Rotary Reciprocating Actuator Angle Sensing Under Motor Noise
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Solution Overview
Problem
The detection accuracy of the angle sensor in rotary reciprocating drive actuators is compromised by shaft shake and electromagnetic noise from the motor, making it difficult to achieve precise scanning.
Innovation Solution
A configuration that includes a movable body with a shaft, a magnet, a core assembly, and a sensor board, where the sensor is positioned to face the wall portion axially and detect the rotational angle, while the magnet is held by a magnet position holding portion to define a reference position, and the core assembly generates a magnetic flux for reciprocating rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the angle sensor is disposed close to the motor to detect rotational angle, then the detection function is integrated, but electromagnetic noise and heat generation from the motor make it difficult to perform suitable measurement
Solution Approach 1:
The actuator is divided into distinct functional zones: the motor assembly (core assembly with coil and magnet) is separated from the angle sensor assembly. The shaft is segmented into different portions, with the first portion connected to the motor and the second portion extending to the angle sensor. This spatial segmentation isolates the angle sensor from electromagnetic noise and heat generated by the motor, enabling accurate rotational angle detection without interference.
2Object-affected harmful factors
If the angle sensor is not disposed in the vicinity of the bearing to avoid electromagnetic noise, then electromagnetic interference is reduced, but it becomes difficult to accurately detect the rotational angle due to shaft shake
Solution Approach 1:
The angle sensor is positioned to detect the rotational angle of the second shaft portion rather than directly at the bearing location. The second shaft portion acts as an intermediary transmission element that conveys rotational information from the motor-driven first shaft portion to the angle sensor. This intermediary approach allows the sensor to be positioned away from electromagnetic noise while still accurately detecting the rotational angle, as the shaft shake at the bearing is decoupled from the sensor measurement point.
3Measurement precision
If the magnet is not held at a defined reference position, then the structure is simpler, but the relative relationship between the angle sensor and other components cannot be determined with high accuracy
Solution Approach 1:
The magnet is pre-positioned at a defined reference position relative to the core assembly before final assembly. The core assembly includes a magnet holding portion that securely positions the magnet in a predetermined location. This preliminary positioning ensures that when the actuator is assembled, the relative relationship between the angle sensor and the magnet (and consequently the mirror) is determined with high accuracy, eliminating the need for complex post-assembly adjustments.
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 allows for accurate detection of the shaft rotation, enabling the movable object to be driven at a high amplitude with improved scanning accuracy.
Implementation Method 1
a coil body that is wound around the core body and that is energized to generate a magnetic flux interacting with the magnet to cause a reciprocating rotation of the movable body
Implementation Method 2
a magnet position holding portion that generates a magnetic attraction force between the magnet position holding portion and the magnet to define a reference position of the reciprocating rotation
Data Source
AI summary
A rotary reciprocating drive actuator includes: a movable body including a shaft part to which a movable object is connected, and a magnet; a base portion including a pair of wall portions disposed to sandwich the movable object and support the shaft part; a core assembly including a core body including a plurality of magnetic poles, a coil body, and a magnet position holding portion to define a reference position of the reciprocating rotation, the core assembly being attached to one wall portion; and a sensor board that is attached to an other wall portion and on which a sensor configured to detect a rotational angle of the one end portion of the shaft part is mounted, in which the sensor board is disposed such that the sensor faces the other wall portion from an outer surface side of the other wall portion and detects the rotational angle.