Encoder Eccentricity Correction via Dual-Sensor Averaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Elevator systems face decreased ride quality due to non-linear errors introduced by eccentricity in the rotational motion of motor rotors, which existing methods address by isolating encoders with costly hollow shaft encoders and flexible mountings.
Innovation Solution
A system comprising a motor with an encoder wheel and two sensors positioned 180 degrees apart to detect velocities, averaging these velocities to determine a corrected rotational speed, thereby correcting for encoder eccentricity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hollow shaft encoders with integrated bearings and flexible mountings are used to isolate the encoder from eccentric motion, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the harmful eccentric motion from the encoder measurement system by using a separate correction mechanism. Instead of isolating the encoder physically, the system measures the eccentricity separately and subtracts its effect from the encoder signal, thereby removing the harmful influence without complex mechanical isolation
Solution Approach 2:
The patent introduces an intermediary correction signal that represents the eccentricity effect. This correction signal is generated by measuring the position of the encoder shaft center relative to the rotor center and is used to compensate the encoder output, acting as a mediator between the eccentric motion and the measurement system
2Measurement precision
If hollow shaft encoders with integrated bearings and flexible mountings are used to isolate the encoder from eccentric motion, then measurement precision is improved, but cost increases
Solution Approach 1:
The patent replaces expensive hollow shaft encoders with standard encoders combined with a low-cost correction mechanism. The correction is achieved through software processing and simple position sensing, which are much cheaper than specialized mechanical encoder designs
Solution Approach 2:
The patent replaces the mechanical isolation approach (hollow shaft encoders with flexible mountings) with an electronic/software-based correction approach. The eccentricity is measured and corrected through signal processing, substituting mechanical complexity with electronic control
3Device complexity
If standard encoders are used without correction, then device complexity is reduced, but measurement precision deteriorates due to non-linear errors from rotor eccentricity
Solution Approach 1:
The patent implements a feedback correction mechanism where the actual position of the encoder shaft center is continuously measured and used to generate a correction signal. This correction signal is fed back to compensate the encoder output in real-time, eliminating the non-linear errors caused by eccentricity
Solution Approach 2:
The patent changes the parameters of the encoder signal by applying a correction based on the measured eccentricity position. The correction modifies the angular position and velocity parameters to account for the offset between the encoder shaft center and rotor center, thereby restoring measurement accuracy
Data Source
AI summary
An encoder assembly is disclosed. The encoder assembly comprises a motor having a rotor, and an encoder. The encoder comprises an encoder wheel axially coupled to the rotor, a first sensor configured to detect a first velocity at which a portion of the encoder wheel moves relative to the first sensor, and a second sensor configured to detect a second velocity at which a portion of the encoder wheel moves relative to the second sensor, the first sensor and the second sensor positioned approximately 180 degrees apart from each other about an axis of rotation of the rotor.