Motor Controller Resolver Signal Amplitude Synthesis
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Solution Overview
Problem
Existing motor controllers face challenges in accurately detecting rotational angle, especially at high-speed rotations, due to calculation errors caused by non-negligible time differences between input data, leading to inaccurate motor control.
Innovation Solution
A motor controller system that includes a reference signal generator, A/D converters, amplitude calculators, and a synthesizer to calculate and synthesize cosine and sine signal amplitudes from a resolver, allowing for accurate rotational angle calculation and PWM control, reducing errors from drift and processing period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated resolver/digital conversion IC is used to accurately detect rotational angle, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the digital conversion function from a dedicated IC and implements it within the microcomputer using software-based amplitude calculation. The microcomputer directly processes resolver output signals through A/D conversion and calculates amplitudes using arithmetic operations, eliminating the need for external dedicated conversion ICs and reducing system complexity while maintaining measurement precision.
Solution Approach 2:
The patent replaces the hardware-based dedicated resolver/digital conversion IC with a software-based amplitude calculation system implemented in the microcomputer. By using computational algorithms (arctan function based on calculated amplitudes) instead of dedicated hardware circuits, the system achieves the same functional result with reduced complexity and cost.
2Reliability
If calculation is performed using discretely inputted data to eliminate temperature drift effects, then reliability is improved, but measurement precision deteriorates at high-speed rotation
Solution Approach 1:
The patent performs preliminary A/D conversion of the resolver output signals synchronized with the PWM period before amplitude calculation. By converting the signals to digital form at precise timing intervals and storing them in memory, the system prepares the data in advance for accurate amplitude computation, ensuring both temperature drift immunity and high-speed rotation precision.
Solution Approach 2:
The patent dynamically adjusts the calculation methodology based on rotational speed conditions. At high speeds, it uses synchronized A/D conversion results with precise timing relationships to calculate amplitudes, while at lower speeds it can use discrete data differences. This dynamic adaptation ensures measurement precision across the entire operating range while maintaining reliability.
3Measurement precision
If the carrier wave period and A/D conversion period are made small to reduce calculation errors at high speed, then measurement precision is improved, but use of energy and processing complexity increase
Solution Approach 1:
The patent uses the PWM control period as a universal timing reference for multiple functions: it synchronizes the A/D conversion of resolver signals, coordinates the amplitude calculation process, and controls the motor drive switching. This multi-functional use of the PWM period eliminates the need for separate carrier wave periods and conversion periods, reducing processing overhead and energy consumption while maintaining measurement precision at high speeds.
Data Source
AI summary
A motor controller includes a reference signal generator; an A/D converter performing A/D conversion of the cosine and the sine signals outputted from a resolver; a first amplitude calculator calculating cosine and sine signal amplitudes based on twice-A/D converted cosine and sine signals respectively; a second amplitude calculator calculating averages of the cosine and the sine signals, and that calculates the amplitude of the cosine signal from a difference between the cosine signal average and a latest A/D converted cosine signal, and that calculates the amplitude of the sine signal from a difference between the sine signal average and a latest A/D converted sine signal; a synthesizer synthesizing the cosine and sine signal amplitudes obtained by the first and the second amplitude calculators respectively; a rotational angle calculator calculating a rotational angle based on the synthesized cosine and sine signal amplitudes; and a PWM controller.