Robot Motor Control for Emergency Stop Position Maintenance
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Solution Overview
Problem
Existing brake systems in machines like industrial robots and machine tools fail to maintain the position and posture of components during emergency stops when the braking force is compromised, potentially leading to unintended movement due to gravity, especially when the brake fails or is impaired by substances like grease or oil.
Innovation Solution
A control device with a state detector, such as a rotational position detector, monitors the movement of members on a drive axis and controls the motor and brake to maintain the stopped position by interrupting power supply during emergency stops and restarting it if movement is detected, ensuring the component remains in a safe position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the brake is operated and power supply to the motor is interrupted during emergency stop control, then the stopped position of the member is maintained, but if the brake is in failure, the position and posture of the robot cannot be maintained and the member moves due to gravity
Solution Approach 1:
The control device continuously monitors the rotational position of the motor during emergency stop control using a rotational position detector. If movement is detected despite the brake being applied and power being interrupted, the control device activates the motor to counteract gravitational force and maintain the safe position. This feedback mechanism ensures position maintenance reliability even when the brake fails.
2Measurement precision
If the rotational position detector is used to monitor the position of the member during emergency stop control, then the position can be accurately detected, but the device complexity increases
Solution Approach 1:
The rotational position detector serves multiple functions: it detects the rotational position during normal operation for motion control, and it continues to detect position during emergency stop control to monitor for unintended movement. By reusing the same detector for both normal and emergency operations, the system achieves accurate position detection without significantly increasing device complexity.
Data Source
AI summary
A robot includes a motor that includes a brake and moves an arm on a drive axis, and a rotational position detector that detects movement of the arm. When a state occurs in which the robot is preferably emergency-stopped, a control device performs an emergency stop control in which the brake is operated and power supply to the motor is interrupted. When the movement of the arm is detected based on an output of the rotational position detector during the emergency stop control, the control device supplies power to the motor to prevent the movement of the arm.