Brushless DC Motor Drive Unit Sine Wave Energization Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless DC motors with hall elements experience torque drop and increased noise and vibration at low rotation numbers due to deviations in energization timing, which existing drive units fail to adequately address.
Innovation Solution
A drive unit for brushless DC motors that employs intermediate value energization until the rotor position is detected, then transitions to sine wave energization, applying voltage based on the sine value of a predetermined angle θM for one phase and similar phase difference for the rest, to reduce noise, vibration, and torque drop at low rotation numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If rectangular wave energization drive is used at low rotation number, then torque drop is suppressed, but noise and vibration become large
Solution Approach 1:
The patent changes the energization waveform parameter from rectangular wave to sine wave based on rotation speed conditions. At low rotation numbers, sine wave energization is applied to reduce noise and vibration while maintaining adequate torque through intermediate value energization control, rather than using rectangular wave energization which causes excessive noise and vibration.
Solution Approach 2:
The patent dynamically switches the energization method based on rotation speed detection. The control unit transitions from intermediate value energization at low speeds to sine wave energization when rotation reference detection becomes available, adapting the energization strategy to the current operational state to optimize both torque and noise/vibration performance.
2Object-generated harmful factors
If sine wave energization drive is used at low rotation number, then noise and vibration are reduced, but torque drops due to energization timing deviation
Solution Approach 1:
The patent applies preliminary intermediate value energization before the rotation reference detection signal is available. This preliminary energization phase establishes initial rotation and ensures proper energization timing alignment, preventing torque drop that would otherwise occur when transitioning to sine wave energization at very low speeds where timing detection is unreliable.
Solution Approach 2:
The patent uses intermediate value energization as a transitional phase between startup and normal sine wave operation. This intermediary energization mode bridges the gap by providing controlled voltage levels that maintain torque while allowing the system to reach a state where accurate rotation position detection is possible for proper sine wave timing.
3Force
If intermediate value energization is applied, then torque is maintained at low rotation number, but voltage values must be precisely controlled for each phase
Solution Approach 1:
The patent employs feedback control by continuously monitoring the rotation reference detection signal from the hall element. This feedback enables the control unit to determine when the rotor has reached positions where sine wave energization can be properly timed, automatically transitioning from intermediate value energization to sine wave energization without requiring complex manual voltage scheduling.
Solution Approach 2:
The system uses the hall element detection to self-regulate the transition timing. Rather than requiring external control inputs or complex pre-programmed voltage schedules, the system automatically detects when rotation reference signals are available and transitions energization modes accordingly, making the voltage control self-adjusting based on actual rotor position feedback.
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 effectively suppresses noise and vibration while maintaining torque by setting suitable voltage values for each phase, improving output efficiency and reducing torque drop at low rotation numbers compared to rectangular wave energization.
Implementation Method 1
n-phase (n is a natural number of two or more) windings that rotate the rotor
Implementation Method 2
a brushless DC motor including a rotor, n-phase (n is a natural number of two or more) windings that rotate the rotor
Data Source
AI summary
A waveform control unit outputs a signal for driving a brushless DC motor by intermediate value energization to a waveform output unit, and outputs a signal for driving a brushless DC motor by sine wave energization to the waveform output unit when the signal in which the rotation position of the rotation reference is detected is acquired from the element, and the waveform control unit applies voltage corresponding to a sine value of an angle of a winding of one phase of n-phase windings when the brushless DC motor is to be driven by intermediate value energization, and outputs a signal for applying voltage corresponding to a sine value of an angle having similar phase difference as the sine wave energization drive with respect to the angle to the rest of the windings.