X-ray computed tomographic apparatus
View Patent ↗An X-ray computed tomographic apparatus includes a rotary frame, a mechanism which rotatably supports the rotary frame, an X-ray tube which is mounted to the rotary frame, an X-ray detector which is mounted to the rotary frame, a plurality of rotor magnets which is arranged in the rotary frame, a plurality of stator coils which is opposed to the rotor magnets, an MR sensor which detects a magnetic-flux variation accompanied by a movement of the rotor magnets, and a position specifying unit which specifies a magnetic-pole position of each rotor magnet with respect to each stator coil on the basis of an output of the MR sensor and a convergence time from a vibration start of the rotary frame caused by a short-time excitation of the stator coil to a vibration stop of the rotary frame.
1. An X-ray computed tomographic apparatus comprising:
a rotary frame;
a mechanism which rotatably supports the rotary frame;
an X-ray tube which is mounted to the rotary frame;
an X-ray detector which is mounted to the rotary frame;
a plurality of rotor magnets which is arranged in the rotary frame;
a plurality of stator coils which is opposed to the rotor magnets;
a sensor which detects a magnetic-flux variation accompanied by a movement of the rotor magnets; and
a position specifying unit which specifies a magnetic-pole position of each rotor magnet with respect to each stator coil on the basis of an output of the sensor and a convergence time from a vibration start of the rotary frame caused by a short-time excitation of the stator coil to a vibration stop of the rotary frame.
2. The X-ray computed tomographic apparatus according to claim 1 , further comprising:
a storage unit which stores a correspondence table between the convergence time and the magnetic-pole position.
3. The X-ray computed tomographic apparatus according to claim 1 , further comprising:
a storage unit which stores a plurality of correspondence tables between the convergence time and the magnetic-pole position having different excitation current values.
4. The X-ray computed tomographic apparatus according to claim 3 , wherein the position specifying unit selectively uses the plurality of correspondence tables in accordance with the excitation current values.
5. The X-ray computed tomographic apparatus according to claim 1 , wherein the position specifying unit determines whether the convergence time exceeds a predetermined time.
6. The X-ray computed tomographic apparatus according to claim 5 , further comprising:
a controller which decreases the excitation current value of the stator coil when it is determined that the convergence time exceeds the predetermined time.
7. An X-ray computed tomographic apparatus comprising:
a rotary mechanism which rotates an X-ray tube and an X-ray detector;
a direct-drive motor which is mounted to the rotary mechanism; and
a position specifying unit which specifies a magnetic-pole position of a rotor magnet with respect to a stator coil on the basis of a convergence time from a vibration start of a frame caused by a short-time excitation of the stator coil to a vibration stop of the frame.
8. The X-ray computed tomographic apparatus according to claim 7 , further comprising:
a storage unit which stores a correspondence table between the convergence time and the magnetic-pole position.
9. The X-ray computed tomographic apparatus according to claim 7 , further comprising:
a storage unit which stores a plurality of correspondence tables between the convergence time and the magnetic-pole position having different excitation current values.
10. The X-ray computed tomographic apparatus according to claim 9 , wherein the position specifying unit selectively uses the plurality of correspondence tables in accordance with the excitation current values.
11. The X-ray computed tomographic apparatus according to claim 7 , wherein the position specifying unit determines whether the convergence time exceeds a predetermined time.
12. The X-ray computed tomographic apparatus according to claim 11 , further comprising:
a controller which decreases the excitation current value of the stator coil when it is determined that the convergence time exceeds the predetermined time.
13. An apparatus comprising:
a rotary mechanism;
a direct-drive motor which is mounted to the rotary mechanism; and
a position specifying unit which specifies a magnetic-pole position of a rotor magnet with respect to a stator coil or a value corresponding to the magnetic-pole position on the basis of a convergence time from a vibration start of a frame caused by a short-time excitation of the stator coil to a vibration stop of the frame or a value corresponding to the convergence time.