High-precision discrete PI temperature control method suitable for S7500 laser

Abstract

The invention discloses a high-precision discrete PI temperature control method suitable for an S7500 laser. The method comprises the following steps: determining an input temperature value, setting a temperature value, a heating capability UPVL and a cooling capability HIVL; calculating a temperature difference value according to the input temperature value and the set temperature value; according to the temperature difference value and the discrete KP value, a PI conversion median value is calculated; updating a temperature control discrete PI value according to the temperature difference value, the discrete KI value and the PI conversion mid-value; calculating a duty ratio set value and a temperature discrete PI value at the current moment according to the updated temperature control discrete PI value and the temperature rising capability; according to the duty ratio set value at the current moment, PWM output at the current moment is solved; and according to the temperature discrete PI value and the temperature rising capability, a laser temperature control direction signal at the current moment is solved, a laser driving power signal is output, and laser output driving is carried out.

Description

Technical Field

[0001] This invention relates to a high-precision discrete PI temperature control method suitable for S7500 lasers, belonging to the field of aerospace overall technology. Background Technology

[0002] With the rapid development of aerospace technology, the demand for miniaturized, low-cost, and high-performance digital single-unit sensors is constantly increasing, involving multiple fields such as remote sensing, communication, and microsatellites. In the field of space deformation measurement, fiber Bragg gratings (FBGs) are fiber optic sensors with advantages such as high sensitivity, light weight, and strong anti-interference capabilities. They can measure physical quantities such as temperature and strain. FBG sensors can form sensor networks through wavelength division multiplexing, greatly reducing the difficulty of sensor wiring. In this field, output temperature control of lasers used in conjunction with fiber Bragg gratings has become a significant engineering challenge. The S7500 laser continuously linearly scans at 20 pm intervals within the wavelength range of 1527nm to 1567nm, achieving a single-point wavelength accuracy better than 2pm. Traditional temperature control algorithms can only guarantee the laser's operation within a ±1℃ working environment. With the gradual development of deformation measurement technology, a ±1℃ working environment can no longer guarantee stable output at specific laser wavelengths, making higher-precision temperature control algorithms increasingly necessary. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a high-precision discrete PI temperature control method suitable for S7500 lasers.

[0004] The technical solution of this invention is: This invention discloses a high-precision discrete PI temperature control method suitable for S7500 lasers, comprising: Determine the input temperature value, set the temperature value, and define the heating capacity (UPVL) and cooling capacity (HIVL). Calculate the temperature difference based on the input temperature value and the set temperature value; Calculate the PI conversion median based on the temperature difference and discrete KP values; Update the temperature control discrete PI value based on the temperature difference, discrete KI value, and PI conversion median. Based on the updated temperature control discrete PI value and heating capacity, calculate the duty cycle setting value and temperature discrete PI value at the current moment; Calculate the PWM output at the current moment based on the current duty cycle setting value; Based on the temperature discrete PI value and heating capacity, the laser temperature control direction signal at the current moment is obtained, and the laser drive power signal is output to drive the laser output.

[0005] Furthermore, in the above method, the temperature difference is calculated based on the input temperature value and the set temperature value, specifically as follows: When the input temperature value is greater than the set temperature value: PI_ERR_TEMP = FEED_VALUE - SET_VALUE; When the set temperature value is greater than the input temperature value: PI_ERR_TEMP = SET_VALUE - FEED_VALUE; Where PI_ERR_TEMP is the temperature difference, FEED_VALUE is the input temperature value, and SET_VALUE is the set temperature value.

[0006] Furthermore, in the above method, the PI transformation median is calculated based on the temperature difference and the discrete KP value, specifically as follows: PI_KP_REG = Data_Kp * PI_ERR_TEMP; Wherein, PI_KP_REG is the median of the PI conversion, Data_Kp is the discrete KP value, and PI_ERR_TEMP is the temperature difference value.

[0007] Furthermore, in the above method, the temperature control discrete PI value is updated based on the temperature difference, the discrete KI value, and the PI transformation median, specifically as follows: When the input temperature value is greater than the set temperature value: PI_KI_REG = PI_KI_MID + Data_Kit*PI_ERR_TEMP; When the input temperature value is lower than the set temperature value: PI_KI_REG = PI_KI_MID - Data_Kit*PI_ERR_TEMP; Wherein, PI_KI_REG is the discrete PI value for temperature control, PI_KI_MID is the median of the PI conversion, Data_Kit is the discrete KI value, and PI_ERR_TEMP is the temperature difference value.

[0008] Furthermore, in the above method, the step of calculating the duty cycle setting and temperature discrete PI value at the current moment based on the updated temperature control discrete PI value and heating capacity specifically involves: TEC_PWM_PI = PI_KI_REG + PI_KP_REG; PWM_REAL = TEC_PWM_PI-UPVL; Wherein, PWM_REAL is the duty cycle setting value at the current moment; UPVL is the heating capacity; PI_KI_REG is the discrete PI value for temperature control; PI_KP_REG is the median value of PI conversion; and TEC_PWM_PI is the discrete PI value for temperature.

[0009] Furthermore, in the above method, the step of obtaining the PWM output at the current moment based on the current duty cycle setting value specifically involves: When the duty cycle setting value is greater than the actual PWM output period, the PWM output is 1; when the duty cycle setting value is less than the actual PWM output period, the PWM output is 0.

[0010] Furthermore, in the above method, the step of obtaining the laser temperature control direction signal at the current moment based on the temperature discrete PI value and the heating capacity specifically involves: When the temperature discrete PI value is greater than the heating capacity UPVL, the temperature control direction signal is set to 0. When the temperature discrete PI value is less than the heating capacity UPVL, the temperature control direction signal is set to 1.

[0011] The advantages of this invention over the prior art are as follows: (1) This invention addresses the problem that the temperature control accuracy of the S7500 in current miniaturized electronic single-unit lasers is only ±1℃, which cannot meet the requirements for higher precision laser stable output. It designs a high-precision temperature control algorithm with segmented discrete PI, enabling the implementation of a high-precision discrete PI temperature control algorithm using HDL language in aerospace miniaturized electronic single-unit lasers. Under an external environment of ±10℃, the temperature control accuracy of the S700 laser can be improved from the traditional ±1℃ variation to ±0.01℃.

[0012] (2) This invention uses aerospace FLASH type FPGA products and combines them with the low current difference scheme of the laser driving module. By designing the expected discrete value, the PI control rate is periodically controlled, which solves the over-control problem of the simple PI control strategy under the condition of using FPGA and can ensure the effectiveness of the temperature control range.

[0013] (3) In the discrete PI temperature control process, this invention adopts a data-aligned control strategy and uses steady-state monitoring of temperature data and PWM output expectations instead of non-steady-state monitoring. Therefore, it has lower requirements for temperature control timeliness and is more suitable for implementation in aerospace FPGA products. It provides a high-precision control method for laser output temperature control applications using FPGA. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the principle structure of the high-precision discrete PI control module of the present invention; Figure 2This is a schematic diagram of the laser driver module of the present invention; Figure 3 This is the current amplifier circuit model of the present invention. Detailed Implementation

[0015] The following is combined Figure 1 , Figure 2 , Figure 3 The present invention will be further described below.

[0016] This invention discloses a high-precision discrete PI temperature control method suitable for S7500 lasers, comprising: Determine the input temperature value, set the temperature value, and define the heating capacity (UPVL) and cooling capacity (HIVL). Calculate the temperature difference based on the input temperature value and the set temperature value; Calculate the PI conversion median based on the temperature difference and discrete KP values; Update the temperature control discrete PI value based on the temperature difference, discrete KI value, and PI conversion median. Based on the updated temperature control discrete PI value and heating capacity, calculate the duty cycle setting value and temperature discrete PI value at the current moment; Calculate the PWM output at the current moment based on the current duty cycle setting value; Based on the temperature discrete PI value and heating capacity, the laser temperature control direction signal at the current moment is obtained, and the laser drive power signal is output to drive the laser output.

[0017] Preferably, the temperature difference is calculated based on the input temperature value and the set temperature value, specifically as follows: When the input temperature value is greater than the set temperature value: PI_ERR_TEMP = FEED_VALUE - SET_VALUE; When the set temperature value is greater than the input temperature value: PI_ERR_TEMP = SET_VALUE - FEED_VALUE; Where PI_ERR_TEMP is the temperature difference, FEED_VALUE is the input temperature value, and SET_VALUE is the set temperature value.

[0018] Preferably, the PI transformation median is calculated based on the temperature difference and the discrete KP value, specifically as follows: PI_KP_REG = Data_Kp * PI_ERR_TEMP; Wherein, PI_KP_REG is the median of the PI conversion, Data_Kp is the discrete KP value, and PI_ERR_TEMP is the temperature difference value.

[0019] Preferably, the temperature control discrete PI value is updated based on the temperature difference, the discrete KI value, and the PI conversion median, specifically as follows: When the input temperature value is greater than the set temperature value: PI_KI_REG = PI_KI_MID + Data_Kit*PI_ERR_TEMP; When the input temperature value is lower than the set temperature value: PI_KI_REG = PI_KI_MID - Data_Kit*PI_ERR_TEMP; Wherein, PI_KI_REG is the discrete PI value for temperature control, PI_KI_MID is the median of the PI conversion, Data_Kit is the discrete KI value, and PI_ERR_TEMP is the temperature difference value.

[0020] Preferably, based on the updated temperature control discrete PI value and heating capacity, the duty cycle setting value and temperature discrete PI value at the current moment are calculated, specifically as follows: TEC_PWM_PI = PI_KI_REG + PI_KP_REG; PWM_REAL = TEC_PWM_PI-UPVL; Wherein, PWM_REAL is the duty cycle setting value at the current moment; UPVL is the heating capacity; PI_KI_REG is the discrete PI value for temperature control; PI_KP_REG is the median value of PI conversion; and TEC_PWM_PI is the discrete PI value for temperature.

[0021] Preferably, the PWM output at the current moment is obtained based on the current duty cycle setting value, specifically as follows: When the duty cycle setting value is greater than the actual PWM output period, the PWM output is 1; when the duty cycle setting value is less than the actual PWM output period, the PWM output is 0.

[0022] Preferably, the laser temperature control direction signal at the current moment is obtained based on the temperature discrete PI value and the heating capacity, specifically as follows: When the temperature discrete PI value is greater than the heating capacity UPVL, the temperature control direction signal is set to 0. When the temperature discrete PI value is less than the heating capacity UPVL, the temperature control direction signal is set to 1.

[0023] Example This embodiment provides a high-precision discrete PI temperature control system suitable for S7500 lasers, including a high-precision discrete PI control module, an S7500 laser driver module, and a data alignment module. Figure 1This is a schematic diagram of the high-precision discrete PI control module of the present invention. In the schematic diagram, R(s) is the temperature setpoint, Y(s) is the temperature output value, G(s) is the transfer function of the controlled temperature, and F(s) is the prediction transfer function. The specific implementation steps of the discrete PI control module are as follows: S1. Determine the output control objects, which are the laser temperature control direction signal TEC_DIR and the laser drive power signal TEC_PWM; S2. Determine the control cycle. Based on the current FPGA application environment, the control cycle is determined to be 50µs. S3. Determine the target preset value. Based on the temperature feedback value from the S7500 laser control, determine the target preset value as 0x7F9. S4. Determine the maximum unit temperature control capacity, with the heating capacity UPVL and cooling capacity HIVL set to 0x80; S5. Determine the key parameters for controlling TEC_PWM, including the temperature control discrete PI value TEC_PWM_PI, the heating capacity UPVL, and the duty cycle setting value PWM_REAL; S6. Determine the input temperature value TEC_TEP, set the temperature value SET_VALUE, the differential temperature PI_ERR_TEMP, the discrete parameters Data_Kp and Data_Kit, and the PI transformation median PI_KI_MID; S7. Instantiate the above engineering parameters respectively, start time counting, set the time threshold to 50us, and start temperature control when the time threshold is reached; S8. Determine the relationship between TEC_TEP and SET_VALUE, and determine the current temperature difference. S9. Calculate the PI conversion median based on the magnitude of the temperature difference and the discrete KP values; S10. Based on the temperature difference, discrete KI value, and PI conversion median, update the temperature control discrete PI value (PI_KP_REG, PI_KI_REG). S11. Determine the relationship between TEC_TEP and SET_VALUE, subtract or sum PI_KI_REG and PI_KP_REG, and calculate TEC_PWM_PI; S12. Based on the latest obtained TEC_PWM_PI and UPVL, calculate PWM_REAL at the current time. S13. Calculate the current TEC_PWM based on the latest obtained PWM_REAL; S14. Calculate the current TEC_DIR based on the latest obtained TEC_PWM_PI; S15. Drive the laser output according to the current TEC_PWM and TEC_DIR.

[0024] Figure 2 This is a schematic diagram of the laser driver module of the present invention. The specific application scheme derivation scheme is as follows: Based on the virtual interrupt principle of operational amplifiers, the following formula is derived: …………(1) = …………(2) Based on the virtual short principle of operational amplifiers, the formula is derived. = …………(3) Based on equations (1), (2), and (3), we can derive... = …………(4) In this embodiment It is clear that the output current is twice the input current.

[0025] Based on engineering experience, the relationship between the accuracy of the left arm current, right arm current, and phase current of the S7500 laser and the laser output wavelength is shown in the table below.

[0026] Table 1. Relationship between left arm, right arm, phase current and wavelength.

[0027] When the laser is working, the scanning wavelength step is 20pm, and the error requirement is ±2pm. Referring to the table above, the current error requirement is ±2.676uA.

[0028] Because operational amplifiers have parasitic parameters such as input offset voltage, input offset current, and input bias current, and the input bias current of operational amplifiers... Input bias current to the non-inverting input of the op-amp and the bias current input to the inverting terminal The average value, i.e. = (5) Input offset current This is the difference between the input bias current at the non-inverting input and the input bias current at the inverting input.

[0029] (6) Equations (7) and (8) are obtained from equations (5) and (6).

[0030] = (7) = (8) The input bias current, input offset current, and input offset voltage of the op-amp are respectively , and The circuit model of the current multiplier circuit used is as follows: Figure 3 As shown.

[0031] The input offset voltage drift of the operational amplifier LMH6628 is 5uV / ℃. The maximum temperature variation in the operating environment is 20℃. With R3 set to 50Ω, the current error caused by temperature variation is 2uA, which meets the error requirement.

[0032] This invention employs a high-precision discrete PI temperature control algorithm to maintain the temperature of the target laser (S7500) within the range of 25±0.01℃ under conditions where the external temperature variation is less than ±10℃. This achieves stable operation of the laser's multi-spectral lasing capabilities and can also be widely applied in ground-based electronic equipment using this laser.

[0033] Phase shifting is divided into coarse phase shifting and fine phase shifting. When the accompanying clock frequency of the interface link is much lower than the system clock frequency of the FPGA, coarse phase shifting can be achieved using a time-delay operation. When the accompanying clock frequency of the interface link is high, and time-delaying using the FPGA's system clock cannot meet the phase shifting accuracy, fine phase shifting is required. Fine phase shifting can achieve phase shifting accuracy down to the sub-system clock cycle level. The phase shifting method used in this invention is a fine phase shifting implemented using HDL. Because it does not use a high-performance IP core, it has lower requirements for the FPGA's system clock and performance.

[0034] The method for discrete PI temperature control in this invention consists of two steps: 1) Discrete PI temperature control hardware design When the laser is working, the scanning wavelength step is 20pm, and the error requirement is ±2pm. Referring to the table above, the current error requirement is ±2.676uA.

[0035] The fixed error of the circuit can be eliminated by calibration and has a small impact. The error caused by temperature drift is the main factor. The temperature drift of the current multiplier circuit based on the operational amplifier LMH6628 is calculated as follows.

[0036] Because operational amplifiers have parasitic parameters such as input offset voltage, input offset current, and input bias current, and the input bias current of operational amplifiers... Input bias current to the non-inverting input of the op-amp and the bias current input to the inverting terminal The average value, i.e. = (5) Input offset current This is the difference between the input bias current at the non-inverting input and the input bias current at the inverting input.

[0037] (6) Equations (17) and (18) are obtained from equations (15) and (16).

[0038] = (7) = (8) The input bias current, input offset current, and input offset voltage of the op-amp are respectively , and Therefore, the circuit model of the current multiplier circuit is shown in the figure below, where U# is an ideal operational amplifier.

[0039] According to Kirchhoff's current law, the following equation is derived: (9) (10) (11) Based on basic circuit knowledge, it is concluded that... (12) = (13) Based on the virtual short principle of operational amplifiers and equations (12) and (13), the following equation is derived: (14) Based on equations (9), (10), (11), and (14), the following equation is derived: (15) in: Due to changes in ambient temperature, This is the operational amplifier offset voltage temperature drift coefficient.

[0040] The input offset voltage drift of the operational amplifier LMH6628 is 5uV / ℃. The greatest variation occurs due to ambient temperature. It is 20℃. With a value of 50Ω, the current error caused by temperature change is 2uA, which meets the current error requirement.

[0041] 2) HDL layout and routing control Use placement and routing tools to adjust the delay time of each delay level, and use timing analysis tools to confirm the adjustment results. Since the delay time of the standard delay cell is related to the device's speed class, operating temperature, and voltage, it is only necessary to control the line delay between standard delay cells, the line delay from the standard delay cell to the D flip-flop, and the line delay from the clock to the D flip-flop.

[0042] To ensure consistent line delays among standard delay cells, place all standard delay cells close together using a place-and-route tool; to ensure consistent line delays from standard delay cells to D flip-flops, place standard delay cells and D flip-flops close together using a place-and-route tool; to ensure that the rising and falling edges of the DDR clock sample data at the same location, place two D flip-flops close together using a place-and-route tool; the line delay from clock to D flip-flops is guaranteed through a global clock network.

[0043] After completing the layout and routing adjustments, use timing analysis tools to confirm the timing of each path from DATA to D flip-flops DFFP1~DFFPn and DFFN1~DFFNn, ensuring that the delay time increases after each delay stage and that the total delay time is greater than one DDR clock cycle.

[0044] By delaying the insertion and controlling the delay time, the taps at each delay level have the characteristics of equal and monotonically increasing delay time, and the tap data can be further processed to complete the data alignment operation.

[0045] 2. Temperature control simulation A simulation model of the current multiplier circuit was established using Saber software to simulate the working process of a temperature-controlled tunable laser. The input current waveform was set to 0~20mA with a period of 10ms. The simulation results show that the output current of the current multiplier circuit is twice the input current, and the response speed of the current multiplier circuit meets the driving requirements of the laser.

[0046] To test and verify the current system, the FPGA unit operated in calibration mode and provided the input digital quantity of the first channel temperature control via RS422 communication. The voltage drop of the first channel temperature control output current across a 10.0Ω resistor to ground was measured, and its current value was calculated. The test results are shown in the table below.

[0047] Table 2 Test Results of Temperature Control System

[0048] Table 2 shows that the output current range of the temperature control system meets the requirements of the S7500 laser. Due to the offset in the above formula, the output current value has zero bias when the input digital value is 0. This effect can be eliminated through calibration. The proportional coefficient is consistent with the theoretical value, and the goodness of fit R is good. 2=1 indicates that the linearity of the temperature control system is very good.

[0049] This invention employs a high-precision AD chip to acquire temperature data, which is then directly injected into the temperature control module of an S7500 laser. The temperature target is discretized, and a discrete PI algorithm is used to transform the single target object into a dual object: the target temperature and the temperature control PWM wave. Through continuous temperature feedback, real-time temperature control tuning of the temperature data and PWM wave is achieved, resulting in high-precision temperature control.

[0050] This invention implements a discrete PI temperature control method using HDL. Because it does not use high-performance IP cores, it has lower requirements for the FPGA's system clock and performance. This invention achieves discretization of the PI algorithm by inserting standard delay units such as combinational logic, carry chains, or BUFs into the data channel. The temperature control result of this algorithm is no less than one clock cycle.

[0051] This invention uses rising-edge and falling-edge sensitive D flip-flops to sample data at each stage after passing through a standard delay unit. By constraining the positions of the standard delay unit and the D flip-flops, the discretization accuracy of the algorithm is guaranteed.

[0052] This invention uses a shift register controlled by a DDR accompanying clock to perform serial-to-parallel conversion on the data after each delay stage. By judging the results of the serial-to-parallel conversion at each stage, the stability of the conversion result at each stage is detected. The stable serial-to-parallel conversion results at each stage are analyzed to obtain the delay stages where stable data changes. Then, based on the stable data characteristics output from these delay stages, the data sampling edges based on the DDR accompanying clock are selected from the delay stages, and the data sampling center is calculated to complete data alignment.

[0053] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

[0054] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A high-precision discrete PI temperature control method suitable for S7500 lasers, characterized in that, include: Determine the input temperature value, set the temperature value, and define the heating capacity (UPVL) and cooling capacity (HIVL). Calculate the temperature difference based on the input temperature value and the set temperature value; Calculate the PI conversion median based on the temperature difference and discrete KP values; Update the temperature control discrete PI value based on the temperature difference, discrete KI value, and PI conversion median. Based on the updated temperature control discrete PI value and heating capacity, calculate the duty cycle setting value and temperature discrete PI value at the current moment; Calculate the PWM output at the current moment based on the current duty cycle setting value; Based on the temperature discrete PI value and heating capacity, the laser temperature control direction signal at the current moment is obtained, and the laser drive power signal is output to drive the laser output.

2. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that, The temperature difference is calculated based on the input and set temperature values, specifically as follows: When the input temperature value is greater than the set temperature value: PI_ERR_TEMP = FEED_VALUE - SET_VALUE; When the set temperature value is greater than the input temperature value: PI_ERR_TEMP = SET_VALUE - FEED_VALUE; Where PI_ERR_TEMP is the temperature difference, FEED_VALUE is the input temperature value, and SET_VALUE is the set temperature value.

3. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that: Based on the temperature difference and discrete KP values, the PI transformation median is calculated as follows: PI_KP_REG = Data_Kp * PI_ERR_TEMP; Wherein, PI_KP_REG is the median of the PI conversion, Data_Kp is the discrete KP value, and PI_ERR_TEMP is the temperature difference value.

4. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that, Based on the temperature difference, discrete KI value, and PI conversion median, update the temperature control discrete PI value as follows: When the input temperature value is greater than the set temperature value: PI_KI_REG = PI_KI_MID + Data_Kit*PI_ERR_TEMP; When the input temperature value is lower than the set temperature value: PI_KI_REG = PI_KI_MID - Data_Kit*PI_ERR_TEMP; Wherein, PI_KI_REG is the discrete PI value for temperature control, PI_KI_MID is the median of the PI conversion, Data_Kit is the discrete KI value, and PI_ERR_TEMP is the temperature difference value.

5. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that, The step of calculating the duty cycle setting and temperature discrete PI value at the current moment based on the updated temperature control discrete PI value and heating capacity is as follows: TEC_PWM_PI = PI_KI_REG + PI_KP_REG; PWM_REAL = TEC_PWM_PI-UPVL; Wherein, PWM_REAL is the duty cycle setting value at the current moment; UPVL is the heating capacity; PI_KI_REG is the discrete PI value for temperature control; PI_KP_REG is the median value of PI conversion; and TEC_PWM_PI is the discrete PI value for temperature.

6. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that, The process of calculating the PWM output at the current moment based on the current duty cycle setting value is as follows: When the duty cycle setting value is greater than the actual PWM output period, the PWM output is 1; when the duty cycle setting value is less than the actual PWM output period, the PWM output is 0.

7. The high-precision discrete PI temperature control method for S7500 lasers according to claim 1, characterized in that, The laser temperature control direction signal at the current moment is obtained based on the temperature discrete PI value and the heating capacity, specifically as follows: When the temperature discrete PI value is greater than the heating capacity UPVL, the temperature control direction signal is set to 0. When the temperature discrete PI value is less than the heating capacity UPVL, the temperature control direction signal is set to 1.

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