Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Aeronautical vehicle
Reexamination Certificate
2000-03-28
2003-06-03
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Aeronautical vehicle
C701S003000, C701S004000, C701S008000, C701S027000, C244S158700, C244S164000
Reexamination Certificate
active
06574534
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a 6-degree-of-freedom control apparatus for controlling three position axes and three attitude axes, i.e., a total of 6 degrees of freedom of a spacecraft such as an artificial satellite.
Conventionally, to dock a spacecraft such as an artificial satellite and another spacecraft, put them into orbit, and maintain a predetermined orbital position, a 6-degree-of-freedom control apparatus controls three position axes and three attitude axes of the spacecraft.
FIG. 4
shows a conventional 6-degree-of-freedom control apparatus disclosed in Japanese Patent Laid-Open No. 7-33095 (reference 1).
Referring to
FIG. 4
, the 6-degree-of-freedom control apparatus comprises a spacecraft main body
101
, a position detector
102
for measuring the position of the spacecraft main body
101
, a target position value generation section
103
for outputting the target position value of the spacecraft main body
101
, a position control calculation section
104
for calculating a control signal associated with position control of the spacecraft main body
101
, an attitude detector
105
for measuring the attitude of the spacecraft main body
101
, a target attitude value generation section
106
for outputting the target attitude value of the spacecraft main body
101
, an attitude control calculation section
107
for calculating a control signal associated with attitude control of the spacecraft main body
101
, a noninterference calculation section
108
for eliminating interference on the dynamics on the basis of the calculation results from the position control calculation section
104
and attitude control calculation section
107
, and a feedforward calculation section
109
for compensating the acceleration components of the target position and attitude values and the inertial force on the dynamics.
The spacecraft main body
101
comprises a thruster selection section
116
for selecting a combination of thrusters and thruster jet pattern on the basis of an input control signal, a thruster modulator
117
including a thruster driving circuit, a plurality of thrusters
118
, and a spacecraft dynamics
119
that changes depending on the thrusts generated by the thrusters
118
.
In the 6-degree-of-freedom control apparatus for a spacecraft shown in
FIG. 4
, the position and attitude of the spacecraft main body
101
are detected by the position detector
102
and attitude detector
105
, respectively. The position control calculation section
104
calculates a control signal associated with position control of the spacecraft main body
101
on the basis of the deviation between the output from the position detector
102
and the target position value output from the target position value generation section
103
. The attitude control calculation section
107
calculates a control signal associated with attitude control of the spacecraft main body
101
on the basis of the deviation between the output from the attitude detector
105
and the target attitude value output from the target attitude value generation section
106
.
The feedforward calculation section
109
calculates a compensation amount for the acceleration components of the target values on the basis of the outputs from the target position value generation section
103
and target attitude value generation section
106
. The feedforward calculation section
109
also calculates the compensation amount for the inertial force on the basis of the outputs from the position detector
102
and attitude detector
105
. The noninterference calculation section
108
eliminates interference on the dynamics between the control signal output from the position control calculation section
104
and that output from the attitude control calculation section
107
. The output from the noninterference calculation section
108
is added to the output from the feedforward calculation section
109
and then output to the thruster selection section
116
mounted in the spacecraft main body
101
.
On the basis of the input control signal, the thruster selection section
116
selects a combination of the thrusters
118
and jet pattern simultaneously for a plurality of axes such that the fuel consumption becomes minimum. The thruster modulator
117
actuates the valves of the selected thrusters
118
of the plurality of thrusters
118
to supply fuel in accordance with the thruster control signal output from the thruster selection section
116
. With this operation, the thrusters
118
selectively jet, and the position and attitude of the spacecraft main body
101
are freely controlled.
The thruster selection section
116
selects the combination of the thrusters
118
and jet pattern on the basis of a lookup table and realizes an efficient thruster control method capable of minimizing the total fuel jet amount using the offset jet logic or permutation jet logic. The offset jet logic removes an offset jet pattern that nullifies the resultant force and torque by jet of the selected thrusters
118
. The permutation jet logic replaces a thruster jet combination with a combination that minimizes the total jet amount, though the resultant force and torque are generated by the selected thrusters
118
.
However, in the 6-degree-of-freedom control apparatus shown in
FIG. 4
, since the thruster selection section
116
distributes the jet to the plurality of thrusters
118
used for axial control in accordance with the control signal generated on the basis of the position and attitude deviations of the spacecraft main body
101
, the thrusters
118
need always be switched. However, the individual thrusters
118
mounted on the spacecraft have a large variation in their output characteristics. Additionally, the variation is random.
Hence, in switching the thrusters
118
used for axial control, it is difficult to accurately grasp the influence of the variation in output characteristics between the individual thrusters
118
on the accuracy of axial control. For this reason, it is hard to accurately control the position and attitude of the spacecraft main body
101
.
In the 6-degree-of-freedom control apparatus shown in
FIG. 4
, after all control signals associated with the axes are added, the thruster selection section
116
selects thrusters to be used, and the thruster modulator
117
executes jet modulation in units of thrusters. The thruster selection section
116
optimizes the thrusters to be used in accordance with, e.g., the required thruster jet amount, independently of the state of the spacecraft main body
101
. For this reason, the relationship between thruster jet and the axial motion of the spacecraft main body
101
is unclear, and the force generated by thrust jet can hardly be decomposed in units of axes.
Modulation executed by the thruster modulator
117
substantially corresponds to the axial motion of the spacecraft main body
101
. In the arrangement shown in
FIG. 4
wherein thruster jet and the motion of the spacecraft main body
101
cannot be associated with each other, the modulation logic to be executed by the thruster modulator
117
cannot be set in advance.
In the 6-degree-of-freedom control apparatus shown in
FIG. 4
, information associated with the velocity/angular velocity of the spacecraft main body
101
is not used for axial control. Hence, for position and attitude control of the spacecraft main body
101
, phase lead compensation cannot be achieved, resulting in limited control performance.
In a thruster control method disclosed in Japanese Patent Laid-Open No. 62-59200 (reference 2), for simultaneous control of a plurality of axes, 6-degree-of-freedom control of a spacecraft is realized by simply adding control logic components for individual axes.
However, since the logic components for axial control are only simply added, fuel consumption of thrusters cannot be suppressed.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a 6-degree-of-freedom control apparatus for a spacecraft, which can simultaneously realize accurate positio
Broadhead Brian J.
Dickstein Shapiro Morin & Oshinsky LLP.
Louis-Jacques Jacques H.
NEC Corporation
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