Sensorless BLDC Motor Actuation via Induced Voltage Detection
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Solution Overview
Problem
Brushless direct current motors face challenges in starting from standstill and low-speed operation without sensors, as traditional methods rely on sensors or minimum speed conditions for commutation, leading to inefficiencies and imprecise torque evaluation.
Innovation Solution
An actuating apparatus with a DC voltage converter or inverter that uses high- and low-switch bridge sections to apply supply voltage, allowing sensorless operation by measuring induced voltage differentials across phase connections, enabling precise commutation time determination and rotor position detection at standstill and low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless commutation methods are used in brushless direct current motors, then device complexity is reduced by eliminating sensors, but measurement precision deteriorates at standstill and low speeds making commutation timing inaccurate
Solution Approach 1:
The patent applies preliminary action by performing a startup sequence that first accelerates the motor to a minimum speed where sensorless EMF-based commutation becomes reliable, then transitions to normal sensorless operation. This preliminary speed buildup enables accurate commutation timing without sensors at operating speeds while avoiding the measurement precision problems at standstill.
Solution Approach 2:
The patent changes the operating parameter (rotational speed) from standstill to minimum operational speed during the startup phase. By controlling the motor to reach a speed threshold where induced EMF is sufficient for accurate detection, the system transitions from a state where sensorless measurement is unreliable to one where it is precise, thereby resolving the measurement accuracy contradiction.
2Device complexity
If traditional EMF-based sensorless commutation is used, then device complexity is reduced, but productivity deteriorates due to inability to start from standstill and operate at low speeds
Solution Approach 1:
The patent implements preliminary action through a dedicated startup routine that first brings the motor to minimum operational speed using open-loop or simplified control, then transitions to closed-loop sensorless vector control. This preliminary speed achievement enables subsequent productive operation at low speeds and standstill that would otherwise be impossible with pure sensorless EMF-based methods.
Solution Approach 2:
The patent applies dynamics by implementing speed-dependent control mode transitions. The control system dynamically adapts its operation mode based on rotational speed: using preliminary acceleration modes at standstill, transitioning to sensorless EMF-based commutation above minimum speed, and maintaining adaptive control across the full speed range. This dynamic adaptation enables productive operation across all speed conditions while maintaining sensorless simplicity.
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 and precise motor operation at low speeds and standstill conditions by using voltage differentials to determine commutation times, facilitating fast startup and robust motor control without the need for sensors.
Implementation Method 1
measuring a first induced voltage differential in the passive first phase connection
Data Source
AI summary
A motor actuating apparatus includes three phase connections for three motor phase connections, a high-connection for a supply voltage and a low-connection for a reference potential of the supply voltage, three bridge branches having a series connection of a high-switch and a low-switch and a control device for actuating the switches of the bridge branches. The high-switches are connected to the high-connection and the low-switches are connected to the low-connection. Each of the three phase connections is connected to exactly one of the three bridge branches between the high-switch and the low-switch. The control device is adapted for actuating the switches of the bridge branches such that during a first time period a first phase connection is switched to passive and the second phase connection and third phase connection are alternatingly connected to the high-connection and the low-connection in a predeterminable duty cycle if the supply voltage is applied.