CT bulb tube positive rotation control optimization method based on temperature model prediction

Abstract

The invention relates to a CT bulb tube positive rotation control optimization method based on temperature model prediction, and relates to the technical field of motor control. The method comprises the following steps: setting an experiment environment and establishing a temperature prediction model, wherein the setting of the experiment environment comprises setting a reference environment temperature; dynamically compensating the driving voltage of the positive rotation winding according to the model prediction temperature; acquiring an actual temperature value of the positive rotation winding; and optimizing the temperature prediction model, and readjusting the driving voltage of the positive rotation winding according to the optimized temperature prediction model. The method has the effect of improving the control precision of rotation of the anode of the CT bulb tube.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of motor control, in particular to a CT tube positive rotation control optimization method based on temperature model prediction. BACKGROUND

[0002] Before high-power CT tube exposure, the anode target disc needs to be rotated and reach a certain speed to prevent damage to the target disc.

[0003] At present, the target disc motor is mostly designed as an asynchronous motor and is driven by a three-phase bridge arm inverter. In order to quickly rotate the target disc before exposure, the driving voltage and frequency parameters in the starting process are often carefully designed and debugged.

[0004] However, the parameters are most suitable for the first start of the tube in a cold state. In actual use scenarios, as the positive rotation continuously starts, operates and brakes, the temperature of the positive rotation winding will increase greatly, thereby affecting the winding resistance, so that the originally carefully designed parameters are no longer suitable, the positive rotation cannot achieve the target acceleration effect, the stress on the target disc during subsequent exposure is increased, the service life of the tube is reduced, and the exposure inspection effect is not good. SUMMARY

[0005] In order to improve the control accuracy of the CT tube anode rotation, the application provides a CT tube positive rotation control optimization method based on temperature model prediction.

[0006] The CT tube positive rotation control optimization method based on temperature model prediction provided by the application adopts the following technical scheme: A CT tube positive rotation control optimization method based on temperature model prediction, comprising the following steps: Setting an experimental environment and establishing a temperature prediction model, wherein the setting of the experimental environment comprises setting a reference ambient temperature; According to the model, the driving voltage of the positive rotation winding is dynamically compensated; An actual temperature value of the positive rotation winding is obtained; The temperature prediction model is optimized, and the driving voltage of the positive rotation winding is readjusted according to the optimized temperature prediction model.

[0007] By adopting the above technical scheme, through the establishment of the temperature prediction model, the dynamic compensation of the driving voltage, the actual temperature feedback and the model iteration optimization, the stable acceleration of the positive rotation winding under different temperature conditions is realized, and the performance decline caused by overheating or undercompensation is avoided.

[0008] As a preferred, the establishment of the temperature prediction model comprises the following steps: After the positive rotation stops, the change of the winding temperature with time is monitored in real time, and a temperature-time curve is recorded; The temperature-time curve is segmented linearly fitted, the temperature-time curve is divided into n continuous time periods, and the slope of each time period corresponding linear segment is obtained.

[0009] By adopting the technical scheme, the complex nonlinear heat dissipation process is simplified into multiple slope parameters through segmented linear fitting of the temperature-time curve, so that the model is easy to store and calculate in an embedded system, and the hardware resource requirement is reduced.

[0010] As preferred, the calculation formula of the driving voltage of the dynamic compensation positive rotating winding is: ; Wherein, and respectively represent the corrected driving voltage and the initial driving voltage, T is the reference ambient temperature, T' is the predicted temperature value obtained through the temperature prediction model, C is the temperature coefficient of the positive rotating winding wire material, and β is the driving voltage compensation coefficient.

[0011] By adopting the technical scheme, the mathematical formula of the driving voltage compensation is clarified.

[0012] As preferred, after the positive rotating winding starting process ends, the maximum current and the positive rotating speed detection result in the starting process are collected, if the maximum current and the positive rotating speed are both less than the test result under the cold state, the value of β is increased, if the maximum current exceeds the test result under the cold state, the value of β is reduced, and in other cases, the value of the current β is maintained unchanged.

[0013] By adopting the technical scheme, the driving effect can be enhanced or the damage to the positive rotation caused by excessive current can be prevented by adjusting the value of β according to the actual situation.

[0014] As preferred, the actual temperature value of the positive rotating winding is obtained, including the following contents: The temperature calculation formula of the positive rotating winding is: ; Wherein, c is the temperature coefficient of the wire material, T is the reference ambient temperature, is the winding temperature conversion rate; The calculation formula of is: ; Wherein, is the effective value of the positive rotating each-phase driving voltage, is the effective value of the positive rotating each-phase driving current, is the positive rotating stator driving frequency, is the positive rotating equivalent circuit each-phase inductance value, and S is the slip rate; T is the ambient temperature the positive rotation equivalent circuit per-phase stator resistance value; ambient temperature the positive rotation equivalent circuit per-phase rotor resistance value.

[0015] By adopting the technical scheme, the equivalent circuit model is used to realize the sensorless temperature monitoring.

[0016] As preferred, the temperature prediction model is optimized according to the comparison result, including the following steps: The actual temperature value Tact at the same time and the predicted temperature value Tpre obtained by the temperature prediction model are obtained, and a temperature ratio r is calculated, r=Tact / Tpre; A temperature ratio range is set, and a corresponding slope adjustment coefficient is set according to the temperature ratio range, so as to establish a slope adjustment coefficient table; The temperature prediction model is corrected according to the established slope adjustment coefficient table.

[0017] By adopting the technical scheme, the temperature ratio r is classified and corrected, so as to avoid over-adjustment.

[0018] As preferred, the slope of the temperature prediction model is corrected, including the following steps: The winding temperature Ts at the brake shutdown time and the corresponding time ts are obtained; The predicted temperature Tx,pred at a future time tx is calculated through the temperature prediction model; After the positive rotation is started and enters a steady state, the actual temperature value Tx,actual at the time tx is obtained; The temperature ratio r is calculated, and a correction coefficient is determined by referring to the slope adjustment coefficient table; The slope of the related straight line segment between the shutdown time ts and tx is corrected according to the determined correction coefficient.

[0019] By adopting the technical scheme, the range and logic of slope correction are limited, so as to ensure that only the slope related to the error time period is adjusted, and the accuracy of other segments is reserved; and by cooperatively correcting the slopes of multiple segments, the continuity of the temperature curve can be maintained.

[0020] As described above, the present application includes at least one of the following beneficial technical effects: 1. By dynamically adjusting the driving voltage compensation coefficient, the winding resistance change under different temperature conditions is automatically adapted, so that the positive rotation system can maintain consistent starting performance under various working conditions; 2. The temperature prediction model can be dynamically corrected, the prediction accuracy is continuously optimized through the real-time feedback mechanism, different device individual differences and environmental condition changes can be adapted, and the accuracy of temperature control is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a step flow chart of an embodiment of the present application; Figure 2 is a CT tube positive spin winding heat dissipation temperature curve chart in an embodiment of the present application; Figure 3 is an equivalent circuit diagram of the positive spin winding of an embodiment of the present application; Figure 4 is a start-up acceleration process optimization curve chart in an embodiment of the present application; Figure 5 is a CT tube positive spin winding heat dissipation temperature curve optimization curve chart in an embodiment of the present application. DETAILED DESCRIPTION

[0022] The following will be described in detail in combination with Figures 1-5 the present application.

[0023] An embodiment of the present application discloses a CT tube positive spin control optimization method based on temperature model prediction.

[0024] Referring to Figure 1 , a CT tube positive spin control optimization method based on temperature model prediction includes the following steps: S1: establishing a temperature prediction model; S2: dynamically compensating the driving voltage of the positive spin winding according to the model predicted temperature; S3: iteratively optimizing the driving voltage compensation coefficient; S4: obtaining the actual temperature value of the positive spin winding; S5: iteratively optimizing the temperature prediction model.

[0025] Step S1, establishing a temperature prediction model, includes the following steps: S11: experimental environment setting. Select the model of the tube and set the working heat dissipation conditions, including the reference ambient temperature, cooling air speed and heat dissipation performance, etc. Moreover, the selection of the tube model is as extensive as possible, and the working heat dissipation conditions need to be as consistent as possible with the tube application scenarios, so as to simulate the actual use scenarios.

[0026] S12: after the positive spin is stopped, the winding temperature change with time is monitored in real time, and the temperature-time curve is recorded. The horizontal axis of the temperature-time curve is time t, and the vertical axis is temperature value T.

[0027] S13: Piecewise linear fitting is performed on the temperature-time curve. Since the temperature-time curve is nonlinear, direct storage and calculation will occupy a large number of chip resources and is low in efficiency, therefore, the temperature-time curve is divided into n continuous time periods, a straight line segment is used to approximate the curve, and the temperature change slope of each segment is recorded. Specifically, t1 is the initial time and the temperature at t1 is T1, the temperature at t2 is T2, and so on, tn is the initial time and the temperature at tn is Tn. The slope of the straight line segment between t1-t2 is k1_2, the slope of the straight line segment between t2-t3 is k2_3, and so on, the slope of the straight line segment between t(n-1)-tn is k(n-1)_n. The number of time periods can be set according to the accuracy requirement. Figure 2 The embodiment of the present application divides the temperature-time curve into four time periods for illustration.

[0028] S14: Model parameter storage. The slope and the corresponding time period parameters are stored in the memory (such as Flash or EEPROM) of the control chip for subsequent real-time control calling.

[0029] Step S2, the driving voltage of the positive rotating winding is compensated according to the model predicted temperature, including the following contents: Reference Figure 3 The equivalent circuit of the positive rotating winding includes a power supply Vphase, a plurality of resistors and a plurality of inductors. The resistors include resistor R1, resistor Rn, resistor R2' and resistor Rm, and the inductors include inductor X1, inductor Xn, inductor X2 and inductor Xm. The voltage output end of the power supply Vphase is electrically connected to the negative electrode of the power supply Vphase through resistor Rn, inductor Xn, resistor Rm and inductor Xm in turn, and the voltage output end of the power supply Vphase is also electrically connected to the negative electrode of the power supply Vphase through resistor R1, inductor X1, inductor X2 and resistor R2' in turn.

[0030] On the stator side, resistor R1 and inductor X1 represent the copper loss and leakage magnetic effect of the stator winding; on the rotor side, resistor Rn and inductor Xn are used to equivalently reflect the rotor bar resistance and leakage, and resistor R2' and inductor X2 are used to equivalently reflect the impedance characteristics of the rotor bar. In addition, resistor Rm and inductor Xm are used to represent the core loss and the energy storage of the main magnetic field. The equivalent resistance value of the rotor in the equivalent circuit is R2' / s, wherein s is the slip.

[0031] The inductance value of the inductor is little affected by temperature change and can be ignored, while the resistance value of the resistor is more obviously affected by temperature. The formula for the resistance value affected by temperature is: ; Wherein, T is the reference ambient temperature, T' is the predicted temperature value obtained by the temperature prediction model, R, R' respectively represent the corresponding resistance value of the winding at T, T' temperature, C represents the temperature coefficient of the wire material, for example, when using copper as the wire material, C is 235.

[0032] Referring to Figure 4 , at the beginning of starting, s≈1, the impedance is dominated by the inductive reactance X1+X2', the resistance value of the resistor has little effect, and the driving voltage remains consistent with the initial strategy. In the later stage of operation, s tends to 0, the equivalent resistance value R2' / s of the rotor increases significantly, and the resistance value of the resistor becomes the main influencing factor. At this time, the driving voltage needs to be increased together with the resistance value of the resistor to maintain the driving current and driving torque. According to Ohm's law, the final corrected driving voltage is: ; Wherein, and respectively represent the corrected driving voltage and the initial driving voltage, and β is the driving voltage compensation coefficient to avoid excessive compensation leading to excessively high driving voltage. The value of β ranges from 0 to 1, and the initial value of β is set to 0.5. In the subsequent work process, the value of β will be continuously feedback and rolling corrected.

[0033] Step S3, iterative optimization of driving voltage compensation coefficient, including the following contents: After the starting process is completed, the maximum current and the sun rotation speed detection results during the starting process are collected. If both the maximum current and the sun rotation speed are less than the test results in the cold state, the value of β is increased to enhance the driving effect. If the maximum current exceeds the test results in the cold state, the value of β is decreased to prevent damage to the sun caused by excessive current. In other cases, the current value of β is maintained unchanged.

[0034] S4: Obtain the actual temperature value of the sun winding.

[0035] When the sun enters the steady state operation, the driving voltage value, current value, frequency and slip of the sun winding at this time are obtained, and the actual temperature value of the sun winding at this time is calculated.

[0036] The temperature calculation formula of the sun winding is: ; Wherein, c is the temperature coefficient of the wire material, is the reference ambient temperature, is the winding temperature conversion rate.

[0037] The calculation formula of is: ; Wherein, is the effective value of the driving voltage of each phase of the sun, is the effective value of the driving current of each phase of the sun, is the driving frequency of the positive-rotating stator, is the inductance value of each phase of the positive-rotating equivalent circuit, and S is the slip ratio. is the ambient temperature is the stator resistance value of each phase of the positive-rotating equivalent circuit. is the ambient temperature is the rotor resistance value of each phase of the positive-rotating equivalent circuit.

[0038] S5: Iterative optimization of the temperature prediction model.

[0039] S51: Set the slope adjustment coefficient.

[0040] The actual temperature value Tact and the predicted temperature value Tpre at the same time are obtained, and the temperature ratio r is calculated, r = Tact / Tpre. When r > 1, it means that the actual heat dissipation condition is worse than the temperature prediction model, so the temperature drop slope in the temperature prediction model needs to be reduced. When r < 1, it means that the actual heat dissipation condition is better than the temperature prediction model, so the temperature drop slope in the temperature prediction model needs to be increased.

[0041] Set the temperature ratio range, and set the corresponding slope adjustment coefficient according to the temperature ratio range, to establish a slope adjustment coefficient table, for example: Temperature ratio range <0.8 0.8-0.9 0.9-1.1 1.1-1.2 >1.2 Slope adjustment factor 1.1 1.05 1 0.95 0.9 The adjustment coefficient table of different ball tube models can be customized to adapt to individual differences.

[0042] S52: Slope correction.

[0043] The winding temperature Ts at the brake shutdown time and the corresponding time ts are obtained.

[0044] Through the temperature prediction model, the predicted temperature Tx,pred at a future time tx is calculated.

[0045] After the positive-rotating starts and enters a steady state, the actual temperature value Tx,actual at time tx is obtained.

[0046] The ratio is calculated and the correction coefficient is determined by table lookup method.

[0047] The slope of the relevant straight line segment from the shutdown time ts to tx needs to be adjusted.

[0048] Reference Figure 5 For example, the winding temperature at brake shutdown is T2, and after a period of time, the predicted winding temperature at t4 is calculated by the model to be T4. The actual measured winding temperature at t4 in the above process is 1.15*T4, so the slopes k2_3 and k3_4 are both corrected to 0.95 times of the original value by table lookup.

[0049] After step S5 ends, return to step S2 and start a cycle. The starting process driving voltage compensation parameter is optimized in a rolling manner according to the optimized temperature prediction model, so that the control effect is continuously optimized to achieve the best positive spin starting acceleration effect, and the temperature prediction model is optimized in a rolling manner.

[0050] The implementation principle of the CT tube positive spin control optimization method based on a temperature model prediction according to an embodiment of the application is as follows: a temperature prediction model of a CT tube positive spin winding is established, and the driving voltage is compensated through the model to optimize the acceleration effect; the model parameters and the compensation parameters are optimized in a rolling manner in the actual operation process to achieve better effect.

[0051] The above are preferred embodiments of the application, and do not limit the protection scope of the application, so: any equivalent changes made according to the structure, shape, principle of the application should be covered within the protection scope of the application.

Claims

1. A method for optimizing the vortex control of a CT X-ray tube based on temperature model prediction, characterized in that: Includes the following steps: Set up the experimental environment and establish a temperature prediction model, wherein setting up the experimental environment includes setting a reference ambient temperature; The driving voltage of the anode winding is predicted based on the model to dynamically compensate for temperature. Obtain the actual temperature value of the male rotary winding; Optimize the temperature prediction model, and readjust the driving voltage of the anode winding based on the optimized temperature prediction model; establish the temperature prediction model, including the following steps: After the anode winding is shut down, the temperature change of the winding over time is monitored in real time, and the temperature-time curve is recorded. Piecewise linear fitting is performed on the temperature-time curve, dividing the temperature-time curve into n consecutive time periods, and the slope of the corresponding straight line segment for each time period is obtained.

2. The CT X-ray tube vortex control optimization method based on temperature model prediction according to claim 1, characterized in that: The formula for calculating the driving voltage of the dynamically compensated anode winding is as follows: ； in, and These represent the corrected driving voltage and the initial driving voltage, respectively. T is the reference ambient temperature, T' is the predicted temperature value obtained through the temperature prediction model, C is the temperature coefficient of the anode winding conductor material, and β is the driving voltage compensation coefficient.

3. The CT X-ray tube vortex control optimization method based on temperature model prediction according to claim 1, characterized in that: After the start-up process of the anode winding is completed, the detection results of the maximum current and anode rotation speed during the start-up process are collected. If both the maximum current and the anode rotation speed are less than the test results under cold conditions, the value of β is increased; if the maximum current exceeds the test results under cold conditions, the value of β is decreased; otherwise, the current value of β is maintained unchanged.

4. The CT X-ray tube vortex control optimization method based on temperature model prediction according to claim 1, characterized in that: Obtain the actual temperature value of the male winding, including the following: The formula for calculating the temperature of the anode winding is: ; Where c is the temperature coefficient of the conductor material. For reference to ambient temperature, This is the winding temperature conversion factor; The calculation formula is: ; in, This represents the effective value of the driving voltage per phase of the rotating coil. This represents the effective value of the driving current per phase of the anode. This is the driving frequency of the male-rotating stator. is the inductance per phase of the cyclone equivalent circuit, and S is the slip. For ambient temperature Below, the stator resistance value per phase of the cyclone equivalent circuit; For ambient temperature Below, the rotor resistance value of each phase in the cyclone equivalent circuit.

5. The CT X-ray tube vortex control optimization method based on temperature model prediction according to claim 1, characterized in that: The temperature prediction model is optimized based on the comparison results, including the following steps: The actual temperature value Tact and the predicted temperature value Tpre obtained through the temperature prediction model at the same time are obtained, and the temperature ratio r is calculated, r = Tact / Tpre; Set the temperature ratio range, and set the corresponding slope adjustment coefficient according to the temperature ratio range, and establish a slope adjustment coefficient table; The temperature prediction model is corrected based on the established slope adjustment coefficient table.

6. The CT X-ray tube vortex control optimization method based on temperature model prediction according to claim 5, characterized in that: Correcting the slope of the temperature prediction model includes the following steps; Obtain the winding temperature Ts and the corresponding time ts at the moment of braking and stopping; The predicted temperature Tx,pred at a future time tx is calculated using a temperature prediction model. After the cyclone starts and enters a steady state, the actual temperature value Tx,actual at time tx is obtained; Calculate the temperature ratio r and determine the correction factor by referring to the slope adjustment factor table; The slope of the relevant straight line segment from the shutdown time ts to tx is corrected based on the determined correction factor.

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