Ball Screw Thermal Expansion Compensation in Positioning Devices
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Solution Overview
Problem
Conventional positioning devices using ball screws fail to accurately compensate for thermal displacement errors due to temperature changes, especially when the reference and measurement holding members have different temperatures than the base, leading to positioning inaccuracies.
Innovation Solution
A positioning device that includes temperature and distance detection means to accurately measure the linear expansion of the ball screw, allowing for precise compensation of thermal displacement errors by adjusting the rotational angle of the motor based on the measured temperature differences and linear expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If only the temperature of the base is measured to compensate positioning errors, then the device complexity is reduced, but the positioning precision deteriorates due to temperature differences between the base and holding members
Solution Approach 1:
The temperature measurement system is segmented into multiple independent sensors placed at different locations (base, reference holding member, measurement holding member). Each sensor independently measures the temperature at its specific location, allowing separate compensation calculations for each component's thermal expansion without requiring a complex integrated measurement system.
Solution Approach 2:
Temperature sensors act as intermediary elements that bridge the gap between thermal conditions and positioning accuracy. By introducing these intermediary measurement devices, the system can detect temperature differences and use them to calculate compensation amounts, thereby resolving the contradiction between simple measurement and high precision.
2Manufacturing precision
If temperature sensors are added to measure temperatures of holding members, then the positioning precision is improved, but the device complexity increases
Solution Approach 1:
The solution segments the temperature measurement function into separate, simple sensors distributed at critical locations rather than using a single complex measurement system. This segmentation allows each sensor to perform a simple, dedicated function while collectively providing comprehensive thermal data for accurate compensation.
Solution Approach 2:
The holding members are equipped with temperature sensors that enable them to self-report their thermal state. This self-service approach allows the system to automatically detect temperature differences and calculate compensation without requiring complex external monitoring systems, thereby improving precision with minimal added complexity.
3Ease of operation
If the temperatures of reference and measurement holding members are assumed equal to the base temperature, then the measurement process is simplified, but the measurement precision deteriorates due to thermal differences from bearing friction
Solution Approach 1:
The temperature measurement process is segmented into multiple independent measurements at different locations rather than a single assumed temperature value. By placing sensors at the base, reference holding member, and measurement holding member, the system captures the actual thermal distribution caused by bearing friction and other heat sources, enabling precise compensation calculations.
Solution Approach 2:
The system implements feedback by continuously measuring temperatures at multiple locations and using this information to calculate and apply compensation amounts. The temperature sensors provide real-time feedback on thermal conditions, allowing the control device to adjust positioning commands dynamically based on actual thermal expansion, thereby maintaining measurement precision while keeping the process simple through automated feedback loops.
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 device achieves enhanced positioning accuracy by accurately measuring thermal displacement and compensating for temperature-induced errors, ensuring precise positioning of the movable body.
Implementation Method 1
a temperature of the ball screw is detected by temperature detection means
Implementation Method 2
an amount of linear expansion of the ball screw is obtained on the basis of the detected temperature and a linear expansion coefficient of the ball screw
Data Source
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AI summary
Temperatures of a base (2), a support member (5), and a support member (6) are measured, and amounts of linear expansion of the base (2), the support member (5), and the support member (6) due to temperature differences from a reference temperature are computed. An amount of linear expansion of a ball screw (7) with respect to the support member (6) is measured. An amount of linear expansion of a lead of the ball screw (7) is computed based on the sum of the aforementioned amounts of linear expansion, and an amount of rotation of the ball screw (7) is adjusted from an amount of rotation of the ball screw (7) at the reference temperature, to an amount of rotation of the ball screw (7), which corresponds to the amount of linear expansion of the lead at a predetermined temperature.