10 Thruster Rotation Angle Control During Contactless Removal …
131
Here, the projections of the relative EPS thrust are the ratio of the sum of
projections of the EPT thrusts to the thrust of a single thruster P E in the form of
Eq. 10.2.
p i = (P i S1 + P i S2 )P
−1
E
(10.2)
Equation 10.1 serves as the basis for determining the EPT rotation angles
providing the required values of the thrust projections onto the axes of the associated coordinate system. Note that the number of unrestricted variables in these
equations is by one more than equations.
Of the possible variants of the thruster rotation angles with respect to axis OZ S ,
we exclude the case when the plumes of the operating thrusters are directed toward
each other. Variants of the EPT rotation angles with respect to axis OX S make it
possible to control the sign of the momentum relative to axis OY S . This should be
taken into account in the EPT rotation control algorithm during the accumulation of
the total momentum relative to axis OY S for unloading the flywheels.
10.3.2 The Thruster Rotation Control Algorithm
The following algorithm for determining the EPT rotation angles is proposed.
Step 1. Using the algorithms for lateral motion control and longitudinal thrust
component control, the required values of the relative thrust projections
of two EPT on the axes of the SSC-associated coordinate system are
determined.
Step 2. Using Eq. 10.1, the maximum and minimum acceptable values of the EPS
thrust projection onto the longitudinal axis OY S are determined taking into
account the implementation of lateral control as well as the sign of the
total momentum relative to the axis OY S . If the required value of the thrust
projection onto the longitudinal axis exceeds the permissible range, the
control corresponding to such boundary values is implemented.
Step 3. If the required value of the thrust projection onto the longitudinal axis is
within the acceptable range, then the control is provided as follows.
Step 3.1. The EPT rotation angles relative to the axis OX S are taken equal
to each other and equal to the values corresponding to the required
values of the thrust projection on the axis OZ S . The EPT rotation
angles with respect to the axis OZ S are calculated on the basis
of Eq. 10.1 taking into account the required values of the EPS
thrust projection onto the axes OX S and OY S .
Step 3.2. If one of the calculated thruster rotation angles with respect to
axis OZ S exceeds the permissible deflection value, then for the
wider calculated rotation angle in terms of its absolute value,
the rotation angle value is assumed as the maximum permissible
131
Here, the projections of the relative EPS thrust are the ratio of the sum of
projections of the EPT thrusts to the thrust of a single thruster P E in the form of
Eq. 10.2.
p i = (P i S1 + P i S2 )P
−1
E
(10.2)
Equation 10.1 serves as the basis for determining the EPT rotation angles
providing the required values of the thrust projections onto the axes of the associated coordinate system. Note that the number of unrestricted variables in these
equations is by one more than equations.
Of the possible variants of the thruster rotation angles with respect to axis OZ S ,
we exclude the case when the plumes of the operating thrusters are directed toward
each other. Variants of the EPT rotation angles with respect to axis OX S make it
possible to control the sign of the momentum relative to axis OY S . This should be
taken into account in the EPT rotation control algorithm during the accumulation of
the total momentum relative to axis OY S for unloading the flywheels.
10.3.2 The Thruster Rotation Control Algorithm
The following algorithm for determining the EPT rotation angles is proposed.
Step 1. Using the algorithms for lateral motion control and longitudinal thrust
component control, the required values of the relative thrust projections
of two EPT on the axes of the SSC-associated coordinate system are
determined.
Step 2. Using Eq. 10.1, the maximum and minimum acceptable values of the EPS
thrust projection onto the longitudinal axis OY S are determined taking into
account the implementation of lateral control as well as the sign of the
total momentum relative to the axis OY S . If the required value of the thrust
projection onto the longitudinal axis exceeds the permissible range, the
control corresponding to such boundary values is implemented.
Step 3. If the required value of the thrust projection onto the longitudinal axis is
within the acceptable range, then the control is provided as follows.
Step 3.1. The EPT rotation angles relative to the axis OX S are taken equal
to each other and equal to the values corresponding to the required
values of the thrust projection on the axis OZ S . The EPT rotation
angles with respect to the axis OZ S are calculated on the basis
of Eq. 10.1 taking into account the required values of the EPS
thrust projection onto the axes OX S and OY S .
Step 3.2. If one of the calculated thruster rotation angles with respect to
axis OZ S exceeds the permissible deflection value, then for the
wider calculated rotation angle in terms of its absolute value,
the rotation angle value is assumed as the maximum permissible