Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
1998-08-11
2001-02-27
Sheikh, Ayaz (Department: 2155)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S245000, C708S420000, C708S518000, 36
Reexamination Certificate
active
06195596
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a motion effector for use in a virtual reality system; and, more particularly, to a motion effector controller capable of reducing a time gap between an input and an output and also eliminating the harmful effects caused by external disturbances and modeling errors.
BACKGROUND OF THE INVENTION
An effector is a kind of hardware that allows a user to experience a virtual reality, i.e., a device that stimulates human senses to create a feeling of presence in a virtual world. That is, a motion effector or a motion simulator allows a user, sitting on an entertainment chair fixed but moving in synchronism with varying scenes projected on a full-sighted screen, to feel real while he or she, watching the screen, is stirring, shifting or rotating the entertainment chair.
Such movement of the entertainment chair may be driven by a hydraulic mechanism which works under the control of a motion effector controller.
A schematic diagram of a conventional motion effector
100
is given in FIG.
1
and details of the plant
140
shown in
FIG. 1
are shown in FIG.
2
.
The conventional motion effector
100
comprises: a reference provider
110
, a subtractor
120
, a PID (proportional integral derivative) controller
130
and a plant
140
.
The reference provider
110
serves to feed a reference input R(t) which is an electrical signal reflecting a desired movement of the entertainment chair. The subtractor
120
produces an error signal E(t) by subtracting an output signal Y(t) from the reference input R(t). As a controller or compensator, the PID controller
130
manipulates the error signal E(t) so as to produce a control signal U(t). The plant
140
has a moving part therein including the entertainment chair; and is the target of the control by the motion effector controller.
FIG. 2
illustrates details of the plant
140
shown in FIG.
1
. The plant
140
includes: a first AMP (amplifier)
141
, a hydraulic mechanism
142
used as an actuator, a motion simulator
143
, a sensor
144
and a second AMP
145
.
The first AMP
141
magnifies the intensity of the control signal U(t) to a proper level to be used to control the hydraulic mechanism
142
. The hydraulic mechanism
142
has therein hydraulic pumps, valves and a reservoir (which are not shown) for use in driving the motion simulator
143
. The motion simulator
143
, presented as the entertainment chair herein, is made to move according to the operation of the hydraulic mechanism
142
. The sensor
144
detects the movement of the motion simulator
143
to generate an electrical signal reflecting the detected movement of the motion simulator
143
. The electrical signal is finally used in the feedback as illustrated in
FIG. 1
after being amplified at the second AMP
145
.
The operation of the conventional motion effector
100
will now be described.
The error signal reflecting the difference between the reference input R(t) representing the motion that the motion simulator
143
is expected to make and the output signal Y(t) fed back from the plant
140
to the subtractor
120
is provided to the PID controller
130
. So as to compensate the error between the reference input R(t) and the output signal Y(t), the error signal E(t) is manipulated at the PID controller
130
and then transformed into the control signal. The control signal produced at the PID controller
130
is a function of the error signal E(t) and represented by:
U
(
t
)
=
K
p
E
(
t
)
+
K
D
ⅆ
E
(
t
)
ⅆ
t
+
K
I
∫
E
(
t
)
ⅆ
t
,
Eq. 1
wherein, K
P
, K
D
and K
I
are a proportional gain, a differential gain and an integral gain, respectively.
The control signal U(t) is applied to the hydraulic mechanism
142
to be used in controlling the hydraulic mechanism
142
after undergoing an amplification at the first AMP
141
. The hydraulic mechanism
142
drives the motion simulator
143
in such a manner that the motion simulator
143
incessantly traces the desired movement represented by the reference input R(t) under the control of the PID controller
130
. The sensor
144
transforms the movement of the motion simulator
143
into an electrical signal. The output signal Y(t) produced as a result of applying the control signal U(t) is used in the subtraction at the subtractor
120
to thereby produce the error signal E(t). Continuous feedbacks enable the PID controller
130
to finally control the movement of the motion simulator
143
to thereby trace the desired movement.
Albeit popular, however, the PID controller
130
has inherent deficiencies to be used in the motion effector: it provides little countermeasure against the time gap between the reference input R(t) and the output signal Y(t), which may lessen the sense of reality of the user; and, further, such factors as external disturbances, modeling errors, sensor noises, etc. cannot be fully considered and compensated by using the PID controller
130
.
Accordingly, there has existed a need to develop a controller capable of provicing a higher degree of sense of reality to the user.
SUMMARY OF THE INVENTION
It is, therefore, a primary object of the present invention to provide a motion effector controller capable of reducing a time gap between an input and an output and also eliminating harmful effects caused by external disturbances, modeling errors and the like.
In accordance with the present invention, there is provided a motion effector for use in a virtual reality system, comprising: a plant for producing an output signal reflecting the actual movement of a moving part therein; means for providing a reference input signal which reflects a desired motion of the plant; subtracting means for producing an error signal by subtracting the output signal from the reference input signal; first compensating means for generating a first control signal by using the error signal; second compensating means for generating a second control signal by using the reference input signal; and adding means for generating a final control signal by adding the first and the second control signals and providing the final control signal to the plant, wherein the final control signal is used to control the plant.
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patent: 5768122 (1998-06-01), Motoc
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Backer Firmin
Daewoo Electronics Co. Ltd.
Pennie & Edmonds LLP
Sheikh Ayaz
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