Note: Descriptions are shown in the official language in which they were submitted.
SYSTEM FOR CONTROLLING ROTATION OF PROPELLER
VNIT OF Z-TYPE PROPULSION APPARATUS
BACKGRO~ND OF THE INVENTION
Field of the Invention
_
This invention relates to a system for controlling the
rotation of a propeller unit of a Z-type propulsion apparatus
for a watercraft such as a tug boat.
Prior Art
In recent years, harbors have become much crowded with
vessels of a large size. Therefore, it has been required
that tug boats should operate to move the vessel toward and
away from the shore in a safe and rapid manner. For this
reason, there have now been extensively used tug boats
equipped with a Z-type propulsion apparatus which can easily
vary the direction of propulsion over the range of 360
degrees.
There has been proposed a system for controlling the
rotation of a propeller unit of such a Z-type propulsion
apparatus which comprises a steering handle for commanding a
propeller unit to rotate by a desired amount of angle in a
selected direction. The steering handle is provided with a
potentiometer for detecting the angular movement thereof
(steering angle 01). There is provided in the system another
potentiometer for detecting the angular movement of the
propeller unit (follow-up angle 02). And a vector
calculation circuit is provided for outputting a sinusoidal
signal sin(al ~ ~2) to a servo~control circuit, the signal
sin (~1 - 02) representing a sine of the difference of angle
between the steering angle 01 and the follow-up angle 02.
The servo control circuit produces a servo signal from the
sinusoidal signal sin(~ 2) and feeds it to a servomotor
which in turn controls a hydraulic circuit in accordance with
its rotational movement. The hydraulic circuit controls a
hydraulic motor, and the hydraulic motor rotates the
propeller unit via a gear mechanism.
With the construction of the above-described
conventional system however, the propeller unit rotates in
the opposite direction to that of rotation of the steering
handle when the difference of angle (01 - ~2) exceeds 180,
since the sinusoidal signal sin(~ 2), whose polarity is
reversed when the difference of angle (al - a2) exceeds 180,
is directly inputted to the servo control circuit. As shown
in Fig. 2, when the steering handle is operated in such a
manner that the steering angle 01 is abruptly varied from 0
to 180 clockwise, the propeller unit rotates not clockwise
but counterclockwise by the follow-up angle ~2, as indicated
by a broken line in the same figure. As a result, the tug
boat mounting this system turns in the opposite direction,
i.e., counterclockwise. As is described above, the
conventional system has a deficiency that the propeller unit
rotates in the opposite direction when the difference of
angle (01 - ~2) exceeds 180.
SUMMARY O~ TNE INVENTION
It is therefore an object of the present invention to
provide a system for controlling the rotation of a propeller
unit of a Z-type propulsion apparatus in which the propeller
unit can be rotated in the selected direction even when the
propeller unit is commanded to ro~ate by more than 180,
thereby a safe and good steerability being obtained.
It i5 another object of the invention to provide such a
system which is simple in construction and can be
manufactured at lower costs.
According to one aspect of the present invention, there
is provided a system for controlling the rotation of a
propeller unit of a Z-type propulsion apparatus comprising a
steering angle detector for detecting as a steering angle an
angular position of a steering handle for commanding the
propeller unit to rotate; a follow-up angle detector for
detecting as a follow-up angle an angular position of the
propeller unit; a vector calculation circuit responsive to
outputs of the steering angle detector and the follow-up
angle detector for outputting a first sinusoidal signal
representative of a sine of the difference of angle between
the steering angle of the steering handle and the follow-up
angle of the propeller unit, a cosine signal representative
of a cosine of the difference of angle and a second
sinusoidal signal representative of a sine of an angle
obtained by adding +45 to the difference of angle; a signal
processing circuit responsive to the first and second
S
sinusoidal signals and cosine signal for outputting a
positive constant value when the difference of angle, which
varies within -360 and ~360, is grea~er than ~180 and when
the second sinusoidal signal is negative, the signal
processing circuit outputting a negative cons~ant value when
the difference of angle is less than -180 and when the
second sinusoidal signal is negative/ the signal processing
circuit outputting the first sinusoidal signal when the
difference of angle is between -180 and +180 or when the
second sinusoidal signal is greater than or equal to 0; and a
drive unit responsive to output of the signal processing
circuit for rotating the propeller unit.
According to another aspect of the present invention,
there is provided a system for controlling the rotation of a
propeller unit of a Z-type propulsion apparatus comprising: a
steering angle detector for detecting as a steering angle an
angular position of a steering handle for commanding the
propeller unit to rotate; a follow-up angle detector for
detecting as a follow-up angle an angular position of the
propeller unit; a vector calculation circuit responsive to
outputs of the steering angle and follow-up angle detectors
for outputting a sinusoidal signal representative of a sine
of the difference of angle between the steering angle of the
steering handle and the follow-up angle of the propeller unit
and a cosine signal representative of a cosine of the
difference of angle; a signal processing circuit responsive
to the sinusoidal and cosine signals for outputting the
sinusoidal signal when the cosine signal is greater than a
predetermined value, the signal processing circuit outputting
a positive constant value when the difference of angle i5
positive and when the cosine signal is less than the
predetermined value, the signal processing circuit outputting
a negative constant value when the difference of angle is
negative and when the cosine signal is less than the
predetermined value; and drive unit responsive to output of
the signal processing circuit for rotating the propeller
unit. In this system, the signal processing circuit may be
constructed so that it holds and outputs the value of the
sinusoidal signal obtained a~ the moment when the cosine
signal becomes less than the predetermined value if the
cosine signal is less than the predetermined value. And in
this system, the signal processing circuit may further
comprise a circuit for comparing the value of the sinusoiclal
signal held by itself with the sinusoidal signal outputted
from the vector calculation circuit to release the holding of
the value of the sinusoidal signal when the polarity of the
value and the polarity of the sinusoidal signal outputted
from the vector calculation circuit coincide with each other
and when the cosine signal becomes greater than the
predetermined value~ Alternatively, the signal processing
circuit may further comprises a circuit for comparing the
value of the sinusoidal signal held by itself with the
2~ sinusoidal signal outputted from the vector calculation
circuit to release the holding of the value of the sinusoidal
signal when the cosine signal becomes greater than the
predetermined value and when the difference between the value
held by itself and the sinusoidal signal outputted from the
vector calculating circuit is less than a second
predetermined value.
According to a further aspect of the present invention,
there is provided a system in which the signal processing
circuit comprises a counter circuit for performing one of
incremental and decremental counting operations which is
identical to the preceding counting operation each time the
polarity of the cosine signal is changed and when the
polarity of the sinusoidal signal at the time of changing of
the polarity of the cosine signal is different from the
polarity of the sinusoidal signal at the time of the
- preceding changing of the polarity of the cosine signal, the
initial count value of the incremental and decremental
counting operations being 0, the counter circuit performing
one of the incremental and decremental counting operations
which is of the different ~ind from that of the preceding
counting operation each time the polarity of the cosine
signal is changed and ~hen the polarity of the sinusoidal
signal at the time of changing of the polarity of the cosine
signal is identical to the polarity of the sinusoidal signal
at the time of the preceding changing of the polarity of the
cosine signal; and a signal hold circuit for outputting the
sinusoidal signal to the drive unit when the count value
outputted from the counter circuit is 0, the signal hold
circuit holding and outputting the value of the sinusoidal
signal obtained at the moment when the count value becomes
other than 0 if the count value is other than 0.
~21S~S
And in the systems provided in accordance with the
present invention, the steering angle detector and the
follow-up angle detector may comprise potentiometers.
Fig. 1 is a block diagram showing the construction of
the first embodiment of the present invention;
Fig. 2 is an illustration for explaining the
relationship between the steering angle and the follow-up
angle in the conventional system;
Fig. 3 is a diagrammatical illustration of the propeller
housing of the embodiment shown in Fig. l;
Fig. 4 is a circuit diagram showing in detail the
calculation processing circuit of the embodiment shown in
Fig. l;
Fig. 5 is a circuit diagram showing in detail the signal
processing circuit of the embodiment shown in Fig. l;
Fig. 6 is an illustration showing the waveforms for
explaining the operation of the embodiment shown in Fig. l;
Fig. 7 is a block diagram showing the construction of
2G the second embodiment of the invention;
Fig. 8 is an illustration showing the waveforms for
explaining the operation of the embodiment shown in Fig. 7;
Fig. 9 is a block diagram showing the construction of
the third embodiment of the invention;
Fig. 10 is a block diagram showing the construction of
the fourth embodiment of the invention;
~IL2~ S
Fig. 11 is a block diagram showing the construction of
the fifth embodiment of the invention;
Fig. 12 is an illustration showing the waveforms for
explaining the operations of the embodiments shown in Figs. 9
to 11.
DES~RIPTION OF THE PREFERRED EMBODIMENTS
___
Figs. 1, 3 and 5 show a system for controlling the
rotation of a propeller unit of a Z-type propulsion apparatus
according to the present invention. In the figures,
reference numeral 1 denotes a steering handle for commanding
a propeller housing 2 (propeller unit) of a 2-type propulsion
apparatus to rotate, the propeller housing 2 being rotatably
mounted on a hull. The steering handle 1 is connected to an
angular position detector 3 comprising a well-known
potentiometer or the like which outputs a sinusoidal voltage
sin al and a cosine voltage cos 01 in accordance with the
angular position 01 (steering angle) of the steering handle
1. Another angular position detector 4 such as a
potentiometer is connected to a worm shaft 5 through a gear
mechanism, the potentiometer outputting a sinusoidal voltage
sin 02 and a cosine voltage cos 92 (follow-up angle) in
accordance with the angular position 92 of the propeller
housing 2. The output voltages sin ~1 and cos 01 of the
angular position detector 3 and the output voltages sin 02
and cos 92 of the angular position detector 4 are inputted to
the calculation circuit 6 (vector calculation circuit). The
--8~
s
calculation circuit 6 produces a first sinusoidal signal sin
(01 - 02) and a cosine signal cos(~l - 02) of an angle (~1 -
~2) representative of the d.ifference of angle between the
steering angle 01 and the follow-up angle 02, and also
produces a second sinusoidal signal sin ~al - ~2 + 45) of an
angle (01 - H2 ~ 45) which is obtained by adding 45 to the
difference of angle (21 - ~2). These signals sin (~1 - 02),
cos (~ 2) and sin (01 - e2 + 45) are inputted to a
signal processing circuit 7.
As shown in Fig. 4, the calculation circuit 6 comprises
multipliers MULl to MUL4, a subtracter SUBl and adders ADDl
and ADD2. These operational devices may be constituted of
analog circuits including operational amplifiers or of
digital circuits including a microprocessor. The signal
processing circuit 7 is connected to a limiter 8, and this
limiter 8 is connected to a servo control circuit 9 for
controlling a servomotor 10.
The servomotor 10 is connected to a hydraulic pump 11
which is coupled to a hydraulic cylinder 14 through
connecting tubes 12 and 13. The piston 14a of the hydraulic
cylinder 14 is linked to a control lever 15a of a a hydraulic
pump 15 to control the direction and amount of the oil
passing therethrough, the hydraulic pump 15 being connected
to an electric motor 16. The hydraulic pump 15 is coupled
through connecting tubes 17 and 18 to a hydraulic motor 19
which is linked to a worm wheel 21 through a worm 20 formed
on a shaft 5, and the worm wheel 21 is connected to the
propeller housing 2.
The sinusoidal signal sin (01 - 02) inputted to the
signal processing circuit 7 is supplied through a square wave
circuit 22 to a +180 crossover detection circuit 23 and to a
-180 crossover detection circui-t 24, the square wave circuit
22 shaping the waveform of the signals inputted thereto into
square waves. The ~180 crossover detection circuit 23
detects the positive to negative change of the polarity of
the sinusoidal signal sin (01 - 02) when the difference of
angle (01 - 92) becomes 180 while the -180 crossover
detection circuit 23 detects the negative to positive change
of the polarity of the sinusoidal signal sin (01 - 02) when
the difference of angle (al - 02) becomes -180. The
sinusoidal signal sin (~1 - 92) is also supplied through
contacts 25a of a signal switching circuit 25 to the limiter
8 which limits the amplitude of the inputted signal to a
predetermined range. An output terminal of the +180
crossover detection circuit 23 is connected to one input
terminal of an AND circuit 26, while an output texminal of
the -180 crossover detection circuit 24 is connected to one
input terminal of another AND circuit 27. And the cosine
signal cos (~1 - 02) inputted to the signal processing
circuit 7 is supplied through a square wave circuit 28 to a
polarity decision circuit 29 which outputs a H level signal
when the cosine signal cos (al - ~2) is negative. An output
terminal of the polarity decision circuit 29 is connected to
the other input terminal of the AND circuit 26 and to the
other input terminal of the AND circuit 27. An output
terminal of the AND circuit 26 is connected to a SET terminal
--10--
of a flip~flop 30, while an output terminal of the AND
circuit 27 is connected to a SÆT terminal of another flip-
flop 31. The sinusoidal signal sin (~1 - 02 ~ 45) inputted
to the signal processing circuit 7 is supplied through a
square wave circuit 32 to a flip-flop reset circuit 33. This
flip-flop reset circuit 33 is connected to a RESET terminal
of the flip flop 30 and to a RESET terminal of the flip-flop
31. And an output terminal of the flip-flop 30 is connected
to a + input terminal of an operational amplifier 34 and to
one input terminal of an OR circuit 35. An output terminal
of the flip-flop 31 is connected to a - input terminal of the
operational amplifier 34 and to the other input terminal of
the GR circuit 35. An output terminal of the operational
amplifier 34 is connected through contacts 25b of the signal
switching circuit 25 to the input terminal of the limiter 8,
and an output terminal of the OR circuit 35 is connected to
the +180 crossover switching circuit 36. This +180
crossover switching circuit 36 closes the contacts 25b of the
signal switching circuit 25 when a H level signal is inputted
thexeto, and closes the contacts 25a when a L level signal is
inputted thereto.
The operation of this system will now be described with
reference to Fig. 6.
It is assumed that the steering handle l begins to be
pivotally moved when the steering angle 01 of the steering
handle 1 and the follow-up angle ~2 of the propeller housing
2 are equal to each other. In this case, a difference of
angle appears between the steering angle 01 and the follow-up
angle ~2. It is also assumed that the difference of ang1e
(01 - ~2) becomes positive when the steering handle 1 is
pivoted clockwise and that the difference of angle (~1 - 02)
becomes negative when the steering handle 1 is pivoted
counterclockwise. The output signals sin 01 and cos 61 of
the angular position detector 3 and the output signals sin 02
and cos 02 of the angular position detector 4 are inputted to
the calculation circuit 6 which in turn executes a
calculation using these signals to form three kinds of
signals, i.e., the sinusoidal signals sin (01 - Q2) and sin
(el - 02 ~ 45) and the cosine signal cos (91 - ~2) (see Fig.
6). The waveforms of the signals sin (~1 - 02), sin (01 - a2
45) and cos (91 - ~2) outputted from the calculation
circuit 6 are shaped into square waves by the square wave
circuits 22, 23 and 28, respectively. And in the case where
the difference of angle (~1 - 82) is within the range of
between -180 and +180, i.e., -180 _ (01 - ~2) ~ ~180,
both of the +180 crossover detection circuit 23 and -180
crossover detection circuit 24 do not operate, so that the
+180 crossover switching circuit 36 opens the contacts 25b
of the signal switching circuit 36 and closes the contacts
25a of the same. As a result, the sinusoidAl signal sin (01
- 02) is inputted to the limiter 8 intactly. The output
signal SL of the limiter 8 is therefore a signal derived from
the sinusoidal signal sin (el - 02) with its amplitude
limited to the values determined by the limiter 8.
12-
5'.~
Next, when the difference of angle (01 - 02) exceeds
180, the both output signals of the +180 crossover
detection circuit 23 and the polarity decision circuit 29 go
to H level, so that the flip-flop 30 is brought into a set
state. A~ a result, +180 crossover switching circuit 36
opens the contacts 25a of the signal switching circuit 25 and
closes the contacts 25b of the same, so that a positive
voltage obtained by amplifying the output of the flip-flop 30
in a non-inverting fashion by the operational amplifier 34 is
fed to the input terminal of the limiter 8. And during this
operation, the signal SQ is kept to a constant voltage level.
Thus, the propeller housing 2 i5 rotated in accordance with
the output signal SQ of the limiter 8. And when the
difference of angle (01 - 02) is decreased to an extent that
the polarity of the sinusoidal signal sin ~01 - a2 + 45) is
changed, that is to say, the diference vf angle (01 - 02)
becomes less than ~135, the flip-flop 30 is brought into a
reset state (see the waveform indicated by a dot and dash
line in Fig. 6). Consequently, +180 crossover switching
circuit 36 opens the contacts 25b of the signal switching
circuit 25 and closes the contacts 25a of the same, so that
the sinusoidal signal sin (01 - 02) is intactly supplied to
the input terminal of the limiter 8.
When the difference of angle (el - ~2~ becomes less than
-180, the both outputs of the -180 crossover detection
circuit 24 and the polarity decision circuit 29 go to H
level, so that the flip-flop 31 is brought into a set state.
As a result, +180 crossover switching circuit 36 opens the
contacts 25a of the signal switching circuit 25 and closes
the contacts 25b of the same, so that a negative voltage
obtained by inversely amplifying the output of the flip-flop
31 by the operational amplifier 34 is applied to the input
terminal of the limiter 8. Thus the propeller housing 2 is
rotated in accordance with the signal S~ outputted from the
limiter 8, the signal S~ being at a negative constant voltage
. And when the difference of angle ~ a2 ) is increased to
an extent that the polarity of the sinusoidal signal sin (~1
- ~2 + 45) is changed, that is to say, the difference of
angle (01 - 92) becomes greater than -45, the flip-flop
reset circuit 33 resets the flip-flop 31 ( see the waveform
indicated by the dot and dash line in Fig. 6 ), so that the
180 crossover switching circuit 36 opens the contacts 2sb
of the signal switching circuit 25 and closes contacts 25a of
the same. As a result, the sinusoidal signal sin (01 - ~2)
is intactly supplied to the input terminal of the limiter 8.
The signal thus inputted to the limiter 8 is outputted
to the servo control circuit 9 as the signal SL whose
20 amplitude has been limited to predetermined levels by the
limiter 8, as shown in Fig. 6.
The servo control circuit 9 controls the servomotor 9 in
accordance with the signal S~, and the servomotor 9 controls
the hydraulic motor 19 through the hydraulic pump 11, the
hydraulic cylinder 14 and the hydraulic pump 15 to rotate the
worm 20 of the shaft 5 in accordance with its rotational
movement. As a result, the worm wheel 21 rotates so that the
propeller hou.sing 2 of the Z-type propulsion apparatus begins
-14-
to rotate in unison with the steering handle 1 in the
direction of rotation thereof~ And when the difference of
angle (~ 2) reaches 0 the propeller housing 2 stops~
Thus, with the construction of this system, the signal
processing circuit 7 can control the propeller housing 2 so
as to rotate in unison with the steering handle 1 in the
direction of rotation thereof on condition tha-t the
difference of angle (01 - ~2) is within the range of between
-225 and +315, i.e., -225 < (01 - 02) ~ +315.
With the construction of this system, if the steering
handle is operated to command such a rapid rotation of the
propeller housing 2, which is beyond the response
characteristic of the mechanical system, that the difference
of angle (~1 - e2) becomes less than -225 ( -360 ~ (01 -
02) _ -225 ~ or more than ~315 ( ~315 _ (01 - ~2) < +360
), the propeller housing rotates in the direction opposite to
that of rotation of the steering handle 2. However, when it
is desired to rotate the propeller housing by more than 225,
the steering handle is usually operated so that it rotates
not in the forward direction beyond 180 but in the reverse
direction. Actually, it is rare to command the propeller
housing to rotate by more than 225, so that any significant
problem will not be encountered~
The sinusoidal signals sin (01 - ~2) and sin (91 - ~2 +
45) and the cosine signal cos (~1 02) may alternatively be
obtained by employing synchros and Scott transformers and
removing the ac components from its output signals. These
-15-
sinusoidal and cosine signals may also be obtained by
employing resolvers and differential transformers or by
employing rotary encoders or the like.
Fig~ 7 shows a second embodiment of the present
invention in which like references denote same parts of the
first embodiment of the invention. A calculation circuit 6a
of this system is so constructed as to supply the sinusoidal
signal sin t01 - ~2) representing a sine of the difference of
angle (~ 2) between the angular position 01 of the
steering handle 1 and the angular position 82 of the
propeller housing 2 to a sample and hold circuit 38 of a
signal processing circuit 7a and to supply the cosine signal
cos (~ 2~ representing a cosine of the difference of
angle (~1 - e2 ) to a polarity decision circuit (comparator)
39 of the signal processing circuit 7a. The polarity
decision circuit 39 detects the polarity of the cosine signal
cos (~1 - 02) and feeds the detection result to the sample
and hold circuit 38. The sample and hold circuit 38 is so
constructed as to hold the inputted signal when the polarity
decision circuit 39 detects a negative signal, and an output
terminal of this sample and hold circuit 38 is connected to
the limiter 8. The limiter 8 is connected to the servo
control circuit 9 for controlling the SerVOmotGr 10.
The operation of this system will now be described with
reference to Fig. 8.
When the steering handle 1 is pivotally moved, the
calculation circuit 6a executes a calculation using the
output signals sin 01 and cos 01 of the angular position
-16-
detector 3 and the output signals sin 02 and cos 02 of the
angular position detector 4 to form two kinds of signals,
i.e., the sinusoidal signal sin (01 - 02) and the cosine
signal cos (01 - 02), (see Fig. 8). The polarity decision
circuit 39 detects the polarity of the cosine signal cos (~1
02) outputted from the calculation circuit 6a and brings
the sample and hold circuit 38 into a sample mode A when the
cosine signal cos (01 - 02) is equal to or more than a
predetermined value 0 ( cos (01 - ~2) -~ 0 ). As a result,
the sinusoidal signal sin (01 - Q2) outputted from the
calculation circuit 6a to the sample and hold circuit 38 is
intactly supplied to the limiter 8. The polarity decision
circuit 39 brings the sample and hold circuit 38 into a hold
mode B when the cosine signal cos (~1 - 92) is less than 0 (
cos (01 - ~2) < 0 ). As a result, a signal representative of
the value sin ( +90 ) is inputted to the limiter 8 when the
difference of angle (01 - ~2) is greater than 90 ((01 - ~2)
90 ), while a signal representative of the value sin ( -90
) is inputted to the limiter 8 when the difference of angle
(~ 2) is less than 90 ((91 - 02) < 90 ). An output
signal Ss of the sample and hold circuit 38 is the sinusoidal
signal sin (~1 02) itself outputted from the calculation
circuit 6a when the difference of angle (01 - 02) is between
-90 and +90 ( -90 - (61 - 92) <- +90 ~. The signal Ss is
a signal representative of the value sin ( -90 ) when the
difference of angle (01 - ~2) is between -270 and -90 ( -
270 < (01 - ~2) < -90 ) and i5 a signal representative of
the value sin ( +90 ) when the difference of angle (~1 - 02)
i5 between +90 and -~270 ( +90 < (~1 - 02) ~ +270 ). The
limiter 8 limits the amplitude of the output signal of the
sample and hold circuit 38 to form a signal S~ shown in Fig.
8 and feeds it to the servo control circuit 9. The servo
control circuit 9 controls the servomotor 10 in accordance
with the signal S~, and the servomotor 10 controls the
hydraulic motor 19 through the hydraulic pump 11, the
hydraulic cylinder 14 and the hydraulic pump 15 to rotate the
worm 20 of the shaft 5. As a result, the worm wheel 21
rotates so that the propeller housing 2 of the Z-type
propulsion apparatus hegins to rotate in unison with the
steering handle 1 in the direction of the rotation thereof.
And when the difference of angle (~1 - a2 ) reaches 0 the
propeller housing 2 stops. Thus, the signal processing
c.ircuit 7a can control the propeller housing 2 to rotate in
unison with the steering handle 1 in the direction of
rotation thereof on condition that the difference of angle
(01 - ~2) is within the range of between -270 and ~270,
i.e., -270 < (~ 2) ~ ~270.
In the above-described system, the polarity decision
circuit 39 is so constructed as to hold and output the
sinusoidal signal sin (al - 02) when ~he cosine signal cos
~ 02) is negative, however the circui~ 39 may be modified
so as to hold the sinusoidal signal sin (~1 - H2 ) when the
cosine signal cos (01 - ~2) is less than a predetermined
value other than 0. With the construction of this system,
the sample and hold circuit 38 does not hold the sinusoidal
signal sin (01 - ~2) when the difference of angle (01 - 02)
-18-
s
is between -360 and -270 ( ~360 < (01 - 02) ~ -270 ) or
when the difference of angle (~ 2) is between -~270 and
~360 ( ~270 ~ 92) ~ +360). Therefore, if the
steering handle is operated to command such a rapid rotation
S of the propeller housiny 2, which is beyond the response
characteristic of the mechanical system, that the absolute
value of the difference of angle (~ 2) becomes greater
than ¦+270¦, the propeller housing 2 rotates in the
direction opposite to that of rotation of the steering handle
1. However, when it is desired to rotate the propeller
housing by more than +270, the steering handle is usually
operated in such a manner that the propeller housing rotates
not in the forward direction beyond 180 but in the reverse
direction~ Actually, it is rare to command the propeller
housing to rotate by more than +270, so that any significant
problem will not be encountered.
Fig. 9 shows a third embodiment of the invention in
which like references denote same parts of the second
invention.
In the figure, the sinusoidal signal sin (~ 2)
outputted from the calculation circuit 6a is supplied to the
sample and hold circuit 38 of a signal processing circuit 7b
and to one input terminal of a polarity comparator 40. The
cosine signal. cos (01 - ~2) outputted from the circuit 6a is
fed to the polarity decision circuit 39 of the signal
processing circuit 7bo An output signal of the sample and
hold circuit 38 is supplied to the input terminal of the
servo control circuit 9 and to the other input terminal of
--19--
~Z~ 5
the polarity comparator 40. The polarity decision circuit 39
outputs a true signal when the cosine signal cos (~1 - 02) is
negative, and the polaxity comparator 40 outputs a true
signal when the two input signals are different in polarity
to each other. And the output signals of the polarity
decision circuit 39 and the polarity comparator 40 are
logically added by an OR circuit 41, and the resultant signal
is fed to the sample and hold circuit 38. When the output
signal Sl of the OR circuit 41 is true, the sample and hold
circuit 38 holds its input signal. And when the signal Sl is
false, the circuit 38 samples its input and outputs it.
The operation of this system will now be described with
reference to Fig. 12. When the difference of angle (01 - 02)
is between -90 and +90 ( -90 <- (61 - ~2) ~ +90 ), the
output of the polarity decision circuit 39 is not true. And
in this case, the output of the polarity comparator 40 is
also not true, so that the sample and hold circuit 38 is
brought into the sample mode A to output the sinusoidal
signal sin (01 - 02) intactly.
When the difference of angle (01 - ~2) exceeds +90, the
cosine signal cos (01 - ~2) becomes less than 0, so that a
true signal is outputted from the polarity decision circuit
39~ As a result, the OR circuit 41 outputs the signal Sl
(hold signal) to bring the sample and hold circuit 38 into
the hold mode B, so that ~he circuit 38 outputs a signal
representative of the value sin ( +90 ), i.e., the
sinusoidal signal sin (~1 - 02) at the moment when the
difference of angle (al - 02) is equal to +90~ The hold
-20-
~ 4 ~rj
mode B is maintained so lon~ as the difference of angle (~1 -
02) i5 between +90 and ~270 ( ~90 ~ (01 - 02) < +270 ).
If the difference of angle exceeds ~270, the cosine signal
cos (01 - ~2) becomes positive. In this case however, the
polarities of the input and output signals of the sample and
hold circuit 38 differs from each other, so that the polarity
comparator 40 outputs a true signal, thereby the hold si~nal
Sl being outputted from the OR circuit 41. As a result, the
sample and hold circuit 38 is brought into the hold mode C to
output the positive value sin ( +90 ). The hold mode C i5
maintained so long as the difference of angle (~1 - 02) is
between +270 and +360 ( +270 <- (01 - 02) < ~360 ), since
the polarity of the output of the sample and hold circuit 38
differs from that of the sinusoidal signal sin (~1 - 02).
If the difference of angle becomes less than -90, the
cosine signal cos (01 - 02) becomes less than 0 so that the
polarity decision circuit 39 outputs a true signal. As a
result, the OR circuit 41 outputs the hold signal Sl, so that
the sample and hold circuit 38 is brought into the hold mode
B to output sin ( -90 ), i.e., the value of the sinusoidal
signal sin (al - 92) at the moment when the difference of
angle (01 - 02) is equal to -90. The hold mode B is
maintained so long as the difference of angle (01 - ~2) is
between -270 and -90 ( -270 < (01 - 02) ~ -90 ). If the
difference of angle (el - 02) becomes less than -270, the
cosine signal cos (01 - ~2) becomes positive. In this case
however, the polarity comparator 40 outputs a true signal,
since the polarities of the input and output of the sample
-21-
4LS
and hold circuit 38 are dif~erent from each other. As a
result, the OR circuit 41 ou-tputs the signal Sl, so that the
sample and hold circuit 38 is brought into the hold mode C to
output the negative value sin ( -90 ). The hold mode is
maintained so long as the difference of angle (~ 2) is
between -360 and -270 ( -360 < (al ~ ~2) - -270 ), since
the polarities of the input and output of the sample and hold
circuit 38 differ from each other.
Thus, with the construction of this system, the
propeller housing 2 is controlled to rotate in unison with
the ~teering handle 1 in the direction of rotation thereof on
condition that the difference of angle (~ 2) is within
the rang~ of ~360. In this system, the polarity decision
circuit 39 may be modified so as to output a true signal when
the cosine signal cos (~ 2) is less than a predetermined
value other than 0.
Fig. 10 shows a fourth embodiment of the present
invention.
This system differs from the system shown in Fig. 9 in
the following respects. In a signal processing circuit 7c of
this system, the both signals at the input and output
terminals of the sample and hold circuit 38 axe inputted to
both input terminals of an error detection circuit 42. The
error detection circuit 42 detects the difference (error)
between the two signals inputted thereto and outputs the
error to an error comparator 43. The error comparator 43 is
constructed in such a manner that it outputs a true signal
when the output of the error detection circuit 42 is greater
-22-
than a predetermined value ( for example, 1 corresponding to
the value sin 90 ). The output of the error comparator 43
is supplied to the other input terminal of the OR circuit 41.
The operation of this system will now be described with
reference to Fig. 12.
When the difference of angle (01 - 02) is within ~90,
the output of the polarity decision circuit 39 is not true.
And in this case, the output of the error comparator 43 is
also not true since the output of the error detector 42 is 0,
so that the sample and hold circuit 38 is brought into the
sample mode A to output the sinusoidal signal sin (~1 ~ 02)
intactly.
When the difference of angle (01 - 02~ exceeds ~90, the
cosine signal cos (~ 2) becomes less than 0, so that a
true signal is outputted from the polarity decision circuit
39. As a result, the OR circuit 41 outputs the signal S1 to
bring the sample and hold circuit 38 into the hold mode B, so
that the circuit 38 outputs a signal representing the value
sin ( +90 ), i.e., the sinusoidal signal sin (~ 2) at
the moment when the difference of angle (01 - 02) is equal to
+90. The hold mode B is maintained so long as the
difference of angle (~ 2) is between +90 and ~270 (
+90~ ~ (01 - ~2) ~ +270 ). If the difference of angle (01 -
~2) exceeds ~270, the cosine signal cos (01 - 02) becomes
positive. In this case however, the output ( error ) of the
error detect.ion circuit 42 is greater than the value
predetermined at the error comparator 43 ( it is assumed
herein that the predetermined value is 1 ), so that the error
-23-
comparator 43 outputs a true signal, thereby the hold signal
Sl being outputted from the OR circuit 41. As a result~ the
sample and hold circuit 38 is brought into the hold mode C to
output the positive value sin ( +90 ). The hold mode C is
maintained so long as the difference of angle (al - ~2) is
between +270 and +360 ( ~270 ~ (~1 - 02) < +360 ), since
the difference between the output and input of the sample and
hold circuit 38 is greater than the predetermined value ( = 1
).
If the difference of angle (~ 2) becomes less than
-90, the cosine signal cos (~ 2) becomes less than 0 so
that the polarity decision circuit 39 outputs a true signal.
As a result, the OR circuit 41 outputs the hold signal Sl, so
that the sample and hold circuit 38 is brought into the hold
mode B to output sin ( -90 ), i.e., the value of the
sinusoidal signal sin (91 - 02) at the moment when the
difference of angle (01 - 92) is equal -to -90. The hold
mode B is maintained so long as the difference of angle (~1 -
~2) is between -270 and -90 ( ~270 ~ 2) < -90 ).
If the difference of angle (01 - ~2) becomes less than -270,
the cosine signal cos ~01 - ~2) becomes positive. In this
case however, the error comparator 43 outputs a true signal,
since the output ( error ) of the error detection circuit 42
is greater than the value ( = 1 ) predetermined at the error
comparator 43. As a result, the OR circuit 41 outputs the
signal Sl, so that the sample and hold circuit 38 is hrought
into the hold mode C to output the negative value sin ( -90
). The hold mode C is maintained so long as the difference
-24-
s
of angle (~ 2) is bet~een -360 and -270 ( -360 ~
~2) ~- ~270 ), since the difference between the output and
input of the sample and hold circuit 38 is greater than the
predetermined value.
Thus, with the construction of this system, the
propeller housing 2 is controlled to rotate in unison with
the steering handle 1 in the direction of rotation thereof on
condition that the difference of angle (~ 2) is within
the range of +360.
_
Incidentally, a limiter circuit may be provided at the
input terminal of the servo control circuit 9 to limit the
amplitude of the output signal of the sample and hold circuit
38 to appropriate values. In the syste~ described above, it
is assumed that the value predetermined at the error
comparator 43 is 1, however, the value may be increased or
decreased from 1 to expand or reduce the hold mode range.
Further, the polarity decision circuit 39 may be modified so
as to output a true signal when its input becomes less than a
predetermined value other than 0.
Fig. 11 shows a fifth embodiment of the present
invention.
A signal processing circuit 7d of this system shown in
this figure differs from those of the second to fourth
embodiments in the following respects.
The sinusoidal signal sin (~1 - 92) outputted from the
calculation circuit 6a is supplied to the input terminal of
the sample and hold circuit 38 and to an input terminal of a
polarity decision circuit 44. The polarity decision circuit
-25-
44 outputs a signal S2 indicating whether the sinusoidal
signal sin (~ 2) is positive or negative. The cosine
signal cos (~ 2) outputted from th~ calculation circuit
6a is supplied to a polarity-inversion detection circuit 45.
The polarity-inversion detection circuit 45 outputs a pulse
signal P when a positive to negative or a negative to
positive change of the polarity of the cosine signal cos (~1
- ~2) is detected. The pulse signal P is fed to a pulse
generating circuit 46. When the pulse signal P is inputted
to the the pulse generating circuit 46 with a signal S2
representing a polari~y of the sinusoidal signal sin (~1 -
~2) different from that represented by it when the preceding
pulse signal P is generated, the circuit 46 outputs one of an
increment pulse Pl and a decrement pulse P2 which is the same
as the pulse precedingly outputted therefrom. The pulse
generating circuit 46 outputs one of the increment and
decrement pulses which is of the type different from that of
the pulse precedingly outputted therefrom, when the pulse
signal P is inputted thereto with the signal S2 representing
the same polarity of the signal sin (~ 2) as that
represented ~y it when the preceding pulse signal P is
generated. The increment and decrement pulses are fed to a
counter circuit 47. The count value outputted from the
counter circuit 47 is supplied to a zero detection circuit 48
to decide whether the value is zero or not. This zero
detection circuit 48 brings the sample and hold circuit 38
into a sample mode when the count value of the counter
-26-
s
circuit 47 is zero, while it brings the sample and hold
circuit into a hold mode when the count value is other than
0.
The operation of the above system will now be described
with reference to Fig. 12.
When the difference of angle (Ql - 02) is within -~90
the polarity of the cosine signal cos (01 - ~2) does not
change, so that the pulse signal P is not outputted. In this
case, the count value of the counter circuit 47 is 0. And
therefore, the sample and hold circuit 38 is kept in the
sample mode by the output of the ~ero detection circuit 48
and outputs the sinusoidal signal intactly.
Next, when the difference of angle (01 - 02) exceeds
+90, the cosine signal (91 - B2 ) changes its polarity from a
positive to a negative state/ so that pulse signal P is
outputted from the polarity-inversion detection circuit 45.
At this moment, the polarity decision circuit 44 outputs to
the pulse generating circuit 46 signal S2 indicating that the
sinusoidal signal sin (01 - 02) is positive. The pulse
generating circuit 46 stores the state indicating that the
sinusoidal signal sin (01 - e2 ) is positive and at the same
time outputs increment pulse Pl to the counter circuit 47
since the contents of the counter circuit 47 is 0. As a
result, the count value of the counter circuit 47 is
incremented from 0 to +1, which causes the zero detection
circuit 48 to output the hold signal to the sample and hold
cixcuit 38. The sample and hold circuit 38 therefore holds
and outputs ( hold mode ) sin ( -90 ), i.e., the value of
the sinusoidal signal sin (01 - ~2) at the moment when the
difference of angle (01 - 02 ) i5 equal to -90. In this
system, when the difference of angle (~1 02) becomes less
than -90, increment pulse Pl is supplied to the counter
circuit 47 to increment its contents from 0 to +1 as
described above. However, this system may be modified 50
that when th~ difference of angle (Ql - 02) is less than -90
decrement pulse P2 is supplied to the counter circuit 47 to
decrement its contents from 0 to -1.
Next, the case where the steering handle is abruptly
rotated clockwise by +300 will now be described in detail.
In the beginning of a clockwise rotation of the steering
handle 1, the follow-up angle 02 remains 0 since the follow-
up operation has not yet been commenced, so that only the
steering angle 01 begins to increase. And when the steering
angle 01 exceeds +90 the difference of angle (~1 - 92~
exceeds +90, so that the polarity of the cosine signal cos
~01 - 02) is changed from a positive to a negative state. At
this moment, the polarity of the sinusoidal signal sin (01 -
~2) is positive, and the contents of the counter circuit 47is 0. The pulse generator 46 therefore memorizes the
positive polarity of the sinusoidal signal sin (~ 2) and
outputs increment pulse Pl to increment the contents of the
counter circuit 47 from 0 to +1. As a result~ the sample and
hold circuit 38, which has outputted the sinusoidal signal
sin (01 - 02) intactly ( sample mode ) until then, holds and
outputs ( hold mode ) the value sin ( +90 ). And when the
steering angle 01 exceeds +270, the difference of angle (01
-28-
- ~2) also exceeds +270, so that the polarity of the cosine
signal cos (~ 2) is changed from a neyative to a positive
state. At this moment, the polarity of the sinusoidal signal
sin (al - 02) is negative, and the pulse generating circuit
46 compares this polarity with the polarity of the signal sin
(~1 - 02) precedingly stored thereinto. The polarity
precedingly stored is positive and the present polarity is
negative, so that the pulse generating circuit 46 stores the
present polarity thereinto and outputs the same kind of pulse
signal ( increment pulse Pl ) as that previously outputted
therefrom. As a result, the count value of the counter
circuit 47 is incremented from +1 to +2. The resultant count
value of the counter circuit 47 is not O, so that the sample
and hold cixcuit 38 continues to output the value sin ( +9O
). When the steering angle ~1 becomes +300, the follow-up
operation is commenced, so that the follow-up angle ~2 begins
to increase, thereby the difference of angle (~ 2) being
decreased. And when the difference of angle (~ 2)
becomes less than +270, the polarity of the cosine signal
cos (~ 2) is changed from a positive to a negative state.
At this time, the polarity of the sinusoidal signal sin (~1 -
~2~ is negative, 50 tha~ the pulse generating circuit 46
stores the present polarity of the signal sin (~ 2) and
outputs a pulse signal ( decrement pulse P2 ) which is of the
kind different from that of th~ pulse signal precedingly
outputted therefrom. As a result, the count value of the
counter circuit 47 is decremented from +2 to ~1. The sample
and hold circuit 38 therefore continues to output the value
-29-
4~
~in ( t90 ). When the difference of angle (~ 2) is
decreased to less than ~90, the polarity of the cosine
signal cos (al - ~2) is changed from a negative to a positive
state. The polarity of the sinusoidal signal sin (~ 2)
at this time is positive and the polarity of the signal sin
~ 2) precedingly stored is negative, the pulse
generating circuit 46 therefore outputs the same kind of
pulse signal ( decrement pulse P2 ) as that precedingly
outputted therefrom. As a result, the count value of the
counter circuit 47 is decreased from fl to 0, so that the
sample and hold circuit 38 is released from its hold mode and
outputs the sinusoidal signal sin (01 - ~2) intactly ( sample
mode ). And when the difference of angle (~ 2) reaches
0, the follow-up operation i5 completed.
With the construction of the above-described ~ystem,
even when the difference of angle (Gl - ~2~ is varied in any
way, for example, even when the difference of angle (~ 2)
exceeds ~360, the propeller housing 2 is controlled to
rotate in unison with the steering handle in the direction of
rotation thereof. And if the counting capacity of the
counter circuit 47 is increased, the propeller housing 2 can
be controlled to rotate a plurality of revolutions in unison
with the steering handle. The system may also be modified by
setting the counting capacity to an appropriate value so as
to restrict the maximum number of its revolutions to a
specific value. In addition, the ratio of the steering angle
01 to the follow-up angle ~2 i5 not limited to 1 : 1 but car
be changed to 1 : n or n : 1 to enhance the accuracy of the
-30-
operation. ~urther, the construction for effecting the
counting operation at the countex circuit 47 may be modified
so that the polarity of the cosine signal cos (~1 - 32~
immediately after a change of the polarity oE the same is
compared with that of the sinusoidal signal sin (fll - ~2) to
decide which pulse should be generated an increment pulse or
a decrement pulse. In this case, the pulse generating
circuit 46 is modified so that it outputs a decrement pulse
to the counter circuit 47 to decrement its contents by one
when the two polarities coincide with each other and that the
circuit 46 outputs an increment pulse to the counter circuit
47 to increment its contents by one when the two polarities
are different from each other.
-31-
