Aerospace and Electronic Systems Magazine July 2017 - 32

Reaction Control Thruster Configurations for a Three-Axis Attitude Control System
Table 7.

Dynamic Analysis Results of the Different Configurations
Tracking Error (deg)
Roll

Conf. No.

Pitch

Yaw

Three Axis

Mean

2**

Mean

2

Mean

2

Mean

2

Conf. 1

0.052

0.107

0.018

0.038

0.377

1.093

0.389

1.090

Conf. 2

0.025

0.055

0.014

0.033

0.043

0.099

0.056

0.105

Conf. 3

0.020

0.045

0.018

0.044

0.041

0.093

0.054

0.098

Conf. 4

0.032

0.080

0.039

0.083

0.045

0.110

0.076

0.138

Conf. 5

0.028

0.062

0.061

0.152

0.031

0.074

0.083

0.160

Conf. 6

0.026

0.064

0.020

0.049

0.043

0.104

0.060

0.116

Conf. 7

0.021

0.048

0.016

0.035

0.045

0.109

0.057

0.113

Conf. 8

0.022

0.052

0.025

0.061

0.038

0.091

0.057

0.104

Conf. 9

0.070

0.173

0.048

0.117

0.184

0.474

0.220

0.484

Conf. 10

0.027

0.069

0.022

0.051

0.028

0.067

0.051

0.093

Conf. 11

0.017

0.040

0.017

0.038

0.068

0.186

0.077

0.187

Conf. 12

0.021

0.046

0.015

0.033

0.066

0.178

0.076

0.178

Conf. 13

0.023

0.052

0.021

0.065

0.027

0.062

0.047

0.091

Conf. 14

0.019

0.043

0.016

0.036

0.034

0.076

0.046

0.082

Conf., configuration; Cons., consumption.
* 68% of total data.
** 95% of total data.
*** 99.7% of total data.

As can be seen from Table 6, different configurations are primarily evaluated w.r.t. fuel consumption. The fuel consumption
criterion is the summation of each thruster's fuel consumption for
the points on the sphere surface according to (10). From the fuel
consumption aspect, configuration 13 has the best performance;
see Table 6. The table implies that configurations 12 and 14, and
in the next rank configurations 10 and 7, are the next good ones.
Although configurations 12 and 14 have a different number of
thrusters, they have similar fuel consumption performance. However, configuration 1 has the worst performance from the aspect of
fuel consumption. It can be calculated that the best configuration
compared to the worst configuration has 550% less fuel consumption. The information regarding the maximum and minimum C.C.
shows which configuration in which direction has the best and
worst fuel consumption performance, respectively, which may be
informative for a specific path.

DYNAMIC BEHAVIOR ANALYSIS
To obtain a better understanding of closed-loop attitude control
system performance, dynamic simulations are carried out, because
32

many design parameters may appear in closed-loop simulations.
For this purpose, characteristics such as three-axis tracking error, number and width of modulator pulses, linear displacement,
and fuel consumption are assessed in Table 7 in association with a
given reference.
Based upon the attitude performance in Figure 5, it can be
clearly seen that full three-axis attitude control requirements are
met in all cases, even in the presence of a large initial error. All
performances show that the roll, pitch, and yaw attitudes are stable
and track the command signals accurately from the initial large
attitude errors after about 30 s. For the given mission, Table 7 is
arranged in terms of tracking error, the average number of pulses
per thruster, the average of pulse widths, linear displacement, and
fuel consumption. Regarding the information presented in Table
7, configuration 10 has the best performance from the aspect of
fuel consumption, while configurations 13, 7, and 14 in turn follow
configuration 10. The worst performance corresponds to configurations 1 and 9.
As can be seen, configurations with 16 thrusters have a bit
better performance from the aspect of three-axis tracking accuracy overall. Configurations 13 and 14 have a three-axis accuracy

IEEE A&E SYSTEMS MAGAZINE

JULY 2017

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