A north finderhttps://www.ericcointernational.com/inf … inder.html is a type of compass that is used to find the true north value of a certain position. Gyro North finder, also known as gyro compass, is an inertial measurement system that uses gyro principle to determine the projection direction of the Earth’s rotation rate in the local horizontal plane (that is, true north position). Its north finding process requires no external reference. In addition to being limited by high latitude, its north finding survey is not affected by weather, day and night time, geomagnetic field and site visibility conditions.
Gyroscope north finder can be divided into the following three types:
A north finder using a two-degree-of-freedom gyroscope as an Earth rotation sensor (e.g. a pendulous gyro north finder)
A north finder using a single-axis rate gyroscope as a sensor (e.g., strap down gyroscope north finder)
Platform north finding system

As a key technology of navigation system, The low-cost 3-axis FOG North finder ER-NFS-03https://www.ericcointernational.com/nor … ining.html  consists of an inertial measurement unit (IMU), a digital signal processing unit, and a mechanical component mechanism. It can provide true north azimuth for the carrier north-seeking technology is not only widely used in satellite, missile, artillery, ship inertial navigation and other fields, known as attitude measurement and national defense high-tech field, but also in geophysical exploration, coal mining, Geodetic surveying and other fields are also widely used. North finder is one of the important equipments using north-seeking technology, and it has also become a necessary measurement method.
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Range – In order to get reasonable sensitivity and confirm the range of gyrohttps://https://www.ericcointernational … 06021.html is within in your are expecting, meanwhile make sure the max angular rate of gyros are not exceed you are expecting .

Interface – Actually it has not too much difference in this section, most of gyros what we have feature an analog output, less gyro has a digital interface -either SPI or I2C.

Number of axes measured – Gyros are a little behind curve when it compared with accelerometers, most of gyros are either1 or 2 axis before 3 axis appeared on the market. You need to pay more attention to which of the three axes the gyro will measure. For example, some two axis gyros will measure pitch and roll, but others measure pitch and heading.

Power Usage – You have to consider how much the power of gyro will consume if your project is battery powered. Usually the request of current consumption should be within100s of μA range.
Now there is a high-precision mems gyroscopehttps://www.ericcointernational.com/gyr … -gyro.html directly available for you to choose.
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GPS is indispensable to the current vehicle positioning technology. Due to the error of GPS, multipath and update frequency is low, we can’t just rely on GPS positioning. Inertial sensor has high update frequency, it can be complementary with GPS. Using sensor fusion technology, we can be the integration of GPS and inertial sensor data, from each director, in order to achieve better location performance.

Inertial navigation system (INS)https://www.ericcointernational.com/inf … 07653.html detecting acceleration and rotation motion of high frequency (1 KHZ) sensor, the inertial sensor data processing after the displacement and rotation of the vehicle can drawn real-time information. INS have bias and noise problems affect the outcome. By using a sensor fusion technique based on kalman filtering, we can be the integration of GPS and inertial sensor data, from each director, in order to achieve better location performance. Attention because of the unmanned for reliability and security requirement is very high, so based on GPS and inertial sensor positioning is not the only way of positioning in the unmanned, we also use LiDAR point cloud and high precision map matching, and locating methods such as visual mileage calculation method for various positioning method to correct each other to achieve more accurate results.
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The performance index of a gyro north-seeking device depends on two aspects: north-seeking precision and north-seeking time. The traditional north-seeking device has a good performance in north seeking performance, but its equipment is expensive and heavy. With the continuous optimization of the performance and accuracy of MEMS gyroscope, the future gyro north-seeking device will develop towards the trend of high north-seeking accuracy, low north-seeking time, low cost, small size and high operational flexibility. MEMS IMUhttps://www.ericcointernational.com/nor … eeker.html has been widely used in general civil navigation, tactical weapons and unmanned systems because of its advantages of small size, low cost, high reliability and easy installation.

IMU in inertial navigation system

The inertial navigation system is an auxiliary navigation system that uses accelerometers and gyroscopes to measure the acceleration and angular velocity of objects and uses computers to continuously estimate the attitude, speed and position of objects through navigation solutions. Inertial navigation system is an inseparable system in the modern navigation field.

MEMS is an industrial technology that merges microelectronics and mechanical engineering with a range of operations on the micron scale. Along with the improvement of the silicon semiconductor process for making integrated circuits, the micromechanical manufacturing technology of micro-machinery, micro-sensor and micro-actuator emerged in the 1980s, making MEMS technology become a real product. The achievements of MEMS technology in the field of inertial navigation are reflected in the MEMS IMU, which is composed of three silicon micro gyroscopes, three silicon micro accelerometers and the corresponding control circuit. MEMS IMU has the advantages of small size, light weight, easy mass production and low cost, and has been widely used in the general civil and some unmanned system navigation fields. But its disadvantages are obvious: relatively low accuracy, bias stability is about 10~20°/h.

But Ericco’s ER-MIMU-01&ER-MIMU-05 use High Performance North Seeking MEMS Gyroscope(ER-MG2-100) that can reach 0.1°/h, which is lower than the lowest precision IMU of many large companies, and can reflect its high performance in the complex environment.
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The high-precision north seeker is a high-precision dual axis dynamically tuned gyroscope, which can independently determine the true north direction value of the attached carrier by measuring the earth’s rotation angle velocity, and is not disturbed and affected by the external magnetic field or other environment. In addition, it can also measure and correct the horizontal angle in combination with the acceleration. It is mainly used in the fields of drilling director, drilling equipment control, ocean survey, three-dimensional scanner, radar, antenna, military vehicles and so on.
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It is mainly used to quickly and independently determine the true north direction. After obtaining the azimuth angle, the equipment starts to move and can continuously output the changing dynamic inclination and azimuth angle. MEMS gyroscope is used for north seeking and built-in IMU is used for inclination measurement and azimuth estimation. It has the characteristics of small size, low price, low power consumption, long service life and high reliability.

MEMS gyroscope, accelerometer, mechanical rotation device and signal solving circuit are composed. The micro gyroscope north finder uses the rate gyroscope to measure the rotation speed of the earth, so as to calculate the azimuth. The product collects the output of the gyroscope under different azimuth angles, and carries out signal processing to calculate the azimuth of the equipment
Among them, IMU’s inertial measurement unit is an important part of which the internal MEMS Accelerometer is also one of the components of IMU inertial measurement unit, which is mainly used as the acceleration in three directions of x\y\z axis, so as to cooperate with gyroscope and calculate the correct angle required by north finder.
Dynamic gyro north finder is a gyroscope that uses strapdown compass effect to solve true north direction.
The dynamic gyro north finder is composed of three-axis dynamically adjustable gyro, three-axis plus meter, data acquisition and processing module, secondary power supply, optocoupler isolated input and output serial port circuit and other related structural parts. After power on and startup, the product enters the preheating time. After the preheating time, the product turns into initial self-alignment under the condition of moving base. After the north finder is powered on for 30 minutes, the aircraft carrying the product can sail at sea.
The dynamic gyro north finder is mainly used in navigation. When sailing, the dynamic gyro north finder will timely output the heading angle, roll angle and pitch angle.


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Ericco provides north finding system solutions. We have fog and MEMS north seeker, If you have any needs, please feel free to contact us.

В отличие от магнитного севера, который обозначается компасом, истинный Север — это направление, которое указывает прямо на географический северный полюс. Она определяется как линия от любой точки на поверхности земли до северного полюса. Все линии долготы ведут к истинному северу, где они в конечном итоге пересекаются на северном полюсе. В современных инженерных обследованиях истинный Север часто используется в качестве данных для определения подшипника. Поэтому люди использовали множество различных методов поиска «севера», таких как астрономический поиск севера, геомагнитный поиск севера, инерционный поиск севера и электромагнитный поиск севера.
В 1852 году французский ученый фуко джей предложил использовать гироскоп, чтобы найти Север. Ограниченный техническими условиями в то время, он использовал метод перетягивания веревки людьми, чтобы управлять гиро вращения, который не мог соответствовать требованиям севера поиска с точки зрения вращения и стабильности точности. Несмотря на то, что эксперимент в конечном итоге оказался неудачным, он открыл новую главу в человеческом инерционном поиске на севере.
В 1908 году немецкие Anschutz H и Schuler, наконец, разработали первый в мире практический гирокомпас. Впервые в истории человечества механические принципы были успешно применены для достижения северного поиска.
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you can use north finder
for more info :https://www.ericcointernational.com/application-case/fog-north-finder-for-mining.html
Mine north finder is based on three-axis integrated fiber optic gyro and three-axis accelerometer, which can complete the initial alignment, attitude maintenance function, real-time output carrier attitude reference value.

The invention is a method for measuring the attitude of a downhole drilling machine. It is fixed on the track of the rig propeller. After starting work, the angular velocity of the sensitive rotational motion and the acceleration of the translational motion are solved in the posture of the processor to obtain the attitude of the rig. Then, the inertial measurement system continuously measures the current rig’s current position. Attitude until the end of the measurement. The invention can automatically and quickly and accurately measure and display the posture information of the downhole drilling rig without relying on the external information by means of the external information.

This North Finder is specially developed for coal mines. It reduces the cost of using the North Finder and has stable performance. Many companies have a strong interest in it and express their intention to cooperate with us.

MEMS gyroscope is a kind of instrument used to measure and maintain direction, it has a wide range of applications in aviation, aerospace, navigation, seismology and other fields. The precision of MEMS gyroscope is one of the important indexes to measure its performance, which directly affects the use effect and reliability of the gyroscope.
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The precision indexes of MEMS gyroscope mainly include zero bias, drift, stability and repeatability. Among them, zero bias refers to the non-zero signal output by the gyroscope in the static state, which will cause the measurement result of the gyroscope to deviate from the true value. Drift refers to the non-zero value number output by the gyroscope in the state of motion, which will cause the measurement results of the gyroscope to change with time. Stability refers to the stability of the performance of the gyroscope in the process of long-term use, which directly affects the reliability and service life of the gyroscope. Repeatability refers to the consistency of the output results when the gyroscope measures the same physical quantity for many times, and it is one of the important indexes to evaluate the measurement accuracy of the gyroscope.

The main performance parameters of MEMS gyroscope

1. Zero bias stability

Zero deviation refers to the output of the gyroscope in the zero input state, which is expressed by the mean value of the output for a long time, which is equivalent to the input angular rate, that is, the degree of dispersion of the observed value around the zero deviation, such as 0.005 degree/sec means that it will drift 0.005 degree per second. Ericco’s ER-MG2-50/100 High Performance North Seeking MEMS Gyroscope‘ zero bias stability can reach 0.1deg/hr, zero bias repeatability is 0.1deg/hr, it can be seen that its measurement accuracy is very high. The long-term steady-state output in the zero-input state is a stationary random process, that is, the steady-state output will ebb and flow around the mean (zero-bias), which is conventionally represented by the mean square error, which is defined as zero-bias stability. The initial zero bias error can be understood as a static error, which does not fluctuate with time and can be calibrated with software.

2. Range (dynamic range)

The range of a gyroscope is usually expressed as the maximum of the positive and negative input angular rates, such as +/-300 degree/sec. The larger the value, the stronger the ability of the gyroscope to be sensitive to the angular rate. In the range of this input angular rate, the nonlinearity of the gyroscope scale factor can meet the specified requirements, and the range of the gyroscope can usually be configured.

3. Sensortivity resolution

Sensitivity (resolution) represents the increment of the minimum input angular rate that can be perceived at a specified input angular rate, for example: 0.05 degree/sec/LSB. In general, the greater the measuring range of a MEMS gyroscope, the sensitivity will decrease accordingly.

4. Scale factor

The scale factor (scaling factor) is the ratio of the gyroscope output to the input angular rate. This ratio is expressed as the slope of a specific line, which is obtained by fitting the input and output data measured over the entire range of input angular rates using the least square method.

5. Degree of nonlinearity

The nonlinearity is the ratio of the maximum deviation of the gyroscope output relative to the line fitted by the least square method in the range of the input angular rate to the maximum output, which represents the deviation degree of the actual input and output data of the gyroscope and determines the reliability of the fitted data.

6. Linear acceleration sensitivity

The linear acceleration sensitivity reflects the gyroscope’s sensitivity to acceleration, and the unit is degree/sec/g.

7. Vibration sensitivity

Vibration sensitivity refers to the sensitivity of the gyroscope to vibration, and the unit is degree/sec/g2. The less sensitive the gyroscope is to linear acceleration and vibration, the better the performance of the gyroscope and the more effective the built algorithm will be.

8. Bias voltage sensitivity

Bias voltage sensitivity refers to the sensitivity of the gyroscope’s output to changes in the power supply, such as: 0.03degree/sec/V, that is, how much the output angular rate changes for every 1V change in the power supply.

9. Bandwidth

Bandwidth refers to the frequency range in which the gyroscope can accurately measure the input angular rate, and the larger the range, the stronger the dynamic response capability of the gyroscope.

10. Self-test function

The self-test function automatically tests the mechanical and CMOS circuit parts of the device before use to provide system robustness.

11. Power consumption

Power consumption includes power consumption when the gyroscope is running at different resolutions or different data output rates, sleep power consumption. This indicator is particularly important in low-power applications such as wearables and Internet of Things applications.

12. Impact survivability

Impact survivability refers to the ability of the gyroscope to withstand acceleration shocks of different degrees, for example, the gyroscope ensures the normal operation of the system after the 2000g acceleration impact. Considering that the application environment of the gyroscope may receive a large impact, this indicator is particularly important, generally the gyroscope is more than its acceleration range will be hung up, must be restarted to work normally.

13. Working temperature range

The mechanical architecture of MEMS gyroscopes determines that temperature will affect the output of data, and exceeding the operating temperature range may cause large deviations in the data output.

14. Packaging error

Package error is the Angle between the diagonal of the bare piece and the diagonal of the package.

In order to improve the accuracy of MEMS gyroscope, a series of measures need to be taken. First of all, it is necessary to select high-quality gyroscope devices to ensure that their manufacturing process and quality meet the requirements. Secondly, it is necessary to carry out accurate calibration and debugging to eliminate errors such as zero bias and drift. In addition, it is also necessary to adopt a suitable installation method and use environment to avoid external interference and influence. The ER-MG2-50/100 is a single-axis MEMS angular rate north seeking sensor (gyroscope) designed as an advanced differential sensor that rejects the effects of linear acceleration, enabling the ER-MG2-50/100 to operate in extremely harsh environments where shock and vibration are present. This high-precision north finder is designed for north finding, pointing, and initial alignment in logging/gyroscopes, mining/drilling equipment, weapon/UAV launch systems, satellite antennas, target tracking systems, etc.

Finally, regular maintenance and overhaul should be carried out to ensure that the performance of the gyroscope is stable and reliable.

MEMS gyroscope is a kind of instrument used to measure and maintain direction, it has a wide range of applications in aviation, aerospace, navigation, seismology and other fields. The precision of MEMS gyroscope is one of the important indexes to measure its performance, which directly affects the use effect and reliability of the gyroscope.
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The precision indexes of MEMS gyroscope mainly include zero bias, drift, stability and repeatability. Among them, zero bias refers to the non-zero signal output by the gyroscope in the static state, which will cause the measurement result of the gyroscope to deviate from the true value. Drift refers to the non-zero value number output by the gyroscope in the state of motion, which will cause the measurement results of the gyroscope to change with time. Stability refers to the stability of the performance of the gyroscope in the process of long-term use, which directly affects the reliability and service life of the gyroscope. Repeatability refers to the consistency of the output results when the gyroscope measures the same physical quantity for many times, and it is one of the important indexes to evaluate the measurement accuracy of the gyroscope.

The main performance parameters of MEMS gyroscope

1. Zero bias stability

Zero deviation refers to the output of the gyroscope in the zero input state, which is expressed by the mean value of the output for a long time, which is equivalent to the input angular rate, that is, the degree of dispersion of the observed value around the zero deviation, such as 0.005 degree/sec means that it will drift 0.005 degree per second. Ericco’s ER-MG2-50/100 High Performance North Seeking MEMS Gyroscope‘ zero bias stability can reach 0.1deg/hr, zero bias repeatability is 0.1deg/hr, it can be seen that its measurement accuracy is very high. The long-term steady-state output in the zero-input state is a stationary random process, that is, the steady-state output will ebb and flow around the mean (zero-bias), which is conventionally represented by the mean square error, which is defined as zero-bias stability. The initial zero bias error can be understood as a static error, which does not fluctuate with time and can be calibrated with software.

2. Range (dynamic range)

The range of a gyroscope is usually expressed as the maximum of the positive and negative input angular rates, such as +/-300 degree/sec. The larger the value, the stronger the ability of the gyroscope to be sensitive to the angular rate. In the range of this input angular rate, the nonlinearity of the gyroscope scale factor can meet the specified requirements, and the range of the gyroscope can usually be configured.

3. Sensortivity resolution

Sensitivity (resolution) represents the increment of the minimum input angular rate that can be perceived at a specified input angular rate, for example: 0.05 degree/sec/LSB. In general, the greater the measuring range of a MEMS gyroscope, the sensitivity will decrease accordingly.

4. Scale factor

The scale factor (scaling factor) is the ratio of the gyroscope output to the input angular rate. This ratio is expressed as the slope of a specific line, which is obtained by fitting the input and output data measured over the entire range of input angular rates using the least square method.

5. Degree of nonlinearity

The nonlinearity is the ratio of the maximum deviation of the gyroscope output relative to the line fitted by the least square method in the range of the input angular rate to the maximum output, which represents the deviation degree of the actual input and output data of the gyroscope and determines the reliability of the fitted data.

6. Linear acceleration sensitivity

The linear acceleration sensitivity reflects the gyroscope’s sensitivity to acceleration, and the unit is degree/sec/g.

7. Vibration sensitivity

Vibration sensitivity refers to the sensitivity of the gyroscope to vibration, and the unit is degree/sec/g2. The less sensitive the gyroscope is to linear acceleration and vibration, the better the performance of the gyroscope and the more effective the built algorithm will be.

8. Bias voltage sensitivity

Bias voltage sensitivity refers to the sensitivity of the gyroscope’s output to changes in the power supply, such as: 0.03degree/sec/V, that is, how much the output angular rate changes for every 1V change in the power supply.

9. Bandwidth

Bandwidth refers to the frequency range in which the gyroscope can accurately measure the input angular rate, and the larger the range, the stronger the dynamic response capability of the gyroscope.

10. Self-test function

The self-test function automatically tests the mechanical and CMOS circuit parts of the device before use to provide system robustness.

11. Power consumption

Power consumption includes power consumption when the gyroscope is running at different resolutions or different data output rates, sleep power consumption. This indicator is particularly important in low-power applications such as wearables and Internet of Things applications.

12. Impact survivability

Impact survivability refers to the ability of the gyroscope to withstand acceleration shocks of different degrees, for example, the gyroscope ensures the normal operation of the system after the 2000g acceleration impact. Considering that the application environment of the gyroscope may receive a large impact, this indicator is particularly important, generally the gyroscope is more than its acceleration range will be hung up, must be restarted to work normally.

13. Working temperature range

The mechanical architecture of MEMS gyroscopes determines that temperature will affect the output of data, and exceeding the operating temperature range may cause large deviations in the data output.

14. Packaging error

Package error is the Angle between the diagonal of the bare piece and the diagonal of the package.

In order to improve the accuracy of MEMS gyroscope, a series of measures need to be taken. First of all, it is necessary to select high-quality gyroscope devices to ensure that their manufacturing process and quality meet the requirements. Secondly, it is necessary to carry out accurate calibration and debugging to eliminate errors such as zero bias and drift. In addition, it is also necessary to adopt a suitable installation method and use environment to avoid external interference and influence. The ER-MG2-50/100 is a single-axis MEMS angular rate north seeking sensor (gyroscope) designed as an advanced differential sensor that rejects the effects of linear acceleration, enabling the ER-MG2-50/100 to operate in extremely harsh environments where shock and vibration are present. This high-precision north finder is designed for north finding, pointing, and initial alignment in logging/gyroscopes, mining/drilling equipment, weapon/UAV launch systems, satellite antennas, target tracking systems, etc.

Finally, regular maintenance and overhaul should be carried out to ensure that the performance of the gyroscope is stable and reliable.

1.Definition of Gyroscope

Gyroscope, a gyroscope device with various functions made by people using the mechanical properties of gyroscope, is widely used in various fields such as science, technology and military. For example: gyrocompass, directional indicator, shell turnover, nutation of the gyroscope, the earth in the sun (moon) torque under the precession.
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2.Gyroscope Classification

Today’s gyroscopes are mainly Piezoelectric gyroscopes, micromechanical gyroscopes, fiber optic gyroscopes, dynamically-tuned gyroscopes, laser gyroscopes, all electronic, can be combined with accelerometers, reluctance chips, GPS, inertial navigation control systems.

By use:

It can be divided into sensing gyroscope and indicating gyroscope. Sensing gyroscopes are used as horizontal, vertical, pitch, heading and angular velocity sensors in automatic control systems of aircraft motion. Indicating gyroscopes are mainly used to indicate flight status and are used as piloting and piloting instruments.

By function:

Various instruments or devices made of gyroscope’s dynamic characteristics mainly include the following:

Gyro directioner

A gyroscopic device that gives an indication of turning Angle and heading of a flying object. Manual adjustment against a precision compass should be made at regular intervals (e.g. 15 minutes).

Gyro compass

A three-degree-of-freedom gyroscope for finding and tracking geographic meridional planes for navigational and flying objects.

Gyro vertical instrument

An instrument that uses pendulum sensors to apply correction torque to a three-degree-of-freedom gyroscope to indicate the vertical line of the ground is also called gyro level. Gyro verticalometer is another kind of vertical indicator or measuring instrument used in aviation and navigation system besides gyro pendulum.

Gyroscopic stabilizer

A gyroscope to stabilize the ship. Once the hull tilts, the small gyroscope precesses along its straight axis, so that the control motor on the main gyroscope frame axis starts in time, and the active torque in the same direction as the original gyroscope torque is applied on the axis, so as to strengthen the precession of the frame and the stability effect of the resulting precession on the hull.

Rate gyroscope

A two-degree of freedom gyro device used to directly determine the angular velocity of a vehicle. Rate gyro and integral gyro are widely used in remote measurement system, automatic control and inertial navigation platform.

Gyro stabilized platform

With gyroscope as the core component, the device that keeps the stabilized object stable relative to the given attitude in inertial space. According to the number of rotating axes that an object can maintain stability, gyrostabilized platforms can be divided into uniaxial, biaxial and triaxial gyrostabilized platforms. Gyro stabilized platform can be used to stabilize instruments and equipment that need accurate orientation, such as measuring instruments, antennas, etc., and has been widely used in aviation and navigation system and fire control, radar universal support.

4.Gyroscope of application

Gyro instrument can not only be used as indicator, but more importantly, it can be used as a sensitive element in automatic control system, which can be used as signal sensor.

According to the need, the gyroscope instrument can provide accurate azimuth, level, position, speed and acceleration signals, so that the pilot or the automatic navigator can control the aircraft, ship or space shuttle and other vehicles to fly according to a certain course.

In the guidance of missile, satellite carrier or space exploration rocket, the signals are directly used to complete the attitude control and orbit control of the vehicle.

Gyroscopic instruments can be used as stabilisers to keep trains on monorail, to reduce the sway of ships in wind and waves, to stabilize cameras mounted on aircraft or satellites relative to the ground, and so on.

As a precision test instrument, gyro instruments can provide accurate bearing datums for surface installations, mine tunnels, underground railroads, oil drilling, and missile silos.

5.How to choose a gyroscope better

The factors we usually consider when choosing a gyroscope are based primarily on minimizing the maximum source of error-in most applications, vibration sensitivity, other parameters that can be easily enhanced by calibrating or averaging multiple sensors, and bias stability error being one of the smaller components of all gyro errors.

When looking at a high performance gyroscope data manual, the first thing most system designers consider is the bias stability specification. After all, this is what describes the bottom line of gyroscope resolution, so it is surely the best predictor of gyroscope performance. However, errors in real gyroscopes due to multiple sources make it impossible for users to take advantage of the high bias stability in the data manual. The only place to get this level of performance is on the lab bench by increasing compensation to minimize the impact of these error sources.

5.1 Environmental factors

All low-and medium-cost MEMS gyroscopes exhibit some zero time zero bias and scale factor errors, as well as some variation with temperature. As a result, users usually temperature compensate them. In general, gyroscopes contain integrated temperature sensors for this purpose only. The absolute accuracy of the temperature sensor is not important for this task. What is important is the repeatability of the temperature sensor and its tight coupling to the actual gyroscope temperature. Modern gyro temperature sensors almost never meet these requirements.

There are many techniques available for temperature compensation (polynomial curve fitting, piecewise linear approximation, etc.). As long as a sufficient number of temperature points are recorded and sufficient care is taken during calibration, the particular technique used is irrelevant. For example, insufficient hold time at each temperature is a common source of error. However, no matter which technique is used or how much care is taken, the limiting factor will be temperature lag – the difference in output through cooling and heating near a particular temperature.

This error can be ignored if the application allows either a reset of zero bias at on-off (that is, on-off occurs without rotation) or a field return to zero with zero bias. Otherwise, this may be a bias stability performance limiter because there is no control over shipping or storage conditions.

5.2 Vibration factor

Ideally, a gyroscope can only measure the rate of rotation and nothing else. In practice, all gyroscopes have some sensitivity to acceleration due to asymmetrical mechanical design and/or imprecise micromachining. In fact, acceleration sensitivity comes in many forms, and its severity varies by design. The most important is for linear acceleration (or g sensitivity) and vibration correction (or g2 sensitivity). Since most gyroscope applications are devices that move and/or rotate in the Earth’s 1 g gravitational field, sensitivity to acceleration is usually the largest source of error.

Ultra-low cost gyroscopes typically use extremely simple and compact mechanical system designs that are not optimized for vibration suppression (instead, they are optimized for low cost) and can be greatly affected by vibration. g sensitivity of over 1000°/h/g (or 0.3°/s/g) or higher is not unheard of – more than 10 times worse than one would expect from a high performance gyroscope! There is no point in looking for good bias stability in such a gyroscope, because small rotation of the gyroscope through the Earth’s gravitational field leads to large error 2 sensitivity due to g and g. Usually, vibration sensitivity is not specified in these types of gyroscopes – assuming it is very large.

Some designers try to use external accelerometers to compensate for g sensitivity (this is most often done in IMU applications because the necessary accelerometers already exist), which can indeed improve performance in some cases. However, g sensitivity compensation is not entirely successful for a number of reasons. Most gyroscopes tend to have a g sensitivity, which varies with vibration frequency. Figure 2 shows the response of the silicon sensing gyroscope due to vibration. Note that while the gyroscope’s g sensitivity is within its rated specification (except for some small spurities at specific frequencies, which may not be significant), it does vary in the 12:1 ratio range from DC to 100 Hz, so calibration cannot be accomplished by simply measuring the g sensitivity at DC. In fact, the compensation scheme will be very complex, requiring sensitivity that varies with frequency.

Another difficulty lies in matching the phase response of the compensating accelerometer to that of the gyroscope. If the phase response of the gyroscope and the compensating accelerometer do not match, the high-frequency vibration error may actually be amplified! Another conclusion is drawn: g sensitivity compensation is only suitable for low frequencies of most gyroscopes.

Vibration correction is usually not specified. Sometimes this is because it is embarrassingly poor or varies from device to device. Sometimes this is simply due to the gyroscope manufacturer’s unwillingness to test or specify it (which, to be fair, can be difficult to test). Either way, vibration correction should be of concern because it cannot be compensated with an accelerometer. Unlike the accelerometer response, the gyro output error is corrected.

5.3 A new selection method-vibration sensitivity

Since bias stability is one of the smaller components of the error budget, it is more sensible to select a gyroscope based on its minimization of the maximum error source – in most applications, this would be vibration sensitivity. However, there are times when you may still want lower noise or better bias stability than your chosen gyroscope. Fortunately, there is a solution: average.

Unlike design-driven environmental or vibration errors, the bias stabilization errors of most gyroscopes have noise characteristics. That is, devices are not correlated with each other. Therefore, the bias stability performance can be improved by averaging multiple devices. For every average n devices, you can expect an improvement of √n. Wideband noise can be similarly improved by averaging multiple gyroscopes.

While bias stability has long been considered the “gold standard” specification for gyroscopes, in the real world, vibration sensitivity is often the more serious performance limitation. It is wise to select a gyroscope based on its vibration suppression ability, as other parameters can be easily enhanced by calibrating or averaging multiple sensors.

MEMS definition
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MEMS is the abbreviation of English Micro Electro Mechanical systems, that is, microelectromechanical systems. Microelectromechanical systems (MEMS) technology is a 21st century cutting-edge technology based on micro/nanotechnology, which refers to the design, processing, manufacturing, measurement and control of micron/nanomaterials. It can integrate mechanical components, optical systems, drive components and electronic control systems into a micro-system. This kind of microelectromechanical system can not only collect, process and send information or instructions, but also act on the acquired information autonomously or according to external instructions. It uses a combination of microelectronics technology and micro-machining technology (including silicon body micro-machining, silicon surface micro-machining, LIGA and wafer bonding technology) to produce a variety of excellent performance, low-cost, miniaturized sensors, actuators, drivers and Microsystems. Microelectromechanical system (MEMS) is a new multi-disciplinary technology developed in recent years, which will have a revolutionary impact on human life in the future. It involves many disciplines such as machinery, electronics, chemistry, physics, optics, biology and materials.
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Definition of gyroscope

The gyroscope is an angular motion detection device using the moment-sensitive shell of a high-speed rotating body relative inertia space around one or two axes orthogonal to the rotating axis. The angular motion detection device made of other principles is also called a gyroscope with the same function.

The gyroscope can sense the rotation angular speed of one or more axes, and can accurately sense the complex movement in free space, so the gyroscope has become a necessary motion sensor to track the movement orientation and rotation of the object. Unlike accelerometers and electronic compasses, gyroscopes do not require any external force, such as gravity or magnetic fields, to perform their functions autonomously. Therefore, in theory, only gyroscope can complete the task of attitude navigation.

The characteristic of the gyroscope is that the high frequency characteristic is good, and the high-speed rotating motion can be measured. The disadvantage is that there is zero drift and it is easy to be affected by temperature/acceleration.

MEMS gyroscope definition

MEMS gyroscope is a micro mechanical angular velocity sensor realized by micro-electro-mechanical system (MEMS) technology. It is a fast, accurate and compact sensor that can be used to measure and sense changes in angular acceleration and angular velocity.

Ericco’s MEMS gyroscopes are divided into single axis, double axis, and triple axis according to the number of axes. It is divided into industrial class, tactical class (ER-MG-056, ER-MG-067) and navigation class (ER-MG2-50/100, ER-MG2-300/400). The tactical ER-MG-056 Economical MEMS Gyroscope, ER-MG-067 High Performance MEMS Gyroscope, navigation grade ER-MG2-50/100 High Performance North Seeking MEMS Gyroscope and ER-MG2-300/400 High Precision Navigation MEMS Gyroscope is our best-selling products.

Working principle of micromechanical gyroscope

The basic principle of MEMS gyroscope is to use Nanco crystal gyro (MEMS chip) in MEMS system to detect, measure and interpret changes in angular acceleration and angular velocity. The characteristics of the MEMS crystal gyro used will be oscillated by changes in external angular velocity. The rotor of nanocrystal gyro involved in MEMS gyro will mechanically vibrate according to the external angular acceleration and angular velocity changes.

Important parameters of micromachined gyroscope

The important parameters of MEMS gyroscope include: Resolution, zero angular velocity output (zero output), Sensitivity and measurement range. The ER-MG2-300/400 is a navigation-grade MEMS gyroscope sensor with a measurement range of 400 °/s and deviation instability of 0.01°/ hour, designed for high performance IMU /AHRS/ GNSS auxiliary INS. Designed for accurate attitude and bearing measurement, positioning, navigation and guidance in aerial/Marine/land mapping/surveying systems/UAVS/AUVs and navigation-grade MEMS weapon systems.

ER-MG2-50/100 is a high performance MEMS gyro sensor with 0.01-0.02°/hr bias instability and 0.0025-0.005°/√hr Angle random walk, designed for logging tools/gyro tools, mining/drilling equipment, weapons/UAV launch systems, satellite antennas, etc. The target tracking system is designed for north finding, pointing, and initial alignment.

The resolution is the minimum angular velocity that the gyroscope can detect, and this parameter and the zero angular velocity output are actually determined by the gyroscope’s white noise. These three parameters mainly explain the internal performance and anti-interference ability of the gyroscope. For the user, the sensitivity has more practical selection significance. The measuring range refers to the maximum angular velocity that the gyroscope can measure. Different applications have different requirements for various performance indicators of gyroscopes.

The ER-MG-056 is a low-cost tactical MEMS gyroscope with an instability deviation of 1 °/hr and an angular random walk of 0.25°/√h. It is a single-axis MEMS angular rate sensor (gyroscope) capable of measuring angular velocity up to ±400°/s with a digital output compliant with the SPI slave Mode 3 protocol. Angular rate data is expressed as 24-bit words.

The ER-MG-067 is a high-precision tactical grade MEMS gyroscope with an instability deviation of 0.3 °/hr and an angular random walk of 0.125°/√h. It is a single-axis MEMS angular rate sensor (gyroscope) capable of measuring angular velocity up to ±400°/s with a digital output compliant with the SPI slave Mode 3 protocol. Angular rate data is expressed as 24-bit words.

These parameters are important indicators to judge the performance of MEMS gyroscopes, and also determine the application environment of gyroscopes.
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INS, full name of Inertial Navigation System, is also referred to as inertial navigation system and sometimes referred to as inertial navigation system. Inertial navigation system is a system which uses gyroscope and accelerometer mounted on the carrier to determine the position of the carrier. Through the measurement data of gyroscope and accelerometer, the motion of the carrier in the inertial reference coordinate system can be determined, and the position of the carrier in the inertial reference coordinate system can be calculated.

Unlike other types of navigation systems, inertial navigation systems are completely autonomous in that they neither transmit nor receive signals from outside. The inertial navigation system must know exactly where the vehicle is at the start of navigation, and the inertial measurements are used to estimate the change in position after starting.

An inertial navigation system contains three accelerometers, each of which is sensitive to acceleration in one direction, usually perpendicular to each other. In order to navigate with reference to the inertial reference coordinate system, the direction of the accelerometer must be tracked. The gyroscope can be used to detect the rotational motion of the carrier with respect to the inertial reference coordinate system, so that the direction of the accelerometer at all times can be determined. With this information, we can decompose the acceleration into the reference coordinate system and integrate it.

Inertial system is an autonomous dead reckoning navigation system which uses inertial sensor, reference direction and initial position information to determine the bearing, position and speed of the carrier. It shall at least consist of an inertial measurement device, a digital computer, a control display device and a dedicated precision power supply. The motion of the carrier is carried out in three dimensional space. Its motion forms are linear motion and angular motion. Both linear motion and angular motion are three-dimensional space. To build a three-dimensional coordinate system, it is necessary to build a triaxial inertial platform. The three axis inertial platform can provide a reference for measuring the linear acceleration of three degrees of freedom. The three linear acceleration components of the known azimuths are measured, and the moving speed and position of the carrier are calculated by computer. Therefore, the first type of inertial navigation system scheme is the platform inertial navigation system. There is no “electromechanical” platform, the inertial component gyroscope and accelerometer are directly installed on the carrier, and a “mathematical” platform is established in the computer. Through complex calculation and transformation, the speed and position of the carrier can be obtained. This electromechanical platform inertial navigation system is the second category of inertial navigation system scheme, which is called strapdown inertial navigation system. According to the different use of core sensors, INS can also be divided into RLG INS, FOG INS, DTG INS and MEMS INS.

The Advantages

The inertial navigation system has the following advantages:

1.Because inertial navigation system is independent of any external information and an autonomous system that not radiates energy from the outside.Therefore, it has good concealment and is not affected by external electromagnetic interference;

2.Inertial navigation system can work all day long  in the sky, on the earth surface and even under water.

3.Inertial navigation system can provide location, speed, azimuth and attitude Angle data, and the resulting navigation information is continuous and low noise.

4.High data update rate, short-term accuracy and good stability.

The Disadvantages

1.Due to the integration navigation system, the positioning error increases with time, and the long-term accuracy is poor;

2.Long initial alignment time is required before each use;

3.The equipment is more expensive;

4.Time information cannot be given.

China’s inertial navigation technology has made great progress in recent years. The liquid floating gyro platform inertial navigation system and the dynamic tuned gyro four-axis platform system have been applied to the Long March series carrier rockets successively. Other miniaturized strapdown inertial navigation system, fiber optic gyroscope inertial navigation system, laser gyroscope inertial navigation system and inertial navigation system matching GPS correction have also been widely used in tactical guidance weapons, aircraft, ships, carrier rockets, spacecraft and so on. For example, the test flight of the new laser gyro strapdown system with drift rate of 0.01°~0.02°/h on the new fighter aircraft, the application of the fiber optic gyro and strapdown inertial navigation system with drift rate below 0.05°/h on ships and submarines, and the application of the miniaturized flexible strapdown inertial navigation system on various missile guidance weapons have greatly improved the performance of our military equipment.
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