CN100465651C - Resonant Sensor Control System Using Intermittent Work Mode - Google Patents

Abstract

The resonant sensor control system adopts intermittent working mode, including a preamplifier, a frequency detector, a controller and an excitation signal generator. The signal output by the vibration pickup element is amplified by the preamplifier, and the output of the vibration pickup element is measured by the frequency detector. The frequency of the signal, the controller controls the excitation signal generator to generate the excitation signal, the excitation signal adopts the linear frequency modulation signal, the resonator of the sensitive structure vibrates under the excitation of the linear frequency modulation signal, when the controller controls the excitation signal to be disconnected, the resonator is in free Vibration state, its vibration frequency is the natural frequency of the resonator, after the excitation signal is disconnected, the controller controls the frequency detector to detect the frequency of the output signal of the vibration pickup element, and measures the natural frequency of the resonator, so as to realize the measurement of the measured signal . The excitation element and the vibration pickup element in the sensitive structure can be the same element. The invention solves the problem that the output signal of the sensitive structure of the resonant sensor is relatively weak when a single frequency signal is used for excitation.

Description

Resonant Sensor Control System Using Intermittent Work Mode

technical field

The invention relates to a resonant sensor control system, in particular to a resonant sensor control system adopting an intermittent working mode.

Background technique

Under the action of the measured sensor, the natural frequency of the resonator of its sensitive structure changes, and the measured value can be measured by measuring the natural frequency of the resonator. The performance indicators such as repeatability, resolution and stability of the resonant sensor are suitable for the measurement of various parameters such as pressure, acceleration, force and density.

Usually the sensitive structure of the resonant sensor needs to be combined with a closed-loop system to work. The usual closed-loop system includes an amplitude control link and a phase shift link. The amplitude controller is used to adjust the gain of the entire closed loop to meet the amplitude conditions of the self-excited closed-loop of the resonant sensor. The phase shift link is used to adjust the phase shift of the entire closed loop to meet the phase conditions of the self-excited closed loop of the resonant sensor.

The vibration pickup signal of the resonant sensor will be interfered by its excitation signal, thereby reducing the signal-to-noise ratio of the vibration pickup signal, making it difficult to measure the vibration pickup signal. Thierry Corman et al. in 1999 in the article "Burst" Technology with Feedback- Loop Control for Capacitive Detection and Electrostatic Excitation of Resonant Silicon Sensors' proposes a "Burst" technology to solve this problem, using the method of time-sharing excitation and time-sharing detection to realize the closed loop of the resonant sensor. In this scheme , using a single frequency signal to excite the sensor. The problem with this method is that when the excitation frequency deviates too much from the natural frequency of the resonator of the sensitive structure of the resonant sensor, the intensity of the output signal of the sensitive structure will be very weak. The theoretical frequency characteristics of the resonator are shown in Figure 2. From the amplitude-frequency characteristics of the resonator, it can be seen that when the excitation signal deviates too much from the natural frequency of the resonator, the gain of the resonator is much lower than the gain corresponding to its natural frequency. When the strength of the output signal of the resonator is very weak, the detection circuit will not be able to measure the output signal of the resonator.

Contents of the invention

The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, to provide a resonant sensor control system that adopts an intermittent working mode, and to solve the problem that the output signal of the sensitive structure of the resonant sensor is relatively weak when a single frequency signal is used for excitation.

The technical solution of the present invention: the resonant sensor control system adopting the intermittent working mode is characterized in that it includes a preamplifier, a frequency detector, a controller and an excitation signal generator, and the controller controls the excitation signal generator to generate an excitation signal. The excitation signal adopts a linear frequency modulation signal, and the resonator of the sensitive structure vibrates under the excitation of the linear frequency modulation signal. When the controller controls the excitation signal to be disconnected, the resonator is in a free vibration state, and its vibration frequency is the natural frequency of the resonator. After disconnecting for a certain period of time, the controller controls the frequency detector to detect the frequency of the output signal of the vibration pickup element amplified by the preamplifier, and measures the natural frequency of the resonator, thereby realizing the measurement of the measured signal.

The principle of the present invention: the present invention adopts the linear frequency modulation signal as the excitation signal of the sensitive structure of the resonant sensor. The linear frequency modulation signal is a signal whose power is more uniformly concentrated in the frequency band between its start frequency and stop frequency. The resonator of the sensitive structure of the resonant sensor is excited by the linear frequency modulation signal, and the power of the resonator vibration is also concentrated in the within this frequency band. When the frequency band of the chirp signal used as the excitation signal contains the natural frequency of the resonator, the vibration signal of the resonator also contains the signal component at its natural frequency point, and the vibration signal of the resonator is also strong, and the deviation from the natural frequency of the resonator When a single frequency signal of a higher frequency is used as an excitation signal, the vibration signal of the resonator is weaker. When the excitation signal used for the sensitive structure of the resonant sensor is disconnected, the resonator will vibrate freely at its natural frequency. By measuring the frequency of the vibration signal in the free vibration state of the resonator, the natural frequency of the resonator can be measured, thereby Realize the measurement of the measurand.

The advantages of the present invention compared with the prior art: because the present invention has adopted the linear frequency modulation signal as the excitation signal of the sensitive structure of the resonant sensor, relative to the single frequency signal of the resonator which deviates from the sensitive structure of the resonant sensor as the excitation signal, effective The strength of the output signal of the sensitive structure of the resonant sensor is improved.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is the theoretical frequency characteristic curve diagram of the resonant sensor of the present invention, wherein Fig. 2a is the amplitude-frequency characteristic curve diagram, and Fig. 2b is the phase-frequency characteristic curve diagram;

Fig. 3 is a structural schematic diagram of the sensor control system when the excitation element and the vibration pickup element are the same element in the sensitive structure of the present invention.

Detailed ways

As shown in Figure 1, the sensor control system 2 of the intermittent working method of the resonant sensor is composed of a preamplifier 6, a frequency detector 5, a controller 4 and an excitation signal generator 3, and the output of the vibration pickup element 7 of the sensitive structure 1 The signal is amplified by the preamplifier 6, and the frequency of the output signal of the pickup element 7 is measured by the frequency detector 5. The controller 4 controls the excitation signal generator 3 to generate an excitation signal. The excitation signal adopts a linear frequency modulation signal, and the resonator of the sensitive structure 1 8 vibrates under the excitation of the linear frequency modulation signal. When the controller 4 controls the excitation signal to disconnect, the resonator 8 is in a free vibration state, and its vibration frequency is the natural frequency of the resonator. After the excitation signal is disconnected, the controller 4 controls the frequency The detector 5 detects the frequency of the output signal of the vibration pickup element 7 to measure the natural frequency of the resonator 8 .

As shown in Figure 3, when the excitation element 9 and the vibration pickup element 7 in the sensitive structure 1 are the same element, that is, when the vibration pickup element 10 is excited, the switch 11 is used to switch, when the sensitive structure 1 of the resonant sensor needs to be excited , the controller 4 controls the switch 11 to connect the excitation signal generator 3, and the signal output by the excitation signal generator 3 passes through the switch 11 to excite the excitation pickup element 10 in the sensitive structure 1; after the excitation signal is completed, the controller 4 controls The switching switch 11 turns on the preamplifier 6, and the signal output by the excitation pickup element 10 is detected by the frequency detector 5 after passing through the preamplifier 6, and the natural frequency of the resonator 8 is measured.

The above-mentioned excitation signal generator 3 is implemented by a DDS chip, and the DDS chip can be a series of DDS chips of ADI Company, such as AD9852.

The frequency detector 5 can be realized by an analog-to-digital converter or a microprocessor, for example: the analog-to-digital converter can be AD7671 of ADI Company, and the processor can adopt a single-chip microcomputer C8051F120 or a digital signal processor TMS3206713.

The controller 4 can be realized by using a digital signal processor DSP or a single-chip microcomputer, for example: TMS3206713, C8051F120 and other processors.

The changeover switch 11 can be realized by using an analog switch or a relay.

The preamplifier 6 is designed according to the characteristics of the pickup element 7 or the excitation pickup element 10 of the sensitive structure 1 . When the pickup element 7 and the excitation pickup element 10 are resistors, they can be realized by an operational amplifier. The selection of the operational amplifier should take into account the bandwidth of the sensor vibration signal, the noise of the operational amplifier itself and the DC bias, so as to ensure that the sensor output can be well realized. For the amplification of the weak signal and the excitation signal required by the sensor, OPA627, OPA228, LT1028 and other operational amplifiers can be selected.

Claims (2)

1, adopt the resonant type sensor control system of intermittent working mode, it is characterized in that: comprise preamplifier (6), frequency detector (5), controller (4) and excitation signal generator (3), sensitive structure (1 The signal output by the vibration pickup element (7) of ) is amplified by the preamplifier (6), and the frequency of the output signal of the vibration pickup element (7) is measured by the frequency detector (5), and the controller (4) controls the excitation signal generator (3) Generate an excitation signal, the excitation signal adopts a linear frequency modulation signal, and the resonator (8) of the sensitive structure (1) vibrates under the excitation of the linear frequency modulation signal. When the controller (4) controls the excitation signal to disconnect, the resonator ( 8) It is in a free vibration state, and its vibration frequency is the natural frequency of the resonator. After the excitation signal is disconnected, the controller (4) controls the frequency detector (5) to detect the frequency of the output signal of the vibration pickup element (7), and measures the resonance The natural frequency of the device (8). 2. The resonant sensor control system adopting intermittent working mode according to claim 1, characterized in that: when the excitation element (9) and the vibration pickup element (7) in the sensitive structure (1) are the same element , that is, when the vibration pickup element (10) is excited, the switching switch (11) is used for switching, and when the sensitive structure (11) of the resonant sensor needs to be excited, the controller (4) controls the switching switch (11) to turn on the excitation signal to generate device (3), the signal output by the excitation signal generator (3) passes through the switch (11) to excite the excitation pickup element (10) in the sensitive structure (1); after the excitation signal is completed, the controller (4) controls the switch (9) Connect the preamplifier (6), and the signal output by the excitation pickup element (10) is detected by the frequency detector (5) after the preamplifier (6), and the natural frequency of the resonator (8) is measured.

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