Electrohydrostatic Actuator Force Estimation Without Pressure Sensors
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Solution Overview
Problem
Existing electrohydrostatic actuators in aircraft require additional sensors to measure pressure and external forces, increasing bulk and mass, and relying on these sensors for real-time control to prevent damage from excessive reaction forces.
Innovation Solution
A method using state observers to estimate dynamic and static components of fluid pressure differences within the actuator, based on motor rotation speed, piston position, and supply current, allowing for the estimation of external forces without additional sensors, and a control unit applies corrections to limit fluid pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pressure sensors or force sensors are added to measure pressure difference or external force, then measurement precision is improved, but device complexity and weight increase
Solution Approach 1:
The system uses existing sensors (motor rotation speed sensor, piston position sensor, supply current sensor) to estimate the pressure difference and external force through computational methods, rather than adding dedicated pressure or force sensors. The actuator system estimates its own internal states using available measurements and mathematical models.
Solution Approach 2:
The patent replaces direct mechanical measurement (pressure sensors, force sensors) with a computational estimation system that uses electrical and positional measurements combined with mathematical models to derive pressure and force information indirectly.
2Measurement precision
If pressure sensors are added to measure pressure difference, then measurement precision is improved, but weight increases
Solution Approach 1:
The actuator system estimates its own internal states (pressure difference, external force) using existing measurements and mathematical models, eliminating the need for additional pressure or force sensors that would add weight.
Solution Approach 2:
The patent replaces direct mechanical measurement devices (pressure sensors, force sensors) with a computational estimation approach using electrical and positional measurements, thereby eliminating the weight penalty of additional sensing hardware.
3Measurement precision
If additional electronic equipment is added to process sensor signals, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The control unit uses existing computational resources to estimate pressure difference and external force through mathematical models, avoiding the need for additional dedicated electronic processing equipment for pressure or force sensor signals.
Solution Approach 2:
The existing control unit and sensors are made multi-functional: the motor rotation speed sensor, piston position sensor, and supply current sensor are used not only for their primary control functions but also for estimating pressure difference and external force through computational methods.
Data Source
AI summary
The invention concerns a method for estimating an external force acting on an electrohydrostatic actuator, the actuator comprising a ram including a first chamber, a second chamber and a piston located between the first chamber and the second chamber, a pump capable of injecting fluid into the chambers for controlling a movement of the piston, and an electric motor driving the pump, the method comprising steps of: estimating, by means of at least one state observer (21, 22), a dynamic component and a static component of a difference in equivalent fluid pressure between the first chamber and the second chamber from a rotational speed of the electric motor, a position of the piston and a supply current of the electric motor, estimating the external force by means of a post-processing module (23) as a combination of the estimated dynamic component and static component of the difference in fluid pressure.