Robot Cable Asymmetric Ground Shielding
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Solution Overview
Problem
Existing motor drive cables in robot systems face inefficiencies in reducing conductive noise, particularly common-mode switching noise, due to insufficient measures in existing technologies, which affect the performance and reliability of motor control systems.
Innovation Solution
The proposed solution involves a cable configuration with multiple power lines, frame ground lines, and a shield, where a first interposition object is placed between the power lines and the shield, and the centers of the frame ground lines are closer to the shield than the power lines, along with a second interposition object between the power lines and the frame ground lines, utilizing insulators and specific arrangements to minimize conductive noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power lines and frame ground lines are arranged in conventional cable configurations, then cable structure is simple, but conductive noise current increases due to increased parasitic capacitance
Solution Approach 1:
The patent applies asymmetry by positioning the centers of frame ground lines closer to the shield than the centers of power lines. This asymmetric arrangement creates unequal spacing between conductors, which reduces the parasitic capacitance between power lines and frame ground lines, thereby reducing conductive noise current while maintaining a relatively simple cable structure.
Solution Approach 2:
The patent introduces an interposition object (insulator or air gap) between the power lines and the shield. This intermediary element increases the distance between power lines and the shield, reducing parasitic capacitance and conductive noise current. The interposition object acts as a mediator that electrically isolates the power lines from the shield while maintaining structural integrity.
2Volume of moving object
If power lines are positioned closer to the shield, then cable diameter is reduced, but conductive noise current increases due to increased capacitance
Solution Approach 1:
The patent uses asymmetric positioning where frame ground lines are closer to the shield than power lines. This allows the cable to maintain a compact diameter while the asymmetric spacing ensures that power lines remain sufficiently distant from the shield, preventing excessive parasitic capacitance and conductive noise current generation.
Solution Approach 2:
The interposition object is placed between power lines and the shield to maintain an adequate distance. This intermediary ensures that even in compact cable designs, the power lines do not come too close to the shield, thus preventing excessive capacitance formation and conductive noise while still achieving a reduced cable diameter through optimized arrangement.
3Device complexity
If frame ground lines are positioned closer to power lines, then cable structure is compact, but capacitance parasitic increases leading to higher conductive noise
Solution Approach 1:
The patent implements asymmetric positioning where frame ground lines are positioned closer to the shield than power lines are. This creates a compact cable structure while simultaneously ensuring that power lines maintain sufficient distance from frame ground lines, thereby reducing parasitic capacitance and conductive noise current despite the compact overall arrangement.
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 configuration effectively reduces conductive noise currents, enhancing the reliability and efficiency of motor control systems by minimizing capacitance and power loss, and reducing noise interference in robot systems.
Implementation Method 1
A conductive noise current flows via capacitance parasitic between the power line and the FG. The current is specifically a common-mode switching noise current.
Implementation Method 2
A conductive noise current flows via capacitance parasitic between the power line and the FG.
Data Source
AI summary
A robot system includes a plurality of drive parts, a control unit that controls power for driving the drive parts by switching, and a cable that connects the drive parts and the control unit, wherein the cable has a plurality of power lines, a plurality of frame ground lines, and a shield, a first interposition object is provided between the plurality of power lines and the shield, and, in a section of the cable, respective centers of the plurality of frame ground lines are closer to the shield than respective centers of the plurality of power lines.