BLDC Motor Load Estimation Using Phase Zero-Cross Delay
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Solution Overview
Problem
Existing BLDC motor control methods lack accuracy due to unknown load conditions, leading to inefficiencies in torque and speed control.
Innovation Solution
A motor driving device and method that determines load applied to a BLDC motor using a duty ratio of a control signal and phase voltage zero cross point, incorporating sensors and a controller to calculate a zero cross delay value and duty ratio for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If feedback control method is used to control BLDC motor by changing torque or speed, then the motor can be controlled without knowing the load, but the control accuracy deteriorates
Solution Approach 1:
The patent implements feedback control by measuring the zero cross delay value of the phase current with respect to the phase voltage, and using this information to adjust the PWM duty ratio. The controller continuously monitors the load conditions through zero cross point detection and adjusts motor driving parameters accordingly, achieving both ease of operation and improved control accuracy.
Solution Approach 2:
The patent replaces direct mechanical load sensing with an electrical measurement approach by detecting the zero cross point of the phase current and calculating the zero cross delay value. This substitution of mechanical sensing with electrical field-based measurement enables accurate load detection without additional mechanical sensors, maintaining ease of operation while improving control precision.
2Device complexity
If load is not measured, then the control system remains simple, but the control accuracy and ability to predict application completion time deteriorates
Solution Approach 1:
The patent enables the motor control system to self-determine the load by utilizing existing electrical signals (phase voltage and phase current) already present in the system. The controller calculates the zero cross delay value using these inherent signals, allowing the system to self-assess load conditions without external measurement devices, thus maintaining simplicity while achieving accurate load determination.
Solution Approach 2:
The patent introduces the zero cross delay value as an intermediary parameter that bridges the relationship between electrical signals and mechanical load. By measuring the time delay between the zero cross point of phase current and the corresponding phase voltage, the system indirectly determines load conditions, achieving accurate measurement without direct mechanical sensing.
Data Source
AI summary
An embodiment provides a motor driving device including an inverter configured to generate a pulse width modulation (PWM) signal for controlling driving of a brushless direct current (BLDC) motor and supply the driving voltage to the BLDC motor; a sensor configured to sense a phase voltage and a phase current of the BLDC motor; and a controller configured to receive a target speed of the BLDC motor as an input and generate the PWM signal, calculate a zero cross delay value of the phase current with respect to a phase of the phase voltage using the phase of the phase voltage and a zero cross point of the phase current sensed by the sensor, and determine a load amount to be applied to the BLDC motor using the zero cross delay value and a duty ratio of the PWM signal.