Linear Actuator Control System for Positioning Accuracy
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Solution Overview
Problem
Unipolar-type linear actuators experience efficiency decreases and positioning issues due to output characteristic differences across stroke positions, leading to increased positioning time and reduced followability, as the magnetic flux density varies with stroke position, output level, and direction, causing magnetization saturation.
Innovation Solution
A control system for linear actuators that includes a position calculation unit, control amount calculation unit, direction determination unit, gain calculation unit, and correction unit to calculate and apply a correction gain based on stroke position, output level, and output direction, thereby correcting the control amount to maintain consistent thrust constant across different operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gain correction based on stroke position is applied, then positioning characteristics improve, but output characteristic differences during high-speed driving still influence positioning time and followability
Solution Approach 1:
The invention changes the correction approach from position-based gain adjustment to a comprehensive correction that considers stroke position, output level, and output direction simultaneously. By calculating correction gains based on these three parameters and applying them to the control amount, the system compensates for output characteristic differences more effectively, improving both positioning accuracy and dynamic performance during high-speed driving.
2Productivity
If field magnet unit shape is modified to reduce middle-stroke efficiency, then end-part efficiency improves, but rated output and idle power consumption are compromised
Solution Approach 1:
Instead of modifying the overall field magnet unit shape, the invention applies local quality correction through position-dependent gain adjustment. The correction gain varies locally based on stroke position, output level, and output direction, compensating for efficiency variations at different stroke positions without changing the physical structure of the field magnet unit. This preserves rated output and idle power consumption while improving end-part efficiency.
3Device complexity
If unipolar-type linear actuator is used for compact size and ease of control, then device complexity reduces, but output characteristic differences cause positioning performance degradation
Solution Approach 1:
The invention introduces feedback correction by calculating correction gains based on actual stroke position, output level, and output direction. This feedback mechanism compensates for the inherent output characteristic differences of the unipolar-type linear actuator, maintaining simple device structure while significantly improving positioning characteristics and reducing the influence of magnetization saturation.
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 control system effectively reduces the influence of output characteristic differences, improving drivability and followability by maintaining a constant thrust constant, thereby enhancing positioning accuracy and efficiency across the stroke range.
Implementation Method 1
A linear actuator includes a coil and a magnetic field unit, and is configured to drive a drive target object along a main axis
Implementation Method 2
This is caused by the magnetization (magnetic flux density relative to the magnetic field) of a yoke, which configures a field magnet unit, not being infinite but instead becoming saturated
Data Source
AI summary
A control system of a linear actuator that is provided with a coil and a magnetic field unit, and is configured to drive a drive target object along a main axis, is configured to acquire position information of the drive target object or the linear actuator from an encoder and calculate the position information of the drive target object and the linear actuator, calculate a control amount to control drive of the linear actuator, based on position information of the drive target object and a target position to move the drive target object, determine an output level of the linear actuator based on the control amount, determine an output direction of the linear actuator, based on the control amount and the position information of the linear actuator, calculate a correction gain for correcting the control amount, based on the position information, the output level, and the output direction of the linear actuator, and correct the control amount by using the correction gain.