Encoder Wheel Rotational Speed Control for Electric Machines
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Solution Overview
Problem
Current control systems for electric machines in hybrid and electric vehicles rely heavily on complex sensors for accurate rotational speed detection, which can be costly and prone to inaccuracies, especially in low dynamics conditions.
Innovation Solution
A method utilizing an encoder wheel with multiple teeth and a reference marking, coupled with simpler sensors to detect tooth positions, allowing for the calculation and control of rotational speed during low dynamics phases, where the speed is assumed constant, enabling accurate control without complex sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex sensors (Vogt sensors or resolvers) are used to detect rotational speed, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent uses a simplified encoder wheel with teeth and reference markings that creates a copy or representation of the rotational position information. Instead of using complex sensors to directly measure rotational speed, the system uses a simplified optical encoder structure where the teeth and reference markings on the encoder wheel create easily detectable position signals that can be processed to determine rotational speed with sufficient accuracy for control purposes
Solution Approach 2:
The patent replaces expensive, complex sensors (Vogt sensors or resolvers) with a simpler, more cost-effective encoder wheel and sensor combination. The encoder wheel with teeth and reference markings is a simpler mechanical component that works with basic optical or magnetic sensors, significantly reducing the cost and complexity of the measurement system while maintaining adequate measurement precision for electric machine control
2Measurement precision
If complex sensors are used for rotational speed detection, then measurement precision is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent changes the measurement parameters by using the relative positions of teeth and reference markings on the encoder wheel rather than relying on absolute precision of the encoder wheel manufacturing. By measuring the time or position differences between consecutive teeth and the reference marking, the system can calculate rotational speed while compensating for manufacturing tolerances, thus reducing the stringency of manufacturing precision requirements
3Power
If the electric machine operates with high dynamics, then power output is improved, but measurement precision deteriorates due to tolerance effects
Solution Approach 1:
The patent acknowledges the dynamic operation of the electric machine and designs the measurement system to adapt to varying speed conditions. The encoder wheel with multiple teeth provides sufficient measurement points even during high-speed operation, and the control system can process the position information to accurately determine rotational speed across a wide range of operating conditions, maintaining measurement precision despite the dynamic nature of the application
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 simplifies rotational speed detection and control, improving accuracy and reducing costs by using encoder wheels and sensors to calculate rotational speed, even in low dynamics conditions, ensuring precise torque and power management in electric machines.
Implementation Method 1
at least one sensor, which is disposed next to the encoder wheel and is designed to detect the teeth and the at least one reference marking of the encoder wheel and to emit a sensor signal which characterizes the movement of the teeth
Implementation Method 2
at least one sensor, which is disposed next to the encoder wheel and is designed to detect the teeth and the at least one reference marking of the encoder wheel
Data Source
AI summary
The present invention discloses a method for controlling an electric machine, having an encoder wheel which has a multiplicity of teeth and at least one reference marking, having the steps: detecting the dynamics of the electric machine, detecting the positions of the teeth on the encoder wheel in relation to the at least one reference marking if the electric machine exhibits low dynamics, calculating a rotational speed of the electric machine on the basis of at least the detected positions, and controlling the electric machine on the basis of at least the calculated rotational speed. Furthermore, the present invention discloses a drivetrain and a vehicle.