Closed-loop control system and method of pendulum accelerometer based on velocity feedback principle

Abstract

The present invention belongs to the technical field of accelerometer closed-loop control, and specifically relates to a closed-loop control system and method of a pendulum accelerometer based on the principle of velocity feedback. The system comprises: a velocity detection unit, a displacement detection unit, a signal pickup and demodulation unit, and a force feedback execution unit. Among them, the velocity detection unit and the displacement detection unit are connected to the signal pickup and demodulation unit, and the signal pickup and demodulation unit is connected to the force feedback execution unit to realize the closed-loop control of the accelerometer system. The control method simultaneously detects and utilizes the displacement signal and velocity signal of the accelerometer pendulum assembly to participate in the control algorithm, so as to realize the high-speed measurement of the flexible pendulum accelerometer under high dynamic conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of accelerometer closed-loop control, and in particular relates to a pendulum accelerometer closed-loop control system and method based on a velocity feedback principle. Background Art

[0002] As a core component of an inertial navigation system, the accelerometer provides acceleration information, and its accuracy directly impacts the accuracy of the navigation system. Currently, high-precision accelerometers, both domestically and internationally, generally utilize a closed-loop control model. This involves detecting the offset of the pendulum assembly within the accelerometer, providing a feedback control signal, calculating and demodulating the signal, and then controlling the actuator to pull the pendulum assembly back to its equilibrium position, thereby achieving high-precision acceleration measurement. Because closed-loop control allows the pendulum assembly to be constrained near a fixed position, accelerometers exhibit significant advantages over open-loop accelerometers in terms of static accuracy and interference immunity.

[0003] Traditional accelerometer closed-loop control systems generally consist of a displacement detection device, a demodulation and amplification device, and a drive device. The displacement detection device can only detect the distance the pendulum assembly deviates from its equilibrium position, i.e., displacement detection. However, the controlled object is the acceleration value, and the displacement is obtained by integrating the acceleration twice. The phase angle value in its amplitude-frequency characteristic will lag 180° behind the acceleration signal. The signal output by the demodulation and amplification device always lags behind the changes in external acceleration, resulting in this type of accelerometer having the disadvantages of poor dynamic tracking, obvious resonance, and large vibration errors. Chinese patent CN201710613390.3 discloses an accelerometer control method. This method detects the accelerometer input signal and uses a computer to determine the signal type, external vibration conditions, etc., to provide a compensation amount. Its disadvantage is that it relies on complex sampling, data processing devices, and algorithms, which are very complex. In addition, it cannot provide an accurate compensation amount under complex vibration conditions, which greatly limits its application field. Theoretically, there is always a lag effect when controlling the acceleration through displacement detection. Even if a more complex control system is designed, it can only make slight improvements to the existing problem and cannot fundamentally solve it. Summary of the Invention

[0004] In view of the above problems in the prior art, an object of the present invention is to provide a closed-loop control system of a pendulum accelerometer based on the velocity feedback principle.

[0005] A closed-loop control system of a pendulum accelerometer based on the velocity feedback principle comprises: a velocity detection unit, a displacement detection unit, a signal pickup and control unit, and a force feedback execution unit; the signal pickup and control unit are electrically connected to the velocity detection unit, the displacement detection unit, and the force feedback execution unit respectively;

[0006] The speed detection unit is used to detect the movement speed of the pendulum assembly, the displacement detection unit is used to detect the displacement change of the pendulum assembly, and the force feedback execution unit is used to pull the pendulum assembly back to the equilibrium position after the pendulum assembly swings; the signal pickup and control unit is used to receive the speed signal representing the movement speed input by the speed detection unit, receive the displacement signal representing the displacement change, and determine the feedback force size based on the two signals; and transmit the driving signal with the feedback force size to the force feedback execution unit. After receiving the driving signal, the force feedback execution unit converts the driving signal into a torsional force that drives the movement of the pendulum assembly.

[0007] Furthermore, the speed detection unit includes a speed detection coil, a magnet and a magnetic field loop, and a signal demodulator;

[0008] The speed detection coil is installed under the moving end of the pendulum assembly; the speed detection coil is in the magnetic field of the force speed detection unit; the magnet of the speed detection unit and the displacement detection unit are fixed to the base of the system; the signal demodulator is set between the speed detection coil and the signal pickup and control unit;

[0009] When the speed detection coil moves relative to the magnet, an electric potential difference signal proportional to the speed is formed at both ends of the speed detection coil due to the principle of electromagnetic induction; the signal demodulator is used to demodulate and amplify the electric potential difference signal induced by the speed detection coil into a speed signal.

[0010] Furthermore, the speed detection coil is wound with multiple turns of conductive cable with an insulating sheath.

[0011] Furthermore, the displacement sensor selected by the displacement detection unit includes a capacitive, photoelectric, or grating displacement sensor.

[0012] A closed-loop control method for a pendulum accelerometer based on a velocity feedback principle, comprising:

[0013] Picking up a speed signal from the speed detection unit and picking up a displacement signal from the displacement detection unit;

[0014] The velocity signal and displacement signal are processed comprehensively to obtain a feedback signal. The feedback signal can directly affect the damping coefficient of the accelerometer core, that is, the control system response speed. It can be adjusted to exceed the bandwidth required by the system, forming a zero-error system and improving control accuracy.

[0015] Feedback signal is fed back to the input torquer coil.

[0016] Furthermore, the transfer function of the comprehensive processing is:

[0017]

[0018] Among them: U O is the control system output; I inis the displacement signal detected and demodulated by the displacement detection unit; α is the offset angle of the pendulum component, that is, the velocity signal; K1, K2, K3 are the proportional coefficients of each control item; s is the differential sign of the signal, and 1 / s is the integral sign of the signal.

[0019] Furthermore, after feeding the feedback signal back to the input torquer coil, the method further includes:

[0020] The feedback signal is converted into a torsional force that drives the pendulum assembly to move, pushing the pendulum assembly back to the equilibrium position to achieve a force balance state.

[0021] Furthermore, specific implementation forms of the force feedback execution unit include electromagnetic and electrostatic.

[0022] The present invention enables closed-loop control of an accelerometer based on velocity signal feedback. Compared to traditional closed-loop feedback control methods based solely on displacement signals, this new method significantly reduces control hysteresis, effectively predicting the motion trend of the pendulum assembly, improving dynamic control accuracy, and enhancing the accelerometer's tracking and reproducibility for high-dynamic signals. Furthermore, due to the optimized tracking performance of the pendulum assembly, the pendulum's swing amplitude can be effectively reduced. This not only reduces vibration errors caused by nonlinear factors, but also improves the accelerometer's tolerance to vibration and shock, thereby enhancing reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A diagram illustrating an implementation of a speed detection unit, a displacement detection unit, a force feedback execution unit, and a pendulum assembly in a closed-loop control system of the present invention;

[0024] Figure 2 It is the overall logical structure diagram of the closed-loop control system of the present invention;

[0025] Figure 3a This is the control effect diagram based on displacement feedback;

[0026] Figure 3b This is the control effect diagram based on speed feedback. DETAILED DESCRIPTION

[0027] The following describes the technical solution in detail with reference to the accompanying drawings and in combination with specific embodiments:

[0028] The present invention provides a closed-loop control system of a pendulum accelerometer based on the speed feedback principle, such as Figure 1 Shown, including:

[0029] The speed detection unit 1 is used to detect the speed signal of the pendulum assembly. The speed detection unit includes a speed detection coil, a magnet, a magnetic field circuit, and a signal demodulator. The magnet, fixed to the base of the accelerometer, generates a uniform magnetic field within a certain area. The speed detection coil is wound from an insulated conductive cable. One end is fixed to the pendulum assembly and moves with it, while the other end is placed in a magnetic field perpendicular to the coil plane. During operation, when the pendulum assembly moves relative to the magnet fixed to the base, it drives the speed sensing coil. Due to the principle of electromagnetic induction, a potential difference signal U related to the speed of movement is generated across the coil. After detection and demodulation by the signal demodulator, a voltage signal proportional to the speed is generated, thereby achieving the function of detecting the speed of the pendulum assembly.

[0030] Displacement detection unit 2 is used to detect the displacement of the accelerometer pendulum assembly relative to its equilibrium position. It outputs an electrical signal proportional to the pendulum assembly's displacement, achieving the purpose of pendulum assembly displacement measurement. Its specific implementation can be capacitive, photoelectric, grating, and other methods.

[0031] The signal pickup and control unit 3 is used to pick up the velocity signal generated by the velocity detection unit and the displacement signal generated by the displacement detection unit. After obtaining the velocity signal and displacement signal, the signal pickup and demodulation unit combines the information of the two to form a force feedback current signal, which is provided to the accelerometer force feedback mechanism to control the position of the accelerometer pendulum assembly, thereby detecting external acceleration;

[0032] The specific control system design method is:

[0033] ① The velocity signal is picked up, amplified, and fed back into the torquer coil. The velocity signal is used to adjust the damping coefficient of the accelerometer core, increasing the system's response speed.

[0034] ② The displacement signal is picked up, amplified, and fed back into the torquer coil. The displacement signal is used to adjust the eigenfrequency of the accelerometer core.

[0035] ③ After integrating and amplifying the displacement signal, it is fed back into the torquer coil. The integrated displacement signal is mainly used to form a zero-error system and improve control accuracy.

[0036] ④ The above signals need to be comprehensively processed before being fed back into the torquer coil, generally by addition and reverse processing.

[0037] The specific control system design method is:

[0038] ① The velocity signal is picked up, amplified, and fed back to the torquer coil 16. The velocity signal feedback can directly affect the damping coefficient of the accelerometer core, that is, the control system response speed. According to empirical methods, the damping coefficient adjustment principle is to match the damping coefficient of the pendulum component with the eigenfrequency to form a slightly underdamped system. Generally, it is designed according to a ratio of 1.2, that is, the system characteristic root is located at ω n ±1.2ω n Where ω n The bandwidth frequency required by the system.

[0039] ② The displacement signal is picked up, amplified, and fed back into torquer coil 16. The displacement signal is used to adjust the eigenfrequency of the accelerometer core. This frequency must be adjusted to exceed the system's required bandwidth.

[0040] ③ After integrating and amplifying the displacement signal, the signal is fed back to the torquer coil 16. The integral displacement signal is mainly used to form a zero-error system and improve control accuracy.

[0041] ④ Before the above signals are fed back into the torquer coil 16, they need to be processed comprehensively, generally by addition and inversion. The resulting transfer function can be expressed as:

[0042]

[0043] Among them, U O is the control system output; I in is the displacement signal detected and demodulated by the displacement detection unit; α is the offset angle of the pendulum assembly; K1, K2, K3 are the proportional coefficients of each control item, which need to be adjusted as needed; s is the differential or integral sign of the signal.

[0044] The above method can be implemented by using an operational amplifier, a differential amplifier, an adder, etc. in a circuit, or by using a computer, a chip with programming function, etc.

[0045] The force feedback actuator 4 receives the drive signal from the signal pickup and demodulation unit and converts the force feedback current signal into a torsional force that drives the pendulum assembly, thereby pushing the pendulum assembly back to the equilibrium position and achieving a force balance state. The force feedback actuator can be implemented in various forms, such as electromagnetic and electrostatic.

[0046] The pendulum assembly 5 is composed of a pendulum assembly with one end fixed. When there is external acceleration, the other end will move or swing around the fixed end, thereby achieving the effect of converting the acceleration signal into a motion signal.

[0047] The pendulum assembly 5 is connected to the speed detection unit 1 and the displacement detection unit 2, and the motion signal generated can be detected by both. Then, both are connected to the signal pickup and control unit 3, and after generating the final control signal, it is connected to the force feedback execution unit 4.

[0048] First, follow Figure 1 The accelerometer structure is shown in the figure. The two magnets with opposing N and N poles generate a uniform magnetic field in the area between them. A velocity sensing coil is connected to the pendulum assembly, with its other end placed in the uniform magnetic field. When subjected to external acceleration, the pendulum assembly is subjected to inertial forces, causing it to oscillate relative to the axis of rotation. This generates velocity and displacement. The velocity sensing coil induces an electromotive force in the magnetic field, which accumulates at the coil's two endpoints, creating a potential difference. This potential difference is proportional to the coil's oscillation velocity, and its direction depends on the pendulum's oscillation direction and coil winding method. This potential difference is conditioned by a differential amplifier circuit, converting it into a voltage signal proportional to the pendulum's oscillation velocity. Figure 1 The displacement sensor shown in the figure can adopt various forms such as capacitive and photoelectric to realize displacement detection and output a voltage signal proportional to the displacement.

[0049] Then, according to Figure 2 The velocity and displacement signals measured by the velocity and displacement detection units are connected to the signal acquisition and control unit. This unit performs operations and integration on the two signals. In actual use, parameter design is required based on the transfer characteristics of the controlled object, namely the acceleration measurement unit. Generally, an integrator, proportional amplifier, adder, or a combination thereof is required to implement the control algorithm.

[0050] The signal acquisition and control unit outputs a control signal, which is then fed into the force feedback actuator. The torquer coil in the force feedback unit is placed within the torquer magnet. When current flows through it, a force perpendicular to the coil is generated, counteracting the inertial force on the pendulum assembly, pulling it back to its equilibrium position and achieving force balance. At this point, the inertial force on the pendulum assembly is equal to the electromagnetic force in the coil.

[0051] according to Figure 2 Connect the previously constructed unit structures to form a closed-loop feedback control structure. When the pendulum assembly achieves force balance, the applied acceleration information can be obtained by detecting the current in the coil, thereby achieving acceleration measurement.

[0052] The present invention proposes a method for detecting the swing speed of the pendulum assembly of a pendulum accelerometer, and introduces the speed signal into a closed-loop control system to form a new control mode. This control system, due to the introduction of the speed signal, greatly reduces the hysteresis of the detection signal, thereby improving the feedback sensitivity of the closed-loop control system. It can be verified from simulation and practice that the accelerometer using this control method has significantly improved dynamic tracking characteristics and significantly reduced vibration errors. Figure 3a and 3b As shown in the figure, the control effects based on displacement feedback and speed feedback are compared. It can be seen that the resonance peak of the speed feedback control can be controlled at around 1dB, while the control based on displacement feedback generally exceeds 5dB, indicating that the signal tracking characteristics are significantly improved and the dynamics are greatly improved.

Claims

1. A closed-loop control system of a pendulum accelerometer based on the velocity feedback principle, characterized in that: include: A speed detection unit (1), a displacement detection unit (2), a signal pickup and control unit (3) and a force feedback execution unit (4); the signal pickup and control unit (3) is electrically connected to the speed detection unit (1), the displacement detection unit (2) and the force feedback execution unit (4) respectively; One end of the pendulum assembly is fixed; when there is external acceleration, the other end will move or swing around the fixed end, thereby achieving the effect of converting the acceleration signal into a motion signal; the pendulum assembly is connected to the speed detection unit (1) and the displacement detection unit (2), and the generated motion signal can be detected by both; The speed detection unit (1) is used to detect the movement speed of the pendulum assembly, the displacement detection unit (2) is used to detect the displacement change of the pendulum assembly, and the force feedback execution unit (4) is used to pull the pendulum assembly back to the equilibrium position after the pendulum assembly swings; The signal pickup and control unit (3) is used to receive a speed signal representing the movement speed input by the speed detection unit (1), receive a displacement signal representing the displacement change, and determine the magnitude of the feedback force according to the two signals; and transmit a driving signal with the magnitude of the feedback force to the force feedback execution unit (4); after receiving the driving signal, the force feedback execution unit (4) converts the driving signal into a torsional force for driving the pendulum assembly to move; The speed detection unit (1) comprises a speed detection coil (11), a magnetic steel and a magnetic field loop (12), and a signal demodulator (13); The speed detection coil (11) is installed under the moving end of the pendulum assembly (5); the speed detection coil (11) is in the magnetic field of the speed detection unit (1); the magnetic steel of the speed detection unit (1) and the displacement detection unit (2) are fixed to the base (6) of the system; the signal demodulator (13) is arranged between the speed detection coil (11) and the signal pickup and control unit (3); When the speed detection coil (11) moves relative to the magnetic steel, an electric potential difference signal proportional to the speed is formed at both ends of the speed detection coil (11) according to the principle of electromagnetic induction; the signal demodulator (13) is used to demodulate and amplify the electric potential difference signal induced by the speed detection coil (11) into a speed signal; When affected by external acceleration, the pendulum assembly is acted upon by inertial force, causing it to swing relative to the rotating shaft. At this time, the pendulum assembly generates speed and displacement. The speed detection coil induces electromotive force in the magnetic field, which gathers at the two ends of the coil to form a potential difference. This potential difference is conditioned by the differential amplifier circuit and converted into a voltage signal proportional to the swing speed of the pendulum assembly. The speed and displacement signals measured by the speed detection unit and the displacement detection unit are connected to the signal pickup and control unit. This unit can perform operations and integration on the two signals. The signal pickup and control unit outputs a control signal and sends it to the force feedback execution unit; the torquer coil in the force feedback execution unit is placed in the torquer magnet. When current flows through it, it can generate a force perpendicular to the coil to offset the inertial force on the pendulum assembly, pull the pendulum assembly back to the equilibrium position, and achieve force balance; at this time, the inertial force applied to the pendulum assembly is equal to the electromagnetic force in the coil; when the pendulum assembly achieves force balance, the external acceleration information is obtained by detecting the current in the coil, thereby achieving acceleration measurement.

2. The system according to claim 1, characterized in that The speed detection coil (11) is formed by winding a plurality of turns of conductive cables with insulating outer skins.

3. The system according to claim 1, characterized in that The displacement sensors selected by the displacement detection unit include capacitive, photoelectric and grating displacement sensors.

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