Work Machine Hydraulic Velocity Compensation for Region Stability
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Solution Overview
Problem
In work machines using positive flow control systems and open-centered control valves, the actual velocity of hydraulic actuators can differ from estimated velocities during combined operations, leading to unstable behavior due to prioritization of flow to larger actuators, causing hunting or instability.
Innovation Solution
A work machine with an articulated work device and multiple hydraulic actuators, flow control valves, and a controller that computes and adjusts estimated velocities based on predefined relations to stabilize operation, ensuring the work device operates within a target region by region limiting control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a positive flow control system with open-centered control valves is used to prioritize pump flow to actuators with larger operation amounts, then productivity is improved, but the actual velocity of actuators differs from estimated velocity during combined operations, causing instability
Solution Approach 1:
The controller computes estimated velocities for multiple actuators based on pump flow rate and metering characteristics, then compares these estimated velocities with target velocities. The control signal to the directional control valve is adjusted based on this comparison, creating a feedback mechanism that compensates for the velocity deviations caused by positive flow control prioritization, thereby stabilizing actuator operation during combined operations
Solution Approach 2:
The system dynamically adjusts the control signal parameters to the directional control valve based on computed estimated velocities and target velocities. By changing the control signal parameters in response to velocity deviations, the system compensates for the flow prioritization effect and maintains stable actuator velocities during combined operations
2Measurement precision
If the controller computes estimated velocity based on metering characteristics during combined operation, then measurement precision is maintained, but the actual velocity becomes faster than estimated velocity due to increased pump flow rate, causing hunting behavior
Solution Approach 1:
The controller uses feedback by comparing the estimated velocity (computed from metering characteristics) with the target velocity, then adjusts the control signal to the directional control valve. This feedback loop compensates for the velocity increase caused by positive flow control, preventing hunting behavior while maintaining accurate velocity estimation
Solution Approach 2:
The controller computes the estimated velocity in advance and uses this information to preemptively adjust the control signal to counteract the velocity increase that would otherwise occur due to positive flow control prioritization. This preliminary anti-action prevents hunting behavior before it can manifest
Data Source
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AI summary
When an operation amount of an operation lever 1a or 1b corresponding to a boom cylinder 5 is equal to or smaller than an operation amount of an operation lever 1a or 1b corresponding to an arm cylinder 6, an estimated velocity of the arm cylinder used for region limiting control is computed on the basis of a first condition defining, in advance, a relation between the operation amount of the operation lever 1a or 1b and the estimated velocity of the arm cylinder 6. When the operation amount of the operation lever 1a or 1b corresponding to the boom cylinder 5 is larger than the operation amount of the operation lever 1a or 1b corresponding to the arm cylinder 6, the estimated velocity of the arm cylinder 6 used for the region limiting control is computed as a velocity higher than the estimated velocity of the arm cylinder 6 computed on the basis of the first condition. The behavior of a work device can thereby be stabilized.