CN104147711A - Method for improving leaf position detection accuracy of multi-leaf collimator - Google Patents

Abstract

The invention provides a method for improving the leaf position detection accuracy of a multi-leaf collimator. The method sequentially comprises the following steps that (a), the phase A of an incremental encoder is connected with an external interrupt interface of a single-chip microcomputer, and the phase B of the incremental encoder is connected with an I/O interface of the single-chip microcomputer; (b), when an interrupt happens, the single-chip microcomputer judges that the phase A is located on the rising edge or the falling edge when in the interrupt position and detects that a signal of the phase B is in high level or in low level at the moment; (c), if the phase A is located on the rising edge and the phase B is in low level, the single-chip microcomputer judges the forward rotation and one is added to the number of a counter; if the phase A is located on the rising edge and the phase B is in high level, the micro-chip microcomputer judges backward rotation and one is subtracted from the number of the counter; if the phase A is located on the falling edge and the phase B is in high level, the micro-chip microcomputer judges forward rotation and one is added to the number of the counter; if the phase A is located on the falling edge and the phase B is in low level, the micro-chip microcomputer judges backward rotation and one is subtracted from the number of the counter. Accumulated errors of the incremental encoder are effectively avoided in the frequent forward rotation and backward rotation process of a motor, and the leaf position detection accuracy of the multi-leaf collimator is improved.

Description

A kind of method that improves multi-diaphragm collimator leaf position accuracy of detection

Technical field

The present invention relates to medical apparatus and instruments control technology field, be specifically related to a kind of method that multi-diaphragm collimator leaf position detects.

Background technology

Multi-diaphragm collimator is a kind of advanced person's stereotaxic radiosurgery armarium, can coordinate linear accelerator or cobalt-60 machine to carry out conformal intensity modulated treatment to tumor, thereby reaching the raising radiotherapy ratio of gains (focuses on the dosage of lonizing radiation in pathological changes to greatest extent, killing off tumor cells, and normal structure around and organ are subject to less or avoid unnecessary irradiation) object.It is one of capital equipment of current oncotherapy.It is, by A, two groups of arrange in opposite directions some of B, high density tungsten alloy blade is substituted to traditional plumbous baffle plate with shielding ray, with motor driven vane and the vane group respectively of corresponding logarithm, detect and control the position of blade by control system, form fast the launched field shape requiring, the corresponding actions of combined treatment machine, reaches conformal or adjusts strong object.

Because the motion of blade has directly affected the distribution of X ray at patient's body, therefore the control of blade movement speed is required to have good acceleration and good dynamic property, require also more and more higher to leaf position control accuracy.Current, leaf position is generally to calculate by the number of rotary encoder (being generally incremental encoder) feedback pulse.Blade control system schematic diagram as shown in Figure 1.

Incremental encoder is directly to utilize photoelectricity transformation principle to export two prescription wave impulse A, B, and 90 ° of A, B two group pulse phase contrasts, by judging that the phase place of A, B phase judges forward and backward and calculates current location.Currently mainly read encoder feedback pulse by software approach.Obviously be, the key point that improves leaf position precision to the accurate counting of encoder output pulse.But in conformal intensity modulated therapeutic process, blade exists the drawback movement that advances frequently, the motor of driven vane exists forward reversal development frequently.There are serious cumulative errors in this method, affects the accurate counting of encoder output pulse.

Summary of the invention

The present invention, in order to overcome the deficiency of above technology, provides a kind of method that improves multi-diaphragm collimator leaf position accuracy of detection.

The present invention overcomes the technical scheme that its technical problem adopts:

The method of this raising multi-diaphragm collimator leaf position accuracy of detection, in turn includes the following steps:

A) A of incremental encoder is connected on mutually to the external interrupt interface of single-chip microcomputer, and down trigger mode is set is that rising edge and trailing edge interrupt, the B of incremental encoder is connected on mutually to the I/O interface of single-chip microcomputer;

B) in the time that the feedback pulse of incremental encoder output occurs to interrupt, when single-chip microcomputer judge interruption position, A is positioned at mutually rising edge or is positioned at trailing edge, by detect B phase now signal be high level or low level;

If c) A is that rising edge and B are mutually when the low level mutually, single-chip microcomputer is judged to be to be rotated in the forward, and enumerator adds 1, if A is that rising edge and B are during mutually for high level mutually, be judged to be reverse rotation, enumerator subtracts 1, if A be mutually trailing edge and B mutually when the high level, be judged to be to be rotated in the forward, enumerator adds 1, if A be mutually trailing edge and B mutually when the low level, be judged to be reverse rotation, enumerator subtracts 1.

The invention has the beneficial effects as follows: judge that by single-chip microcomputer A is mutually for rising edge or trailing edge and to B phase place high level or low level, and after being compared mutually with B, A phase judges rotating, determine again enumerator+1 still-1, therefore effectively avoid in the frequent rotating process of motor, the cumulative error of incremental encoder, has improved multi-diaphragm collimator leaf position accuracy of detection.

Brief description of the drawings

Fig. 1 is multi-leaf collimator control system schematic diagram;

Fig. 2 is encoder A, B phase waveform figure;

Fig. 3 is encoder and single-chip microcomputer syndeton schematic diagram.

Detailed description of the invention

Below in conjunction with accompanying drawing 2, the present invention will be further described for accompanying drawing 3.

At present, the position feedback of multi-diaphragm collimator blade generally adopts the feedback pulse of incremental encoder to obtain as calculated.Usual way is: in the time that A occurs rising edge mutually, if now B is low level, being forward, is reversion during for high level.Recording the number of A phase rising edge, is exactly the umber of pulse of encoder feedback.But in rotating process frequently, there are serious cumulative errors in this method.As shown in Figure 2, for " edge " of same pulse, forward is rising edge, is trailing edge, as shown in Figure 3 when reversion.Suppose that motor is in forward rotation, oscillogram is seen from left to right.If now motor stops and being parked in the place of mark I, and hypothesis step-by-step counting is now 100.After this, motor reversal, and move to mark II.Now, oscillogram should see from right to left, and trailing edge originally becomes rising edge, and count pulse will subtract 1 and become 99.And if then just forwarding mark I to from mark II, count pulse does not change, then is inverted to mark II from mark I, and count pulse will subtract 1 and become 98.So accumulation is gone down, and the cumulative errors of system constantly increase, thereby cannot correctly reflect the actual position of blade.

The method of this raising multi-diaphragm collimator leaf position accuracy of detection, in turn include the following steps: the external interrupt interface that a) A of incremental encoder is connected on mutually to single-chip microcomputer, and down trigger mode is set is that rising edge and trailing edge interrupt, the B of incremental encoder is connected on mutually to the I/O interface of single-chip microcomputer; B) in the time that the feedback pulse of incremental encoder output occurs to interrupt, when single-chip microcomputer judge interruption position, A is positioned at mutually rising edge or is positioned at trailing edge, by detect B phase now signal be high level or low level;

If c) A is that rising edge and B are mutually when the low level mutually, single-chip microcomputer is judged to be to be rotated in the forward, and enumerator adds 1, if A is that rising edge and B are during mutually for high level mutually, be judged to be reverse rotation, enumerator subtracts 1, if A be mutually trailing edge and B mutually when the high level, be judged to be to be rotated in the forward, enumerator adds 1, if A be mutually trailing edge and B mutually when the low level, be judged to be reverse rotation, enumerator subtracts 1.Judge that by single-chip microcomputer A is mutually for rising edge or trailing edge and to B phase place high level or low level, and after being compared mutually with B, A phase judges rotating, determine again enumerator+1 still-1, therefore effectively avoid in the frequent rotating process of motor, the cumulative error of incremental encoder, has improved multi-diaphragm collimator leaf position accuracy of detection.

Claims (1)

1. a method that improves multi-diaphragm collimator leaf position accuracy of detection, is characterized in that: in turn include the following steps:

A) A of incremental encoder is connected on mutually to the external interrupt interface of single-chip microcomputer, and down trigger mode is set is that rising edge and trailing edge interrupt, the B of incremental encoder is connected on mutually to the I/O interface of single-chip microcomputer;

B) in the time that the feedback pulse of incremental encoder output occurs to interrupt, when single-chip microcomputer judge interruption position, A is positioned at mutually rising edge or is positioned at trailing edge, by detect B phase now signal be high level or low level;

If c) A is that rising edge and B are mutually when the low level mutually, single-chip microcomputer is judged to be to be rotated in the forward, and enumerator adds 1, if A is that rising edge and B are during mutually for high level mutually, be judged to be reverse rotation, enumerator subtracts 1, if A be mutually trailing edge and B mutually when the high level, be judged to be to be rotated in the forward, enumerator adds 1, if A be mutually trailing edge and B mutually when the low level, be judged to be reverse rotation, enumerator subtracts 1.