9.4 Design Methodology
319
for backup to achieve different level of fault tolerance according to design of cold
and hot backup, as well as different costs paid.
The high integration of electronic circuits made it possible to change the design
ideas of double redundancy or triple redundancy used in current OBDH system. The
redundancy design could be conducted in device level, board level and chip level
according to the importance of units. Each chip and function unit could be designed
with double redundancy or triple redundancy. The cross reconfiguration of system
could be realized to improve the success of system reconfiguration, so as to greatly
improve reliability of system.
According to analysis of task requirements and system reliability, the SMU
of OBDH subsystem of the Chang’E-3 lunar lander should perform all platform
management, while there were many operation modes and the functional design
was complex. There were internal cold backup and the hot backup circuit simultaneously, and the cross control requirement in internal interface, so the cold and hot cross
backup based on fault isolation was applied in SMU redundancy design. The CTU
and the Data Multiplexer Unit was cold backup. The TCU, the indirect command
unit and the thermal control unit were hot backup. The telemetry acquisition unit was
always online. The drive unit of mechanism control was online only when working,
and circuit-level hot backup of main and backup windings was applied. The interface design between them for cross backup, hot/cold backup was difficult. The drive
control circuit design for cross backup, hot/cold backup between units in the SMU
effectively solved the issue of complex interface reliability between internal cold/
hot backup function units in highly integrated devices, as well as the issue of fault
isolation, anti-sneak path design, and other issues between cold/hot backup units.
The dual-system hot backup design was applied in DIU.
2. Thermal and Electromagnetic Compatibility Design in Highly Integrated Device
Since many functions were integrated in the OBDH devices of Chang’E-3, miniaturization and integration of devices induced issue of significant amounts of heat
in operation. Stringent requirement for thermal design of the device was comp up.
The focus of thermal design was not only on the power components mounted on
structure, but also the cooling effect of critical control circuits to ensure accuracy
of control. In the design, it was necessary not only to apply various thermal design
methods for reducing thermal resistance, but also to effectively combine thermal
simulation work with computer simulation to find overheated parts of each unit and
adopt scientific cooling measures. Thermal analysis based on software simulation
was of great significance to design rational layout of each circuit part and improve
structural design level of devices. It was necessary to combine advanced manufacturing technology to solve heat dissipation of power units, such as the use of ceramic
substrates and metal substrates (including aluminum substrates, copper substrates),
and the use of surface mount devices instead of discrete components to improve heat
dissipation conditions.
319
for backup to achieve different level of fault tolerance according to design of cold
and hot backup, as well as different costs paid.
The high integration of electronic circuits made it possible to change the design
ideas of double redundancy or triple redundancy used in current OBDH system. The
redundancy design could be conducted in device level, board level and chip level
according to the importance of units. Each chip and function unit could be designed
with double redundancy or triple redundancy. The cross reconfiguration of system
could be realized to improve the success of system reconfiguration, so as to greatly
improve reliability of system.
According to analysis of task requirements and system reliability, the SMU
of OBDH subsystem of the Chang’E-3 lunar lander should perform all platform
management, while there were many operation modes and the functional design
was complex. There were internal cold backup and the hot backup circuit simultaneously, and the cross control requirement in internal interface, so the cold and hot cross
backup based on fault isolation was applied in SMU redundancy design. The CTU
and the Data Multiplexer Unit was cold backup. The TCU, the indirect command
unit and the thermal control unit were hot backup. The telemetry acquisition unit was
always online. The drive unit of mechanism control was online only when working,
and circuit-level hot backup of main and backup windings was applied. The interface design between them for cross backup, hot/cold backup was difficult. The drive
control circuit design for cross backup, hot/cold backup between units in the SMU
effectively solved the issue of complex interface reliability between internal cold/
hot backup function units in highly integrated devices, as well as the issue of fault
isolation, anti-sneak path design, and other issues between cold/hot backup units.
The dual-system hot backup design was applied in DIU.
2. Thermal and Electromagnetic Compatibility Design in Highly Integrated Device
Since many functions were integrated in the OBDH devices of Chang’E-3, miniaturization and integration of devices induced issue of significant amounts of heat
in operation. Stringent requirement for thermal design of the device was comp up.
The focus of thermal design was not only on the power components mounted on
structure, but also the cooling effect of critical control circuits to ensure accuracy
of control. In the design, it was necessary not only to apply various thermal design
methods for reducing thermal resistance, but also to effectively combine thermal
simulation work with computer simulation to find overheated parts of each unit and
adopt scientific cooling measures. Thermal analysis based on software simulation
was of great significance to design rational layout of each circuit part and improve
structural design level of devices. It was necessary to combine advanced manufacturing technology to solve heat dissipation of power units, such as the use of ceramic
substrates and metal substrates (including aluminum substrates, copper substrates),
and the use of surface mount devices instead of discrete components to improve heat
dissipation conditions.