Robot Servo Control for Stable Power Shutdown
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Solution Overview
Problem
Industrial robot servo systems face instability in stopping positions due to unpredictable power shutdowns, leading to prolonged restart times, as existing safety units struggle to maintain control over servo motors effectively.
Innovation Solution
A robot system equipped with a controller, encoder, and monitoring section that compares control signals with output signals to generate a power shutoff command only when the difference exceeds a threshold, ensuring controlled motor operations and stable stop positions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the safety unit stops the supply of electric power to the servo motor when detecting abnormality, then the safety of the robot system is improved, but the stop position of the rotation shaft becomes unstable and restart time increases
Solution Approach 1:
The monitoring unit performs preliminary monitoring of the difference between command values and feedback values before complete failure occurs. By detecting trends and generating warnings in advance, the system can prepare for potential shutdowns and reduce restart time by maintaining optimal positions during the transition to shutdown mode.
Solution Approach 2:
The system cushions the impact of power shutdown by implementing a multi-stage response: first generating warning signals when abnormalities are detected, then gradually reducing motor operation, and finally shutting down power only when necessary. This cushioning approach minimizes sudden position changes and reduces restart time.
2Measurement precision
If the monitoring unit continuously monitors the difference between command values and feedback values, then the detection precision of abnormalities is improved, but the device complexity increases
Solution Approach 1:
The monitoring unit is designed to perform multiple functions: it monitors the difference between command and feedback values, detects abnormalities, generates warning signals, and controls the shutdown timing. By consolidating these functions into a single multi-functional unit, the system achieves high detection precision without proportionally increasing overall system complexity.
Solution Approach 2:
The monitoring unit continuously receives feedback values from the servo driver and compares them with command values. This feedback mechanism enables precise detection of abnormalities while using existing system components, thereby achieving high measurement precision without significant additional complexity.
3Manufacturing precision
If the controller transmits control signals at high frequency for precise control, then the control precision is improved, but the difference between command values and feedback values increases making false abnormality detection more likely
Solution Approach 1:
The determination of abnormality is made dynamically based on the temporal pattern of differences between command and feedback values. The monitoring unit considers whether the difference persists across multiple control signal cycles rather than reacting to single-instance variations, enabling reliable detection even during high-frequency precise control operations.
Solution Approach 2:
The monitoring unit performs periodic comparison of command and feedback values at regular intervals synchronized with the control signal frequency. This periodic monitoring approach distinguishes between normal high-frequency control variations and actual abnormalities, maintaining both control precision and detection reliability.
Data Source
AI summary
A robot includes a controllers and a monitoring section, wherein when causing the motor to execute a predetermined operation, the controller transmits a first control signal to the motor as the control signal, receiving a first output signal based on the first control signal as the output signal from an encoder, generates a second control signal in which the difference from the first output signal is smaller than a difference value that between the first control signal and the first output signal, and sending the second control signal to the motor and the monitoring section receiving the second control signal from the controller and comparing the difference between the second control signal and the output signal with the threshold.