Hydraulic Cylinder Stall Strategy for Flow Redirection
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Solution Overview
Problem
Hydraulic systems in heavy equipment face inefficiencies and reduced controllability when an actuator stalls, leading to increased fluid pressure and reduced flow rates across all actuators, particularly in machines with a single pump or subset actuator stalls, affecting productivity and controllability.
Innovation Solution
A hydraulic control system with a controller that determines stall conditions and selectively adjusts fluid flow commands between actuators, implementing a flow-sharing strategy to redirect excess fluid from stalled cylinders to non-stalled ones, maintaining pump output and enhancing machine controllability and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pressurized fluid continues to be allocated to the stalled cylinder based on the displacement position of the operator interface device, then the system maintains velocity control based on operator input, but machine efficiency is reduced and system pressure rises abruptly
Solution Approach 1:
The controller continuously monitors the actual flow rate delivered to each actuator and compares it with the commanded flow rate. When a stall condition is detected (actual flow significantly less than commanded flow), the controller adjusts the flow distribution in real-time, reducing flow to the stalled actuator and redirecting it to non-stalled actuators, thereby maintaining efficiency while preserving velocity control for active actuators.
Solution Approach 2:
The system dynamically adjusts flow distribution based on real-time actuator performance. During normal operation, flow is allocated based on operator interface displacement. During stall conditions, the system transitions to a dynamic flow-sharing mode where flow commands are continuously modified to divert excess fluid from stalled actuators to non-stalled actuators, optimizing productivity while maintaining controllability.
2Reliability
If system pressure is controlled by the single highest pressure of any one actuator, then all actuators receive pressurized fluid, but flow rate to all actuators is needlessly reduced during single-actuator stall
Solution Approach 1:
The hydraulic system is segmented into independent flow control zones for each actuator. The controller independently manages flow distribution to each actuator based on its specific needs and operational state. During stall conditions, the stalled actuator's flow zone is decoupled from the system pressure regulation, allowing other actuator zones to maintain full flow rates without being constrained by the stalled actuator's high pressure requirement.
Solution Approach 2:
The system changes the pressure parameter management from a unified system-wide approach to a selective per-actuator approach. During stall detection, the controller modifies pressure regulation parameters specifically for the stalled actuator while maintaining normal pressure and flow parameters for non-stalled actuators, thereby preventing unnecessary flow reduction across the entire system.
3Reliability
If the pump destrokes to reduce pressures during stall, then pump stall is avoided, but controllability of other connected actuators is reduced
Solution Approach 1:
The excess flow that would cause pressure buildup in the stalled actuator is extracted and redirected to non-stalled actuators. The controller identifies the stalled actuator and diverts its commanded flow to other actuators that are actively moving, thereby preventing pump stall conditions without reducing the flow available to controllable actuators, maintaining full controllability.
Solution Approach 2:
The controller acts as an intermediary that mediates between the pump's constant flow output and the variable demands of multiple actuators. During stall conditions, it intermediates the flow distribution by redirecting excess flow from the stalled actuator to non-stalled actuators, preventing pump destruction while maintaining controllability of active actuators.
Data Source
AI summary
A hydraulic control system for a machine is disclosed. The hydraulic control system may have a hydraulic circuit, and a pump configured to supply pressurized fluid to the hydraulic circuit. The hydraulic control system may also have a first fluid actuator fluidly connected to receive pressurized fluid from the hydraulic circuit, a first valve arrangement movable to control a flow of fluid to the first fluid actuator, a second fluid actuator fluidly connected to receive pressurized fluid from the hydraulic circuit, and a second valve arrangement movable to control a flow of fluid to the second fluid actuator. The hydraulic control system may additionally have a controller in communication with the first and second valve arrangements. the controller may be configured to make a determination of a stall condition of the first fluid actuator, and to selectively change a flow command directed to the second valve arrangement based on the determination.