Magnetic Pole Detection in X-ray CT Air Bearing Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing X-ray CT apparatus with direct drive motor driving mechanisms face challenges in quickly estimating the magnetic pole position at startup due to low friction resistances from air bearings, leading to prolonged data acquisition start-up times.
Innovation Solution
The implementation of a magnetic pole detection unit and a brake mechanism that applies a brake load to the rotation frame during startup, allowing for precise detection of the magnetic pole position based on vibration timing and encode pulses, enabling rapid stabilization and data acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If air bearings are used to support the rotation frame for non-contacting support, then friction resistance is reduced and operational smoothness is improved, but the vibration convergence time is prolonged making magnetic pole position detection difficult
Solution Approach 1:
The brake mechanism is activated before magnetic pole position detection to artificially create friction resistance. This preliminary action counteracts the low friction environment caused by air bearings, enabling the rotation frame to converge vibrations quickly during detection. After detection completes, the brake is released to restore smooth non-contact operation.
Solution Approach 2:
The system dynamically adjusts friction characteristics by controlling the brake mechanism. During magnetic pole position detection, the brake is engaged to increase friction for rapid vibration convergence. During normal operation, the brake is disengaged to maintain low friction non-contact support. This dynamic switching resolves the contradiction between detection speed and operational smoothness.
2Speed
If the rotation frame is excited during a very short time period to estimate magnetic pole position, then detection speed is improved, but accurate detection becomes difficult due to low friction resistance from air bearings
Solution Approach 1:
The brake mechanism is activated before excitation to create artificial friction resistance. This preliminary action ensures that when the rotation frame is excited during a short time period, the vibrations will converge quickly and accurately, enabling precise magnetic pole position detection without requiring prolonged excitation.
Solution Approach 2:
The brake mechanism acts as an intermediary that temporarily modifies the friction characteristics of the air bearing system during detection. By introducing controlled friction only when needed for detection, the system achieves both fast and accurate magnetic pole position estimation without compromising the low-friction operational state.
3Loss of time
If conventional ball bearings and slip rings are used, then friction resistance provides natural vibration convergence for magnetic pole detection, but mechanical vibrations and operation sounds increase causing discomfort
Solution Approach 1:
The system replaces conventional ball bearings and slip rings with air bearings for non-contact support. To compensate for the loss of friction-based vibration convergence, a brake mechanism is introduced that temporarily provides friction only during detection. This substitution eliminates continuous mechanical vibrations and operation sounds while enabling rapid vibration convergence during detection through controlled brake application.
Solution Approach 2:
The brake mechanism is activated periodically only during magnetic pole position detection rather than continuously. This periodic application of friction allows the system to enjoy low-friction smooth operation during most of the time, while still achieving rapid vibration convergence when detection is needed. The periodic action resolves the contradiction between operational quietness and detection efficiency.
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 solution allows for quick and accurate detection of the magnetic pole position, enabling rapid startup and initiation of projection data acquisition in X-ray CT apparatus with non-contacting support systems, improving operational efficiency and reducing noise.
Implementation Method 1
the brake mechanism is configured to apply a brake load to the rotation frame when detecting the magnetic pole position
Implementation Method 2
the non-contacting rotation power transmission is performed between the windings on the rotation frame and the magnets on the gantry fixing unit. More specifically, the rotation frame is directly rotationally driven as a non-contacting rotor member of a repulsion motor by repulsions between the magnetic fluxes generated by supplying a current to the windings of the rotation frame
Implementation Method 3
supporting the rotation frame by the fixed gantry using air bearings makes it difficult to easily estimate the magnetic pole position
Data Source
AI summary
An X-ray CT apparatus includes a fixed gantry having a plurality of stator coils arranged in a circle and mounted on the fixed gantry. A ring-shaped rotation frame of the CT apparatus includes a plurality of rotor magnets facing the plurality of stator coils. The CT apparatus further has an X-ray tube and an X-ray detector situated on the rotation frame to face each other and a supporting unit configured to provide non-contact support of the rotation frame on the fixed gantry. A magnetic pole detection unit of the apparatus is configured to detect a magnetic pole position of the rotor magnet at a start-up time of the plurality of stator coils and a brake mechanism of the apparatus is configured to apply a brake load to the rotation frame when detecting the magnetic pole position and to remove the brake load after detecting the magnetic pole position.