Servo Motor Drive System Abnormality Detection and Output Limiting
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Solution Overview
Problem
In motor drive systems, when an abnormality occurs in the power storage device, the power consumption or regenerative power of the servomotor exceeds the maximum output of the power supply unit, potentially leading to abnormal operation or breakage, resulting in economic losses and safety hazards due to the need to stop machines like machine tools and robots.
Innovation Solution
A motor drive system with an abnormality detection unit that limits the output of the servomotor when an abnormality is detected in the power storage device, ensuring the output does not exceed the maximum supply power of the power supply unit, thereby preventing damage and maintaining efficient operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power storage device is provided to the DC link to reduce power peak, then the power supply unit capacity can be reduced, but when abnormality occurs in the power storage device, the power consumption or regenerative power exceeds the maximum output of the power supply unit, potentially causing abnormal operation or breakage
Solution Approach 1:
The control unit performs preliminary detection of abnormalities in the power storage device and takes preventive action by limiting the servomotor output before damage can occur. When an abnormality is detected, the control unit proactively restricts the power output to levels the power supply unit can handle, preventing potential breakage of the power supply unit or servo amplifier.
Solution Approach 2:
The control unit continuously monitors the state of the power storage device and adjusts the servomotor output based on this feedback. When an abnormality is detected through monitoring, the control unit responds by limiting the output power, creating a closed-loop control system that adapts to the actual system state to prevent damage.
2Reliability
If the servomotor output is limited when abnormality is detected, then the power supply unit and servo amplifier are protected from damage, but the output of the servomotor must be reduced, affecting productivity
Solution Approach 1:
Instead of completely stopping the servomotor when an abnormality is detected, the control unit applies partial action by limiting the output to a reduced but still functional level. This allows the system to continue operating at reduced capacity rather than shutting down completely, maintaining some productivity while protecting the power supply unit and servo amplifier from damage.
3Loss of energy
If the power storage device is used to store regenerative power, then the power peak is reduced, but when abnormality occurs, the regenerative power cannot be stored, causing power imbalance
Solution Approach 1:
The control unit applies preliminary anti-action by preemptively limiting the servomotor output when an abnormality in the power storage device is detected. This prevents the situation where regenerative power cannot be stored by avoiding operations that would generate excessive regenerative power, thus maintaining power balance and preventing damage to the power supply unit.
Data Source
AI summary
A motor drive system includes a power supply unit configured to supply DC power to a DC link, a servo amplifier for drive configured to convert the DC power in the DC link to AC power and supplies the AC power to the servomotor for drive as a driving power, a power storage device configured to store DC power from the DC link or supplies DC power to the DC link, an abnormality detection unit configured to detect the abnormality of the power storage device, and a control unit configured to, when the abnormality detection unit detects the abnormality of the power storage device, control the operation of the servo amplifier for drive such that the output of the servomotor for drive is limited to a value smaller than the output before the abnormality detection by the abnormality detection unit.