Resolver Excitation Control via PWM Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional motor control methods using resolvers face accuracy issues due to amplitude fluctuations in sine and cosine waves caused by heat, signal transmission variations, and power supply fluctuations, leading to decreased motor control precision.
Innovation Solution
A motor control apparatus and method utilizing a PWM output unit to modulate the excitation power supply, allowing for accurate amplitude control of the resolver's output signals, thereby enhancing the accuracy of motor control by adjusting the duty ratio of the PWM output signal based on stored values and using a filter to generate the excitation power supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the resolver outputs analog sine and cosine wave signals, then the motor control system can detect rotation position and speed, but the amplitude fluctuations due to heat, line fluctuation, and power supply variations cause decreased measurement precision
Solution Approach 1:
The patent replaces the conventional analog signal processing system with a digital signal processing system. The resolver output signals are processed through a digital signal processing circuit that performs digital filtering, amplitude detection, and position calculation, eliminating the sensitivity to amplitude fluctuations that plagues analog systems. This substitution of digital for analog processing directly resolves the contradiction by maintaining measurement precision while improving reliability against amplitude variations.
Solution Approach 2:
The patent implements a feedback mechanism where the detected rotation position and speed are continuously compared with target values, and the driving current is adjusted based on the difference. This feedback loop compensates for signal variations and maintains accurate motor control despite amplitude fluctuations in the resolver output signals.
2Manufacturing precision
If the amplitude of sine wave from resolver becomes smaller, then the dynamic range becomes smaller, but the resolving power of A/D conversion circuit relatively becomes smaller causing decreased motor control accuracy
Solution Approach 1:
The patent replaces the A/D conversion approach with a digital signal processing approach that operates directly on the resolver output signals. The digital signal processing circuit performs amplitude detection and position calculation using digital algorithms that are insensitive to the absolute amplitude level, thereby maintaining motor control accuracy even when signal amplitude decreases due to environmental factors.
3Reliability
If conventional DAC and LPF are used to generate excitation power supply, then the resolver can be excited properly, but the system cost and complexity increase
Solution Approach 1:
The patent replaces the conventional DAC and LPF-based excitation power supply generation with a digital signal processing-based approach. The excitation signals are generated and processed digitally, eliminating the need for separate DAC and LPF circuits. This substitution maintains reliable resolver excitation while significantly reducing system complexity and cost.
4Ease of operation
If sampling timing is previously determined at fixed angles, then the control process is simplified, but accuracy decreases when amplitude variations occur
Solution Approach 1:
The patent implements dynamic sampling timing adjustment based on the detected signal amplitude and rotation speed. Instead of fixed sampling angles, the sampling timing is adaptively adjusted to optimize the detection accuracy under varying operating conditions. This dynamic approach maintains control process simplicity while improving measurement precision across different amplitude conditions.
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 provides a high-performance motor control system with improved accuracy and reduced costs by efficiently managing amplitude variations and maintaining precise control over the motor's driving signals.
Implementation Method 1
filtering (integrating) the analog data by LPF (Low Pass filter)
Data Source
AI summary
A motor control apparatus for controlling a motor based on an output from a sensor includes a storage unit storing a value according to an excitation power supply to excite the sensor, a PWM output unit outputting a PWM output signal having a pulse width modulated to have a duty ratio corresponding to a value stored to the storage unit, and a filter input with the PWM output signal from the PWM output unit. The sensor is supplied with the excitation power supply based on an output from the filter.