Motorized Measurement Arm Stop Holding for Repeatable Positioning

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Solution Overview

Problem

Existing motorized measurement arm apparatuses for machine tools suffer from repeatability issues in their operative positions, especially under machine vibrations or when carrying heavy sensors, leading to measurement uncertainty.

Innovation Solution

A motorized measurement arm apparatus with a mechanical stop arrangement maintained by a motor controller, which supplies a holding current to the motor after initial engagement, reducing thermal expansion and maintaining engagement torque without further rotation, thereby enhancing positional repeatability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a mechanical stop arrangement with spring engagement is used to define the operative position, then the apparatus is compact and robust, but the repeatability of the operative position degrades under machine vibrations or when carrying heavy sensors

Engineering Contradiction:

Improverepeatability of operative positionVSAvoideffect of machine vibrations and heavy sensor weight

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the purely mechanical spring-based engagement system with an electromechanical system. A motor (electromagnetic actuator) is used to apply a controlled holding force to the mechanical stop arrangement, substituting the passive mechanical spring force with an active electromagnetic force that can be precisely controlled to maintain engagement under varying conditions including vibrations and heavy sensor weights.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the physical state or parameters of the engagement force by using a motor to dynamically adjust and maintain the holding force on the mechanical stop. The motor controller can modulate the electromagnetic force to compensate for external disturbances such as vibrations and variable sensor weights, thereby maintaining consistent engagement and improving repeatability.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the motor is continuously energised to maintain engagement of the mechanical stop, then positional repeatability is improved, but thermal expansion may occur

Engineering Contradiction:

Improvepositional repeatabilityVSAvoidmotor temperature and thermal expansion

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent employs periodic or intermittent motor energization rather than continuous operation. The motor controller activates the motor only when needed to maintain mechanical stop engagement, allowing thermal dissipation during idle periods. This periodic action maintains positional repeatability while preventing excessive temperature buildup and thermal expansion that would occur with continuous motor operation.

Inventive Principle:

Principle #19Periodic action

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 provides improved metrology accuracy and reduced measurement uncertainty by maintaining a consistent engagement force, even under vibrations or when carrying heavy sensors, ensuring precise sensor positioning.

Implementation Method 1

a motor controller for energising the motor to move the arm member relative to the base, wherein the motor controller is configured to energise the motor when the arm member is in the operative position to maintain engagement of the mechanical stop arrangement

Methodology Applied

Scientific EffectElectromagnetic torque: Electromagnetic Induction

Implementation Method 2

the operative position being defined by engagement of a mechanical stop arrangement

Methodology Applied

Scientific EffectKinematic constraint: Mechanical Force

Data Source

PatentUS20240198474A1A motorised measurement arm apparatus for a machine tool

Publication Date: 2024.06.20 RENISHAW PLC

AI summary

A motorised measurement arm apparatus for a machine tool includes a base for attachment to the machine tool and an arm member extending from the base for holding one or more sensors. The arm member is moveable relative to the base between a stowed position and an operative position, the operative position being defined by engagement of a mechanical stop arrangement. The apparatus also has a motor for moving the arm member relative to the base and a motor controller for energising the motor to move the arm member relative to the base. The motor controller is configured to energise the motor when the arm member is in the operative position to maintain engagement of the mechanical stop arrangement. An operative position having improved repeatability is thus obtained.