Hydraulic Drive Control for Piston Positioning Accuracy
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Solution Overview
Problem
Hydraulic drive devices in machines like punching, embossing, and bending machines face inaccuracies and inefficiencies due to deviations between desired and actual piston positions, leading to prolonged process times and reduced precision.
Innovation Solution
A method where the setpoint for a hydraulic drive device is initially set below the bottom dead center and then reversed above the top dead center, with switchover values and override positions selected to maintain a large deviation between desired and actual values, ensuring continuous operation and rapid piston movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If proportional control is used with a displaceable valve piston, then the valve can be controlled faster than the massive working piston, but the actual value of piston position deviates from the setpoint due to inertial forces
Solution Approach 1:
The control method anticipates the piston's inertial behavior by setting the valve opening in advance to compensate for expected position deviations. The control device calculates the required valve opening based on the relationship between valve piston position and working piston position, proactively adjusting the valve to ensure the working piston reaches the desired setpoint despite its mass and inertia.
Solution Approach 2:
The system continuously monitors the actual position of the working piston and uses this feedback to adjust the valve opening dynamically. The control device determines the valve opening as a function of the actual working piston position, creating a closed-loop control system that corrects deviations in real-time and ensures accurate positioning.
2Ease of operation
If proportional control is used, then the valve opening changes proportionally to the deviation from setpoint, but the volume flow decreases when the actual value approaches the setpoint, delaying movement
Solution Approach 1:
The control method transforms the control parameter from a simple proportional relationship to a more complex functional relationship between valve opening and working piston position. Instead of linear proportional control, the system uses a predetermined function that optimizes the volume flow characteristics, ensuring sufficient flow rate even when approaching the setpoint to minimize positioning time.
Solution Approach 2:
The system pre-calculates the optimal valve opening sequence based on the desired piston motion profile. By anticipating the required flow characteristics throughout the motion cycle, the control device maintains higher volume flows longer into the approach phase, preventing the deceleration effect that occurs with simple proportional control near the setpoint.
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 approach significantly reduces the control time and process duration for double strokes while maintaining precision, enhancing economic efficiency and accuracy.
Implementation Method 1
the hydraulic cylinder-piston unit for moving the working piston is supplied with hydraulic fluid via a proportional valve
Implementation Method 2
the valve piston can be controlled much faster than the massive working piston due to its usually lower mass. A change in the setpoint can therefore take place comparatively quickly, whereas the speed of the change in position of the working piston is limited by inertial forces.
Data Source
Figure 1
Figure 2a~2b
AI summary
The invention relates to a method for operating a hydraulic driving device (10) with a hydraulic cylinder-piston unit (12) having a working piston (16) which is movable along a working direction (14) between an upper dead centre and a lower dead centre, wherein a desired value for the position of the working piston along the working direction is predetermined, and an actual value of the position of the working piston along the working direction is detected, and the movement of the working piston is regulated depending upon the desired value and the actual value. The invention further relates to a hydraulic driving device (10).