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Instrument engineering for aerospace vehicles

Strap-down stellar inertial unit (SSIU)

This device is intended for spacecraft Control Systems application. Device functioning is based on strap-down stellar inertial navigation system concept.

Purpose of SSIU:

  • determination of absolute rate vector projections of base on axes of the Instrumental reference frame (RF);
  • determination of attitude quaternion of the Instrumental RF wrt the Inertial (second equatorial) RF;
  • correction of attitude quaternion by stellar measurement system;
  • monitoring of device functioning and issue of the report of device state to Control System on-board computer.

SSIU structure:

  • four fiber-optic gyros (FOG), one of them is in cold standby;
  • main and reserve (in cold standby) special computer;
  • secondary power supplies;
  • commutation unit of primary power supply;
  • cable system.

  • FOG data processing is performed in special computer with tact 5 ms, stellar measurement system measurements are used for inertial data specification with tact 200 ms.

SSIU structural diagram


SSIU performances:

  • angular rate determination error - ± 1,5*10-5 °/s;
  • error of attitude parameters determination with stellar monitoring - ± 15 ";
  • interfaces - RS-422/RS-485;
  • functional readiness time - 3 s;
  • accuracy readiness time - 30 min;
  • life time - 65000 h;
  • power consumption - 12,5 W;
  • temperature range of installation plane - -5+40 °;
  • mass (excluding stellar measurement system) - 5,5 kg;
  • overall dimensions (excluding stellar measurement system) - 210x210x205 mm.

Versatile Navigation Complex


Term versatile means the possibility of versatile navigation complex application in Control Systems of various aerospace vehicles: launch vehicles, small rockets, Unmanned Aerial Vehicles of medium and heavy class, cargo-and-passenger aircrafts.

Versatile Navigation Complex functioning is based on integrated inertial-satellite navigation system concepts.

Purpose of Versatile Navigation Complex:

  • measurement of parameters that characterize objects motion and its attitude in inertial space;
  • inertial navigation parameters correction by data which is received from other data sources;
  • computation of full volume of navigation data which is necessary for Control System operation;
  • performing of initial alignment of inertial measurement unit (IMU);
  • running order monitoring of exchange channels and complex components.

Composition of base case of Versatile Navigation Complex:

  • IMU on the base of three fiber-optic gyros (FOG) and three pendulous accelerometers of medium class accuracy;
  • navigation computer;
  • satellite navigation systems data user equipment (GPS user equipment);
  • secondary power supplies;
  • analog-digital converter (ADC);
  • synchronizing pulses unit;
  • cable system.

  • Inertial measurement unit and navigation computer are developed in common form factor.
    Versatile navigation complex integration with other external systems (radio altimeter, barometric altimeter, air signals system, odometers etc.) is determined by tasks to perform by concrete vehicles.

    Tact of data pickup:
  • from IMU sensors 1,25 ms;
  • from GPS user equipment 1 s.

  • Navigation task integrated with GPS user equipment is computed with tact 5 ms.

Versatile Navigation Complex structural diagram


Versatile Navigation Complex performances:

  • coordinates determination error (3 σ) - < 9 m;
  • velocity determination error (3 σ) - ± 0,1 m/s;
  • rate of attitude parameters drift - ± 0,15 °/h
  • interfaces - RS-422/RS-485;
  • accuracy readiness time - 10 min;
  • warranty period of versatile navigation complex operation as a part of Control System - 12 years;
  • power consumption (excluding GPS user equipment) - 20,5 W;
  • operational temperature range - -40…+55 °;
  • mass (excluding GPS user equipment) - 3,2 kg
  • overall dimensions (excluding GPS user equipment) - 190x190x120 mm.

On-board control complex with navigation unit for small unmanned helicopter


Purpose of on-board control complex:

  • helicopter motion parameters measurement and issue to navigation unit;
  • navigation parameters determination;
  • helicopter attitude determination;
  • helicopter navigation and control during the flight by given program;
  • helicopter control during the flight wrt the program attitude;
  • payload control;
  • data transmission through the radio channel from payload.

On-board control complex composition:

  • three-axis gyro;
  • three-axis accelerometer;
  • absolute pressure sensor;
  • three-axis magnetometer;
  • GPS user equipment.

  • Sensors are developed according to MEMS-technology.

    On-board control complex structural diagram


    On-board control complex performances:

    • coordinates determination error (3 σ) - 25...40 m;
    • attitude determination error (3 σ) - 0,9…1,5 °;
    • velocity determination error (3 σ) - ± 0,6 m/s;
    • accuracy readiness time - 5 min;
    • power consumption - 1,5…2,0 W;
    • operational temperatures range - -40…+55 °;
    • mass - 0,12 kg
    • overall dimensions for non-hermetic case - 77x70,5x30,5 mm

On-board computers (OBC)
OBC provide the implementation of wide range of tasks of spacecraft and launch vehicles Control Systems.

Name OBC for spacecraft Control System OBC for launch-vehicles Control System
OBC-698 OBC-697
Processor type I386EX S698M Sparc-V8 697F
Clock frequency, MHz 50 66/266 100
Operation speed 12 MIPS 33/266 MIPS, 8/64 MFLOPS 90 MIPS, 20 MFLOPS
Digit capacity 8/16/32 8/16/32/64 (FPU) 8/16/32
RAM capacity/digits 0,5 Mb/16 2 Mb/32 8 Mb/32
ROM capacity/digits 2 Mb/16 4 Mb/32 12 Mb/32
Reliability methods redundant structure
(cold reserve)
asynchronous, triple structure with majoritivity and data recovery for the cases of failures, Hamming codes for memory majority processor chip, Hamming codes for memory, redundant bus MIL-STD-1553
Interfaces RS-232,
16-bit parallel bus
RS-422, RS-485, MIL-STD-1553,
16-bit parallel bus
RS-422, MIL-STD-1553
Power consumption, W 6,6 29 14

Navigation computers

  Navigation computers are used in navigation devices and complexes of different control objects.

Name Navigation computer for Versatile Navigation Complex and SSIU On-board computer for automatic control systems of aircrafts of An-148, 158, 178 class
Processor type DSP TMS320C6713B TMS570LS3137
Clock frequency, MHz 200 180
Operation speed 1600/1200 MIPS/MFLOPS 288 MIPS
Digit capacity 8/16/32 8/16/32
RAM capacity/digits 1 Mb/32 256 Kb
ROM capacity/digits 2 Mb/32 3 Mb
Reliability methods a) single-channel structure with control by watch dog timer
b) redundant structure (cold standby)
redundant structure (hot standby),
Hamming codes for memory
Interfaces RS-422, RS-485,
16-bit parallel bus
RS-422, SPI, Ethernet
Power consumption, W 6,6 10