Drive Controller Self-Calibration via Rotor Coasting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Misalignment between the motor shaft and the position transmitter in electric drives results in systematic measurement errors in the rotational position of the rotor shaft, which are exacerbated when determining rotational speed by differentiation, necessitating effective correction variables to ensure accurate position and speed control.
Innovation Solution
A drive controller that determines correction variables by having the rotor shaft coast down and continuously receive raw signals, storing these variables for use in normal operation to correct for measurement errors, without the need for additional components or precise positioning of the transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the position transmitter is attached with high precision to eliminate misalignment, then measurement error is reduced, but manufacturing and installation complexity increases
Solution Approach 1:
The patent applies preliminary action by performing a special operation before normal operation to determine correction variables. During this preliminary phase, the rotor shaft is accelerated to a test rotational speed and then allowed to coast down, during which raw position signals are recorded. These pre-determined correction variables are then stored and applied during normal operation to compensate for misalignment errors, eliminating the need for high-precision mechanical installation.
Solution Approach 2:
The patent changes the operational parameters of the electric machine by operating it at a specific test rotational speed during the special operation phase. This parameter change allows the system to capture position signals under controlled conditions where the rotor dynamics are predictable, enabling accurate determination of correction variables that account for misalignment without requiring precise mechanical positioning.
2Measurement precision
If correction variables are determined through precise mechanical positioning, then measurement accuracy improves, but device complexity and installation time increase
Solution Approach 1:
The system performs self-service by automatically determining its own correction variables through the special operation. The drive controller autonomously controls the rotor shaft acceleration, records raw position signals during coasting down, calculates the correction variables, and stores them for future use. This self-determination process eliminates the need for external precision positioning equipment or complex calibration procedures.
Solution Approach 2:
The patent replaces mechanical positioning systems with a computational approach. Instead of using complex mechanical alignment tools and procedures, the system uses software-based correction variable determination through electrical control of the rotor shaft and signal processing of position transmitter outputs. This substitution of mechanical methods with electrical and computational methods simplifies the overall system.
3Measurement precision
If the rotor shaft is kept at high rotational speed for measurement, then signal quality improves, but energy consumption and mechanical stress increase
Solution Approach 1:
The patent applies periodic action by using a transient high-speed operation followed by coasting down, rather than maintaining continuous high speed. The rotor shaft is accelerated to a test rotational speed, allowed to coast down while recording signals, and then the process can be repeated if needed. This periodic measurement approach achieves high signal quality during the measurement window while minimizing overall energy consumption compared to continuous high-speed operation.
Solution Approach 2:
The system exploits dynamic conditions during coasting down to achieve accurate measurements. By allowing the rotor shaft to naturally decelerate from a high speed, the system captures position signals over a range of rotational speeds during the coasting phase, with the highest quality signals obtained at the beginning when speed is highest. This dynamic measurement approach provides good signal quality without requiring sustained high energy input.
Data Source
AI summary
A drive controller controls an electric drive of an electric machine receiving electric energy via a converter. The drive controller has a normal operating mode and a special operating mode. In the special operating mode, the drive controller determines control signals for the converter and rotates the rotor shaft first at a starting rotational speed. The rotor shaft then coasts without an applied external force, with the drive controller determining from raw signals continuously received from a position sensor raw positions of the rotor shaft, and determining therefrom correction variables for use in the normal operating mode. In the normal operating mode, the drive controller determines from continuously received raw signals in combination with the correction variables determined in the special operating mode an actual position of the rotor shaft and controls the converter with control signals based on the actual position or rotational speed of the electrical machine.