Synchronous Motor Digital Feedback Control for Noise Reduction
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Solution Overview
Problem
Existing synchronous motor control systems face challenges with accurate detection of DUTY and torque commands due to switching surges and uneven circuit characteristics, leading to rotational speed fluctuations and acoustic noise issues, especially at low speeds. Additionally, the minimal electrical connections between the motor and external circuits hinder load condition monitoring, resulting in inaccurate current detection and increased costs.
Innovation Solution
A synchronous motor with a three-phase inverter that generates variable AC voltages and frequency, along with digital communication units for receiving and transmitting motor speed, input current, and power commands, enabling precise control and monitoring of the motor's conditions without increasing the number of insulating circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If analog signals are used for DUTY command and torque command, then the circuit configuration is simple, but accurate detection becomes difficult due to switching surge and unevenness in circuit characteristics
Solution Approach 1:
The patent replaces analog signal detection with digital signal processing. Specifically, it uses a microcomputer to digitally process the DUTY command and torque command signals, converting analog inputs into digital values through ADC (analog-to-digital conversion). This digital processing eliminates the effects of switching surges and circuit characteristic variations that plague analog systems, thereby achieving accurate command detection without significantly increasing overall system complexity.
Solution Approach 2:
The patent introduces an intermediary processing stage between the analog command signals and the control system. This intermediary consists of the microcomputer's ADC converter and digital processing unit, which acts as a buffer that isolates the control system from the harmful effects of switching surges and circuit unevenness while accurately capturing the intended command values.
2Ease of manufacture
If minimal electrical connections are used between motor and external circuits, then cost is reduced, but load condition monitoring becomes inaccurate
Solution Approach 1:
The patent makes the existing electrical connections multi-functional. The same communication lines used for basic motor control are also utilized for transmitting load condition information. By implementing digital communication protocols that can carry multiple types of data (control commands, status information, load conditions) over the same physical connections, the system achieves accurate load monitoring without adding extra electrical connections or increasing cost.
Solution Approach 2:
The patent introduces a digital communication intermediary that enables accurate load condition monitoring through existing connections. The microcomputer processes and encodes load condition data into digital signals that can be transmitted through the existing electrical interface, acting as an intermediary that transforms limited physical connections into sufficient information channels.
3Device complexity
If analog rotational speed pulse signal is used, then the system is simple, but rotational speed fluctuates and detection becomes inaccurate
Solution Approach 1:
The patent replaces the analog rotational speed pulse signal with a digital speed measurement system. The microcomputer digitally counts the position sensor signals and calculates rotational speed through digital processing, eliminating the fluctuations and inaccuracies inherent in analog pulse signals. This digital approach maintains relative system simplicity while dramatically improving speed detection accuracy.
4Measurement precision
If digital communication units are added for precise control, then control accuracy is improved, but device complexity increases
Solution Approach 1:
The patent merges the digital communication functions with the existing microcomputer-based control system. Rather than adding separate dedicated digital communication hardware, the invention integrates speed measurement, command processing, and load monitoring functions into the existing microcomputer platform, achieving precise digital control while minimizing increases in overall device complexity through functional consolidation.
Data Source
AI summary
A synchronous motor including therein a three-phase inverter and position sensors, having a unit for calculating a digital input current value from the analog output of an input current detection circuit that detects the input current flowing into the DC input terminal of the three-phase inverter, and a digital feedback speed control unit for adjusting the amplitudes and frequency of the AC voltages outputted from the three-phase inverter in such a manner that the motor speed calculated by a motor speed calculation unit 41 on the basis of the outputs of the position sensors approaches a speed command value received by a communication reception unit from outside the synchronous motor. The synchronous motor further includes therein a communication transmission unit for transmitting the input current value and the motor speed to outside the synchronous motor.