Biomechanical foot guidance linkage

A gait replication apparatus can include a scalable mechanical mechanism configured to replicate different gaits. The scalable mechanical mechanism can include, for example, a four-bar linkage, a pantograph, a cam/Scotch-yoke mechanism, and so forth. In some embodiments, the mechanical mechanism includes a beam rotating about an axis passing proximate to its center, with a foot pedal slidably coupled with the beam, and a timing chain/belt or cable pulley-pair coupled with the foot pedal and looped about the beam. A method can include decomposing a foot path defined by Cartesian coordinates into polar coordinates, and providing a mechanical support for a foot, where a first mechanism controls an angular position of the mechanical support with respect to a reference frame, and a second mechanism controls a radial distance of the mechanical support from the reference frame.

SUMMARY

A human gait replication apparatus can include a scalable mechanical mechanism configured to replicate different gaits. The scalable mechanical mechanism can include, for example, a four-bar linkage (e.g., with adjustable link lengths), a pantograph100(e.g., coupled with a Cardan gear), a cam/Scotch-yoke mechanism (e.g., with a beam oscillated by a cam), and so forth. In some embodiments, the mechanical mechanism includes a beam rotating about an axis passing proximate to its center, with a foot pedal slidably coupled with the beam, and a timing chain/belt or cable-pulley pair coupled with the foot pedal and looped about the beam (e.g., where the timing chain/belt or cable-pulley pair is coupled with a rocker arm of a four-bar linkage).

A method can include decomposing a foot path defined by Cartesian coordinates into polar coordinates, and providing a mechanical support for a foot, where a first mechanism controls an angular position of the mechanical support with respect to a reference frame, and a second mechanism controls a radial distance of the mechanical support from the reference frame (e.g., where the second mechanism can be adjusted independently of the first mechanism to scale the gait).

DETAILED DESCRIPTION

Referring generally toFIGS. 1 through 21, gait replication apparatus122are described. Effective gait rehabilitation can be challenging, often requiring strenuous effort from a therapist, expensive technology, or both. One rehabilitation method involves assisting the patient's foot through a gait-like trajectory. While numerous devices have been developed to address the gait training needs of adults, these tools do not always scale well to meet the needs of a child's smaller body size. As described herein, gait-guidance devices can be scaled to address the gait retraining needs of individuals of varying body sizes from a child to an adult. Additionally, the gait-guidance devices can be used to vary gait-like trajectory for adults having varying therapeutic needs. For example, a shorter step length can be facilitated for a patient having, for example, limited range of motion due to a problem with hip flexion.

As described herein, a foot guidance linkage device can replicate biomechanically correct walking. The device can be used for gait rehabilitation, exercise, and/or cardiovascular fitness. The device can also scale motion for use by children and adults with varying step length. The device may use a decomposition of a foot path into polar coordinates (e.g., as opposed to Cartesian coordinates) so that scaling can be accomplished by controlling a single degree of freedom. Further, in some embodiments, the device can be bilaterally adjustable, facilitating independent step size/length adjustment for a foot on either side (right or left) of a user. In other embodiments, step size/length adjustment can be coupled together on both sides (right and left).

Gait (walking) impairments can be detrimental to health and mobility as they may contribute to trips and falls and limit access to community and social activities. In 2013, approximately 20.6 million Americans (7.1% of the population) had an ambulatory disability, of whom approximately 330,000 (1.6%) were children. To improve or sustain walking capacity, many individuals partake in physical rehabilitation programs that include intensive practice of gait-like activities. Clinicians and/or technology help guide the patient through repetitive gait cycles to strengthen not only the muscles important for walking, but also the neural connections that help control gait. One challenge is that sophisticated technology that has been developed for adults does not always scale well to meet the needs of those with smaller bodies (e.g., young, pre-pubescent children). As a result, clinics and school settings providing rehabilitation services for children may need to purchase separate equipment to address the needs of smaller versus larger stature children. This need for additional equipment can be difficult, particularly in light of budget and space constraints faced by many institutions. An affordable and scalable gait guidance system is described that can be used to address the walking needs of adults and children.

Children as young as two (2) years old demonstrate a kinematic gait profile that is very similar to that of adults. In some embodiments, normalization methods are used to compare pediatric data to standard adult gait. For example, children's gait data between ages five (5) and twelve (12) may be very consistent following normalization. Regardless of the velocity at which a child is travelling, there may be only minor differences in step length, cadence, and other factors. In some embodiments, normalized parameters may show no correlation between age and gait parameters after the age of about seven (7). Apparatus122and techniques described herein may be used with individuals ranging in age from about two (2) to about twelve (12) and upwards (e.g., depending, in some instances, upon the cognitive abilities of a particular child). For example, in some embodiments, gait-replication is provided for adults and children (e.g., where the children range in age from about four (4) years old to about twelve (12) years old, adults over sixty five (65) years old, etc.).

The foot is composed of a complex set of articulations across twenty-six (26) bones that are controlled by a myriad of muscles often spanning multiple joints. Due to the similarity of normalized paths, a single foot trajectory can be chosen and scaled to match the gait path of various leg lengths. However, unique points on the foot traverse different trajectories during gait. To simplify observational and biomechanical analysis of gait, the foot's trajectory can be simplified to include an analysis of the forefoot and rearfoot. Using this approach, the foot can be modeled as two hinged, rigid bodies. With the toes affixed to a solid surface, the metatarsal heads serve as the juncture between the two rigid bodies. A heel marker can provide a biomechanical reference for the proximal aspect of the rearfoot.

A normalized sample path of a child's third metatarsal and heel trajectory are shown inFIG. 2. These data are taken relative to the center of mass of the body, causing the trajectory to be a smooth, closed loop. In some embodiments, foot trajectory can be modeled by tracing the path of the metatarsal only. However, if the foot angle is taken into consideration, all points on the foot may travel through a gait-like trajectory. This tracking of one point vs. two points on the foot may be analogous to the difference between the path-generation and rigid-body-guidance problems in kinematic synthesis.

Currently, gait training methods may be expensive and/or labor-intensive, placing notable demands on the clinician's body to deliver the intervention. Treadmill and elliptical training are less expensive, but often require significant effort from a therapist and may require that the patient have significant strength to support themselves. To address this problem, gait rehabilitation techniques have been developed by researchers using treadmills with body weight support and robotic-assisted driven-gait orthoses. Gait training methods are usually specialized for different body sizes, meaning that different gait training devices are required for pediatric and adult gait therapy. Robotic gait-training devices can be extremely expensive, and readjusting link lengths to match leg parameters may be cumbersome. In addition, some potential gait training equipment options do not propel the foot through a gait-like trajectory, thus reducing task-specific training thought to be beneficial for strengthening not only the muscles, but also the neural pathways responsible for controlling movements.

Gait replication apparatus122are described herein that can be used by adults and children alike, accommodating a broad range of step lengths. Further, the apparatus122can be used in rehabilitation clinics, for in-home therapy, in hospitals, in schools and community centers, and so on. In some embodiments, the apparatus122can provide gait-like trajectory, where the mechanism constrains the feet to a trajectory similar to normal gait motion. Further, the apparatus122can be scalable to accommodate individuals with a step length between at least approximately twenty centimeters (20 cm) and at least approximately one hundred and two centimeters (102 cm) while producing a linearly-scaled gait trajectory, such that the size of the foot path is variable, but not its shape. Also, the entire scaling process may be performed by one actuator, eliminating the possibility of accidental misalignment or inaccurate mechanism trajectory.

In some embodiments, the apparatus122can be adjustable to accommodate specific impairments, such as different step lengths for each foot and/or reduced step heights. In some embodiments, the apparatus122can be cost-effective so that smaller rehabilitation centers and in-home users can afford to purchase the device. The apparatus122may also have a small footprint (e.g., not requiring excessive space to store or operate). In some embodiments, the apparatus122can be motorized. For example, a motor and/or other actuator can be used to propel a patient's foot through a gait-like trajectory. The motor component can be used to assist patients with low muscular strength. In some embodiments, the apparatus122can be back-drivable. For instance, a gait replication apparatus122can be manually driven without requiring significant effort, which can make it usable as an exercise device. In some embodiments, the apparatus122can also be ergonomic (e.g., not impairing the normal gait motion of the user, and avoiding uncomfortable interferences that may prevent effective rehabilitation). For example, the mechanism can mimic the trajectory of the foot during normal gait and create a comfortable, enjoyable exercise/rehabilitation experience.

A gait-like trajectory may be difficult to replicate mechanically. Without the use of multiple motors, a mechanical device that traces a highly nonlinear path may prove difficult to synthesize. Scaling and back-drivability may further complicate the mechanism. Example approaches for addressing these difficulties include replicating the path using a single, scalable, path-generating mechanism, and parametrizing the path and using multiple systems in tandem to produce the desired output. When using path-tracing mechanisms, one mechanism to drive the motion of the foot can make it far easier to provide back-drivability. Also, the simplicity of such mechanisms can make them more affordable and easier to construct.

In some embodiments, a four-bar (4-bar) linkage144can be used to produce a variety of paths. Several methods can be employed to fit the trajectory to a four-bar linkage144, including nonlinear optimization, consulting a four-bar linkage coupler curve atlas, classical linkage synthesis for rigid-body guidance, and experimenting in simulation software. In some embodiments, best-fit methods for the long, flat shape of the metatarsal trajectory may result in an elliptical shape without a desired flatness. Thus, in order to scale the four-bar linkage144according to design requirements, each individual link may be scaled proportionately. For example, links with changing lengths can be provided using multiple motors. Other closed-loop mechanisms, such as six-bar (6-bar) and/or eight-bar (8-bar) linkages may also be used, allowing higher-order paths closer to a natural gait.

Pantograph100srely on geometrical constraints of similar triangles or parallelograms to produce similar motions at different points on a linkage. A pantograph100design can be generated by tracing the trajectory of the foot (e.g., from a template) and then mapping out an identical (or substantially identical), scaled path for the foot. In one design, two long beams102connect with two shorter beams104to create a scaling mechanism, as shown inFIG. 3. Triangles ABC and ADF are similar. Point A is rigidly attached to the ground, and point F is attached to a foot pedal118. Point C attaches to a pin (Point P) that rolls in a track that matches the gait path. To power the pin through the track, a Cardan gear106can be used, as shown inFIG. 4. Cardan gears106can generate elliptical trajectories with similarities to gait paths. Since the desired path is not a true ellipse, the mechanism can use a sliding connection between Point P and the Cardan gear106. This can allow the pin to follow the gait path and not be constricted to an elliptical trajectory.

However, this pantograph100design is provided by way of example and is not meant to limit the present disclosure. In other embodiments, different pantograph100implementations can be used to generate a gait path. In this manner, accurate gait trajectory tracing can be provided. To obtain scaling, a motor can be used to change link lengths so that the geometric similarities of the triangles can be preserved. In some embodiments, a telescoping pantograph108extends outward, as shown inFIG. 5. Again, point A is rigidly attached to the ground, and point B (116) traces the gait path similar to the embodiment shown inFIG. 3. The foot pedal118is located at point C. In order to scale the motion, point C can be moved to different joints along the pantograph100assembly. This implementation can provide discrete, accurate scaling, although the scaling may not necessarily be linear.

In some embodiments, gait path can be separated into Cartesian coordinates, where each coordinate is a function of time. For example, the X-position and Y-position coordinates of the metatarsal trajectory are separated, and the graphs of these variables are shown inFIG. 6. Both X-position and Y-position coordinates may be highly nonlinear functions of time, but separating the X and Y positions can allow independent mechanisms to be used to control the horizontal and vertical motions of a foot pedal118. This technique may be simpler than constructing a single mechanism that generates the entire path. Scaling in Cartesian coordinates may be cumbersome for this scenario. Thus, in some embodiments, parametrization in polar coordinates can be used. In a parametrized system, one mechanism can control the angular position of a point relative to a fixed reference frame, while another mechanism can control the radial position. With the angle held constant, the radius of an arc and the arc length are linearly correlated, meaning that simple scaling of the radial position scales the entire trajectory. The coordinates are highly sensitive to the location of the origin. If the origin is placed inside the closed loop, the angular position may undergo a complete revolution. If the origin is outside of the loop, the angular position may oscillate. In some embodiments of a parametrized implementation, the origin is located at a point just outside of the loop at a point on the ground. An example trajectory of this configuration is shown inFIG. 7.

In some embodiments, a definition in terms of radial and angular coordinates allows for a parametrically defined, scalable mechanism. As shown inFIG. 8, a beam112(link A) is oscillated up and down by a cam114(link E) about its connection with Link B. This defines the angular position of the beam112. Rotating link B defines the radial position of the foot pedal118(or carriage) (link D), which is sliding along the beam112. By interfacing with the slot120in link C, link B is able to drive the radial position with the offset from zero as seen inFIG. 8. In a linearly-scaled system, the angular position may not necessarily change, and the radial position can be adjusted to produce proportional changes in stride length and trajectory. This may be performed by lengthening or shortening link B, although this may also require adjusting the offset (link C). In some embodiments, this configuration may use simultaneous adjustment of two links (e.g., rotating link B and the offset attached to link C). Further, the apparatus122described with reference toFIG. 8may be back-drivable and ergonomic, and simple geared connections between link B and link E can allow the mechanism to be driven by a single motor110per foot pedal118.

The strengths of the cam/Scotch-yoke mechanism are also used in the implementation described next. In the previous cam/Scotch-yoke mechanism, the offset included in link C was used because the origin of the polar coordinate system defining the angular and radial positions was set on the ground away from the trajectory. If the polar coordinate origin is placed on the trajectory, then no offset is necessarily used. However, if the origin is placed anywhere on the system, it may encounter angles exceeding 90 degrees (90°), where the mechanism would flip orientations. It is possible to place the polar coordinate origin on the gait path if the gait path intersects the origin. In the previous mechanisms described, the gait path is assumed to be the metatarsal trajectory. Both the metatarsal trajectory and the heel trajectory shown inFIG. 2are smooth, cusp- and loop-free paths. However, a different point on the foot may experience a trajectory that is tangent to itself. The bottom of the foot can be defined by a line connecting the metatarsal and the heel. The position of every point on the bottom of the foot can be found using simple interpolation. To find the trajectory of point O on the foot, located on a vector traveling from the metatarsal to the heel, the following equation is used:
{circumflex over (X)}O=(1−p){circumflex over (X)}metatarsal+p{circumflex over (X)}heel
where X is the vector defining the horizontal and vertical position of the trajectory at any time and p is the percent distance from the metatarsal to the heel where the desired point is located on the foot.

Using the above equation, it is apparent that when p=−0.25, the path is tangent to itself at the origin, as shown inFIG. 15. The position of point O, located at −25% of the distance from the metatarsal to the heel, occurs just in front of the toe on the foot. In healthy individuals, the toe joint flexes, causing the toe to diverge from the trajectory shown. If the mechanism accounts for foot orientation, then as long as the foot is placed in the correct location on the foot pedal118, the foot will travel through a gait-like trajectory.

In some embodiments, a gait replication apparatus122includes a beam112rotating about an axis passing proximate to (e.g., through or near) its center128(e.g., Point A), as shown inFIG. 9. The beam112can include two L-shaped channels130separated by a small gap132. A slider134(e.g., foot pedal118) travels along the top of the beam112, and the front-toe position of the slider134can be constrained to the beam112. The slider134can be connected to a chain136coupled with a sprocket138(or a timing belt coupled with a pulley, etc.) that loops around the beam112, which can propel the foot pedal118forward and backward. The chain136can be connected through gears (e.g., rack146and pinion148) to the rocker arm142of a four-bar linkage144. The rocker arm142can rotate at angle θ (theta) relative to the vertical axis, as shown in FIG.9. The oscillations of the rocker arm142may cause the chain136to travel forward and backward along the beam112, with timing matching that of a natural gait.

To scale the radial distance that the foot pedal118travels, the vertical position of the rack146and pinion148can be shifted. Moving the rack146along the rocker bar means that angular rotations of the rocker may result in larger or smaller horizontal displacement of the rack. Because the arc distance and radial distance are correlated, changing the position of the rack's connection to the rocker arm142can linearly scale the motion. The crank150of the four-bar linkage144can be connected through gearing to a cam114that defines the beam's112angular position. The angular position of the beam112(e.g., a first beam), combined with the radial position defined by the chain movement, can create the trajectory seen inFIG. 15. To capture the foot angle, the foot pedal118can be connected to a second beam. The second beam can rotate about Point A with the main beam112, and can be raised and lowered through a cam. The vertical displacement of the second beam may cause the angle of the foot pedal118to change regardless of the position of the foot pedal118. This can make the foot angle motion independent of the scaling.

FIG. 10illustrates one specific implementation of a gait replication apparatus122. In this implementation, the gait replication apparatus122can include a crank-rocker four-bar linkage144, which forms the foundation. A four bar linkage144can include a rocker142(as used herein, rocker arm can be interchangeable with rocker), a crank150, and a connector166(e.g., block166). The block166can be slidable along the rocker142(e.g., the rocker142can include a slot120in which the block166can slide), and the block166can be fixed with a pin168. In one specific embodiment, the block166can be slidable along the rocker142(e.g., and can be fixed with a lead screw nut). In another specific embodiment, the rocker142can include a plurality of holes positioned along the rocker142, where the block166can be fixed to the rocker142using a pin168and one of the plurality of holes. The block166can be coupled to a bar170that is coupled to a carriage124. The carriage124can carry off-axis loading from the four bar linkage144and transmit the loading into longitudinal motion along the pivoting beam112(or rail). At least one cam114drives angular displacement of the beam(s)112, and the cam114rotation can be coupled to the crank150of the four bar linkage144. In this embodiment, the gait replication apparatus122forms a cam-constrained seven-bar linkage with one degree of freedom. The top figure inFIG. 10illustrates a line diagram for power transmission of the gait replication apparatus122.

FIG. 11illustrates one specific implementation of the gait replication apparatus122. Instead of a mobile, pivoting rail as previously described, the rail can include an immobile beam112(F) that the carriage124(E) can travel upon. In this implementation, carriage motion is dictated by a four-bar linkage144(A-B-C). A sliding linkage (D) (e.g., block166) on the rocker142(C) scales the carriage longitudinal movement.

Additionally, different embodiments of a foot pedal118are illustrated inFIGS. 12 through 14. In the embodiment shown inFIG. 12, the foot pedal118includes at least one rod (e.g., bar170) that is connected to the carriage124through a revolute joint174. Two more rods176can be joined to the carriage124using at least one revolute joint174, and the revolute joint174can be configured such that it moves along the foot pedal118. The distance between the two revolute joints can be adjusted to be consistent with the distance between the heel and the metatarsal of a patient.

In the embodiment illustrated inFIG. 13, the foot pedal118includes a pivoting plate178with at least one wheel180attached to the pivoting plate178. Additionally, the foot pedal118includes at least one actuator184disposed between the at least one wheel180and a foot pedal base188. Rotation of the pivoting plate178is lockable when the actuator(s)184is/are activated and pushed into the wheel(s)180, and where the actuator(s)184deactivate and release the at least one wheel180during a swing cycle and allow the pivoting plate178to pivot about the pivot190on the center point. During the swing phase, the actuator(s)184can deactivate, and the pivoting plate178can freely pivot about the center point to the desired foot angle during heelstrike and the desired foot angle during toe off.

In the embodiment illustrated inFIG. 14, the foot pedal118includes a foot plate194with u-groove wheels180attached to it and a curved arc rail192coupled to the carriage124using a locking actuator184. The locking actuator184engages the bottom of the foot plate194and disallows the foot plate194from moving. The actuator184can unlock during the swing phase. The foot plate194can be designed such that the heel and metatarsal can be located equidistant from each of the wheels180on the foot plate194. The center of the curved arc rail can be disposed at a position very near to the ankle, where both the heel and metatarsal pivot about during a normal stride. When the actuator184is unlocked, pressure on the metatarsal (during toe off) causes the rear of the foot to rise. Pressure on the heel (during heel strike) causes the toe of the foot to rise. The fluidity of the foot pedal118encourages a user to engage in natural foot motions.

The four-bar linkage144may be designed to replicate the radial position with respect to time, mimicking normal gait. The radial trajectory of a foot pedal118is shown inFIG. 16. To convert between radial distance and rocker arm142angle, the coordinates can be converted from Cartesian to polar form. The radial movement is directly influenced by the motion of the rack. The rack146is constrained to only move horizontally. From polar coordinates:
x=r*sin(θ)
y=r*cos(θ)=constant
where x is the radial distance of the rack, y is the vertical position of the rack, r is the distance from the rotation point of the rocker arm142to the connection point to the rack, and θ is the angular displacement of the rocker arm142from the neutral position. The y-position is constant here during operation of the machine. Vertical motion of the rack146causes the rack trajectory to scale. Thus, the rack146can be held at a constant height, and the distance r can be variable, dependent on θ. Rearrangement and combination of the equations solves for θ in terms of x and y:

In some embodiments, to limit size while increasing power transmission, the maximum range of x can be chosen to be at least approximately [−25 cm, 25 cm], which may occur at a length of at least approximately fifty-one centimeters (51 cm) from the rocker arm142pivot point. This can be the position of the system when outputting the step length of at least approximately one hundred and two centimeters (102 cm). To synthesize a four-bar (4-bar) linkage144to produce the above output curve, Freudenstein's equation can be used as follows:
R1cos(θ)−R2cos(φ)+R3=cos(θ−φ)
where

R1=dcR2=daR3=a2+c2+d2-b22⁢⁢a⁢⁢c
and where a is the length of the crank150; b is the length of the coupler; c is the length of the rocker arm142; d is the length of the ground link, which is the distance between the fixed pivot on the crank150and the fixed pivot on the rocker; θ is the angle between the crank150and the ground link; and φ is the angle between the rocker arm142and the ground link. Using the trigonometric difference identities, Freudenstein's equation can be rewritten as follows:

Assuming θ to be constant, the φ term can be isolated by combining the sine and cosine terms using linear summation:
R1cos(θ)+R3=Acos(θ−α)
where
A=√{square root over ([cos(θ)+R2]2+sin2(θ))}
α=atan [(cos(θ)+R2)/sin(θ)]
Thus, the equation for the rocker arm angle in terms of the crank angle is given as follows:

R1⁢cos⁡(θ)+R3=cos⁡(θ)⁢cos⁡(φ)+sin⁡(θ)⁢sin⁡(φ)+R2⁢cos⁡(φ)R1⁢cos⁡(θ)+R3=(cos⁡(θ)+R2)⁢cos⁡(φ)+sin⁡(θ)⁢sin⁡(φ)
This equation can be least-squares curve fit to the phi angle calculated from the observed radial displacement of the foot. Constraints can be applied to meet the Grashof conditions for a crank-rocker. Also, to maximize backdrivability and power transmission, the crank150may not be less than at least approximately fifteen centimeters (15 cm) long in some embodiments. As a result, the crank length may be at least approximately fifteen and two-tenths centimeters (15.2 cm), the coupler may be at least approximately thirty-six and five-tenths centimeters (36.5 cm), the rocker arm may be at least approximately twenty-three and two-tenths centimeters (23.2 cm), and the ground link may be at least approximately forty-three and four-tenths centimeters (43.4 cm). The ground link can make at least approximately a minus forty-seven and eight-tenths degrees (−47.8°) angle with the horizontal. Example rocker angles are shown inFIG. 17.

The timing for the four-bar linkage rocker angle can be similar to the desired timing of the radial motion of the foot pedal118. In this manner, the crank rotation speed may be changed without use of a controller, and the crank150can rotate at a uniform angular velocity. Further, cams defining the angular position of the beam112and the vertical position of a secondary beam can be configured directly from displacement requirements (e.g., without consideration for cam rotation speed changes). In some embodiments, to use a roller follower with a cam, no point on the cam pitch curve may have a curvature smaller than the follower radius. With the cams114located halfway between the pivot point of the beam112and the end of the beam112(e.g., at least approximately twenty-five centimeters (25 cm) away), the cams may provide a maximum vertical movement of at least approximately four and four-tenths centimeters (4.4 cm). Example beam angle and cam profiles are shown inFIG. 18.

In some embodiments, a foot orientation rail can be used to define the angle of the foot by rotating the foot pedal118relative to the foot position beam. Foot orientation angle is shown inFIG. 19. After accounting for the rotation of the foot positioning beam, a cam114that defines the motion of the foot orientation beam is shown inFIG. 20. Like the other cam, this cam114can be driven synchronously with the rest of the mechanism. Another cam114is illustrated inFIG. 21.

As described herein, apparatus122that mimic the foot trajectory of normal gait are described. In some embodiments, the apparatus122provides back-drivability, can be powered by a single motor (reducing weight and size), has linear scaling that is easy to adjust, and does not hinder children in a gait training scenario. In some embodiments, the chains136and/or cams can be enclosed (e.g., in a housing) to prevent or minimize contact with patients. In some embodiments, a gait replication apparatus122provides a gait-like trajectory that is adjustable for pediatric or adult users and adjustable for users with different gait lengths for each foot or increased/reduced step height. The apparatus122can be motorized and back drivable so users with poor muscle tone can benefit from the therapy and those with good muscle tone can use it as an exercise or therapy device.

As described herein, a four-bar linkage144can be attached to a rack146and pinion148. Changing the location of the rack146and rocker bar connection effectively changes the gait length of the system. The rack146and pinion148is then attached via a chain136to the foot pedal118, which travels along a beam112, to advance the foot. Cams can be attached to the beam112to add vertical motion in the stride to accurately mimic a gait pattern. A motor can be used to move the foot pedals118by moving the crank arm (e.g., crank150) of the four bar linkage, or the machine can be back driven if the motor is off. In the latter case, the motion of the foot pedal118drives the chain136attached to the rack146and pinion148to move the four bar linkage.

The gait replication apparatus122can be scalable to accommodate individuals with a wide range of step lengths, pediatric to adult. The gait replication apparatus122can be adjustable, with custom adjustment for those with uneven or unusual gait, different lengths for each foot, increased and/or reduced step heights, and so forth. Further, anatomically correct motion that accurately mimics natural gait motion can be provided. The gait replication apparatus122can also be used for assistive/resistive applications, where the equipment can be powered by a motor to varying degrees to fully or partially assist patients and/or can be powered by the user directly.

In some embodiments, gait replication apparatus122can be used for physical therapy and rehabilitation applications, where gait therapy is provided for victims of stroke, nervous system damage, Parkinson's disease, the elderly, or users with generally poor muscle tone, in settings including, but not necessarily limited to: rehabilitation hospitals (e.g., those serving pediatric and adult patients), nursing homes, and so on. Further, the gait replication apparatus122can be used in cardiovascular and exercise equipment applications, e.g., as a general physical fitness and/or cardiovascular exercise device. Similar applications can include elliptical exercise machines, treadmills, and so forth. Further, such apparatus122can be adjustable for use by an entire family.