Rotary Actuator Capacitive Sensor Distance Control
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Solution Overview
Problem
The varying distance between a rotating operating surface and a fixed capacitive sensor surface on a turntable causes significant sensor errors due to changing electrical properties, which are dependent on the point of actuation and are not constant during rotary motion.
Innovation Solution
A distance-fixing means, such as a non-rotatably mounted sliding disk or spacers, is used to maintain a constant and minimal distance between the sensor and rotor surfaces, with a spring element pressing the sensor surface towards the rotor to minimize friction and ensure consistent capacitance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed sensor surface is placed under a rotatable control surface, then a distance (air gap) must be maintained to minimize friction, but this causes varying distances during rotation leading to sensor errors
Solution Approach 1:
A sliding disk is introduced as an intermediary component between the rotor and sensor surface. This sliding disk serves as a mediator that maintains a constant distance relationship while allowing rotational movement, thereby resolving the contradiction between rotational mobility and measurement precision by decoupling the rotation function from the distance variation problem
Solution Approach 2:
The patent changes the physical parameters of the system by introducing a sliding disk with specific material properties (low friction coefficient, appropriate permittivity). This parameter change allows the system to maintain a constant air gap distance while enabling smooth rotation, thus improving measurement precision without sacrificing rotational mobility
2Measurement precision
If the air gap between rotor and sensor surface is reduced to improve sensing accuracy, then friction increases, but this restricts rotational mobility
Solution Approach 1:
The sliding disk acts as a mediator that enables the system to achieve both goals simultaneously: it maintains a minimal constant air gap for accurate sensing while its low-friction surface allows smooth rotation. The sliding disk transfers the rotational motion without creating excessive friction, resolving the contradiction between measurement precision and ease of operation
Solution Approach 2:
The sliding disk introduces local quality differentiation by having a specific surface design with low friction properties that contacts the rotor, while maintaining a constant distance to the sensor surface. This localized friction reduction at the contact point allows rotation without compromising the overall sensing accuracy
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 arrangement eliminates sensor errors by maintaining a constant air gap and reducing frictional influences, allowing for precise and consistent capacitive sensing across the entire surface, even during rotation.
Implementation Method 1
a spring element presses the sensor surface in the direction of the control surface
Implementation Method 2
the conductor structure forms a capacitor system, which can evaluate the approach of objects to a control surface, which is formed by the surface of the rotor, in a location-resolving manner through changes in capacitance
Implementation Method 3
The material and the surface design of the sliding disk is selected so that the underside of the rotor moves along the sliding disk with as little friction as possible
Data Source
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AI summary
The invention relates to a rotary actuator having a stationary part (stator), on which a capacitive sensor surface is arranged, and a part (rotor) which is rotatably movable relative to the stationary part and has a control surface for the capacitive sensor surface, wherein at least one spacing means is arranged between the control surface and the sensor surface and a spring element presses the sensor surface in the direction of the control surface.