Pump-Controlled Hydraulic Circuit for Single-Rod Cylinder Stability
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Solution Overview
Problem
Pump-controlled hydraulic circuits for single-rod cylinders face instability and energy inefficiencies due to throttling losses and dynamic performance issues, particularly in low loading conditions and high-speed operations, where existing solutions require additional control effort and sensors, increasing system complexity and cost.
Innovation Solution
A pump-controlled hydraulic circuit design incorporating a reversible hydraulic pump, main fluid lines, a hydraulic charging system, and a set of valves including pilot-operated critical zone shifting and vibration-damping valves, which operate in a four-quadrant mode to reduce oscillations and energy losses by shifting critical loading zones to lower loading ranges and throttling only in critical zones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pump-controlled circuits are used for single-rod cylinders, then energy efficiency is improved, but instability and oscillations occur in low loading conditions
Solution Approach 1:
The circuit dynamically switches between different operational modes (pumping mode and motoring mode) based on loading conditions. The reversible pump changes its displacement direction to match the load requirements, allowing the system to adapt to varying load conditions and maintain stability while preserving energy efficiency.
Solution Approach 2:
The system changes the pump's displacement parameter (swash plate angle) to control flow direction and magnitude. By adjusting the pump displacement parameter, the circuit can operate efficiently across different loading conditions without causing instability or oscillations.
2Productivity
If high-speed operation is achieved, then productivity is improved, but oscillations and instability increase in low loading conditions
Solution Approach 1:
The circuit enables dynamic operation at high speeds by allowing the pump to rapidly change flow direction and magnitude. The reversible pump can quickly switch between extending and retracting modes, maintaining high productivity while avoiding oscillations through proper mode selection.
Solution Approach 2:
The circuit maintains continuous useful action by ensuring the pump always operates in a productive mode (either pumping or motoring). This eliminates idle periods and maintains high-speed operation continuity while preventing instability through consistent energy utilization.
3Speed
If valve-controlled circuits are used, then dynamic performance is improved, but energy consumption increases due to throttling losses
Solution Approach 1:
The patent replaces traditional valve-controlled mechanical systems with a pump-controlled hydraulic system. Instead of using throttle valves to control flow and speed (which cause energy losses), the system uses a reversible pump to directly control fluid delivery, eliminating throttling losses while maintaining dynamic performance.
Solution Approach 2:
The system changes from passive flow control via valves to active flow generation via pump displacement control. By varying the pump's displacement parameter, the circuit achieves dynamic performance without the energy-wasting throttling effects of valve-controlled systems.
4Stability of the object's composition
If additional control valves and sensors are added to stabilize the circuit, then system stability is improved, but device complexity and cost increase
Solution Approach 1:
The circuit achieves stability through self-regulating mechanisms inherent in the pump-controlled architecture. The reversible pump's ability to naturally adapt to load conditions and the hydraulic circuit's inherent feedback mechanisms provide stability without requiring additional external control valves or sensors.
Solution Approach 2:
The reversible pump performs multiple functions: it provides flow control, pressure control, and stability regulation simultaneously. This multi-functionality eliminates the need for separate control components, reducing system complexity while maintaining stability.
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 enhances the dynamic performance and energy efficiency of single-rod hydraulic actuators by reducing oscillations and energy consumption, achieving stable operation across various loading conditions without the need for additional electronic control, while maintaining energy regeneration capabilities.
Implementation Method 1
a hydraulic charging system for supplying/releasing charging fluid to and from the first and second main fluid lines to compensate for differential flow on opposing sides of the differential hydraulic actuator
Implementation Method 2
A cross-pressure line connecting between the main fluid lines LA, LB has a singular connection to the charging system 14, which features an accumulator 20 to boost the charge pump and supplement flow to the circuit when needed
Data Source
AI summary
Pump-controlled hydraulic circuits are more efficient than valve-controlled circuits, as they eliminate the energy losses due to flow throttling in valves and require less cooling effort. Presently existing pump-controlled solutions for single rod cylinders encounter an undesirable performance during certain operating conditions. Novel circuit designs employ use of different charge pressures on a pair of pilot-operated charging-control valves or different piston areas and/or spring constants on a shuttle-type charging control valve to shift a critical loading region in a load-force/actuator-velocity plane to a lower load force range, thereby reducing the undesired oscillations experienced in the response of the typical critical loading region. One or more specialized valves are controlled by fluid pressures to provide throttling in the circuit only within the critical loading region, thereby reducing the oscillatory amplitude while avoiding throttling-based energy losses outside the critical region over the majority of the circuit's operational overall operating area.