Powered prosthetic ankle

Abstract

A prosthetic foot may include a powered ankle joint. The prosthetic foot may include an attachment with multiple connection portions for connecting to a plurality of flexible foot members. The ankle may be powered by a motorized actuator, which may provide control of the ankle stiffness in parallel to the mechanical functions of the plurality of flexible foot members. The prosthetic foot may function with or without the actuator being powered.

Description

OSSUR.236WO PATENTPOWERED PROSTHETIC ANKLEBACKGROUNDField

[0001] The present application relates to prosthetic feet and more particularly to prosthetic feet including a motorized actuator at an ankle joint.Description of the Related Art

[0002] Conventional prosthetic feet may include an attachment member that can couple the prosthetic foot to a user’s lower limb or another prosthetic device at one end and coupled to one or more flexible foot members at the other end.SUMMARY

[0003] In the area of prosthetic feet, it is desirable that the prosthesis provides stability throughout the gait cycle and in other activities (e.g., stance, ascent, descent, etc.), as well as in different terrains (e.g., slope, ramp, stairs, uneven surface). The present disclosure includes embodiments of a prosthetic foot including a motorized actuator at an ankle joint. The motorized actuator may be coupled to one or more flexible foot members directly or indirectly with a transmission mechanism such that control by the actuator may be in parallel with the mechanical functions the one or more flexible foot members if there were no motorized actuator at the ankle joint or when the motorized actuator is not powered. Embodiments of the prosthetic foot disclosed herein may provide one or more of the following advantageous and / or other benefits: variable and / or controlled stiffness, assisted guided rollover (e.g., tibial progression assist), assisted toe lift during swing (dorsiflexion), assisted plantarflexion, active push-off energy, and / or energy harvesting during loading of the flexible foot members.

[0004] The present disclosure provides a prosthetic foot with a powered ankle joint. The prosthetic foot may include an attachment member including a connector configured to connect to a user or another prosthetic device. The prosthetic foot may further include a first flexible foot member coupled to the attachment member at a first pivot and a second flexible foot member coupled to the attachment member at a second pivot via an elongate link. The elongate link may be coupled to the second pivot at a first end of the elongate link and coupled to the second flexible foot member at a second end of the elongate link. The prosthetic foot may further include a powered actuator located within the attachment member. An output center of the powered actuator may be coupled via a torquetransmission mechanism to a proximal end of the first flexible foot member. The powered actuator may be configured to output a torque to control a stiffness of the ankle joint. The prosthetic foot may include an angle sensor located at the first pivot and a load cell located in the attachment member below the connector. The prosthetic foot may further include a control system configured to determine a desired torque value of the powered actuator based at least in part on input from the angle sensor and the load cell. A torque output of the powered actuator may be configured to cause a first force on the first flexible foot member and a second force on the second flexible foot member, and wherein the first force and the second force may be in opposite directions.

[0005] In some aspects, the control system may be configured to apply an impedance equation to determine the desired torque value for the powered actuator to achieve a desired angle and / or position of the ankle joint.

[0006] In some aspects, the control system may be further configured to adjust stiffness gain or the desired angle and / or position of the ankle joint of the impedance equation based on detected user activity and / or terrain.

[0007] In some aspects, the prosthetic foot may further include a third flexible foot member located below the second flexible foot member and coupled to the first and second flexible foot members. The second force on the second flexible foot member may be configured to change a stiffness or angle of the third flexible foot member.

[0008] In some aspects, the second force may be imparted on the second flexible foot member by the elongate link.

[0009] In some aspects, the load cell may be configured to provide ground contact sensing.

[0010] In some aspects, the load cell may be further configured to provide heelload and / or toe-load measurements.

[0011] In some aspects, the powered actuator may be configured to dorsiflex and / or plantarflex the ankle joint.

[0012] In some aspects, the powered actuator may be configured to assist in roll over of the ankle joint by setting a desired torque value that provide tibial progression assist.

[0013] In some aspects, the actuator may be further configured to increase the stiffness of the ankle joint to provide push off energy.

[0014] The present disclosure provides a prosthetic foot with a powered ankle joint. The prosthetic foot may include an attachment member including a first connection portion configured to connect to a user or another prosthetic device. The prosthetic footmay further include a first flexible foot member. A proximal end of the first flexible foot member may be connected to a second connection portion of the attachment member. The prosthetic foot may further include a second flexible foot member. A proximal end of the second flexible foot member may be connected to the attachment member via a third connection portion and a fourth connection portion. The second flexible foot member may be located below the first flexible foot member. The prosthetic foot may further include an elongate link extending between and coupled to the third and fourth connection portions. The prosthetic foot may further include a third flexible foot member located below the second flexible foot member and coupled to the first and second flexible foot members at proximal ends of the first and second flexible foot member such that the first, second, and third flexible foot members may be operably coupled to the attachment member. The prosthetic foot may further include a powered actuator located in an actuator housing of the attachment member. The prosthetic foot may further include a plurality of connectors connected in series with a first free end at a first connector and a second free end at a last connector. The first free end may be coupled to an output center of the powered actuator and the second free end may be coupled to the proximal end of the first flexible foot member, such that a torque at the output center of the powered actuator may be configured to cause a rotation of the ankle joint.

[0015] In some aspects, the plurality of connectors may be located on medial and lateral sides of the powered actuator.

[0016] In some aspects, the plurality of connectors may be located on a sagittal plane of the prosthetic foot.

[0017] In some aspects, a first force applied on the first flexible foot member due to a torque applied by the powered actuator may be configured to be countered by a second force applied on the second flexible foot member by the elongate link, the first force and the second force being in opposite directions.

[0018] In some aspects, the prosthetic foot may further include an angle sensor located at the second connection portion.

[0019] In some aspects, the prosthetic foot may further include a load cell located at the attachment member below the first connection portion.

[0020] In some aspects, the load cell may be configured to provide ground contact sensing.

[0021] In some aspects, the load cell may be configured to provide heel-load and / or toe-load measurements.

[0022] In some aspects, the prosthetic foot may further include a control system configured to control a stiffness of the ankle joint via impedance control.

[0023] In some aspects, the control system may be configured to apply an impedance equation to determine a desired torque value for the powered actuator to achieve a desired angle and / or position of the ankle joint.

[0024] In some aspects, the control system may be further configured to adjust stiffness gain or the desired angle and / or position of the ankle joint of the impedance equation based on detected user activity and / or terrain.

[0025] In some aspects, a control of the ankle joint via a torque output of the powered actuator may be independent of rotation of the ankle joint due to loading of the first, second, and / or third flexible foot members during ambulation.

[0026] In some aspects, the powered actuator may be configured to be not powered during ambulation, and wherein loading of the first, second, and / or third flexible foot members during the ambulation may be configured to turn a motor of the powered actuator.

[0027] In some aspects, energy from turning of the motor may be configured to be harvested by energy harvesting electronics.

[0028] In some aspects, the plurality of connectors may be distinct from the first, second, or third flexible foot members, or the attachment member.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] These and other features, aspects, and advantages of the invention disclosed herein are described below with reference to the drawings of preferred embodiments, which are intended to illustrate and not to limit the invention. Additionally, from figure to figure, the same reference numerals have been used to designate the same components of an illustrated embodiment. The following is a brief description of each of the drawings.

[0030] Figure 1 is a side view of an embodiment of a prosthetic foot disclosed herein.

[0031] Figure 2 is a rear perspective view of the prosthetic foot of Figure 1.

[0032] Figure 3 is a front perspective view of the prosthetic foot of Figure 1.

[0033] Figure 4 is a side view of an embodiment of a prosthetic foot disclosed herein.

[0034] Figure 5 is an opposite side view of the prosthetic foot of Figure 4 with a cover over a rear link removed.

[0035] Figure 6 is a rear perspective view of the prosthetic foot of Figure 4.

[0036] Figure 7 is a top perspective view of the prosthetic foot of Figure 4.

[0037] Figure 8 is a front view of the prosthetic foot of Figure 4.

[0038] Figure 9 is a rear view of the prosthetic foot of Figure 4.

[0039] Figure 10 is a top view of the prosthetic foot of Figure 4.

[0040] Figure 11 is a bottom view of the prosthetic foot of Figure 4.

[0041] Figure 12 is a block diagram illustrating input and output of a control system (e.g., an impedance controller) of the prosthetic foot disclosed herein.DETAILED DESCRIPTION

[0042] Several embodiments of a prosthetic foot with a powered ankle may provide variable stiffness control achieved by changing the impedance of the ankle. For example, the impedance of the ankle may be calculated using an impedance equation. This control allows the stiffness of the prosthetic foot to be adjusted for different types of gait phases, gait subphases, and terrains and / or activities. The variable stiffness control can be automatically adjusted based on position and / or velocity inputs sensed with one or more sensors on the prosthetic foot disclosed herein, which may be inputted into the impedance equation. In some embodiments, the variable stiffness control may be combined and / or supplemented with (e.g., limiting or enhancing) other stiffness control features (e.g., by varying a gap between adjacent flexible foot members to change the stiffness of the prosthetic foot). In some embodiments, the variable stiffness control disclosed herein can be automatically or actively adjusted during ambulation by the user, e.g., based on the activity level of the user or the phase of gait cycle. These activity levels and / or phases of gait cycle may be indicated by the position and / or velocity inputs sensed with the one or more sensors disclosed herein.

[0043] Several embodiments of a prosthetic foot with a powered ankle may provide improved stability. For example, the powered ankle may provide smoother (e.g., guided) rollover throughout the gait cycle, in other activities such as stance, and in various terrains. The powered ankle may assist the user in rolling over the ankle by impedance control to pull the user forward (that is, providing assistance). In some embodiments, the powered actuator may dorsiflex the ankle, for example, during the swing phase to clear the ground by facilitating a toe life. In some embodiments, the powered actuator may plantarflex the ankle, for example, during an early stance phase in ramp descent to increase balance with an earlier foot flat phase. In some embodiments, the powered actuator may increase the stiffness of the ankle using impedance control to facilitate push off.

[0044] In some implementations, during movement the prosthetic foot disclosed herein may harvest energy. Advantageously, the energy harvesting features may reduce or eliminate the need to charge a battery in the prosthetic foot.

[0045] The prosthetic foot disclosed herein can include one or more flexible foot members, an attachment member, and an actuator for modifying the stiffness of the ankle. The attachment member can include a connector configured to connect the attachment member to a user’s lower limb or another prosthetic device (e.g. a lower limb prosthetic device with a knee joint). In one embodiment, the attachment member or adapter can be located generally at a location associated with a natural human ankle and provide for motion similar to that of a natural human ankle.

[0046] The actuator may be coupled to the attachment member. The active actuator that can be selectively actuated (e.g., via an electric controller) to impart mechanical motion to the prosthetic foot (e.g., to change the orientation of the prosthetic ankle during a swing phase of gait cycle to dorsiflexion and then to pl antarfl exion). When the actuator is selectively powered, the actuator may provide any of the functions disclosed herein. When the actuator is not powered, the prosthetic foot, including the one or more flexible foot members may function as disclosed in U.S. Patent Publication No. 2015 / 0328020 Al, the disclosure of which is incorporated by reference in its entirety and should be considered part of the specification. Accordingly, the controlled actuator functions can be parallel to the mechanical functions of the flexible foot members, either limiting or enhancing the mechanical functions and the movement associated therewith.

[0047] The one or more flexible foot members may be coupled to multiple attachment points to provide improved control and stability. In some embodiments, the prosthetic foot can include a bottom flexible foot member extending between a heel end and a toe end. The prosthetic foot may further include an intermediate flexible foot member disposed above the bottom flexible foot member and extending between a proximal end and a distal end. The prosthetic foot can also include a link member extending between and interconnecting the proximal end of the intermediate flexible foot member and the attachment member, the link member pivotally coupled to the proximal end of the intermediate flexible foot member. In some embodiments, the prosthetic foot can also include a top flexible foot member disposed above the intermediate flexible foot member extending between a proximal end and a distal end. The top flexible foot member may include a split that extends from the proximal end to the distal end to divide the top flexible foot member into a medial blade portion and a lateral blade portion. The adapter membermay be pivotally coupled to the medial and lateral blade portions at the proximal end of the top flexible foot member to thereby facilitate a medial-lateral and / or a twist movement of the prosthetic foot during stance when the bottom flexible foot member is in contact with a support surface.

[0048] Figures 1-3 depict an embodiment of a prosthetic foot 100 disclosed herein. The prosthetic foot can attach to a user or to another prosthetic device with an attachment member 102. The attachment member 102 is depicted as including a first connection portion 104 shown as a pyramid connector. The attachment member 102 can attach to a stump on a user, to another prosthetic device, or to any other appropriate object. The first connection portion 104 can include other attachment features such as a threaded hole or screw, a latch, a magnetic member, tube clamp, or other features.

[0049] In some embodiments the attachment member 102 can a load cell 106. The load cell 106 may be configured to measure, for example, ground contact and / or heelload and toe-load. The load cell 106 may be located below (e.g., directly below or aligned vertically when the prosthetic foot 100 is at rest on a flat surface) the first connection portion 104. In some embodiments, the load cell 106 may include configurations and / or features as disclosed in U.S. Patent No. 8,555,715B2, or U.S. Patent. Publication No. 2022 / 0401236A1, the disclosure of each of which is incorporated herein by reference and should be considered part of the specification.

[0050] The prosthetic foot 100 can include an actuator 112. In some embodiments, the actuator 112 can be protected by an actuator housing 122. In some embodiments, the actuator housing 122 may be part of the attachment member 102. In some embodiments, the actuator housing 122 can be located below the load cell 106. In some embodiments, the output center 110 of the actuator 112 may be located anterior of the first connection portion 104. In other embodiments, the output center 110 of the actuator 112 may be vertically aligned with a center of the first connection portion 104, or being posterior of the first connection portion 104.

[0051] The actuator 112 can include a powered actuator 112. The prosthetic foot 100 can include a power source (e.g., a rechargeable battery or the like) to power the actuator 112. The actuator 112 can include a motor. In some embodiments, the actuator can include a gear to enhance the torque. The gear can have different gear ratios and / or be of a different design, (e.g., as a Harmonic Drive, Planetary Gear, or other type of an axial gear box).

[0052] The first, second, and third flexible foot members 116, 118, 120 can be attached, directly or indirectly, to the actuator 112, as described elsewhere in the present disclosure. In parallel with control from the actuator 112, the first, second, and third flexible foot members 116, 118, 120 can be attached, directly or indirectly, to the attachment member 102 at connection points to provide mechanical functions of the first, second, and third flexible foot members 116, 118, 120.

[0053] The attachment member 102 can additionally include second and third connection portions 114, 125. The attachment member 102 can provide a rigid connection between the connection portions 104, 114, 125. For example, the attachment member 102, which may include the actuator housing 122, can include a substantially rigid material such as aluminum, steel, titanium, other metals or metallic alloys, carbon fiber, composites, or substantially rigid plastics. However, in other embodiments the attachment member 102 can be configured to provide flexibility, potentially in multiple planes. Thus, in some embodiments the attachment member 102 can comprise a more flexible material or include flexible joints between separate components of the attachment member 102. For example, in some embodiments the attachment member 102 can have a flexible connection with the first connection portion 104, allowing for motion in the medial / lateral and / or anterior / posterior directions. Further, the connection may allow torsional flexibility with the first connection portion 104. In other embodiments, the attachment member 102 can have a flexible connection with one or both of the second and third connection portions 114, 125.

[0054] The second connection portion 114 may be located below (e.g., directly below the output center 110, or slightly posterior to or anterior to the output center 110) the actuator 112. The attachment member 102 can be coupled to the first flexible foot member 116 at the second connecting portion 114. A brace 115 can connect to or be mounted on (e.g., clamped to, bolted to) a proximal portion 134 of the first flexible foot member 116 such that the first flexible foot member 116 can pivot at the second connection portion 114. The brace 115 may include a flexible material. As shown in Figure 1, the brace 115 may include a right angle in a side view. In some embodiments, the first flexible foot member 116 can be rotatably connected to the second connection portion 114. In some embodiments, the second connection portion 114 can further include an angle sensor 128.

[0055] The third connection portion 125 may be located below the first connection portion 104, such as being posterior to the output center 110 of the actuator. The third connection portion 125 may align horizontally with the output center 110, orslightly above or below the output center 110 when the prosthetic foot 100 is at a resting position on a flat surface. In some embodiments, the second connection portion 114 is in front of the actuator housing 122, and the third connection portion 125 is rear to the actuator housing 122. Like the second connection portion 114, the third connection portion 125 can be rotatable or non-rotatable.

[0056] A rear link 126 at its first end can be coupled to the attachment member 102 at the third connection portion 125. The rear link 126 can be elongate and can extend generally vertically such that a second end of the rear link 126 can be coupled to the second flexible foot member 118 at a fourth connection portion 131. In some embodiments, the fourth connection portion 131 may include a brace that can mount around (e.g., over) a proximal end of the second flexible foot member 118. The brace may include a flexible foot member. As shown in Figure 1, the brace can have a C-shape or U-shape in a side view, with an opening that receives the second flexible foot member 118. The second, third, and / or fourth connection portions 114, 125, 131 may each include a shaft, axel, or pin.

[0057] The rear link 126 can be in a variety of forms and can be operated in a variety of ways, as described by way of example in U.S. Patent Publication No. 2015 / 0328020 Al. For example, the rear link 126 can include a powered actuator such as a screw motor, or a passive member such as a flexible foot member (e.g., a spring) or a chamber with a magnetorheological fluid, or can be a hydraulic or pneumatic system. In some embodiments, the rear link 126 can have an electric motor. The electric motor can have a power between approximately 60W and 100W). Figure 5 illustrates the rear link126 with an outer cover removed. As shown, the rear link 126 may be adjusted in length. In the illustrated embodiment, the rear link 126 may include an adjustable screw member127 such that rotation of the screw member 127 may adjust the length of the rear link 126. In other embodiments, the rear link 126 may include an electronically controlled rear link. In some embodiments, the length adjustment may be motorized. In some embodiments, the length adjustment may be controlled by a control system or processor of the prosthetic foot 100.

[0058] Turning next to the connection of the actuator 112 to the first, second, and third flexible foot members 116, 118, 120, the flexible foot members may function under control of the actuator 112 in parallel with (e.g., independently and / or in combination with) the mechanical functions of the first, second, and third flexible foot members 116, 118, 120. As shown, a shaft or axel may extend through the output center 110 of theactuator 112 on both lateral sides of the actuator 112. Two torque arms 108 may be mounted, at one end of the torque arm 108, onto the output center 110 at the medial and lateral sides of the actuator 112 or the prosthetic foot 100, respectively. The opposite end of each torque arm 108 may connect to one end of a connection rod 124 on the lateral or medial side of the actuator 112. The opposite ends of the connection rods 124 may in turn connect to one end of lever forks 130. The opposite ends of the lever forks 130 may be connected rigidly (non-rotationally) to the first flexible foot member 116 at the proximal portion 134. The connections among the output center 110, the torque arm 108, the connection rod 124, and the lever fork 130 may be rotational connection such that the torque arm 108, the connection rod 124, and the lever fork 130 may be moving connectors.

[0059] The actuator 112 may pivot via the first connection portion 114 on the first flexible foot member 116 with a measured angle. Each set of the moving connectors (e.g., the torque arm 108, connection rod 124, and the lever fork 130 on either the medial side or the lateral side of the prosthetic foot 100) may be connected in series, with the two free ends at the torque arm 108 and the lever fork 130, respectively, hinged to fixed bases (i.e., the output center 110 of the actuator 112 and the proximal portion 134 of the first flexible foot member 116, which in turn is pivoted at the second connection portion 114 of the attachment member 102). Here, moving and fixed may be relative to the attachment member 102. As a result, the torque output at the output center 110 may be transmitted to rotation of the first flexible foot member 116 at the second connection portion 114. In some embodiments, the torque arm 108, connection rod 124, and the lever fork 130 may include rigid components. In some embodiments, one or more of the torque arm 108, connection rod 124, and the lever fork 130 may include an elastic member. As shown, none of the links disclosed herein forming a transmission mechanism between the actuator and the flexible foot member(s) may include any of the flexible foot members, or the attachment member.

[0060] The flexible foot members 116, 118, 120 can each be formed from a sufficiently flexible material such as carbon fiber, though other suitable materials or combination of materials can be used (e.g., carbon and glass fibers, polymers, polymer- fiber composites). In some embodiments, one or more of the flexible foot members 116, 118, 120 can be foot plates (e.g., generally planar or flat, or have a generally rectangular transverse cross-section).

[0061] In some embodiments, the first flexible foot member 116 can be formed into a shape configured to provide a desired flexibility or rigidity. For example, the firstflexible foot member 116 can include a C-shaped portion. In some embodiments, the C- shaped portion can bend more than 90 degrees, more than 110 degrees, 130 degrees, 150 degrees, or 170 degrees when unloaded. The bend of the C-shaped portion can affect the resistance or flexibility of the first flexible foot member 116. This resistance or flexibility can be adjusted, as described herein. In other embodiments, the proximal portion 134 of the first flexible foot member 116 can have other suitable shapes, such as generally L- shaped or angled relative to a toe portion of the prosthetic foot. The first flexible foot member 116 can extend from the lower end of the proximal portion 134 into a foot portion terminating at a distal end. The foot portion of the first flexible foot member 116 can be substantially flat or sloped downward. In the illustrated embodiments, the first flexible foot member 116 can include a split 146 (see Figure 3) extending along at least a portion of the length of the first flexible foot member 116 from the distal end of the first flexible foot member 116 toward the proximal portion 134. The split 146 may allow medial and lateral portions of the first flexible foot member 116 to flex, to a certain extent, independently of each other and to promote a more natural roll-over during ambulation. The split 146 of the first flexible foot member 116 can be aligned with a straight portion of a split 146 (see Figure 11) in the third flexible foot member 120, disclosed elsewhere herein.

[0062] The second flexible foot member 118 can be substantially plate-like and has a generally rectangular cross-section transverse to the longitudinal axis of the second flexible foot member 118 along at least a portion of its length. The second flexible foot member 118 can extend from a proximal end (e.g., downward and / or forward) to a distal end of the second flexible foot member 118. As shown, the second flexible foot member 118 may be disposed below the first flexible foot member 116. In an embodiment, the second flexible foot member 118 may extend tangentially forward and toward the distal end of the first flexible foot member 116. In some embodiments, at least a portion of the second flexible foot member 118 may abut the first flexible foot member 116 along a portion of the foot portion of the first flexible foot member 116. Although the first and second flexible foot members 116, 118 are depicted as ending at approximately the same point posterior to a toe portion of the prosthetic foot 100, in some embodiments the first flexible foot member 116 may extend more anteriorly, or the second flexible foot member 118 may extend more anteriorly. There may be a gap 132 between a bottom surface of first flexible foot member 116 and a top surface of the second flexible foot member 118. As disclosed elsewhere herein, the size of the gap 132 may change during ambulation to vary the stiffness of the prosthetic foot 100.

[0063] The prosthetic foot 100 can further include a third flexible foot member 120. The third flexible foot member 120 may be substantially plate-like and has a generally rectangular or rectangular cross-section transverse to a longitudinal axis of the third flexible foot member 120 along at least a portion of its length. The third flexible foot member 120 can extend from a heel end 136 to a toe end 142 and may include an arch region 138 between the heel end 136 and the toe end 142. For example, the arch region 138 may be at approximately the location of an arch of a natural human foot. In some embodiments, a toe portion of the third flexible foot member 120 can include generally a U-shaped cut-out portion, slot, or gap, 148 (see Figure 3) extending inwardly from the toe end 142. In some embodiments, the cut-out portion 148 is positioned toward a medial side of the longitudinal axis of the third flexible foot member 120 but is spaced from a medial edge of the third flexible foot member 120.

[0064] The first, second, and third flexible foot members can be attached together at an attachment location 140. In some embodiments, the attachment location 140 may include screws, bolts, and other fasteners. In some embodiments, the attachment location 140 may be at a mid-foot section. This mid-foot section can be at the distal ends of the first and second flexible foot members 116, 118 and posterior to the toe end 142 of the third flexible foot member 120.

[0065] Figures 4-11 illustrate an embodiment of a prosthetic foot 200 as disclosed herein. Any features of the prosthetic foot 100 in Figures 1-3 may be incorporated into the prosthetic foot 200 in Figures 4-11 and any features of the prosthetic foot 200 in Figures 4-11 may be incorporated into the prosthetic foot 100 in Figures 1-3. The same or substantially same components (e.g., in terms of structure, function, etc.) are labeled with the same reference number, and the descriptions thereof with reference to the prosthetic foot 200 are not repeated for brevity. The differences between the prosthetic foot 100 and the prosthetic foot 200 are described with reference to Figures 1 and 4-6.

[0066] Unlike including torque arms and connection rods on the lateral and medial sides of the prosthetic foot like the prosthetic foot 100 disclosed herein, the prosthetic foot 200 may include a single torque arm 208 (see Figure 6) extending from a middle portion of the output center 110. The single torque arm 208 may be coupled with a single connection rod 224 (see, e.g., Figures 4-6). In some embodiments, the torque arm 208 and / or the connection rod 224 of the prosthetic foot 200 may be coplanar or generally aligned along the central longitudinal axis with the rear link 126. For example, the torque arm 208, the connection rod 224, and the rear link 126 may be within a sagittal plane of theprosthetic foot 200. The moving connectors (e.g., torque arm 208, connection rod 224, and lever fork 230 of the prosthetic foot 200) may be connected in series, with the two free ends at the torque arm 208 and the lever fork 230, respectively, hinged to fixed bases (i.e., the output center 110 of the actuator 112 and the proximal portion 134 of the first flexible foot member 116, which in turn is pivoted at the second connection portion 114 of the attachment member 102). Here, moving and fixed may be relative to the attachment member 102. As a result, the torque output at the output center 110 may be transmitted to rotation of the first flexible foot member 116 at the second connection portion 114. In some embodiments, the torque arm 208, connection rod 224, and the lever fork 230 may include rigid components. In some embodiments, one or more of the torque arm 208, connection rod 224, and the lever fork 230 may include an elastic member.

[0067] Additionally, unlike the connection 150 between the connection rods 124 and the lever forks 130 in the prosthetic foot 100 (see Figure 1), which may, (e.g., depending on the output of the actuator 112), extend posteriorly to overlap partially with the rear link 126 in a side view, the connection 250 of the connection rod 224 and the lever fork 130 in the prosthetic foot 100 may not be able to, (e.g., at any time), extend more posterior than an anterior surface of the rear link 126. Otherwise, the connection 250 may hit the rear link 126 when the actuator 112 is activated. Accordingly, as shown in Figures 1, 3, and 4, the lever forks 130 in the prosthetic foot 100 are longer than the lever fork 230 in the prosthetic foot 200. As shown in Figure 1, the distance from the connection 150 to the distal end of the first flexible foot member 116 (DI) may range between about 130 mm to about 150 mm, or about 134 mm to about 146 mm, or about 138 mm to about 142 mm, or about 134 mm to about 138 mm, or about 135 mm to about 137 mm, or about 138 mm, or about 140 mm, or any distance within a range defined by those values. The distance from the connection 150 to the proximal end of the foot portion of the first flexible foot member 116 (D2) can range between about 44 mm to about 54 mm, or about 46 mm to about 52 mm, or about 48 mm to about 50 mm, or about 48.5 mm to about 49.5 mm, or about 49.0 mm, or any distance with a range defined by those values. In contrast, as shown in Figure 4, the distance from the connection 250 to the distal end of the first flexible foot member 116 (D3) may range between about 115 mm to about 125 mm, or about 116 mm to about 124 mm, or about 117 mm to about 123 mm, or about 118 mm to about 122 mm, or about 119 mm to about 121 mm, or about 120 mm, or about 120.5 mm, or any distance within a range defined by those values. The distance from the connection 250 to the proximal end of the foot portion of the first flexible foot member 116 (D4) can rangebetween about 24 mm to about 29 mm, or about 24.5 mm to about 28.5 mm, or about 25 mm to about 28 mm, or about 25.5 mm to about 27.5 mm, or about 26 mm to about 27 mm, or about 26.2 mm to about 26.8 mm, or any distance with a range defined by those values. In some embodiments, a different transmission mechanism from the mechanisms in the prosthetic foot 100, 200 may be used to transmit the torque from the actuator to the ankle joint and / or the foot members.

[0068] Figure 12 illustrates the input and output of a control system 160 of the prosthetic foot disclosed herein. An input from the angle sensor disclosed herein (e.g., angle sensor 128) and an input from the load cell disclosed herein (e.g., load cell 106) may be fed into the control system 160. In some embodiments, the control system 160 may include an impedance controller that can control the stiffness of the ankle joint of the prosthetic foot. In some embodiments, the actuator disclosed herein can increase the stiffness of the ankle (also referred to as resistance) and / or reduce the stiffness of the ankle (also referred to as assistance). The ankle torque value as determined by the control system 160 can be sent to the motor driver of the actuator 112 as the desired torque. The gains and desired positions and velocities of the impedance control can be adjusted within gait phases, gait subphases, and terrains / activities. As shown in Figure 12, in some embodiments, the control system 160 of the prosthetic foot disclosed herein may control the length of the rear link 126 through a motor. The command from the control system 160 may be, for example but not limited to a target length of the rear link 126, a force applied to the rear link to reach the target length, or the like.

[0069] In some embodiments, the control system 160 may determine the torque value using an impedance equation. The impedance control of the control system 160 may include a stiffness and damping system in which the angle (e.g., ankle position) and angular velocity (e.g., ankle velocity) may be used at least in part to determine the torque applied by the actuator 112 to reach a desired ankle position and / or velocity.

[0070] In an example, the impedance equation for calculating the ankle torque may be T=K*(Pos_des-Pos_act) + D*(Vel_des-Vel_act), where K is stiffness gain, and D is damping gain, Pos des is the desired ankle position, Pos act is the measured ankle position, Vel des is the desired ankle velocity, and Vel act is the measured ankle velocity. In some embodiments, the measured ankle position and / or measured ankle velocity may be based on the input from the angle sensor disclosed herein. In some embodiments, different impedance equation(s) may be used.

[0071] In some embodiments, the gains, desired ankle position, and / or desired ankle velocity may be based on the input from the load cell disclosed herein. The load cell may be used for ground contact sensing. The prosthetic foot disclosed herein may implement different desired ankle position and / or desired ankle velocity at least in part based on data from the ground contact sensing. For example, data from the ground contact sensing may indicate the user is in various phases, including but not limited to stance phase, toe-lift during the swing phase, heel strike phase, push-off phase, etc. In some embodiments, the load cell may make heel-load and toe-load measurements, which can be used to create compliant motion in the ankle of the prosthetic foot disclosed herein in order to minimize the load on the ankle. Minimizing the load can be beneficial, for example, when the user is in a seated position, relaxing, or getting ready to stand up. The heel-load and toe load can further be used to identify various activities of the prosthetic foot and / or terrains. For example, an excessive heel load during weight acceptance phase may be identified as down ramp walking. As another example, if only toe-load is detected, the user may be engaged in stairs or ramp ascent).

[0072] A torque output by the actuator may directly or indirectly result in a first force on the first flexible foot member 116 (e.g., at the proximal portion 134) and a second force on the second flexible foot member 118 (e.g., at the proximal end via the rear link 126). The first force and the second force may be in opposite directions. When the actuator 112 of the prosthetic foot 100, 200 or other prosthetic foot embodiments disclosed herein outputs a torque rotating the output center 110, the torque arm(s) disclosed herein may create a motion on the connection rods 124 or connection rod 224. The created motion on the connection rods 124 or connection rod 224may pull or push on the lever forks 130 or lever fork 230 connected rigidly to the first flexible foot member 116. The pull or push on the lever forks 130 or lever fork 230 may result in a pull or push on the proximal portion 134 of the first flexible foot member 116, which is clamped to the lever forks 130 or lever fork 230. Because the second connection portion 114 and the third connection portion 125 are on opposite sides of the first connection portion 104, the pull or push on the first flexible foot member 116 at the proximal portion 134 may result in the rear link 126 creating a counter force to the pull or push force of the lever forks 130 or lever fork 230 onto the second flexible foot member 118. As a result, the rear link 126 may pull or push on the second flexible foot member 118 (e.g., at the proximal end of the second flexible foot member 118). This actuated force on the second flexible foot member 118 may change the stiffness and / or angle of the third flexible foot member 120 (e.g., by changing the bendinglength of the third flexible foot member 120). Additionally or alternatively, this actuated force on the second flexible foot member 118 may create the different functions of the prosthetic foot 100, 200, or other foot embodiments disclosed herein. The impact of the functions may be proportional to the variable and controlled output torque from the actuator 112.

[0073] In some embodiments, when a downward force applied to the lever forks 130 or lever fork 230 by the torque arms 108 or torque arm 208 is countered by an upward force applied by the rear link 126, the upward force applied on the second flexible foot member 118 and the downward force applied on the first flexible foot member 116 may decrease the gap 132 between the first and second flexible foot members 116, 118. Additionally or alternatively, the gap 133 between the second and third flexible foot members 118, 120 may be decreased. Conversely, when an upward force applied to the lever forks 130 or lever fork 230 by the torque arms 108 or torque arm 208 is countered by a downward force applied by the rear link 126, the downward force applied on the second flexible foot member 118 and the upward force applied on the first flexible foot member 116 may increase the gap 132 between the first and second flexible foot members 116, 118. Additionally or alternatively, the gap 133 between the second and third flexible foot members 118, 120 may be increased. Changing of the gap sizes of the gaps 132, 133 may affect the stiffness of the prosthetic foot, which may enhance or limit the function of the prosthetic foot depending on the gait cycle, user activity, and / or terrain. Increasing or decreasing the stiffness of the flexible foot members of the prosthetic foot can allow the prosthetic foot to be more versatile in adapting to various intensity levels of the user’s activity. For example, a less stiff foot may be more desirable for daily walking, whereas a stiffer foot may be more desirable during jogging.

[0074] In some embodiments, the actuator 112, using impedance control, may aid a user (e.g., reducing the user’s effort) in dorsiflexing the prosthetic foot 100, 200, or other foot embodiments disclosed herein (e.g., increased toe lift during swing and thus more clearance from the ground) or plantar flexion (e.g., during early stance in a ramp descent to increase balance with an earlier foot flat phase).

[0075] Additionally or alternatively, the control system can assist a user (e.g., reducing the user’s effort) in rolling over the ankle (also referred to as guided rollover) by setting the desired position or velocity in the torque determination (e.g., in the impedance equation) to a value that may pull the user forward (that is, providing tibia progression assist).

[0076] Additionally or alternatively, the control system can instruct the actuator to increase the stiffness of the ankle (e.g., using the impedance equation) by adjusting the stiffness gain, and / or setting a lower desired position or a desired velocity that plantarflexes the foot. The timing of the push off assisted by the actuator may advantageously provide a more natural and / or effective push off, and / or reduce the user’s effort in the push off stage.

[0077] When the user walks on the prosthetic foot disclosed herein, the flexion of the flexible foot members may result from rotation of the actuator. The flexion of the flexible foot members may act a damper or a brake on the movements of the prosthetic foot. In some embodiments, the damping or braking work of the flexible foot members can be harvested into the battery of the prosthetic foot disclosed elsewhere herein. As the actuator is connected to the flexible foot members in parallel with the non-powered connection portions, which is described elsewhere in the present disclosure, the motor of the actuator may not need to be powered for the user to ambulate. Instead, the coils in the motor can be connected to energy harvesting electronics (including but not limited to the battery) to harvest energy when the motor turns (e.g., passively) during loading of the flexible foot members. The harvested energy can power an activity monitor (e.g., the control system disclosed herein), which can be used to change the dampening in the motor by connecting phases of the motor to adjust to different terrains and / or activities. Harvesting the energy may reduce or eliminate the need to recharge the battery of the prosthetic foot.

[0078] In some embodiments, the prosthetic foot may include other sensors, including but not limited to a motion or position sensor, such as an inertial measurement unit (IMU), an (e.g., 3-axis) accelerometer, gyroscope, etc. Input from the IMU may be used to interpolate between controls in the ankle. The input from the IMU may be fed to the control system 160 in addition to or alternative to the input from the angle sensor. In some implementations, the input from the IMU and / or the angle sensor can be used by the control system 160 to calculate a shank angle and / or angular shank velocity. The control system 160 can use the shank angle and / or angular shank velocity to interpolate between impedance (resistance) and assistance (push-off) controls disclosed herein. The higher the shank angular velocity is, the prosthetic foot (e.g., the ankle and / or the flexible foot members) can become stiffer and more push-off power may be generated during push-off phase. A lower angular velocity may result in less added stiffness in the ankle and / or the flexible foot members during rollover and little to no push-off power.

[0079] Alternatively or additionally, the control input for impedance control disclosed herein can include an EMG activity from the user. One or more electrodes maybe located within the socket coupled to the residual limb of the user. The EMG signal (e.g., amplitude, power, and the like) may indicate contraction of one or more muscles or muscle groups. Based at least in part on the EMG signal, the control system disclosed herein may adjust the impedance control of the ankle such that the user may adapt to different activities and / or terrains with different muscle contractions.

[0080] In some embodiments, the other sensors may include one or more sensors to measure distances between the first and second flexible foot members 116, 118, and / or between the second and third flexible foot members 118, 120. In one implementation, the sensor(s) may include hall-effect sensors. For example, the magnet may be on one flexible foot member and the hall-effect sensor may be on the other flexible foot member. In other implementations, the sensor(s) may include ultrasonic distance sensors, time-of-flight distance sensors, etc.

[0081] Further variations to the design of the prosthetic feet are also possible. For example, the flexible foot members described above can be custom made for individual users. The thickness of each flexible foot member can then vary across the length of each flexible foot member to provide a desired amount of flexibility and resistance against bending at each portion of the members. The thickness of the flexible foot members can be determined by any combination of factors such as a user’s weight, leg length, walking style, desired activities, residual limb strength, point of amputation, and the like.

[0082] Although this disclosure has been described in the context of certain embodiments and examples, it will be understood by those skilled in the art that the disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments and / or uses and obvious modifications and equivalents thereof. In addition, while several variations of the embodiments of the disclosure have been shown and described in detail, other modifications, which are within the scope of this disclosure, will be readily apparent to those of skill in the art. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the embodiments may be made and still fall within the scope of the disclosure. For example, features described above in connection with one embodiment can be used with a different embodiment described herein and the combination still fall within the scope of the disclosure. It should be understood that various features and aspects of the disclosed embodiments can be combined with, or substituted for, one another in order to form varying modes of the embodiments of the disclosure. Thus, it is intended that the scope of the disclosure herein should not be limited by the particular embodiments described above.Accordingly, unless otherwise stated, or unless clearly incompatible, each embodiment of this invention may comprise, additional to its essential features described herein, one or more features as described herein from each other embodiment of the invention disclosed herein.

[0083] Features, materials, characteristics, or groups described in conjunction with a particular aspect, embodiment, or example are to be understood to be applicable to any other aspect, embodiment or example described in this section or elsewhere in this specification unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The protection is not restricted to the details of any foregoing embodiments. The protection extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0084] Furthermore, certain features that are described in this disclosure in the context of separate implementations can also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations, one or more features from a claimed combination can, in some cases, be excised from the combination, and the combination may be claimed as a subcombination or variation of a subcombination.

[0085] Moreover, while operations may be depicted in the drawings or described in the specification in a particular order, such operations need not be performed in the particular order shown or in sequential order, or that all operations be performed, to achieve desirable results. Other operations that are not depicted or described can be incorporated in the example methods and processes. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the described operations. Further, the operations may be rearranged or reordered in other implementations. Those skilled in the art will appreciate that in some embodiments, the actual steps taken in the processes illustrated and / or disclosed may differ from those shown in the figures. Depending on the embodiment, certain of the steps described above may be removed, others may be added. Furthermore, the features and attributes of the specificembodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Also, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described components and systems can generally be integrated together in a single product or packaged into multiple products.

[0086] For purposes of this disclosure, certain aspects, advantages, and novel features are described herein. Not necessarily all such advantages may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the disclosure may be embodied or carried out in a manner that achieves one advantage or a group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0087] Conditional language, such as “can,” “could,” “might,” or “may,” unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without user input or prompting, whether these features, elements, and / or steps are included or are to be performed in any particular embodiment.

[0088] Conjunctive language such as the phrase “at least one of X, Y, and Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive language is not generally intended to imply that certain embodiments require the presence of at least one of X, at least one of Y, and at least one of Z.

[0089] Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”, “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than 1% of, within less than 0.1% of, and within less than 0.01% of the stated amount. As another example, in certain embodiments, the terms “generally parallel” and “substantially parallel” refer to a value, amount, or characteristicthat departs from exactly parallel by less than or equal to 15 degrees, 10 degrees, 5 degrees, 3 degrees, 1 degree, 0.1 degree, or otherwise.

[0090] Many other variations than those described herein will be apparent from this disclosure. For example, certain acts, events, or functions of any of the algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (for example, not all described acts or events are necessary for the practice of the algorithms). Moreover, acts or events can be performed concurrently, for example, through multi -threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines and / or computing systems that can function together.

[0091] It is to be understood that not necessarily all such advantages can be achieved in accordance with any particular example of the examples disclosed herein. Thus, the examples disclosed herein can be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.

[0092] The various illustrative logical blocks, modules, and algorithm steps described in connection with the examples disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. The described functionality can be implemented in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the disclosure.

[0093] The various illustrative logical blocks and modules described in connection with the examples disclosed herein can be implemented or performed by a machine, such as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be a controller, microcontroller, or state machine, combinations of the same,or the like. A processor can include electrical circuit or digital logic circuit configured to process computer-executable instructions. In another example, a processor can include an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few.

[0094] The steps of a method, process, or algorithm described in connection with the examples disclosed herein can be embodied directly in hardware, in a software module stored in one or more memory devices and executed by one or more processors, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of non-transitory computer-readable storage medium, media, or physical computer storage known in the art. An example storage medium can be coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. The storage medium can be volatile or nonvolatile. The processor and the storage medium can reside in an ASIC.

[0171] The scope of the present disclosure is not intended to be limited by the specific disclosures of preferred embodiments in this section or elsewhere in this specification, and may be defined by claims as presented in this section or elsewhere in this specification or as presented in the future. The language of the claims is to be interpreted broadly based on the language employed in the claims and not limited to the examples described in the present specification or during the prosecution of the application, which examples are to be construed as non-exclusive.

Claims

WHAT IS CLAIMED IS:

1. A prosthetic foot with a powered ankle joint, the prosthetic foot comprising: an attachment member comprising a connector configured to connect to a user or another prosthetic device; a first flexible foot member coupled to the attachment member at a first pivot; a second flexible foot member coupled to the attachment member at a second pivot via an elongate link, wherein the elongate link is coupled to the second pivot at a first end of the elongate link and coupled to the second flexible foot member at a second end of the elongate link; a powered actuator located within the attachment member, an output center of the powered actuator coupled via a torque transmission mechanism to a proximal end of the first flexible foot member, the powered actuator configured to output a torque to control a stiffness of the ankle joint; an angle sensor located at the first pivot; a load cell located in the attachment member below the connector; and a control system configured to determine a desired torque value of the powered actuator based at least in part on input from the angle sensor and the load cell, wherein a torque output of the powered actuator is configured to cause a first force on the first flexible foot member and a second force on the second flexible foot member, and wherein the first force and the second force are in opposite directions.

2. The prosthetic foot of Claim 1, wherein the control system is configured to apply an impedance equation to determine the desired torque value for the powered actuator to achieve a desired angle and / or position of the ankle joint.

3. The prosthetic foot of Claim 2, wherein the control system is further configured to adjust stiffness gain or the desired angle and / or position of the ankle joint of the impedance equation based on detected user activity and / or terrain.

4. The prosthetic foot of any of Claims 1-3, further comprising a third flexible foot member located below the second flexible foot member and coupled to the first and second flexible foot members, wherein the second force on the second flexible foot member is configured to change a stiffness or angle of the third flexible foot member.

5. The prosthetic foot of any of Claims 1-4, wherein the second force is imparted on the second flexible foot member by the elongate link.

6. The prosthetic foot of any of Claims 1-5, wherein the load cell is configured to provide ground contact sensing.

7. The prosthetic foot of Claim 6, wherein the load cell is further configured to provide heel-load and / or toe-load measurements.

8. The prosthetic foot of any of Claims 1-7, wherein the powered actuator is configured to dorsiflex and / or plantarflex the ankle joint.

9. The prosthetic foot of any of Claims 1-8, wherein the powered actuator is configured to assist in roll over of the ankle joint by setting a desired torque value that provide tibial progression assist.

10. The prosthetic foot of any of Claims 1-9, wherein the actuator is further configured to increase the stiffness of the ankle joint to provide push off energy.

11. A prosthetic foot with a powered ankle joint, the prosthetic foot comprising: an attachment member comprising a first connection portion configured to connect to a user or another prosthetic device; a first flexible foot member, a proximal end of the first flexible foot member connected to a second connection portion of the attachment member; a second flexible foot member, a proximal end of the second flexible foot member connected to the attachment member via a third connection portion and a fourth connection portion, the second flexible foot member located below the first flexible foot member; an elongate link extending between and coupled to the third and fourth connection portions; a third flexible foot member located below the second flexible foot member and coupled to the first and second flexible foot members at proximal ends of the first and second flexible foot member such that the first, second, and third flexible foot members are operably coupled to the attachment member; a powered actuator located in an actuator housing of the attachment member; and a plurality of connectors connected in series with a first free end at a first connector and a second free end at a last connector, wherein the first free end is coupled to an output center of the powered actuator and the second free end is coupled to the proximal end of the first flexible foot member, such that a torque at the output center of the powered actuator is configured to cause a rotation of the ankle joint.

12. The prosthetic foot of Claim 11, wherein the plurality of connectors are located on medial and lateral sides of the powered actuator.

13. The prosthetic foot of Claim 11, wherein the plurality of connectors are located on a sagittal plane of the prosthetic foot.

14. The prosthetic foot of any of Claims 11-13, wherein a first force applied on the first flexible foot member due to a torque applied by the powered actuator is configured to be countered by a second force applied on the second flexible foot member by the elongate link, the first force and the second force being in opposite directions.

15. The prosthetic foot of any of Claims 11-14, further comprising an angle sensor located at the second connection portion.

16. The prosthetic foot of any of Claims 11-15, further comprising a load cell located at the attachment member below the first connection portion.

17. The prosthetic foot of Claim 16, wherein the load cell is configured to provide ground contact sensing.

18. The prosthetic foot of Claim 16 or 17, wherein the load cell is configured to provide heel-load and / or toe-load measurements.

19. The prosthetic foot of any of Claims 11-18, further comprising a control system configured to control a stiffness of the ankle joint via impedance control.

20. The prosthetic foot of Claim 19, wherein the control system is configured to apply an impedance equation to determine a desired torque value for the powered actuator to achieve a desired angle and / or position of the ankle joint.

21. The prosthetic foot of Claim 20, wherein the control system is further configured to adjust stiffness gain or the desired angle and / or position of the ankle joint of the impedance equation based on detected user activity and / or terrain.

22. The prosthetic foot of any of Claims 11-21, wherein a control of the ankle joint via a torque output of the powered actuator is independent of rotation of the ankle joint due to loading of the first, second, and / or third flexible foot members during ambulation.

23. The prosthetic foot of Claim 22, wherein the powered actuator is configured to be not powered during ambulation, and wherein loading of the first, second, and / or third flexible foot members during the ambulation is configured to turn a motor of the powered actuator.

24. The prosthetic foot of Claim 23, wherein energy from turning of the motor is configured to be harvested by energy harvesting electronics.

25. The prosthetic foot of any of Claims 11-24, wherein the plurality of connectors are distinct from the first, second, or third flexible foot members, or the attachment member.

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