What Is A Flexible Pendulum Accelerometer?

Principle
Pendulum accelerometer is a kind of acceleration measuring instrument based on physical principle. The measurement principle is to use a simple pendulum system to calculate the acceleration by measuring the oscillation period and amplitude change of the pendulum. Pendulum accelerometers usually consist of a heavy weight and a slender pendulum bar. When the acceleration is applied to the pendulum, the weight will be subjected to the action of inertial force, which causes the pendulum to bend. This bending will cause the oscillation period and amplitude of the pendulum rod to change.

Adopt a flexible support pendulum accelerometer. The pendulum assembly is connected to the meter housing with two flexible rods. The bending stiffness of the flexible rod around the output shaft is low, while the stiffness in other directions is high. Its basic working principle is similar to the liquid floating pendulum accelerometer. This system has a high-gain servo amplifier that keeps the pendulum assembly working near zero. In this way, the bending of the flexible rod is very small, and the elastic moment introduced is also small, so the instrument can achieve high accuracy. There are two types of accelerometers, oil-filled and dry. The oil-filled interior is filled with a highly viscous liquid as a damping liquid, which can improve the dynamic characteristics of the instrument and improve its resistance to vibration and shock. The dry accelerometer adopts electromagnetic damping or air film damping, which is convenient for miniaturization, reducing costs and shortening the startup time, but the accuracy is lower than that of the oil-filled type.

In order to measure acceleration, pendulum accelerometers need to accurately measure the vibration period and amplitude of the pendulum. Generally speaking, the vibration period can be measured by timers and sensors, while the amplitude can be measured by photoelectric or piezoelectric sensors.

In practical applications, pendulum accelerometers are often used to measure mechanical vibration and seismic activity. Because of its high measurement accuracy and strong reliability, it is widely used in various industrial and scientific research fields. It should be noted that when using a pendulum accelerometer for acceleration measurement, it needs to be calibrated. The purpose of calibration is to compare the output value of the pendulum accelerometer with the real acceleration value to ensure the accuracy and reliability of its output value.

Application

Automobile safety system

Accelerometers play an important role in automobile safety system. For example, when a car is in a collision, the accelerometer can detect changes in the vehicle's acceleration and send a signal to the Ankin airbag system to inflate it at the appropriate time, protecting the driver and passengers. In addition, the accelerometer can also be used in vehicle stability control systems to help the vehicle remain stable in emergency situations.
Aerospace
Accelerometers are also widely used in the aerospace field. During a rocket launch, for example, an accelerometer can measure changes in the rocket's acceleration to help control the trajectory of the rocket. In addition, the accelerometer can also be used in the aircraft's autopilot system to help maintain stability.

Robot state control

Acceleration is an important state variable for robot control systems. For the position control of each degree of freedom, the acceleration of the robot can be obtained by using the accelerometer, the velocity of the robot can be obtained by integrating the acceleration once, and the position of the robot can be obtained by integrating the acceleration twice, so as to form feedback correction according to these information. In the control of robot system, the output of accelerometer can not only be used as the acceleration state variable directly for the state feedback of modern control theory for system synthesis, but also as the feedback correction of classical control theory, which is equivalent to PID correction in series correction (that is, lead-lag correction).

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