Servo Press Control Device Torque Limiting Overload Protection
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Solution Overview
Problem
Existing servo press control systems fail to adequately protect the drive system and machine from overload, particularly during variable motor speed operations, as they do not account for fluctuating torque generated by inertial and friction forces, leading to potential damage from excessive torque during pressing tasks like drawing, which require different torque profiles than blanking.
Innovation Solution
A control device and method for a servo press that includes an encoder for position data, a press information storage unit, a motion data setting unit, a motion calculation unit, a torque calculation unit, a process system limit unit, and a drive system limit unit, which calculate and limit process torque and control torque to prevent overload by determining slide target positions and adjusting motor torque based on predetermined torque capabilities of the press and drive system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If motor torque is increased to satisfy the stroke pressure diagram, then sufficient pressing force is achieved, but the drive system is damaged due to excessive torque
Solution Approach 1:
The patent applies dynamics by making the motor torque variable rather than constant. The control device dynamically adjusts motor torque based on the slide position and pressing requirements, ensuring sufficient torque is provided only when needed during the pressing cycle, while reducing torque during non-pressing phases to protect the drive system from excessive loads.
Solution Approach 2:
The patent changes the torque parameter dynamically throughout the pressing cycle. By monitoring slide position and pressing load, the control device adjusts the motor torque parameter in real-time, increasing it to meet pressing force requirements when the slide is in the pressing zone, and decreasing it during other phases to prevent drive system damage.
2Adaptability or versatility
If motor speed is made variable during pressing, then pressing flexibility is improved, but overload protection fails due to fluctuating torque from acceleration and deceleration
Solution Approach 1:
The patent implements feedback by continuously monitoring slide position, pressing load, and motor speed, then using this information to adjust motor torque in real-time. The control device receives feedback from sensors and modifies the torque output to maintain reliable overload protection even while allowing variable motor speeds for different pressing operations.
Solution Approach 2:
The patent applies preliminary anti-action by calculating and limiting the maximum allowable motor torque in advance based on drive system capabilities and current operating conditions. Before torque fluctuations from acceleration or deceleration can cause damage, the control device has already established torque limits that prevent excessive loads, thereby protecting the drive system proactively.
3Strength
If motor torque is limited to protect the drive system, then drive system durability is improved, but pressing force capability is reduced
Solution Approach 1:
The patent resolves this contradiction through dynamic torque management. The motor torque limit is not fixed but adjusts dynamically based on slide position, pressing load, and required pressing force. When the slide enters the pressing zone and high force is required, the torque limit is increased to provide sufficient pressing capability. When the slide is in non-pressing zones, the torque limit is reduced to protect the drive system, thus achieving both durability and force capability.
Data Source
AI summary
A control system of a servo press and a control method are provided for preventing an overload on a pressure capability of a press and a torque capability of a drive system. A control device of a servo press for pressing by transferring a drive force of a servomotor to a slide via a drive mechanism includes: a motion calculation unit for calculating slide target position data; a torque calculation unit for calculating process torque for pressing and control torque for speed change of the servo motor on the basis of slide target position data; a process system limit unit for limiting the calculated process torque to predetermined process limitation torque; and a drive system limit unit for limiting combined torque of the limited process torque and the control torque to predetermined drive limitation torque. The servo motor is driven on the basis of a command of drive limitation torque.