Prosthesis with powered ankle and toe joints
Inventors
Lenzi, Tommaso • GABERT, Lukas R. • Tran, Minh
Assignees
University of Utah • University of Utah Research Foundation Inc
Publication Number
US-12208026-B2
Publication Date
2025-01-28
Expiration Date
2042-03-29
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Abstract
Disclosed herein is a robotic ankle foot prosthesis that replicates the key biomechanical functions of the biological ankle and toe joints while matching the weight, size, and battery life of passive microprocessor-controlled prostheses. A single actuator powers the ankle and toe joints. The mechanism maximizes the mechanical energy regeneration during walking while imitating the physiological features of energy injection by way of the ankle joint and energy dissipation by way of the toe joint.
Core Innovation
The invention is a robotic ankle-foot prosthesis that replicates the biomechanical functions of biological ankle and toe joints while maintaining the weight, size, and battery life comparable to passive microprocessor-controlled prostheses. The prosthesis incorporates a single actuator that powers both the ankle and toe joints through a specialized kinematic mechanism, maximizing mechanical energy regeneration during walking. This design imitates physiological characteristics by injecting energy through the ankle joint and dissipating energy through the toe joint, closely aligning with natural gait patterns.
Previous prosthesis technologies primarily used passive elements or hybrid actuators that could not actively generate movement or inject net-positive energy, thus limiting user mobility, particularly for activities like stair climbing, descending ramps, or sitting and standing transitions. Other attempts at integrating powered toe joints have led to heavier and bulkier devices, and designs involving parallel springs or four-bar linkages faced substantial limitations in range of motion and size constraints. There was an unmet need for compact, lightweight, and fully powered prostheses capable of effective, biomechanically appropriate toe joint function.
The disclosed prosthesis features a shank assembly, tarsal assembly, and toe assembly connected so that a linear actuator within the tarsal assembly adjusts the distance between shank and toe pivot shafts, simultaneously providing torque and motion to the ankle and toe joints. The actuator may include a compliant element, such as a spring, to bring the toe joint toward a neutral position when inactive. This underactuated configuration uses fewer mechanical and electrical components, matching the functional requirements of biological joints and enabling a smaller, lighter, and more energy-efficient powered prosthesis.
Claims Coverage
The patent contains several independent claims that define inventive features relating to a powered assistive ankle and foot device, especially in the integration and actuation mechanisms that simultaneously power the ankle and toe joints.
Simultaneous actuation of ankle and toe joints by a single linear actuator
A powered assistive ankle and foot device in which a single linear actuator associated with the tarsal assembly powers movement of both the ankle joint and the toe joint. The actuator adjusts the distance between a shank pivot shaft and a toe pivot shaft to provide simultaneous torque and coordinated movement such that lessening this distance results in ankle plantarflexion and toe flexion, while increasing it results in ankle dorsiflexion and toe extension.
Offset pivot shaft configuration for mechanical advantage
The device employs a configuration where the shank pivot shaft is mechanically connected to an ankle joint and offset from it, and the toe pivot shaft is mechanically connected to a toe joint and offset from it. An offset distance between the ankle joint and the shank pivot shaft is greater than that between the toe joint and the toe pivot shaft, optimizing the mechanical advantage for ankle over toe actuation.
Integration of a compliant element in the actuator for toe joint neutral positioning
The linear actuator includes a screw assembly and a compliant element (such as a spring), which is mechanically connected to the nut of the screw assembly and configured to move the toe joint toward a neutral position when no force is applied via the actuator. Anchoring of the spring between a proximal anchor (connected to the nut) and a distal anchor (connected to the toe pivot shaft) allows for restorative action that assists in joint positioning.
Compact, non-rotating motor transmission system
The device comprises a motor, preferably attached to or housed within the shank assembly, that does not rotate relative to the shank frame during ankle joint movement. The motor is mechanically connected to the linear actuator through a power transmission assembly, which includes multiple bevel gears that efficiently transfer power to the actuator while maximizing use of internal space and minimizing build height.
In summary, the patent claims inventive features in the concurrent actuation of ankle and toe joints using a single, strategically linked actuator mechanism, the use of offset pivot shafts for biomechanical and mechanical efficiency, integration of compliant elements to assist joint motion, and a compact, fixed motor and gear transmission layout.
Stated Advantages
The prosthesis allows for a compact and lightweight design while providing fully powered ankle and toe joint actuation comparable to passive microprocessor-controlled devices.
A single actuator powers both the ankle and toe joints, reducing the number of mechanical and electrical components, resulting in improved energy efficiency and lower electrical energy consumption.
The mechanism closely replicates physiological energy injection at the ankle and energy dissipation at the toe, achieving biomechanically appropriate function that can improve real-world mobility for users.
Lower energy losses occur in the underactuated design compared to ankle-only actuators, primarily due to reduced actuator velocity and acceleration, resulting in reduced inertial torque and mechanical power output requirements.
The actuator arrangement enables energy regeneration at the toe joint during walking, enhancing overall efficiency.
Documented Applications
The invention is applied in prosthesis devices for individuals with lower-limb amputations, especially below-knee amputations, to improve ambulation and real-world mobility.
The technology can be used in powered assistive devices, including prostheses, orthoses, and exoskeleton components.
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