall. The present invention, therefore, provides enhanced opportunity for recovery during or from a fall, and otherwise substantially reduces the potential for injury, as compared to conventional configurations which do not provide for a staged control and fall mitigation based on both direction and extent of a fall.

Enhanced control of recovery after such a staged fall is now described.

Should a terminal fall occur, the staged fall control methods described above allow for fall recovery, such that the user may return to a standing position either independently using a stability aid, and/or with the aid of another person. At the outset, recovery control methods are essentially the same in the cases of both a staged forward fall and a staged backward fall, as the different recovery methods would begin from a forward prone position. Accordingly, in the event of a staged backward terminal fall, the first step simply would be for a user to roll over from a sitting or full backward position to a forward prone position. For the initial rollover, the joint components may be driven to release the knee and hip joint components, thereby permitting the user to turn over to the prone position. Once the user has moved to the forward prone position, recovery control follows in a common manner regardless of whether the user initially fell forward or backward.

In exemplary embodiments, the exoskeleton joint components may be controlled to perform a rollover assist operation. For example, the drive components may be controlled to drive the hip and knee joint components to straighten one leg on the side or in the direction of the desired rollover, and optionally further to bend the knee joint component of the other leg. Such leg positioning may provide for an easier rollover by the user. Fig. 17 is a drawing depicting a conceptual illustration of a prone and kneeling recovery control method in accordance with embodiments of the present invention. In exemplary embodiments of the present invention, a recovery control method proceeds as follows. When the user initially is in the forward prone position as referenced above, the exoskeleton components are controlled such that the drive components release the hip and knee joint components (such joints as referenced above may be freed automatically in either a backward or forward terminal fall, or can be freed otherwise while in the forward prone position by putting the device in standby, for instance). With the knee and hip joint components released, the user can then perform a walk-back motion by walking backward with their hands, and in doing so may utilize a stability aid or the environment, to come to their hands and knees. The drive components of the exoskeleton device may or may not be controlled to drive the joint components to assist with this hands walk-back motion. The user then may utilize a stability aid or the environment to straighten the hips and come to a kneeling position. Once the user is kneeling, the exoskeleton components are controlled to provide extensive torque at the knee joints. Such extensive torque tends to straight the leg components of the exoskeleton device, which operates to facilitate standing as the user pushes downward on a stability aid or the environment to stand. As the user stands, the exoskeleton components are controlled to provide support at the hip joint components to keep the torso upright to aid in standing.

As referenced above, there is potential during the staged forward fall for the user coming to the knees during the fall itself, as seen in the third portion of Fig. 15. If the user achieves kneeling during the fall itself, the recovery control method may proceed from the kneeling position without first having to go to the forward prone position. From the kneeling position, as above the exoskeleton components are controlled to provide extensive torque at the knee joints to straighten the leg components to aid in standing, with additional support provided by the hip joint components as the user stands.

In an alternative embodiment of a fall recovery control method, a user may attempt to recover without going to an intermediate kneeling position. Fig. 18 is a drawing depicting a conceptual illustration of prone recovery control method in accordance with embodiments of the present invention. In this alterative fall recovery control method, similarly to the previous method the user begins in the forward prone position with the exoskeleton drive components controlled to release the hip and knee joints (again, such joints may be freed automatically in either a backward or forward terminal fall, or can be freed otherwise while in the forward prone position by putting the device in standby, for instance). After this initial release, the drive components drive the knee joint components to lock in a rigid position. The user then performs a walk-back motion by walking backward with the hands, and in doing so may utilize a stability aid or the environment, to come to the user's hands and feet while the knee joints are controlled to remain rigid as if touching their toes in a conventional exercise manner. The drive components of the exoskeleton device may or may not be controlled further to assist with this hands walk-back motion. As the knees are kept rigid in this embodiment, an intermediate kneeling position is not attained. Following the rigid-knees walk-back, the user utilizes a stability aid or the environment to straighten their hips and stand. Similarly to the previous method, as the user stands, the exoskeleton components are controlled to provide support at the hip joint components to keep the torso upright to aid in standing.

Although the invention has been shown and described with respect to a certain embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and

understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a "means") used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.