Electro-Hydrostatic Prosthesis Actuator Without Valves or Accumulators
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Solution Overview
Problem
Current hydraulic actuators in prosthetic devices, such as those described in US 2010/0023133, are complex, consume high power, generate noise, and have non-linear operation due to valve control and fluid resistance, limiting their efficiency and longevity.
Innovation Solution
A fully integrated linear electro-hydrostatic actuator (EHA) comprising an electric motor, a gerotor volumetric pump, and a linear hydraulic cylinder, which eliminates the need for hydraulic valves and accumulators, providing both active and regenerative power with low power consumption and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional hydraulic actuators with valves and accumulators are used, then the prosthesis can provide active and passive power, but the device complexity increases and operation becomes non-linear
Solution Approach 1:
The patent removes hydraulic valves and accumulators from the system, extracting the problematic components that caused complexity and non-linear operation. The electro-hydrostatic actuator achieves power adaptation through direct electrical control of the motor-pump assembly without needing separate valve control systems or energy storage accumulators.
Solution Approach 2:
The electro-hydrostatic actuator integrates multiple functions into a single unified system. The electric motor can operate in motor mode for active power delivery and in generator mode for passive power recovery, eliminating the need for separate active and passive power systems. This multi-functional design reduces overall device complexity while maintaining versatility.
2Ease of operation
If hydraulic valves and flow control circuits are used, then the actuator can control movement, but the operation becomes non-linear due to valve transients and fluid resistance
Solution Approach 1:
The patent replaces the mechanical hydraulic valve control system with an electro-hydrostatic system where an electric motor directly controls hydraulic fluid flow. This substitution eliminates valve transients and non-linear fluid resistance effects, providing more consistent and predictable linear operation while maintaining movement control capability through electrical control signals.
3Power
If a hydraulic pump with gear mechanism is used, then the actuator can provide hydraulic power, but noise and power consumption increase
Solution Approach 1:
The patent changes the operating parameters of the hydraulic pump by using an electric motor with variable speed control instead of a fixed-speed gear-driven pump. This allows the system to optimize power delivery while minimizing noise and power consumption by adjusting motor speed and torque according to actual operational needs, rather than continuously running at full capacity.
Solution Approach 2:
The electro-hydrostatic actuator uses periodic motor activation instead of continuous hydraulic pump operation. The motor runs only when power delivery or recovery is needed, with regenerative braking during deceleration phases. This periodic operation pattern reduces overall noise and power consumption compared to continuous hydraulic system operation.
4Productivity
If the actuator operates continuously to provide active power, then the prosthesis functionality is improved, but battery power is depleted faster
Solution Approach 1:
The patent converts the previously harmful energy waste during deceleration and regenerative phases into useful energy. The electric motor operates as a generator during passive movement phases, converting kinetic energy back into electrical energy to recharge the battery. This transforms energy that would have been lost as heat or inefficiency into a beneficial power source, extending battery life while maintaining full prosthesis functionality.
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 actuator enhances the efficiency and autonomy of prosthetic devices by providing a more natural and complex task execution capability, with longer operating times and reduced discomfort, while maintaining a compact and efficient design.
Implementation Method 1
an electric motor, a gerotor volumetric pump
Implementation Method 2
a gerotor volumetric pump
Implementation Method 3
a linear hydraulic cylinder
Data Source
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.