JPS59156329A - Control apparatus in radiation tomography apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a force control device used in an apparatus for photographing arbitrary tomography of a subject by linearly or circularly moving a radiation pulse source.

[Technical background of the invention and its problems]

For controlling the drive of the X-tube in a radiation (for example, X-ray) tomography device, a servo bank based on so-called classical control has not been used. This will be explained with reference to FIGS. 1 and 2.

In order to obtain the speed characteristic curve as shown in FIG. 1, it is sufficient to operate the panel selection section 1 shown in FIG. 2 to give the signal generation process section 2 the slope α, the brake start time tB, and the maximum speed υmax f.

Then, the signal from the servo bank 6 drives the DC motor.
4 and speed detection section.

All feedback from the position detection unit 6 is performed for control.In the event of a failure, an integral circuit consisting of an operational amplifier integrates α and obtains a straight line V=αtf.Next, regarding the brake start time tB, the X-ray tube at that time is determined. After calculating the position, the acceleration (-α) is integrated and decelerated at the time of position detection.

In a servo bank based on such classical control, the dynamic characteristics of the motor are expressed by differential equations, and by displaying the transfer function, the position of the poles and characteristics can be known, and the output can also be determined by convolution. but,
It is difficult to evaluate the control performance, and this is more noticeable in the optimal tracking problem than in the constant value control problem. It is necessary to find feedback of the input u, f x that makes ΔJ O (optimal control theory), but it is difficult to calculate this using classical control theory, and it is difficult to calculate this using classical control theory. Uncontrollable 2 Observation in an unconventional state?There is a problem that there is a risk of overlooking the object.Especially on the way to the end of the movement, this problem causes the X-ray tube to shake and prevent accurate tomographic images. It was supposed to be 1.

[Purpose of the invention]

The present invention has been made in consideration of the above circumstances.

It is an object of the present invention to provide a control device for a radiation tomography apparatus that can obtain accurate tomographic images by optimally controlling the movement of a radiation source.

[Overview of the invention]

In order to achieve the above object, the present invention is characterized in that the optimal tracking problem is analyzed by a computer, and the gain of the drive system is adjusted based on the analysis result.

[Embodiments of the invention]

The present invention will be specifically described below with reference to embodiments. FIG. 6 is a block diagram showing an embodiment of the present invention.

This device is, for example, a drive control circuit for an X-ray tube in a tilting tomography device, and 11 is an interactive type that inputs data such as the slope α of the speed characteristic, the brake start time tS p, the maximum speed v max, or the tilting angle. data input device,
12 is a signal generating means for generating a speed setting signal based on set input data, and supplies the speed setting signal to the DC motor 16. Reference numeral 14 denotes a position detection means consisting of a potentiometer or the like, which outputs a position detection signal (motor phase) x1i. 15 is a speed detection means consisting of a tachometer, etc., and a detection signal (rotational speed of the motor) x
Output zt. Reference numeral 16 denotes a computer serving as calculation means, which performs optimal control calculations based on the input data and outputs the calculation results via the 1)/A converter 17. 18
is a feedback gain generating means, based on the speed detection signal x2 and the output of the D/A converter 17, so that the successive detection signal di follows the successive setting signal or minimizes the error amount. The feedback gain is calculated and the calculation result (feedback input) is supplied to one side input of the wf momo.

In such a control circuit, all speed setting signals are generated based on the data from the data input device 11 for the motor 9th shift, and this? It is supplied to the + side input of the motor 16 to fully drive the motor 16, and the motor position detection signal x1. The speed detection signal 5Czk is fed back to the input of the motor 16 via the feedback gain generation means 18. Regarding gain adjustment, the computer 16 analyzes the entire optimal control (tracking) problem off-line, and the results are sent to the feedback gain generation means 1.
8, and the gain is adjusted using this input. Here, if the change in resistance value on the trajectory of the xH tube is minute and the tilting angle is constant, followability is good and stability is guaranteed to produce sound.

Next, an example of analysis of the optimal tracking problem by the computer 16 and an example of calculation of the feedback gain by the feedback gain generating means 18 in the apparatus will be described in detail.

Feedback input payments are generated from state X.

This state m a: k x = (:, ”) is defined.

This can be expressed as follows.

For example, if the speed setting signal is expressed by curve E in Figure 4, the feedback human power 1L1 that follows the speed detection signal F or setting signal E is required. In order to improve followability, a computer solves the optimal feedback gain as a hitch problem, and adjusts the gain to generate feedback manually. In this case, the resistance value on the orbit of the X-ray tube will differ depending on the orbit and the angle of the angle, but the value can be found by inputting the tilting angle and orbit into a computer using the resistance as a parameter.

The analysis of the optimal trunking problem executed by the computer 16 is described, for example, in Masami Ito's "System Control Theory" Vol. 8.
With reference to the known calculation examples shown in chapters P309 to P614, proceed as follows.

However, A is rLx constant matrix, B is r×P constant matrix, C
is an rx constant matrix.

ti−” t≦tf, the target number γ(t
) is specified and it depends on 1 (fl such that the output y (t) operates close to γ (t) with little control energy
Let's think about the problem of designing the flJ system. However, r(t
) is the same as y(t), and r(t) and y(
t) as e(t) −r(t) −y(t) ・
...... (3).

The evaluation function J is given by the following equation.

However, R, Q, and M are symmetrical and positive matrices.

The Hamiltonian H is... (5) Therefore, the U that minimizes H is obtained as U = -7B'P""" (force.However, the equation for the adjoint variable becomes, The terminal condition for the adjoint variable is −C′Mr(tf) − (9) from the condition of transversality.

From each of the above equations, uf: is expressed as a function of x. Solve this calculation on a computer and store the results.

Next, an example of calculation for determining the feedback human forces u and f will be explained.The value of the resistance tLo applied to the ODC motor is determined by the tilting angle and trajectory selection. If we set up a mathematical model with the motor phase as xl and the angular velocity as -Zz, here, y=c
xy is a value of 11j, which in this example is x2.

C=(0,1), I is the inertia rate of the motor, and α and b are constants. Inertial load is proportional to speed.

e (t)−ν(t) −z2(t) ・・・・・・
・ α2 However, 0≦t≦tl.

The evaluation interval and number are set, the control energy is set to the maximum, and the evaluation is made so as to follow the set speed signal. Therefore, J (min) (t) is calculated.

H-Yu(Zl(+Ri-,z2(t)2+a2)+PI
Z22 α 1 10Pz (fz+7cbv+hw-u,o)) −=
(14)... (16) From v (tf) = D, P2(,tf) = -v(tf) + x2ctf)
= ``2 Ctf) -... (is If you put all this together in the form of a matrix, then P(tf) = Fu(tf-6) Pz(t) 1'1
2(tf-t) a2(t)-t2ctf) = Fz
l(tf-t)P2(t) 10F22(t,7'-6)
``2('). However, Vri is a scalar Q~, (2ri, (c), so P2(t) = (Fl t(tf-t) - dreamzsCt
f-t)) -1Fzz(tJ'-6)-F+z(tf
-6) $2(t)... (c) 'Qri(tf-t) can be obtained by finding gD(tf-t). In general, J is a state transition matrix, and the solution is obtained from the above-mentioned reference, "System Control Theory" written by Masami Ito. tf-6))-
"(Fzz(tf=)-Ftz(tf-6))"z(-
g1z(tf-r)) tLτ
(26) Now U can be expressed as a function of town.

u= −F(t) ”z(+')+g(t)
”7.(27) The processing procedure using such a calculation example is explained in the fifth section.
In Figure 04, which will be explained with reference to the figure, tL6 is the resistance, I
o is a current source, 12' is a D/A converter in the signal generating means,
16' is the central processing unit rt in the computer (cpv
> is.

(α) First, calculate the (2υ formula) by hand from the 0 matrix.

(b) −u(t)=F(t)−T2(′)−! 1(t
), F(t), yct>k is calculated by hand (determined as a function of t).

(c) FCO when t = Q) ,! Find 1(0) (by computer) Find F(J) and y(1) using 0 @) 1 = 1+Δ.

(e) After that, increase every t'fcΔ, FCl), y(
t) fI: Obtain〇′). ≦72,.

〔Effect of the invention〕

According to the present invention described in detail above, it is possible to provide a device that can control the W motor more precisely than conventional devices and has excellent followability. Therefore, since the X-ray tube can be moved from point A to point B shown in FIG. 4 in the shortest possible time, it is possible to provide a radiation tomography apparatus that can reduce the exposure dose and provide high-quality images. can.

-4. Brief description of the drawings Fig. 1 is a control characteristic diagram of the motor, Fig. 2 is a block diagram showing an example of a conventional control circuit, Fig. 6 is a block diagram of an embodiment of the circuit of the present invention, and Fig. 4 is a block diagram showing an example of a conventional control circuit. Figure 111 is a characteristic diagram for explaining the operation of the present invention, and Figure 5 shows the main parts of the present invention. FIG. 3 is a block diagram used to read out the example in ≧.

11...Data input device, 12...Signal generation means, 1ro...Motor, 14...Position detection means, 1
5... Speed detection means, 16... Funputer,
17...D/A converter, 18...Feedback gain generation means.

Claims (1)

[Claims] In an apparatus for obtaining a tomographic image of an arbitrary cross section of a subject by moving a radiation source, an input device for inputting data regarding a slope α of a speed characteristic curve of a motor driving the radiation source, a maximum speed vmax, and a brake start time tB; , a signal generating means for generating all speed setting signals based on data from an input device, a speed detecting means for detecting the speed of the motor, a computer for performing optimum control calculations, an output of the computer and an output of the speed detecting means. and a feedback gain generating means that calculates a feedback gain such that the speed detection signal follows the speed setting signal and generates a feedback signal wf to be supplied to the motor. Device.