Linear Actuator Control for Magnetic Pole Position Detection
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Solution Overview
Problem
Linear motors face challenges in accurately determining the magnetic pole position, especially when the mover is shifted by 180° or when external forces like gravity interfere, leading to incorrect position detection and inability to pull the mover to the predetermined magnetic pole position.
Innovation Solution
A control device for a linear actuator that includes a magnetic pole position estimation mechanism using pulse energization to determine the mover's position, a brake device to manage external forces, and direct current excitation to set and maintain the magnetic pole position, allowing for improved accuracy in pole position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If DC excitation is performed to determine magnetic pole position, then the mover can be pulled to the predetermined magnetic pole position, but the position cannot be determined correctly when the mover is shifted by 180° or when external forces like gravity act on the mover
Solution Approach 1:
The brake device is activated before pulse energization to prevent the mover from moving under external forces during the position detection process. This preliminary action ensures that the mover remains stationary while pulse energization is applied, allowing accurate detection of the magnetic pole position even when gravity or other external forces are acting on the system.
Solution Approach 2:
Pulse energization is applied periodically to the linear motor to detect the magnetic pole position. By applying short pulses of energization and observing the mover's response, the system can determine which 90° section the mover is located in, thereby improving position detection accuracy without continuous energization.
2Measurement precision
If the brake device is turned on before pulse energization and turned off after position estimation, then position detection accuracy is improved, but the control process becomes more complex
Solution Approach 1:
The control device integrates the brake control function within the existing position detection control logic. The brake device is automatically activated before pulse energization and deactivated after position estimation without requiring separate control mechanisms, allowing the system to improve position detection accuracy while minimizing additional control complexity.
3Measurement precision
If pulse energization is used to estimate the magnetic pole position by detecting movement direction, then position detection accuracy is improved, but energy consumption increases
Solution Approach 1:
Instead of continuous energization, pulse energization is applied periodically to detect the magnetic pole position. Short pulses are applied to each of the three phases in sequence, and the mover's movement direction during these brief pulses is observed to determine the 90° section. This periodic action significantly reduces energy consumption compared to continuous energization while maintaining detection accuracy.
Solution Approach 2:
The system applies partial energization only to the specific phase that corresponds to the estimated magnetic pole position, rather than energizing all phases simultaneously or continuously. This partial action approach reduces energy consumption while still providing sufficient force to move the mover for position detection purposes.
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 enhances the accuracy of magnetic pole position detection in linear motors, enabling precise control and movement even under external forces like gravity, without the need for additional sensors, thus improving operational reliability and reducing device size.
Implementation Method 1
A linear motor used for a linear actuator or the like cannot generate a thrust according to the thrust constant of the linear motor unless energization is performed according to a relative positional relationship (a magnetic pole position) between a plurality of coils provided on one of a mover or a stator and a driving magnet provided on the other
Implementation Method 2
the brake device may be configured to brake a movement of the mover in a first direction in which the mover is movable and to not brake a movement thereof in a second direction opposite to the first direction
Data Source
AI summary
A control device for controlling a linear actuator having a linear motor and a brake device includes a magnetic pole position estimation means to estimate which of a plurality of sections obtained by dividing a magnetic pole position of 0° to 360°, the mover is located in on the basis of a direction of movement of the mover by pulse energization, a magnetic pole position setting means to perform direct current excitation at an estimated magnetic pole position estimated by the magnetic pole position estimation means and set the estimated magnetic pole position as a magnetic pole position of the mover, and a brake control means to turn on a brake device before pulse energization by the magnetic pole position estimation means is performed and turn off the brake device after the magnetic pole position estimation means estimates the section in which the mover is located.