A three-float instrument magnetic suspension control circuit

Abstract

The application discloses a kind of three float instrument magnetic suspension control circuits, and digital signal processor circuit generates PWM square wave;Excitation generation circuit modulates PWM square wave into sinusoidal excitation signal, and sinusoidal excitation signal is output to position detection bridge;Position detection bridge is driven under the action of sinusoidal excitation signal and magnetic suspension coil works;Position detection bridge obtains AC voltage signal for representing the position of magnetic suspension coil, and AC voltage signal is output to signal processing circuit through multiplexed gating switch;Signal processing circuit converts the AC voltage signal input by position detection bridge into DC signal for representing the position of magnetic suspension coil;Digital signal processor circuit obtains force control signal according to DC signal;Force control circuit responds to force control signal, and provides suspension force for magnetic suspension coil.The application realizes the localization, miniaturization of three float instrument magnetic suspension circuit and the rapid, precise control to controlled object.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inertial technology, and particularly relates to a three-float instrument magnetic suspension control circuit. BACKGROUND

[0002] At present, the three-float instrument as a high-precision inertial instrument is widely applied to the inertial navigation of domestic and foreign ballistic missiles and carrier rockets, and mainly comprises a three-float gyroscope and a three-float gyro accelerometer, and adopts air floating, liquid floating and magnetic suspension supporting technologies. The magnetic suspension system detects the position change of the float through the magnetic suspension coil, analyzes the motion state and trend of the float, and controls the float in the middle position of the jewel bearing by applying a direct current to the magnetic suspension coil to generate a magnetic suspension force, so that the float is completely separated from the mechanical contact with the jewel bearing, the interference torque caused by mechanical friction is avoided, and the precision of the three-float instrument is improved.

[0003] At present, the three-float instrument magnetic suspension control circuit disclosed in the prior art needs to use imported devices or devices packaged by imported chips to support functions, and some circuits can be replaced by completely domestic chips, but the 7B698 chip integrated with the excitation generation circuit and the phase-sensitive demodulation circuit cannot be replaced by domestic chips or similar domestic chips, and no chip manufacturer in China can develop this chip. Therefore, the existing three-float instrument magnetic suspension control circuit cannot be directly replaced by domestic chips to achieve complete self-controlling. SUMMARY

[0004] The application aims to overcome the above-mentioned defects, and provides a three-float instrument magnetic suspension control circuit, which solves the technical problem that the existing three-float instrument magnetic suspension control circuit cannot be replaced by domestic chips, and realizes the domestication, miniaturization and rapid and precise control of the controlled object.

[0005] To achieve the above-mentioned application purposes, the application provides the following technical scheme.

[0006] A three-float instrument magnetic suspension control circuit comprises an excitation generation circuit, a position detection bridge, a multi-channel gating switch, a signal processing circuit, a digital signal processor circuit and a force control circuit.

[0007] The digital signal processor circuit generates a PWM square wave and outputs the square wave to the excitation generation circuit.

[0008] The excitation generation circuit receives the PWM square wave input by the digital signal processor circuit, modulates the PWM square wave into a sinusoidal excitation signal, and outputs the sinusoidal excitation signal to the position detection bridge.

[0009] The position detection bridge drives the magnetic suspension coil to work under the action of the sinusoidal excitation signal.

[0010] The position detection bridge obtains an alternating voltage signal for representing the position of the magnetic suspension coil, and outputs the alternating voltage signal to the signal processing circuit through the multiplexing switch.

[0011] The signal processing circuit converts the alternating voltage signal input by the position detection bridge into a direct current signal for representing the position of the magnetic suspension coil, and outputs the direct current signal to the digital signal processing circuit.

[0012] The digital signal processing circuit obtains a force control signal according to the direct current signal, and outputs the force control signal to the force control circuit.

[0013] The force control circuit provides suspension force for the magnetic suspension coil in response to the force control signal.

[0014] Further, the position detection bridge obtains a plurality of differential signals for representing the position of the magnetic suspension coil.

[0015] The digital signal processing circuit controls each of the multiplexing switches to be turned on and off in turn, so that each of the differential signals is input to the signal processing circuit in a set sequence.

[0016] Further, the signal processing circuit comprises a differential amplification circuit and a demodulation circuit. The differential amplification circuit amplifies and differentiates a selected differential signal to obtain a differential-amplified alternating voltage signal, and the selected differential signal is formed by the alternating voltage signals output by two channels of the position detection bridge. The demodulation circuit comprises a phase-sensitive demodulator and a low-pass filter circuit. The phase-sensitive demodulator takes the sinusoidal excitation signal input by the excitation generation circuit as a reference signal, demodulates the differential-amplified alternating voltage signal to obtain a full-half wave alternating signal for representing the position of the magnetic suspension coil, and the low-pass filter circuit filters the full-half wave alternating signal into a direct current signal for representing the position of the magnetic suspension coil.

[0017] Further, the differential amplification circuit is a domestic instrument amplifier ZSAD620TF, and the demodulation circuit is a domestic phase-sensitive demodulator LZX2.

[0018] Further, the digital signal processing circuit comprises a system initialization module, a magnetic suspension position acquisition and processing module, a magnetic suspension force calculation module, an execution magnetic suspension force module, and an RS485 communication module.

[0019] The system initialization module is used for setting a system clock, an interrupt enable, and a multiplexing switch enable.

[0020] The magnetic suspension position acquisition and processing module comprises a PWM square wave generation module, an A / D conversion circuit and a multi-path gating switch control module; the A / D conversion circuit is used for converting a direct current signal input by the signal processing circuit into a digital signal; and the multi-path gating switch control module is used for controlling the gating of the multi-path gating switch;

[0021] The magnetic suspension force calculation module presets a digital range of the center position of the float, i.e. a dead zone, compares the digital signal with the preset dead zone, and obtains a force control signal; the specific method is as follows: if the digital signal is within the dead zone range, it is considered that the float is at the center position, and no force is needed to be executed; if the digital signal is greater than the upper boundary of the dead zone or smaller than the lower boundary of the dead zone, positive or negative force needs to be executed to pull the float to move towards the dead zone; the force size is dynamically adjusted according to the difference value of the digital signal exceeding the boundary of the dead zone, the greater the difference value, the longer the force time in the force period, and the smaller the difference value, the shorter the force time in the force period;

[0022] The magnetic suspension force execution module is used for PWM disconnection and control of the on-off of the force switch; the force control circuit provides PWM disconnection for the magnetic suspension coil during suspension force, controls the force control circuit through the GPIO port according to the force control signal, inputs the force current into the magnetic suspension coil, and generates magnetic pull force to center the float;

[0023] The RS485 communication module is used for communication with the external device.

[0024] Further, the A / D conversion circuit is a 12-bit A / D module built in the digital signal processor circuit;

[0025] The digital signal processor circuit further comprises an A / D input limiting circuit connected between the A / D conversion circuit and the signal processing circuit; the A / D input limiting circuit is composed of two switching diodes, and the input high voltage of the A / D conversion circuit is clamped at 3.3V, and the input low voltage is clamped at 0V.

[0026] Further, the force control circuit comprises ≥10 force switches, each of which is controlled by the force control signal output by the I / O port of the digital signal processor circuit, and the force switch is turned on to realize the conduction of the magnetic suspension coil and the direct current power supply, and the magnetic suspension force is generated.

[0027] Further, the excitation generation circuit comprises a band-pass filter circuit and a voltage follower;

[0028] The band-pass filter circuit is used for modulating the PWM square wave into a sine wave excitation signal, and the voltage follower is used for stabilizing the sine wave excitation signal and preventing it from being affected by the load behind;

[0029] The resistance and capacitance in the band-pass filter circuit are determined according to the actual demand of the sine wave excitation signal parameters.

[0030] Furthermore, the bandpass filter circuit is an active second-order bandpass filter;

[0031] An active second-order bandpass filter includes resistors R1, R2, and R3, and capacitors C1 and C2;

[0032] Assume the required parameters for the sinusoidal excitation signal include the amplification factor A. u Quality factor Q, center frequency f0, bandwidth B w The resistors R1, R2, R3 and the capacitors C1 and C2 are calculated according to the following formula:

[0033]

[0034]

[0035]

[0036]

[0037] Where C = C1 = C2.

[0038] Furthermore, the operational amplifier in the bandpass filter circuit is a four-channel integrated operational amplifier FX147BH(Z), and one channel of the FX147BH(Z) is used to form a voltage follower for the AC excitation signal.

[0039] The digital signal processor circuit adopts the domestic DSP controller JDSPF2812A, and uses the crystal oscillator JA120-30MHz as the clock source of the digital signal processor circuit. The frequency divider circuit in the digital signal processor circuit generates a 12kHz clock, and the event manager module EVA in the digital signal processor circuit outputs a 12kHz PWM square wave.

[0040] The digital signal processor circuit has an on-chip FLASH memory, with 9 sectors A, C to J used to store the magnetic levitation control software, and sector B dedicated to storing the magnetic levitation parameters.

[0041] Compared with the prior art, the present invention has at least one of the following advantages:

[0042] (1) This invention creatively proposes a three-float instrument magnetic levitation control circuit, which replaces the imported or pseudo-domestic LVDT signal conditioner used in the current conventional scheme with a newly designed functional circuit, realizing the complete localization of all materials of the three-float instrument magnetic levitation control circuit, and getting rid of the dependence on imported components and pseudo-empty package components.

[0043] (2) The magnetic levitation control circuit of the present invention can realize fast and accurate control of the position of the float of the three-float instrument. In particular, the frequency of the excitation signal is determined by the frequency division circuit and crystal oscillator of the digital signal processor circuit. The high stability of the clock gives the excitation signal frequency high stability, which is much higher than the excitation signal generated by the LVDT signal conditioner in the conventional scheme.

[0044] (3) The magnetic levitation control circuit of the present invention takes into account all user needs of the prior art. Under the condition that the printed circuit board size remains unchanged, it is compatible with the existing tasks and multiple types of three-float instrument magnetic levitation control circuits. It is applicable to multiple models, realizes shelf-style productization, and promotes the productization of three-float instruments.

[0045] (4) The present invention achieves a highly simplified design. Due to the replacement of the 7B698 chip with a newly designed functional circuit and the increase in package size of the booster circuit by 3 times, the circuit board space becomes a problem. By using a four-channel integrated operational amplifier, a built-in A / D conversion module of the digital signal processor circuit to replace the single-chip A / D conversion circuit, a multi-channel analog switch, and an on-chip memory of the digital signal processor circuit to replace the off-chip memory, the circuit size is significantly reduced, and the problems of poor built-in A / D conversion accuracy and limited input signal are solved. Attached Figure Description

[0046] Figure 1 This is a structural block diagram of a fully domestically produced three-float instrument magnetic levitation control circuit in an embodiment of the present invention;

[0047] Figure 2 This is a schematic diagram of a magnetic levitation circuit control process in an embodiment of the present invention;

[0048] Figure 3 This is a schematic diagram of an active second-order bandpass filter in an embodiment of the present invention. Detailed Implementation

[0049] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0050] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0051] Currently available magnetic levitation technology solutions all mention or do not mention several essential components that are either imported or pseudo-empty components. This invention replaces the imported or pseudo-domestic LVDT signal conditioners used in conventional solutions for excitation generation, signal demodulation, and DC signal output by designing a new functional circuit. This invention is the first to solve the problem that the bare core of the LVDT signal conditioner is limited by foreign technology.

[0052] This invention provides a fully domestically produced magnetic levitation control circuit for a three-float instrument. Through a novel design of an independently developed excitation signal generation circuit and demodulation circuit, it replaces imported chips or pseudo-empty package chips with functional circuitry. This achieves complete domestic production of the magnetic levitation circuit while ensuring the accuracy and reliability of magnetic levitation control, solving the problem of being constrained by foreign chips. Furthermore, through simplified design, the magnetic levitation circuit is made with fewer components and a smaller size, laying the foundation for the miniaturization of three-float instruments.

[0053] This invention provides a magnetic levitation control circuit for a three-float instrument, comprising: an excitation generation circuit 1, a position detection bridge 2, a multiplexer switch 3, a signal processing circuit 4, a digital signal processor circuit 6 (with an internally integrated A / D conversion circuit 5), a force control circuit 7, and an RS485 interface circuit 8.

[0054] The excitation generation circuit 1 generates a sinusoidal excitation signal, which acts on the position detection bridge to drive the magnetic levitation coil. Processing a 12kHz signal requires a high bandwidth operational amplifier, and generating a 1.6V 12kHz AC signal further requires a high slew rate. Therefore, the bandpass filter circuit 9 can only use a domestically produced four-channel integrated operational amplifier, the FX147BH(Z). To address the insufficient AC excitation signal load capacity of the bandpass filter circuit 9, one channel of the FX147BH(Z) is used to form a voltage follower 10 for the AC excitation signal, significantly improving the load capacity of the excitation generation circuit 1.

[0055] Position detection bridge 2 is used to detect the magnetic levitation voltage signal of each channel, which represents the current position of the float of the three-buoy instrument.

[0056] The multiplexer switch 3 is used for channel selection of the magnetic levitation position signal, enabling the separate acquisition of the magnetic levitation signal.

[0057] Signal processing circuit 4 is used to amplify, demodulate, and filter the acquired position signal to form the analog signal to be converted;

[0058] A / D conversion circuit 5 is used to convert the processed position signal into a digital signal to obtain the digital signal of the magnetic levitation position. A / D conversion circuit 5 is a 12-bit A / D converter integrated into digital signal processor circuit 6, which replaces the single-chip A / D conversion circuit of the prior art. Through reference source correction and median filtering, the accuracy of A / D conversion circuit 5 is better than that of the prior art.

[0059] Digital signal processor circuit 6 is the core control device of the circuit, storing embedded software and magnetic levitation parameters, generating PWM, performing I / O control, calculation, and communication functions. Embedded software in digital signal processor circuit 6 performs calculations and analysis on digital signals, executes magnetic levitation force control based on the calculation results, and sends position signals and force control signals to the host computer for monitoring via an RS485 interface circuit.

[0060] The force-adding control circuit 7 is used to respond to the control signal output by the digital signal processing circuit 5. As an actuator, it controls the DC power supply of the magnetic levitation coil to switch on and off to achieve magnetic levitation force-adding. The force-adding control circuit 7 uses the analog switch SF312MD, whose package size is 3 times that of the pseudo-empty package chip analog switch TW312SS in the prior art.

[0061] RS485 interface circuit 8 is used for communication between the magnetic levitation control circuit and external devices.

[0062] In the above-mentioned three-float instrument magnetic levitation control circuit, the excitation generation circuit 1 generates a PWM square wave through the digital signal processor circuit 6. The PWM square wave signal is converted into a sinusoidal excitation signal of the target value after passing through the bandpass filter circuit 9 and the voltage follower 10.

[0063] The position detection bridge 2 is a bridge circuit composed of resistors and coils. It can convert the change in coil inductance caused by the change in float position into an AC voltage signal, which represents the change in magnetic levitation position.

[0064] The multi-channel selection switch 3 is used to sequentially select multiple channels of the magnetic levitation position signal, and can collect the magnetic levitation signal of each channel one by one as needed.

[0065] The signal processing circuit 4 is used to amplify, demodulate, and filter the acquired position signal to form an analog signal to be converted. It includes a differential amplifier circuit 11 and a demodulation circuit 12. The differential amplifier circuit 11 amplifies and performs difference processing on the selected positive and negative magnetic levitation differential signals to obtain the amplified position signal. The demodulation circuit 12 includes a phase-sensitive demodulator and a low-pass filter circuit. The phase-sensitive demodulator demodulates the differentially amplified position signal, using the sinusoidal excitation signal output by the excitation generator circuit 1 as a reference signal to obtain a full-half-wave AC signal representing the magnetic levitation position. The low-pass filter circuit filters the full-half-wave AC signal into a DC signal representing the magnetic levitation position.

[0066] The A / D conversion circuit 5 is an integrated module built into the digital signal processor circuit. It is responsible for converting the DC signal obtained from the signal processing circuit 4 into a digital signal, which is then input into the digital signal processor circuit 6 for further calculation and processing.

[0067] The digital signal processor circuit 6 adopts the domestic DSP controller JDSPF2812A. In this invention, the crystal oscillator JA120-30MHz is used as the clock source of the digital signal processor circuit 6. The frequency divider circuit in the digital signal processor circuit 6 generates a 12kHz clock, and the event manager module EVA in the digital signal processor circuit 6 outputs a 12kHz PWM square wave.

[0068] The digital signal processor circuit 6 has an on-chip FLASH memory, with 9 sectors A, C to J used to store the magnetic levitation control software, and sector B dedicated to storing the magnetic levitation parameters. This eliminates the need for an off-chip memory and makes full use of the memory resources of the digital signal processor circuit 6.

[0069] The digital signal processor circuit 6 contains embedded magnetic levitation control software, which performs functions such as system initialization, PWM square wave generation, channel selection control, A / D conversion circuit data acquisition, magnetic levitation control law calculation of force value, output of force control signal, and RS485 communication. The digital signal processor circuit 6 includes five main functional modules: system initialization module S1, magnetic levitation position acquisition and processing module S2, magnetic levitation force calculation module S3, magnetic levitation force execution module S4, and RS485 communication module S5, realizing the following control process:

[0070] System initialization module S1: Sets the system clock, enables interrupts, enables the multiplexing switch, and reads the magnetic levitation parameters of sector B, etc.

[0071] Magnetic levitation position acquisition and processing module S2: PWM output enable, multi-channel gating switch gating control, A / D conversion, etc.

[0072] Magnetic levitation force calculation module S3: Instruments in this field typically preset a digital range for the float's centering position, known as the dead zone. The sampled digital position value is compared with the dead zone. If it is within the dead zone, the float is considered to be in the center position, and no force is required. If it exceeds the upper boundary of the dead zone or the lower boundary of the small dead zone, positive or negative force is required to pull the float into the dead zone. The force is dynamically adjusted based on the difference between the value exceeding the dead zone boundary. The larger the difference, the longer the force application time within the force application cycle; the smaller the difference, the shorter the force application time within the force application cycle.

[0073] The magnetic levitation force application module S4 includes PWM enable / disable and control of the force application switch. The magnetic levitation coils serve as both detection and execution mechanisms, employing a time-division multiplexing approach. Position acquisition and magnetic levitation force application are both achieved through the coils. To avoid superimposed interference caused by the excitation signal still being supplied during force application, the excitation signal must be disconnected, i.e., the PWM enable / disable. Based on the force application calculation results in S3, the force application switch is controlled via the GPIO port to input the force application current into the ten magnetic levitation coils, generating magnetic pull to center the float.

[0074] RS485 communication module S5: Sends communication data such as magnetic levitation position and force data to the outside world.

[0075] The force-adding control circuit 7 has each force-adding switch controlled by the I / O port of the digital signal processor. Based on the force-adding value calculated according to the magnetic levitation control law, the force-adding switch is controlled to turn on to connect the force-adding path and provide magnetic levitation force to the float. The total number of channels in the force-adding control circuit 7 is not less than 10.

[0076] This invention relates to a magnetic levitation control circuit for three-float instruments, used for controlling the magnetic levitation bearings of three-float instruments. It can also be used to control other magnetic levitation bearings, and can be applied to high-precision navigation in the aviation and aerospace fields. All components of this invention are completely domestically produced and controllable, achieving 100% localization. This invention enables the elimination of dependence on foreign technology and chips in existing circuits, achieving localization and miniaturization of the magnetic levitation circuit for three-float instruments, as well as rapid and precise control of the controlled object.

[0077] Example:

[0078] Figure 1 This is a structural block diagram of a fully domestically produced three-buoy instrument magnetic levitation control circuit according to an embodiment of the present invention. In this embodiment, the fully domestically produced three-buoy instrument magnetic levitation control circuit includes: an excitation generation circuit 1, a position detection bridge 2, a multiplexer switch 3, a signal processing circuit 4, an A / D conversion circuit 5 integrated in a digital signal processor circuit 6, a digital signal processor circuit 6, a force control circuit 7, and an RS485 interface circuit 8.

[0079] The excitation generation circuit 1 includes a bandpass filter circuit 9 and a voltage follower 10. Based on the required excitation signal parameters, resistors and capacitors with appropriate resistance and capacitance values ​​are configured so that the bandpass filter circuit 9 modulates the PWM square wave signal generated by the digital signal processor circuit 6 into the required sinusoidal excitation signal. The voltage follower 10 is used to stabilize the sinusoidal signal so that it is not affected by the subsequent load.

[0080] In this embodiment, the digital signal processor circuit 6 is programmed by software to output a 3.3V square wave signal with a 50% duty cycle via the PWM pin after initialization; appropriate resistance and capacitance values ​​are set for the bandpass filter circuit 9, which can be obtained through experience and calculation. One preferred design is as follows:

[0081] The bandpass filter circuit is selected as an active second-order bandpass filter. According to the following formulas (1), (2), (3), and (4), it can be seen that by adjusting as follows... Figure 3 The resistance values ​​of resistors R1, R2, and R3 and the capacitance values ​​of capacitors C (C = C1 = C2) shown can be used to obtain the excitation signal with the required gain, bandwidth, and Q value.

[0082] Magnification

[0083] Quality Factor

[0084] Center frequency

[0085] bandwidth

[0086] According to the above design, the square wave signal can be converted into a sinusoidal excitation signal with an effective value of 1.6V and a frequency of 12KHz; the operational amplifiers in the bandpass filter circuit 9 and the voltage follower 10 are preferably four-channel integrated operational amplifiers.

[0087] The position detection bridge 2, composed of a coil and a resistor, converts the change in coil inductance caused by the change in float position into an AC voltage signal. Its implementation involves obtaining the equivalent impedance of the excited inductor coil based on the applied excitation signal, calculated as shown in formula (5):

[0088] Equivalent impedance

[0089] By selecting the appropriate bridge arm resistor, the bridge balance state for centering the magnetic levitation float can be achieved.

[0090] The multiplexer switch 3 is used to select the position detection signals of multiple channels of magnetic levitation coils. The multiplexer switch 3 is turned on and off sequentially by the digital signal processor circuit 6, and the magnetic levitation signals of each channel can be collected as needed.

[0091] In this embodiment, ten magnetic levitation coils are set up, and five differential signals are obtained through the position detection bridge 2; the multi-channel selection switch 3 is preferably a domestic dual 8-to-1 analog switch, so that the five signals are input into the subsequent circuit in the set selection order.

[0092] The signal processing circuit 4 includes a differential amplifier circuit 11 and a demodulation circuit 12. The differential amplifier circuit 11 amplifies and performs difference processing on the selected positive and negative magnetic levitation differential signals to obtain the amplified position signal; the demodulation circuit 12 modulates the differentially amplified position signal, uses the sinusoidal excitation signal output by the excitation generator circuit 1 as a reference signal, and demodulates to obtain the magnetic levitation position DC signal.

[0093] In this embodiment, the differential amplifier circuit 11 is preferably a domestically produced instrumentation amplifier, which has the characteristics of low cost and high precision, and the required amplification factor can be set by adjusting the resistor. In this embodiment, according to the overall system gain, the resistance value of the adjusting resistor is selected as 9.1KΩ and the amplification factor is 5.5 times.

[0094] In this embodiment, the modem in demodulation circuit 12 is preferably a domestically produced phase-sensitive demodulator, which has the characteristic of adjustable output zero point. Since the signal used for A / D conversion must be a DC signal, adaptive adjustments are also required based on the selected phase-sensitive demodulator type. If the demodulated signal is DC, it can be directly used for A / D conversion; if the demodulated signal is AC, a filter circuit can be set up to convert it into a DC signal according to the signal condition. In one case of this embodiment, the demodulated waveform is a half-wave AC signal, so a second-order low-pass filter circuit is designed to filter the waveform to obtain the corresponding DC signal.

[0095] In this embodiment, the excitation generation circuit 1 and signal processing circuit 4 (including differential amplifier circuit 11 and demodulation circuit 12) are designed independently, realizing the domestic substitution of the excitation generation and demodulation functions of foreign LVDT signal processors, and solving the problem that the related device circuits cannot be domestically produced.

[0096] A / D conversion circuit 5 is used to convert the processed DC position signal into an analog-to-digital signal to obtain a magnetic levitation position digital signal.

[0097] In this embodiment, the aforementioned A / D conversion circuit 5 preferably uses the 12-bit A / D module built into P in the digital signal processor circuit 6, which reduces the use of peripheral chips and further reduces the circuit size and cost; since the input voltage requirement of the A / D conversion circuit 5 is positive, the aforementioned fourth operational amplifier of the four-channel operational amplifier is used to design an adder circuit to raise the demodulated DC signal to a constant voltage value.

[0098] To further protect the digital signal processing circuit 6, this embodiment uses an A / D input limiting circuit composed of two switching diodes to clamp the high input voltage to 3.3V and the low input voltage to 0V, thus preventing damage to the device from excessively high or low negative input voltages.

[0099] The digital signal processor circuit 6 contains magnetic levitation control software, which performs calculations and analysis on the position digital signal, calculates the required force value, executes magnetic levitation force control based on the calculation results, and sends the position signal and force control signals to the outside for monitoring via the RS485 interface circuit.

[0100] The common package shape of the digital signal processor circuit 6 is the quad flat package (LQFP). In this embodiment, the preferred package shape of the digital signal processor circuit 6 is BGA, which is smaller than the conventional LQFP package. Furthermore, by adjusting the pin arrangement of the device from a U-shape to a 16*16 array arrangement, the BGA package shape is further optimized, reducing the size by one-third compared to the conventional surface mount package, which is beneficial for further reducing the circuit size.

[0101] The force-adding control circuit 7 is used to respond to the control signal output by the digital signal processing circuit 6. As an actuator, it controls the magnetic levitation coil to switch on and off the force-adding power supply through a control switch to realize magnetic levitation force addition. Its single-channel switch is controlled by a single-channel I / O. When force is added, the single-channel switch is turned on to allow the DC power supply to pass through and provide current to the single-channel coil. The total number of channels of the force-adding switch is not less than 10.

[0102] In this embodiment, the force control circuit 7 uses three domestically produced four-way single-pole single-throw analog switches, which have the characteristics of separate control by four switches and large channel input current.

[0103] RS485 interface circuit 8 is used for communication between the magnetic levitation circuit and the host computer.

[0104] Reference Figure 2 As shown, in this embodiment, the force control circuit 7 includes five main functional modules: a system initialization module S1, a magnetic levitation position acquisition and processing module S2, a magnetic levitation force calculation module S3, a magnetic levitation force execution module S4, and an RS485 communication module S5. The main loop of the program can be formed by modules S2 to S5, which executes cyclically after system initialization.

[0105] System initialization module S1: Sets the system clock, interrupt enable, multiplexing switch enable, etc.

[0106] Magnetic levitation position acquisition and processing module S2: PWM output enable, multi-channel gating switch selection control, A / D conversion, etc.; In this embodiment, five magnetic levitation signals need to be acquired, and the multi-channel gating switch is controlled through the I / O port to select each position signal in sequence.

[0107] Magnetic levitation force calculation module S3: In this embodiment, the instrument presets a digital range for the float's centering position, called the dead zone, which can be set to, for example, 2048±8. The sampled position digital value is compared with the dead zone. If it is within the dead zone, the float is considered to be in the center position, and no force is required. If it is greater than the upper boundary of the dead zone (2056 in this example) or the lower boundary of the small dead zone (2040 in this example), then positive or negative force is required to pull the float into the dead zone.

[0108] The S4 module for magnetic levitation force application includes PWM enable / disable and control of the force application switch on / off. In this embodiment, the magnetic levitation coil serves as both the detection and execution mechanism, employing a time-division multiplexing approach. Both position acquisition and magnetic levitation force application are achieved through the coil. To avoid superimposed interference caused by the excitation signal still being supplied during force application, the excitation signal must be disconnected, i.e., the PWM enable / disable. Based on the force application calculation results in S3, ten force application switches are controlled via GPIO ports to input the force application current into ten magnetic levitation coils, generating magnetic pull to center the float.

[0109] RS485 communication S5 module: Sends magnetic levitation position and force data to the host computer.

[0110] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0111] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A magnetic levitation control circuit for a three-float instrument, characterized in that, It includes an excitation generation circuit (1), a position detection bridge (2), a multiplexer switch (3), a signal processing circuit (4), a digital signal processor circuit (6), and a force control circuit (7); The digital signal processor circuit (6) generates a PWM square wave and outputs the square wave to the excitation generator circuit (1); The excitation generation circuit (1) receives the PWM square wave input by the digital signal processor circuit (6), modulates the PWM square wave into a sinusoidal excitation signal, and outputs the sinusoidal excitation signal to the position detection bridge (2). The position detection bridge (2) drives the magnetic levitation coil to work under the action of the sinusoidal excitation signal; The position detection bridge (2) acquires the AC voltage signal used to characterize the position of the magnetic levitation coil, and outputs the AC voltage signal to the signal processing circuit (4) through the multiplexer (3); The signal processing circuit (4) converts the AC voltage signal input by the position detection bridge (2) into a DC signal used to characterize the position of the magnetic levitation coil, and outputs the DC signal to the digital signal processor circuit (6). The digital signal processor circuit (6) obtains the force control signal based on the DC signal and outputs the force control signal to the force control circuit (7); The force control circuit (7) responds to the force control signal and provides levitation force to the magnetic levitation coil; The signal processing circuit (4) includes a differential amplifier circuit and a demodulation circuit. The differential amplifier circuit amplifies and performs differential processing on the selected differential signal to obtain a differentially amplified AC voltage signal. The differential signal is formed by the AC voltage signals output from the two channels of the position detection bridge (2). The demodulation circuit includes a phase-sensitive demodulator and a low-pass filter circuit. The phase-sensitive demodulator uses the sinusoidal excitation signal input from the excitation generator circuit (1) as a reference signal to demodulate the differentially amplified AC voltage signal to obtain a full-half-wave AC signal used to characterize the position of the magnetic levitation coil. The low-pass filter circuit filters the full-half-wave AC signal into a DC signal used to characterize the position of the magnetic levitation coil. The differential amplifier circuit is a domestically produced instrumentation amplifier ZSAD620TF, and the demodulation circuit is a domestically produced phase-sensitive demodulator LZX2. The excitation generation circuit (1) includes a bandpass filter circuit (9) and a voltage follower (10); The bandpass filter circuit (9) is used to modulate the PWM square wave into a sinusoidal excitation signal, and the voltage follower (10) is used to stabilize the sinusoidal excitation signal so that it is not affected by the subsequent load. The resistors and capacitors in the bandpass filter circuit (9) are determined according to the parameters of the sinusoidal excitation signal required in actual use; The bandpass filter circuit (9) is an active second-order bandpass filter; An active second-order bandpass filter includes resistors R1, R2, and R3, and capacitors C1 and C2; The operational amplifier in the bandpass filter circuit (9) is a four-channel integrated operational amplifier FX147BH(Z), and one channel of FX147BH(Z) is used to form a voltage follower (10) for the AC excitation signal. The digital signal processor circuit (6) adopts the domestic DSP controller JDSPF2812A, and uses the crystal oscillator JA120-30MHz as the clock source of the digital signal processor circuit (6). The 12kHz clock is generated by the frequency divider circuit inside the digital signal processor circuit (6), and the 12kHz PWM square wave is output by the event manager module EVA inside the digital signal processor circuit (6). The digital signal processor circuit (6) has an on-chip memory FLASH, with 9 sectors A, C to J used to solidify the magnetic levitation control software, and sector B dedicated to solidifying the magnetic levitation parameters.

2. The magnetic levitation control circuit for a three-buoy instrument according to claim 1, characterized in that, The position detection bridge (2) acquires multiple differential signals used to characterize the position of the magnetic levitation coil; The digital signal processor circuit (6) controls the sequential switching of each gating switch in the multiplexing switch (3) so that the differential signals are input into the signal processing circuit (4) in the set gating order.

3. The magnetic levitation control circuit for a three-buoy instrument according to claim 1, characterized in that, The digital signal processor circuit (6) includes a system initialization module, a magnetic levitation position acquisition and processing module, a magnetic levitation force calculation module, a magnetic levitation force execution module, and an RS485 communication module; The system initialization module is used to set the system clock, interrupt enable, and multiplexing switch enable; The magnetic levitation position acquisition and processing module includes a PWM square wave generation module, an A / D conversion circuit (5), and a multiplexer control module; the A / D conversion circuit (5) is used to convert the DC signal input by the signal processing circuit (4) into a digital signal; the multiplexer control module is used to control the selection of the multiplexer switch (3); The magnetic levitation force calculation module presets a digital range for the float's centering position, i.e., the dead zone. It compares the digital signal with the preset dead zone to obtain the force control signal. Specifically, if the digital signal is within the dead zone, the float is considered to be in the center position, and no force is required. If the digital signal is greater than the upper boundary of the dead zone or the lower boundary of the small dead zone, positive or negative force is required to pull the float into the dead zone. The magnitude of the force is dynamically adjusted according to the difference between the digital signal and the dead zone boundary. The larger the difference, the longer the force application time within the force application cycle; the smaller the difference, the shorter the force application time within the force application cycle. The magnetic levitation force module is used to enable PWM and control the on / off state of the force switch; the force control circuit (7) enables PWM when providing levitation force to the magnetic levitation coil. According to the force control signal, the force control circuit (7) is controlled through the GPIO port to input the force current into the magnetic levitation coil, generating magnetic pull force to keep the float centered. The RS485 communication module is used to communicate with external devices.

4. The magnetic levitation control circuit for a three-buoy instrument according to claim 3, characterized in that, The A / D conversion circuit (5) is a 12-bit A / D module built into the digital signal processor circuit (6); The digital signal processor circuit (6) also includes an A / D input limiting circuit connected between the A / D conversion circuit (5) and the signal processing circuit (4); the A / D input limiting circuit consists of two switching diodes, which clamp the high voltage of the input A / D conversion circuit (5) to 3.3V and the low voltage of the input to 0V.

5. The magnetic levitation control circuit for a three-buoy instrument according to claim 1, characterized in that, The force control circuit (7) includes ≥10 force switches. Each force switch is controlled by the force control signal output from the I / O port of the digital signal processor circuit (6). When the force switch is turned on, the magnetic levitation coil is connected to the DC power supply to perform magnetic levitation force.

6. The magnetic levitation control circuit for a three-buoy instrument according to claim 1, characterized in that, Assume the required parameters for the sinusoidal excitation signal include the amplification factor A. u Quality factor Q, center frequency f0, bandwidth B w The resistors R1, R2, R3 and the capacitors C1 and C2 are calculated according to the following formula: Where C = C1 = C2.

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