FIELD OF INVENTION

The present invention relates to movement assist devices, such as a legged mobility device or “exoskeleton” device, and more particularly to drive mechanisms and coupling components for driving the joint components of such devices.

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. The use of powered orthoses presents an opportunity for electronic control of the orthoses, for enhanced user mobility.

An example of the current state of the art of exoskeleton devices is shown in Applicant's co-pending International Application Serial No. PCT/US2015/23624, entitled “Wearable Robotic Device,” filed 31 Mar. 2015. Such device is representative of an effective and generally user friendly exoskeleton device. There is a general concern with exoskeleton devices that they be compact and light weight. Device users typically have significant physical impairments, and reducing the size and weight of exoskeleton devices makes them easier to don and otherwise manipulate. With increased ease, users can experience more freedom of mobility, and can reduce the need for outside caregivers and assistance.

The drive mechanism for the joint components is one aspect of exoskeleton devices that is a continuing subject of concern for rendering exoskeleton devices more compact and light weight. Reduced size and weight must be balanced with performance so as to provide a device that is more user friendly to don and manipulate, while still providing adequate torque and driving forces for operation of the exoskeleton device.

In a recent survey of 354 wheelchair users and 127 healthcare professionals “ease of putting on and taking off the device” was rated as “very important”, and “portability of the device” was rated as “important”, (Wolff et al, A Survey of Stakeholder Perspectives on Exoskeleton Technology, JNER 2014.) Conventional legged mobility devices often incorporate two full leg braces or leg components rigidly connected to a common hip brace or hip component. This conventional arrangement of a lower leg, upper leg, and hip components will generally articulate at each knee joint and each hip joint, making the device cumbersome to handle when it is being worn by a user. Additionally, the weight of each segment may be significant, particularly if actuation and batteries are incorporated.

To address the cumbersome nature of a fully assembled legged mobility device, such a system may be designed with modular components that are handled separately and are connected together during the donning process. In a modular system, ease of donning/doffing and portability become significant issues. Furthermore, as referenced above, device users who might benefit from a powered orthosis suffer from significant mobility impairments, which not only inhibit volitional leg movement but also impair trunk and/or upper extremity function. Such impairments often impede a user's ability to achieve independent donning and doffing without assistance of a caregiver, which is undesirable.

SUMMARY OF THE INVENTION

The present invention is directed to movement assist devices such as powered limb or gait orthoses or wearable robotic legged mobility devices or “exoskeletons,” and more particularly to coupling mechanisms and drive mechanisms for driving the joint components of such devices. An aspect of the invention is an actuator assembly that includes an enhanced magnetic coupling system, which enables easy, one-handed coupling of a driven component to a rotational driving member of the actuator assembly.

In exemplary embodiments, the rotational driving member may be an output reel of a cable reel assembly that is part of the actuator assembly. In particular, the cable reel assembly may constitute a final stage of a multi-stage speed reduction transmission portion of the actuator assembly. This output reel may include a plurality of recessed pockets (e.g., six recessed pockets in an exemplary embodiment), with one or more of the pockets having a cylindrical neodymium disc magnet installed in the bottom of the recessed pocket. The driven component, which may be a contoured plastic orthotic section which contours and attaches to the lower leg of a human wearer, may include a coupling portion having mating raised features that essentially match the recessed pockets of the rotational driving member or output reel. These raised mating features may include embedded cylindrical neodymium disc magnets that couple to the magnetic discs in the recessed pockets of the output reel.

During assembly of the legged mobility device (i.e. donning), when the coupling portion of the driven component is placed in proximity to the rotational driving member or output reel, the magnetic attraction draws the two components together, and the raised mating features of the coupling portion of the driven component become mechanically engaged in the recessed pockets of the rotational driving member. Once the two components are drawn together by magnetic coupling, a mechanical interface of a mating surface of the raised mating features of the driven component against an opposing mating surface of the recessed pockets of the rotational driving member handles the torque loads applied to the actuator assembly. Accordingly, although the magnetic coupling aids in donning, the principal torque accommodation is performed by the mechanical interface of the two opposing mating surfaces. The mechanical interface of the recessed pockets and the raised mating features further may have matching steps or tapers (e.g., of approximately 15 degrees relative to normal) which further eases alignment.

To further enhance the self-aligning capability of the magnetic coupling system, the magnetic elements in each of the rotational driving member and the driven component may be installed with alternating polarity. In other words, a first magnetic element may be installed in the rotational driving member with the north pole facing out; a next adjacent magnetic element may be installed with the south pole facing out; and so on in alternating fashion. The coupling portion of the driven component similarly would have magnetic elements installed with alternating polarity, and of opposite polarity relative to the magnetic elements of the recesses to achieve the magnetic coupling. In this way, the magnetic coupling system has magnetic keying that actively forces the two components apart if the user is attempting to make the coupling in the wrong alignment of the actuator assembly relative to the driven component.

In an exemplary embodiment, the six magnetic connections each have a holding force of approximately six pounds, for a total coupling force of approximately 36 pounds. In addition to the magnetic polarity keying, which discourages misalignment during donning, the recessed pockets of the rotational driving member may be arranged in a non-uniform pattern of differing surfaces that matches an opposing pattern of the surfaces of the raised features of the driven element. The patterning of the mechanical interface provides an additional mechanical keying feature that further precludes an improper misaligned engagement between the two components of the coupling system. Thus, the coupling system may be both mechanically and magnetically keyed to ensure proper alignment when donning.

In another exemplary embodiment, one side of the coupling system may be loaded with ferrous discs (e.g. steel) rather than magnetic elements. This could enable connecting in a variety of orientations if desired, in contrast to the keying of the previous embodiment. Such configuration also may reduce the mating impact of the coupling components as they come together, as the attractive force of magnet to steel decays more quickly with distance than that of magnet to magnet. Connecting in a variety of orientations also could be achieved by maintaining a uniform polarity convention for all magnets, in contrast to the magnetic keying of the previous embodiment. In other words, in each of the rotational driving member and the driven component the polarity may be the same for all magnetic elements, i.e., north pole facing out for all magnetic elements in the rotational driving component and south pole facing out for all magnetic elements in the driven component, or vice versa. In yet another exemplary embodiment, the magnetic elements may be used to assist with alignment and engagement during assembly, but an additional locking feature may be present to positively engage the coupling of the two components, and/or handle the torque loading and/or separation forces during use.

In accordance with such features, a joint actuator assembly includes a motor, a rotating driving member driven by the motor for driving a driven component, and a transmission assembly located between the motor and the rotating driving member that provides a speed reduction from the motor to the rotating driving member. The rotating driving member comprises a magnetic coupling including a plurality of magnetic elements that are configured to magnetically couple with an opposing magnetic coupling of the driven component. The actuator and driven component may be combined into a mobility device including a magnetic coupling system having a first magnetic coupling on the actuator assembly that magnetically couples to a second magnetic coupling on the driven component. The magnetic coupling system includes plurality of magnetic elements located as part of one or both of the first and second magnetic couplings. The first and second magnetic couplings have opposing mating surfaces that joint together when the magnetic coupling system is in a coupled position.

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.

