Motor Position Sensing by Magnetic Field Orientation
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Solution Overview
Problem
Existing position detection systems for motors, such as those used in camera modules of mobile devices, face challenges in providing a broad enough detection area for lenses with longer focal lengths, which are increasingly common in multi-lens camera systems, limiting the range of autofocusing capabilities.
Innovation Solution
A position detection system that includes a magnetic sensor with a bias magnet and a processing circuit, arranged to detect the orientation of the magnetic field superposed by the drive magnetic field, allowing for a broader detection area by using a single magnetic sensor positioned at the center of the coil surface, both parallel and perpendicular to the magnetization direction, and processing signals from half-bridge circuits to determine the position of the drive magnet with respect to the coil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If multiple magnetic sensors are arranged to expand the detection area, then the detection area increases, but the device complexity and potential for phase shifts increase
Solution Approach 1:
The patent transitions from using multiple sensors arranged in space to using a single sensor that detects magnetic field orientation in multiple dimensions (angles). The magnetic sensor detects both the magnitude and orientation of the magnetic field vector, effectively using angular dimensionality to expand detection capability without adding spatial complexity
Solution Approach 2:
The patent changes the detection parameter from simple magnetic field magnitude (scalar) to magnetic field orientation (angular parameter). By detecting the angle of the magnetic field vector relative to a reference direction, the system extracts positional information without requiring multiple sensors, thus resolving the contradiction between detection area and device complexity
2Area of stationary object
If multiple magnetic sensors are used to detect position, then the detection area expands, but measurement precision decreases due to phase shifts and errors
Solution Approach 1:
The patent extracts the essential information needed for position detection from the magnetic field - specifically the orientation angle of the magnetic field vector. By taking only the angular component relative to a reference direction, the system eliminates the need for multiple sensors that would introduce phase shifts, thereby maintaining high measurement precision while expanding detection area
Solution Approach 2:
The patent uses a single magnetic sensor to effectively 'copy' the functionality of multiple sensors by detecting the magnetic field orientation. The angular information obtained from one sensor provides equivalent positional data to what would require multiple sensors arranged in space, eliminating phase shift errors while maintaining detection precision
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 enhances the detection area from ±2 mm to ±2.5 mm, improving the accuracy and range of autofocusing capabilities for lenses with longer focal lengths, while minimizing phase shifts and errors associated with multiple sensor arrangements.
Implementation Method 1
The magnetic sensor delivers at least an output signal representing a magnetoresistance effect produced by the drive magnetic field generated from the drive magnet (302)
Data Source
AI summary
In a motor including a coil and a drive magnet that applies a drive magnetic field to the coil, the drive magnet has a magnetized surface aligned with a magnetization direction and facing a coil surface and a driving direction of the motor is aligned with the magnetization direction. The driving direction is a direction in which one member selected from the coil and the drive magnet is displaced with respect to the other member. The position detection system includes a magnetic sensor and a processing circuit. The magnetic sensor includes a base member, a wiring layer disposed on a base member surface as a surface of the base member, and a bias magnet that applies a bias magnetic field to the wiring layer. The magnetic sensor is arranged such that the base member surface is parallel to the magnetization direction and perpendicular to the magnetized surface.