Key Words
| Allan Variance | Plot of quotient when the integrated value of gyro output is divided by integral time. It shows a cluster time (averaging time) in a horizontal axis and an Allan deviation (σ) in a vertical axis. We can read the random walk, bias stability etc. from the plot and also represent the noise component of gyro in a graph. |
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| Warm Up | Warming up operation after turning on the power |
| Angular Velocity | Change ratio of angle (rotation speed, rotation angle) per unit time |
| Acceleration | Change ratio of speed per unit time. The gravity is a kind of the acceleration. |
| Cross Coupling | Sensitivity against the detection axis by another axis input. Misalignment which indicates direction accuracy is a kind of the cross coupling. |
| CPS/INS Hybrid Navigation System | Compound navigation of GPS and INS (Inertial Navigation System). Technology for high accuracy and stable navigation. The error estimation of inertial sensor by Kalman filter improves the accuracy. |
| Scale Factor | Ratio of sensor output changed by input. It is also called sensitivity (Sensitivity is distinguished from scale in the IEC standard). |
| Sensor Fusion | By compounding data from several sensors, improve the measurement reliability of the unit or complement defects of each sensor. |
| Sensor Data Correction | To correct the error which each sensor has. |
| Dynamic Range | Measurable range of a sensor from minimum to maximum of a motion. The reciprocal of a dynamic range is a scale factor. |
| Dead Reckoning (Autonomous Navigation) |
Technology of position measurement with high accuracy even in a tunnel without GPS signal by the compound arithmetic procession of the information from gyro sensor, accelerometer etc. |
| Drift | Drift is the indication of bias variation size under the influence of environmental condition such as temperature (rise or fall), power supply variation or vibration. There is also a successive change shifting slowly. |
| Bias | Deviation from ideal center. Difference between output in a stationary state and ideal zero. It is also called zero point bias or offset. It becomes an element of the error (integration error) in case of angle calculation. |
| Fiber Optic Gyro | Turn the optical fibers like a coil in CW and CCW and input light to both directions. By the interference of the output, the wavelength is changed due to Doppler effect according to the motion (red and blue shift). A gyroscope which detects and outputs the change amount. |
| MEMS | MEMS is the abbreviation of Micro Electro Mechanical Systems and the general term indicates the technology to build micro mechanical mechanism of nano-level or micron-level by using semiconductor manufacturing equipment. |
| MEMS Gyro | Sensor making use of MEMS technology which detects the acceleration by using inertial force (Coriolis force) coming from vibration or rotation |
| Random Walk | Digitalized value of degree of variation (white noise). It is considered to be the noise which a sensor has. |
| Leveling Calculation | Inertial operating algorithm of MEMS-IMU (IMU consists of MEMS gyros and MEMS accelerometers) made by Tamagawa. It enables a high precision dynamic posture measurement to a low cost (low accuracy) gyro. ※Leveling Calculation vs GNSS/INS/VS |