Brushless Motor Driving Control Apparatus for Vibration Suppression
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Solution Overview
Problem
Existing driving control apparatuses for brushless motors face challenges in suppressing vibration and noise during phase switching, particularly due to torque variation, and struggle with arbitrarily adjusting PWM signal widths, leading to restrictive noise suppression and increased circuit complexity.
Innovation Solution
A driving control apparatus that includes an inverter circuit and a motor control unit, which generates specific PWM signals with adjustable frequencies and on-duties to manage overlap energization, allowing for flexible control of switching elements to minimize torque variation and prevent power supply current drops during phase switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If PWM signals are generated based on a carrier frequency to make current change gentle, then vibration and noise are suppressed, but the pulse width cannot be arbitrarily adjusted and only stepwise adjustment is possible
Solution Approach 1:
The patent makes the PWM signal generation dynamic by allowing arbitrary adjustment of pulse width through a duty ratio calculation unit that computes duty ratios based on current commands and phase currents, rather than being constrained by fixed carrier frequency-based PWM generation. This enables continuous adjustment of pulse width to optimize noise suppression for different operating conditions.
Solution Approach 2:
The patent changes the fundamental parameter of PWM signal generation from fixed carrier frequency to variable duty ratio calculation. By calculating duty ratios based on current commands and actual phase currents, the system can arbitrarily adjust pulse width and frequency, providing flexibility to optimize current change characteristics for different motor operating conditions.
2Object-affected harmful factors
If PWM signals are generated both at the upper arm side and the lower arm side to suppress vibration and noise, then the suppression effect is improved, but the driving circuit operation becomes complicated and circuit size may be increased
Solution Approach 1:
The patent extracts the PWM signal generation function from both upper and lower arms and consolidates it to only the upper arm side. The lower arm switching elements are controlled by simple on/off signals based on commutation timing, while PWM modulation is performed only on the upper arm side. This reduces circuit complexity while maintaining effective noise suppression through selective PWM application.
Solution Approach 2:
The upper arm PWM switching elements are designed to perform multiple functions: they provide both the PWM modulation for noise suppression and the commutation control for phase switching. By making the upper arm switching elements universal, the patent eliminates the need for separate PWM generation circuits in the lower arms, reducing overall circuit complexity.
3Stability of the object's composition
If overlap energization is performed to reduce torque lowering at commutation, then torque variation is reduced, but power supply current may be sharply decreased causing torque variation
Solution Approach 1:
The patent calculates duty ratios using actual phase current feedback during overlap energization. By comparing current commands with actual phase currents and adjusting PWM duty ratios accordingly, the system prevents sharp decreases in power supply current while maintaining torque stability. The feedback mechanism ensures that current transitions are controlled to avoid torque variation.
Solution Approach 2:
The patent performs preliminary PWM modulation on the upper arm switching elements before commutation occurs. By pre-adjusting the duty ratios of upper arm PWM signals during the overlap period, the system prepares smooth current transitions in advance, preventing sharp power supply current decreases and maintaining stable torque throughout the commutation process.
Data Source
AI summary
A driving control apparatus includes an inverter circuit, a motor driving circuit and a motor control unit. In performing overlap energization, at a start time of an overlap time period, a pulse width of a first PWM signal at an energization side is widened to increase a number of pulses of a second PWM signal accordingly, and a first PWM signal at an energization side corresponding to a constant voltage side is also widened.