Estimating Hydraulic Pump Displacement via Valve Position
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Solution Overview
Problem
Hydraulic machines face productivity losses and increased complexity due to the shutdown of pressure or displacement sensors, leading to additional costs and complexity, as existing systems require multiple sensors for accurate operation.
Innovation Solution
A system that estimates the displacement of a variable displacement hydraulic pump using a pressure sensor, valve position, and a controller, allowing for operation even with failed sensors by generating estimates of missing outputs, thereby reducing the need for redundant sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple sensors are used to monitor pump operation, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system creates a virtual copy of the displacement sensor signal by calculating it from pressure sensor data and valve position. Instead of requiring a physical displacement sensor, the controller computes an estimated displacement signal that replicates what a real sensor would provide, using the relationship between pressure, valve position, and pump displacement characteristics
Solution Approach 2:
The system uses valve position as an intermediary parameter to bridge the gap between pressure measurements and displacement estimation. The valve position provides information about the intended pump displacement, which combined with pressure data, allows the controller to infer actual displacement without a direct sensor
2Reliability
If the system shuts down upon sensor failure, then reliability is improved, but productivity is worsened
Solution Approach 1:
The system performs self-diagnosis and self-correction by detecting sensor failures and automatically switching to estimation mode. When a sensor failure is detected, the controller identifies the failed sensor and activates the appropriate estimation algorithm, allowing the system to continue operation without external intervention or shutdown
Solution Approach 2:
The system prepares estimation algorithms in advance that can compensate for sensor failures. By having pre-programmed estimation methods ready, the system can immediately switch to using calculated values when a sensor fails, cushioning against the impact of the failure and maintaining continuous operation
3Measurement precision
If additional sensors are installed, then measurement precision is improved, but loss of substance increases
Solution Approach 1:
The system replaces expensive physical sensors with virtual sensor copies generated through calculation. The estimated displacement and pressure values are computed from existing measurements and system parameters, eliminating the need to purchase and install additional expensive sensor hardware while maintaining measurement capability
Data Source
AI summary
A system for determining an estimated displacement of a variable displacement hydraulic pump includes a control cylinder associated with the swash plate of the variable displacement hydraulic pump to control the angle of inclination of the swash plate and a valve that controls the flow of hydraulic fluid to the control cylinder and has a position that defines an effective area of an opening of the valve. A pressure sensor generates pressure signals indicative of an output pressure from the variable displacement hydraulic pump. A controller is configured to receive pressure signals from the pressure sensor and determine an estimated displacement of the variable displacement hydraulic pump based upon the pressure signals from the pressure sensor and the position of the valve.