BLDC Motor Control Transition Using Weighted IB Angle Blending
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Solution Overview
Problem
Existing BLDC motors face challenges in transitioning between open loop and closed loop control modes, leading to torque shocks, current spikes, and noise due to significant errors in the initial iteration of closed loop algorithms, increasing the risk of motor stalling.
Innovation Solution
A method and device that utilize a weighted average of open loop and closed loop IB angles to facilitate smooth transitions, minimizing torque shocks and noise by running both control modes in parallel and adjusting weighting factors based on motor speed and signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If instantaneous transition from open loop to closed loop control is performed, then control efficiency is improved, but torque shocks and current spikes occur
Solution Approach 1:
The system performs preliminary initialization of the closed loop algorithm using open loop control data (voltage angle, amplitude, current usage, speed) before the actual transition. This preliminary preparation ensures that when closed loop control activates, the initial state is already optimized, reducing the magnitude of correction actions needed in the first iteration and thereby minimizing torque shocks and current spikes.
Solution Approach 2:
The system dynamically adjusts the transition process by monitoring the first iteration error of the closed loop algorithm and modulating the controller's response accordingly. When a significant error is detected, the system adjusts the proportional gain or introduces damping factors to prevent aggressive corrective actions, thereby maintaining smooth operation during the dynamic transition phase.
2Measurement precision
If aggressive proportional gain response is used in closed loop initialization, then control accuracy is improved, but motor stalling risk increases
Solution Approach 1:
The system applies preliminary anti-action by pre-initializing the closed loop controller with accurate open loop data and by detecting potential large errors before they manifest as harmful torque shocks. The system prepares countermeasures in advance, such as adjusting proportional gain or introducing soft-start mechanisms, to prevent the aggressive responses that would otherwise lead to motor stalling while still achieving control accuracy.
3Device complexity
If traditional instantaneous transition method is used, then device complexity is reduced, but audible noise increases
Solution Approach 1:
The system performs preliminary initialization of the closed loop algorithm using open loop control parameters before the actual mode transition. This preparatory step ensures that the controller starts with accurate initial conditions, reducing the magnitude of corrective actions needed and thereby minimizing audible noise during transition without adding significant complexity to the control system.
4Reliability
If open loop control is used at low speeds, then motor stalling risk is reduced, but energy efficiency decreases
Solution Approach 1:
The system dynamically switches between open loop and closed loop control modes based on operating conditions. At low speeds, open loop control is used to minimize stalling risk, while at higher speeds where closed loop control provides better efficiency, the system transitions to closed loop mode. The transition is managed smoothly using the initialization technique to ensure continuous optimal performance across the entire speed range.
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
Enables efficient motor operation across a wide range of speeds by optimizing energy usage and reducing the risk of stalling, ensuring stable control with minimal disturbances during mode transitions.
Implementation Method 1
an observer module configured to obtain a closed loop IB angle between a measured current angle and a closed loop back electromotive force (BEMF) angle wherein the BEMF angle is obtained based on the applied voltage
Data Source
AI summary
This invention provides a method and device for controlling brushless direct current (BLDC) motors, enabling smooth transitions between open loop control at low speeds and closed loop control at higher speeds. The device integrates modules for driving, observing, and transitioning between open and closed loop IB (current and back electromotive force) angles. A weighted average of the IB angles ensures stable motor performance during transitions, minimizing torque shocks, current spikes, and noise. The device also features current and voltage regulation to maintain accurate motor speed under varying conditions. Dynamic adjustment of weighting factors based on motor speed and signal-to-noise ratio further enhances control stability. This system improves motor efficiency in motor driving, reduces the risk of stalling, and optimizes performance across a wide range of operating speeds.