Application of gyroscope in directional measurement of long-distance subway tunnel

 

Orientation control is particularly important in the directional measurement of long-distance subway tunnels, and is a necessary condition to ensure the smooth penetration of the tunnel. The conventional directional measurement method is to use contact measurement or wire measurement to transmit the orientation. Inertial orientation has incomparable advantages that conventional measurement methods. This article proposes The north-seeker orientation was applied in the directional measurement of long-distance subway tunnels, which verified the effectiveness of the north-seeker in the directional measurement of long-distance cross-sea tunnels.

In order to improve the penetration accuracy of subway tunnels, many rail transit (subway) systems have recently introduced the highest. Accurate, gyroscopic north finder used for directional measurement in subway tunnels.In the construction measurement of subway tunnels, the measurement accuracy of the underground conductor control network is often related to the penetration of the tunnel.Error, high-precision penetration is very important for track engineering construction.

The gyro north finder is a measuring device that finds the true north value of a certain location. It is combined with known ground control

points, which can provide precise direction values for underground conductor control points. Underground conductors are generally connected through shafts

System survey introduces the coordinates of ground control points into the underground. Due to the limitation of shaft size, ultra-short

While controlling the direction of tunnel excavation, the one-way excavation length is too long in some sections.

These conditions have laid hidden dangers for the smooth penetration of the subway tunnel. Therefore, small-sized north seekers are widely favored: for example, ER-MNS-06, with a size of only 44.84×38.88×21.39mm, can be applied to most excavation fields.

The ER-FNS-02 gyro north finder introduced this time is 1 to 3 times more accurate than traditional measurement, with an accuracy of 0.02° to 0.1°. In vertical shafts, the accuracy is more reliable and has greater improvement.

Technicians from the rail transit third-party measurement project tested the orientation accuracy of the gyro north finder when orienting the tunnel. Through on-site testing, it was found that its orientation accuracy was much higher than the accuracy requirements for the tunnel's lateral penetration error required by the specification. This new technology will be used in more rail transit construction.

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Application of Tilt Sensor in Dam Safety Monitoring

This paper mainly introduces the application of tilt sensor in dam safety monitoring and its role in the whole monitoring system. Dam safety monitoring system is mainly composed of monitoring instruments and measuring points, among which the monitoring instruments mainly include: dam deformation monitor, dam osmometer, dam displacement monitor and so on. The measuring points mainly include: horizontal displacement of dam foundation, slope, horizontal displacement of dam top, water level in front of dam, water level behind dam and so on. Dam safety monitoring system is a dynamic monitoring system, which is a comprehensive understanding of dam operation, so as to find problems in time and ensure the safety of dam operation. In order to monitor and analyze the safety state of the dam in real time, a perfect monitoring system must be established.

1. Overview of the system

The dam safety monitoring system is generally composed of monitoring instruments and measuring points, among which the monitoring instruments mainly include: dam deformation monitor, dam osmometer, dam displacement monitor and so on. The measuring points mainly include: the water level in front of the dam, the horizontal displacement of the dam top, the horizontal displacement of the dam foundation, the water level in front of the dam and the water level behind the dam. The tilt sensor based on single chip microcomputer is used to measure the tilt angle of the dam.

The inclination of the dam is monitored by the tilt sensor in real time, and the data is uploaded to the host computer through the serial port. By analyzing these data, the host computer can realize the analysis of dam safety status. At the same time, the host computer can save and remotely access the collected data to realize the remote monitoring function. The system supports simultaneous monitoring of up to 4 measuring points and can provide various types of alarm output.

2. The working principle of tilt sensor

Tilt sensor is a special kind of transmitter, and its internal sensitive element is composed of three symmetrical elastic sheets, which are sensitive to displacement in three directions respectively. When the three elastic plates are in equilibrium, there is no deformation inside the sensor, then the three elastic plates are consistent with the displacemence-sensitive sensitive axis, and the output voltage is zero. However, when an elastic sheet is subjected to external force, it moves, because the elastic sheet is asymmetric, it will cause deformation in three directions, and the output voltage will also change. At this time, the internal sensitive element will produce a corresponding displacement change. By detecting this change in displacement, the tilt angle of the object can be measured.

The tilt sensor is mainly composed of housing, sensing element, measuring circuit and power supply. The following is a detailed introduction to the structure of each part:

3. System composition

The system mainly consists of the following parts:

3.1 Monitoring equipment, mainly an inclination sensor and a data collector.

3.2 Communication equipment, mainly including GPRS, 4G wireless transmission equipment and solar power equipment.

3.3 Computers and computers are mainly used for storing data, running programs and setting various parameters.

3.4 Software, mainly used for data analysis and processing, to provide reliable technical basis for the project.

3.5 Software platform, mainly used for real-time data display, collection and the setting of various parameters.

3.6 Solar power supply is mainly used for power supply.

4. System function

4.1 can be operated remotely, timely view the operating status of the system.

4.2 through the database, the dam data can be queried, statistical analysis, remote maintenance, etc.

4.3 the data can be remotely managed, and the operation status of the dam can be mastered at any time.

4.4 data can be exported, and the exported data is transmitted to the computer through the network.

4.5 can be collected data for remote alarm, and send alarm information to the relevant personnel.

4.6 the system has good compatibility, and can be connected with other equipment.

4.7 the collected data can be transmitted to the relevant departments through the wireless network, in order to find the problem in time and solve the problem.

4.8 the system has good scalability and compatibility, you can add or modify the database according to user needs.

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Accelerometer Classification

 

An accelerometer is a sensor that measures the motion of an object in terms of acceleration. The acceleration measured by the accelerometer includes the change of the speed of the general object (linear acceleration), the low-frequency shaking of the object, and the high-frequency vibration. Therefore, there are many kinds of accelerometers, from accelerometers that detect heavy static acceleration to 10KHz high-frequency response accelerometers. Generally referred to as "accelerometer", "acceleration sensor", etc.

There are many types of accelerometers:

According to the measurement quality of displacement, there are linear accelerometers (measuring the mass of line displacement) and pendulum accelerometers (detecting the rotation of mass around the support axis).

According to the material, silicon accelerometers quartz accelerometers and metal accelerometers, of which quartz accelerometers are the most widely used, it has the advantages of high precision, high sensitivity and high stability, play the quartz material wear resistance, high temperature resistance characteristics make it popular in the field of aerospace and inertial navigation system. For example, ER-QA-03A not only achieves 10-50μg in zero-bias stability, but also achieves 10-30μg/g2 and 15-50 PPM in second-order nonlinearity and scale factor, respectively.

According to the composition of the measuring system, there are open loop type and closed loop type. The measuring system of open-loop accelerometer is open-loop, which is poor in anti-interference ability and accuracy. The closed-loop accelerometer has a compensatory system, strong anti-interference ability, high precision and large range. ER-QA-03B uses a closed-loop measurement system with zero bias stability of 10-30μg, scale factor and second-order nonlinearity of 15-50 PPM and 10-30μg/g2, respectively.

According to working principle, there are vibrating string type, vibrating beam type and pendulum type gyro accelerometer.

There are single-axis, two-axis and three-axis accelerometers, depending on the number of input axes.

According to the sensor components are classified into piezoelectric, piezoresistive and potentiometer.

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How to choose MEMS IMU?

IMU (Inertial Measurement Unit) is an inertial measurement unit that can measure the three-axis acceleration and angular velocity of an object. It is generally used in the measurement part of the system to estimate the pose of the object. IMU generally includes a three-axis accelerometer and a three-axis gyroscope. The accelerometer detects the acceleration signal of the object on three independent axes of the carrier coordinate system, and the gyroscope detects the angular velocity signal of the carrier relative to the navigation coordinate system. The angular velocity and acceleration in space can solve the pose of the object. MEMS IMU is cheap and small, and is widely used in many fields such as navigation, drones, VR, robots, and smart bracelets. The detection accuracy of the IMU is very important to the overall performance of the system. If the noise detected by the IMU is very noisy, then the feedback the system gets is wrong, just like human eyes, ears and other sense organs get wrong information. How can we move freely? The bottom layer of the system is the foundation. If the bottom layer of the system is unstable, it will be difficult for the upper layer to function well. ERICCO has always strictly controlled the accuracy of IMU and has been pursuing the improvement of IMU system. Next, ERICCO will also launch new high-precision IMU products.

1. Zero bias temperature hysteresis characteristics

The zero-bias temperature hysteresis characteristic means that the corresponding zero-bias of the IMU is inconsistent during the heating phase and the cooling phase. Some IMU data manuals will give the zero-bias temperature hysteresis characteristic curve, and some will not. It is best to test it when applying the IMU. Since the IMU zero bias estimate is calibrated based on temperature (the IMU calibration algorithm is introduced in detail), if the temperature lag difference is not too large, the calibration accuracy will be relatively high; if the IMU zero bias hysteresis value is too large, the IMU zero calibration error will be relatively high. large, thus affecting the fusion effect.

2.Vibration characteristics

In the case of external vibration, the variation characteristics of IMU deviation with vibration frequency. Some MEMS IMU chips have abnormal frequency characteristics under high-frequency excitation. For applications such as rotor drones that are prone to high-frequency vibrations, vibration characteristics are generally tested. If the IMU frequency characteristics are abnormal, you can consider it. Add shock absorbers.

3. Effect of repeated power-on on IMU deviation

Ideally, it is thought that under the same external conditions, the bias of the IMU will remain the same each time it is powered up. In fact, under the same external conditions, the bias of the IMU will be different every time the IMU is powered up. If the difference is relatively large, it will be zero. The bias estimation error will be relatively large, affecting the fusion effect.

4. The impact of stress on prejudice

The influence of stress on IMU includes: the influence of stress moment on offset, and the influence of different stresses on offset. The stress mainly comes from: the stress exerted by the PCB board on the IMU chip and the stress exerted by the temperature control device on the IMU chip. If the IMU bias is too sensitive to the impact of stress, it will also affect the zero drift estimation error, thus affecting the fusion effect.

5. Impact of impact on zero deviation

When the IMU is subjected to an external impact (on the order of tens of G), it is possible that the IMU will get stuck or the deviation will change. In general, testing should be done.

6. Nonlinear factor (%Fs)

Ideally, we consider the sensor data to be linear over this range. In fact, the sensor changes are non-linear. As shown in Figure 2, the nonlinear characteristics of the IMU need to be tested before use. If the nonlinearity is too severe, nonlinear calibration should be performed. There are many such calibration methods, such as proportional calibration, quadratic fitting calibration, etc.

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How to Select Tilt sensor?

As the name suggests, the tilt sensor is to measure the angle of the carrier through sensor technology. The application of tilt sensor is more and more extensive, and it has been widely used in the attitude detection field such as radar antenna angle measurement, bridge, mountain, dam, tall building, engineering vehicle robot arm angle measurement. So how do we choose a suitable tilt sensor?

1. Select by application environment

If you want to apply to a static environment or uniform motion environment, choose a static tilt sensor, if your actual use of the environment is dynamic, non-uniform motion, then choose a dynamic tilt sensor.
1.1 Inclination sensors are divided into two types according to the principle, one type can be called static inclination sensors, which are more widely used in the monitoring of static or quasi-static objects such as DAMS, bridges, towering buildings. For example, the ER-TS-3160VO is a static inclination sensor that can measure the tilt angle of an object in a static state, and can be used to check the tilt angle of bridges, DAMS, and monitor the angle of various construction machinery. It has the characteristics of small size, strong impact resistance and vibration resistance.
1.2 Another type is the dynamic inclination sensor, which adopts the latest inertial navigation technology to avoid the loss of accuracy of the sensor in the process of motion and vibration, and can be applied to vehicles, aircraft, construction machinery, robots and other motion carriers to measure the attitude of the carrier with high precision in motion.

2. Select by transmission mode

If you have high requirements for environment, noise, and mobility, you can choose wireless, if you need high signal stability, long life, and low failure rate you can choose wired. According to the different data transmission mode, the inclination sensor can be divided into wireless and wired two kinds.

2.1 Wireless tilt sensors transmit tilt signals through wireless communication technology without cable connection, making them highly flexible. The main advantage of wireless tilt sensors is their flexibility and convenience. Since no wiring is required, the sensor can be easily installed wherever it is needed, regardless of laying cables. In addition, the wireless tilt sensor also has the advantages of high mobility, easy expansion and maintenance. For example, the ER-TS-12200-Modbus is a wireless inclination sensor that does not need to use a traditional cable to transmit inclination signals, but uses a lithium battery to power and wirelessly transmit inclination data via Bluetooth and ZigBee. This wireless digital signal transmission method eliminates the tedious wiring and noise interference caused by long cable transmission. However, wireless sensors also have some disadvantages, such as signal quality may be affected by radio interference, and signal stability and reliability may not be as good as wired sensors. Wireless inclinometer sensors can be widely used in bridge construction, transmission tower/signal tower tilt, dangerous buildings, ancient buildings, warehouse shelves, smart towns, smart lighthouses, fan tower tilt monitoring and other scenarios.

2.2 Wired inclination sensors usually use RS485 bus or other similar bus protocols to transmit inclination signals. RS485 is a serial communication protocol widely used in the field of industrial automation, which has the advantages of noise suppression and high signal quality. The main advantage of the wired inclinometer sensor is that the signal stability is high, and the signal quality is not easy to be disturbed by the wired transmission mode. In addition, wired sensors have long service life, low maintenance costs, and low failure rates. However, this sensor also has some disadvantages, such as the need to lay cables, high requirements for the field environment, and wiring difficulties may exist in some application scenarios. Wired inclination sensors can be widely used in construction, bridge, dam, shield jacking, rail transit, high-rise buildings, slope monitoring and other scenarios.

3. Select by the number of axes

According to the need to measure the inclination of several directions to choose, if it is to measure one direction, use a single axis, if it is to measure two directions (pitch and roll), choose a double axis.

What is the Difference Between an Accelerometer and a Vibration Sensor

 The difference of working principle

Acceleration sensors and vibration sensors look very similar in appearance, but there is a big difference in how they work.

An acceleration sensor measures the acceleration of an object over a given period of time, that is, the rate of change in the velocity of an object over a period of time. It obtains vibration information by measuring the motion state of the object.

The vibration sensor is to measure the amplitude, frequency and phase information of the vibration of the object, and diagnose the application through the characteristics of the vibration. It directly monitors the vibration of the object and is used to determine whether the equipment is in normal operation.

Acceleration sensor

An acceleration sensor is a common sensor used to measure the acceleration of an object. This sensor is manufactured using microelectromechanical system (MEMS) technology and can measure an object's acceleration, tilt Angle and static gravity. It is widely used in car navigation, smart phones, sports tracking and other fields. The working principle of the acceleration sensor is to estimate the speed and displacement of an object by measuring its acceleration.For example, the bias stability of ER-MA-5 is (1s standard deviation)(1σ)<20ug, and bias month repeatability is 200ug.

Vibration sensor

Vibration sensor is a kind of sensor mainly used in industrial automation, mechanical monitoring and other fields. It can measure key parameters such as vibration speed, displacement and acceleration of equipment or machines. The working principle of vibration sensor is to capture the vibration signal of the target to feedback its physical motion. Under normal circumstances, vibration sensors are widely used in mechanical fault diagnosis, process monitoring, equipment status assessment and other fields.

Application difference

Although both vibration sensors and acceleration sensors can be used to detect vibrations, they have different application scenarios. Vibration sensors are mainly used in industrial automation, mechanical monitoring and other fields, which can measure the speed, displacement and acceleration of vibration. The acceleration sensor is suitable for car navigation, smart phones, sports tracking and other fields, and can measure the acceleration of objects. In addition, vibration sensors are better suited for measuring low frequency vibrations than acceleration sensors, while acceleration sensors are better suited for high frequency vibrations than vibration sensors.

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Inertial Measurement Unit (IMU) Technology and Applications in UAVs

1: Definition and composition of IMU An inertial measurement unit (IMU) is a device that integrates sensors such as accelerometers and gyroscopes and is used to measure the linear acceleration, angular velocity and direction of objects. An IMU typically consists of a three-axis accelerometer, a three-axis gyroscope, and possibly a magnetometer. These sensors can capture the movement of the drone and provide accurate attitude information.

2: IMU technical principle and working method The working principle of IMU is based on the basic principle of inertial measurement. Accelerometers derive information about an object's velocity and displacement by measuring the linear acceleration experienced by an object. The gyroscope measures the angular velocity of the object and derives the rotation attitude of the object. Magnetometers can help determine the direction of an object. The IMU uses data from these sensors and processes it with filtering and fusion algorithms to provide accurate flight status information.

3: Application scenarios of IMU in drones IMU has a wide range of application scenarios in drones. First of all, IMU is one of the key technologies to realize UAV navigation and positioning, and can provide precise position and attitude information. Secondly, in the stability control of the drone, the IMU can help the drone maintain balance and offset external interference. In addition, IMU is also commonly used to implement functions such as autonomous flight, path planning, and obstacle avoidance of UAVs. The ER-MIMU-03 developed by Ericco uses high-quality and reliable MEMS accelerometers and gyroscopes. It communicates with the outside via RS422. The baud rate can be flexibly set between 9600 and 921600. The communication baud rate required by the user is set through the communication protocol. Equipped with X, Y, Z three-axis precision gyroscope, X, Y, Z three-axis accelerometer, with high resolution, it can output the original hexadecimal complement of X, Y, Z three-axis gyroscope and accelerometer through RS422 code data (including gyroscope hexadecimal complement) numerical temperature, angle, accelerometer hexadecimal temperature, acceleration hexadecimal complement); it can also output gyroscope and accelerometer data that have been processed by underlying calculations Floating point dimensionless value. The application fields are also relatively wide, and can be used in heading, pitch, and roll measurement in UAV AHRS; guidance, navigation and control of satellite antennas in tactical MEMS weapon systems, stabilization and pointing in target tracking systems, and autonomous machines and unmanned aerial vehicles. Robot control and orientation in driving vehicles, etc.

Inertial measurement unit (IMU) technology in drones plays a vital role in the modern drone field. By in-depth understanding of the principles, composition and application scenarios of IMU, we can better understand the flight control system of drones and apply it to various practical scenarios.

In the future, with the continuous development and innovation of drone technology, IMU technology will also be further improved and improved. Through continued research and exploration, we can expect the emergence of more accurate and stable drone navigation and control systems. The widespread application of drones will bring more convenience to our lives, and at the same time promote the development and progress of the entire aviation field.

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