Electric Proportional Valve Pressure Margin Control
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Solution Overview
Problem
Electric proportional valves in hydraulic excavators face spool repositioning issues due to flow forces, leading to incorrect pressure margins, which can cause operational failures, especially in attachments like grapples that require rapid hydraulic fluid flow, and conventional feedback loop strategies are insufficient for recalibration within short time frames.
Innovation Solution
A method involving a feed-forward command to determine and adjust the spool position of the electric proportional valve by calculating pressure deviations and applying electric input offsets to align the actual pressure differential with the desired differential, using a control unit connected to both the valve and hydraulic pump, allowing for recalibration independent of the hydraulic actuator type.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback loop strategies are used to control the electric proportional valve, then the valve can be controlled based on pressure feedback, but the recalibration cannot be completed within short time frames required for rapid flow applications
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing calibration data in lookup tables before operation. The controller retrieves pre-computed spool position commands based on desired pressure differentials and flow rates, eliminating the need for real-time iterative feedback calculations. This allows rapid recalibration for attachments like grapples that require fast response times.
2Productivity
If the hydraulic pump operates at high flow rates to meet rapid attachment demands, then productivity increases, but the spool repositioning accuracy decreases due to flow forces
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual pressure differential across the proportional valve and comparing it with the desired pressure differential. The controller uses this feedback to retrieve appropriate calibration data from lookup tables and adjust the spool position command accordingly, maintaining accuracy even at high flow rates where flow forces would otherwise cause repositioning errors.
3Measurement precision
If the electric proportional valve is designed for high precision pressure control, then pressure margin accuracy improves, but the device complexity increases
Solution Approach 1:
The patent reduces control system complexity by pre-computing and storing calibration data in lookup tables during manufacturing or initial setup. During operation, the controller simply retrieves pre-calculated spool position commands based on desired pressure differentials and flow rates, avoiding the need for complex real-time calculations or additional sensors, thus maintaining measurement precision while simplifying the control architecture.
Data Source
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AI summary
A method for controlling an electric proportional valve (42) of a hydraulic excavator attachment (28) is disclosed. The electric proportional valve (42) is controllable based on an electric input to the electric proportional valve (42). The electric proportional valve (42) is connected to a hydraulic actuator (34) for actuating the hydraulic excavator attachment (28) and to a hydraulic pump (36) for providing a flow of hydraulic fluid to the electric proportional valve (42). The method comprises operating the hydraulic pump (36) at a desired flow rate depending on the hydraulic excavator attachment (28); setting a desired pressure differential (Δp) over the electric proportional valve (42); determining an actual pressure differential (Δp') over the electric proportional valve (42); determining a pressure deviation (Δp - Δp') between the desired pressure differential (Δp) and the actual pressure differential (Δp'); and operating the electric proportional valve (42) such that the actual pressure differential (Δp') approaches the desired pressure differential (Δp).