JP5077270B2 - Round-trip X-ray equipment - Google Patents

Description

  The present invention relates to a power-driven X-ray imaging apparatus that moves forward or backward in response to the force of an operation handle, and more particularly, to a round-patient X-ray imaging apparatus in which a current flowing through a drive motor is limited.

  Conventionally, a roundabout X-ray imaging apparatus has a weight of 400 kg or more, and therefore a traveling motor is provided, and the roundabout X-ray imaging apparatus can be moved by driving the motor. . This motor drive is controlled by pulse width modulation control (hereinafter referred to as PWM control), and the pulse width of PWM control is controlled by the position of the operation lever handle. If the rotational speed of the motor is lower than a predetermined rotational speed for the input signal from the operation lever handle, the rotational speed of the motor is increased by widening the pulse width of the PWM control. Further, if the motor rotation speed is higher than a predetermined rotation speed for the input signal from the operation lever handle, the rotation speed of the motor is lowered by narrowing the pulse width of the PWM system. In this way, the rotational speed of the motor is controlled by the position of the operation lever handle.

  In such an X-ray apparatus for round trips, even if the same motor drive current is applied during climbing and traveling on flat ground, the load also changes if the road surface slope changes, so that it is heavy on an uphill and light on a downhill. Therefore, when climbing up, it is necessary to increase the output torque from the motor by flowing a large motor drive current. When the motor is controlled in this way, an excessive drive current flows through the motor even when starting on flat ground, and the vehicle starts suddenly. The problem that occurred.

  Therefore, in the round-ray X-ray imaging apparatus described in Patent Document 1, wheel rotational speeds and motor drive circuit outputs according to various traveling inclination angles θ are stored in advance, and average values of the respective speeds and outputs. Is compared with the ratio R of the average value of the speed and the output when actually traveling, the uphill inclination angle θ is estimated, and the uphill inclination angle θ is input to the input signal from the operation lever handle. The rotation speed of the motor is controlled by multiplying by a coefficient corresponding to.

JP 2001-309910 A

  However, in the roundabout X-ray imaging apparatus described in Patent Document 1, every time the specification of the apparatus is changed, the wheel rotation speed and the motor drive circuit output due to various traveling inclination angles θ must be measured. Rather, acquiring such data requires a great deal of effort.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide an X-ray imaging apparatus for round trips that can smoothly climb uphill and prevent sudden acceleration on flat ground. To do.

In order to achieve such an object, the present invention has the following configuration.
That is, the invention according to claim 1 is an X-ray imaging apparatus for round trips, which is a pair of wheels that are driven independently of each other, a motor that drives the wheels, and a motor drive control circuit that drives and controls the motor. Current detecting means for detecting a current value flowing through the motor, a calculation unit for calculating a limit current value that is an upper limit value of a current flowing through the motor according to a traveling state of the round-trip X-ray imaging apparatus, A limiting current determining unit that compares a limiting current value and a current value flowing through the motor, and when the limiting current determining unit determines that the current value flowing through the motor exceeds the limiting current value, the motor The drive control circuit controls the current value flowing through the motor so as not to exceed the limit current value.

  According to the said structure, the limiting current value which is the upper limit of the electric current sent to a motor according to the driving | running | working state of a roundabout X-ray imaging apparatus is calculated by a calculating part. Further, the current value flowing through the motor is detected by the current detecting means, and the current value flowing through the motor and the limited current value are compared in the limited current determining unit. When the current limit value determining unit determines that the current value flowing through the motor exceeds the limit current value, the motor drive control circuit controls so that the current value flowing through the motor does not exceed the limit current value. The current value falls within the limit current value. As a result, since no excessive current flows through the motor, an appropriate output torque can be obtained from the motor, and sudden acceleration does not occur during traveling on flat ground. Further, since the limit current value changes according to the traveling state of the round-trip X-ray imaging apparatus, the limit current value increases when a large amount of motor current is required, such as during climbing. As described above, the limit current value of the current flowing through the motor is different when traveling on a flat ground and when climbing a hill.

According to a second aspect of the present invention, in the X-ray imaging apparatus for round visits according to the first aspect, the motor drive control circuit includes a motor drive circuit for driving the motor, and a pulse width modulation control for a current flowing through the motor. A pulse width modulation control circuit that sends a pulse signal to the motor drive circuit, and when the limit current determination unit determines that the current value flowing through the motor exceeds the limit current value, the pulse width modulation control The circuit modulates the pulse width of the pulse signal to control the current value flowing through the motor so as not to exceed the limit current value.

  According to the above configuration, the pulse width modulation control circuit controls the pulse width modulation control circuit so that the current value flowing through the motor does not exceed the limit current value when the limit current determination unit determines that the current value flowing through the motor exceeds the limit current value. Since the width is modulated and controlled, the value of the current flowing through the motor immediately can be within the limit current value.

According to a third aspect of the present invention, in the X-ray imaging apparatus for round visits according to the first aspect, the motor drive control circuit pulses a motor drive circuit for driving the motor and a voltage applied to the motor drive circuit. A pulse amplitude modulation control circuit that performs amplitude modulation control, and the pulse amplitude modulation control circuit is applied to the motor when the limit current determination unit determines that the current value flowing through the motor exceeds the limit current value wherein the current flowing value to the motor voltage pulse amplitude modulation control to the to the control so as not to exceed the limited current value.

  According to the above configuration, when the current limit value determining unit determines that the current value flowing through the motor exceeds the limit current value, the pulse amplitude modulation control circuit is configured to prevent the current value flowing through the motor from exceeding the limit current value. Since the voltage supplied to the motor drive control circuit is controlled, the current value flowing through the motor can be immediately kept within the limit current value.

  According to a fourth aspect of the present invention, in the X-ray imaging apparatus for round visits according to any one of the first to third aspects, an inclination detection means for detecting an inclination state of the X-ray imaging apparatus for round visits is provided, and the calculation is performed. The unit calculates the limit current value from the tilt information detected by the tilt detection means.

  According to the above configuration, the traveling state of the round X-ray apparatus is detected by the inclination detection means. In other words, the tilt detection means detects how much the roundabout X-ray imaging apparatus is in the tilt state, and the calculation unit calculates an optimum current limit value for the tilt state. Thus, the limit current value can be changed in accordance with the inclination state. Therefore, when the hill is climbed, the output current of the motor can be increased by increasing the limit current value as compared with when traveling on a flat ground. In this way, by changing the current limit value between when climbing up and running on flat ground, it is possible to operate naturally without any sense of incompatibility when traveling on either uphill or flat ground.

  According to a fifth aspect of the present invention, in the X-ray imaging apparatus for round visits according to any one of the first to third aspects, the calculation unit sets a threshold value for the limit current value and the current flowing through the motor. A value obtained by adding a difference between the value and the threshold value to the limit current value is set as a new limit current value.

  According to the above-described configuration, the traveling state of the round-trip X-ray imaging apparatus is detected by comparing the threshold value provided for the limit current value by the calculation unit and the current value flowing through the motor. The calculation unit adds the difference between the current value flowing through the motor and the threshold value to the limit current value, and sets this as a new limit current value. As a result, the limit current value varies in accordance with the value of the current flowing through the motor. When the current value flowing through the motor tends to increase with time, such as during climbing, the limit current value increases by the difference between the current value flowing through the motor and the threshold value. Torque can be obtained. In addition, when the current value flowing through the motor does not exceed the threshold value, such as when driving on flat ground, the limited current value is reduced by the difference between the threshold value and the current value flowing through the motor, so the round-trip X-ray imaging apparatus accelerates rapidly. Can be prevented. In this way, the vehicle can be operated naturally without any discomfort when traveling either way.

  According to a sixth aspect of the present invention, in the X-ray imaging apparatus for round visits according to the fifth aspect, the calculation unit sets the threshold value by multiplying the limit current value by a predetermined coefficient. And

  According to the above configuration, the threshold value is set by multiplying the limit current value by a predetermined coefficient. Therefore, if the limit current value changes corresponding to the change in the current value flowing through the motor, the threshold value also changes. It is possible to calculate a threshold value and a limit current value that are optimal for fluctuations in the current value flowing through the.

  A seventh aspect of the present invention is the round-trip X-ray imaging apparatus according to the fifth or sixth aspect, wherein the arithmetic unit calculates a difference between the current value flowing through the motor and the threshold value as an average value for each predetermined period. Is calculated.

  According to the above configuration, since the calculation unit calculates the difference from the threshold value as an average value of the current value flowing through the motor every predetermined period, the limit current value can be prevented from changing suddenly, and the smoother Acceleration can be realized.

  According to the round-trip X-ray apparatus according to the present invention, it is possible to provide a round-trip X-ray apparatus capable of smoothly climbing even on an uphill and preventing sudden acceleration on a flat ground.

It is a side view of the X-ray imaging apparatus for round trips concerning an Example. 1 is a block diagram showing a configuration of a round-trip X-ray imaging apparatus according to Embodiment 1. FIG. 1 is a block diagram illustrating a PWM control circuit according to a first embodiment. 1 is a circuit diagram illustrating a motor drive circuit according to Embodiment 1. FIG. It is a block diagram which shows the structure of the X-ray imaging apparatus for rounds based on Example 2. FIG. FIG. 10 is an explanatory diagram showing fluctuations in the limit current value according to the second embodiment. FIG. 10 is an explanatory diagram showing fluctuations in the limit current value according to the second embodiment. It is a block diagram which shows the structure of the X-ray imaging apparatus for round trips concerning Example 3. FIG. FIG. 6 is a circuit diagram illustrating a motor drive circuit according to a third embodiment.

Embodiment 1 of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic side view of a roundabout X-ray imaging apparatus, FIG. 2 is a block diagram showing a configuration of the roundabout X-ray imaging apparatus, FIG. 3 is a block diagram showing a PWM control circuit, and FIG. It is a circuit diagram which shows a motor drive circuit.

<X-ray system for round trips>
As shown in FIGS. 1 and 2, an X-ray imaging apparatus 1 for round trips includes an X-ray tube 2 that irradiates X-rays, an arm 3 that holds the X-ray tube 2, and a carriage 4 that supports the arm 3. Provided on a handle holding base 9 attached to the carriage 4, provided with a support column 5 that can be turned up, a front wheel 5 that can turn freely, and a rear wheel 6 that cannot be steered (left rear wheel 7 and right rear wheel 8). By operating the lever handle 10 back and forth, the drive motor 11 (the left motor 12 and the right motor 13) provided in the lower portion can rotate to move forward or backward.

  The arm 3 is provided with a support mechanism and a rotation mechanism for the X-ray tube 2, and the arm 3 that expands and contracts in the horizontal direction is designed to be a mechanism that can move vertically on the support column 5 smoothly and take a balance. The collimator 14 (X-ray emission port) of the X-ray tube 2 can be peeled in all directions and spatial positions according to the imaging region.

  A pair of fixed non-steerable rear wheels 6 are provided at the rear part of the carriage 4, and are supported at the front part of the carriage 4 by a pair of casters, that is, pivotable front wheels 5. The rear wheel 6 and the drive motor 11 have independent control systems on the left and right, and the rear wheel 6 is driven independently from each other by the drive motor 11 mounted on the carriage. That is, with the front wheel 5 in front, the left rear wheel 7 on the left side of the rear wheel 6 is driven by the left motor 12, and the right rear wheel 8 on the right side of the rear wheel 6 is driven by the right motor 13.

  And the cart 4 is equipped with a high voltage transformer and a capacitor using a main circuit 100 to 120 V, 60 Hz as an internal power source by an automobile battery and an inverter. The control circuit is made into a solid system, and one-touch type devices that are automatically programmed for shooting operations are often used.

  The front wheels 5 and the rear wheels 6 are made of rubber tires and are designed so that they can freely enter and leave the hospital room, and are equipped with other brake systems, cassette boxes, and accessory devices. It is important for this round-trip X-ray imaging apparatus 1 to be small, light and easy to operate as a mobile device. In hospitals, bedrooms, technical rooms, operating rooms, children's rooms, X-ray rooms, infant rooms, elevators It can be easily moved and used for X-ray photography on site.

  The lever handle 10 is connected to the carriage 4 via a relatively rigid but flexible spring member. The two spring members connected to both sides of the carriage 4 are composed of rigid leaf springs, and by providing the spring members, the force applied to the lever handle 10 to push and pull the lever handle 10 is increased. Accordingly, the lever handle 10 can be slightly displaced in the front-rear direction. By operating the lever handle 10 back and forth, the lever handle 10 can be displaced relatively easily by the spring action of the spring member, and when the lever handle 10 is released, it returns quickly to the neutral position or the center position. Can be made.

  A pair of linear magnets that move with the lever handle 10 are attached to both ends of the lever handle 10. On the other hand, a pair of Hall effect sensors (the left pressure sensor 18 and the right pressure sensor 19) are attached to the carriage 4 and are respectively disposed adjacent to the corresponding magnets.

  When the Hall effect sensor (left pressure sensor 18, right pressure sensor 19) is in the center position with respect to the magnet, the output signal of the Hall effect sensor (left pressure sensor 18, right pressure sensor 19) becomes zero level, and the magnet Is shifted, the output signals of the Hall effect sensors (the left pressure sensor 18 and the right pressure sensor 19) change substantially linearly between the positive maximum value and the negative maximum value.

  The sign or polarity of the sensor signal represents the direction of displacement of the lever handle 10, and the magnitude of the sensor signal is proportional to the amount of displacement. In this way, the operating force applied to the lever handle 10 can be converted into an electrical signal. Further, the operation force may be detected using a pressure sensor other than the Hall sensor. The left pressure sensor 18 and the right pressure sensor 19 correspond to the operating force detection means in the present invention.

  When the operator operates the lever handle 10 of the carriage 4 back and forth, the operation force signal Ft (the left operation force signal 20 and the right operation force signal) from the left pressure sensor 18 and the right pressure sensor 19 provided at both ends of the lever handle 10. 21) is input to a CPU (Central Processing Unit) 17 independently on the left and right. On the other hand, a motor rotation speed signal is input to the CPU 17 from a left encoder 22 and a right encoder 23 which are provided on the axles of the left wheel 7 and the right wheel 8 and detect the rotation speed Vt of the left motor 12 or the right motor 13, respectively.

  In addition, an inclination signal is input from the inclination detection circuit 24 to the CPU 17 in accordance with the inclination angle of the round X-ray imaging apparatus 1. The inclination detection circuit 24 can detect whether the round-trip X-ray imaging apparatus 1 is traveling on a flat ground, up a hill, or down. As the tilt detection circuit 24, a gyroscope, a gravity sensor, or the like can be employed.

  Next, the CPU 17 calculates a duty ratio of PWM control proportional to the forward and backward operating force signals Ft (left operating force signal 20 and right operating force signal 21) from the left pressure sensor 18 and the right pressure sensor 19, The duty ratio signal is sent to the PWM control circuit 16 independently on the left and right sides. Further, the CPU 17 calculates a limit current value corresponding to the tilt angle based on the tilt signal from the tilt detection circuit 24, and sends this limit current value to the limit current determination unit 25. The CPU 17 corresponds to the calculation unit in the present invention.

  The PWM control circuit 16 generates a switching pulse signal whose duty ratio is determined based on the duty ratio signal sent from the CPU 17 and performs PWM control on the motor drive circuit 15. The PWM control circuit 16 includes a left PWM control circuit and a right PWM control circuit, both of which are the same control circuit. The left PWM control circuit sends a switching pulse signal to the left motor drive circuit, and the right PWM control circuit sends a switching pulse signal to the right motor drive circuit. In this way, PWM control switching pulse signals are sent to the motor drive circuit 15 independently on the left and right sides.

  The motor drive circuit 15 includes a left motor drive circuit and a right motor drive circuit, and both have the same circuit configuration. The left motor drive circuit controls the rotation of the left motor 12, and the right motor drive circuit controls the rotation of the right motor 13. The motor drive circuit 15 performs on / off control of the current flowing through the left motor 12 and the right motor 13 by the PWM-controlled switching pulse signal sent from the PWM control circuit 16 so that each motor rotates at the output torque T. In this way, the left motor 12 drives the left rear wheel 7 and the right motor 13 drives the right rear wheel 8 independently.

  Thus, the left encoder 22 and the right encoder 23 respectively detect the rotation speed Vt of the drive motor 11 (left motor 12 and right motor 13) rotating at the output torque T, and the motor rotation speed signal is input to the CPU 17 again. If the rotational speed Vt is lower than a predetermined rotational speed with respect to the operating force signal Ft from the lever handle 10, the PWM control pulse width is widened, and if high, the PWM control pulse width is narrowed to perform feedback control. The CPU 17 inputs a corresponding duty ratio signal to the PWM control circuit 16, the PWM control circuit 16 controls the motor drive circuit 15, and the motor drive circuit 15 controls the rotational speed V of the left motor 12 and the right motor 13. Is. Next, each component will be described in detail.

<Limit current discrimination unit>
As shown in FIGS. 2 and 3, the limit current determination unit 25 determines whether the current value flowing through the drive motor 11 sent from the motor drive circuit 15 exceeds or does not exceed the limit current value sent from the CPU 17. When the current value detected by the ammeter 33 (referred to as a motor current value) is less than or equal to the limit current value sent from the CPU 17, the limit current determination unit 25 does not operate on the PWM control circuit 16. . However, when the motor current value exceeds the limit current value sent from the CPU 17, the limit current determination unit 25 determines the duty ratio of the duty ratio signal sent from the CPU 17 to the PWM control circuit 16 by the pulse width. A duty ratio change signal that is changed to be smaller is sent to the PWM control circuit 16. What is necessary is just to set suitably how much a pulse width is made small.

<PWM control circuit>
As shown in FIG. 3, the PWM control circuit 16 sends a pulse generation circuit 26 to the pulse generation circuit 26 by a pulse generation circuit 26 that generates a pulse, a duty ratio signal sent from the CPU 17, and a duty ratio change signal sent from the limit current determination unit 25. And a duty ratio changing circuit 27 for changing the duty ratio of the generated pulses. That is, the left PWM control circuit and the right PWM control circuit are each provided with a pulse generation circuit 26 and a duty ratio changing circuit 27. When the duty ratio signal and the duty ratio change signal are sent to the duty ratio change circuit 27, a switching pulse signal having a pulse width smaller than the duty ratio by the duty ratio signal is generated. The switching pulse signal whose duty ratio has been changed by the duty ratio changing circuit 25 is sent to the motor drive circuit 15.

<Motor drive circuit>
As shown in FIG. 4, the motor driving circuit 15 includes a DC power source V that outputs a DC constant voltage and a driving motor 11 ( Left motor 12, right motor 13), ammeter 33 for detecting motor current flowing through the drive motor, an H bridge circuit composed of switching elements SW1 to SW4 such as FET transistors, and parallel to each switching element SW1 to SW4 And a switching element driving circuit 30 for turning on and off each of the switching elements SW1 to SW4.

  The switching elements SW1 and SW2 are connected in series to an energization line 31 connected at both ends to the DC power supply V, and the switching elements SW3 and SW4 are connected in series to the energization line 32 connected at both ends to the DC power supply V. It is connected to the. That is, the conducting wire 31 and the conducting wire 32 are connected in parallel to each other. In addition, the drive motor 11 and the ammeter 33 are connected in series between the switching elements SW1 and SW2 of the energization line 31 and between the switching elements SW3 and SW4 of the energization line 32.

  According to this H-type bridge circuit, when the switching element SW1 is turned on, SW2 and SW3 are turned off, and SW4 is PWM-controlled, the drive motor 11 can be driven forward. If the switching element SW3 is turned on, SW1 and SW4 are turned off, and SW2 is PWM-controlled, the drive motor 11 can be driven in reverse.

  A switching pulse signal is sent from the duty ratio changing circuit 25 in the PWM control circuit 16 to the switching element driving circuit 30 in the motor driving circuit 15. On the basis of the switching pulse signal, a driving signal is issued from the switching element driving circuit 30, and the switching elements SW1 and SW4 are on / off controlled. When the switching elements SW1 and SW4 are in the ON state, a closed circuit is formed by the DC power source V, the switching element SW1, the motor 11, and the switching element SW4, so that the driving current Ia of the motor flows and the driving motor 11 rotates forward. Then, the round-trip X-ray imaging apparatus 1 accelerates forward.

  On the other hand, when it is desired to run the round-trip X-ray imaging apparatus 1 backward, similarly, when the lever handle 10 is operated backward, a driving signal is generated from the switching element driving circuit 30 to switch the switching elements SW2 and SW3. The on state, SW1 and SW4 are turned off, the drive current in the direction opposite to the drive current Ia flows, the drive motor 11 rotates in the reverse direction, and the round trip X-ray imaging apparatus 1 moves backward.

  Next, the case of starting on flat ground will be described. When starting on flat ground, the rear wheel 6 is stopped, so the motor rotation speed signal input from the left encoder 22 and the right encoder 23 to the CPU 17 is at a zero level. Since the difference between the operating force signal Ft from the lever handle 10 and the motor rotation speed signal is larger than this, the CPU 17 calculates a duty ratio having a large pulse width and sends the duty ratio signal to the PWM control circuit 16. In addition, the inclination signal input from the inclination detection circuit 24 to the CPU 17 is zero level because it is flat, and the limit current value based on this input signal is sent to the limit current determination unit 25.

  The PWM control circuit 16 changes the duty ratio of the generated pulse based on the duty ratio calculated by the CPU 17 and sends a switching pulse signal with the changed duty ratio to the motor drive circuit 15. In the motor drive circuit 15, the switching element is on / off controlled based on the sent switching pulse signal, and the motor drive current Ia flows. When the motor drive current Ia flows, the current value flowing through the drive motor 11 is immediately detected by the ammeter 33, and the detected motor current value is sent to the limit current determination unit 25.

  The limit current determination unit 25 compares the sent motor current value with the limit current value. When it is determined that the motor current value exceeds the limit current value, a duty ratio change signal is sent to the PWM control circuit 16. In the PWM control circuit 16, when the duty ratio change signal is sent from the limiting current determination unit 25, the switching pulse signal whose duty ratio is changed so that the pulse width becomes smaller than the duty ratio based on the duty ratio signal sent from the CPU 17 is generated. It is sent to the motor drive circuit 15.

  As described above, when starting on a flat ground, the motor drive current exceeding the limit current value flows to the drive motor 11 for an instant, but the current below the limit current value is immediately changed to flow to the drive motor 11. The start is made with the prevention of excessive output torque, and no rapid acceleration is made, so the operator can start the X-ray imaging apparatus for round trips with peace of mind.

  Next, a case where the round trip X-ray imaging apparatus 1 travels uphill will be described. In this case, the inclination detection circuit 24 detects an uphill and sends an inclination signal indicating the uphill to the CPU 17. The CPU 17 calculates a limit current value according to the tilt angle detected from the sent tilt signal. The calculated limit current value is sent to the limit current determination unit 25. That is, the limit current value is larger on the uphill than on the flat ground. As a result, a larger drive current Ia can be supplied to the motor drive circuit 15 than when traveling on flat ground, so that the output torque T of the drive motor 11 is greater than when traveling on flat ground, and the motor drive circuit 15 can comfortably climb uphill. Can drive.

  Further, when the round-trip X-ray imaging apparatus 1 travels on a downhill, the inclination detection circuit 24 detects a downhill and sends an inclination signal indicating the downhill to the CPU 17. The CPU 17 calculates a limit current value according to the tilt angle detected by the sent tilt signal. The calculated limit current value is sent to the limit current determination unit 25. That is, the current limit value is smaller on the downhill than on the flat ground. As a result, only a drive current Ia smaller than that when traveling on flat ground can be supplied to the motor drive circuit 15, so that the output torque T of the drive motor 11 can be suppressed compared to when traveling on flat ground, and the motor drive circuit 15 can be inadvertently lowered. You can drive downhill with peace of mind because there is no sudden acceleration on the hill.

  Thus, according to the round-trip X-ray apparatus of Example 1, since the limiting current value is large when climbing, a large driving current Ia can be supplied to the driving motor 11, and the output torque T of the driving motor 11 is increased. can do. On the other hand, since the limit current value is small when traveling on a flat ground or downhill, a large drive current Ia cannot be supplied to the drive motor 11, and an excessive torque can be prevented from being generated in the drive motor 11. As a result, smooth acceleration can be achieved when climbing, and it is easy for the operator to travel when traveling on a flat ground or downhill because rapid acceleration is not performed. Further, since the current limit value can be changed depending on the inclination angle, the same traveling performance can be obtained regardless of the magnitude of the inclination.

Next, Embodiment 2 of the present invention will be described with reference to the drawings.
FIG. 5 is a block diagram showing the configuration of the round-trip X-ray imaging apparatus, and FIGS. 6 and 7 are explanatory diagrams showing fluctuations in the limit current value. The same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the first embodiment and the second embodiment is that, in the first embodiment, the limit current value is determined by the inclination angle of the road surface. In the second embodiment, a threshold value is provided for the limit current value. The limiting current value is determined from the relationship between Details will be described below.

Unlike the first embodiment, the round trip X-ray imaging apparatus 41 according to the second embodiment does not include an inclination detection circuit as shown in FIG. The motor current value detected by the ammeter 33 of the motor drive circuit 15 is also sent to the CPU 42. The CPU 42 calculates a threshold value Ct ₁ smaller than the limited current value CL (t ₁ ) at time t ₁ using the coefficient α as shown in the following equation.

Ct ₁ = CL (t ₁ ) × α, (0 <α <1) (1)

Further, the limit current value CL (t ₂ ) at the next time (t ₂ ) is added to the limit current value CL (t ₁ ) at time t _{1 by} the difference between the detected motor current value Cd and the threshold value Ct _1. Therefore, the following formula is established.

CL (t ₂ ) = CL (t ₁ ) + (Cd−Ct ₁ ) (2)

Further, the threshold value Ct ₂ at the next time (t ₂ ) is set to a value obtained by adding a value obtained by multiplying the difference between the motor current value Cd and the threshold value Ct ₁ by the coefficient α to the threshold value Ct ₁ at time t ₁ . The following formula holds.

Ct ₂ = Ct ₁ + α × (Cd−Ct ₁ ) (3)

  The expression (3) is also calculated from the expressions (1) and (2).

  The motor current value Cd in the equations (2) and (3) is the average value of the motor current values detected by the ammeter 33 during the time T. This is equivalent to a certain time interval between the time when the current exceeding the threshold flows and the time when the limit current value is changed. Thereby, it is possible to prevent the limit current value from changing abruptly. The CPU 42 also calculates an average value of the motor current value sent from the motor drive circuit 15 during the time T. The average value during this time T may be calculated as a moving average value.

The CPU 42 sends the limit current value obtained by the expression (2) to the limit current determination unit 43, and the limit current determination unit 43 compares the limit current value CL (t ₂ ) with the motor current value to determine the motor current. When the value exceeds the limit current value, a duty ratio change signal is sent to the PWM control circuit 16.

According to the configuration of the second embodiment, as shown in FIG. 6A, when the motor current value tends to increase such as when climbing, the motor current value Cd and the threshold value Ct ₁ that are moving averaged during the time interval T are The difference ΔCL (= Cd−Ct ₁ ) is added to the limit current value at time t ₁ as shown in FIG. 6B. Further, only α × ΔCL is added to the threshold at time t ₁ . When the motor current value like time uphill tends to increase, the motor current value exceeds the threshold, Cd> Ct _1, and the sign of the ΔCL becomes positive. As a result, the upper limit of the limit current value is raised, so that the drive current Ia can further flow through the drive motor 11 (the left motor 12 and the right motor 13), and the output torque of the drive motor 11 can be increased.

In addition, as shown in FIG. 7A, when the motor current value tends to decrease, such as when traveling on a flat ground after climbing uphill, or when descending, the motor averaged during the time interval T The difference ΔCL (= Cd−Ct ₁ ) corresponding to the difference between the current value Cd and the threshold value Ct ₁ is added to the limit current value as shown in FIG. 7B. Further, only α × ΔCL is added to the threshold at time t ₁ . When the motor current value tends to decrease, Cd <Ct _{1 and} ΔCL has a minus sign. Thus, since the upper limit of the limit current value is lowered, the drive current Ia that can be passed to the drive motor 11 is further limited, and sudden acceleration can be prevented.

  As described above, even when the limit current value is changed in accordance with the motor current value instead of the inclination detection circuit, it is possible to smoothly travel on the uphill. Further, according to the method of calculating the limit current value according to the second embodiment, even when the uphill traveling is finished and the drive current Ia flowing through the drive motor 11 is reduced, the limit current value is reduced accordingly. As a result, there is no sudden acceleration even when traveling on a flat ground or downhill at the end of climbing. In addition, a large current flows as an inrush current immediately after the start of acceleration even when traveling on flat ground or downhill, but since the limit current value is calculated using the motor current value as the moving average value, it is possible to suppress a rapid change in the limit current value. it can. Thus, since the drive current Ia flowing through the drive motor 11 does not change abruptly, a sudden acceleration of the round trip X-ray apparatus 41 can be prevented.

Next, Embodiment 3 of the present invention will be described with reference to the drawings.
FIG. 8 is a block diagram showing the configuration of a round-trip X-ray imaging apparatus, and FIG. 9 is a circuit diagram showing a motor drive circuit. The same members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The difference between the first embodiment and the third embodiment is that, in the first embodiment, the current flowing through the drive motor 11 is PWM-controlled. In the third embodiment, a DC power source V that supplies a constant DC voltage to the drive motor 11 is used. In this configuration, the current flowing through the drive motor 11 is controlled by performing pulse amplitude modulation control (hereinafter referred to as PAM control). Components different from the first embodiment will be described below.

  The CPU 52 provided in the round-trip X-ray imaging apparatus 51 is a PAM proportional to the forward and backward operating force signals Ft (the left operating force signal 20 and the right operating force signal 21) from the left pressure sensor 18 and the right pressure sensor 19. The control amplitude is calculated, and the PAM amplitude signal is sent to the PAM control circuit 54 independently on the left and right. Further, the CPU 52 calculates a limit current value corresponding to the tilt angle based on the tilt signal from the tilt detection circuit 24, and sends this limit current value to the limit current determination unit 53. The CPU 52 corresponds to the calculation unit in the present invention.

  The PAM control circuit 54 determines the voltage value to be supplied from the DC power supply V to the motor drive circuit 55 based on the PAM amplitude signal sent from the CPU 52, and performs PAM control on the motor drive circuit 55. The PAM control circuit 54 includes a left PAM control circuit and a right PAM control circuit, both of which are the same control circuit. The left PAM control circuit supplies the PAM-controlled voltage to the left motor drive circuit, and the right PAM control circuit supplies the PAM-controlled voltage to the right motor drive circuit. In this way, the PAM-controlled voltage is sent to the motor drive circuit 55 independently on the left and right sides.

  The motor drive circuit 55 includes a left motor drive circuit and a right motor drive circuit, and both have the same circuit configuration. The motor drive circuit 55 controls the current flowing in the left motor 12 and the right motor 13 by the PAM-controlled voltage sent from the PAM control circuit 54, so that each motor rotates with the output torque T.

  Thus, the left encoder 22 and the right encoder 23 respectively detect the rotation speed Vt of the drive motor 11 (left motor 12 and right motor 13) rotating at the output torque T, and the motor rotation speed signal is input to the CPU 52 again. If the rotational speed Vt is lower than a predetermined rotational speed with respect to the operation force signal Ft from the lever handle 10, the amplitude of the PAM control is increased to increase the voltage value supplied to the motor drive circuit 55, and if higher, the amplitude of the PAM control. The feedback control is performed to reduce the voltage value supplied to the motor drive circuit 55 by narrowing. The CPU 52 inputs a corresponding PAM amplitude signal to the PAM control circuit 54, the PAM control circuit 54 controls the motor drive circuit 55, and the motor drive circuit 55 controls the rotational speed V of the left motor 12 and the right motor 13. To do.

  As shown in FIGS. 8 and 9, the limit current determination unit 53 determines whether the current value flowing through the drive motor 11 sent from the motor drive circuit 55 exceeds or does not exceed the limit current value sent from the CPU 52. When the motor current value is equal to or less than the limit current value sent from the CPU 52, the limit current determination unit 53 does not operate on the PAM control circuit 54. However, when the motor current value exceeds the limit current value sent from the CPU 52, the limit current determination unit 53 changes the PAM control circuit 54 so that the amplitude of the PAM control sent from the CPU 52 becomes small. The PAM amplitude change signal to be sent is sent to the PAM control circuit 54. What is necessary is just to set suitably how much amplitude is made small.

  As shown in FIG. 9, the motor drive circuit 55 includes a drive motor 11 that causes the apparatus to run by supplied current, an ammeter 33 that detects a motor current flowing through the drive motor, and switching elements SW1 to SW4 such as FET transistors. H diode circuit, diodes D1 to D4 connected in parallel to the switching elements SW1 to SW4, and a switching element drive circuit 56 for turning on and off the switching elements SW1 to SW4.

  The switching elements SW1 and SW2 are connected in series to a conducting line 31 connected at both ends to the PAM control circuit 54, and the switching elements SW3 and SW4 are connected to the conducting line 32 connected at both ends to the PAM control circuit 54. Connected in series.

  According to this H-type bridge circuit, if the switching elements SW1 and SW4 are turned on and SW2 and SW3 are turned off and PAM control is performed, the drive motor 11 can be driven forward. If the PAM control is performed with the switching elements SW3 and SW2 in the on state and SW1 and SW4 in the off state, the drive motor 11 can be driven in reverse.

  A switching signal is sent from the CPU 52 to the switching element drive circuit 56 in the motor drive circuit 55 as the lever handle 10 moves forward or backward. Based on this switching signal, a driving signal is issued from the switching element driving circuit 56, and the switching elements SW1 and SW4 are turned on / off. When the switching elements SW1 and SW4 are in the ON state, a closed circuit is formed by the PAM control circuit 54, the switching element SW1, the motor 11, and the switching element SW4, so that the driving current Ia of the motor flows and the driving motor 11 is positive. The X-ray imaging apparatus 1 for round trips accelerates in the forward direction.

  On the other hand, when it is desired to run the round-trip X-ray imaging apparatus 1 backward, similarly, when the lever handle 10 is operated backward, a driving signal is generated from the switching element driving circuit 56 and the switching elements SW2 and SW3 are switched. The on state, SW1 and SW4 are turned off, the drive current in the direction opposite to the drive current Ia flows, the drive motor 11 rotates in the reverse direction, and the round trip X-ray imaging apparatus 1 moves backward.

  Next, the case of starting on flat ground will be described. When starting on flat ground, the difference between the operation force signal Ft from the lever handle 10 and the motor rotation speed signal is large, so the CPU 52 calculates a large amplitude for PAM control and sends the PAM amplitude signal to the PAM control circuit 54. In addition, the inclination signal input from the inclination detection circuit 24 to the CPU 52 is zero level because it is a flat ground, and the limiting current value based on this input signal is sent to the limiting current determination unit 53.

  The PAM control circuit 54 performs PAM control on the voltage supplied from the DC power supply V based on the amplitude of the PAM control calculated by the CPU 52 to control the supply voltage to the motor drive circuit 55. In the motor driving circuit 55, a motor driving current Ia flows by supplying a voltage under PAM control. As soon as the motor drive current Ia flows, the current value flowing through the drive motor 11 is detected by the ammeter 33, and the detected motor current value is sent to the limited current determination unit 53.

  The limit current determination unit 53 compares the sent motor current value with the limit current value. When it is determined that the motor current value exceeds the limit current value, a PAM amplitude change signal is sent to the PAM control circuit 54. In the PAM control circuit 54, when the PAM amplitude change signal is sent from the limited current determination unit 53, the voltage whose pulse amplitude has been changed to be smaller than the pulse amplitude based on the PAM amplitude signal sent from the CPU 52 is supplied to the motor drive circuit 55. Sent.

  As described above, when starting on a flat ground, the motor drive current exceeding the limit current value flows to the drive motor 11 for an instant, but the current below the limit current value is immediately changed to flow to the drive motor 11. The start is made with the prevention of excessive output torque, and no rapid acceleration is made, so the operator can start the X-ray imaging apparatus for round trips with peace of mind.

  Next, a case where the round trip X-ray imaging apparatus 51 travels uphill will be described. In this case, the inclination detection circuit 24 detects an uphill and sends an inclination signal indicating the uphill to the CPU 52. The CPU 52 calculates a limit current value according to the tilt angle detected from the sent tilt signal. The calculated limit current value is sent to the limit current determination unit 53. That is, the limit current value is larger on the uphill than on the flat ground. As a result, a larger drive current Ia can be supplied to the motor drive circuit 55 than when traveling on flat ground, so that the output torque T of the drive motor 11 becomes larger than when traveling on flat ground, and the motor drive circuit 55 can comfortably climb uphill. Can drive.

  In addition, when the round-trip X-ray imaging apparatus 51 travels on a downhill, the inclination detection circuit 24 detects a downhill and sends an inclination signal indicating the downhill to the CPU 52. The CPU 52 calculates a limit current value according to the tilt angle detected by the sent tilt signal. The calculated limit current value is sent to the limit current determination unit 53. That is, the current limit value is smaller on the downhill than on the flat ground. As a result, only a drive current Ia smaller than that when traveling on flat ground can be supplied to the motor drive circuit 55, so that the output torque T of the drive motor 11 can be suppressed compared to when traveling on flat ground, and the motor drive circuit 55 can be inadvertently lowered. You can drive downhill with peace of mind because there is no sudden acceleration on the hill.

  As described above, according to the round-trip X-ray apparatus of Example 3, since the limiting current value is large when climbing, a large driving current Ia can be supplied to the driving motor 11, and the output torque T of the driving motor 11 is increased. can do. On the other hand, since the limit current value is small when traveling on a flat ground or downhill, a large drive current Ia cannot be supplied to the drive motor 11, and an excessive torque can be prevented from being generated in the drive motor 11. As a result, smooth acceleration can be achieved when climbing, and it is easy for the operator to travel when traveling on a flat ground or downhill because rapid acceleration is not performed. Further, since the current limit value can be changed depending on the inclination angle, the same traveling performance can be obtained regardless of the magnitude of the inclination.

  In the third embodiment, the limit current value is calculated based on the inclination angle of the road surface. A threshold value is provided for the limit current value as in the second embodiment, and the limit current value is calculated from the relationship between the threshold value and the motor current value. May be configured to calculate.

  The present invention is not limited to the above embodiment, and can be modified as follows.

  (1) In the above-described embodiment, when the motor current value exceeding the limit current value is detected in the limit current determination unit 25, the duty ratio change signal is sent to the PWM control circuit 16 and the duty sent from the CPUs 17 and 42. A switching pulse signal with a duty ratio that is smaller than the pulse width of the duty ratio based on the ratio signal is sent from the PWM control circuit 16 to the motor drive circuit 15. Instead of controlling in this way, the control may be such that the pulse width is changed to zero by the duty ratio change signal and transmission of the switching pulse signal is stopped.

  Even if the motor drive current Ia does not flow through the drive motor 11, the drive motor 11 rotates inertially, so that the round trip X-ray imaging apparatus travels inertially. Further, when the limit current determination units 25 and 43 determine that the motor current value becomes zero and falls below the limit current value, transmission of the switching pulse signal having the duty ratio based on the duty ratio signal is resumed. A motor drive current Ia flows. By controlling in this way, sudden acceleration can be prevented when traveling on flat ground or traveling downhill.

  (2) In the above-described embodiment, an ammeter is used as a means for detecting the value of the current flowing through the motor. However, the present invention is not limited to this, and it may be detected as a current detection circuit. As a result, the value of the current flowing through the drive motor 11 can be detected with higher accuracy, so that accurate motor control can be performed.

  (3) In the above-described embodiment, the on / off control of the switching element is performed by performing the PWM control. However, the present invention is not limited to this, and pulse number modulation control (hereinafter referred to as PNM control). ), The switching element may be turned on / off.

  (4) In the embodiment described above, the current flowing through the drive motor 11 is controlled by performing PWM control, PNM control, or PAM control. However, the present invention is not limited to this, and PWM control, PNM control, and PAM are controlled. You may control the electric current which flows into the drive motor 11 using 2 or more of control together. By properly using PWM control, PNM control, and PAM control depending on the rotation speed of the drive motor 11, the drive motor 11 can be efficiently driven and controlled.

DESCRIPTION OF SYMBOLS 1,51 ... X-ray imaging apparatus for rounds 6 ... Rear wheel 7 ... Left rear wheel 8 ... Right rear wheel 11 ... Drive motor 12 ... Left motor 13 ... Right motor 14, 55 ... Motor drive circuit 15 ... PWM control circuit 16, 52 ... CPU
DESCRIPTION OF SYMBOLS 17 ... Right pressure sensor 18 ... Left pressure sensor 21 ... Left encoder 22 ... Right encoder 24 ... Inclination detection means 25, 53 ... Limiting current discrimination | determination part 33 ... Ammeter 54 ... PAM control circuit

Claims (7)

A round-trip X-ray apparatus,
A pair of wheels driven independently of each other;
A motor for driving the wheel;
A motor drive control circuit for driving and controlling the motor;
Current detection means for detecting a current value flowing through the motor;
A calculation unit that calculates a limit current value that is an upper limit value of a current that flows to the motor according to a traveling state of the round-trip X-ray imaging apparatus;
A limiting current determination unit that compares the limiting current value and a current value flowing through the motor;
When the current limit value determining unit determines that the current value flowing through the motor exceeds the current limit value,
The motor drive control circuit performs control so that a current value flowing through the motor does not exceed the limit current value. The round X-ray imaging apparatus according to claim 1,
The motor drive control circuit is
A motor drive circuit for driving the motor;
A pulse width modulation control circuit that sends a pulse signal for pulse width modulation control of the current flowing through the motor to the motor drive circuit;
When the current limit value determination unit determines that the current value flowing through the motor exceeds the current limit current value, the pulse width modulation control circuit modulates the pulse width of the pulse signal to determine the current value flowing through the motor. Control is performed so as not to exceed the limit current value. The round X-ray imaging apparatus according to claim 1,
The motor drive control circuit is
A motor drive circuit for driving the motor;
A pulse amplitude modulation control circuit that performs pulse amplitude modulation control on the voltage applied to the motor drive circuit;
When the current limit value discriminating unit determines that the current value flowing through the motor exceeds the current limit value, the pulse amplitude modulation control circuit controls the voltage applied to the motor through pulse amplitude modulation control and flows to the motor . A round trip X-ray imaging apparatus, wherein the current value is controlled so as not to exceed the limit current value. In the X-ray imaging apparatus for rounds according to any one of claims 1 to 3,
Inclination detecting means for detecting the inclination state of the round X-ray imaging apparatus,
The operation unit calculates the limit current value from the inclination information detected by the inclination detection means. In the X-ray imaging apparatus for rounds according to any one of claims 1 to 3,
The calculation unit sets a threshold value for the limit current value,
A roundabout X-ray imaging apparatus characterized by adding a difference between the current value flowing through the motor and the threshold value to the limit current value as a new limit current value. In the X-ray imaging apparatus for round visits according to claim 5,
The operation unit sets the threshold value by multiplying the limited current value by a predetermined coefficient. The round X-ray imaging apparatus according to claim 5 or 6,
The arithmetic unit calculates a difference from the threshold value as a value obtained by averaging current values flowing through the motor every predetermined period.

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