Robot Balancer Fault Detection Using Standby Motor Current
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Solution Overview
Problem
Conventional collision detection systems in articulated robots struggle to detect balancer abnormalities, such as spring breakage, due to the torque fluctuations being masked by larger margins set to prevent erroneous detection during high acceleration or load variations, making it difficult to differentiate between normal and abnormal conditions.
Innovation Solution
A balancer abnormality detection system that measures the current value of the motor during robot standby and compares it with a specific command value to detect abnormalities, using a separate threshold for balancer detection that is distinct from collision detection thresholds, allowing for early detection of balancer issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed threshold with large margin is used for collision detection to prevent erroneous detection during high acceleration or load variations, then false detection is reduced, but the ability to detect balancer abnormalities is lost
Solution Approach 1:
The patent divides the detection function into two separate thresholds: a first threshold for collision detection during robot operation, and a second threshold for balancer abnormality detection during standby. This segmentation allows each threshold to be optimized for its specific purpose without compromising the other
Solution Approach 2:
The patent applies different threshold values for different operational states: a larger threshold margin during operation to prevent false collision detection, and a smaller threshold margin during standby to enable sensitive balancer abnormality detection. This local quality adjustment resolves the contradiction by tailoring the detection sensitivity to the specific operational context
2Productivity
If the robot operates with great acceleration or in a state greatly off preset load, then productivity is improved, but collision detection becomes unreliable due to torque fluctuations exceeding the threshold
Solution Approach 1:
The patent dynamically adjusts the detection threshold based on the robot's operational state. During operation, a larger threshold margin accommodates torque fluctuations from high acceleration and load variations. During standby, a smaller threshold margin enables sensitive detection of balancer abnormalities. This dynamic adjustment maintains both productivity and detection reliability
3Object-generated harmful factors
If the threshold margin is increased to accommodate torque fluctuations during operation, then false collision detection is prevented, but the torque fluctuation from balancer abnormality can no longer be detected
Solution Approach 1:
The patent segments the detection function into two distinct modes with different thresholds: operation mode with a higher threshold to filter out normal torque fluctuations, and standby mode with a lower threshold to detect balancer abnormalities. This segmentation resolves the contradiction by applying appropriate sensitivity levels to each operational context
Solution Approach 2:
The patent changes the detection threshold parameter based on the robot's operational state. During operation, the threshold is set higher to tolerate torque fluctuations from acceleration and load changes. During standby, the threshold is lowered to detect the smaller torque changes caused by balancer abnormalities. This parameter change enables both false detection prevention and abnormality detection
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
Enables reliable and early detection of balancer abnormalities by distinguishing between normal and abnormal conditions through a dedicated threshold for balancer detection, improving the system's ability to identify issues like spring breakage.
Implementation Method 1
The balancer generates the force for assisting the power of the servomotor by the force generated by an elastic body
Implementation Method 2
a gas spring which generates elastic force (repulsive force) by compression of a gas
Implementation Method 3
a servomotor that drives an axis on which the load by the gravity acts
Data Source
AI summary
A balancer abnormality detection system includes: a robot; a motor configured to operate the robot; a balancer provided in the robot and configured to generate assist torque which assists power of the motor with force generated by elastic bodies; and a controller configured to detect abnormality of the balancer by measuring a current value of the motor operated to keep a posture of the robot during standby of the robot and comparing the current value with a current command value of the motor necessary for keeping the posture of the robot.