Pilot Valve Neutral Current Control for Swashplate Stability
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Solution Overview
Problem
Existing hydraulic pressure medium supply arrangements for mobile working machines face challenges in controlling pressure and flow efficiently, leading to vibrations during operation and suboptimal adjustment behavior.
Innovation Solution
A hydraulic pressure medium supply arrangement with an adjustable axial piston machine, an electrically proportional controllable pilot valve, and a controller that pre-controls the neutral current to maintain the valve spool in a middle position, reducing vibrations and improving dynamic response by linking the pre-control variable with the manipulated variable and adapting the characteristic map based on operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pilot valve with basic neutral position control is used, then the structure is simple, but vibrations occur during operation and adjustment behavior is suboptimal
Solution Approach 1:
The controller pre-calculates and applies the neutral current value before the pilot valve actuator reaches its neutral position, based on the actual swivel angle feedback. This anticipatory control prevents oscillations and vibrations by ensuring the valve is already positioned correctly when the actuator arrives, rather than reacting after deviation occurs.
Solution Approach 2:
The system continuously monitors the actual swivel angle of the hydraulic machine and feeds this information back to the controller. The controller uses this feedback to dynamically adjust the neutral current value, creating a closed-loop control system that eliminates vibrations by constantly correcting the valve position based on actual system state.
2Manufacturing precision
If the pilot valve neutral position is fixed, then the control system is simple, but manufacturing tolerances cause deviations and suboptimal performance
Solution Approach 1:
The system dynamically changes the neutral current parameter based on the actual swivel angle feedback. Instead of using a fixed neutral position that is affected by manufacturing tolerances, the controller continuously adjusts the neutral current value to compensate for tolerances and maintain precise control, thereby improving manufacturing precision through adaptive parameter modification.
Solution Approach 2:
The controller pre-adjusts the neutral current value based on anticipated operating conditions and feedback from the actual swivel angle. This preliminary adjustment compensates for manufacturing tolerances before they cause performance deviations, ensuring the pilot valve maintains accurate neutral positioning across varying operating conditions.
3Productivity
If rapid adjustment of the hydraulic machine is implemented, then productivity is improved, but overshoots and vibrations increase
Solution Approach 1:
The controller applies preliminary counteracting control by pre-calculating the neutral current value that will counterbalance the system's momentum and prevent overshoot. When rapid adjustment is commanded, the system anticipates potential overshoot and applies an opposing control action in advance, allowing fast response while maintaining stability and preventing vibrations.
Solution Approach 2:
The continuous feedback loop monitors the actual swivel angle and dynamically adjusts the neutral current to prevent overshoot during rapid adjustments. The feedback mechanism detects approaching target positions and automatically modulates the control signal to reduce gain near the target, enabling fast adjustments without overshoot or vibrations.
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 solution significantly reduces vibrations and enhances the dynamic response of the hydraulic pressure medium supply arrangement, ensuring precise control and minimal overshoots by automatically adapting to changing conditions and compensating for manufacturing tolerances.
Implementation Method 1
A pilot valve (14) with a valve spool (14.1) is provided. This is used to control an inflow and/or an outflow into a control chamber (46) of an actuating cylinder (34)
Implementation Method 2
the actuating piston (36) does not move, which means that the hydraulic machine or the pressure medium supply arrangement (1) can be in a stationary state
Data Source
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AI summary
A hydraulic pressure medium supply arrangement with a hydraulic machine featuring an adjustable swashplate is disclosed. The angle of the swashplate is adjustable via a pilot valve. The pilot valve is controlled by a controller. When the pilot valve is actuated with a neutral flow, a spool of the pilot valve assumes a neutral position in which the swashplate does not move. To control the pilot valve, the controller outputs a manipulated variable. This manipulated variable is then linked and adapted on the controller's output side to a pilot control variable for the neutral flow in order to pre-control the neutral flow.