Door Mass Determination via Mechanical Power Measurement
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Solution Overview
Problem
Existing methods for determining the moving mass of an elevator door system are compromised by voltage fluctuations, dead time in output stages, and internal resistance losses, making it difficult to accurately determine mass in a largely automated and independent manner from the running curve.
Innovation Solution
The method involves measuring the electrical power converted into mechanical power, calculating the kinetic energy at maximum speed, and using the relationship m=2Ev2 to determine the door mass, with automatic compensation for friction and closing forces by summing energy over intended opening and closing movements, and utilizing back-EMF to simplify power calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If voltage ramp method is used to determine mass, then automation is improved, but measurement precision deteriorates due to voltage fluctuations, dead time, and electrical losses
Solution Approach 1:
The patent replaces electrical measurement methods with a mechanical approach. Instead of using voltage ramps and electrical power measurements that are susceptible to electrical disturbances, the invention uses mechanical power measurement at the drive shaft. The mechanical power P_mech is measured directly from the mechanical side of the drive system, avoiding all electrical measurement errors such as voltage fluctuations, dead time effects, and line resistance losses. This substitution of measurement domain from electrical to mechanical resolves the contradiction between automation and precision.
2Measurement precision
If friction compensation is applied to minimize fault effects, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent converts the harmful effect of friction into a useful measurement parameter. Instead of trying to compensate for or eliminate friction effects, the invention measures the mechanical power at the drive shaft where friction is already present, and uses this measurement to directly calculate mass. The friction forces that were previously obstacles to accurate measurement become part of the measured mechanical power P_mech, which is then used in the mass calculation formula. This approach eliminates the need for separate friction compensation mechanisms while maintaining measurement accuracy.
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 approach allows for accurate and automated determination of the door mass, robust against noise and fluctuations, providing reliable results with good repeatability and the added benefit of automatically calculating friction, which is essential for safety and control optimization.
Implementation Method 1
measurement of a motor's electrical power Pel which is converted into mechanical power
Implementation Method 2
utilizing back-EMF to simplify power calculation
Data Source
AI summary
A method for determining moving mass of a door system, actuated by a motor, wherein a) the motor electrical output, which is converted into mechanical output, is measured, b) the electrical output is summed during opening and/or closure, starting from the beginning of the actuation of the mass by the motor from initial rest until an end rest position is reached following completion of the actuation to determine energy losses, c) measurement of the maximum speed of the mass of the door system is measured during opening and/or closure, d) the electrical output provided by the motor from the initial rest position of the mass of the door system until achieving the maximum speed v thereof is summed, and the obtained energy value is reduced by the energy losses occurring up to this time point to determine the mass of the door system from the obtained kinetic energy.