318
9 OBDH Technology of Lunar Lander
9.4.7 Reliable Design of Highly-Integrated and Lightweight
Devices
Because of the requirements of autonomous survivability and lightweight, there were
following difficulties and characteristics when the electronic devices of the lunar
lander were developed. The increase of the function density made higher complexity
of system and raises the level of hardware and software design. The increase in
the degree of integration made the degree of coupling between the functions to
increase too, leading to the possibility of fault diffusion in operation, which made
the reliability of devices more important. The design of electronic devices should
consider following factors: feasibility, thermal characteristic (heat dissipation and
parts temperature), electromagnetic compatibility and constraints of volume and
mass. Because of improvement of system integration and operation speed, heat dissipation and EMC performance became more and more prominent. It was necessary
to integrate the mechanical, electric, thermal and EMC design.
The high-power modules such as power distribution, drive of heating loop control,
and mechanism control drive had been integrated in the SMU and DIU of the
Chang’E-3 lunar lander. The large electric current might interference other weak
signals and high-speed signals in devices. The issue of concentrated heat dissipation in high-power units was particularly prominent. The design of devices involved
cooperation and communication of many specific and manufacturers. The interface
between boards in a device was more complicated. The key point of reliability design
was to solve the issue of anti-interference and fault tolerance under the condition of
unit combination.
1. Fault Tolerance and Redundant Backup Design under Severe Mass Constraint
The on-board computer was the core component of spacecraft OBDH subsystem,
which performed important tasks such as spacecraft control, autonomous management, and information sharing. The success of spacecraft mission depended directly
on normal operation of OBDH subsystem, so the reliability design had always been
the focus. To date, fault-tolerant design was generally applied to improve the reliability of onboard computer. The fault tolerant technology was realized by two
methods: external intervention and autonomy. The autonomous fault tolerance of
onboard computer was to implement fault screening and processing without ground
or manual intervention, so as to ensure continuous operation of onboard computer to
complete the task. The basic technologies included fault detection, screening, switch
processing, and fault recovery. The implementation means included hardware and
software, which is closely related to architecture of onboard computer.
Up to date, fault-tolerant technology had been widely used in Chinese spacecraft
on-board computers. There were memory EDAC error detection and redundant architecture on the single-board or functional circuit level. In the device level, methods
such as dual-system hot backup and double-machine cold backup and three-machine
hot backup were applied, while 1553B bus dual redundancy and etc. were applied in
system-level. The nature was essentially utilization of hardware redundant resources
9 OBDH Technology of Lunar Lander
9.4.7 Reliable Design of Highly-Integrated and Lightweight
Devices
Because of the requirements of autonomous survivability and lightweight, there were
following difficulties and characteristics when the electronic devices of the lunar
lander were developed. The increase of the function density made higher complexity
of system and raises the level of hardware and software design. The increase in
the degree of integration made the degree of coupling between the functions to
increase too, leading to the possibility of fault diffusion in operation, which made
the reliability of devices more important. The design of electronic devices should
consider following factors: feasibility, thermal characteristic (heat dissipation and
parts temperature), electromagnetic compatibility and constraints of volume and
mass. Because of improvement of system integration and operation speed, heat dissipation and EMC performance became more and more prominent. It was necessary
to integrate the mechanical, electric, thermal and EMC design.
The high-power modules such as power distribution, drive of heating loop control,
and mechanism control drive had been integrated in the SMU and DIU of the
Chang’E-3 lunar lander. The large electric current might interference other weak
signals and high-speed signals in devices. The issue of concentrated heat dissipation in high-power units was particularly prominent. The design of devices involved
cooperation and communication of many specific and manufacturers. The interface
between boards in a device was more complicated. The key point of reliability design
was to solve the issue of anti-interference and fault tolerance under the condition of
unit combination.
1. Fault Tolerance and Redundant Backup Design under Severe Mass Constraint
The on-board computer was the core component of spacecraft OBDH subsystem,
which performed important tasks such as spacecraft control, autonomous management, and information sharing. The success of spacecraft mission depended directly
on normal operation of OBDH subsystem, so the reliability design had always been
the focus. To date, fault-tolerant design was generally applied to improve the reliability of onboard computer. The fault tolerant technology was realized by two
methods: external intervention and autonomy. The autonomous fault tolerance of
onboard computer was to implement fault screening and processing without ground
or manual intervention, so as to ensure continuous operation of onboard computer to
complete the task. The basic technologies included fault detection, screening, switch
processing, and fault recovery. The implementation means included hardware and
software, which is closely related to architecture of onboard computer.
Up to date, fault-tolerant technology had been widely used in Chinese spacecraft
on-board computers. There were memory EDAC error detection and redundant architecture on the single-board or functional circuit level. In the device level, methods
such as dual-system hot backup and double-machine cold backup and three-machine
hot backup were applied, while 1553B bus dual redundancy and etc. were applied in
system-level. The nature was essentially utilization of hardware redundant resources