Machine Tool Control Apparatus for Power Outage Collision Prevention

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Solution Overview

Problem

Existing machine tool control systems face challenges in reliably and quickly halting the feed shaft motor during a power outage at the AC power supply side, leading to potential collisions due to delayed motor shutdowns caused by issues with regenerative power management.

Innovation Solution

A control apparatus that includes a converter, feed shaft motor inverter, main spindle motor inverter, power outage detection unit, voltage detection unit, and control unit, which outputs specific commands to manage DC voltage levels by accelerating or decelerating the main spindle motor based on detected voltage conditions, ensuring timely motor shutdown and preventing collisions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If regenerative power is stored in the DC link during motor deceleration, then energy conservation is improved, but DC voltage increases excessively during power outage causing delayed motor shutdown

Engineering Contradiction:

Improveregenerative power recoveryVSAvoidmotor shutdown timing

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent extracts the regenerative power from the DC link by introducing a regenerative power discharge device that discharges excess regenerative power to a discharge device (such as a resistor) when DC voltage exceeds a predetermined threshold. This prevents DC voltage from increasing excessively during power outage while still allowing regenerative power to be recovered under normal conditions, thus resolving the contradiction between energy conservation and reliable motor shutdown timing.

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-affected harmful factors

If feed shaft motor is decelerated upon power outage detection, then collision prevention is improved, but DC voltage fluctuation causes control instability

Engineering Contradiction:

Improvefeed shaft collisionVSAvoidDC voltage stability

Core Design Contradiction:

Object-affected harmful factorsVSStability of the object's composition

Solution Approach 1:

The patent implements a feedback control mechanism where the DC voltage is continuously monitored and compared with predetermined threshold values. When DC voltage exceeds the upper threshold during power outage, the regenerative power discharge device is activated to discharge excess power, thereby stabilizing DC voltage while enabling safe feed shaft motor deceleration. This feedback-based approach resolves the contradiction between collision prevention and voltage stability.

Inventive Principle:

Principle #23Feedback

3Reliability

If converter capacity is increased to handle regenerative power, then power management reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidconverter configuration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent introduces a dynamic power management approach where the regenerative power discharge device is selectively activated based on real-time DC voltage conditions. Instead of permanently increasing converter capacity, the system dynamically adjusts power flow by discharging regenerative power when needed (during power outage or high voltage conditions) and recovering it when safe. This dynamic approach maintains power management reliability without permanently increasing converter complexity or cost.

Inventive Principle:

Principle #15Dynamics

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 solution enables reliable and early halting of the feed shaft motor upon a power outage, effectively preventing collisions by managing DC voltage fluctuations and maintaining system stability.

Implementation Method 1

a converter for performing a bi-directional power conversion between an AC voltage of an AC power supply side and a DC voltage at a DC link being a DC side

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

a feed shaft motor inverter for performing a bi-directional power conversion between the DC voltage at the DC link and an AC voltage of a feed shaft motor side

Methodology Applied

Scientific EffectInversion:

Implementation Method 3

an inverter, which is connected to a DC link (direct current link) being a DC side of the converter, for performing a bi-directional power conversion between DC power of the DC link and AC power which is driving power for the motors or regenerative power

Methodology Applied

Scientific EffectBi-directional power conversion:

Data Source

PatentUS9092027B2Control apparatus of machine tool including feed shaft motor and main spindle motor

Publication Date: 2015.07.28 FANUC LTD

AI summary

A control apparatus includes a converter for converting an AC voltage to a DC voltage, a feed shaft motor inverter for converting the DC voltage to an AC voltage for a feed shaft motor, a main spindle motor inverter for converting the DC voltage to an AC voltage for a main spindle motor, a power outage detection unit for detecting a power outage of the AC power supply, a voltage detection unit for detecting the DC voltage, and a control unit which, upon power outage of the AC power supply side, outputs a feed shaft motor deceleration command to the feed shaft motor inverter and outputs, to the main spindle motor inverter, a main spindle motor acceleration command when a DC voltage is greater than an upper limit and a main spindle motor deceleration command when the DC voltage is less than a lower limit.