Digital Variable Reluctance Motor Control for Power Tools

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Solution Overview

Problem

Power tools lack efficient control mechanisms to adapt to varying load conditions during operation, leading to inefficiencies and potential hazards such as splintering, bogging down, or equipment damage.

Innovation Solution

A digital variable reluctance (DVR) controller that senses changes in motor reluctance and current to automatically adjust speed and torque, eliminating the need for mechanical transmissions and enabling precise control of power tool operations based on load conditions, including automatic shutdown, speed changes, and reverse operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If manual or basic automatic control is used in power tools, then the device complexity is reduced, but the adaptability to varying load conditions deteriorates

Engineering Contradiction:

Improveadaptability to load conditionsVSAvoidcontrol mechanism complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The control system continuously monitors motor current and reluctance variations during operation, using this feedback to dynamically adjust motor parameters. This enables automatic adaptation to changing load conditions without requiring complex mechanical transmissions or multiple speed settings, resolving the contradiction between adaptability and device complexity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes motor operating parameters (current, speed, torque) in real-time based on detected reluctance variations. By dynamically adjusting electrical parameters rather than using mechanical transmissions, the system achieves high adaptability to varying load conditions while maintaining relatively simple device structure.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If mechanical transmissions are used for speed control, then the ease of operation is improved, but the reliability deteriorates due to potential equipment damage

Engineering Contradiction:

Improveequipment reliabilityVSAvoidspeed control ease

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent replaces mechanical transmissions and mechanical speed control mechanisms with an electronically controlled motor system. The microcomputer controller adjusts motor parameters electrically, eliminating mechanical wear and failure points while maintaining ease of speed control through digital adjustment, thus improving reliability without sacrificing operational ease.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If high power is delivered to the working element, then the productivity is improved, but the object-affected harmful factors increase such as splintering and equipment damage

Engineering Contradiction:

Improvecutting speedVSAvoidsplintering and equipment damage

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The system dynamically adjusts motor power output based on real-time reluctance detection. When the working element encounters resistance (indicating potential splintering or equipment damage risk), the controller automatically reduces power delivery. This dynamic adjustment allows high productivity during normal operation while preventing harmful effects when load conditions change, resolving the contradiction between productivity and harmful factors.

Inventive Principle:

Principle #15Dynamics

4Measurement precision

If simple control mechanisms are used, then the device complexity is reduced, but the measurement precision of operating characteristics deteriorates

Engineering Contradiction:

Improveoperating characteristic sensingVSAvoidcontrol circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The system uses motor reluctance as an intermediary parameter to indirectly measure working element load conditions. By monitoring changes in motor electrical characteristics (current, reluctance) rather than directly measuring working element parameters, the system achieves high measurement precision with relatively simple sensing circuits, resolving the contradiction between measurement precision and device complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enhances operational efficiency by reducing maintenance needs, preventing splintering and equipment damage, and improving the quality of cuts by dynamically responding to load changes, thereby ensuring safer and more precise tool operation.

Implementation Method 1

A digital variable reluctance (DVR) controller senses changes in motor reluctance and current

Methodology Applied

Scientific EffectVariable reluctance: Magnetic Reluctance

Data Source

PatentUS10189136B2Power tool with digital variable reluctance motor control

Publication Date: 2019.01.29 JPW IND INC

AI summary

A power tool includes a control for the motor of the power tool that senses an operating characteristic of the motor and controls the operation of the power tool based on the sensed characteristic. The sensed characteristic includes variations in reluctance of the motor. A controller may sense changes on load on the motor as a result of interaction between a working element such as a saw blade or drill bit and the work piece. The controlled operation may include variation in speed or torque or both, or may include stopping the motor. Emergency conditions may be sensed by changes in reluctance.