Rotary Encoder Angular Velocity Calculation via Lookup Tables
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Solution Overview
Problem
Existing rotary encoders lack accuracy and efficiency in providing speed information, and previous approaches require significant communication overhead to determine angular velocity of a shaft, which is essential for control tasks like torque control on motors and gears.
Innovation Solution
A rotary encoder system comprising a sensor and a controller that measures the angle of a rotating shaft at two times, calculates the angular velocity based on the angular difference and time difference, and transmits this information in an output packet, using a serial communication link, thereby directly determining and normalizing the angular velocity without reducing the angular resolution of the sensor output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If speed information is generated using previous approaches, then speed data can be obtained, but accuracy is insufficient and communication overhead is large
Solution Approach 1:
The controller pre-calculates angular velocity values and stores them in lookup tables during system initialization or calibration. During operation, the controller simply retrieves pre-computed speed values based on current encoder position readings, eliminating the need for complex real-time calculations and reducing communication data requirements while maintaining high accuracy
Solution Approach 2:
Instead of transmitting raw sensor data and computing speed externally, the encoder device creates a copied version of the position information, processes it internally to generate angular velocity values, and transmits only the necessary speed data. This reduces communication overhead by transmitting processed information rather than raw data
2Productivity
If angular velocity is calculated from sensor output, then speed information is obtained, but communication overhead increases
Solution Approach 1:
The controller merges the position measurement function and speed calculation function into a single integrated device. By combining these functions, the encoder computes angular velocity internally using stored position data and transmits only the essential speed information through the serial communication link, improving efficiency while minimizing communication overhead
3Device complexity
If angular resolution is reduced for calculation, then processing is simpler, but measurement precision decreases
Solution Approach 1:
The system performs preliminary organization of position data into lookup tables with full angular resolution during initialization. During runtime, the controller performs simple table lookups rather than complex calculations, maintaining full measurement precision while dramatically reducing computational complexity and processing requirements
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 solution provides accurate and efficient angular velocity measurements with reduced communication overhead, enhancing the precision and reliability of speed information for control systems, while maintaining the full resolution of the sensor output.
Implementation Method 1
In a magnetic rotary encoder (also referred to as a magnetic encoder) a magnet is attached to the shaft such that the magnetic field at a sensor varies as the shaft rotates
Data Source
AI summary
A rotary encoder comprises a sensor configured to measure an angle of a rotating shaft; and a controller configured to: determine a first angle of the rotating shaft at a first time; determine a second angle of the rotating shaft at a second time; calculate an angular velocity based on: 1) an angular difference between the first angle and the second angle; and 2) a time difference between the first time and the second time; and transmit an output packet comprising the angular velocity.