Robot Joint Command Correction Using Acceleration Feedback
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Solution Overview
Problem
Robot manipulators experience kinematic errors due to inaccuracies in motor and gear manufacturing, leading to deviations in joint position and speed, which affect the accuracy of end effector control.
Innovation Solution
A method is introduced that includes using an acceleration sensor in the distal portion of the manipulator to measure acceleration along a selected trajectory, estimating expected acceleration values, and applying kinematic error corrections to position commands to reduce deviations from expected acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If standard manufacturing processes are used for robot manipulators, then manufacturing cost and ease of manufacture are improved, but manufacturing precision and reliability deteriorate due to kinematic errors from motor and gear inaccuracies
Solution Approach 1:
The patent applies preliminary action by pre-determining kinematic error correction values for each joint through systematic measurement and calculation before actual robot operation. The correction values are stored in memory and automatically applied during robot control, eliminating the need for expensive precision manufacturing while ensuring accurate end effector positioning.
2Manufacturing precision
If high precision manufacturing is used for motors and gears, then manufacturing precision and reliability are improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent replaces the mechanical solution of high-precision manufacturing with an informational/control-based solution. Instead of improving physical manufacturing precision through better machining processes, the system uses measurement devices to detect kinematic errors and applies computational corrections through the controller, substituting mechanical precision requirements with information processing.
3Manufacturing precision
If individual customization is applied to each robot specimen, then manufacturing precision and reliability are improved, but productivity and ease of manufacture deteriorate
Solution Approach 1:
The patent applies parameter changes by determining specific kinematic error correction parameters for each joint of each robot specimen through standardized measurement procedures. These individualized parameter sets are stored in the controller's memory and automatically applied during operation, enabling mass production of robots with customized correction parameters through a systematic process rather than individual hand-tuning.
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
This method effectively reduces kinematic errors in robot joints by compensating for individual inaccuracies, allowing for accurate control of the end effector and enabling cost-efficient manufacturing and maintenance of robotic systems.
Implementation Method 1
providing an acceleration sensor in the distal portion, selecting a trajectory to be followed by the acceleration sensor, estimating expected acceleration values to which the sensor is expected to be subject along said trajectory
Data Source
AI summary
A method for reducing kinematic error in a joint includes providing an acceleration sensor; selecting a trajectory to be followed by the acceleration sensor; estimating expected acceleration values the sensor will experience along the trajectory; outputting initial commands for moving the sensor along the trajectory; obtaining corrected commands by adding to a parameter specified in an initial command a kinematic error correction and inputting the corrected commands into a joint controller; recording acceleration values to which the sensor is subject while moving according to the corrected commands; judging whether a deviation between the expected acceleration values and the recorded acceleration values exceeds a predetermined threshold, and when the deviation is judged to exceed the threshold, modifying the kinematic error correction so as to reduce the deviation.