9.4 Design Methodology
311
the selection of internal and external connectors and etc. Synthetic measures were
taken to meet the requirements of lightweight and miniaturization of OBDH devices.
According to the characteristics and constraints of the lunar lander, through
comprehensive utilization and analysis of spacecraft resources, the integrated design
and management of function and information flow of the probe were conducted.
The centralized management and classification of information were realized, and the
integrated design of the function of electronic devices was realized to the maximum
extent. According to the configuration of probe and the communication requirements
of each part, it was also considered that the cable connection among different modules
and devices could be maximally saved.
For example, the OBDH subsystem devices of the Chang’E-3 lunar lander were
installed in the + Y module and –Y module to manage telemetry and telecommand.
Based on analysis of function requirements, the integrated design of mechanism,
electricity and thermal control, as well as design of hardware and software could
achieve the optimization of resources allocation and the reduction of interface and
hardware resources among subsystems. The traditional OBDH devices (CTU, TCU,
RTU, DMU, DDR) and other subsystem devices (payload bus controller, power
supply distributor, pyro controller, thermal control heater, ± Y solar panel mechanism controller, transfer mechanism controller, directional antenna bi-axis mechanism controller, the camera pointing mechanism controller, –Y cover mechanism
controller and etc.) were integrated into two devices. In the selection of parts, components and materials, the lightweight materials of aluminum magnesium alloy were
applied as the houses of key electronic devices for the first time, and a lot of integrated
devices such as surface attachment chips, FPGA and high-density connector were
used to reduce mass and power effectively. The electromagnetic compatibility and
anti-interference issues of highly integrated devices were solved at the same time,
so as to realize lightweight and miniaturization of the subsystem.
The system was composed of a combination of centralized and distributed architecture. A single device was integrated with several functional modules and connected
by the internal bus, while the devices were connected by a serial data bus.
The OBDH subsystem was composed of a system management unit (including
telecommand demodulation processing, control computer, command unit, telemetry
unit, multiplexing, DDR, + Y power distribution, pyro controller, thermal controller,
+ Y solar panel mechanism controller), and a data interface unit (including computer,
indirect command unit, thermal controller, transfer mechanism controller, –Y solar
panel mechanism controller, camera pointing mechanism controller, –Y hatch cover
mechanism controller, the dual axis mechanism controller, –Y power distribution
unit and etc.), a double redundant serial data bus and the subsystem software. The
architecture diagram of the Chang’E-3 lunar lander OBDH subsystem is shown in
Fig. 9.2.
The System Management Unit (SMU) was the core of OBDH subsystem. Through
the TT&C transponder, it received and performed all direct commands from ground
stations, and implemented the collection of telemetry data and the distribution of
telecommand indirect commands. SMU managed the power distribution of the + Y
module, the center module and the –Z module, pyro devices, scientific payloads, data
311
the selection of internal and external connectors and etc. Synthetic measures were
taken to meet the requirements of lightweight and miniaturization of OBDH devices.
According to the characteristics and constraints of the lunar lander, through
comprehensive utilization and analysis of spacecraft resources, the integrated design
and management of function and information flow of the probe were conducted.
The centralized management and classification of information were realized, and the
integrated design of the function of electronic devices was realized to the maximum
extent. According to the configuration of probe and the communication requirements
of each part, it was also considered that the cable connection among different modules
and devices could be maximally saved.
For example, the OBDH subsystem devices of the Chang’E-3 lunar lander were
installed in the + Y module and –Y module to manage telemetry and telecommand.
Based on analysis of function requirements, the integrated design of mechanism,
electricity and thermal control, as well as design of hardware and software could
achieve the optimization of resources allocation and the reduction of interface and
hardware resources among subsystems. The traditional OBDH devices (CTU, TCU,
RTU, DMU, DDR) and other subsystem devices (payload bus controller, power
supply distributor, pyro controller, thermal control heater, ± Y solar panel mechanism controller, transfer mechanism controller, directional antenna bi-axis mechanism controller, the camera pointing mechanism controller, –Y cover mechanism
controller and etc.) were integrated into two devices. In the selection of parts, components and materials, the lightweight materials of aluminum magnesium alloy were
applied as the houses of key electronic devices for the first time, and a lot of integrated
devices such as surface attachment chips, FPGA and high-density connector were
used to reduce mass and power effectively. The electromagnetic compatibility and
anti-interference issues of highly integrated devices were solved at the same time,
so as to realize lightweight and miniaturization of the subsystem.
The system was composed of a combination of centralized and distributed architecture. A single device was integrated with several functional modules and connected
by the internal bus, while the devices were connected by a serial data bus.
The OBDH subsystem was composed of a system management unit (including
telecommand demodulation processing, control computer, command unit, telemetry
unit, multiplexing, DDR, + Y power distribution, pyro controller, thermal controller,
+ Y solar panel mechanism controller), and a data interface unit (including computer,
indirect command unit, thermal controller, transfer mechanism controller, –Y solar
panel mechanism controller, camera pointing mechanism controller, –Y hatch cover
mechanism controller, the dual axis mechanism controller, –Y power distribution
unit and etc.), a double redundant serial data bus and the subsystem software. The
architecture diagram of the Chang’E-3 lunar lander OBDH subsystem is shown in
Fig. 9.2.
The System Management Unit (SMU) was the core of OBDH subsystem. Through
the TT&C transponder, it received and performed all direct commands from ground
stations, and implemented the collection of telemetry data and the distribution of
telecommand indirect commands. SMU managed the power distribution of the + Y
module, the center module and the –Z module, pyro devices, scientific payloads, data