Elevator Positioning via Motor Slip and Power Consumption
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Solution Overview
Problem
Existing elevator systems face challenges in providing precise and cost-effective methods for determining the position of the elevator car, particularly in old installations where complex wiring and extensive renovations are required to comply with standards, often necessitating the replacement of control cabinets.
Innovation Solution
A method utilizing an asynchronous motor where the energy consumed and rotor field rotations are measured to calculate the car's position relative to a reference level, reducing the need for permanent elevator shaft installations and minimizing cable requirements by using a single phase wire with a ferrite ring for measurements, and a device with multiplexing/demultiplexing means for communication between the control cabinet and cabin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cabin position sensors are installed at each floor level or notched strips are placed in the elevator shaft, then position determination precision is improved, but device complexity and installation complexity increase significantly
Solution Approach 1:
The patent extracts the position determination function from the traditional shaft-based sensor system and relocates it to the motor control cabinet. By measuring motor parameters (current, voltage, frequency, power) and calculating position based on energy consumption and rotation counts, the system eliminates the need for physical sensors in the shaft and at each floor, thereby reducing installation complexity while maintaining position determination capability
Solution Approach 2:
The patent introduces motor parameters (current, voltage, frequency, power consumption) as intermediary measurements to indirectly determine cabin position. Instead of directly measuring position with sensors, the system uses motor electrical parameters as intermediaries to calculate position through integration and slip compensation, achieving position determination without shaft installations
2Reliability
If notched strips and shaft sensors are installed, then position measurement reliability is improved, but the number of cables and wiring complexity increase
Solution Approach 1:
The patent makes the motor serve multiple functions: it not only drives the elevator cabin but also acts as a position sensor through its electrical parameters. The motor's current, voltage, frequency, and power consumption measurements provide position information, eliminating the need for separate sensing systems and reducing cable requirements to only those needed for motor control
3Adaptability or versatility
If old elevator installations are upgraded with traditional position sensing systems, then compliance with new standards is achieved, but replacement of the control cabinet is required, increasing costs
Solution Approach 1:
The patent enables the existing motor to serve the dual purpose of driving the cabin and providing position information through its electrical parameters. By utilizing the motor's own measurements (current, voltage, frequency, power) for position determination, the system achieves standard compliance without requiring external sensing infrastructure or control cabinet replacement, reducing upgrade costs for old installations
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 precise determination of the elevator car's position without extensive shaft installation, reduces wiring complexity, and allows old elevators to meet new standards by replacing only the cabin button box, facilitating compliance with minimal modifications to the control cabinet and reduced cabling.
Implementation Method 1
the measurements of the energy consumed by the motor and of number of revolutions of the stator rotating field are carried out on a phase wire of the stator by means of a ferrite ring
Data Source
Figure 1~2
AI summary
The method involves measuring power consumption of an asynchronous motor (2), and determining number of turns of a rotating stator field for a particular displacement of a lift car (18). A distance covered by the lift car is calculated from a slip of a rotor of the asynchronous motor, from power consumption measurements of the motor, and from number of turns of the stator field. A position of the lift car is determined with regard to a reference level. The power consumption and the number of turns are determined from a phase wire (3) of the stator. An independent claim is also included for a device for application of a method for determining position of a lift car.