Electro Hydrostatic Actuation for Walking Machine Stability
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Solution Overview
Problem
Existing walking machines with traditional hydraulic systems face issues of low payload-to-vehicle mass ratio, high power consumption under low load, reliability problems, and maintenance challenges due to closely packaged hydraulic circuits, requiring constant system pressure to maintain position.
Innovation Solution
The implementation of an electro hydrostatic actuation (EHA) system with electric motors, fixed displacement pumps, and pilot-operated check valves, eliminating the need for a centralized reservoir and pump system, allowing power consumption to be proportional to the load, and enabling modular, easily replaceable units with reduced system mass.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional hydraulic system with centralized reservoir and pump is used, then the walking machine can maintain position, but power consumption is high due to constant system pressure
Solution Approach 1:
The patent divides the centralized hydraulic system into distributed electro-hydrostatic actuators, where each actuator contains its own pump and fluid reservoir. This segmentation eliminates the need for constant system pressure by allowing each actuator to operate independently and only pressurize fluid when actuation is required, thereby reducing overall power consumption while maintaining position-holding capability.
Solution Approach 2:
The electro-hydrostatic actuators use on-demand pressurization rather than continuous pressure maintenance. The electric motors drive pumps only when actuation is needed, creating periodic action patterns that significantly reduce average power consumption compared to traditional systems that maintain constant pressure.
2Volume of moving object
If closely packaged hydraulic circuits are used, then the system is compact, but reliability and maintenance are compromised
Solution Approach 1:
By distributing the hydraulic functions into separate modular electro-hydrostatic actuators, the patent reduces the complexity of closely packaged circuits. Each actuator is a self-contained unit with its own pump, fluid reservoir, and control electronics, isolating potential failure points and improving reliability while maintaining a compact overall system architecture.
Solution Approach 2:
Each electro-hydrostatic actuator is designed as a modular unit that can be independently replaced or maintained. The self-contained design with integrated components allows for easier servicing and repair without requiring system shutdown or complex disassembly, thereby improving maintenance accessibility and system reliability.
3Power
If traditional hydraulic systems are used, then the machine has sufficient power, but payload to vehicle mass ratio is low
Solution Approach 1:
The patent replaces the traditional mechanical-hydraulic power transmission system with an electro-hydrostatic system where electric motors directly drive hydraulic pumps. This substitution eliminates the need for heavy prime movers and complex power transmission mechanisms, reducing overall vehicle mass while maintaining or improving power delivery capability to the actuators.
Solution Approach 2:
The electro-hydrostatic actuators provide dynamic power delivery matched to actual operational needs, rather than requiring continuous high power capacity. The electric motors can rapidly adjust power output based on demand, allowing for lighter overall system design while maintaining sufficient power availability during actuation events.
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
This solution enhances payload capacity, reduces power consumption, improves reliability by isolating actuators, and simplifies maintenance, achieving efficient power use and stability during varying load conditions without external control loops.
Implementation Method 1
at least a first electro hydrostatic actuator in electrical communication with the leg microcontroller
Implementation Method 2
fixed displacement pumps
Implementation Method 3
pilot-operated check valves
Data Source
AI summary
A walking machine that includes a chassis with an operator interface, a main controller in data communication with the operator interface, at least two leg members operatively connected to the chassis, and a power system in data communication and electrical communication with the main controller. Each leg member includes a leg control system that includes a leg microcontroller in data communication with the main controller and at least a first electro hydrostatic actuator in electrical communication with the leg microcontroller. The power system includes an electrical generator, power supply electronics in electrical communication with the electrical generator, an electrical storage medium in electrical communication with the electrical generator and in parallel with the power supply electronics, and an electrical power bus for distributing power from the power system to the leg control systems.