Polishing Apparatus Load Control via Magnetic Position Sensing
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Solution Overview
Problem
Conventional polishing apparatuses face challenges in achieving accurate load control, especially when encountering tiny protrusions or foreign substances, due to a narrow measurable load range and rapid load changes, which complicates precise polishing processes.
Innovation Solution
The polishing apparatus employs a position sensor, such as a linear scale, in conjunction with the spring constant value of an elastic mechanism to control the load applied to the polishing body, allowing for expanded load detection range and precise positioning, thereby maintaining accurate polishing even when encountering obstacles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load cell is used to measure the load applied to the polishing pad, then the load can be measured, but the measurable load range is narrow and rapid load changes cause measurement difficulties
Solution Approach 1:
The patent replaces the mechanical load cell measurement system with a magnetic measurement system. A magnetic sensor detects the position of a magnetic body attached to the polishing pad, and the load is calculated based on the magnetic field strength and sensor position relationship. This substitution eliminates the narrow measurement range limitation of load cells while maintaining measurement accuracy, as the magnetic field can be precisely measured across a wider range of forces.
Solution Approach 2:
The patent introduces a magnetic body as an intermediary between the polishing pad and the measurement system. Instead of directly measuring the load on the polishing pad with a load cell, the magnetic body's position changes in response to load variations, and these position changes are detected by the magnetic sensor. This intermediary approach enables indirect measurement with an expanded dynamic range and improved response to rapid load changes.
2Manufacturing precision
If position control is used to control the driving mechanism, then the position of the polishing pad can be controlled, but accurate load control becomes difficult when rapid load changes occur due to tiny protrusions or foreign substances
Solution Approach 1:
The patent implements a feedback control system where the magnetic sensor continuously monitors the position of the magnetic body, which reflects the actual load conditions. This feedback information is used to adjust the driving mechanism in real-time, maintaining stable load control even when rapid load changes occur due to surface irregularities. The closed-loop feedback compensates for disturbances that open-loop position control cannot handle.
Solution Approach 2:
The patent replaces direct mechanical load sensing with magnetic field-based position sensing. The magnetic sensor detects subtle position changes of the magnetic body that correspond to load variations, providing more sensitive and reliable load information than mechanical load cells. This substitution improves the system's ability to detect and respond to rapid load changes while maintaining manufacturing precision.
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
This approach enables the polishing apparatus to maintain high accuracy and expand the load detection range without relying on load cells, ensuring effective polishing across varying surface conditions.
Implementation Method 1
a head (30) that supports the polishing body (10) via an elastic mechanism (32); wherein the elastic mechanism (32) provides an elastic force in a direction of canceling a load of the head
Implementation Method 2
a position sensor (34) which is connected to the control device (50) and which measures a position of the polishing body (10) with respect to the head (30)
Implementation Method 3
a driving mechanism (24) that causes the head (30) to be relatively moved in a direction in which a separation distance from the material to be polished is changed
Data Source
AI summary
A polishing apparatus includes: a holding section that holds a material to be polished; a polishing body that polishes the material to be polished held by the holding section; a head that supports the polishing body via an elastic mechanism; a driving mechanism that causes the head to be moved in a Z coordinate direction; a control unit that controls the driving mechanism; and a position sensor that measures a position of the polishing body with respect to the head. The load control is performed based on a measurement value of the position sensor and a spring constant value of the elastic mechanism.