Motor Drive Control Device for Power Limiting
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Solution Overview
Problem
Existing motor drive control devices for machine tools face challenges in effectively limiting the combined output of servo and spindle motors without adversely affecting cutting operations, particularly during high load conditions, leading to potential machine tool stoppages and reduced efficiency.
Innovation Solution
A motor drive control device with a first and second control unit that adjusts the alternating-current power to the servo and spindle motors based on predicted power supply limits, reducing feed speed during cutting operations and limiting torque during non-cutting operations, while monitoring DC link voltage to prevent output exceeding the rectifier's capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the torque of the servo motor is limited to prevent output exceeding rectifier capacity, then the sum of motor outputs is controlled, but the feed speed and tracking precision deteriorate
Solution Approach 1:
The control device dynamically changes the parameter being limited based on operating conditions. During cutting operations, it limits feed speed instead of torque to maintain cutting performance. During non-cutting operations, it limits torque to prevent power overload. This conditional parameter switching resolves the contradiction between power control and speed maintenance.
2Power
If the torque of the spindle motor is limited to prevent output exceeding rectifier capacity, then the sum of motor outputs is controlled, but the cutting operation is adversely affected
Solution Approach 1:
The control device switches the limited parameter based on operation type. During cutting operations, it maintains spindle torque to ensure cutting continuity and only limits feed axis speed. During non-cutting operations, it limits spindle torque to prevent power overload. This resolves the contradiction between power control and cutting productivity.
3Device complexity
If a smaller rectifier unit is used to reduce installation space and cost, then equipment size and cost are reduced, but the risk of power shortage increases
Solution Approach 1:
The control device continuously monitors the actual power consumption of motors and compares it with the rectifier unit's capacity. When the sum of motor outputs approaches the rectifier capacity, the system automatically limits appropriate parameters (feed speed or torque) to prevent power overload. This feedback mechanism ensures reliable operation with a smaller rectifier unit by dynamically adjusting motor output to match available power capacity.
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 solution allows for effective limitation of motor output without disrupting cutting operations, reducing the risk of machine tool stoppages and enabling the use of smaller, less costly rectifier units by optimizing power distribution between servo and spindle motors.
Implementation Method 1
a first inverter unit to which one rectifier unit configured to convert alternating-current voltage or alternating current into direct-current voltage or direct current is connected
Implementation Method 2
which is configured to convert the direct-current voltage or direct current supplied from the rectifier unit into alternating-current voltage or alternating current and to supply the converted alternating-current voltage or alternating current
Data Source
AI summary
If it is predicted that the sum of the output of a servo motor and the output of a spindle motor exceeds power supplied by a rectifier unit, during a cutting operation, a motor drive control device controls alternating-current power of a first inverter unit so as to reduce the feed speed of at least one feed axis and controls alternating-current power of a second inverter unit so as not to limit torque of the spindle motor. Further, if it is predicted that the sum of the output of the servo motor and the output of the spindle motor exceeds power supplied by the rectifier unit, during an operation other than the cutting operation, the motor drive control device controls the alternating-current power of the second inverter unit so as to limit the torque so as not to reduce the feed speed.