Electronically Commutated Motor Control Using Delta-Sigma Bit Streams
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Solution Overview
Problem
Existing control devices for electronically commutated electric motors face challenges in generating high-resolution, high signal-to-noise ratio control signals for precise rotor position control, leading to inefficiencies in torque generation and electromagnetic compatibility.
Innovation Solution
The integration of a delta-sigma converter generates a digital bit stream from the rotor position signal, producing a pulsed control signal with increased frequency bandwidth and noise distribution, which is processed by semiconductor switches to enhance the control signal's accuracy and compatibility, using noise generators and voltage feedback mechanisms to compensate for supply voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional control device generates load current without noise superposition, then the control signal has sufficient stability, but the frequency bandwidth is insufficient for effective rotor movement
Solution Approach 1:
The patent applies noise dithering technique where controlled random noise is superimposed on the load current control signal. This converts the harmful effect of noise into a beneficial effect by spreading concentrated spectral energy across a wider frequency range, thereby increasing frequency bandwidth while maintaining electromagnetic compatibility through spectral distribution.
Solution Approach 2:
The patent changes the spectral parameters of the control signal by superimposing noise with specific characteristics (amplitude, frequency distribution). This parameter modification transforms a narrowband signal into a wideband signal, enabling effective rotor movement across broader frequency ranges while managing electromagnetic interference through controlled spectral spreading.
2Reliability
If the control signal frequency bandwidth is increased to improve rotor control, then the electromagnetic compatibility improves, but the device complexity increases due to additional components
Solution Approach 1:
The patent merges the noise generation function with the existing control signal generation pathway. The noise dithering is integrated into the digital control architecture, combining the random noise source with the deterministic control algorithm in a unified signal generation process, thereby achieving bandwidth expansion without proportionally increasing device complexity.
Solution Approach 2:
The patent introduces a noise dithering mechanism as an intermediary element between the control algorithm and the power electronics. This intermediary superimposes controlled noise on the control signal, mediating between the digital control domain and the analog power conversion domain, thereby improving electromagnetic compatibility while maintaining architectural simplicity.
3Measurement precision
If voltage feedback is implemented to compensate for supply voltage fluctuations, then the control precision improves, but the device complexity increases due to additional feedback components
Solution Approach 1:
The patent implements voltage feedback by sensing the supply voltage and using it to modulate the noise dithering signal or the control signal amplitude. This feedback mechanism compensates for supply voltage fluctuations, maintaining control precision across varying operating conditions while integrating seamlessly with the existing control architecture.
Solution Approach 2:
The voltage feedback mechanism serves multiple functions: it compensates for supply voltage variations, maintains optimal noise dithering levels, and ensures consistent control precision across different operating conditions. This multi-functionality reduces the need for separate compensation circuits, thereby limiting the increase in device complexity.
Data Source
AI summary
The invention relates to a control device for controlling an electronically commutated motor. The control device comprises a control input for a rotor position signal and a control output for connection to field coils of the motor. The control device is designed to generate a load current for displacing a rotor of the motor depending on the rotor position signal and to output said load current via the control output. The control device comprises at least one semiconductor switch for switching the load current depending on a semiconductor control signal. The control device comprises at least one pulse generator including the at least one semiconductor switch, said pulse generator being designed to generate the load current in the form of a pulsed control signal for displacing the rotor. The control device is characterized by a delta sigma converter which is at least indirectly connected to the control input on the input side and which is designed to produce the semiconductor control signal in the form of a digital bit stream depending on the rotor position signal.