Actuator Position Estimation Using Pressure and Spool Sensors
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Solution Overview
Problem
Existing fluid actuator systems in hydraulic applications lack precise positioning, leading to inaccuracies, especially in critical situations, due to the cost-prohibitive nature of position sensors and the imprecision of existing solutions like U.S. Pat. Nos. 6,848,323 and 7,114,430.
Innovation Solution
An actuator position control system that includes an actuator, at least one position sensor, a flow control valve with pressure and spool position sensors, and a controller that calculates corrected fluid flow rates and adaptive gain factors to estimate and correct the actuator position, using a combination of kinematic and dynamic components based on fluid pressure and spool position data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position sensors are installed on actuators to achieve precise positioning, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent introduces an intermediary estimation system that uses readily available sensors (pressure sensors, spool position sensors) to indirectly determine actuator position through mathematical modeling. Instead of directly measuring position with expensive position sensors, the system uses fluid pressure data and spool position data as intermediaries to calculate and estimate the actuator position, thereby avoiding the need for complex and costly direct position sensing while achieving acceptable measurement precision
Solution Approach 2:
The patent replaces the mechanical/electrical position sensing system with a computational estimation system. Instead of using physical position sensors that require mechanical coupling and electrical connections, the system substitutes a software-based estimation algorithm that processes pressure and spool position signals to derive actuator position information, reducing hardware complexity and installation requirements
2Measurement precision
If traditional position sensors with markings are used on actuators, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent creates a virtual copy or model of the actuator position through mathematical estimation rather than using physical sensors. The estimation algorithm creates a digital representation of the actuator position based on pressure and spool data, eliminating the need for physical markings on the rod and expensive position sensor hardware, thereby reducing manufacturing costs while maintaining measurement precision
Solution Approach 2:
The patent uses inexpensive pressure sensors and spool position sensors that are already part of the hydraulic system rather than expensive dedicated position sensors. These existing sensors serve as disposable or reusable components that provide sufficient data for position estimation without requiring additional costly markings or specialized sensor installations
3Device complexity
If existing position estimation methods (U.S. Pat. Nos. 6,848,323 and 7,114,430) are used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent incorporates feedback mechanisms where the estimated position is continuously refined using pressure feedback and spool position feedback. The system monitors the relationship between commanded spool position and actual fluid pressure changes, and uses this feedback to correct estimation errors and improve measurement precision over time, maintaining low device complexity while enhancing accuracy
Solution Approach 2:
The patent improves measurement precision by dynamically adjusting estimation parameters based on operating conditions. The system changes parameters such as flow coefficients, pressure compensation factors, and estimation algorithms based on real-time pressure and spool position data, allowing accurate position estimation across varying hydraulic conditions without increasing device complexity
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 provides precise actuator positioning by minimizing errors through adaptive gain factors and error-correction calculations, enhancing accuracy and reducing costs compared to traditional sensor-based solutions.
Implementation Method 1
A plurality of pressure sensors are included to monitor pressure of fluid at the supply port, the tank port, the first control port, and the second control port of the flow control valve
Implementation Method 2
at least one spool position sensor, wherein the spool position sensor provides spool position signals to the controller
Implementation Method 3
A flow control valve is in fluid communication with the actuator. The flow control valve includes a main stage spool, a supply port, a tank port, a first control port, and a second control port
Data Source
AI summary
A method for estimating actuator position includes the steps of receiving fluid pressure data signals from a plurality of fluid pressure sensors (31), receiving spool position signals from at least one spool position sensor (33), and receiving actuator position data signals from at least one actuator position sensor (35). Corrected flow rates to and from an actuator (21) are determined with each corrected flow rate being based on fluid pressure data signals, the spool position signals, and an error-correction factor, wherein the error-correction factor is a function of the fluid pressure data signals and the spool position signals. An estimated actuator position is determined wherein the estimated position includes a kinematic component and a dynamic component. Adaptive gain factors are applied to calibrate the estimated actuator position to the actuator position data signals from the actuator position sensor.