Robot Arm Dual Encoder Redetection for Position Error
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Solution Overview
Problem
Industrial robot arms experience position errors due to twisting and backlash in reduction gears and encoder reading errors, leading to manufacturing line stoppages and decreased efficiency, as existing solutions fail to quickly restore accurate position information without affecting robot operation.
Innovation Solution
A robot apparatus with dual encoders, where a first encoder detects joint position information and a second encoder, with a patterned scale and detector, independently reads position information, and a controller executes encoder redetection processing based on the first encoder's detection results to restore accurate position information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an encoder is disposed on the output side of the reduction gear to detect actual joint angle and reduce position error, then position accuracy of the robot arm is improved, but the system becomes vulnerable to reading errors that cause manufacturing line stoppages
Solution Approach 1:
The patent applies local quality by using two different types of encoders at different locations: an input shaft encoder (incremental type) on the motor side and an output shaft encoder (absolute type) on the reduction gear output side. Each encoder has different characteristics and is suited for its specific location, allowing the system to maintain high measurement precision while improving reliability through redundancy
Solution Approach 2:
The patent implements beforehand cushioning by preparing a backup detection method using the input shaft encoder when the output shaft encoder encounters reading errors. The control unit monitors the output shaft encoder's readings and switches to the input shaft encoder's data when errors are detected, preventing manufacturing line stoppages and ensuring operational continuity
2Measurement precision
If encoder reading errors occur in the output shaft encoder, then position information becomes inaccurate, but stopping the robot to restore accurate position information reduces productivity
Solution Approach 1:
The patent ensures continuity of useful action by enabling the robot arm to continue operating without stopping when encoder reading errors occur. The control unit automatically switches from the output shaft encoder to the input shaft encoder for position detection, maintaining continuous and accurate control of the robot arm while preventing manufacturing line stoppages
Solution Approach 2:
The control unit acts as an intermediary that monitors the output shaft encoder's readings and mediates between the two encoders. When reading errors are detected in the output shaft encoder, the control unit seamlessly transitions to using the input shaft encoder's position information, ensuring continuous accurate control without requiring manual intervention or production stoppage
3Reliability
If dual encoders are used to detect joint position independently, then reliability against reading errors is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the encoder system into two independent detection paths: one using the input shaft encoder for motor position detection and another using the output shaft encoder for actual joint position detection. This segmentation allows the system to maintain high reliability through independent verification while managing complexity by assigning specific functions to each encoder location
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 quick restoration of accurate position information without stopping the robot, reducing manufacturing line downtime and improving efficiency by using the first encoder to drive the joint and redetect position information with the second encoder, even in the presence of encoder reading errors.
Implementation Method 1
a detector configured to relatively move with respect to the scale in a case where the joint operates, the detector being configured to detect position information of the joint by reading the pattern of the scale
Data Source
AI summary
A robot arm includes a joint and links connected via the joint, a first encoder configured to detect information related to a position of the joint, a second encoder configured to detect information related to the position of the joint independently from the first encoder, and a controller configured to control an operation of the joint. The second encoder includes a scale in which a pattern is formed and a detector configured to detect position information of the joint by reading the pattern of the scale. The controller is configured to, in a case where a reading error occurs in the detector of the second encoder, execute encoder redetection processing of driving the joint of the robot arm on a basis of the detection result of the first encoder and redetecting the position information by the second encoder.