Semi-Actuated Prosthetic Knee With Hydraulic Power Unit
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Solution Overview
Problem
Above-knee prosthetics require effective control of swing and stance phases with varying motion ranges, but existing systems often consume excessive power and are bulky, limiting amputees' mobility and activity range.
Innovation Solution
A semi-actuated prosthetic knee system that operates in both actuated and un-actuated modes, using a hydraulic power unit with a signal processor and sensors to manage torque and resistance, reducing power consumption and enhancing motion control through a combination of electric and hydraulic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fully actuated powered knee system is used to provide consistent motion control during swing and stance phases, then motion control reliability is improved, but power consumption increases and device size becomes bulky
Solution Approach 1:
The hydraulic pump operates intermittently rather than continuously, activating only during specific phases of the gait cycle when torque generation is needed. The controller monitors gait phase and triggers the pump to deliver hydraulic fluid to the torque generator only during swing and stance phases, allowing the system to maintain reliability while significantly reducing overall power consumption compared to continuous operation.
Solution Approach 2:
The control system divides the gait cycle into distinct phases (swing phase and stance phase) and applies actuation only during specific segments rather than continuously. The controller separates the operation into periodic intervals where the hydraulic system is activated during needed phases and deactivated during others, enabling reduced power consumption while maintaining motion control reliability when required.
2Manufacturing precision
If a fully actuated powered knee system is used to provide synchronized torque and power, then motion control precision is improved, but device complexity and size increase
Solution Approach 1:
The system achieves motion control precision through periodic, phase-specific actuation rather than continuous complex control. The hydraulic pump delivers torque during swing and stance phases in a periodic manner, simplifying the overall system architecture while maintaining the precision needed for synchronized torque and power delivery during critical gait phases.
3Speed
If fluid system speed is increased to improve response time during swing phase, then swing control performance is improved, but power consumption increases
Solution Approach 1:
The hydraulic pump operates at high speed only during brief periodic intervals corresponding to swing and stance phases, rather than maintaining high speed continuously. This periodic high-speed operation delivers the necessary response time performance during critical phases while dramatically reducing average power consumption compared to continuous high-speed operation.
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 system allows amputees to walk longer distances on a single battery charge, reduces hip torque, and provides efficient synchronized torque and power during the walking cycle, maximizing motion range and type while minimizing power usage.
Implementation Method 1
A hydraulic pump is coupled to an electric motor and configured to deliver hydraulic fluid under pressure to a torque generator
Implementation Method 2
A hydraulic pump is coupled to an electric motor and configured to deliver hydraulic fluid under pressure to a torque generator
Data Source
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AI summary
A semi-actuated above knee prosthetic system (100), includes a shank link (105) coupled to an artificial foot (108), a knee mechanism (107) connected to the shank link (105) and a thigh link (103) attached to an above-knee remaining lower limb (110) of an amputee, is operable in two modes controlled by a signal processor (130) linked to various sensors (120,122,124,126,127). In the actuated mode, power is delivered to a torque generator (104) connected to the knee mechanism (107) to move thigh (103) and shank links (105). In the un-actuated mode, a control circuit (204) operates in a non-powered manner with modulated resistance in the knee mechanism (107). Power is delivered through an electric motor (202) connected to a battery source (205) and employed to drive a hydraulic pump (201) as part of an overall hydraulic power unit (200) including the torque generator (104)