Stride Emulator Device

Abstract

A stride emulator device for efficiently utilizing force transmitted by a human leg to a rotary drive system, the stride emulator device including a pair of levers, at least two gears, at least two crankshafts with crank arms, and each lever including a cam and a cam track.

Description

[Technical field]

[0001] Priority This application claims priority to U.S. Provisional Patent Application No. 62 / 902,331, filed September 18, 2019. [Background technology]

[0002] The present invention relates to the conversion of linear motion to circular or rotational motion (or vice versa), and in particular to mechanisms for the conversion.

[0003] When walking or climbing, our leg strokes are asymmetrical, and the legs move at different speeds relative to each other. The return movement of the leg in the air is faster than the push to the ground. Thus, the leg strokes overlap, and power is transferred smoothly from one leg to the other without continuous thrust or loss of contact with the ground.

[0004] A common way to convert linear thrust into rotational motion is with a crank. Bicycle cranks are commonly used to capture power from the legs. Unlike walking or climbing, when turning a crank, the legs move at the same speed as each other. This motion is similar to running, where the legs also move quickly at roughly the same speed. While running, the momentum (inertia) of the body moving at a higher speed allows for "air time" so continuous ground contact and overlapping strokes are not required. Similarly, bicycle cranks also rely on inertia from speed and high RPM to get through the "dead" spots of the crank.

[0005] It is well understood that successful cycling depends on a very high cadence or RPM (revolutions per minute). One of the main reasons is the pedal-crank input system. The crank requires high RPM to be efficient due to the intermittent linear power input of the crank. Cycling at lower cadences and slower speeds is inherently inefficient.

[0006] Certain movements and applications require a lower RPM and cannot rely on inertia for efficiency. For example, when climbing a hill, you cannot take advantage of the momentum and rotational inertia from a high forward speed, even though the crank is turning at a high RPM.

[0007] The goal of the present invention is to provide a mechanical system that emulates walking and climbing leg movements and efficiently converts power from such movements into rotation, thereby allowing efficient transfer of power at lower input RPM.

[0008] Another goal of the present invention is to create a bike or exercise machine that efficiently uses or trains slow twitch muscle fibers that operate at lower cadences. Summary of the Invention

[0009] The present invention provides a lever mechanism designed to follow the leg motion of walking or climbing. The lever mechanism is characterized by a power cycle or stroke that is longer than the travel cycle or stroke, i.e., in one "revolution" of the driven gear, power is transmitted to said gear more than 50% of the time. This "overlap" of power strokes allows for a fully linear power input 100% of the time. The path of motion is very similar to leg motion. While pushing, the leg is moving in a straight line. When moving forward, the leg follows an "arc" shape and lifts in the air.

[0010] Each input lever of the stride emulator of the present invention follows such a path or "cycle". When pushing, the leg moves in an approximately straight line. When moving, the leg follows an arc. The stride emulator of the present invention includes two slider cranks that are coupled together (by chains, gears, or other means) so that they always rotate the same amount in the same direction. The crank arms of each slider crank are rotated approximately 180 degrees from each other. Slightly larger or smaller angles are possible depending on the desired input path (simulated trajectory of the leg stroke).

[0011] The two slider cranks themselves rotate 180 degrees relative to each other, since they are connected by a shaft. Thus, the input lever follows the rhythm of walking or climbing. In a simple crank, the linear power stroke is not converted into a rotation purely linearly. However, it is more or less efficient for about 1 / 4 of the rotation. In the stride emulator according to the invention, the linear power stroke is not only converted linearly, but is also efficient for more than 1 / 2 of the rotation.

[0012] More specifically, a stride emulator device is provided, the stride emulator device comprising: a pair of levers including a first lever and a second lever, wherein the first lever includes a first cam track and the second lever includes a second cam track; at least two gears including a distal gear and a central gear; a distal crankshaft disposed on a distal axle of the distal gear and connected to a first distal crank arm, wherein the first distal crank arm is rotatably connected at its distal portion to the first lever, wherein the distal crankshaft is connected to a second distal crank arm, wherein the second distal crank arm is rotatably connected at its distal portion to the second lever; a distal crankshaft disposed on an axle of the central gear; and an intermediate crankshaft in mechanical communication with a first intermediate crank arm, the first intermediate crank arm including a first cam slidably connected to a first cam track, where the intermediate crankshaft is connected to a second intermediate crank arm, and the second intermediate crank arm including a second cam and slidably connected to a second cam track, where the first lever and the second lever are disposed on at least one side of the gear, and where the first distal crank arm and the first intermediate crank arm are offset by a first power arc angle perpendicular to the intermediate axis, and where the second distal crank arm and the second intermediate crank arm are offset by a second power arc angle perpendicular to the intermediate axis.

[0013] Further provided is a stride emulator device having at least one force synchronizer, such as at least one gear, at least one pulley, at least one belt, and at least one chain, whereby when a force is applied to a proximal portion of a first lever, a first pivotal movement is induced in a distal gear, and when a subsequent force is induced in a proximal portion of a second lever after at least partial rotation, a second pivotal movement is induced in the distal gear.

[0014] Further provided is a stride emulator device, wherein the first lever further includes a first lever line, and the first lever line follows along a power variation cycle.

[0015] Further provided is a stride emulator device, wherein the first lever further includes a power-varying cycle including a power phase and a movement phase.

[0016] Object of the invention It is an object of the present invention to provide a lever-actuated gear transmission system for continuous and efficient energy transfer with fixed and variable gear ratios. Specific examples are included in the following description for purposes of clarity, but various details may be changed without departing from the scope of the invention.

[0017] Another object of the invention is to provide a lever actuated mechanism suitable for exercise equipment.

[0018] Another object of the invention is to provide a lever mechanism that converts rotational to walking motion for use in robotics.

[0019] Another object of the invention is to provide a lever mechanism that converts rotational to walking motion for training purposes, similar to a stair climbing machine or treadmill.

[0020] It is another object of the invention to provide a lever drive mechanism adapted for use with other forms of human powered vehicles such as boats, aircraft, etc. It is another object of the invention to provide a lever drive mechanism having a variable gear ratio adapted for powering bicycles.

[0021] Another object of the present invention is to provide a better manual winch.

[0022] It is a further object of the present invention to provide a better pump system.

[0023] Other and further objects of the present invention will become apparent upon a consideration of the following detailed description of the invention or after a practice of the invention. [Brief description of the drawings]

[0024] Preferred embodiments of the invention have been selected for detailed description and are illustrated in the accompanying drawings to enable those skilled in the art to which the invention pertains to readily understand how to make and use the invention. [Figure 1] FIG. 1 is a perspective view of an embodiment of a stride emulator according to the present invention. [Figure 2a] FIG. 2a is a diagram depicting the relative speed of body and leg movements over time. [Figure 2b] FIG. 2b is a diagram depicting the relative speed of body and leg movements over time. [Figure 3a] FIG. 3a depicts a side view of an embodiment of a stride emulator according to the present invention. [Figure 3b] FIG. 3b illustrates a side view of an embodiment of a stride emulator according to the present invention. [Figure 4] FIG. 4 is a conceptual diagram illustrating portions of an embodiment of a stride emulator according to the present invention and a possible path or cycle as a track. [Diagram 5]FIG. 5 depicts a side view of a portion of an embodiment of a stride emulator according to the present invention having an intermediate gear and shown in two positions. [Figure 6] FIG. 6 is a conceptual diagram showing one possible power cycle and the relative positions of the levers of an embodiment of a stride emulator according to the present invention at various points in the cycle during the power and translation phases. [Figure 7a] FIG. 7a is a conceptual diagram illustrating various factors for designing a desired power cycle that may be implemented in an embodiment of a stride emulator according to the present invention. [Figure 7b] FIG. 7b is a conceptual diagram illustrating various factors for designing a desired power cycle that may be implemented in an embodiment of a stride emulator according to the present invention. [Figure 7c] FIG. 7c illustrates a side view of an embodiment of a stride emulator according to the present invention. [Figure 8a] FIG. 8a is a conceptual diagram illustrating various factors for the design of a desired power cycle that may be implemented in an embodiment of a stride emulator according to the present invention having a motion phase to power phase ratio of 60%. [Figure 8b] FIG. 8b is a conceptual diagram illustrating various factors for the design of a desired power cycle that may be implemented in an embodiment of the stride emulator according to the present invention having a motion phase to power phase ratio of 66%. [Figure 8c] FIG. 8c is a conceptual diagram illustrating various factors for the design of a desired power cycle that may be implemented in an embodiment of the stride emulator according to the present invention having a motion phase to power phase ratio of 53%. [Figure 9] FIG. 9 is a side view of an embodiment of a bicycle adapted for use with a stride emulator device according to the present invention, for use by a virtual human user. [Figure 10a] FIG. 10a depicts a side view of an embodiment of exercise equipment adapted for a stride emulator device according to the present invention, with a virtual human user. [Figure 10b]FIG. 10b is a diagram illustrating a side view of an embodiment of exercise equipment adapted for a stride emulator device according to the present invention, with a virtual human user. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] A preferred embodiment of a stride emulator device (100) according to the present invention is shown in Figure 1. The embodiment of the stride emulator device (100) includes a pair of levers (101) including a first lever (102) and a second lever (152). Each lever includes a cam track (104), (154). The cam track may be formed, among other things, as a track attached to the lever, or as a recessed portion extending along the length of the lever, or simply as an opening extending along the length of the lever.

[0026] Additionally, the stride emulator device (100) includes at least two gears, a distal gear (180), a central gear (182), and a distal crankshaft (170). The distal crankshaft is attached to the central part, i.e., the distal axle (181) of the distal gear, so that when the gears rotate, rotational force is transmitted to the crankshaft and vice versa.

[0027] The distal crankshaft (170) is connected to the first distal crank arm (110), which is rotatably connected to the first lever (102) at one end of the lever, such as by using a pivot, a screw, or a revolute joint in the distal portion (106) of the lever. Thus, the distal crankshaft (170) forms a rotational support for one end of the lever, which moves according to the length of the first distal crank arm.

[0028] In addition, the distal crankshaft (170) is connected to the second distal crank arm (160), which is rotatably connected to the second lever (152) at one end of the lever, such as by using a pivot, a screw, or a revolute joint in the distal portion (156) of the lever. Thus, the distal crankshaft (170) forms a rotational support for one end of the lever, which moves according to the length of the first distal crank arm.

[0029] Further, an intermediate crankshaft (190) is provided and is attached to the central or intermediate shaft (181) of the central gear (182) so that as the gear rotates, rotational force is transmitted to the crankshaft and vice versa.

[0030] Additionally, the intermediate crankshaft (190) is connected to the first intermediate crank arm (112), which is rotatably connected to the first cam track (104) by a rotatable support such as a first cam (114). The intermediate crankshaft thus forms a rotary support at the end of the intermediate crank arm of the first lever, where the cam supports, rotates and slides along the first cam track (104) of the first lever depending on the length of the first distal crank arm and the length and position of the first cam track (104). The first intermediate crank arm thus includes a first cam slidably connected to the first cam track, and may alternatively include other means such as a pin, shuttle, or other sliding means of connection.

[0031] Similarly, the intermediate crankshaft (190) is in mechanical communication with a second intermediate crank arm (162) which also includes a second cam (164) slidably connected to the second cam track (154) of the second lever.

[0032] Preferably, each set of levers and associated elements are mirror images of each other. In one embodiment, the first and second levers are located on either side of the gear, but it can be understood that the relative positions of the various elements can be adjusted depending on the intended function of the device, and one skilled in the art can adapt the relative positions, sizes, and combinations of the various elements described herein in accordance with the teachings of the present invention to achieve the intended benefits of such a device according to the present invention.

[0033] For example, in a preferred embodiment of the stride emulator device (100) according to the present invention, the first distal crank arm and the first intermediate crank arm are offset in their initial starting position by a first power arc angle (210) perpendicular to the intermediate or first axial direction (220). The first power arc angle is the difference in angle between the distal and intermediate crank arms. It may be 180°, which is the base position, and may be reduced from 180° to about 70°. For example, in an embodiment where the gears are of the same diameter and are mechanically connected, such as by an intermediate gear (300), (510), or other force synchronizer (300), each gear moves at the same speed, thereby rotating each crank arm at the same speed. In the simplest case, each crank arm may be positioned in the same relative orientation, i.e., they are synchronized. However, to achieve the objectives of the present invention, one skilled in the art may change the starting position and offset one of the crank arms relative to the other, as further described herein.

[0034] Similarly, the stride emulator device includes a second distal crank arm offset by a second power arc (230) perpendicular to the intermediate axis or second axial direction (240).

[0035] A frame (199) may also be provided to support the stride emulation device (100) and provide a framework within which the gears rotate, and may be connected to other elements of a bicycle, exercise machine, or other machine upon which one of ordinary skill in the art may wish to utilize the features of the present invention.

[0036] FIG. 2a is a diagram representing the relative velocities of body motion and foot motion over time as a way of illustrating the benefits of the present invention. In the first phase of the stride, the foot provides constant power to the body over time as it is in contact with the ground and can be represented as Vb-Vf. In the second phase, where the foot is lifted and forward and then returned as a stride, this is the "moving" phase, no work is being done and the foot needs to be reset before the stride to provide more power. In this conceptual diagram, the amount of lost opportunity to transfer power is 40%, but can vary greatly. Thus, this diagram is not intended to convey more than the concepts behind the present invention.

[0037] Similarly, FIG. 2b is a diagram of the relative velocity of body and foot motion over time, showing multiple consecutive strides. During each stride, power is transferred uninterrupted, but there is overlap where power is wasted. Again, this is a conceptual diagram, and while the overlap is shown as 10%, it can vary significantly. Thus, this diagram is not intended to convey more than the concepts behind the invention.

[0038] Figures 3a and 3B are side views of an embodiment of a stride emulator according to the present invention. In this embodiment, a chain (300) is provided to connect two gears as a force synchronizer (300). These two figures are intended to show the movement of the lever at different points in the cycle during use. For example, in Figure 3a, the lever is in a position where each crank arm is offset by a first power angle (210) measured by the angle between the middle crank arm line (212) and the distal crank arm line (214). It will be appreciated that the proximal portion (116), (166) of the lever (102) is in two different positions depending on where in the cycle the stride emulation device is provided. It will be appreciated that as each gear rotates, each crank arm induces the lever to move in a particular cycle.

[0039] FIG. 4 is a schematic diagram showing a portion of an embodiment of a stride emulator according to the present invention and a possible path or cycle that the proximal portion (116), (166) of the lever (102) may follow. More generally, the lever lines (118), (168) trace a cycle, i.e., a power modified cycle (200), as shown in the figure. The shape of the cycle depends on many factors, including, among others, the relative lengths of each crank arm (110), (112), (160), (162) and the gear separation. In one embodiment of the present invention shown in FIG. 4, the power modified cycle (200) has an outwardly curved or convex movement phase (280) portion and a concave or inwardly curved power phase (260). In this schematic diagram, the lever lines (118), (168) are shown as intangible extensions of the material lever arms that may be used.

[0040] FIG. 5 shows a side view of a portion of an embodiment of a stride emulator according to the present invention, shown with an intermediate gear (510) and with two levers (102), (152). In a preferred embodiment with two levers, the stride emulation device according to the present invention is adapted to provide an offset position for each lever. For example, in an embodiment of a stride emulator device adapted for a bicycle, the embodiment may include a left pedal and a right pedal that are intermittently pressed to drive the gears. The first distal crank arm (110) is offset 180° from the second distal crank arm (160), and the first intermediate crank arm (112) is offset 180° from the second intermediate crank arm (162). Rather than pushing the pedals a full revolution, the user of the device intermittently pushes and pulls the first lever and then the second lever back and forth, which allows for a very efficient transfer of energy to the gears that can be utilized to drive the machine.

[0041] 6 is a schematic diagram showing one possible power cycle (200) and the relative positions of the levers of an embodiment of a stride emulation device (100) according to the present invention at various points around the cycle (200) during the power (260) and travel phases (280). The schematic diagram is not to scale and shows where the levers are located at each point along the power and travel phase curves. It will be appreciated that the shape of the power modified cycle (200) will vary depending on the configuration selected by one skilled in the art to which the invention pertains for a particular embodiment.

[0042] This figure shows a possible cycle (200) of one embodiment of the stride emulator. In this path, each point on the path represents 1 / 15 of a rotation of the output crank. In FIG. 6, some points in the power phase (260) are close to a straight line, and the distance between each adjacent point is similar. This means that the same amount of linear input from these points will cause the same amount of rotation of the output crank. The arched path of these points on the travel phase (280) shows the acceleration and deceleration of the lever on the travel stroke. In this particular example, the travel stroke is about half the time of the power stroke. It can be seen that if both lever arms are connected to a crankshaft, an overlap of power strokes can occur, allowing power to be transferred from one input lever to the other.

[0043] The ratio of power to travel stroke is determined by the pivot location of the cranks and the distance between the cranks. Several arrangements are possible depending on the amount of overlap desired and the desired shape of the stroke. Additionally, the angle between the two cranks can be slightly offset, resulting in a slightly asymmetric path. The length of the lever arm further affects the shape of the path. Additionally, by extending the lever arm in the opposite direction, the shape of the path can be changed so that the power segment is in an arc and the travel segment is more linear. Alternatively, if the cam track extends to the second crank, a locking mechanism such as a cam lock (530) (shown in FIG. 5) can alternatively lock the front or rear crank, allowing it to switch between a mode that emulates walking and a mode that emulates a movement such as skating or jumping, where the leg push is faster than the forward movement. By changing the shape of the cam track, it is also possible to further control the path so that it is not perfectly linear and non-linear, such as an arc. Additionally or alternatively, embodiments of the emulator device (100) according to the present invention may include a mid-arm shift (540) and a distal arm shift (520) for changing the power cycle (200) on the fly. The mid-arm shift (540) and the distal arm shift (520) may be provided as telescoping arms that change length when a signal is provided from a gear shift (not shown) or may be set and adjusted manually prior to use. The mid-arm shift (540) and the distal arm shift (520) should shift in length in complementary directions to prevent excessive strain on the force synchronizer (300).

[0044] 7a, 7b, and 7c are side views of an embodiment of a stride emulator according to the present invention, along with a conceptual diagram illustrating various factors for designing a desired power cycle that can be implemented in an embodiment of a stride emulator according to the present invention to assist one of skill in the art in selecting a desired configuration having particular power cycle (200) characteristics for a selected embodiment.

[0045] As shown in Figures 7a, 7b, and 7c, where the linear extensions (118), (168) of several levers intersect, an imaginary focal point (700) is provided. For example, starting from a single gear having a distal shaft (181) and a specific lever arm length that defines the diameter of travel of the distal portions (106), (156) of the levers, as shown in Figure 7a, the focal point (700) is defined by the tangent at two points that provide the farthest extent of the power change cycle when tracing an arcuate path.

[0046] Providing a second lever arm and cam track in FIG. 7b provides additional constraints and provides definition to the arcuate path of the power change cycle (200).

[0047] Thus, when designing a machine to utilize a power modified cycle, one can return to the desired configuration of the stride emulation device (100) by first selecting the lever length and / or lever line extension (118), (168) and secondly selecting the desired power modified cycle characteristics (200). For example, a bicycle can be designed for individuals with short or long leg lengths or strides, thereby providing an optimal system tailored to that particular individual to most efficiently transfer power to the device.

[0048] It will be appreciated by those skilled in the art that various power variation cycles are possible and that the power to displacement ratios will vary depending on the particular application. Accordingly, Figures 8a, 8b, and 8c are conceptual diagrams illustrating various factors for designing a desired power cycle that may be implemented in an embodiment of a stride emulator according to the present invention having displacement to power ratios of 60%, 66%, and 53%.

[0049] It is within the scope of the present invention that several stride emulation devices may be used to emulate gear shifting for a more powerful system. For example, a first power-change cycle (200) of a first stride emulation device (100) may be adapted for use with an additional stride emulation device (1000) and its associated additional power-change cycle (2000), whereby a step-up in power may be achieved by shifting from one gear system to another. For example, in an alternative embodiment, a device (100) having a first configuration as shown in FIG. 3a may be connected to a further device having a second configuration as shown in FIG. 3b. Each device would have a different configuration, i.e., gear size focal position, lever length, etc., and thus, in combination, obtain a new and unique power cycle (200).

[0050] Figure 9 is a side view of an embodiment of a bicycle (910) fitted with a stride emulator device according to the present invention by a virtual human user. The bicycle is fitted where the stride emulator (100) replaces a conventional crank as a means of power input. In this figure, a series of chains are shown connecting one of the stride simulator's cranks to the rear wheel. It can be appreciated that other means of transmitting power to the front wheel are also possible. Additionally, it is possible to use the stride emulator mechanism as a means of synchronizing inputs rather than harvesting rotational outputs.

[0051] 10a and 10b are diagrams depicting side views of an embodiment of exercise equipment (1010) adapted for a stride emulator device according to the present invention with a virtual human user.

[0052] Different applications of the present invention include training or exercise equipment, pumps, folding bikes, cargo bikes, watercraft, among others.

[0053] Various modifications may be made to the structure embodying the principles of the present invention. The foregoing embodiments have been set forth in an illustrative, not a limiting sense. The scope of the present invention is defined by the claims appended hereto.

Claims

1. A stride emulator device, comprising: a pair of levers including a first lever and a second lever, wherein the first lever includes a first cam track and the second lever includes a second cam track; at least two gears including a distal gear and a central gear; a distal crankshaft disposed on a distal axle of the distal gear and in mechanical communication with a first distal crank arm, wherein the first distal crank arm is rotatably connected at a distal portion thereof to the first lever, and wherein the distal crankshaft is in mechanical communication with a second distal crank arm, wherein the second distal crank arm is rotatably connected at a distal portion thereof to the second lever; an intermediate crankshaft disposed on an intermediate shaft of a central gear and in mechanical communication with a first intermediate crank arm, wherein the first intermediate crank arm includes a first cam slidably connected to the first cam track, wherein the intermediate crankshaft is in mechanical communication with a second intermediate crank arm, and wherein the second intermediate crank arm includes a second cam and is slidably connected to the second cam track; wherein the first lever and the second lever are disposed on at least one side of the gear; and wherein the first distal crank arm and the first intermediate crank arm are offset by a first power arc angle perpendicular to the intermediate axis; and wherein the second distal crank arm and the second intermediate crank arm are offset by a second power arc angle perpendicular to the intermediate axis; the first power arc angle and the second power arc angle range from 0 degrees to 360 degrees; the first lever has a proximal portion at an end opposite to the distal portion that extends beyond the first cam track, the proximal portion being adapted to receive a pedal when the stride emulator device is used on a bicycle; a proximal portion of the second lever at an end opposite to the distal portion extends beyond the second cam track, the proximal portion being adapted to receive a pedal when the stride emulator device is used on a bicycle.

2. 2. The stride emulator device of claim 1, further comprising at least one force synchronizer selected from the group consisting of at least one gear, at least one pulley, at least one belt, and at least one chain, whereby when a force is applied to a proximal portion of a first lever, a first rotational motion is induced in the distal gear, and when a subsequent force is induced on a proximal portion of a second lever after at least partial rotation, a second rotational motion is induced in the distal gear.

3. The stride emulator device of claim 1 , wherein the first lever further includes a first lever line, and the first lever line follows along a power modified cycle.

4. The stride emulator device of claim 1 , wherein the first lever further includes a power modified cycle, wherein the power modified cycle includes a power phase and a translation phase.

5. The stride emulator device of claim 4 , wherein the powered phase has a smaller curvature than the translational phase.

6. 6. The stride emulator device of claim 5, wherein the power phase has a linear characteristic and the translation phase has an arcuate characteristic.

7. 2. The stride emulator device of claim 1, wherein a first power phase of the first lever overlaps with a second power phase of the second lever by an amount selected from the range of 3 to 16 percent.

8. 2. The stride emulator device of claim 1, wherein the length of the movement phase is selected from an amount of 10 to 30 inches.

9. 3. The stride emulator device of claim 2, wherein the at least one force synchronizer includes an intermediate gear in mechanical communication with the distal gear and the central gear, wherein a force transmitted from the distal gear to the intermediate gear is further transmitted to the central gear.

10. The stride emulator device of claim 1 , wherein the first power arc angle is selected from an angle within a range of 0 degrees to 120 degrees.

11. The stride emulator device of claim 1 , wherein the first distal crank arm and the second distal crank arm are offset 180 degrees in a second axial direction.

12. The stride emulator device of claim 1 , wherein the first intermediate crank arm and the second intermediate crank arm are offset 180 degrees in a second axial direction.

13. The stride emulator device of claim 1, wherein the lever arm passes through a focal point located between the first distal axis and the intermediate axis and, in its farthest open position, exhibits a tangent to the second crank arm.

14. The stride emulator device of claim 1 , wherein the first lever includes a cam lock.

15. The stride emulator device of claim 4 , wherein the power modified cycle is asymmetric.

16. 2. The stride emulator device of claim 1, wherein the first distal crank arm includes a distal arm shift and the first intermediate crank arm includes a intermediate arm shift (540).

17. The stride emulator device of claim 1 , wherein the cam track is linear.

18. The stride emulator device of claim 1 , wherein the cam track is arcuate.

19. The stride emulator device of claim 1 , wherein the cam track is non-linear.

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