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Power System
Subsystem Software Investigation Sheet
PLEASE COMPLETE AND RETURN TO THE SOFTWARE TEAM AT THE NEXT
MEETING OR IN AN EMAIL TO hokiesat_software@vt.edu BY 10/23.
Please attach any info necessary.
1.
What subsystem is this and who is the head? (name and e-mail)
Power system, Chris Cantrell [chcantre@vt.edu]
2.
Who should we contact in your subsystem for software needs? (name and email)
David Zhan [xdzhan@vpec.vt.edu]
3.
What has your subsystem completed up to this point?
System block diagram
4.
What kind of interactions or dependencies does your subsystem have with
other subsystems ? Is there any equipment you use that is shared with another
subsystem such that software access/control to the equipment should be
mutually exclusive?
All subsystems are powered by power system. Power system is
controlled by MSDS and computer system. Except computer and I/O
board, nothing is shared with other subsystems.
5.
Describe, in detail, your subsystem’s software needs. We need you to be as
specific as possible.
The software needed by power system are:
(1).
System operation and load management software
The algorithms are defined by Top system requirement.
(2).
Fault analysis and treatment software
Condition-based algorithm
(3).
Battery charge control software
Check battery temperature, current and voltage, at certain
condition switch on or off the shunt transistor.
(4).
Current, voltage and temperature sense software
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(5).
Time-based algorithm. Sample solar string currents, bettery
temperature, battery current and battery voltage 6 times
per second.
Battery box temperature control software ???
When temperature is lower than –20C, turn on the heater.
When temperature is higher than 0C, turn off the heater.
The heater can be designed to be self-controlled. If so, no
software is needed.
TAKE THE FOLLOWING INTO CONSIDERATION FOR THE QUESTIONS
BELOW:
a.) Include any algorithms you have or plan to have. Please note which are completed.
b.) Include sufficient details about any component and its possible software needs.
c.) Please give an estimate of the time required for the satellite to perform your
algorithms, excluding algorithms that take no appreciable time to execute.
d.) For the purpose of this document, please use the following definitions:
satellite state: The satellite will operate in certain “states”. The satellite transitions
between states depending on certain events. The states are mutually exclusive, and certain
algorithms only exist or execute within the context of certain states. There must be welldefined criteria for transitioning to and from states. We have identified the following
example states to date:
1.) Ground mode: This is the mode used while the satellite is on the ground. It
includes debugging features and such.
2.) Safe mode: This mode represents when the satellite is attached to the stack.
Things like hardware checking are performed in this mode.
3.) Transitory mode: This mode marks the transition from safe mode to normal
operating mode. Things like activating hardware components are performed in
this mode.
4.) Operation mode: This mode is the normal operating mode for the satellite.
a.) Normal mode …
b.) Eclipse mode …
c.) Orbit-correcting mode …
d.) And so forth …
time-based algorithm: Any algorithm that runs either continuously or
periodically while the satellite is in a particular state. A time-based algorithm
should be stated along with its execution frequency. For example,
algorithm X should be executed no fewer than five times per second, and
no less than seven times per second. An example of a time-based algorithm might
be an algorithm that monitors battery charge every so often, or an algorithm that
checks the satellite’s position.
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condition-based algorithm: Any algorithm that is not triggered by the system
clock or is not performed repeatedly on a time interval. These algorithms mainly
arise due to events measured/observed in a time-based algorithm. Error handling,
flight correcting, and response to communication signals are examples of
condition-based algorithms. Note that condition-based algorithms may trigger a
change in the satellite's state and may induce some time-based algorithms to
execute in the new state. For example, "During a time-based algorithm, the orbit
is calculated to be slightly wrong. Execute a condition-based algorithm B to
correct this. Algorithm B changes the satellite’s execution state from "normal
mode" to "correct orbit mode", and in doing so, causes time-based algorithm C to
run. Algorithm C simply fires the thruster every so often to correct the orbit."
5.) Please discuss how the different states of the satellite will affect your
algorithms. Which algorithms exist or execute in which sates?
6.) Please discuss any time-based algorithms you may have.
7.) Please discuss any condition-based algorithms you may have.
8.) Please discuss any error-checking routines. (ex: component failure,
data/measurement failure, communications failure)