Hydraulic Cushion Control for Accurate Work Machine Stroke-End Deceleration
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Solution Overview
Problem
The flow force acting on the control valve in hydraulic cushion control systems can make it difficult to achieve precise control of the working equipment velocity, leading to inadequate cushion effects and reduced operability.
Innovation Solution
A work machine control system that includes a hydraulic pump, hydraulic cylinder, flow paths, flow rate control valves, bleed valves, and a control device that adjusts hydraulic oil flow rates based on posture sensor data to manage the working equipment's position and velocity, particularly near the end of its range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If cushion control is implemented using a control valve, then impact reduction is achieved, but flow force acts on the control valve making velocity control inaccurate
Solution Approach 1:
The hydraulic system is segmented into two independent flow paths: a first flow path for supplying hydraulic oil to the hydraulic cylinder, and a second flow path for discharging hydraulic oil to the tank. This segmentation allows independent control of each path, enabling the second path to be optimized for cushion control without interfering with the velocity control in the first path.
Solution Approach 2:
The cushion control function is extracted from the main velocity control system by creating a separate second flow path with its own bleed valve. This extraction removes the source of flow force interference from the velocity control system, allowing accurate velocity control while maintaining effective cushion control.
2Device complexity
If the control valve is used for both velocity control and cushion control, then device complexity is reduced, but operability deteriorates due to flow force interference
Solution Approach 1:
The control system is segmented into two independent control paths with separate control valves: a flow rate control valve for velocity control and a bleed valve for cushion control. This segmentation eliminates the flow force interference that occurs when a single control valve handles both functions, thereby improving operability while maintaining reasonable system complexity.
3Speed
If hydraulic oil flow rate is not adjusted near the end position, then response speed is maintained, but cushion effect becomes inadequate
Solution Approach 1:
The control device receives feedback from a posture sensor that detects the position of the working equipment element. Based on this feedback, the control device determines when the element is in the end section and automatically adjusts the flow rate of hydraulic oil discharged to the tank through the bleed valve, enabling adaptive cushion control that maintains both response speed and adequate cushion effect.
Solution Approach 2:
The system dynamically adjusts the flow rate of hydraulic oil discharged to the tank based on the real-time position of the working equipment element. When the element is in the end section, the flow rate is reduced to provide cushioning; when outside the end section, normal flow rate is maintained for responsive operation. This dynamic adjustment ensures both speed and cushion effect are optimized at different operational phases.
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
This system enables precise control of the working equipment, ensuring an appropriate cushion effect and improved operability by accurately managing hydraulic oil flow rates through the use of posture sensors and control commands.
Implementation Method 1
a hydraulic pump; a hydraulic cylinder that operates a working equipment element in a movable range based on hydraulic oil supplied from the hydraulic pump
Implementation Method 2
a flow rate control valve that adjusts a flow rate of the hydraulic oil supplied to the hydraulic cylinder
Implementation Method 3
a bleed valve that adjusts a flow rate of the hydraulic oil discharged to a tank via the second flow path
Implementation Method 4
a posture sensor that detects a posture of the working equipment element in the movable range
Data Source
AI summary
A work machine control system includes: a pump; a cylinder operating a working equipment element in a movable range based on hydraulic oil supplied from the pump; a first path connected to the pump; a second path branching from the first path; a control valve adjusting the flow rate of the oil supplied to the cylinder via the first path; a bleed valve adjusting the flow rate of the oil discharged to a tank via the second path; a sensor detecting a posture of the element in the range; and a control device outputting a first command for adjusting the flow rate of the oil supplied to the cylinder and a second command for adjusting the flow rate of the oil discharged to the tank when the element is determined to be present in an end section of the range based on detection data of the sensor.