Hip and Knee Actuation for Lower Limb Orthotics
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Solution Overview
Problem
Existing orthotic devices are bulky and cumbersome, and lack the ability to power both thigh and knee joints effectively to aid in natural walking motions while carrying a load.
Innovation Solution
A lower limb orthotic device with a hip and knee actuation system that includes a linear hydraulic hip actuator, mechanical transmission mechanisms, and a shared motor-driven pump arrangement, utilizing hydraulic circuits with check valves and valves to provide different gear ratios for efficient torque generation during walking phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pneumatic cylinders and pump system are used to power leg movement, then walking assistance is provided, but the device becomes bulky and cumbersome
Solution Approach 1:
The orthotic device divides the leg into separate functional segments (thigh link and shank link) with independent actuation systems for hip and knee joints, allowing each segment to be optimized independently for weight and function
Solution Approach 2:
The patent replaces bulky pneumatic cylinders with a more compact mechanical transmission system using linkages and levers that transmit force from the pump through hydraulic actuators, reducing overall device weight while maintaining walking assistance capability
2Power
If separate motor-driven pumps are used for hip and knee actuation, then each joint receives adequate power, but the device complexity increases
Solution Approach 1:
The patent merges two separate motor-driven pump systems into a single shared pump that serves both hip and knee actuators. The pump alternates between supplying hydraulic fluid to the hip actuator and the knee actuator, providing adequate power to both joints while halving the number of motors and pump components required
Solution Approach 2:
The shared pump operates in periodic cycles, alternating between actuating the hip joint and actuating the knee joint. This periodic operation ensures both joints receive sufficient power while the single pump remains compact, avoiding the complexity of two continuously operating pump systems
3Device complexity
If hydraulic pump operates at constant speed, then system simplicity is maintained, but torque distribution during different walking phases is inefficient
Solution Approach 1:
The patent implements dynamic pump speed control that adjusts the hydraulic pump's operating speed based on the walking phase. The pump operates at higher speeds during swing phase for fast actuator response and at lower speeds during stance phase for high torque generation, optimizing overall walking efficiency
Solution Approach 2:
The system changes the pump's operational parameters (speed and flow rate) according to the gait cycle phase. During swing phase, the pump operates at high speed with low torque requirements, while during stance phase, it operates at low speed with high torque requirements, matching the biomechanical demands of natural walking
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables a compact, wearable orthotic device that provides natural walking motion by optimizing torque distribution across joints, allowing for efficient power assistance during both swing and stance phases, thus enhancing mobility and load-carrying capabilities.
Implementation Method 1
a hydraulic pump driven by the electric motor to pressurize hydraulic fluid within a hydraulic circuit to extend or retract the linear hydraulic hip actuator
Implementation Method 2
first and second pilot check valves which regulate the flow of hydraulic fluid between first and second fluid ports of a non-symmetrical linear hip actuator
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A lower limb orthotic device (100) includes a thigh link (101) connected to a hip link (102) through a hip joint (103). a hip torque generator (106) including a hip actuator (110) and a first mechanical transmission mechanism (111) interposed between the thigh link ( 101) and the hip link (102), a shank link (104) connected to the thigh link (101) through a knee joint ( 105), a knee torque generator ( 107) including a knee actuator (112) and a second mechanical transmission mechanism (113) interposed between the thigh link (101) and the shank link (104), and a controller (108), such as for a common motor (154) and pump (156) connected to the hip and knee torque generators (106, 107), for regulating relative positions of the various components in order to power a user through a natural walking motion, with the first and second mechanical transmission mechanisms (111, 113) aiding in evening out torque over the ranges of motion, while also increasing the range of motion where the torque generators (106, 107) can produce a non-zero torque.