Motor Control Apparatus Adaptive Current Sampling
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Solution Overview
Problem
Existing motor control apparatuses for three-phase AC motors face issues with switching noise and distorted current command waveforms, which affect motor control accuracy, especially when correcting current command values and changing duty ratios.
Innovation Solution
A motor control apparatus that includes an inverter with switching elements, current detection, and conversion means to acquire phase current values at specific timings based on current command value amplitudes and electrical angles, converting them into digital AD values to prevent switching noise and ensure accurate motor control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If current command value correction is applied to prevent switching noise, then switching noise is reduced, but current command waveform distortion occurs affecting motor control accuracy
Solution Approach 1:
The patent applies preliminary action by detecting the electrical angle in advance and pre-determining the optimal AD conversion timing based on the electrical angle range before current command value correction is applied. This allows the system to select conversion timings that avoid waveform distortion while preventing switching noise, rather than applying correction after distortion has occurred.
Solution Approach 2:
The patent changes the parameter of AD conversion timing based on the electrical angle. By dynamically adjusting the conversion timing according to the electrical angle range (e.g., converting at t=τ/2 for certain angle ranges, or at t=τ/8 and t=7τ/8 for others), the system adapts to different operating conditions to prevent both switching noise and waveform distortion.
2Adaptability or versatility
If duty ratio is changed to control motor, then motor control flexibility is improved, but switching noise occurs affecting motor control
Solution Approach 1:
The patent applies preliminary action by determining the optimal AD conversion timing in advance based on the electrical angle before duty ratio changes are executed. This pre-determination ensures that current sampling occurs at timings that avoid switching noise regardless of subsequent duty ratio adjustments, maintaining control flexibility without noise interference.
Solution Approach 2:
The patent changes the AD conversion timing parameter dynamically based on electrical angle conditions. By selecting different conversion timings (t=τ/2, t=τ/8, t=7τ/8) according to the electrical angle range, the system maintains flexibility in duty ratio control while preventing switching noise through adaptive timing selection.
3Device complexity
If phase current value is acquired at fixed timing, then system complexity is reduced, but switching noise affects current detection accuracy
Solution Approach 1:
The patent applies dynamics by making the AD conversion timing variable rather than fixed. The conversion timing is dynamically adjusted based on the electrical angle range, allowing the system to select optimal timings that avoid switching noise while maintaining relatively simple control logic through angle-based decision rules.
Data Source
AI summary
A motor control apparatus includes an inverter comprising switching elements, current detection means for detecting a phase current value, conversion means for converting the phase current value into a digital AD conversion value, and current control means for controlling a three-phase AC motor by switching the switching elements using a current command value based on the AD conversion value. When the conversion means determines that an amplitude of the current command value is greater than or equal to a threshold, it acquires the phase current value at timings of at least one of t=τ/8, 3τ/8 and t=5τ/8, 7τ/8 converts the acquired phase current value into the AD conversion value. When the conversion means determines that the amplitude of the current command value is smaller than the threshold, it acquires the phase current value at a timing of t=τ/2, converts the acquired phase current value into the AD conversion value.