Torque Estimation for Railway Vehicle Braking Control
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Solution Overview
Problem
Existing systems for estimating braking torque in railway vehicles are not economically secure and lack operational reliability, relying on lookup tables and complex calculations.
Innovation Solution
A method using a second controller to measure phase currents and rotor position, transforming them into rotating coordinates, filtering, and calculating torque using the equation Cem = 3np((Ld - Lq)Id Iq + Φ0 Iq, with low-pass filtering to reduce noise, and comparing estimated torque to a reference torque for accurate braking control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lookup tables are used to estimate braking torque, then the system is simple to implement, but the operational reliability and accuracy are insufficient
Solution Approach 1:
The patent replaces traditional mechanical lookup table methods with an electrical/mathematical calculation system. The torque estimation is achieved through real-time calculation using measured currents, voltages, and angular positions fed into a torque estimation equation, substituting static mechanical tables with dynamic computational methods that provide both accuracy and reliability.
Solution Approach 2:
The system uses the electric machine's own operational parameters (phase currents, voltages, angular positions) to estimate torque without requiring external sensors or additional measurement devices. The control device leverages existing measurements already taken for control purposes, making the system self-sufficient and eliminating the need for separate torque sensing hardware.
2Measurement precision
If complex calculations are used to estimate torque, then the accuracy improves, but the economic efficiency deteriorates
Solution Approach 1:
The system achieves accurate torque estimation by utilizing measurements already performed for control purposes (phase currents, voltages, angular positions). This self-service approach eliminates the need for additional expensive torque sensors while maintaining high measurement precision through mathematical calculation rather than physical measurement hardware.
Solution Approach 2:
The patent substitutes expensive mechanical torque sensing systems with computational torque estimation using readily available electrical measurements. This replacement reduces manufacturing costs while maintaining or improving torque measurement accuracy through real-time calculation based on machine parameters.
3Reliability
If a redundant torque estimation system is implemented, then the operational security improves, but the device complexity increases
Solution Approach 1:
The patent merges the torque estimation function with the existing control device, combining multiple functions (control, measurement, and torque estimation) into a single integrated system. This consolidation provides redundant torque estimation capability without proportionally increasing system complexity, as the same hardware resources are utilized for multiple purposes.
Solution Approach 2:
The control device is designed to perform multiple functions: primary control operations, torque estimation for safety monitoring, and activation of friction brakes when necessary. This multi-functionality allows a single device to provide operational security through redundant estimation without requiring separate dedicated hardware for each function.
Data Source
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AI summary
The present invention relates to a method for controlling an electric vehicle (1), in particular a railway vehicle, having a three phase electric machine (7) for accelerating and/or decelerating the vehicle, the three phase electric machine includes a stator and a rotor, the method comprising the following steps: determining a current (I1) of a first phase of the three phase electric machine, determining a current (I2) of a second phase of the three phase electric machine, determining the angular position (p) of the rotor, and determining an estimated torque of the three phase electric machine based on the current of the first phase, the current of the second phase and the angular position of the rotor, controlling the electric vehicle based on the estimated torque..