Die Cushion Control Device Speed Force Mode Switching
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Solution Overview
Problem
Conventional die cushion mechanisms using servo-motors face challenges in quickly and accurately controlling force responses due to significant pressure fluctuations during collisions, with issues like overshoot and delayed force detection affecting the accuracy and speed of force control.
Innovation Solution
A control device for a die cushion mechanism that employs a servo-motor with distinct control modes: an initial stage using speed control for rapid response and a succeeding stage using force control for accuracy, utilizing a force commanding section, a force detecting section, and a slide-speed detecting section to adjust speed commands accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If force control is used during collision, then force accuracy is improved, but response speed deteriorates due to integrator delay
Solution Approach 1:
The control system dynamically switches between two control modes: speed control mode during collision (initial stage) and force control mode during subsequent pressing operation (succeeding stage). This dynamic switching allows the system to achieve fast response during collision while maintaining accurate force control during the pressing operation, resolving the contradiction between response speed and force control accuracy.
2Device complexity
If simple control scheme change is used, then device complexity is reduced, but force control performance deteriorates during significant pressure fluctuation
Solution Approach 1:
The control process is segmented into two distinct stages: an initial stage during collision where speed control is applied, and a succeeding stage during pressing operation where force control is applied. This segmentation allows each stage to be optimized independently with the appropriate control method, improving overall force control performance without requiring complex integrated control schemes.
3Measurement precision
If force control is applied immediately during collision, then force accuracy is improved, but overshoot increases due to rapid pressure fluctuation
Solution Approach 1:
The system performs preliminary speed control during the collision phase to stabilize the cushion pad position before transitioning to force control. This preliminary action prevents excessive force fluctuation and overshoot that would occur if force control were applied immediately during the rapid pressure changes of collision, thereby improving force stability.
Data Source
AI summary
A device for controlling a die cushion mechanism including a servo-motor as a drive source and producing a force adapted to be applied to a slide in a press machine. The device includes a section for commanding a force to be produced by the die cushion mechanism; a section for detecting a force produced by the die cushion mechanism and applied to the slide; a section for detecting a moving speed of the slide; and a section for executing a force control on the servo-motor. The force controlling section executes force controls in mutually different modes on the servo-motor, through mutually different control loops, one mode being provided for an initial stage defined from an instant when the die cushion mechanism starts producing the force to be applied to the slide until a predetermined subsequent instant, and another mode being provided for a succeeding stage defined after the predetermined subsequent instant, by using at least a slide-speed detected value detected by the slide-speed detecting section. The force controlling section includes a section for preparing a first speed-command value to be commanded to the servo-motor in the initial stage and a second speed-command value, different from the first speed-command value, to be commanded to the servo-motor in the succeeding stage.