Capacitive Robot Sensing With Guarded Electrical Lines
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Solution Overview
Problem
Collaborative robots equipped with capacitive sensors face interference and erroneous detections due to electric cables, which can trigger safety procedures and disrupt detection accuracy.
Innovation Solution
Applying a guard potential identical to the detection potential to at least part of the electric line within the capacitive detection zone, making the line 'invisible' to the measuring electrodes and preventing interference with capacitive detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electrical lines are positioned in the capacitive detection zone to carry power and control signals, then the robot can operate tools and accessories, but the electrical lines interfere with capacitive sensor operation and cause false detections
Solution Approach 1:
The patent applies equipotentiality by polarizing the electrical line at the same alternating potential and frequency as the capacitive sensor electrode. This creates an equipotential condition between the line and the electrode, eliminating the potential difference that causes capacitive coupling and interference. The line becomes electrically invisible to the sensor, allowing both signal transmission and accurate detection to coexist.
Solution Approach 2:
The patent changes the electrical parameters of the line by applying an alternating polarization at the detection frequency, matching the sensor's operating parameters. This parameter transformation converts the line from a source of interference (when at different potential) to a non-interfering element (when at identical potential), enabling simultaneous operation of power/control signals and capacitive detection.
2Ease of operation
If electrical lines are routed through cable channels along the robot, then power and control can be delivered to tools, but the lines are detected as obstacles and trigger erroneous safety procedures
Solution Approach 1:
By maintaining the electrical line at the same alternating potential as the measuring electrode throughout the detection zone, the line creates no potential difference for the sensor to detect. This equipotential relationship prevents the line from being registered as an obstacle, eliminating false safety triggers while preserving the line's function for power and control signal transmission.
Solution Approach 2:
The electrical line, when polarized at the guard potential, acts as an intermediary that is transparent to the capacitive detection system. The matching potential creates a condition where the line mediates between the sensor and the tools without being detected itself, allowing seamless operation without false safety interventions.
3Measurement precision
If capacitive electrodes are placed on the robot surface for proximity detection, then object approach can be detected, but nearby electrical cables disrupt detection accuracy and range
Solution Approach 1:
The patent eliminates the harmful capacitive coupling effect by making the electrical cable equipotential with the measuring electrode. When both are at the same alternating potential, no capacitive current flows between them, and the cable becomes invisible to the detection system. This restores the full detection accuracy and range as if the cable were not present.
Solution Approach 2:
The patent converts the potentially harmful presence of electrical cables near the sensor into a benign condition by applying the guard potential. The cables, which would normally cause interference, are transformed into non-interfering elements through polarization, turning a harmful factor into an acceptable presence that does not degrade detection performance.
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 effective capacitive detection while allowing the electric line to carry power, control, and communication signals without triggering false safety procedures or disrupting sensor accuracy.
Implementation Method 1
capacitive sensors to detect the approach of objects or human operators in the robot's vicinity. These sensors can, for example, include capacitive electrodes arranged as sensitive surfaces that cover at least part of the robot's surface. These capacitive electrodes are polarized to an alternating excitation potential and connected to sensing electronics that measure the capacitive coupling between these electrodes and objects polarized at a different potential than the electrodes
Implementation Method 2
sensing electronics that measure the capacitive coupling between these electrodes and objects polarized at a different potential than the electrodes
Data Source
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AI summary
The invention concerns an apparatus (200) comprising: - at least one measurement electrode (108) for detecting at least one object in a detection zone (124), by detecting a signal relating to a coupling capacitance between said object (122) and said measurement electrode (108), - at least one capacitive detection electronics (100) connected to the measurement electrodes (108), and - an electrical line (202) comprising at least one electrical wire, in said detection zone (124); the apparatus (200) also comprising a conditioner (204), applying, to at least a portion of the electrical line (202), an alternating electrical potential (VG), called the guard potential, identical to the detection potential at said detection frequency. The apparatus according to the invention may be a robot, in particular a robotic arm, equipped with an electrical line supplying a member of said robot.