Electrohydrostatic Prosthetic Actuator With Regenerative Knee Motion
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Solution Overview
Problem
Existing prosthetic devices, such as those described in US 2010/0023133, suffer from complexity, non-linear operation, high power consumption, noise, and inefficiency due to hydraulic actuators with valves and gears, limiting their effectiveness and battery life.
Innovation Solution
A linear electro-hydrostatic actuator (EHA) is integrated into the prosthesis, comprising a hydraulic cylinder, a permanent-magnet brushless motor, and a gerotor pump, eliminating valves and optimizing the actuator for low power consumption and noise, with both active and regenerative operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional hydraulic actuators with valves and gears are used, then the prosthesis can provide active force during knee flexion and extension, but the device complexity increases and power consumption rises
Solution Approach 1:
The patent removes valves and gear mechanisms from the hydraulic actuator system, extracting only the essential hydraulic cylinder and pump components. This simplification eliminates non-essential elements that contributed to complexity while preserving the core force-generating capability through direct hydraulic actuation.
Solution Approach 2:
The patent integrates the electric motor and hydraulic pump into a unified electro-hydrostatic actuator assembly, merging previously separate components into a single integrated unit. This combination reduces overall device complexity by eliminating intermediate mechanical transmissions and reducing the number of discrete parts.
2Ease of operation
If traditional hydraulic actuators with valves are used, then the prosthesis can control knee movement, but the power consumption increases and battery life decreases
Solution Approach 1:
The patent implements a regenerative braking system where the hydraulic pump acts as a motor during knee flexion, recovering energy and storing it in the accumulator. This self-service mechanism reduces net power consumption by recycling energy that would otherwise be lost during the unassisted phase of the gait cycle.
Solution Approach 2:
The patent employs periodic activation of the electric motor, running it only during the extension phase when force is needed, while relying on passive gravity-driven flexion and regenerative energy recovery during the flexion phase. This periodic operation pattern significantly reduces average power consumption compared to continuous motor operation.
3Power
If traditional hydraulic actuators with gears are used, then the prosthesis can provide motive action, but noise increases and efficiency decreases
Solution Approach 1:
The patent replaces mechanical gear transmissions with a direct-drive electro-hydrostatic system where the electric motor directly drives the hydraulic pump without intermediate gear mechanisms. This substitution eliminates gear meshing noise and mechanical friction losses, providing motive action through hydraulic pressure generation alone.
4Force
If traditional hydraulic actuators are used, then the prosthesis can support gait phases, but the actuator size and weight increase
Solution Approach 1:
The patent nests the rodless hydraulic cylinder design where the piston and hydraulic chamber are integrated within a compact housing, eliminating the need for separate rod assemblies and external reservoirs. This nested configuration reduces the overall actuator footprint and weight while maintaining the necessary force-generating capacity.
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 EHA provides high efficiency, reduced size, and extended operation time by minimizing power consumption and noise, allowing for more complex movements and increased autonomy.
Implementation Method 1
permanent-magnet brushless motor
Implementation Method 2
gerotor pump
Implementation Method 3
hydraulic circuit
Implementation Method 4
hydraulic energy can be recovered to recharge the electric batteries
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a prosthesis (1) for limbs of the human body, in particular the leg, actuated by means of an actuator (10) capable of both generating and collecting energy.The actuator is a linear electro-hydrostatic (EHA) one, and is more compact and efficient than traditional drives based on electro-mechanical gears. Through a suitable kinematic chain, the actuator (10) produces an angle-dependent transmission ratio.The invention also comprises a generated rotor pump (20), whose external rotor is supported by rolling means.