JP2009077758A - Abnormality detector and magnetic resonance imaging apparatus provided with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the technique for detecting the abnormality of an absolute encoder and a signal line extending from the absolute encoder without the need of a special operational circuit of adding bits or the like. <P>SOLUTION: While a first signal train comprising the data bit group of two or more digits indicating the rotation angle of a detection object outputted from the absolute encoder is changed in either increasing or decreasing direction, when the bits of the lower orders are not changed while the N-th bit of the signal train is changed for two or more times, the abnormality is judged. Also, while a second signal train comprising the data bit group of two or more digits indicating the rotation amount of a detection object is changed in either increasing or decreasing direction, when the bits of the lower orders are not changed while the N-th bit of the signal train is changed for two or more times, the abnormality is judged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging apparatus that detects the position of a bed with an absolute encoder, and more particularly to detection of an abnormality in a signal path extending from the absolute encoder and the absolute encoder.

  In magnetic resonance imaging (MRI), a nuclear spin in a subject tissue placed in a static magnetic field is excited by a high-frequency signal (RF pulse) having the Larmor frequency, and a magnetic resonance signal ( This is an imaging method for reconstructing image data from MR signals.

  A magnetic resonance imaging apparatus (hereinafter referred to as “MRI apparatus”) is an image diagnostic apparatus that generates image data based on MR signals detected from within a living body, and includes not only anatomical diagnostic information but also biochemical information and Since a lot of diagnostic information such as functional diagnostic information can be obtained, it is indispensable in the field of today's diagnostic imaging.

  The MRI apparatus includes a magnet gantry, a couch unit that inserts a subject into the magnet gantry, and a control unit that controls driving of the magnet gantry and the couch unit and reconstructs image data. The subject is placed on the top plate of the bed unit, the top plate is moved into the magnet stand, and the subject is inserted into the magnet stand.

  In order to reconstruct an image of a desired part, accurate alignment of the top plate is necessary. In addition, in order to observe a desired portion having a predetermined width in time series, a repetitive operation of moving the top plate in the magnet mount in the insertion direction or moving in the pulling direction may be performed. Even in repeated operations, in order to obtain a good image, it is necessary to reciprocate the top board at an accurate turning point.

  Therefore, the MRI apparatus is provided with an absolute encoder in order to accurately detect the movement of the top plate. The absolute encoder monitors the rotation angle and rotation amount of the drive unit that moves the top plate, and outputs the rotation angle and rotation number as absolute values. The encoder signal output from the absolute encoder is composed of a plurality of digits of data bits. The rotation angle and the number of rotations are uniquely determined by the value taken by the data bit group. Normally, the data bit group output by the absolute encoder outputs a value that is incremented or decremented by one every time the rotation angle or the number of rotations is displaced by a predetermined amount in either direction.

  Since this absolute encoder outputs a parallel signal, there is a greater risk of disconnection or the like than an incremental encoder. Also, there is a possibility that the lower bits are not noticed even if the bit is disconnected.

  Therefore, a parity check, a sum check, a CRC, and the like are well known as methods for detecting a so-called bit error caused by an abnormality such as an absolute encoder abnormality, a signal line extending from the absolute encoder, or an interface board disconnection.

  These bit error detection methods add error check bits to the encoder signal (see, for example, “Patent Document 1” and “Patent Document 2”). For this reason, the conventional method for detecting a bit error in an absolute encoder requires a special arithmetic circuit for adding bits to the transmission side that outputs the encoder signal.

Japanese Patent Application Laid-Open No. 06-94480 JP 09-280892 A

  However, the bed unit is installed in a shield room together with a magnet base that generates a strong magnetic field. Therefore, in order to install this special arithmetic circuit on the transmission side, it is necessary to install it in a form that shields a strong magnetic field, leading to an increase in cost. In addition, an RF pulse or a high magnetic field generated in the shield room causes a malfunction of the arithmetic circuit, and there is a risk that an abnormality of the absolute encoder or the signal line cannot be detected.

  Furthermore, there is a risk that this special circuit will radiate noise to the receiving RF coil of the MRI apparatus.

  The present invention has been made in view of the above-described problems, and its purpose is to eliminate an abnormality in a signal path extending from an absolute encoder or an absolute encoder without requiring a special arithmetic circuit such as adding a bit. It is to provide a technique for detecting.

  The invention described in claim 1 for solving the above-mentioned problems is a static magnetic field generating means for generating a static magnetic field in a diagnostic space, a gradient magnetic field coil for generating a gradient magnetic field in the static magnetic field, and the diagnostic space. A top plate for inserting a subject from the entrance to the inside of the diagnostic space, a drive unit for driving the top plate, a first bit string of a plurality of digits representing a rotation angle of the drive unit, or in addition thereto An absolute encoder that outputs a second bit string of a plurality of digits representing the rotational speed of the drive unit as a signal sequence, and the signal sequence is input from the absolute encoder via a signal path, and the drive unit is based on the signal sequence And a control unit that outputs a drive signal to the Nth bit of any one of the signal sequences when the value of the signal sequence changes in one direction of increase or decrease. Change more than once During, if there is no change to the lower bits than, comprise determining means to be abnormal, characterized by.

  The invention according to claim 2 for solving the above-mentioned problems is a static magnetic field generating means for generating a static magnetic field in a diagnostic space, a gradient magnetic field coil for generating a gradient magnetic field in the static magnetic field, and the diagnostic space. A top plate for inserting a subject from the entrance to the inside of the diagnostic space, a drive unit for driving the top plate, a first bit string of a plurality of digits representing a rotation angle of the drive unit, or in addition thereto An absolute encoder that outputs a second bit string of a plurality of digits representing the rotational speed of the drive unit as a signal sequence, and the signal sequence is input from the absolute encoder via a signal path, and the drive unit is based on the signal sequence And a control unit that outputs a drive signal to the control unit, wherein the control unit is lower than the Nth bit of any one of the signal sequences when the value of the signal sequence is changing in any one direction All of By Tsu Doo changes, if there is no change in the N-th bit, comprise determining means to be abnormal, characterized by.

  The invention according to claim 3 for solving the above-mentioned problems is a static magnetic field generating means for generating a static magnetic field in a diagnostic space, a gradient magnetic field coil for generating a gradient magnetic field in the static magnetic field, and the diagnostic space. A top plate for inserting a subject from the entrance to the inside of the diagnostic space, a drive unit for driving the top plate, a first bit string of a plurality of digits representing a rotation angle of the drive unit, or in addition thereto An absolute encoder that outputs a second bit string of a plurality of digits representing the rotational speed of the drive unit as a signal sequence, and the signal sequence is input from the absolute encoder via a signal path, and the drive unit is based on the signal sequence A control unit that outputs a drive signal to the second bit string when the values of the first and second bit strings change in one direction of increase or decrease. Lower bit While changes more than once, if the bit is not changed to the first bit string, comprise determining means to be abnormal, characterized by.

  The invention according to claim 4 for solving the above-mentioned problems is a static magnetic field generating means for generating a static magnetic field in a diagnostic space, a gradient magnetic field coil for generating a gradient magnetic field in the static magnetic field, and the diagnostic space. A top plate for inserting a subject from the entrance to the inside of the diagnostic space, a drive unit for driving the top plate, a first bit string of a plurality of digits representing a rotation angle of the drive unit, or in addition thereto An absolute encoder that outputs a second bit string of a plurality of digits representing the rotational speed of the drive unit as a signal string, and at least one of the above when the value of the signal string changes in one direction of increase or decrease A sensor that detects the movement of the top plate by a distance that changes the Nth bit of the signal sequence twice or more, and outputs a detection signal; and the signal sequence is input from the absolute encoder through a signal path, and the signal Column And a control unit that outputs a drive signal to the drive unit, and the control unit outputs a bit lower than the N-th bit of the signal sequence when the sensor outputs the detection signal. If there is no change, it is determined to be abnormal.

  The invention according to claim 5 for solving the above-mentioned problem is a plurality of first bit strings representing a rotation angle of a detection target, or a plurality of second bit strings representing a rotation speed of the detection target in addition to this. When the signal string is input via a signal path from an absolute encoder that outputs the signal string as a signal string, and the value of the signal string changes in one direction of either increase or decrease, N bits of any of the signal strings While the eye changes twice or more, if there is no change in the lower bits, it is determined that there is an abnormality.

  The invention according to claim 6 for solving the above-mentioned problem is a plurality of digit first bit strings representing the rotation angle of the detection object, or a plurality of digit second bit strings representing the rotation speed of the detection object in addition to this. When the signal string is input via a signal path from an absolute encoder that outputs the signal string as a signal string, and the value of the signal string changes in one direction of either increase or decrease, N bits of any of the signal strings If there is no change in the Nth bit before all the bits below the eye change, it is determined that an abnormality has occurred.

  In order to solve the above-mentioned problem, the invention according to claim 7 is a plurality of digit first bit strings representing the rotation angle of the detection object, or a plurality of digit second bit strings representing the rotation number of the detection object. When the signal sequence is input via a signal path from an absolute encoder that outputs the signal sequence as a signal sequence, and the first and second signal sequences change in one direction of increase or decrease, the second bit sequence If there is a bit that has not changed in the first bit string while the least significant bit of the bit changes twice or more, it is determined that there is an abnormality.

  The invention according to claim 8 for solving the above-mentioned problem is a plurality of first digit strings representing a rotation angle of a detection target for moving the device, or a plurality of digits representing the number of rotations of the detection target in addition to this. When the signal sequence is input via a signal path from an absolute encoder that outputs the second bit sequence as a signal sequence, and the value of the signal sequence changes in one direction of either increase or decrease, A sensor that detects the movement of the device by a distance that changes the Nth bit of the signal sequence at least twice, and outputs a detection signal; and when the sensor outputs the detection signal, If there is no change in the bits lower than the Nth bit, it is determined that there is an abnormality.

  In the present invention, as long as the signal sequence output from the absolute encoder can be received, a bit error can be detected on the receiving side without providing a special arithmetic circuit for adding a bit for detecting the bit error. Or, it is possible to judge the abnormality of the absolute encoder. Therefore, an increase in manufacturing cost can be prevented.

  In addition, in the MRI apparatus, providing this special arithmetic circuit in the shield room creates a risk of noise emission to the receiving RF coil, and also causes a risk of malfunction of the arithmetic circuit due to an RF pulse or a high magnetic field. In the present invention, such a risk does not occur.

  Hereinafter, embodiments of an abnormality detection technique according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a diagram showing an MRI apparatus 100 that detects an abnormality in a signal path output from an absolute encoder or an absolute encoder.

  The MRI apparatus 100 is an image diagnostic apparatus that generates image data based on MR signals detected from within a living body. The MRI apparatus 100 includes a magnet gantry 10, a couch unit 20, and a control unit 30. The magnet mount 10 excites the nuclear spin of the subject P tissue placed in a static magnetic field with a high-frequency signal (RF pulse) having the Larmor frequency, and a magnetic resonance signal (MR signal) generated along with this excitation. To get. The couch unit 20 inserts the top plate 21 into the magnet gantry 10. A subject P is placed on the top plate 21. The control unit 30 controls driving of the magnet mount 10 and the bed unit 20. Further, the control unit 30 reconstructs an image in the subject P from the MR signal acquired by the magnet mount 10.

  The magnet mount 10 includes a static magnetic field magnet 11, a gradient magnetic field coil 12, a transmission RF (Radio Frequency) coil 13, and a reception RF coil 14.

  The static magnetic field magnet 11 is formed in a hollow cylindrical shape and acts so as to generate a uniform static magnetic field in its internal space. For example, a superconducting magnet is used as the static magnetic field magnet 11.

  The gradient magnetic field coil 12 has a hollow cylindrical shape and is disposed in an internal space formed by the static magnetic field magnet 11. The gradient magnetic field coil 12 is formed by combining three coils corresponding to respective coordinate axes of a preset three-dimensional orthogonal coordinate system (XYZ coordinate system). These three coils are individually supplied with power and generate a gradient magnetic field in which the magnetic field strength is inclined along the X, Y, and Z coordinate axes.

  The Z coordinate axis is arranged along the body axis direction of the subject P (the longitudinal direction of the top plate 21 described later), and the static magnetic field magnet 11 generates a static magnetic field in the Z direction. The gradient magnetic fields in the X, Y, and Z directions correspond to, for example, the slice selection gradient magnetic field, the phase encoding gradient magnetic field, and the readout gradient magnetic field, respectively.

  Here, the gradient magnetic field for slice selection is used to arbitrarily determine the imaging section. The phase encoding gradient magnetic field is used to encode the phase of the magnetic resonance signal in accordance with the spatial position. The readout gradient magnetic field is used to encode the phase of the magnetic resonance signal according to the spatial position.

  The transmission RF coil 13 is disposed in the internal space of the gradient magnetic field coil 12. The transmission RF coil 13 receives a high frequency pulse corresponding to a Larmor frequency and generates a high frequency magnetic field.

  The reception RF coil 14 is disposed in the internal space of the gradient magnetic field coil 12 and includes a plurality of RF coils. The plurality of RF coils each receive a magnetic resonance signal emitted from the subject P due to the influence of the generated high-frequency magnetic field, and output a signal representing the reception result to the control unit 30.

  The bed unit 20 includes a top plate 21. The subject P is placed on the top plate 21. The bed unit 20 on which the subject P is placed inserts the top plate 21 into the internal space (imaging port) of the gradient magnetic field coil 12. Usually, the bed apparatus is installed so that the longitudinal direction of the top plate 21 is parallel to the central axis of the static magnetic field magnet 11.

  The control unit 30 includes a reconstruction unit 31, a display unit 32, an input unit 33, and a control unit 34.

  The reconstruction unit 31 performs image reconstruction processing such as Fourier transform on the magnetic resonance signal data to obtain desired nuclear spin spectrum data and image data in the body of the subject P. Thereby, image data of a tomographic image of the subject P is generated.

  The display unit 32 displays various images and screens based on various data such as spectrum data and image data. The control of the display process is executed by the control unit 34. As this display part 32, arbitrary display devices, such as LCD (Liquid Crystal Display), can be used, for example.

  The input unit 33 receives various designations and information input from the examiner. As the input unit 33, any input device or operation device such as a keyboard, a mouse, a trackball, a joystick, a control panel, or a pen tablet can be used as appropriate.

  The control unit 34 includes a CPU, ROM, RAM, and the like (not shown), and controls each unit of the MRI apparatus 100 individually or in conjunction with each other.

  FIG. 2 is a diagram illustrating a detailed configuration of the bed unit 20 of the MRI apparatus 100 and the control unit 34 that controls the bed unit 20.

  The bed unit 20 is installed in the shield room 200 together with the magnet mount 10, and the control unit 30 is installed outside the shield room 200. The shield room 200 is a leakage magnetic field management area and is provided with a magnetic shield for suppressing the leakage magnetic field of the magnet. This is because the MRI apparatus 100 generates a strong magnetic field and thus affects the human body and peripheral devices and equipment. For this reason, the control unit 30 and the couch unit 20 are connected via the signal path 25. The signal path 25 includes a communication unit 24a, a communication interface 24b, and a signal line.

  The bed unit 20 detects a communication unit that transmits and receives signals to and from the control unit 34 of the control unit 30 via the signal path 25, a drive unit 22 that moves the top plate 21, and a rotation angle and a rotation number of the drive unit 22. And a multi-rotation type absolute encoder 23 (hereinafter simply referred to as “absolute encoder”). The control unit 34 of the control unit 30 becomes a drive control device 341 and an abnormality detection device 342 by executing a program stored in advance.

  A drive signal is output from the drive control device 341. The drive unit 22 includes a motor and a drive mechanism that converts the rotational motion of the motor into linear motion. In the drive unit 22, the motor rotates in response to the input of the drive signal, and this rotational motion is converted into a linear motion by the drive mechanism, and the top plate 21 is moved.

  The absolute encoder 23 detects the rotation angle of the drive unit 22 and outputs a signal string composed of a plurality of digits of data bits representing the rotation angle of the drive unit 22. Further, the number of rotations of the drive unit 22 is detected, and a signal string including a plurality of digits of data bits representing the number of rotations of the drive unit 22 is output. The absolute encoder 23 includes a rotation angle scale having a plurality of sets of tracks having different slit pitch numbers, a rotation speed scale, and a sensor for observing each track at a fixed point and detecting the presence or absence of a slit. In each scale, slits are formed so that when the presence or absence of slits in each track is arranged along the radial direction, the arrangement is uniquely determined by the angle. When signals representing the presence / absence of slits detected by the sensors corresponding to the tracks are arranged, the rotation angle and the number of rotations of the motor are determined by the signal sequence. From the absolute encoder 23, a signal string indicating the presence or absence of a slit detected by this sensor is output as an encoder signal. The encoder signal output from the absolute encoder 23 is input to the control unit 34 as a parallel signal.

  The abnormality detection device 342 analyzes the encoder signal representing the rotation speed and detects an abnormality in the absolute encoder 23 or the signal path 25. FIG. 3 is a block diagram showing the configuration of the abnormality detection device 342. As shown in FIG.

  The abnormality detection device 342 includes an N-th bit change detection unit 343, a signal storage unit 344, a change digit detection unit 345, a change digit storage unit 346, and an abnormality determination unit 347. This configuration is realized by the control unit 34 when the control unit 34 configured by a CPU, a ROM, and a RAM executes a program stored in the ROM.

  The Nth bit change detection unit 343 detects a change in the Nth bit signal of the encoder signal. N is the number of digits of the encoder signal ≧ N ≧ 2. When the Nth bit signal changes, the signal storage unit 344 stores the encoder signal. The change digit detection unit 345 detects a bit whose value lower than the Nth bit has changed. When a bit lower than the Nth bit changes, change digit information representing the digit number of the bit is stored in the change digit storage unit 346. When the Nth bit of the encoder signal changes twice, the abnormality determination unit 347 refers to the change digit storage unit 346 and detects bits that are not stored in the change digit storage unit 346. If a bit that is not stored in the change digit storage unit 346 is detected after the Nth bit of the encoder signal changes and then changes again, it is determined to be abnormal.

  4 and 5 are timing charts showing the relationship between bits of the encoder signal input to the abnormality detection device 342. FIG. FIG. 4 shows a normal timing chart shown when there is no abnormality such as disconnection in the absolute encoder 23 or the signal path 25. FIG. 5 shows an abnormal timing chart shown when there is an abnormality such as disconnection in the absolute encoder 23 or the signal path 25.

  The encoder signal is composed of a data bit string of a plurality of digits. When the rotation of the drive unit 22 is in one direction, the encoder signal counts up or counts up in the direction in which the numerical value indicated by the signal increases or decreases.

  For example, as shown in FIG. 4, it is assumed that the absolute encoder 23 outputs a 4-bit encoder signal, and the rotation speed of the drive unit 22 is the rotation speed represented by an encoder signal such as 0000. The scale of the absolute encoder 23 is optically formed with a code string that is incremented by one every time the rotational speed increases by one.

  In this absolute encoder 23, as the rotation speed becomes 1, 2, 3, 4, 5, 6, 7, 8,..., The encoder signals are 0001, 0010, 0011. , 0100, 0101, 0110, 0111, 1000,... Are incremented by one and output.

  Assuming that the third digit is the Nth bit, when the absolute encoder 23 and the signal path 25 are normal, the rotation number is the fourth rotation, the third digit changes from 0 to 1, and then the rotation number is the eighth rotation. Until the third digit changes from 1 to 0 again, the numerical values of the second and first digits lower than the Nth bit always change at least once.

  On the other hand, as shown in FIG. 5, for example, when the signal path 25 for outputting the signal of the second digit is disconnected, the signal of the second digit is constantly at the low level, so the rotation speed is the fourth rotation. Until the third digit changes from 1 to 0 again after the third digit changes from 0 to 1, the second digit remains 0 and never changes. .

  Therefore, if there is a bit that never changes in the lower bits while the Nth bit changes twice, an abnormality such as a disconnection occurs in the signal path 25 or absolute encoder 23 corresponding to that bit. Will be doing.

  Based on the difference in the output value of the encoder signal between the normal time and the abnormal time, the abnormality detection device 342 detects an abnormality such as disconnection of the absolute encoder 23 or the signal path 25. FIG. 6 is a flowchart showing the operation of the abnormality detection device 342.

  The signal storage unit 344 of the abnormality detection device 342 stores an encoder signal output first as an initial value. When the top plate 21 is manually moved in the top plate free mode or the drive control device 341 outputs a drive signal to the drive unit 22, the encoder signal is sent from the absolute encoder 23 to the abnormality detection device 342 at a constant cycle. Input (S01).

  The N-th bit change detection unit 343 determines whether or not a preset value of the N-th bit has changed in the signal sequence of the input encoder signal (S02). The Nth bit change detection unit 343 compares the value of the Nth bit of the signal sequence of the encoder signal stored in the signal storage unit 344 with the value of the Nth bit of the input encoder signal. For example, it is determined that the value of the Nth bit has changed.

  If it is determined that the value of the Nth bit has changed (S02, Yes), the Nth bit change detection unit 343 clears the value stored so far and stores the input encoder signal in the signal storage unit 344. (S03). The encoder signal stored in the signal storage unit 344 is stored as an encoder signal when the Nth bit changes for the first time.

  Then, the Nth bit change detection unit 343 determines whether the detection start point information is “1” (S04). The Nth bit change detecting unit 343 has detection start point information indicating whether or not the change is the first change after the drive is started. As an initial value, the detection start point information is “0”. If the detection start point information is “0” (S04, No), the Nth bit change detection unit 343 assumes that the change is the first and changes the detection start point information to “1” (S05). The process returns to the encoder signal input waiting in S01 without proceeding with the abnormality detection process. That is, in the initial operation of the drive unit 22, since it is not possible to guarantee that the lower bits change more than once before the Nth bit of the encoder signal changes first, abnormality detection is not performed. .

  When the encoder signal is input again (S01) and the value of the Nth bit has not changed (S02, No), the change digit detector 345 determines whether the detection start point information is “1” (S06). ). If the detection start point information is “0” (S06, No), the abnormality detection has not started yet, and the process returns to the input waiting for the encoder signal in S01.

  On the other hand, if the encoder signal is input again (S01), the value of the Nth bit has not changed (S02, No), and the detection start point information is “1” (S06, Yes), the change digit detection The unit 345 compares the value of bits lower than the N bits of the input encoder signal with the value of bits lower than the N bits stored in the signal storage unit 344 (S07). As a result of the comparison, the change digit detection unit 345 stores change digit information indicating the digit number of the bit whose value changes in the change digit storage unit 346 (S08).

  As long as the encoder signal is input and the value of the Nth bit does not change, the Nth bit change detection unit 343 and the change digit detection unit 345 repeat S01 to S08 and accumulate change digit information.

  When the value of the N-th bit changes again (02, Yes) and the detection start point information is “1” (S04, Yes), the abnormality determination unit 347 changes the change accumulated so far from the change digit storage unit 346. Digit information is read (S09), and it is determined whether there is a bit that is not stored as change digit information (S10). In this determination, the abnormality determination unit 347 searches the read change digit information for whether there is change digit information representing the (N−1) th digit, the (N−2) th digit,. .

  If all the change digit information representing the lower bits than the Nth bit exists (S10, Yes), the abnormality determination unit 347 uses the absolute encoder 23 and the signal path 25 corresponding to the lower bits than the Nth bit. The change digit information stored in the change digit storage unit 346 is cleared (S11). When the change digit storage unit 346 is cleared, the abnormality detection device 342 returns to the encoder signal input waiting process of S01 and continues the abnormality determination process.

  On the other hand, if any of the change digit information indicating the digit number of the bit lower than the N-th bit does not exist (S10, No), the abnormality determination unit 347 indicates that the absolute encoder 23 or the non-existing change digit information is present. The signal path 25 corresponding to the represented bit is determined to be abnormal (S12). If the abnormality determination unit 347 determines that there is an abnormality, the abnormality detection device 342 inputs a signal indicating the abnormality to the drive control device 341. When the drive control signal receives a signal indicating an abnormality, the drive control signal outputs a control signal for stopping each part of the MRI apparatus 100.

  As described above, in this embodiment, when the signal sequence changes in one direction of increase or decrease, while the N-th bit of any signal sequence changes twice or more, the lower order bits are changed. If there was no change, it was judged as abnormal. That is, if only the encoder signal can be received, a bit error can be detected by the control unit 34 on the receiving side, and abnormality determination of the signal path 25 or the absolute encoder 23 lower than the Nth bit is possible.

  Therefore, it is not necessary to provide a special arithmetic circuit for adding a bit for detecting a bit error on the bed unit 20 side which is a transmission side, and an increase in manufacturing cost can be prevented. In addition, in the case of the MRI apparatus 100, providing this special arithmetic circuit on the bed unit 20 side in the shield room 200 causes a risk of noise emission to the reception RF coil 14, and this is caused by an RF pulse or a high magnetic field. Although there is a risk of malfunction of the arithmetic circuit, such a risk cannot occur in the present embodiment.

  Further, in the present embodiment, an abnormality is detected using an encoder signal representing the rotation speed. Many of the absolute encoders 23 can measure the number of rotations up to a power of 2n from the viewpoint of easily forming a 2 nth slit pattern on a scale for measuring the number of rotations. That is, the encoder signal representing the rotation speed output from the absolute encoder 23 can take all values that can be expressed by the data bit group. Therefore, by detecting an abnormality using the encoder signal representing the rotation speed, it is possible to detect the abnormality regardless of the value of the encoder signal that is output at the time of starting the abnormality detection.

  However, the present embodiment does not prevent the abnormality from being detected using the encoder signal representing the rotation angle. Even if an encoder signal representing the rotation angle is used, an abnormality can be detected by the same method as in the present embodiment, and the same effect can be obtained. That is, in addition to the multi-rotation type, the present invention can also be applied to an absolute encoder that outputs only an encoder signal representing a rotation angle. The encoder signal representing the rotation angle can represent a group of data bits from the viewpoint that it is difficult to form a 2 n slit pattern on the scale because the resolution of the angle and the least common multiple of the scale pitch are enormous. If not taking all values and counting up to several values, the values may be initialized. Therefore, when an abnormality is detected using an encoder signal representing the rotation angle, this abnormality detection process may be performed within a range in which the Nth bit can be changed twice.

(Second Embodiment)
Next, the MRI apparatus 100 according to the second embodiment will be described. The basic structure of the MRI apparatus 100 according to the second embodiment is the same as that of the first embodiment, and detailed description thereof is omitted. In the MRI apparatus 100 according to the second embodiment, when the control unit 34 operates as the abnormality detection apparatus 342, when the signal sequence of the encoder signal indicating the rotational speed changes in one direction of increase or decrease, N If there is no change in the Nth bit before all the bits lower than the bit are changed, it is determined that there is an abnormality.

  As described above, if the signal path 25 and the absolute encoder 23 are normal, the lower bits always change at least once while the Nth bit changes twice. In other words, if the signal path 25 and the absolute encoder 23 are normal, the Nth bit changes at least once and the Nth bit is abnormal before all the bits lower than the Nth bit change. If there is no change.

  In the second embodiment, the abnormality detection device 342 detects an abnormality such as a disconnection of the absolute encoder 23 or the signal path 25 based on the difference in the output value of the encoder signal between the normal time and the abnormal time. FIG. 7 is a block diagram showing a configuration of the abnormality detection device 342.

  The abnormality detection device 342 includes an end value calculation unit 348, an end value storage unit 349, a change detection unit 350, an N-th bit storage unit 351, and an abnormality determination unit 347. This configuration is realized by the control unit 34 when the control unit 34 configured by a CPU, a ROM, and a RAM executes a program stored in the ROM.

  The end value calculation unit 348 calculates a value taken by the lower bits indicating that all the bits lower than the Nth bit have changed. For example, when the lower bit is 011, abnormality detection starts, and if the drive unit 22 is driven in a direction to increase the value of the encoder signal, the next lower bit takes a value of 010. The lower bits go through 100, 101, 111,000, 001, and all bits have changed. The end value calculation unit 348 increases or decreases the value of the lower bits at the start of abnormality detection by 1 in accordance with the increase / decrease direction, and stores the result in the end value storage unit 349 as the end value.

  The change detection unit 350 refers to the value of the Nth bit stored in the Nth bit storage unit 351 when abnormality detection starts, and detects that the Nth bit has changed. The abnormality determination unit 347 monitors whether a change in the Nth bit is detected before the encoder signal takes the end value stored in the end value storage unit 349. If no change in the Nth bit is detected as a result of monitoring, it is determined that there is an abnormality.

  FIG. 8 is a flowchart showing the operation of the abnormality detection device 342.

  First, the drive signal is output to the drive unit 22 by the drive control device 341, whereby the encoder signal is input from the absolute encoder 23 to the abnormality detection device 342 at a constant cycle (S21).

  When the encoder signal is input, the end value calculation unit 348 extracts the value indicated by the lower bits than the N bits from the encoder signal (S22). If the drive control device 341 outputs a drive signal indicating normal rotation (S23, Yes), the end value is calculated by subtracting 1 from the extracted value (S24). On the other hand, if the drive control device 341 outputs a drive signal indicating reverse rotation (S23, No), an end value is calculated by adding 1 to the extracted value (S25). When the end value is calculated, the end value calculation unit 348 stores the end value in the end value storage unit 349 (S26).

  At the same time, the change detection unit 350 extracts the value of the Nth bit from the encoder signal (S27) and stores it in the Nth bit storage unit 351 (S28).

  When the encoder signal is input again (S29), the change detection unit 350 compares the value of the Nth bit stored in the Nth bit storage unit 351 with the value of the Nth bit of the encoder signal (S30). . If the values of the Nth bit are the same as a result of the comparison (S30, Yes), the abnormality determination unit 347 extracts the value indicated by the lower bits of the Nth bit of the encoder signal (S31) and stores the end value. The value stored in the part 349 is compared (S32). As a result of the comparison, if the value indicated by the bits lower than the Nth bit is different from the end value (No in S32), the process returns to the input waiting for the encoder signal in S29.

  On the other hand, if the value of the Nth bit is different as a result of the comparison by the change detection unit 350 (S30, No), the abnormality determination unit 347 determines normal and ends the process.

  Further, the value of the Nth bit is the same by the comparison of the change detection unit 350 (S30, Yes), and the value indicated by the bits lower than the Nth bit is the same as the end value by the comparison of the abnormality determination unit 347. If there is (S32, Yes), the abnormality determination unit 347 determines that there is an abnormality in the absolute encoder 23 or the N-th signal path 25 (S33). If the abnormality determination unit 347 determines that there is an abnormality, the abnormality detection device 342 inputs a signal indicating the abnormality to the drive control device 341. When the drive control signal receives a signal indicating an abnormality, the drive control signal outputs a control signal for stopping each part of the MRI apparatus 100.

  Also in the present embodiment, if only the encoder signal can be received, the control unit 34 on the receiving side can detect a bit error, and the abnormality determination of the signal path 25 of the Nth bit or the absolute encoder 23 becomes possible.

  Therefore, it is not necessary to provide a special arithmetic circuit for adding a bit for detecting a bit error on the bed unit 20 side which is a transmission side, and an increase in manufacturing cost can be prevented. In addition, in the case of the MRI apparatus 100, providing this special arithmetic circuit on the bed unit 20 side in the shield room 200 causes a risk of noise emission to the reception RF coil 14, and this is caused by an RF pulse or a high magnetic field. Although there is a risk of malfunction of the arithmetic circuit, such a risk cannot occur in the present embodiment.

  In this embodiment as well, an abnormality can be detected by the same method as in this embodiment using an encoder signal representing the number of rotations, and the same effect is obtained.

(Third embodiment)
Next, an MRI apparatus 100 according to the third embodiment will be described. The basic structure of the MRI apparatus 100 according to the third embodiment is the same as that of the first embodiment, and detailed description thereof is omitted.

  In the MRI apparatus 100 of this embodiment, the control unit 34 analyzes the relationship between the encoder signal indicating the rotation speed and the encoder signal indicating the rotation angle as the abnormality detection apparatus 342, and detects an abnormality in the absolute encoder 23 or the signal path 25. To detect. FIG. 9 is a block diagram showing a configuration of the abnormality detection device 342.

  The abnormality detection device 342 includes a least significant bit change detection unit 352, a signal storage unit 344, a change digit detection unit 345, a change digit storage unit 346, and an abnormality determination unit 347. This configuration is realized by the control unit 34 when the control unit 34 configured by a CPU, a ROM, and a RAM executes a program stored in the ROM.

  The least significant bit change detection unit 352 detects a change in the least significant bit of the encoder signal indicating the rotation speed. When the least significant bit changes, the signal storage unit 344 stores the encoder signal. The change digit detector 345 detects a changed bit from the encoder signal indicating the rotation angle. If there is a changed bit, the changed digit information indicating the digit number of the bit is stored in the changed digit storage unit 346. When the least significant bit of the encoder signal indicating the number of rotations changes twice, the abnormality determination unit 347 refers to the change digit storage unit 346 to detect bits that are not stored in the change digit storage unit 346. When a bit that is not stored in the change digit storage unit 346 is detected after the least significant bit of the encoder signal indicating the rotation speed changes and then changes again, it is determined as abnormal.

  10 and 11 are timing charts showing the relationship between the encoder signal indicating the rotational speed and the encoder signal indicating the rotational angle input to the abnormality detection device 342. FIG. FIG. 10 shows a normal timing chart shown when there is no abnormality such as disconnection in the absolute encoder 23 or the signal path 25. FIG. 11 shows an abnormal timing chart shown when there is an abnormality such as disconnection in the absolute encoder 23 or the signal path 25.

  The absolute encoder 23 is formed so that when the rotation angle scale rotates once, the rotation speed scale rotates by a predetermined angle. Therefore, when the drive unit 22 makes one revolution, the encoder signal representing the number of revolutions is a value counted up by one.

  For example, as shown in FIG. 10, it is assumed that the absolute encoder 23 outputs an encoder signal representing a 2-bit rotational speed and an encoder signal representing a 2-bit rotational angle.

  In this absolute encoder 23, as the rotation angle becomes α degrees, 2α degrees, and 3α degrees, the encoder signal indicating the rotation angle is output with a value counted up from 00 to 01, 10, 11, one by one. If the angle is further rotated by α degrees, the scale rotates once and a value of 00 is output. Then, as the rotation angle further becomes α degrees, 2α degrees, and 3α degrees, the encoder signal indicating the rotation angle is output as a value counted up from 00 to 01, 10, 11, and 1 each. When the angle is rotated, the scale rotates twice and a value of 00 is output. During this time, the value output as the encoder signal representing the rotational speed becomes 00, 01, 10 as the rotational speed changes to 0, 1, and 2.

  When the absolute encoder 23 and the signal path 25 are normal, the rotation speed becomes the first rotation, the least significant bit of the encoder signal indicating the rotation speed changes from 0 to 1, and then the rotation speed becomes the second rotation. During the period from 1 to 0 again, all bits of the encoder signal indicating the rotation angle always change at least once.

  On the other hand, as shown in FIG. 11, for example, when the signal path 25 that outputs the second digit signal out of the signal path 25 that outputs the encoder signal indicating the rotation angle is disconnected, the second digit signal is Since the rotation level is constantly low, the least significant bit of the encoder signal indicating the rotation speed changes from 0 to 1 at the first rotation, and then the rotation speed changes from 2 to 1 again from 1 to 0. Until the change, the bit of the second digit of the encoder signal indicating the rotation angle remains 0 and never changes.

  Therefore, when the signal trains of both encoder signals change in one direction of increase or decrease, the encoder signal indicating the rotation angle is changed while the least significant bit of the encoder signal indicating the rotation speed changes twice or more. If there is a bit that never changes, an abnormality such as disconnection has occurred in the signal path 25 or the absolute encoder 23 corresponding to the bit.

  Based on the difference in the output value of the encoder signal between the normal time and the abnormal time, the abnormality detection device 342 detects an abnormality such as disconnection of the absolute encoder 23 or the signal path 25. FIG. 12 is a flowchart showing the operation of the abnormality detection device 342.

  The signal storage unit 344 of the abnormality detection device 342 stores the encoder signal of the rotation number and the rotation angle that are initially output as initial values. When the drive signal is output to the drive unit 22 by the drive control device 341, an encoder signal is input from the absolute encoder 23 to the abnormality detection device 342 at a constant cycle (S41).

  The least significant bit change detection unit 352 determines whether or not the value of the least significant bit of the encoder signal indicating the input rotation number has changed (S42). The least significant bit change detection unit 352 compares the value of the least significant bit of the encoder signal representing the rotation number stored in the signal storage unit 344 with the least significant bit of the encoder signal representing the input rotation number, If they are different, it is determined that the value has changed.

  If it is determined that the value has changed (S42, Yes), the least significant bit change detection unit 352 clears the value stored so far, and inputs the encoder signal indicating the rotation angle and the encoder signal indicating the rotation speed. Is stored in the signal storage unit 344 (S43). The encoder signal representing the rotation angle stored in the signal storage unit 344 is stored as an encoder signal when the least significant bit of the encoder signal representing the number of rotations changes for the first time.

  Then, the least significant bit change detection unit 352 determines whether the detection start point information is “1” (S44). When the detection start point information is “0” (No in S44), the least significant bit change detection unit 352 changes the detection start point information to “1” assuming that the change is first (S45). Then, the process of abnormality detection does not proceed and the process returns to the input waiting for the encoder signal in S41.

  If the encoder signal is input again (S41) and the value of the least significant bit of the encoder signal indicating the rotational speed has not changed (No in S42), the change digit detector 345 has the detection start point information “1”. (S46). If the detection start point information is “0” (No in S46), the abnormality detection has not started yet, and the process returns to the input waiting for the encoder signal in S41.

  On the other hand, if the encoder signal is input again (S41), the value of the least significant bit of the encoder signal indicating the rotational speed has not changed (S42, No), and the detection start point information is “1” (S46). , Yes), the change digit detection unit 345 compares the input encoder signal representing the rotation angle with the encoder signal representing the rotation angle stored in the signal storage unit 344 (S47). As a result of the comparison, the change digit detection unit 345 stores change digit information indicating the digit number of the bit whose value changes in the change digit storage unit 346 (S48).

  The least significant bit change detection unit 352 and the change digit detection unit 345 repeat S41 to S48 and accumulate change digit information as long as the encoder signal is input and the least significant bit of the encoder signal indicating the rotational speed does not change. I will do it.

  When the least significant bit of the encoder signal indicating the rotational speed changes again (42, Yes) and the detection start point information is “1” (S44, Yes), the abnormality determination unit 347 reads the change digit storage unit 346 from the current digit. The change digit information accumulated up to this time is read (S49), and it is determined whether there is a bit not accumulated as change digit information (S50).

  If all the change digit information exists (S50, No), the abnormality determination unit 347 determines that the signal path 25 of the encoder signal indicating the absolute encoder 23 and the rotation angle is normal, and clears the change digit storage unit 346. (S51). When the change digit storage unit 346 is cleared, the abnormality detection device 342 returns to the encoder signal input waiting process of S41 and continues the abnormality determination process.

  On the other hand, if there is no change digit information representing any bit of the encoder signal representing the rotation angle (S50, Yes), the abnormality determination unit 347 uses the absolute encoder 23 or the bit represented by the non-existing change digit information. The corresponding signal path 25 is determined to be abnormal (S52). If the abnormality determination unit 347 determines that there is an abnormality, the abnormality detection device 342 inputs a signal indicating the abnormality to the drive control device 341. When the drive control signal receives a signal indicating an abnormality, the drive control signal outputs a control signal for stopping each part of the MRI apparatus 100.

  Also in the present embodiment, if only the encoder signal can be received, the control unit 34 on the receiving side can detect a bit error, and the abnormality determination of each signal path 25 or the absolute encoder 23 that outputs the encoder signal representing the rotation angle is performed. It becomes possible.

  Therefore, it is not necessary to provide a special arithmetic circuit for adding a bit for detecting a bit error on the bed unit 20 side which is a transmission side, and an increase in manufacturing cost can be prevented. In addition, in the case of the MRI apparatus 100, providing this special arithmetic circuit on the bed unit 20 side in the shield room 200 causes a risk of noise emission to the reception RF coil 14, and this is caused by an RF pulse or a high magnetic field. Although there is a risk of malfunction of the arithmetic circuit, such a risk cannot occur in the present embodiment.

(Fourth embodiment)
Next, an MRI apparatus 100 according to the fourth embodiment will be described. The basic structure of the MRI apparatus 100 according to the fourth embodiment is the same as that of the first embodiment, and detailed description thereof is omitted.

  FIG. 13 is a diagram illustrating a detailed configuration of the bed unit 20 and the control unit 34 that controls the bed unit 20 of the MRI apparatus 100 according to the fourth embodiment.

  The bed unit 20 is provided with a pair of limit sensors 26 along the moving direction of the top plate 21. The limit sensor 26 is installed at a distance that changes at least the Nth bit of the encoder signal indicating the rotation speed or the encoder signal indicating the rotation angle in the movable range of the top plate 21. When the limit sensor 26 is separated by a distance that allows the top plate 21 to move when the drive unit 22 rotates by the maximum number of rotations that can be detected by the absolute encoder 23, the signal path of the most significant bit of the encoder signal representing the number of rotations 25 abnormalities can be detected. If the limit sensor 26 is separated by a distance that allows the top plate 21 to move when the drive unit 22 rotates once, an abnormality in the signal path 25 of the most significant bit of the encoder signal representing the rotation angle can be detected.

  In the present embodiment, in order to detect an abnormality of the Nth bit or less of the encoder signal representing the rotational speed, the limit sensor 26 is set apart by a distance at which the Nth bit of the encoder signal representing the rotational speed changes twice or more. is doing.

  The abnormality detection device 342 analyzes the encoder signal representing the rotation speed and the signal from the limit sensor 26 to detect an abnormality in the absolute encoder 23 or the signal path 25. FIG. 14 is a block diagram showing the configuration of the abnormality detection device 342. As shown in FIG.

  The abnormality detection device 342 includes a sensor value detection unit 353, a signal storage unit 344, a change digit detection unit 345, a change digit storage unit 346, and an abnormality determination unit 347. This configuration is realized by the control unit 34 when the control unit 34 configured by a CPU, a ROM, and a RAM executes a program stored in the ROM.

  The sensor value detection unit 353 detects a signal from the limit sensor 26. When a signal is output from one limit sensor 26, the input encoder signal is stored in the signal storage unit 344. The change digit detection unit 345 detects a bit in which the value of the Nth bit or less of the encoder signal has changed. When the bits below the Nth bit change, change digit information indicating the digit number of the bit is stored in the change digit storage unit 346. When the sensor value detection unit 353 detects a signal from the other limit sensor 26, the abnormality determination unit 347 refers to the change digit storage unit 346 and detects bits not stored in the change digit storage unit 346. . If a bit that is not stored in the change digit storage unit 346 is detected before signals are output from both of the pair of limit sensors 26, it is determined as abnormal.

  FIGS. 15 and 16 are timing charts showing the relationship between the encoder signal input to the abnormality detection device 342 and the signal output from the limit sensor 26. FIG. 14 shows a normal timing chart shown when there is no abnormality such as disconnection in the absolute encoder 23 or the signal path 25. FIG. 15 shows an abnormal timing chart shown when there is an abnormality such as a disconnection in the absolute encoder 23 or the signal path 25.

  Assuming that the third digit is the Nth bit, when the absolute encoder 23 and the signal path 25 are normal, the drive unit starts when one of the limit sensors 26 outputs a signal and the other limit sensor 26 outputs a signal. Since the top plate 21 is moved beyond the range in which the Nth bit changes twice or more, the numerical value for the Nth bit or less of the encoder signal indicating the rotation angle always changes once or more.

  On the other hand, as shown in FIG. 16, for example, when the signal path 25 for outputting the signal of the second digit is disconnected, the signal of the second digit is constantly at the low level. The second digit remains 0 and does not change even after the other limit sensor 26 outputs a signal.

  Therefore, the N-th bit and below are installed until both the pair of limit sensors 26 that output the detection signals that detect the arrival of the top plate 21 are separated by a distance that changes the N-th bit and output the detection signals. If there is a bit that does not change, an error such as disconnection has occurred in the signal path 25 or the absolute encoder 23 corresponding to the bit.

  Based on the difference in the output value of the encoder signal between the normal time and the abnormal time, the abnormality detection device 342 detects an abnormality such as disconnection of the absolute encoder 23 or the signal path 25. FIG. 17 is a flowchart showing the operation of the abnormality detection device 342.

  First, the sensor value detection unit 353 detects a detection signal of one limit sensor 26 (S61), and when an encoder signal is input from the absolute encoder 23 (S62), the sensor value detection unit 353 receives the input encoder. The signal is stored in the signal storage unit 344 (S63).

  After that, when the encoder signal is input (S64), the change digit detecting unit 345 receives the value of the Nth bit or less of the input encoder signal and the Nth bit stored in the signal storage unit 344. The following values are compared (S65). As a result of the comparison, the change digit detection unit 345 stores change digit information indicating the digit number of the bit whose value is changing in the change digit storage unit 346 (S66).

  Unless the detection signal is output from the other limit sensor 26 (S67, No), the sensor value detection unit 353 and the change digit detection unit 345 repeat S64 to S66 and accumulate change digit information.

  When the sensor value detection unit 353 detects the detection signal of the other limit sensor 26 (S67, Yes), the abnormality determination unit 347 reads the change digit information accumulated so far from the change digit storage unit 346 (S68), and changes. It is determined whether there are bits of the Nth bit or less that are not stored as digit information (S69).

  If all the change digit information representing the Nth bit or less is present (S69, Yes), the abnormality determination unit 347 determines that the signal path 25 corresponding to the absolute encoder 23 and the Nth bit or less is normal. The change digit storage unit 346 is cleared (S70). When the change digit storage unit 346 is cleared, the abnormality detection device 342 returns to the encoder signal input waiting process of S61 and continues the abnormality determination process.

  On the other hand, if any of the change digit information indicating the digit number of the Nth bit or less is not present (S69, No), the abnormality determination unit 347 indicates the bit represented by the absolute encoder 23 or the change digit information that does not exist. Is determined to be abnormal (S71). If the abnormality determination unit 347 determines that there is an abnormality, the abnormality detection device 342 inputs a signal indicating the abnormality to the drive control device 341. When the drive control signal receives a signal indicating an abnormality, the drive control signal outputs a control signal for stopping each part of the MRI apparatus 100.

  Also in this embodiment, if only the encoder signal and the detection signal of the limit sensor 26 can be received, the control unit 34 on the receiving side can detect a bit error, and the signal path 25 or the absolute encoder 23 in the Nth bit or less is abnormal. Judgment is possible.

  Therefore, it is not necessary to provide a special arithmetic circuit for adding a bit for detecting a bit error on the bed unit 20 side which is a transmission side, and an increase in manufacturing cost can be prevented. In addition, in the case of the MRI apparatus 100, providing this special arithmetic circuit on the bed unit 20 side in the shield room 200 causes a risk of noise emission to the reception RF coil 14, and this is caused by an RF pulse or a high magnetic field. Although there is a risk of malfunction of the arithmetic circuit, such a risk cannot occur in the present embodiment.

  Further, according to the present embodiment, the signal path 25 for outputting the encoder signal is used to determine the abnormality of any bit of the encoder signal based on the detection signal of the limit sensor 26 instead of any bit of the encoder signal. Even if an abnormality occurs in a plurality of them simultaneously, the abnormality can be detected without any problem.

  In this embodiment as well, an abnormality can be detected by the same method as in this embodiment using an encoder signal representing the number of rotations, and the same effect is obtained.

It is a figure which shows the MRI apparatus which detects abnormality of the signal wire | line output from an absolute encoder or an absolute encoder. It is a figure which shows the detailed structure of the control part which controls the bed unit and bed unit of an MRI apparatus. It is a block diagram which shows the structure of the abnormality detection apparatus which concerns on 1st Embodiment. It is a timing chart which shows the normal relationship between the bits of an encoder signal. It is a timing chart which shows the relationship between the bits of an encoder signal when abnormality arises. It is a flowchart which shows operation | movement of the abnormality detection apparatus which concerns on 1st Embodiment. It is a block diagram which shows the structure of the abnormality detection apparatus which concerns on 2nd Embodiment. It is a flowchart which shows operation | movement of the abnormality detection apparatus which concerns on 2nd Embodiment. It is a block diagram which shows the structure of the abnormality detection apparatus which concerns on 3rd Embodiment. It is a timing chart which shows the normal relationship of the encoder signal which shows a rotation speed, and the encoder signal which shows a rotation angle. It is a timing chart which shows the normal relationship of the encoder signal which shows the rotation speed, and the encoder signal which shows a rotation angle when abnormality has arisen. It is a flowchart which shows operation | movement of the abnormality detection apparatus which concerns on 3rd Embodiment. It is a figure which shows the detailed structure of the control part which controls the bed unit of the MRI apparatus which concerns on 4th Embodiment, and a bed unit. It is a block diagram which shows the structure of the abnormality detection apparatus which concerns on 4th Embodiment. It is a timing chart which shows the normal relationship between an encoder signal and the signal which a limit sensor outputs. It is a timing chart which shows the relationship between the signal which an encoder signal and a limit sensor output when abnormality has arisen. It is a flowchart which shows operation | movement of the abnormality detection apparatus which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 MRI apparatus 200 Shield room 10 Magnet stand 11 Static magnetic field magnet 12 Gradient magnetic field coil 13 Transmission RF coil 14 Reception RF coil 20 Bed unit 21 Top plate 22 Drive part 23 Absolute encoder 24a Communication unit 24b Communication interface 25 Signal path 26 Limit sensor 30 Control unit 31 Reconfiguration unit 32 Display unit 33 Input unit 34 Control unit 341 Drive control device 342 Abnormality detection device 343 Nth bit change detection unit 344 Signal storage unit 345 Change digit detection unit 346 Change digit storage unit 347 Abnormality determination unit 348 End Value calculation unit 349 End value storage unit 350 Change detection unit 351 Nth bit storage unit 352 Least significant bit change detection unit 353 Sensor value detection unit P Subject

Claims (8)

A static magnetic field generating means for generating a static magnetic field in the diagnostic space;
A gradient coil for generating a gradient magnetic field in the static magnetic field;
A top plate for inserting a subject from the entrance of the diagnostic space into the diagnostic space;
A drive unit for driving the top plate;
An absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the driving unit, or a second bit string of a plurality of digits representing the rotation speed of the driving unit in addition to the first bit string;
A control unit that receives the signal sequence from the absolute encoder via a signal path, and outputs a drive signal to the drive unit based on the signal sequence;
With
The controller is
When the value of the signal sequence changes in one direction of increase or decrease, while the Nth bit of any one of the signal sequences changes more than once, if there is no change in the lower bits, Including a determination means for determining an abnormality,
A magnetic resonance imaging apparatus. A static magnetic field generating means for generating a static magnetic field in the diagnostic space;
A gradient coil for generating a gradient magnetic field in the static magnetic field;
A top plate for inserting a subject from the entrance of the diagnostic space into the diagnostic space;
A drive unit for driving the top plate;
An absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the driving unit, or a second bit string of a plurality of digits representing the rotation speed of the driving unit in addition to the first bit string;
A control unit that receives the signal sequence from the absolute encoder via a signal path, and outputs a drive signal to the drive unit based on the signal sequence;
With
The controller is
When the value of the signal sequence changes in one direction of either increase or decrease, there must be no change in the Nth bit until all the bits lower than the Nth bit of the signal sequence change. Including a determination means for determining an abnormality,
A magnetic resonance imaging apparatus. A static magnetic field generating means for generating a static magnetic field in the diagnostic space;
A gradient coil for generating a gradient magnetic field in the static magnetic field;
A top plate for inserting a subject from the entrance of the diagnostic space into the diagnostic space;
A drive unit for driving the top plate;
An absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the driving unit and a second bit string of a plurality of digits representing the rotation speed of the driving unit as a signal string;
A control unit that receives the signal sequence from the absolute encoder via a signal path, and outputs a drive signal to the drive unit based on the signal sequence;
With
The controller is
When the value of the first and second bit strings changes in one direction of increase or decrease, the value changes to the first bit string while the least significant bit of the second bit string changes twice or more. Including a determination means for determining that there is an abnormality if there is a bit that is not
A magnetic resonance imaging apparatus. A static magnetic field generating means for generating a static magnetic field in the diagnostic space;
A gradient coil for generating a gradient magnetic field in the static magnetic field;
A top plate for inserting a subject from the entrance of the diagnostic space into the diagnostic space;
A drive unit for driving the top plate;
An absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the driving unit, or a second bit string of a plurality of digits representing the rotation speed of the driving unit in addition to the first bit string;
When the value of the signal sequence changes in one direction of increase or decrease, it detects and detects the movement of the top plate by a distance that changes at least the Nth bit of any of the signal sequences twice or more A sensor that outputs a signal;
A control unit that receives the signal sequence from the absolute encoder via a signal path, and outputs a drive signal to the drive unit based on the signal sequence;
With
The controller is
When the sensor outputs the detection signal, if there is no change in the bit lower than the Nth bit of the signal sequence, it is determined that there is an abnormality.
A magnetic resonance imaging apparatus. The absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the detection object or a second bit string of a plurality of digits representing the rotation speed of the detection object in addition to the first bit string as a signal string via the signal path A signal sequence is input,
When the value of the signal sequence changes in one direction of increase or decrease, while the Nth bit of any one of the signal sequences changes more than once, if there is no change in the lower bits, Judging it as abnormal,
An abnormality detection device characterized by the above. The absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the detection object or a second bit string of a plurality of digits representing the rotation speed of the detection object in addition to the first bit string as a signal string via the signal path A signal sequence is input,
When the value of the signal sequence changes in one direction of increase or decrease, there must be no change of the Nth bit until all the bits lower than the Nth bit of the signal sequence change. If it is judged abnormal,
An abnormality detection device characterized by the above. The absolute encoder that outputs a first bit string of a plurality of digits representing the rotation angle of the detection object or a second bit string of a plurality of digits representing the rotation speed of the detection object in addition to the first bit string as a signal string via the signal path A signal sequence is input,
When the first and second signal sequences change in one direction of increase or decrease, the least significant bit of the second bit sequence changes to the first bit sequence while the least significant bit changes twice or more. If there is a bit that is not, determine that it is abnormal.
An abnormality detection device characterized by the above. Signal path from an absolute encoder that outputs, as a signal sequence, a first digit string of multiple digits representing the rotation angle of the detection target for moving the device, or a second bit string of multiple digits representing the number of rotations of the detection target in addition to this The signal sequence is input via
When the value of the signal sequence changes in one direction of increase or decrease, a detection signal is detected by detecting movement of the device by a distance that changes at least the Nth bit of any of the signal sequences twice or more. A sensor that outputs
When the sensor outputs the detection signal, if there is no change in the bit lower than the Nth bit of the signal sequence, it is determined that there is an abnormality.
An abnormality detection device characterized by the above.

Images