Servo Motor Position Sensing With Planetary Hall Detection
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Solution Overview
Problem
Existing servo motors in footed robots lack high detection accuracy for motor output positions, limiting robot control precision due to reliance on relative position sensing between stator and rotor without absolute position detection.
Innovation Solution
A servo motor design incorporating a planetary reduction mechanism, Hall magnets, and Hall switches, along with a position sensor, to detect the rotation position of the rotor and improve detection accuracy by determining the rotation angle of the motor, enhancing the robot's movement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If relative position sensing between stator and rotor is used, then the structure is simple, but the detection accuracy of motor output position is low
Solution Approach 1:
The patent introduces a planetary reduction mechanism as an intermediary between the rotor and the position detection system. The planetary carrier, which rotates at a reduced speed (N:1 reduction ratio), carries the first Hall magnet that interacts with the Hall switches. This intermediary mechanism transforms the direct rotor position detection into a two-stage detection process, enabling absolute position detection of the motor output while maintaining reasonable structural complexity through the use of standard planetary gear components.
Solution Approach 2:
The position detection function is segmented into two independent parts: (1) the first Hall magnet and Hall switches on the planetary carrier for detecting the rotation position through reduction mechanism, and (2) the second Hall magnet and position sensor for detecting the rotor rotation angle. This segmentation allows each subsystem to perform its specific detection task independently, improving overall detection accuracy without requiring a completely new complex detection system.
2Measurement precision
If absolute position detection is implemented, then robot control accuracy is improved, but the device complexity increases
Solution Approach 1:
The planetary reduction mechanism serves multiple functions: it provides mechanical speed reduction for the motor output, acts as a position transmission mechanism for the first Hall magnet, and enables absolute position detection through its unique rotational characteristics. By making the reduction mechanism multi-functional, the patent avoids adding separate complex detection mechanisms, thus improving robot control accuracy while limiting the increase in device complexity.
Solution Approach 2:
The system uses the existing rotational motion of the planetary carrier (which naturally occurs during motor operation) to drive the first Hall magnet and generate position signals. The detection system essentially 'self-services' by utilizing the inherent motion characteristics of the reduction mechanism rather than requiring additional actuators or complex sensing arrangements, thereby improving control accuracy with minimal added complexity.
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
The servo motor achieves higher detection accuracy and improved movement control for robots by enabling precise detection of the motor's rotation angle, thereby enhancing the overall movement accuracy of the robot's leg assembly.
Implementation Method 1
a first Hall magnet arranged on the planetary carrier; a plurality of Hall switches corresponding to the first Hall magnet and arranged in the housing at even intervals around a rotation axis of the rotor shaft
Implementation Method 2
a second Hall magnet arranged on the rotor; and a position sensor arranged in the housing and opposite the second Hall magnet
Data Source
Figure 1~2A
Figure 2B~3
Figure 4~5
AI summary
A servo motor includes a housing, a rotor, a stator, a planetary reduction mechanism, a first Hall magnet, Hall switches, a second Hall magnet, and a position sensor; the rotor, stator, the planetary reduction mechanism, and the position senor are arranged in the housing. The rotor has a rotor support and a rotor shaft; the planetary reduction mechanism includes a sun gear, a planetary carrier, and planetary gears; a reduction ratio of the planetary reduction mechanism is N:1, where N is a positive integer; the first Hall magnet is arranged on the planetary carrier; the Hall switches correspond to the first Hall magnet and are arranged in the housing at even intervals around a rotation axis of the rotor shaft. The number of Hall switches is N; the second Hall magnet is arranged on the rotor; and the position sensor is opposite the second Hall magnet.