Miniature Motor Sensor Chip for Position Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Miniature electric motors with an outer diameter of 6 mm or less face challenges in determining the rotational rotor position for commutation control, especially at low speeds, due to their small size, which makes it difficult to implement effective position regulation without sensors.
Innovation Solution
A sensor chip with multiple magnetic field sensors, preferably Hall-effect sensors, is arranged axially adjacent to the magnetic rotor to detect the rotational position directly from the rotor's magnetic field, eliminating the need for additional transmitter elements and allowing for precise positioning within the compact motor design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If sensorless control based on back EMF is used in miniature motors with outer diameter ≤6mm, then the motor maintains its compact design, but accurate rotational position detection and low-speed actuation become difficult to achieve
Solution Approach 1:
A sensor chip is introduced as an intermediary component between the rotor and stator. This chip contains multiple magnetic field sensors that detect the rotor's magnetic field through the stator winding, enabling accurate position detection without requiring direct mounting on the rotor or adding significant motor volume.
Solution Approach 2:
The sensor chip is nested within the motor structure by mounting it on the stator, allowing the magnetic field sensors to detect the rotor's magnetic field through the stator winding. This nesting approach enables sensor functionality within the compact motor volume without requiring additional space.
2Measurement precision
If Hall-effect sensors are mounted on the rotor periphery in larger motors, then rotational position can be detected, but the motor diameter must be greater than 6mm to accommodate the sensors
Solution Approach 1:
The sensor chip acts as an intermediary that enables position detection without requiring physical mounting on the rotor periphery. The magnetic field sensors detect the rotor's magnetic field through the stator winding, eliminating the need for additional space on the rotor.
Solution Approach 2:
Instead of mounting sensors radially on the rotor periphery (requiring larger diameter), the solution moves the sensors to the stator in an axial direction, detecting the magnetic field through the stator winding. This dimensional shift allows position detection in compact motors with diameter ≤6mm.
3Measurement precision
If additional transmitter elements are added to enable position detection, then rotational position can be detected accurately, but the device complexity and volume increase
Solution Approach 1:
The rotor's own magnetic field, which is already present for motor operation, is utilized for position detection. No additional transmitter elements are required; the existing magnetic field serves dual purposes: motor operation and position sensing.
Solution Approach 2:
The rotor's magnetic field serves multiple functions: it enables motor operation and simultaneously provides the signal for position detection. The sensor chip detects this multi-functional magnetic field, eliminating the need for separate transmitter elements.
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 enables accurate rotational position detection and regulation, enabling optimal commutation across the entire speed range, including low speeds, and allows for sinus commutation, which was not previously possible with small motors.
Implementation Method 1
The magnetic field sensor is impinged by the magnetic field of the magnetic rotor in such a way that the magnetic field can be evaluated in order to determine the rotational position of the rotor
Implementation Method 2
The sensor chip preferably includes several, and namely at least three, but preferably four individual magnetic field sensors, in particular Hall-effect sensors, integrated in one component
Implementation Method 3
the stator coils can be driven in dependence upon the rotational position of the magnetic rotor in order to generate a magnetic rotating field
Data Source
AI summary
A miniature electric motor (1) with an outer diameter (DA) that is smaller than or equal to 6 mm, has a hollow cylindrical stator (2) with stator coils (8) and a magnetic rotor (4) rotatably arranged around a rotational axis (16) in the stator (2) by means of a rotor shaft (10). The stator coils (8) can be energized in order to generate a magnetic rotational field in dependence upon the rotational position of the magnetic rotor (4). A sensor chip (20) having at least one magnetic field sensor (22) is arranged in such a manner in an area axially adjacent to a front face of the magnetic rotor (4) located within a plane that is vertical to the rotational axis (16) that the magnetic field sensor (22) is impinged in such a way by the magnetic field that the rotational position of the rotor can be evaluated.