Feed Axis Control Device Cascade Velocity Feedback
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Solution Overview
Problem
Existing methods for controlling servo motors in machine tools are insufficient in handling unpredictable disturbances, as they rely on predicted processing loads that fail to account for unforeseen fluctuations, leading to instability and reduced suppression of disturbances.
Innovation Solution
A feed axis control method and device that incorporate a cascade connection of a velocity feedback loop within a position feedback loop, utilizing state feedback signals to stabilize the control system by subtracting specific gain-multipled outputs from the torque command, allowing for increased feedback gain and effective suppression of disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If predicted processing load is calculated and added to acceleration command to cope with servo control delay, then response to predictable loads is improved, but inability to handle unpredictable disturbances worsens control effectiveness
Solution Approach 1:
The patent implements state feedback by multiplying the output of the feedback loop by a gain and subtracting it from the torque command. This feedback mechanism enables the system to respond to actual system states including unpredictable disturbances, not just predicted loads, thereby improving adaptability while maintaining control effectiveness.
Solution Approach 2:
The patent changes the control parameter from predicted load compensation to state feedback with gain multiplication. By using the actual output of the feedback loop and multiplying by a gain, the system adapts to varying conditions including unpredictable disturbances, resolving the contradiction between reliability and adaptability.
2Object-affected harmful factors
If feedback gain is increased to suppress disturbances more effectively, then disturbance suppression is improved, but system stability deteriorates
Solution Approach 1:
The patent uses state feedback where the output of the feedback loop is multiplied by a gain and subtracted from the torque command. This feedback structure allows the system to achieve strong disturbance suppression while maintaining stability through proper gain selection, as the feedback automatically adjusts to system conditions.
Solution Approach 2:
The patent makes the control system dynamic by using state feedback with gain multiplication rather than fixed gain. This allows the system to adapt its response based on actual operating conditions, achieving both stability and effective disturbance suppression across varying conditions.
3Stability of the object's composition
If state feedback is subtracted from torque command with gain multiplication, then system stability is improved and feedback gain can be increased, but control complexity increases
Solution Approach 1:
The patent implements state feedback by multiplying the feedback loop output by a gain and subtracting from the torque command. This approach achieves improved stability and allows higher feedback gains while adding only one multiplication operation and one subtraction operation to the existing control structure, representing minimal increase in complexity for significant performance improvement.
Data Source
AI summary
A working machine feed axis control device: disposes a velocity feedback loop and forms a cascade coupling on the inner side of a location feedback loop; comprises a velocity gain setting apparatus (30) which multiplies the output of the velocity feedback look by a first gain (kv), and a location gain setting apparatus (31) which multiplies the output of the location feedback loop by a second gain (kp); subtracts the output of the velocity gain setting apparatus (30) and the output of the location gain setting apparatus (31) from a torque instruction (τ); and outputs the remaining torque instruction (τ) to a subject to be controlled (27).