BLDC Motor Control via PWM Amplitude and Polarity Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless DC motors require effective electronic management to control torque and direction for precise positioning of actuators, especially in applications like turbochargers and throttle valves, where traditional methods lack sensor input for accurate torque modulation.
Innovation Solution
A system that uses an input PWM signal to control a BLDC motor, featuring an amplitude detection module and direction detection module within a processor to determine and modify the torque, allowing the motor to move to a commanded position without sensors, by synthesizing three-phase drive signals and monitoring torque to adjust the driving signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional brush-type motors are used, then torque control and direction control are simpler, but reliability decreases and size/weight increase
Solution Approach 1:
The patent replaces the mechanical brush-commutator system with an electronic control system using PWM signals and microcontroller-based torque management. This substitution eliminates wear-prone mechanical components while achieving equivalent or superior control through electronic means, thereby improving reliability despite increased electronic complexity
Solution Approach 2:
The microcontroller serves multiple functions simultaneously: it generates PWM signals for motor control, monitors torque through current sensing, manages direction control, and implements safety features. This multi-functionality consolidates what would otherwise require separate components, reducing overall system complexity while maintaining high reliability
2Measurement precision
If sensor input is added for accurate torque modulation, then positioning precision improves, but device complexity and cost increase
Solution Approach 1:
The system uses the motor's own current draw as a proxy for torque measurement. By monitoring the phase current through existing current sensors used for PWM control, the microcontroller can calculate torque without requiring additional torque sensors. This self-service approach provides accurate torque feedback while avoiding the complexity and cost of separate measurement systems
Solution Approach 2:
The patent uses current as an intermediary variable to infer torque. Instead of directly measuring torque with complex sensors, the system measures current (which is easier and already part of the control system) and uses the known relationship between current and torque in BLDC motors to derive accurate torque information for precise positioning control
3Power
If PWM signal amplitude is increased for higher torque, then power output improves, but energy loss and heat generation increase
Solution Approach 1:
The system uses periodic PWM switching to control motor power delivery. By rapidly switching the power electronics on and off with variable duty cycles, the microcontroller can deliver high average power when needed while allowing energy recovery during off periods. This periodic action enables high power output without continuous high energy dissipation, reducing overall energy loss and heat generation compared to linear control methods
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
A system for controlling movement of an actuator includes an input power source that provides an input pulse width (PWM) signal; a motor driver that receives the PWM signal and provides a synthesized three-phase drive signal; a brushless direct current (BLDC) motor that receives the drive signal and operates in response to the received drive signal to reposition the actuator; and a controller that receives the PWM signal. The controller includes an amplitude detection module that detects the amplitude of the PWM signal, and a direction detection module that detects the polarity of the PWM signal.