CN114545228B - OCT system ball screw wear state monitoring method based on motor current feedback - Google Patents

Abstract

The application relates to a motor current feedback-based OCT system ball screw wear state monitoring method, which comprises the following steps: starting the stepping motor, and performing i on the stepping motor _d Control of = 0; collection stepping motor A, B phase current i _A And i _B Obtaining dq axis current i by Park conversion _d And i _q And applying the d-axis current i _d And q-axis current i _q Storing; for d-axis current i _d Carrying out moving average filtering processing; judging d-axis current i _d Is in the absolute value of i _d If so, carrying out subsequent operation; otherwise, carrying out control early warning. The OCT system has the advantages of high working efficiency, accurate detection state, improvement of accuracy of the OCT system and timely replacement of the lead screw.

Description

OCT system ball screw wear state monitoring method based on motor current feedback

technical field

The present application relates to the field of optical coherence tomography system detection methods, in particular to a method for monitoring the wear state of a ball screw in an OCT system based on motor current feedback.

Background technique

Optical Coherence Tomography (OCT) is a microscopic imaging instrument used in the biomedical field. It is a research hotspot that has been widely concerned by the optical, biomedical and industrial circles for many years. OCT utilizes the basic principle of incoherent light interferometer, and can reconstruct two-dimensional or three-dimensional structural images of biological tissues through the analysis and processing of interference spectra. It has irreplaceable significance in biological biopsy, evaluation and grading of disease diagnosis, tissue and even cell structure and function detection, and in vivo observation of biological laws, and has obtained important research results.

As a key component in the transmission assembly of the OCT imaging system, the ball screw converts the rotational motion of the power motor into the plane movement of the OCT imaging system, and its quality directly affects the positioning accuracy and motion performance of the OCT. In order to make the working state of the ball screw have less influence on the accuracy, the staff generally choose to replace the screw regularly.

In actual use, the inventors have found that regular replacement of the lead screw may result in increased costs and waste of materials due to too short a replacement cycle; it may also result in untimely replacement of the lead screw due to an excessively long replacement cycle, thereby reducing the accuracy of the OCT imaging system. reduce.

Contents of the invention

In order to replace the lead screw in time, this application provides a method for monitoring the wear state of the ball screw in the OCT system based on motor current feedback. By monitoring the wear state of the lead screw, the lead screw can be replaced in time, thereby improving the system accuracy.

In the first aspect, an OCT system ball screw wear state monitoring method based on motor current feedback provided by the present application adopts the following technical scheme:

A method for monitoring the state of wear of a ball screw in an OCT system based on motor current feedback, comprising the following steps:

Start: start the stepper motor, and control the stepper motor with i _d = 0;

Collect d-axis current: collect stepping motor A, B-phase current i _A and i _B , obtain dq-axis current i _d and i _q through Park transformation, and store d-axis current i _d and q-axis current i _q ;

Process the d-axis current: perform sliding average filtering on the _d -axis current id;

Judging the d-axis current: judging whether the absolute value of the d-axis current _id is within the preset range of _id , and if so, perform follow-up operations; otherwise, perform control and early warning.

By adopting the above-mentioned technical scheme, by adopting i _d = 0 control, i _d is 0 in an ideal state, and in actual operation, i _d will produce an error within the controllable range, so after controlling i _d , then i _d is measured, so as to judge whether the system controls the motor normally through the range of i _d ; the measurement process has fewer control parameters, which is convenient for system regulation; the test data is less, so that the test efficiency is higher.

Optionally, in the step of judging the d-axis current, the preset range of the absolute value of i _d is 0-0.1A.

By adopting the above-mentioned technical scheme, through the normal range determined under reasonable experiments, the preset range of the absolute value of i _d is set to 0-0.1A, which can prevent the preset range from being too large and cause the test to be insensitive enough, and can also avoid prediction If the range is too small, the warnings will be too frequent.

Optionally, after the stepper motor is started, it moves at a constant speed.

By adopting the above technical scheme, the q-axis current i _q is proportional to the motor electromagnetic torque T _r when the stepping motor moves at a uniform speed, so that the change law of the motor electromagnetic torque T _r can be reflected by measuring the q-axis current i _q , thereby To judge the degree of screw wear.

Optionally, the following steps are also included:

Handle the q-axis current: perform low-pass filtering on the q-axis current i _q ;

Judging the q-axis current range: judging whether the maximum and minimum values of the q-axis current i _q are within the preset range of i _q .

By adopting the above technical scheme, during the uniform motion of the stepping motor, the motor needs to provide the electromagnetic torque T _r as:

T _r =μgM*B _P /(2πη) (1)

It can be known that there is a linear relationship between the electromagnetic torque T _r and the friction coefficient μ;

Therefore, when the amplitude and frequency range of i _q exceeds the preset range of i _q , it means that the electromagnetic torque T _r of the motor exceeds the normal range, that is, the friction coefficient μ of the screw produces a large error change, and the friction coefficient μ is too small to cause idling , the increase of the friction coefficient μ reflects that the lead screw is seriously damaged, and the lead screw needs to be replaced in time to reduce the error of the OCT system.

Optionally, in the step of judging the q-axis current range, the preset range of i _q is -3*I _n -3*I _n , and the 3I _n is the maximum value of i _q amplitude during factory calibration.

By adopting the above-mentioned technical scheme, the preset range of i _q is set through the maximum value of the amplitude of i _q during factory calibration, so that the referenceability of the data is enhanced, which not only reduces the frequent early warning replacement of the lead screw caused by too small a preset range, but also Provide timely early warning within a suitable range, and replace the lead screw with serious wear in time.

Optionally, the following steps are also included:

Analyze the q-axis current: perform Fourier analysis on the q-axis current i _q ;

Judging the spectrum range of the q-axis current: judging whether the spectrum range of the q-axis current i _q is concentrated within the preset frequency range of i _q .

By adopting the above technical scheme, the change of the backlash of the lead screw will be manifested as the periodic fluctuation of the electromagnetic torque T _r during the uniform motion process, resulting in the periodic change of the current i _q ; therefore, the current i _q of the q-axis of the motor can be used to The quality of the ball screw is monitored; when the periodic fluctuation of the electromagnetic torque T _r exceeds the normal range, adjust the backlash of the screw or replace the screw in time.

Optionally, the OCT system ball screw wear state monitoring method based on motor current feedback runs when the OCT system is powered on.

By adopting the above-mentioned technical solution, a detection is performed at the start-up, thereby reducing the influence of the wear of the lead screw on the operation of the OCT system after the start-up.

Optionally, in the starting step, after the stepper motor is started, perform mechanical zero return or move to a predicted position.

By adopting the above technical solution, the OCT system will perform a mechanical zeroing operation when it is turned on, and then move to a position commonly used by the user. During this process, the stepper motor will perform a constant speed and large-scale movement, and use this action to complete the current information. Acquisition and quality monitoring of the lead screw without additional operations by the user.

In the second aspect, the present application also provides a PC terminal, adopting the following technical solution:

A PC terminal includes a memory and a processor, and the memory stores a computer program that can be loaded by the processor and execute a method for monitoring the wear state of a ball screw in an OCT system based on motor current feedback.

In a third aspect, the present application provides a computer-readable storage medium, adopting the following technical solution:

A computer-readable storage medium stores a computer program capable of being loaded by a processor and executing a method for monitoring the wear state of a ball screw in an OCT system based on motor current feedback.

In summary, the present application includes at least one of the following beneficial technical effects:

1. Judging whether the control of the motor by the system is normal through the range of id; the measurement process has fewer control parameters, which is convenient for system regulation; the test data is less, so that the test efficiency is higher;

2. The q-axis current i _q is proportional to the electromagnetic torque T _r of the motor when the stepping motor moves at a constant speed, so that the change law of the electromagnetic torque T _r of the motor can be reflected by measuring the q-axis current i _q , so as to adjust the lead screw Judgment of the degree of wear;

3. Use the action of returning to zero when the OCT system is turned on to complete the collection of current information and the quality monitoring of the lead screw without additional operations by the user.

Description of drawings

Figure 1 is a two-phase stepper motor space vector diagram;

Fig. 2 is the flow diagram of the OCT system ball screw wear state monitoring method based on motor current feedback in embodiment 1;

Fig. 3 is the flow diagram of the OCT system ball screw wear state monitoring method based on motor current feedback in embodiment 2;

Figure 4 is the iq current waveform and its frequency spectrum when the factory calibrates;

5 is a block diagram of a method for monitoring the state of wear of a ball screw in an OCT system based on motor current feedback in Embodiment 3;

Fig. 6 is a flow chart of the method for monitoring the wear state of the ball screw in the OCT system based on motor current feedback in Embodiment 4.

i _A : Phase A current of the stepping motor;

i _B : Phase B current of the stepping motor;

i _s : stator current;

ψ _s : stator flux linkage;

i _d : d-axis current;

i _q : q-axis current;

ω _e : stepper motor angular velocity;

θ: The position signal of the motor rotor, that is, the angle between the d-axis and the A-phase winding;

p: Number of motor pole pairs:

ψ _f : permanent magnet flux linkage;

T _r : electromagnetic torque;

T _em : permanent magnet torque component;

M: load weight;

B _P : screw pitch;

η: mechanical efficiency;

μ: coefficient of friction;

g: acceleration due to gravity.

Detailed ways

The present application will be described in further detail below in conjunction with accompanying drawings 1-6.

The embodiment of the present application discloses a method for monitoring the wear state of a ball screw in an OCT system based on motor current feedback.

Example 1

Referring to Figure 1 and Figure 2, the OCT system ball screw wear state monitoring method based on motor current feedback includes the following steps:

S201: After the stepping motor is started, control the stepping motor with i _d = 0, and measure the AB phase current i _A and i _B ;

S300: The terminal equipment obtains the d, q axis currents i _d and i _q obtained after the AB phase current is transformed by Park, where the formula of Park transformation is:

Referring to Figure 1, θ is the position signal of the motor rotor, that is, the angle between the d-axis and the A-phase winding.

After obtaining the d and q axis currents _id and i _q , the terminal equipment stores _id and i _q .

S400: performing sliding average filtering on the _d -axis current id;

S500: performing early warning judgment on the d-axis current i _d ;

Wherein step S500 comprises step S510, step S511 and step S512;

S510: Judging whether -0.1A<i _d <0.1A is true, that is, whether the absolute value of i _d is within 0.1A;

S511: If -0.1A<i _d <0.1A is established, then the range of i _d is normal, and the system performs subsequent operations;

S512: If -0.1A<i _d <0.1A is not established, the range of i _d is abnormal, the data is invalid, and an early warning is controlled.

By adopting i _d = 0 control, i _d is 0 in an ideal state, and in actual operation, i _d will produce an error within the controllable range, so after controlling i d, measure _{i d again} , so as to pass The range of i _d judges whether the system controls the motor normally.

Example 2

Referring to FIG. 3 , the difference between this embodiment and Embodiment 1 is that step S201 is replaced by step S202; step S600, step S700 and step S701 are also provided after step S511.

S202: After the stepper motor is started, it moves at a constant speed, and obtains the AB phase current i _A and i _B

Referring to Fig. 1, by adopting i _d = 0 control, only the quadrature axis current component i _q is in the stator current i _s , at this time, the space vector of the magnetomotive force of the stator is orthogonal to the space vector of the magnetic field of the permanent magnet, and the motor output torque T _r Only the permanent magnet torque component T _em , the permanent magnet torque component T _em is:

T _em = pψ _f i _q (3)

Among them, p is the number of pole pairs of the motor, and its value is 50 in the present invention; ψ _f is the flux linkage of the permanent magnet, which is a constant value; therefore, the electromagnetic torque T _r of the motor is proportional to the q-axis current i _q .

The solid q-axis current i _q is proportional to the electromagnetic torque T _r of the motor when the stepping motor moves at a uniform speed, so the law of the electromagnetic torque T _r of the motor can be reflected by the q-axis current i _q .

S600: Perform current processing on the q-axis current i _q ;

S700: performing Fourier analysis on the q-axis current iq;

Step S701, step S701 includes step S710, step S711 and step S712;

S710: judging whether the amplitude-frequency range of i _q is normal;

Referring to Figure 4, in the _iq spectrum distribution of the manufacturer’s factory calibration, the low-frequency signal occupies the majority, concentrates within 25Hz, and reaches the peak at 4.79Hz. When the spectrum analysis changes greater than the preset ratio, it indicates that the ball screw back The gap becomes larger. In this embodiment, the preset ratio is set to 10%.

S711: If in the i _q spectrum distribution, the change of the spectrum analysis relative to the factory calibration data is less than or equal to 10%, the i _q spectrum range is normal;

S712: If in the i _q spectrum distribution, the spectrum analysis changes more than 10% relative to the factory calibration data, give an early warning.

The change of the backlash of the lead screw will be manifested as the periodic fluctuation of the electromagnetic torque T _r during the uniform motion process, which will cause the periodic change of the current i _q . Therefore, the quality of the ball screw can be monitored by the motor current.

Example 3

Referring to FIG. 5 , the difference between this embodiment and Embodiment 3 is that step S600 is followed by step S800 and step S801 .

S800: performing low-pass filtering on the q-axis current i _q ;

Step S801 includes step S810, step S811 and step S812;

S810: judging whether the i _q amplitude range is normal;

Among them, when judging the q-axis current range, refer to the maximum value I _n of the i _q amplitude during factory calibration for judgment, set the preset range of i _q to -3*I _n -3*I _n , and judge the amplitude-frequency range of i _q Whether it is within the preset range of i _q ;

S811: If the amplitude-frequency range of i _q is within the preset range of i _q , then the amplitude-frequency range of i _q is normal;

S812: If the amplitude-frequency range of i _q exceeds the preset range of i _q , give an early warning;

In the OCT system, the load weight M, screw pitch B _P , mechanical efficiency η, friction coefficient μ, and gravitational acceleration g are known. Then in the process of uniform motion, the motor needs to provide electromagnetic torque T _r as:

T _r =μgM*B _P /(2πη) (4)

It can be known that there is a linear relationship between the electromagnetic torque T _r and the friction coefficient μ;

When the amplitude and frequency range of i _q exceeds the preset range of i _q , it means that the electromagnetic torque T _r of the motor exceeds the normal range, that is, the friction coefficient μ of the screw produces a large error change, and the friction coefficient μ is too small to cause idling. The increase of the friction coefficient μ reflects that the lead screw is seriously damaged, and the lead screw needs to be replaced in time to reduce the error of the OCT system.

Example 4

Referring to Fig. 6, the difference between this embodiment and embodiment 1 is that step S600 is also provided after step S511, and step S700 and step S800 are arranged side by side after step S600; referring to embodiment 3 and embodiment 4, after step S700 Step S701 is provided, and step S801 is provided after step S800.

After both step S711 and step S811 are completed, that is, when the amplitude-frequency range and amplitude range of i _q are normal, proceed to step S900;

S900: Normal, that is, the wear state of the ball screw is normal.

That is, there is no need to replace the lead screw, and the normal operation of the OCT system can continue.

All of the above are preferred embodiments of the present application, and are not intended to limit the protection scope of the application. Therefore, all equivalent changes made according to the structure, shape and principle of the application should be covered by the protection scope of the application. Inside.

Claims (8)

1. A kind of OCT system ball screw wear condition monitoring method based on motor current feedback, it is characterized in that: comprise the following steps: Start: start the stepper motor, move at a constant speed, and control the stepper motor with i _d =0; Collect d-axis current: collect stepping motor A, B-phase current i _A and i _B , obtain dq-axis current i _d and i _q through Park transformation, and store d-axis current i _d and q-axis current i _q ; Process the d-axis current: perform sliding average filtering on the _d -axis current id; Judging the d-axis current: judging whether the absolute value of the d-axis current _id is within the preset range of _id , and if so, perform follow-up operations; otherwise, perform control and early warning; Handle the q-axis current: perform low-pass filtering on the q-axis current i _q ; Judging the q-axis current range: judging whether the maximum and minimum values of the q-axis current i _q are within the preset range of i _q ; During the uniform motion of the stepping motor, the motor needs to provide the electromagnetic torque _Tr as:

(1) in

is friction coefficient, g is gravitational acceleration, M is load weight, B _P is screw pitch,

is the mechanical efficiency; When the amplitude-frequency range of i _q exceeds the preset range of i _q , the electromagnetic torque T _r of the motor exceeds the normal range, and the friction coefficient μ of the lead screw produces an error change beyond the range, which reflects that the lead screw is seriously damaged. 2. The OCT system ball screw wear state monitoring method based on motor current feedback according to claim 1, characterized in that: in the step of judging the d-axis current, the preset range of the absolute value of _i is 0- 0.1A. 3. the OCT system ball screw wear state monitoring method based on motor current feedback according to claim 1, is characterized in that: in the described judgment q-axis current range step, described i _q preset range-3*I _n -3*I _n , where 3I _n is the maximum value of i _q amplitude during factory calibration. 4. the OCT system ball screw wear state monitoring method based on motor current feedback according to claim 1, is characterized in that: also comprise the following steps: Analyze the q-axis current: perform Fourier analysis on the q-axis current i _q ; Judging the spectrum range of the q-axis current: judging whether the spectrum range of the q-axis current i _q is concentrated within the preset frequency range of i _q ; the change of the backlash of the lead screw is manifested as the periodic fluctuation of the electromagnetic torque T _r in the process of uniform motion, Make the periodic change of the current i _q , and reflect the change of the screw backlash through the q-axis current i _q of the motor. 5. The OCT system ball screw wear state monitoring method based on motor current feedback according to claim 1, characterized in that: the OCT system ball screw wear state monitoring method based on motor current feedback runs when the OCT system is powered on . 6. The OCT system ball screw wear state monitoring method based on motor current feedback according to claim 1, characterized in that: in the starting step, after the stepper motor is started, perform mechanical zeroing or move to the predicted position . 7. A PC terminal, characterized by comprising a memory and a processor, the memory storing a computer program capable of being loaded by the processor and executing any one of the methods according to claims 1 to 6. 8. A computer-readable storage medium, characterized by storing a computer program capable of being loaded by a processor and executing any one of the methods according to claims 1-6.

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