Servo Zero-Return Control Using Single-Turn Encoders
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Solution Overview
Problem
Conventional methods fail to achieve precise zero-return of a servo rotor in robots due to the lack of a brake device, leading to positional errors when the arm swings beyond 360 degrees, and using multi-turn encoders is costly.
Innovation Solution
A system comprising a motor, speed reducer, single-turn encoders, and a motor controller that issues activation commands, compares default and current positions, and drives the servo to return to zero-point using PWM commands, ensuring precise zero-return without the need for a brake device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single-turn encoder is used to measure motor position, then the cost is low, but precise zero-return cannot be achieved when the arm swings beyond 360 degrees
Solution Approach 1:
The patent divides the position measurement function into two segments: the motor shaft position is measured by a single-turn encoder, while the steering wheel position is measured by a separate sensor. This segmentation allows each component to operate within its optimal range, with the single-turn encoder handling motor rotations and the separate sensor tracking the steering wheel's absolute position, thereby achieving precise zero-return without requiring an expensive multi-turn encoder.
Solution Approach 2:
The patent introduces a steering wheel as an intermediary component between the motor and the final output. The steering wheel's position is independently detected by a separate sensor, and this position information is used to determine the servo's zero-point. This intermediary approach allows the system to track absolute position changes even when the motor shaft rotates multiple times, resolving the contradiction between using a simple single-turn encoder and achieving precise zero-return.
2Device complexity
If no brake device is provided in the steering system, then the device complexity is reduced, but the arms swing out of the original position due to gravity
Solution Approach 1:
The patent implements a self-service mechanism where the system automatically detects and corrects position drift caused by gravity. The controller continuously monitors the steering wheel position using the separate sensor and automatically adjusts the motor position to maintain the correct zero-point alignment. This self-correcting mechanism eliminates the need for a brake device while maintaining position stability through active control.
Solution Approach 2:
The patent establishes a feedback loop where the steering wheel position sensor continuously provides position information to the controller, which then adjusts the motor output to maintain accurate zero-return. This feedback mechanism compensates for gravity-induced position changes without requiring passive mechanical restraint devices like brakes, thereby reducing device complexity while maintaining stability.
Data Source
AI summary
The present disclosure relates to a method for controlling zero-return of a servo of a robot, and a servo and a robot with enhanced zero-return. The method includes: outputting an activation command to a motor, and reading a default zero-point of the motor (w1) and a default zero-point of an output shaft of the speed reducer (w2). The output shaft of the motor (w1) is driven to return until the default zero-point of the output shaft of the speed reducer (w2) is the same with the current position of the output shaft of the speed reducer (w4) in response to the default zero-point of an output shaft of the speed reducer (w2) being not the same with the current position of the output shaft of the speed reducer (w4).