Brushless Motor with Orthogonal Stator Slots for High Acceleration

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Solution Overview

Problem

Brushless motors lack the high acceleration capability required for optical scanning applications, limiting their use in rapid and precise positioning of small optical elements, while galvanometer-based scanners offer high acceleration but are limited to small rotation angles.

Innovation Solution

A brushless motor design featuring a stator with four or eight deep slots, arranged orthogonally to allow bidirectional torque and continuous rotation, with a two-pole diametral-magnetized rotor and non-uniform air gaps to reduce cogging torques, enabling high acceleration and continuous operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Duration of action of stationary object

If brushless motors are used for continuous rotation, then continuous operation capability is improved, but angular acceleration is insufficient for optical scanning applications

Engineering Contradiction:

Improvecontinuous operation capabilityVSAvoidangular acceleration

Core Design Contradiction:

Duration of action of stationary objectVSSpeed

Solution Approach 1:

The stator is segmented into multiple independent phase windings (typically three phases with multiple coils per phase) distributed around the rotor. Each phase can be independently controlled, allowing for optimized torque production across different operating conditions. This segmentation enables the motor to deliver high acceleration during transient periods while maintaining continuous operation capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The motor employs dynamic control of phase winding excitations through electronic commutation. The current magnitude and polarity in each phase are dynamically adjusted based on rotor position and desired torque requirements. This dynamic control allows the motor to provide high acceleration when needed while maintaining steady-state continuous operation.

Inventive Principle:

Principle #15Dynamics

2Speed

If galvanometer-based scanners are used for high acceleration, then angular acceleration is improved, but rotation angle is limited to less than 40 degrees

Engineering Contradiction:

Improveangular accelerationVSAvoidrotation angle range

Core Design Contradiction:

SpeedVSAdaptability or versatility

Solution Approach 1:

The brushless motor design serves multiple functions: it can operate in continuous rotation mode for applications requiring 360-degree rotation, and it can also be controlled to stop at precise positions for positioning applications. The same motor structure and control system accommodate both high-speed continuous operation and high-acceleration positioning, replacing the need for separate galvanometer systems.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The motor control system can dynamically change operating parameters including rotation speed, acceleration, and rotor position. By adjusting the excitation currents and commutation timing, the motor can adapt to different operational requirements within its full rotation capability, effectively changing its behavior from continuous rotation to precision positioning as needed.

Inventive Principle:

Principle #35Parameter changes

3Speed

If high currents are applied to achieve high acceleration, then angular acceleration is improved, but thermal management becomes challenging

Engineering Contradiction:

Improveangular accelerationVSAvoidthermal management

Core Design Contradiction:

SpeedVSTemperature

Solution Approach 1:

The stator windings are divided into multiple phases and multiple coils per phase, distributing the current load across multiple conductors. This segmentation reduces the current density in individual windings while maintaining total torque output, thereby reducing heat generation per unit volume and improving thermal management during high-acceleration operation.

Inventive Principle:

Principle #1Segmentation

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

The design achieves angular acceleration exceeding that of conventional brushless motors and galvanometer-based scanners, with continuous rotation capability and high operational currents, addressing the limitations of both technologies.

Implementation Method 1

a rotor having a two-pole diametral-magnetized magnet bidirectionally operable with the stator

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

a non-uniform separation formed between the magnet and the contoured ends that form a portion of the aperture between each of the slots

Methodology Applied

Scientific EffectMagnetic field interaction: Magnetic Field

Data Source

PatentUS11728698B2Variable torque low inertia brushless motor

Publication Date: 2023.08.15 PANGOLIN LASER SYSTEMS LLC

AI summary

Embodiments of a small brushless motor include a two-pole rotor and a stator having four slots into which electrical coils are placed. Additional embodiments of a small brushless motor include a two-pole rotor and stator having eight slots into which four, six, or eight electrical coils are placed. The stator may include a means for limiting cogging. The small brushless motor having a high torque constant, low coil resistance, low coil inductance, and high thermal conductivity is provided.