Sensorless Elevator Motor Control via Signal Injection
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Solution Overview
Problem
Elevators rely on encoders to control speed and load, but these fail during outages or installation, causing operational interruptions and ride comfort issues, especially in space-constrained environments without machine rooms.
Innovation Solution
A method for controlling an electric motor in elevators using signal injection to determine the rotor's initial angle, forming reference currents in orthogonal dq coordinates to manage load and imbalance, and adjusting current to maintain smooth operation without encoder feedback, employing a processor-controlled system with mechanical braking and load determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an encoder is used to measure speed and control the electric motor, then speed control precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The encoder is completely removed from the system. Instead of using an encoder to measure rotor position and speed, the patent uses sensorless control methods including signal injection to determine initial rotor angle, and observer-based estimation to continuously track rotor position and speed during operation. This extraction eliminates the physical encoder component while maintaining control functionality.
Solution Approach 2:
The mechanical encoder system is replaced with an electrical/software-based sensorless control system. The patent uses signal injection methods and mathematical observers to estimate rotor position and speed electrically, substituting the mechanical sensing approach with an electrical field-based approach that requires no physical sensors on the rotor.
2Measurement precision
If an encoder is installed on the electric motor, then speed measurement accuracy is improved, but ease of installation deteriorates due to space constraints
Solution Approach 1:
The encoder is completely removed from the system. Instead of using an encoder to measure rotor position and speed, the patent uses sensorless control methods including signal injection to determine initial rotor angle, and observer-based estimation to continuously track rotor position and speed during operation. This extraction eliminates the physical encoder component while maintaining control functionality.
Solution Approach 2:
The motor system serves itself by using its own electrical characteristics and back-EMF signals to determine rotor position and speed. The control system extracts position and speed information from the motor's own electrical behavior without requiring external sensors, making the system self-sufficient and eliminating installation complexity.
3Reliability
If an encoder is used for speed control, then operational reliability during outages is improved, but loss of information occurs when encoder operation is interrupted
Solution Approach 1:
The system implements continuous feedback through observer-based estimation that constantly monitors and estimates rotor position and speed based on electrical inputs and model predictions. This feedback mechanism maintains accurate state information without requiring physical encoder feedback, ensuring operational continuity during outages or encoder failures.
Solution Approach 2:
The system prepares for potential encoder failures by implementing redundant estimation algorithms that can determine rotor position and speed through alternative electrical measurements. The observer-based approach provides a backup mechanism that cushions against information loss by maintaining state estimation through mathematical models and electrical signal analysis.
4Ease of operation
If signal injection method is used to determine initial rotor angle, then ease of operation is improved without encoder, but manufacturing precision requirements increase
Solution Approach 1:
The system changes operational parameters by using signal injection at specific frequencies and amplitudes to excite the motor windings and detect rotor position. By carefully controlling the injection signal parameters and analyzing the resulting current responses, the system can accurately determine initial rotor angle without requiring high-precision manufacturing tolerances on the motor itself.
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
Enables smooth and reliable elevator operation without encoders, stabilizing movement and preventing runaway speeds, even during imbalances, while eliminating the need for encoder installation and improving space efficiency.
Implementation Method 1
initial angle of the rotor of the electric motor is determined with the signal injection method
Implementation Method 2
An elevator car is driven in an elevator hoistway with an electric motor
Data Source
AI summary
In one or more example embodiments, an apparatus to control an elevator may include a motor having a rotor configured to rotate with a magnetic axis to drive the elevator at a speed based on a current applied thereto; and a processor configured to regulate the speed of the elevator without information on a speed or an angle of the rotor from an encoder or motion sensor.