Hydraulic Actuator Valve Start Position for Stable Slewing Control
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Solution Overview
Problem
Hydraulic actuators, such as those in cranes, experience variable dead bands and oscillations due to static friction and inertia, leading to inefficient energy consumption and controllability issues during slewing movements, especially under varying load conditions.
Innovation Solution
The method involves pre-adjusting the start position of the valve element based on parameters outside the hydraulic actuator, such as load-dependent and geometry-related factors, using a look-up table and auxiliary drives to minimize dead band and optimize control, allowing for precise actuator movement without direct mechanical connection to the input device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flow-controlled valve section is used to control the hydraulic actuator, then the actuator can be controlled to move, but static friction overcoming leads to pressure overshoot and oscillating movement
Solution Approach 1:
The valve element is pre-adjusted to a start position that anticipates the pressure needed to overcome static friction before the actuator begins moving. This preliminary positioning of the valve element ensures that sufficient pressure is available immediately when movement is initiated, preventing pressure overshoot and subsequent oscillations.
Solution Approach 2:
The system dynamically adjusts the valve element position based on real-time parameters such as actuator position, velocity, and load conditions. This dynamic adjustment allows the valve to adapt to changing friction characteristics and load requirements, maintaining stable operation across different operating conditions.
2Stability of the object's composition
If back pressure is added to the flow-controlled input to reduce oscillations, then oscillations are reduced, but power consumption increases
Solution Approach 1:
Instead of maintaining constant back pressure, the system changes the pressure parameter dynamically based on operating conditions. The valve element position is adjusted according to actuator position, velocity, and load parameters, providing pressure compensation only when needed to overcome static friction and prevent oscillations, rather than continuously consuming power.
3Stability of the object's composition
If a pressure control valve is used to control fixed pressure and dampen oscillations, then oscillations are controlled, but load dependent dead band and load dependent flow occur
Solution Approach 1:
The system uses feedback from multiple sensors measuring actuator position, velocity, acceleration, and load parameters to continuously adjust the valve element position. This feedback mechanism allows the system to adapt to varying load conditions in real-time, maintaining consistent performance and eliminating load-dependent dead bands by compensating for friction and inertia effects based on actual operating conditions.
4Device complexity
If the valve element is directly mechanically connected to the input device, then the control structure is simple, but the dead band is variable and depends on forces acting on the actuator
Solution Approach 1:
An electronic or hydraulic intermediary system is introduced between the input device and the valve element. This intermediary uses sensors and control logic to calculate the optimal valve element position based on actuator parameters and load conditions, then positions the valve element accordingly. This eliminates the direct mechanical connection while providing consistent, predictable control without variable dead bands.
Data Source
AI summary
A method for controlling a hydraulic actuator (2) of a system (1) by means of a valve having a valve element is described. A position of the valve element determines a pressure supplied to a hydraulic actuator (2). In such a method a variable dead band should be minimized. To this end a start position of the valve element is preadjusted as a function of at least one parameter outside the hydraulic actuator (2).