9.4 Design Methodology
317
9.4.6 Design of Spacecraft Autonomous Management
The autonomous capability was the one of most unique and effective functions of the
OBDH subsystem. It was based on the fact that the OBDH subsystem serves as a hub
for monitoring and control of spacecraft and had strong data processing capabilities.
Spacecraft autonomous capabilities could not only reduce the cost of spacecraft
operation and improve reliability, but also be extremely important for autonomously
maintaining spacecraft normal operation and autonomously saving spacecraft under
failure conditions, and greatly improve the survivability of spacecraft.
The autonomous capability meant that the spacecraft could monitor and judge the
status of operation and perform data processing independently, automatically record
abnormity and fill in the problem correction report, inform ground station to request
support only when necessary. Many onboard controls were closed-loop processing,
including routine processing and troubleshooting. It could not only reduce the time
of communication with ground station and the labor of ground station to monitor
spacecraft, but also support the lunar lander in a long term of some intermediate
modes between the independent operation mode and the safe mode, in which some
subsystems and devices could be shut down if necessary, so as to maintain survival
of spacecraft and wait for support from ground station.
In the case of failure, autonomous control would firstly detect, diagnose and locate
the fault parts of spacecraft, and then send a series of commands for redundancy
and reconfiguration to switch spacecraft to a safe mode or downgrade operation.
Obviously, the real-time requirements for fault processing were very prominent.
Usually the time that the lunar lander was accessed by ground station is limited, and
it was difficult to completely handle faults by ground station. It was simpler, quicker
and more effective to implement closed-loop by onboard autonomous control than
by ground station.
The OBDH subsystem of the Chang’E-3 lunar lander was the center of information
and management, which was responsible for autonomous management of the lunar
lander. The automatic thermal control of the lunar lander was a typical autonomous
control. The temperature of the controlled components was detected by telemetry
channel. When the set control threshold was reached, the control commands for
switch-on or switch-off of the heater were sent by OBDH subsystem. The autonomous
management of lithium battery pack discharge protection, high-pressure latch valve
self-monitoring control, special temperature control of the orbit control engine, the
electromagnet control of + Y/–Y solar panel mechanism before landing and the
automatic judgment of the directional antenna back to zero, and etc., were different
from traditional spacecraft. The OBDH software was specially designed for the lunar
lander to extend and enhance the capability of autonomous management. In addition,
the OBDH software could also supported to be on-orbit modified in autonomous
management strategy. It could be injected and modify the autonomous management
strategy without stopping other onboard software running. For sophisticated control,
the detected parameters could be calculated according to certain algorithm, and the
sending of commands could also be determined according to judgment of calculation
results.
317
9.4.6 Design of Spacecraft Autonomous Management
The autonomous capability was the one of most unique and effective functions of the
OBDH subsystem. It was based on the fact that the OBDH subsystem serves as a hub
for monitoring and control of spacecraft and had strong data processing capabilities.
Spacecraft autonomous capabilities could not only reduce the cost of spacecraft
operation and improve reliability, but also be extremely important for autonomously
maintaining spacecraft normal operation and autonomously saving spacecraft under
failure conditions, and greatly improve the survivability of spacecraft.
The autonomous capability meant that the spacecraft could monitor and judge the
status of operation and perform data processing independently, automatically record
abnormity and fill in the problem correction report, inform ground station to request
support only when necessary. Many onboard controls were closed-loop processing,
including routine processing and troubleshooting. It could not only reduce the time
of communication with ground station and the labor of ground station to monitor
spacecraft, but also support the lunar lander in a long term of some intermediate
modes between the independent operation mode and the safe mode, in which some
subsystems and devices could be shut down if necessary, so as to maintain survival
of spacecraft and wait for support from ground station.
In the case of failure, autonomous control would firstly detect, diagnose and locate
the fault parts of spacecraft, and then send a series of commands for redundancy
and reconfiguration to switch spacecraft to a safe mode or downgrade operation.
Obviously, the real-time requirements for fault processing were very prominent.
Usually the time that the lunar lander was accessed by ground station is limited, and
it was difficult to completely handle faults by ground station. It was simpler, quicker
and more effective to implement closed-loop by onboard autonomous control than
by ground station.
The OBDH subsystem of the Chang’E-3 lunar lander was the center of information
and management, which was responsible for autonomous management of the lunar
lander. The automatic thermal control of the lunar lander was a typical autonomous
control. The temperature of the controlled components was detected by telemetry
channel. When the set control threshold was reached, the control commands for
switch-on or switch-off of the heater were sent by OBDH subsystem. The autonomous
management of lithium battery pack discharge protection, high-pressure latch valve
self-monitoring control, special temperature control of the orbit control engine, the
electromagnet control of + Y/–Y solar panel mechanism before landing and the
automatic judgment of the directional antenna back to zero, and etc., were different
from traditional spacecraft. The OBDH software was specially designed for the lunar
lander to extend and enhance the capability of autonomous management. In addition,
the OBDH software could also supported to be on-orbit modified in autonomous
management strategy. It could be injected and modify the autonomous management
strategy without stopping other onboard software running. For sophisticated control,
the detected parameters could be calculated according to certain algorithm, and the
sending of commands could also be determined according to judgment of calculation
results.