Device and method for sensing a rotational position of a rotatable element, control device, sensor system for determining a rotational position of a rotatable element and household appliance
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Solution Overview
Problem
Existing methods for determining the rotational position of a rotatable element in household appliances are either costly, space-intensive, or prone to interference due to the need for a ground surface and wire routing, and often require physical contact or relative change measurements, which can be unreliable, especially after restarts.
Innovation Solution
A capacitive sensor system with a stator and rotor design that eliminates the need for a ground surface, using a rotor with a conductive and dielectric section to cover multiple sensor surfaces, allowing for contactless, absolute, and reliable determination of rotational position through sequential measurements and signal processing, which can be done without physical contact or rotation of the element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a ground surface with wire routing is used for the stator, then the rotational position can be determined using traditional capacitive sensing, but the device becomes more complex, requires more space, and is prone to interference
Solution Approach 1:
The patent extracts and eliminates the ground surface requirement from the traditional capacitive sensing system. By using a rotor with alternating conductive and dielectric sections that modulates the capacitive coupling between stator sensor surfaces and the rotor, the system determines rotational position without requiring a ground surface or wire routing to one, thereby reducing device complexity while maintaining reliability
Solution Approach 2:
The patent replaces the traditional mechanical/electrical ground reference system with a capacitive coupling-based system. Instead of using a grounded surface with wire connections, the system uses the rotor's conductive sections to establish capacitive coupling with the stator sensor surfaces, substituting a purely electrical capacitive mechanism for the mechanical-grounded approach
2Area of stationary object
If a ground surface is provided for the stator, then traditional capacitive sensing can be implemented, but the available sensor area is reduced due to space required for the ground plane
Solution Approach 1:
The patent removes the ground surface requirement from the system, extracting this necessary component from the traditional capacitive sensing architecture. This elimination frees up the space that would have been occupied by the ground plane, allowing for larger sensor surfaces on the stator while maintaining reliable rotational position determination through capacitive coupling alone
3Measurement precision
If incremental evaluation methods are used, then the system can detect rotation changes, but the measurement is not absolute and requires physical contact or rotation to initialize
Solution Approach 1:
The patent implements preliminary action by having the control unit sequentially apply different electrical potentials to multiple stator sensor surfaces and measure the resulting capacitive couplings with the rotor's conductive sections. This initial capacitive measurement pattern provides an absolute reference state that allows the system to determine rotational position absolutely after restart without requiring physical contact or rotation to initialize
Solution Approach 2:
The patent replaces incremental mechanical rotation detection with an absolute capacitive coupling measurement system. By measuring the capacitive coupling between stator sensor surfaces and rotor conductive sections at multiple discrete rotational positions and using these measurements to directly determine absolute rotational position, the system eliminates the need for physical contact or rotation-based initialization required by incremental methods
4Reliability
If wire routing to a ground plane is implemented, then traditional capacitive sensing can function, but interference can occur on the supply line
Solution Approach 1:
The patent extracts and removes the wire routing to ground plane from the system architecture. By eliminating the physical wire connections and ground surface, the system removes the source of supply line interference entirely, achieving reliable signal transmission through wireless capacitive coupling between the rotor and stator
Solution Approach 2:
The patent substitutes the wired electrical connection system with a wireless capacitive coupling system. By using the electric field-based capacitive coupling between the rotor's conductive sections and the stator's sensor surfaces, the system replaces the interference-prone wire routing with a contactless electrical field interaction that is immune to supply line interference
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 approach enables a cost-effective, space-saving, and interference-free method for determining the rotational position, providing accurate and reliable results even after system restarts, with reduced power consumption and faster measurement cycles, allowing for precise detection of multiple detent positions without physical contact.
Implementation Method 1
a stator with a plurality of capacitive sensor surfaces which are separated from one another with respect to an extension plane of the stator
Implementation Method 2
a dielectric non-conductor section, the conductor section preferably being larger in area than the non-conductor section
Data Source
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AI summary
The invention relates to a device (240) for detecting a rotational position of a rotatable element (120). The device (240) has a stator (250) with a plurality of capacitive sensor surfaces that are separate from one another with respect to an extension plane of the stator (250). The device (240) also has a rotor (260) rotatably placeable or arranged relative to the stator (250) and having an electrically conductive conductor section and a dielectric non-conductor section. In this case, the area of the conductor section is preferably larger than that of the non-conductor section. The rotor (260) is arranged so that it can rotate relative to the stator (250) opposite the extension plane of the stator (250). The rotor (260) can be or is coupled to the rotatable element (120).