FT70A Three-Axis FOG

 

 

 

• EO Pod
• Flight Control Platform
• Optical/Photography Platform
• Platform Stabilization Device
• SatCom-on-the-Move
• Inertial Measurement Unit
• Lightweight UAV

 

 

The FT70A is a Sagnac-effect inertial angular rate sensor measuring angular velocity along its sensitive axis. Its sensing unit is a fiber coil. A digital closed-loop detection circuit extracts the optical path difference caused by external angular velocity and converts it into a voltage signal for closed-loop feedback and control, achieving signal modulation and demodulation for high-precision detection. The FT70A three-axis integrated FOG consists of an optical sensing unit and signal detection, providing angular increment and temperature data for medium-high precision INS, positioning, and servo stabilization systems.

 

 

Company is a high-tech enterprise with full closed-loop capabilities from fiber winding equipment and coil winding to IMU circuits, software, and test equipment. End-to-end process control improves quality and reduces costs. Operating under ISO9001 with strict processes, it ensures product reliability and consistency. The oil drilling guidance system is a core downhole equipment component, and accurate attitude and azimuth measurement is key to keeping the borehole trajectory on the designed path. The FT70A FOG measures pitch, roll, and azimuth angular rates of the drilling tool during formation drilling, computing tilt and azimuth angles in real time via angular rate integration.

 

 

FT70A Three-Axis FOG Performance Parameters

Parameter	FT70A
Start-up Time(s)	3
Bias(°/h)	≤0.5
Room Temp.(Constant Temp.)Bias Stability(10s avg. ,°/h)	≤0.05
Room Temp.(Constant Temp.)Bias Stability(100s avg. ,°/h)	≤0.015
Variable Temp. Bias Stability(1℃/min ,100s avg. ,°/h)	≤0.03
Bias Repeatability(°/h)	≤0.015
Bias Magnetic Sensitivity(°/h/Gs)	≤0.01
Angle Random Walk(°/h1/2)	≤0.003
Scale Factor Nonlinearity(ppm)	≤10
Scale Factor Asymmetry(ppm)	≤5
Scale Factor Repeatability(ppm)	≤10
Threshold(°/h)	≤0.015
Resolution(°/h)	≤0.015
Bandwidth(Hz)	≥200
Operating Temperature(℃)	-45～+70
Storage Temperature(℃)	-55～+85
Dynamic Range(°/s)	±300
Supply Voltage(V)	+5
Room Temp. Steady-State Power Consumption(W)	≤4
Full-Temp. Steady-State Power Consumption(W)	≤8
Start-up Inrush Current(A)	<2
Dimensions(mm)	70×70×24.8
Weight(g)	＜750

 

 

 

 

This document specifies the requirements and methods for the use and maintenance of the FT70A three-axis Fiber Optic Gyroscope (FOG) (hereinafter referred to as "the product").

 

2 Product Description 2.1 Working Principle, Functions, and Scope of Application

2.1.1 Working Principle

The product is an inertial angular rate sensor based on the optical Sagnac effect, used to measure the angular velocity of a vehicle along the product's sensitive axes. The angular velocity sensing unit is a fiber coil. A digital closed-loop detection circuit extracts the optical path difference between clockwise (CW) and counterclockwise (CCW) propagating light induced by external physical angular velocity in the fiber coil, while converting the optical path difference signal into a voltage signal for closed-loop feedback and control, thereby achieving signal modulation and demodulation for high-precision angular velocity detection.

2.1.2 Functions

The product consists of an optical angular velocity sensing unit and a signal detection unit, providing three-axis angular increment data and internal temperature information.

2.1.3 Scope of Application

The product is primarily applicable to medium-to-high precision inertial navigation systems (INS), positioning and orientation systems, servo stabilization systems, and similar applications.

2.2 Composition

The main components of the product are as follows:

Optical path unit: includes light source, fiber coil, integrated optical phase modulator (IOPM), fiber coupler, and photodetector;

Electronic circuit unit: light source drive circuit, signal detection and control circuit;

FOG structural components.

2.3 Dimensions and Mounting

Sensor head outline dimensions (mm): 70 ± 0.1 × 70 ± 0.1 × 24.8 ± 0.1 (length × width × height);

Sensor head mounting dimensions (mm): 62 ± 0.1 × 62 ± 0.1, 4 mounting holes: Φ4.2; as shown in Figure 1.

The circuit and optical path components are mounted on the customer's platform.

Figure 1 FT70A Sensor Head Outline and Mounting Diagram

 

2.4 Weight

Total product weight: < 750 g (excluding platform).

2.5 Main Performance Parameters

The main performance parameters of the product are detailed in Table 1.

Table 1 Main Performance Parameters

No.	Test Item	Specification
1	Start-up Time (s)	3
2	Bias (°/h)	≤0.5
3	Bias Stability at Room Temperature (constant temp., 10 s smoothing, °/h)	≤0.05
4	Bias Stability at Room Temperature (constant temp., 100 s smoothing, °/h)	≤0.015
5	Bias Stability under Temperature Variation (1 °C/min ramp, 100 s smoothing, °/h)	≤0.03
6	Bias Repeatability (°/h)	≤0.015
7	Bias Magnetic Sensitivity (°/h/Gs)	≤0.01
8	Random Walk Coefficient (°/h½)	≤0.003
9	Scale Factor Nonlinearity (ppm)	≤10
10	Scale Factor Asymmetry (ppm)	≤5
11	Scale Factor Repeatability (ppm)	≤10
12	Threshold (°/h)	≤0.015
13	Resolution (°/h)	≤0.015
14	Bandwidth (Hz)	≥200
15	Operating Temperature (°C)	-45～+70
16	Storage Temperature (°C)	-55～+85
17	Dynamic Range (°/s)	±300
18	Supply Voltage (V)	+5
19	Steady-State Power Consumption at Room Temperature (W)	≤4
20	Steady-State Power Consumption (full temp. range, W)	≤8
21	Start-up Inrush Current (A)	<2

 

2.6 Mechanical and Electrical Interfaces

2.6.1 Power Supply Requirements

The product is powered by a +5 V DC power supply. The power supply requirements are shown in Table 2:

Table 2 FT70A FOG Power Supply Requirements

No.	Item	Requirement
1	Power Supply Accuracy	±5%
2	Power Supply Ripple (Vpp)	≤50mV
3	Supply Current	>2A

 

2.6.2 Electrical Connection Interface

The FOG-side connector model is J30JZLN9ZKCA000. A mating connector (model: J30JZ/XN9TJCAL01) is provided. The pin definitions are given in Table 3.

Table 3 J30JZLN9ZKCA000 FOG Connector and Test Point Definitions

Pin No.	Definition	Remarks
1	+5V	Power Input
2	GND	Power Ground
3	Reserved	--
4	RXD+	FOG Differential Strobe Positive
5	TXD+	FOG RS422 Output Positive
6	+5V	Power Input
7	GND	Power Ground
8	RXD-	FOG Differential Strobe Negative
9	TXD-	FOG RS422 Output Negative

Note: When connecting to or handling the product, ESD protection measures shall be taken in accordance with GJB 1649-1993.

 

2.6.3 Communication Protocol

Communication interface: Both RXD and TXD are RS422/485 differential communication interfaces. RXD is used to receive a differential pulse (or square wave) synchronization strobe signal, and TXD is used for serial data signal output.

Communication protocol: After receiving the falling edge of the strobe signal, the FOG latches the internal angular increment data and begins outputting the gyro data packet via TXD within 1 μs. The baud rate is 460.8 kbps. The data packet contains 23 bytes, each consisting of 1 start bit, 8 data bits, and 1 stop bit, with no parity bit.

The angular increment data represents the accumulated angular displacement of the gyro between two consecutive strobe signals. The average angular velocity over a given time period is obtained by dividing the accumulated angular increment value by the corresponding time interval.

The data packet format is as follows:

Table 4 Gyro Data Packet Format

Byte No.	Content
	99 (Hexadecimal)
	66 (Hexadecimal)
	Status Word, normal value: FF (hexadecimal)
	X-axis Gyro Angular Increment 1, LSB
	X-axis Gyro Angular Increment 2
	X-axis Gyro Angular Increment 3
	X-axis Gyro Angular Increment 4, MSB
	Y-axis Gyro Angular Increment 1, LSB
	Y-axis Gyro Angular Increment 2
	Y-axis Gyro Angular Increment 3
	Y-axis Gyro Angular Increment 4, MSB
	Z-axis Gyro Angular Increment 1, LSB
	Z-axis Gyro Angular Increment 2
	Z-axis Gyro Angular Increment 3
	Z-axis Gyro Angular Increment 4, MSB
	Temperature Data 1, LSB
	Temperature Data 1, MSB
	Temperature Data 2, LSB
	Temperature Data 2, MSB
	Temperature Data 3, LSB
	Temperature Data 3, MSB
	Frame Number, increments by 1 on each transmission, cyclic count
	Checksum, cumulative sum of Byte 3 through Byte 22
Note: Temperature dimension is 16.

 

The status word bit definitions are as follows:

Table 5 Gyro Status Word Data Format

bit7	bit6	bit5	bit4	bit3	bit2	bit1	bit0
Reserved	Z-axis Circuit Control Status	Y-axis Circuit Control Status	X-axis Circuit Control Status	Reserved	Z-axis Optical Path Status	Y-axis Optical Path Status	X-axis Optical Path Status

Where: the "Reserved" bits are always 1;

the "Circuit Control Status" bit set to 1 indicates normal FOG circuit control status; set to 0 indicates an abnormal control status;

the "Optical Path Status" bit set to 1 indicates normal FOG optical path operation; set to 0 indicates an abnormal optical path status.

If during FOG operation either of the above two status bits remains 0, accompanied by abnormal gyro data, the FOG shall be returned for repair.

 

3 Product Installation and Removal

Requirement

The user is responsible for installing and removing the product. During this process, the product must not be subjected to impact, striking, or collision, nor shall any mechanical processing be performed on its external surfaces.

a) The flatness of the mounting surface shall be better than 0.02 mm;

b) During product testing, it is recommended to fully consider the heat dissipation of the product mounting base.

3.2 Post-Installation Inspection

Verify that all mounting screws conform to the mounting hole dimensions and are securely fastened.

4 Operating Procedures

4.1 Pre-Use Inspection

Inspect the product for physical damage such as collision marks.

4.2 Product Usage Instructions

Mount the product on the vehicle and correctly connect the cables in accordance with Table 3;

Establish the data connection per the communication protocol specified in Section 2.6.3.

4.3 Precautions

a) The FOG should not be subjected to frequent power on/off cycling during use, as this may degrade FOG performance and shorten its service life;

b) Before powering on the FOG, inspect the power supply system to ensure that the supply voltage is correct and that no short circuits exist between electrical points of the power supply, or between the FOG housing and any electrical points;

c) If the product exhibits abnormal operation, consult the manufacturer. Unauthorized disassembly and repair are strictly prohibited;

d) The FOG is a precision instrument. Handle with care during use and transportation;

e) Ensure correct connection of product input signal lines, output signal lines, and power supply lines;

f) ESD protection measures shall be taken when handling the product;

g) The ambient magnetic field strength at the product location shall be less than 10 Gauss.

5 Maintenance

Prior to installation on the vehicle, the product shall be powered on at least once every 6 months for a duration of 3600 s. Electrical parameter testing is not required during this power-on period;

After installation on the vehicle, the product shall be powered on at least once per year for a duration of 3600 s. Electrical parameter testing is not required during this power-on period.

6 Transportation and Storage Requirements

6.1 Transportation Precautions

Place the product according to the orientation indicated on the packaging box;

Transportation is permitted by road, rail, air, and water;

Ensure the packaging box is securely fastened to the carrier to prevent movement during transport.

6.2 Storage Conditions, Shelf Life, and Precautions

a) Products placed in packaging boxes shall be stored under standard atmospheric pressure conditions. The storage ambient temperature shall be 25 °C ± 10 °C, relative humidity 30%–50%, and the surrounding magnetic field strength shall be less than 10 Gauss;

b) The product shelf life is 15 years.

7 Unpacking Instructions

Inspect the outer packaging for physical damage such as collision marks;

Verify that the product and all accessories are complete, as detailed in Table 7.

Perform ESD protection procedures when removing the product.

Table 7 Product Delivery Checklist

No.	Item	Quantity
1	FT70A Three-Axis FOG Assembly	1
2	FOG Assembly Packaging Box	1
3	FOG Assembly Test Report	1
4	J30JZ/XN9TJCAL01 Connector	1
5	Certificate of Conformity	1

 

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