Robot Arm Vibration Suppression via Local Angular Velocity Feedback
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Solution Overview
Problem
Existing robots face challenges in efficiently suppressing vibrations due to low rigidity in joint portions, leading to increased calculations and reduced response speed, particularly when using acceleration sensors at the tip of arm link portions, which results in impaired control performance and potential vibration increase at singular points.
Innovation Solution
A robot design that reduces the number of sensors by installing inertia sensors at strategic points along the arms, allowing feedback control using angular velocities detected by these sensors to suppress vibrations effectively, thereby simplifying calculations and avoiding singular points, and enhancing vibration suppression by controlling drive sources based on detection results from sensors installed at regions with maximum vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If acceleration sensors are installed at the tip portion of the arm link to detect vibration, then vibration suppression capability is improved, but the calculation amount increases hugely due to Jacobi's transformation and matrix calculations
Solution Approach 1:
The patent extracts only the necessary vibration information directly from the arm link where vibration occurs, rather than using acceleration sensors at the tip that require complex coordinate transformations. By placing vibration detectors directly on the arm link and using simple angular velocity differentiation, the system obtains vibration data without needing Jacobi's transformation or large-scale matrix calculations.
Solution Approach 2:
Instead of the conventional approach of using tip acceleration sensors and transforming coordinates to calculate joint vibrations, the patent inverts the approach by directly measuring angular velocity at the arm link joint and differentiating it to obtain vibration information. This reverse methodology eliminates the need for complex coordinate transformations while achieving the same vibration detection goal.
2Measurement precision
If complex matrix calculations are performed continuously to convert acceleration data, then accurate vibration feedback is achieved, but response speed becomes slow
Solution Approach 1:
The patent replaces the complex computational system (matrix calculations and coordinate transformations) with a simpler mechanical/mathematical approach. By directly measuring angular velocity at the joint and using simple differentiation, the system achieves accurate vibration feedback without the computational burden of continuous matrix operations, thereby improving response speed.
3Reliability
If coordinate axis transformation is calculated based on motor rotation angles, then accurate vibration compensation is achieved, but singular points cause vibration increase or control failure
Solution Approach 1:
The patent extracts vibration information directly from the arm link joint using local angular velocity measurement, bypassing the coordinate transformation process entirely. This eliminates the singular point problem that occurs in Jacobi's transformation when the robot configuration approaches certain angles, as the measurement is performed in the local coordinate system where singularities do not exist.
4Reliability
If multiple sensors are installed at various arm portions to achieve comprehensive vibration suppression, then control performance is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies local quality by placing the vibration detector directly at the specific location (arm link joint) where vibration generation is most critical. Rather than distributing multiple sensors throughout the arm structure, the invention concentrates sensing capability at the most effective location, achieving comprehensive vibration suppression with minimal sensor deployment.
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
The proposed solution enables reliable and efficient vibration suppression in robots with reduced sensor usage, improving response speed and reducing costs and circuit complexity, while maintaining effective control performance even at regions with high vibration.
Implementation Method 1
a first inertia sensor that is installed at the first arm and detects the angular velocity or acceleration of the first arm around the first rotation axis
Data Source
AI summary
A robot includes a base, a first arm that rotates around a first rotation axis, a second arm that rotates around a second rotation axis extending in a direction different than the first rotation axis, a third arm that rotates around a third rotation axis extending in a direction parallel to the second rotation axis, a first inertia sensor at the first arm, a second (a) inertia sensor at the third arm, a first angle sensor at a first drive source, a third angle sensor at a third drive source, and the drive sources rotate the respective arms. Angular velocities from the first inertia sensor and the first angle sensor are fed back to a first drive source control unit. Angular velocities from the second (a) inertia sensor and the third angle sensor are fed back to a second drive source control unit.