Electric Motor Torque Constant Determination via Back-EMF
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Solution Overview
Problem
Determining the motor torque constant of a DC motor requires significant measuring effort, often resulting in the use of only mean, maximum, or minimum values for engine control, without precise calibration for each engine.
Innovation Solution
Measuring the generator voltage of the motor and calculating the motor torque constant using specific formulas, eliminating the need for a torque measuring device and allowing for precise torque control without external calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque measuring device and current measuring device are used to determine the motor torque constant, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the essential measurement requirement from the complex torque measurement system. Instead of measuring torque directly with complex devices, it extracts the back EMF voltage signal which contains the torque constant information, and processes this electrical signal to obtain the motor torque constant, thereby eliminating the need for mechanical torque measuring devices.
Solution Approach 2:
The patent replaces the mechanical torque measurement system with an electrical measurement system. By measuring the back EMF voltage and using the relationship between back EMF and motor speed to calculate the torque constant, it substitutes complex mechanical measurement equipment with simple voltage and speed sensors.
2Measurement precision
If a torque measuring device is used to determine the motor torque constant, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The patent enables the motor control system to automatically determine its own torque constant through internal measurements. The system measures the back EMF voltage and rotational speed itself, then calculates the torque constant using the built-in relationship between these parameters, eliminating the need for external calibration equipment and manual calibration procedures.
3Reliability
If statistical measurement on multiple engines is performed, then reliability is improved, but productivity deteriorates
Solution Approach 1:
The patent changes the measurement approach from statistical sampling of multiple engines to direct determination for each individual motor. By measuring the back EMF voltage and speed parameters of each motor and calculating the torque constant individually, it ensures each motor has its own accurate constant without requiring time-consuming statistical measurements on multiple units.
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 torque control and reduces the need for complex equipment, allowing for intelligent motor control and precise torque delivery without the necessity of an external torque test device.
Implementation Method 1
the generator voltage U EMK generated by the motor is measured and that the motor torque constant k M is calculated
Data Source
Figure 1~3
AI summary
The invention relates to a method and a device for determining the motor torque constant KM of an electric motor by measuring motor parameters on the running motor. In order to reduce the previously extensive measurement effort, it is proposed that the generator voltage UEMK generated by the motor is measured first, and that the motor torque constant kM is calculated by dividing the generator voltage UEMK and the rotational speed fMot of the motor, allowing for at least one further constant. The method and the device are suitable for DC motors and for 3-phase synchronous motors.