A method and system for controlling a fourier infrared spectrometer

Abstract

The application discloses a control method system of a Fourier infrared spectrometer, and belongs to the technical field of spectrum analysis instrument control, and comprises the following steps: calibrating the peak-to-valley value and the average value of the driving voltage of a voice coil motor; in a motion cycle of the spectrometer, laser frequency is collected, the collected value is compared with a preset value, a control amount is obtained according to preset parameters, and the control amount is output to a driving system to drive the motor to move; the strategy provided by the application is suitable for motor control under different spectral resolutions, that is, under different spectral resolution settings, the required data amount for spectrum calculation can be met, meanwhile, the uniformity of the moving mirror motion speed in the effective stroke of the motor is ensured, and the quality of the infrared spectrum signal is improved.

Description

Technical Field

[0001] This invention relates to the field of spectral analysis instrument control technology, specifically to a control method and system for a Fourier transform infrared spectrometer. Background Technology

[0002] Fourier transform infrared spectrometers generate optical path difference through the movement of a moving mirror, simultaneously modulating laser and infrared radiation. The distance of the moving mirror's movement is proportional to the optical path difference, and the magnitude of the optical path difference is the main factor affecting spectral resolution.

[0003] Due to delays in various components, traces, or filters within the circuitry, when the moving mirror of the spectrometer moves at an unstable speed, even when sampling is performed using a laser as a scale standard, differences in optical path difference will occur at each sampling point, thus reducing the instrument's signal-to-noise ratio (SNR). Furthermore, if a DLaTGS (deuterated L-alanine sulfate triglycinate) detector, which is more sensitive to frequency response, is used, the SNR will decrease further when the speed is unstable.

[0004] Resolution and signal-to-noise ratio are crucial parameters for Fourier transform spectrometers. Therefore, controlling the smooth movement of the moving mirror is essential to improve the quality of the spectral signal. Furthermore, depending on the spectral resolution requirements of the targets being detected in different applications, the instrument needs to have adjustable resolution capabilities. These issues urgently require solutions; therefore, a control method for a Fourier transform infrared spectrometer is proposed. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to control the smooth movement of the moving mirror and improve the quality of the spectral signal, and a control method for a Fourier transform infrared spectrometer is provided.

[0006] The present invention solves the above-mentioned technical problems through the following technical solution, and the present invention includes the following steps:

[0007] Step 1: Calibrate the peak value Umax and valley value Umin of the driving voltage of the voice coil motor;

[0008] Step 2: Calibrate the average value of the voice coil motor's drive voltage, Uaver;

[0009] Step 3: Within one motion cycle, the motor is driven from a standstill to the "start acceleration position" and then to the "working speed position" according to the calibrated drive voltage valley value Umin and the preset control quantity Δu1. Here, the preset control quantity Δu1 is the preset drive voltage value output.

[0010] Step 4: When the moving mirror reaches the "working speed position", the laser frequency is collected. The collected laser frequency value is compared with the preset value to obtain the error term in the incremental PID algorithm. Then, the control quantity is obtained according to the incremental PID algorithm and the preset parameters, which drives the voice coil motor to move the moving mirror at a constant speed within the sampling interval. The control quantity is a digital signal. The preset parameters include the P parameter, I parameter, D parameter and output limit Δu_limit in the incremental PID algorithm.

[0011] Step 5: When the moving mirror moves at a constant speed to the "start deceleration position", the motor is controlled to start deceleration according to the calibrated peak value of the drive voltage until it "decelerates to zero position";

[0012] Step 6: When the moving mirror decelerates to the "deceleration to zero position", the motor is controlled to return to the "start acceleration position" according to the calibrated peak value of the drive voltage Umax and the preset control quantity Δu2. The preset control quantity Δu2 is the preset drive voltage value of the output.

[0013] Step 7: Repeat Steps 3 through 6 to complete the next cycle of exercise.

[0014] Furthermore, Step 1 specifically includes the following process:

[0015] S11: Collect the driving voltage of the voice coil motor, take the interval between adjacent driving voltage peaks and valleys as a period, and collect the rising edge of the laser interference signal within the period. The number of rising edges corresponds to the total travel of the moving mirror and also to the effective travel of the motor. One rising edge corresponds to one signal point.

[0016] S12: Determine whether the current effective stroke of the voice coil motor under the preset peak-valley driving voltage parameters meets the data volume requirements for spectral calculation; if not, proceed to step S13.

[0017] S13: Determine whether the effective stroke of the voice coil motor is less than the minimum data volume required by the nominal resolution. If so, increase the peak and valley values ​​of the drive voltage of the voice coil motor; if not, decrease the peak and valley values ​​of the drive voltage of the voice coil motor; and then calibrate the current peak and valley values ​​of the drive voltage.

[0018] Furthermore, in step S11, the current optical path difference, i.e., the effective stroke S of the motor, is calculated based on the number of signal points in the laser interferogram within the target period. The specific calculation formula is as follows:

[0019] S = n * λ;

[0020] Where n is the number of signal points in the laser interferogram within the target period, λ is the laser wavelength, and the laser interferogram is the set of signal points ordered from 1 to n.

[0021] Further, in the step S12, the effective stroke S of the motor is within a preset swing distance range [S1, S2].

[0022] Further, in the step S13, if S<S1, the peak-to-valley value of the driving voltage is increased; if S>S2, the peak-to-valley value of the driving voltage is decreased, such that S1<S<S2.

[0023] Further, the Step 2 specifically comprises the following processes:

[0024] S21: selecting the highest point of the infrared interference signal in a cycle as the "zero optical path difference position", determining whether the "zero optical path difference position" is within the middle position range of the effective stroke of the motor; if not, jumping to step S22;

[0025] S22: determining whether the "zero optical path difference position" is earlier than the minimum value of the middle position range of the effective stroke of the motor; if yes, decreasing the average value of the driving voltage of the voice coil motor; if not, increasing the average value of the driving voltage of the voice coil motor; until the "zero optical path difference position" is within the middle position range of the effective stroke of the motor, and then calibrating the current average value of the driving voltage.

[0026] Further, in the step S21, the middle region of the laser interferogram in the target cycle is set as wherein Δ is an allowable deviation, and n is the number of signal points of the laser interferogram in the target cycle.

[0027] 8. The control method of a Fourier transform infrared spectrometer according to claim 7, characterized in that, in the step S22, if that is, the zero optical path difference point appears earlier than the middle region of the laser interferogram in the target cycle, and the average value of the driving voltage is decreased at this time; if that is, the zero optical path difference point appears later than the middle region of the laser interferogram in the target cycle, and the average value of the driving voltage is increased at this time; wherein n0 is the position of the zero optical path difference point.

[0028] Further, in one working cycle, the movement of the voice coil motor is divided into forward movement and reverse movement: the process in which the driving voltage increases from a valley value to a peak value according to a set rule corresponds to the forward movement, and the process in which the driving voltage decreases from a peak value to a valley value according to a set rule corresponds to the reverse movement, and infrared signals are only collected during the forward movement;

[0029] wherein, the forward movement process is as follows:

[0030] the calibrated driving voltage valley value corresponds to the "starting acceleration position" of the voice coil motor during forward movement; the voice coil motor accelerates from a standstill at the "starting acceleration position" to perform forward movement, and accelerates to the working speed at the "working speed position" before the "sampling start position";

[0031] The voice coil motor maintains a constant speed at the operating speed in the "operating speed position" and the "start deceleration position";

[0032] The calibrated peak drive voltage corresponds to the "start deceleration position". The voice coil motor decelerates to zero after passing through the "start deceleration position", which is the "deceleration to zero position".

[0033] The reverse motion process is as follows:

[0034] After the voice coil motor decelerates to zero during forward motion, it naturally returns to the "starting acceleration position," which corresponds to the "starting deceleration position" during forward motion.

[0035] The voice coil motor moves from the "start acceleration position" to the "start deceleration position". The "start deceleration position" of the reverse movement corresponds to the "start acceleration position" of the forward movement.

[0036] After the voice coil motor decelerates to zero in the reverse motion, it reaches the "stop position" and then naturally returns to the "start acceleration position" of the forward motion.

[0037] This invention also provides a control system for a Fourier transform infrared spectrometer, which uses the above-mentioned control method to control the movement of the voice coil motor of the Fourier transform infrared spectrometer, that is, to control the movement of the moving mirror. The system includes: a laser detection circuit, a shaping circuit, an MCU, a D / A conversion circuit, a voltage offset circuit, a power amplifier circuit, and a voice coil motor. The laser detection circuit, the shaping circuit, the MCU, the D / A conversion circuit, the voltage offset circuit, the power amplifier circuit, the voice coil motor, and the voice coil motor coil are connected in sequence. The voice coil motor coil and the moving mirror are connected to the same swing arm, wherein the voice coil motor coil is the voice coil motor mover.

[0038] Each cycle of the spectrometer includes the following motion processes:

[0039] A: At the “start acceleration position” of each cycle, the MCU outputs a digital signal U(n) to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to accelerate to the “working speed position”. Here, the digital signal U(n) = Umin + n*Δu1;

[0040] B: The laser detection circuit and shaping circuit output a laser interference square wave to the MCU. The MCU measures the period of the laser interference square wave through an internal counter and converts it into a frequency. This frequency is used to characterize the speed of the motor. When the moving mirror moves to the "working speed position", the MCU outputs a uniform speed digital signal U(n+1) to the D / A conversion circuit according to the incremental PID algorithm. The D / A conversion circuit converts the uniform speed digital signal into a uniform speed analog signal. The uniform speed analog signal is converted into a uniform speed positive and negative voltage by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to move at a uniform speed within the sampling interval. Here, the uniform speed digital signal U(n+1) = U(n) + Δu, where Δu is the digital increment output by the incremental PID algorithm.

[0041] C: When the moving mirror moves at a constant speed to the "start deceleration position", the MCU outputs a digital signal to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit. After passing through the power amplifier circuit, it drives the voice coil motor to move. The voice coil motor drives the moving mirror to decelerate to the "deceleration to zero position". The digital signal is the peak value of the driving voltage Umax.

[0042] D: When the moving mirror moves at a constant speed to the "deceleration to zero position", the MCU outputs a digital signal U(n) to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to the "start acceleration position" and can enter the next cycle. The digital signal U(n) is Umax-n*Δu2.

[0043] Compared with the prior art, the present invention has the following advantages: the control method of the Fourier transform infrared spectrometer determines the effective stroke of the motor under different resolutions of the spectrometer by calibrating the motion control parameters of the instrument; the proposed strategy is applicable to motor control under different spectral resolutions, that is, under different spectral resolution settings, it can meet the data volume required for spectral calculation, while ensuring the uniformity of the moving mirror speed within the effective stroke of the motor, thereby improving the quality of the infrared spectral signal. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the Fourier transform infrared spectrometer in Embodiment 1 of the present invention;

[0045] Figure 1 In the middle: 1 is a fixed mirror, 2 is a fixed mirror, 3 is a beam splitter, 4 is a compensator, 5 is a laser, 6 is a laser detector, 7 is a moving mirror, 8 is a moving mirror, 9 is a rotating shaft, 10 is a voice coil motor mover, and 11 is a voice coil motor stator.

[0046] Figure 2 This is a schematic diagram of the forward motion of the motor in Embodiment 1 of the present invention;

[0047] Figure 3 This is a schematic diagram of the reverse motion of the motor in Embodiment 1 of the present invention;

[0048] Figure 4 This is a flowchart illustrating the control method of the Fourier transform infrared spectrometer in Embodiment 1 of the present invention;

[0049] Figure 5 This is a schematic diagram of the control system of the Fourier transform infrared spectrometer in Embodiment 2 of the present invention;

[0050] Figure 5 In the diagram, 1 is the laser detection circuit, 2 is the shaping circuit, 3 is the MCU, 4 is the D / A conversion circuit, 5 is the voltage offset circuit, 6 is the power amplifier circuit, and 7 is the voice coil motor. Detailed Implementation

[0051] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0052] Example 1

[0053] like Figures 1-4 As shown, this embodiment provides a technical solution: a control method for a Fourier transform infrared spectrometer, including...

[0054] like Figure 1 As shown, the spectrometer in this embodiment mainly includes a fixed mirror 1, a fixed mirror 2, a beam splitter 3, a compensation plate 4, a laser 5, a laser detector 6, a moving mirror 7, a moving mirror 8, a rotating shaft 9, a voice coil motor mover 10, and a voice coil motor stator 11. The voice coil motor mover 10 extends into the voice coil motor stator 11. When a periodic voltage signal is applied to the voice coil motor mover 10, the voice coil motor mover 10 will be subjected to electromagnetic force to drive the swing arm and the moving mirrors 7 and 8 at both ends of the swing arm to swing back and forth around the rotating shaft 9 at a small angle.

[0055] It should be noted that the moving part of the spectrometer in this embodiment includes a swing arm and moving mirrors (i.e., moving mirror 7 and moving mirror 8) fixed on the swing arm. The voice coil motor mover 10 is connected to the swing arm and drives the swing arm to rotate around the rotating shaft 9.

[0056] The working principle of the spectrometer in this embodiment is as follows:

[0057] The laser emitted from the laser 5 passes through the beam splitter 3 and the compensation plate 4, and is split into two laser beams. The two laser beams are reflected by the fixed mirrors 2 and 1 to the moving mirrors 7 and 8 respectively. The laser reaching the moving mirrors 7 and 8 is offset by a certain distance on the moving mirrors 7 and 8, then returns to the beam splitter 3 along the original direction via the fixed mirrors 2 and 1. After passing through the beam splitter 3 again, the two laser beams are combined into laser interference light, wherein half of the laser interference light returns to the laser 5, and the other half is received by the laser detector 6. When the swing arm swings around the rotating shaft 9, the moving mirrors 7 and 8 swing accordingly, and the intensity of the laser interference light changes in a sine wave with the optical path difference.

[0058] The laser wavelength can be calculated through the period of the laser interference signal. The laser interference signal and the infrared interference signal are collected, and the highest point of the infrared interference signal synchronized with the laser interference signal is taken as the zero optical path difference position. In order to precisely control the swing of the moving mirrors and meet the requirements of different spectral resolutions for the amount of infrared interference data, it is necessary to calibrate the peak value of the driving voltage Umax, the valley value of the driving voltage Umin, and the average value of the driving voltage Uaver of the motor (all motors mentioned below refer to voice coil motors).

[0059] The control method for the Fourier transform infrared interferometer of this embodiment includes the following steps:

[0060] (1) Collect the motor driving voltage, take the interval between adjacent peak values and valley values of the driving voltage as one cycle, collect rising edges of the laser interference signal in the cycle at the same time, the number of rising edges (the laser interference signal is a square wave, the rising edge is the rising edge of the square wave signal, corresponding to one signal point) is the total stroke of the corresponding moving mirror, and also corresponds to the effective stroke of the motor.

[0061] Specifically, the current optical path difference S (proportional to the stroke) is calculated according to the number of signal points in the laser interferogram within the target cycle as follows:

[0062] S=n*λ;

[0063] Wherein, n is the number of signal points of the laser interferogram within the target cycle, λ is the laser wavelength, and the laser interferogram is a set of signal points sorted from 1 to n.

[0064] (2) Determine whether the current effective stroke of the motor meets the data volume requirement for spectral calculation under the preset driving voltage peak-valley parameter; if not, jump to step (3);

[0065] Specifically, the data points (that is, the aforementioned signal points) shall conform to the motor stroke required by the preset resolution of the spectrometer, that is, the effective motor stroke S is within the preset swing distance interval [S1, S2].

[0066] When the above judgment result is negative, there are two situations: the first is S<S1, and the second is S>S2, so the next judgment is performed.

[0067] (3) determining whether the effective stroke of the motor is less than the minimum data volume required by the nominal resolution; if yes, increasing the peak-to-valley value of the driving voltage of the motor; if no, decreasing the peak-to-valley value of the driving voltage of the motor; calibrating the current peak-to-valley value of the driving voltage of the motor;

[0068] Specifically, if S<S1, the peak-to-valley value of the driving voltage signal shall be increased; if S>S2, the peak-to-valley value of the driving voltage signal shall be decreased, so that S1<S<S2.

[0069] (4) selecting the highest point of the infrared interference signal within a period as the "zero optical path difference position", determining whether the "zero optical path difference position" is within the middle position range of the effective stroke of the motor; if not, jumping to step (5);

[0070] Wherein, the position n0 of the zero optical path difference point shall be located near the middle of the laser interferogram to meet the requirement. Specifically, the middle area of the laser interferogram in the target period is set as wherein Δ is the allowable deviation, and n is the number of signal points of the laser interferogram in the target period;

[0071] When the above judgment result is negative, there are two cases as follows: the first one is the second one is proceed with the next judgment:

[0072] (5) determining whether the "zero optical path difference position" is earlier than the minimum value of the middle position range of the effective stroke of the motor; if yes, decreasing the average value of the driving voltage; if no, increasing the average value of the driving voltage. Until the "zero optical path difference position" is within the middle position range of the effective stroke of the motor, calibrate the current average driving voltage Uaver.

[0073] Specifically, if that is, the zero optical path difference point appears earlier than the middle area of the laser interferogram in the target period, and the average driving voltage is decreased at this time; if that is, the zero optical path difference point appears later than the middle area of the laser interferogram in the target period, and the average driving voltage is increased at this time.

[0074] Through the above steps, the calibration of the motor control parameters of the spectrometer is completed. The motor movement is divided into forward direction and reverse direction. The process in which the driving voltage increases from the valley value to the peak value according to a certain rule corresponds to forward movement, and the process in which the driving voltage decreases from the peak value to the valley value according to a certain rule corresponds to reverse movement. Infrared signals are only collected during forward movement, and the motor continuously circulates according to "forward-reverse-forward-reverse...";

[0075] In this embodiment, the forward movement process of the motor is as follows:

[0076] The calibrated motor drive voltage valley value corresponds to the "start acceleration position" when the motor is moving in the forward direction. The motor accelerates from the "start acceleration position" from a standstill to move in the forward direction, and accelerates to the motor working speed at the "working speed position" before the "sampling start position".

[0077] The motor maintains a constant speed at the operating speed in the "operating speed position" and the "start deceleration position";

[0078] The calibrated peak drive voltage corresponds to the "start deceleration position". The motor decelerates to zero after passing through the "start deceleration position", which is the "deceleration to zero position".

[0079] In this embodiment, the reverse motion of the motor is as follows:

[0080] After the motor decelerates to zero during forward motion, it naturally returns to the "starting acceleration position," which corresponds to the "starting deceleration position" during forward motion.

[0081] The motor moves from the "start acceleration position" to the "start deceleration position". The "start deceleration position" of the reverse movement corresponds to the "start acceleration position" of the forward movement.

[0082] After the motor decelerates to zero in the reverse direction, it reaches the "stop position" and then naturally returns to the "start acceleration position" in the forward direction.

[0083] At this point, the motor has completed one motion cycle. After returning to the "start acceleration position" for forward motion, the motor continues to repeat the above steps.

[0084] Within one motion cycle, with the signal at the "zero optical path difference position" as the center, laser and infrared interferometric data required for the corresponding spectral resolution are extracted to the left and right for spectral calculation. The left and right extraction positions correspond to the "sampling start position" and "sampling end position".

[0085] It should be noted that the calibrated motor drive voltage valley value corresponds to the motor's "start acceleration position". The motor starts accelerating from a standstill, accelerates to the target speed before reaching the "sampling start position", and then enters a constant speed state.

[0086] The calibrated peak drive voltage corresponds to the "start deceleration position". After reaching the "start deceleration position", the motor begins to decelerate to zero.

[0087] After decelerating to zero, the motor drive voltage decreases to the valley value of the drive voltage according to preset parameters, and the motor returns to the "start acceleration position".

[0088] (6) Within one motion cycle, the motor is driven from standstill to working speed according to the calibrated drive voltage valley value Umin and the preset control quantity Δu1; the preset control quantity Δu1 is specifically the preset drive voltage value output, which is a fixed value.

[0089] (7) When the moving mirror reaches the "working speed position", the motor is controlled to move at a constant speed within the sampling interval according to the incremental PID algorithm and preset parameters. The preset parameters include the P parameter, I parameter, D parameter and output limit Δu_limit in the incremental PID algorithm (to prevent the output from being too large).

[0090] (8) Control the motor to return to the “start acceleration position” according to the calibrated peak value of the drive voltage Umax and the preset control quantity Δu2; the preset control quantity Δu2 is the preset drive voltage value of the output, which is a fixed value;

[0091] (9) Repeat steps (6) to (8) to make the moving mirror continuously cycle in the "forward-reverse" direction.

[0092] Example 2

[0093] like Figure 5 As shown, this embodiment provides a control system for a Fourier transform infrared spectrometer, used to control the movement of the voice coil motor of the Fourier transform infrared spectrometer using the control method in Embodiment 1, that is, to control the movement of the moving mirror. The system includes a laser detection circuit 1, a shaping circuit 2, an MCU 3, a D / A conversion circuit 4, a voltage offset circuit 5, a power amplifier circuit 6, and a voice coil motor 7. The laser detection circuit 1 is connected to the shaping circuit 2, the shaping circuit 2 is connected to the MCU 3, the MCU 3 is connected to the D / A conversion circuit 4, the voltage conversion circuit 4 is connected to the voltage offset circuit 5, the voltage offset circuit 5 is connected to the power amplifier circuit 6, and the power amplifier circuit 6 is connected to the coil of the voice coil motor 7 (the coil of the voice coil motor 7 is the voice coil electronic mover). The coil of the voice coil motor 7 and the moving mirror are connected to the same swing arm.

[0094] In this embodiment, the laser detection circuit 1 is used to emit laser light and receive laser interference signals; the shaping circuit 2 is used to shape the laser interference signals into square waves; the MCU 3 is used to control the movement of the voice coil motor, receive the square waves output by the shaping circuit 2, calculate the movement speed of the voice coil motor 7 through a counter, and output digital signals to the D / A conversion circuit 4; the D / A conversion circuit converts the digital signals output by the MCU 3 into analog signals; the voltage offset circuit 5 converts the positive voltage output by the D / A conversion circuit into the positive and negative voltages required to control the movement of the voice coil motor 7; the power amplifier circuit 6 is used to amplify the voltage to the range required for the operation of the voice coil motor 7; the voice coil motor 7 is used to receive the control voltage output by the power amplifier circuit 6 and move accordingly according to the direction and magnitude of the voltage.

[0095] Each cycle of the spectrometer includes the following motion steps:

[0096] At the “start acceleration position” of each cycle, MCU3 outputs a digital signal (U(n)=Umin+n*Δu1) to D / A conversion circuit 4. D / A conversion circuit 4 converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltage by voltage offset circuit 5, and then drives voice coil motor 7 to move after passing through power amplifier circuit 6. Voice coil motor 7 drives moving mirror to accelerate to the “working speed position”.

[0097] The laser detection circuit 1 and shaping circuit 2 output a laser interference square wave to the MCU3. The MCU3 measures the period of the laser interference square wave through an internal counter and converts it into a frequency. This frequency is used to characterize the speed of the motor. When the moving mirror moves to the "working speed position", the MCU3 outputs a uniform digital signal (U(n+1)=U(n)+Δu) to the D / A conversion circuit 4 according to the incremental PID algorithm. The D / A conversion circuit 4 converts the uniform digital signal into a uniform analog signal. The uniform analog signal is converted into a uniform positive and negative voltage by the voltage offset circuit 5, and then drives the voice coil motor 7 to move after passing through the power amplifier circuit 6. The voice coil motor 7 drives the moving mirror to move at a uniform speed within the sampling interval.

[0098] The incremental PID algorithm formula is as follows:

[0099] Δu[n]=K p {e[n]-e[n-1]}+K i e[n]+K d {e[n]-2e[n-1]+e[n-2]}

[0100] In the above formula, K p K i K d These are the P parameter, I parameter, and D parameter, respectively; e is the error term; Δu is the digital increment of the output; Δu ≤ Δu_limit.

[0101] When the moving mirror moves at a constant speed to the "start deceleration position", the MCU3 outputs a digital signal (the digital signal is the peak value of the drive voltage Umax) to the D / A conversion circuit 4. The D / A conversion circuit 4 converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit 5, and then drives the voice coil motor 7 to move after passing through the power amplifier circuit 6. The voice coil motor 7 drives the moving mirror to decelerate to the "deceleration to zero position".

[0102] When the moving mirror moves at a constant speed to the "deceleration to zero position", the MCU3 outputs a digital signal (U(n)=Umax-n*Δu2) to the D / A conversion circuit 4. The D / A conversion circuit 4 converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit 5, and then drives the voice coil motor 7 to move after passing through the power amplifier circuit 6. The voice coil motor 7 drives the moving mirror to the "start acceleration position" and begins a new round of movement.

[0103] In summary, the control method for the Fourier transform infrared spectrometer in the above embodiments determines the effective motor stroke at different resolutions of the spectrometer by calibrating the instrument's motion control parameters. The proposed strategy is applicable to motor control at different spectral resolutions, meaning that it can meet the data volume required for spectral calculations under different spectral resolution settings, while ensuring the uniformity of the moving mirror's speed within the effective motor stroke, thereby improving the quality of the infrared spectral signal.

[0104] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A control method for a Fourier transform infrared spectrometer, characterized in that, Comprising the following steps: Step 1: Calibrate the driving voltage peak value Umax and driving voltage valley value Umin of the voice coil motor; Step 2: Calibrate the average driving voltage Uaver of the voice coil motor; Step 3: In one movement cycle, drive the motor from standstill according to the calibrated driving voltage valley value Umin and the preset control quantity Δu1, and accelerate the motor from the "starting acceleration position" to the "working speed position", wherein the preset control quantity Δu1 is a preset driving voltage value for output; Step 4: When the moving mirror reaches the "working speed position", collect the laser frequency, compare the collected value of the laser frequency with a preset value to obtain an error term in the incremental PID algorithm, then obtain a control quantity according to the incremental PID algorithm and preset parameters, and drive the voice coil motor to drive the moving mirror to move uniformly within the sampling interval, wherein the control quantity is a digital signal, and the preset parameters include the P parameter, I parameter, D parameter and output limit Δu_limit in the incremental PID algorithm; Step 5: When the moving mirror moves uniformly to the "starting deceleration position", control the motor to start decelerating according to the calibrated driving voltage peak value until reaching the "deceleration to zero position"; Step 6: When the moving mirror decelerates to the "deceleration to zero position", control the motor to return to the "starting acceleration position" according to the calibrated driving voltage peak value Umax and the preset control quantity Δu2, wherein the preset control quantity Δu2 is a preset driving voltage value for output; Step 7: Repeat Step 3 to Step 6 to complete the movement of the next cycle.

2. The control method for a Fourier transform infrared spectrometer according to claim 1, characterized in that, In said Step 1, specifically comprises the following process: S11: Collect the driving voltage of the voice coil motor, take the interval between adjacent driving voltage peak values and driving voltage valley values as one cycle, and meanwhile collect the rising edges of laser interference signals in the cycle, the number of rising edges is the total stroke of the corresponding moving mirror, which also corresponds to the effective stroke of the motor, and one rising edge corresponds to one signal point; S12: Determine whether the current effective stroke of the voice coil motor meets the data volume requirement required for spectral calculation under the preset driving voltage peak-valley parameters; if not, jump to step S13; S13: Determine whether the effective stroke of the voice coil motor is smaller than the minimum data volume required by the nominal resolution, if yes, increase the driving voltage peak-valley value of the voice coil motor; if no, reduce the driving voltage peak-valley value of the voice coil motor; then calibrate the current driving voltage peak and valley values.

3. The control method for a Fourier transform infrared spectrometer according to claim 2, characterized in that, In said step S11, the current optical path difference, that is, the effective stroke S of the motor, is calculated according to the number of signal points of the laser interferogram in the target cycle, and the specific calculation formula is as follows: S=n*λ; wherein n is the number of signal points of the laser interferogram in the target cycle, λ is the laser wavelength, and the laser interferogram is a set of signal points sorted from 1 to n.

4. The control method for a Fourier transform infrared spectrometer according to claim 3, characterized in that, In said step S12, the effective stroke S of the motor is within a preset swing distance interval [S1, S2].

5. The control method for a Fourier transform infrared spectrometer according to claim 4, characterized in that, In said step S13, if S<S1, increase the driving voltage peak-valley value, if S>S2, reduce the driving voltage peak-valley value, so that S1<S<S2.

6. The control method for a Fourier transform infrared spectrometer according to claim 4, characterized in that, In said Step 2, specifically comprising the following process: S21: Select the highest point of the infrared interference signal within the period as the "zero optical path difference position" and determine whether the "zero optical path difference position" is within the middle position range of the effective stroke of the motor; if not, jump to step S22; S22: Determine whether the "zero optical path difference position" is earlier than the minimum value of the middle position range of the effective stroke of the motor. If yes, decrease the average value of the drive voltage of the voice coil motor; if no, increase the average value of the drive voltage of the voice coil motor until the "zero optical path difference position" is in the middle position range of the effective stroke of the motor, and then calibrate the current average value of the drive voltage.

7. The control method for a Fourier transform infrared spectrometer according to claim 6, characterized in that, In step S21, the central region of the laser interferogram within the target period is set as... Where Δ is the allowable deviation, and n is the number of signal points in the laser interferogram within the target period.

8. The control method for a Fourier transform infrared spectrometer according to claim 7, characterized in that, In step S22, if That is, the zero optical path difference point appears earlier than the middle region of the laser interferogram within the target period, at which point the average driving voltage is reduced; if That is, the zero optical path difference point appears later than the middle region of the laser interferogram within the target period, at which point the average value of the driving voltage is increased; where n0 is the position of the zero optical path difference point.

9. The control method for a Fourier transform infrared spectrometer according to claim 8, characterized in that, Within one working cycle, the movement of the voice coil motor is divided into forward movement and reverse movement. The process of the driving voltage increasing from the valley to the peak value according to the set rule corresponds to the forward movement, and the process of the driving voltage decreasing from the peak value to the valley value according to the set rule corresponds to the reverse movement. Infrared signals are only collected during the forward movement. The forward motion process is as follows: The calibrated drive voltage valley value corresponds to the "start acceleration position" when the voice coil motor moves in the forward direction. The voice coil motor accelerates from the "start acceleration position" from a standstill to move in the forward direction, and accelerates to the working speed at the "working speed position" before the "sampling start position". The voice coil motor maintains a constant speed at the operating speed in the "operating speed position" and the "start deceleration position"; The calibrated peak drive voltage corresponds to the "start deceleration position". The voice coil motor decelerates to zero after passing through the "start deceleration position", which is the "deceleration to zero position". The reverse motion process is as follows: After the voice coil motor decelerates to zero during forward motion, it naturally returns to the "starting acceleration position," which corresponds to the "starting deceleration position" during forward motion. The voice coil motor moves from the "start of acceleration position" to the "start of deceleration position". The "start of deceleration position" of the reverse movement corresponds to the "start of acceleration position" of the forward movement. After the voice coil motor decelerates to zero in the reverse motion, it reaches the "stop position" and then naturally returns to the "start acceleration position" in the forward motion.

10. A control system for a Fourier transform infrared spectrometer, comprising controlling the movement of the voice coil motor of the Fourier transform infrared spectrometer using the control method described in claim 9, i.e., controlling the movement of the moving mirror, characterized in that, include: The laser detection circuit, shaping circuit, MCU, D / A conversion circuit, voltage offset circuit, power amplifier circuit, and voice coil motor are connected in sequence. The voice coil motor coil and the moving mirror are connected to the same swing arm, and the voice coil motor coil is the moving part of the voice coil motor. Each cycle of the spectrometer includes the following motion processes: A: At the "start acceleration position" of each cycle, the MCU outputs a digital signal U(n) to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to accelerate to the "working speed position". Here, the digital signal U(n) = Umin + n*Δu1; B: The laser detection circuit and shaping circuit output a laser interference square wave to the MCU. The MCU measures the period of the laser interference square wave through an internal counter and converts it into a frequency. This frequency is used to characterize the speed of the motor. When the moving mirror moves to the "working speed position", the MCU outputs a uniform speed digital signal U(n+1) to the D / A conversion circuit according to the incremental PID algorithm. The D / A conversion circuit converts the uniform speed digital signal into a uniform speed analog signal. The uniform speed analog signal is converted into a uniform speed positive and negative voltage by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to move at a uniform speed within the sampling interval. Here, the uniform speed digital signal U(n+1) = U(n) + Δu, where Δu is the digital increment output by the incremental PID algorithm. C: When the moving mirror moves at a constant speed to the "start deceleration position", the MCU outputs a digital signal to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit. After passing through the power amplifier circuit, it drives the voice coil motor to move. The voice coil motor drives the moving mirror to decelerate to the "deceleration to zero position". The digital signal is the peak value of the driving voltage Umax. D: When the moving mirror moves at a constant speed to the "deceleration to zero position", the MCU outputs a digital signal U(n) to the D / A conversion circuit. The D / A conversion circuit converts the digital signal into an analog signal. The analog signal is converted into positive and negative voltages by the voltage offset circuit, and then drives the voice coil motor to move after passing through the power amplifier circuit. The voice coil motor drives the moving mirror to the "start acceleration position" and can enter the next cycle. The digital signal U(n) is Umax - n * Δu2.

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