Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2 1 0 2 ~ 6 2
CONTACT PREVENTION SYSTEM FOR A BACKHOE
The present invention relates to a system for
preventing a bucket of a backhoe from contacting an outer
frame defining an outermost region of a driver's section.
An example of backhoe structure designed to avoid
contact between a bucket and an outer frame defining an
outermost region of a driver's section is illustrated in
Fig. 7 and labelled "Prior Art".
In the illustrated prior structure, a danger plane is
established in a space and at a predetermined distance
outwardly of the outer frame defining the outermost region
of the driver's section is. A position sensor detects
position of a bucket pin of a boom assembly. An operation
prohibiting device is provided which is operable in
response to the position sensor. This device stops
hydraulic cylinders which drive the boom assembly, before
the bucket pin moves past the danger plane toward the
driver's section.
This structure defines a danger zone between the
danger plane and a caution plane established in a space and
at a predetermined distance outwardly of the danger plane.
A decelerating device computes a distance in a horizontal
direction from the danger plane to a current position of
the bucket pin, and decelerates operation of the hydraulic
cylinders by the greater degree as the bucket pin moves
closer to the danger plane.
In this prior structure, when the bucket pin lies in
the danger zone, a
-- 1 --
21~ 21 6 2
deceleration rate of the hydraulic cylinders is determined only on the basis
of a ~,i~n~ x~ ce from the danger plane to the bucket pin.
Consequently, when the bucket pin moves s~1bsl~ ;ally holi~ontally
from a given position in the danger zone toward the danger plane, the
4~d,aulic cylinders are decele.dted at the deceleration rate based on the
~o~ noe to the danger plane. The hydraulic cylinders are stopped
when the bucket pin reaches the danger plane. Such an operation of the
boom ~se,.-l.ly agrees with the operating feeling of the driver.
According to the prior structure, the ~lec~leration rate is cletçrmin~ by
o the hori~nlal distance to the danger plane also when the bucket pin moves
obliquely upward and gradually from a given position in the danger zone
toward the danger plane. Although the bucket pin moves a relatively long
d;st~nce (in an obliquely upward direction) to the danger plane, the llydlaulic
cylinders are decelerated as in the case of ho~ntal movement of the
bucket pin. As a result, the bucket is raised through the danger zone a
little too slowly. Thus, there is room for improvement from the viewpoint
of operating efficiency.
The object of the pl~nl in~.enlion is to provide imp,~ed operating
20 efficiency for a bae~oe having the above dan~er plane and danger zone
eotl-,ept, espec;~11y when the bucket lies in the danger zone.
The above object is f llfill~l, acco~iing to the p~senl invention, by a
ba~hoe ccmpnsing a first setting device for setting a danger plane in a
space and at a pn~del~,llined ~lict~nce outwardly of an outer frame deffnin~
an outern~osl region of a driver's section disposed on a swivel deck, a
second setting device for setting a danger zone l,et~n the danger plane
.~
~21S~ K6350
and a plane in a space and at a predetermined distance outwardly of the
danger plane, a position sensor for detecting a position of a bucket of a
boom assembly, a direction sensor for detecting a direction of movement
of the bucket, a velocity sensor for detecting a velocity of movement of
5 the bucket, a safety device opeMble in response to the position sensor and
the direction sensor to stop boom assembly driving hydraulic cylinders to
prevent the bucket from moving past the danger plane toward the driver's
section, and a decelerating device operable in response to the position
sensor, direction sensor and velocity sensor, when the bucket lies in the
o danger zone, to decelerate operation of the hydraulic cylinders to
subst~nti~lly equalize time taken for the bucket to move from a current
position thereof in the danger zone to the danger plane regardless of a
current direction of movement of the bucket.
With the above construction, when the bucket lies in the danger zone,
15 for example, the sensors detect a current position, direction of movement
and velocity of movement of the bucket. It is then possible to compute a
horizontal distance Ll from the current bucket position to the danger plane
or a moving distance L2 along the direction of movement to the danger
plane. Assuming that the bucket is uniformly deceleMted from the current
20 velocity of movement, it is possible to estim~te time taken for the bucket
to move the di~t~nce Ll or L2 from the current position to the danger
plane.
The hydMulic cylinders are decelerated to equalize the above estimated
time to a set time in an instantaneous position of the bucket (the set time
25 being a function of stopping time with respect to distance where a minimum
distance between the danger plane and bucket is used as a variable and the
bucket is assumed to make an ideal decelerated motion).
h ~ K6350
Thus, when the bucket moves horizontally in the danger zone, the
distance Ll from the bucket to the danger plane is expected to be relatively
short so that the bucket reaches the danger plane relatively quickly. In this
case, the boom assembly driving hydraulic cylinders are decelerated by an
s increased degree whereby the bucket reaches the danger plane upon lapse
of the set time.
Conversely, when the bucket lies in the same position as above but
momentarily moves obliquely upward or downward, the distance L2 from
the bucket to the danger plane is relatively long. In this state, the bucket is
expected to consume a relatively long time before re~ching the danger
plane under the ordinary deceleration control noted above. However, the
boom ~semhly driving hydraulic cylinders are decelerated only by a small
degree to cause the bucket to reach the danger plane upon lapse of the
above set time.
Thus, the present invention avoids an excessive deceleration of the
bucket when the bucket moves a relatively long di~t~nce (the ~list~nce
along the direction of movement of the bucket) to the danger plane as
when the bucket moves obliquely upward and gradually from a given
position in the danger zone toward the danger plane.
According to the present invention, as described above, the position,
direction of movement and velocity of movement of the bucket in the
danger zone are detected in order to prevent the bucket movement from
becoming too slow, thereby to improve the operating efficiency of the
bucket.
Other features and advantages of the invention will be apparent from
the following more particular description of preferred embodiments of the
invention, as illustrated in the accompanying drawings.
2 ~ 2 K6350
BRIEF DESCRIPIION OF THE DRAWINGS
Fig. 1 is a side elevation of a backhoe;
Fig. 2 is a schematic side view of the backhoe, showing a front danger
5 plane, a front danger zone and a front caution plane;
Fig. 3 is a side view of a bucket moving in the front danger zone;
Fig. 4 is a schematic plan view of the backhoe, showing the front
danger plane, a side danger plane, the front danger zone and a side danger
zone;
Fig. 5 is a view showing relations among hydraulic cylinders, control
valves, pilot valves and right and left control levers of a boom assembly;
Fig. 6 is a flowcha, I of boom assembly controls effected when a bucket
pin is on the front or side danger plane and in the front or side danger
zone;
Fig. 7 is a schematic side view of a backhoe, showing a front danger
plane and a front danger zone according to the prior art;
Fig. 8 is a view showing a relationship between a predetermined time
and a hor~olllal distance of the bucket pin to the danger planes;
Fig. 9 is a flowchart of boom assembly controls effected when the
20 bucket pin is on the front or side danger plane and in the front or side
danger zone, in a second embodiment of the present invention; and
Fig. 10 is a flowchart of boom assembly controls effected when the
bucket pin is on the front or side danger plane and in the front or side
danger zone, in a third embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be described hereinafter
21 0 21 ~ ~ K6350
with ~e~--ce to the drawings.
Fig. 1 shows a side elevation of a backhoe. This backhoe has a rubber
crawler type running device 1 carrying a bulldozer blade 20, and a swivel
deck 2 mounted on the running device 1. A boom ~cemhly 3 is connect~l
s to a front position of the swivel deck 2. The boom a~sernhly 3 includes a
boom 4 vertically pivotable by a hydraulic cylinder 11, an arm 5 pivotable
back and forth by a hydraulic cylinder 12, and a bucket 6 pivotable by a
hydraulic cylinder 13 to take shoveling action. The swivel deck 2 is
swivelable by a hydraulic motor 14.
o As shown in Figs. 1 and 4, the boom 4 includes a vertically pivotable
first boom portion 4a, a second boom portion 4b connected to the first
boom portion 4a to be pivotable about an axis Pl at a forward end thereof,
and a support bracket 4c connected to the second boom portion 4b to be
pivotable about an axis P2 at a 1~l ~a~ end thereof. The arm 5 is connected
to the support bracket 4c. An interlocking link 8 exten-l~ between the first
boom portion 4a and support bracket 4c to constitute a parallelogram link
mech~ni~m Thus, when the hydraulic cylinder 7 is operated to cause
pivotal movement of the second boom portion 4b, the arm 5 and bucket 6
are moved sideways in parallel.
As shown in Fig. 5, a control system includes a control valve 21
connected to the hydraulic cylinder 11 for flctu~tin~ the first boom portion
4a, a control valve 25 connected to the hydraulic cylinder 7 for actuating
the second boom portion 4b, a control valve 22 connected to the hydraulic
cylinder 12 for actuating the arm 5, a control valve 23 connected to the
hydraulic cylinder 13 for actuating the bucket 6, and a control valve 24
connected to the hydraulic motor 14 for swiveling the swivel deck 2.
These control valves 21-25 are pilot-operated three-position valves whose
~10 21~ ~ K6350
opening degrees are adjustable by pilot pressure to control flow rate. Opening
degree adjusting pilot pressures are generated by pilot valves 31a, 31b,
32a, 32b, 33a, 33b, 34a, 34b, 35a and 35b which are electromagnetic
proportional pressure reducing valves.
s Referring to Figs. 1, 4 and 5, the swivel deck 2 carries a right control
lever 9 and a left control lever 10. These control levers 9 and 10 are
rockable fore and aft and right and left. The control system further includes
a potentiometer 15 for detecting a position in the fore and aft direction of
the right control lever 9, a potentiometer 16 for detecting a position in the
right and left direction of the right control lever 9, a potentiometer 17 for
detecting a position in the fore and aft direction of the left control lever 10,and a potentiometer 18 for detecting a position in the right and left direction
of the left control lever 10. These potentiometers 15-18 transmit control
sign~l~ to a control unit 19. A control pedal 26 is disposed in a lower
front position of the swivel deck 2, which also tr~n~mit~ a control signal to
the control unit 19.
According to the above construction, when the right control lever 9 is
operated forward or backward, the pilot valve 31a or 31b generates a pilot
pressure for causing the control valve 21 to lower or raise the boom 4.
When the right control lever 9 is operated right or left, the pilot valve 33a
or 33b generates a pilot pressure for causing the control valve 23 to actuate
the bucket 6 in an earth pushing direction or a rake-in direction. When the
left control lever 10 is operated forward or backward, the pilot valve 32a
or 32b generates a pilot pressure for c~ ing the control valve 22 to actuate
the arm 5 forward or backward. When the left control lever 10 is operated
right or left, the pilot valve 34a or 34b generates a pilot pressure for
causing the control valve 24 to effect a right or left swivel of the swivel
~ ~ ~ 2 ~ 6 2 K6350
deck 2. When the control pedal 26 is depressed right or left, the pilot
valve 35a or 35b geneMte a pilot pressure for c~llsing the control valve 25
to swing the second boom portion 4b rightward or leftward.
In the above operation, the potentiometers 15-18 detect not only the
directions of operation of the right and left control levers 9 and 10 but also
amounts of operation thereof from respective neutral positions.
Consequently, the larger the amount of operation of the control levers 9
and 10, the higher pilot pressure is generated by the pilot valves 31a-34b
to operate the control valves 21-24 for the higher flow rate. That is, the
o larger the amount of opeMtion of the control levers 9 and 10, the faster the
hydraulic cylinders 11-13 and hydraulic motor 14 are operated.
Referring to Figs. 1 and 5, the control system further includes a
potentiometer 36 (acting as position, direction and velocity detecting means)
for detecting a vertical angle of the boom 4 (first boom portion 4a), a
potentiometer 37 (acting as position, direction and velocity detecting means)
for detecting a horizontal angle of the second boom portion 4b, and a
potentiometer 38 (acting as position, direction and velocity detecting means)
for detecting a fore and aft angle of the arm 5. These potentiometers
36-38 t~ansmit detection signals to the control unit 19.
As shown in Figs. 1 and 4, the swivel deck 2 has the boom assembly 3
disposed on the right side thereof, while on the left side is a driver's
section 27 including a driver's seat 28 and the right and left control levers
9 and 10. A vertical partition plate 29 (acting as part of an outer frame
defining an outermost region of the driver's section 27) having a window
iS erected in a transversely middle position on the swivel deck 2 to separate
the boom assembly 3 and driver's section 27. A semicircular upper partition
plate 30 (acting as part of the outer frame defining the outermost region of
~1021~2
K6350
the driver's section 27)is fixedly mounted on the vertical partition plate 29
to extend along an outer contour of the swivel deck 2.
As shown in Figs. 2 and 4, a front danger plane Alis defined above a
predelei",ined level D over the ground G and at a predetermined distance
forward (outward) from the vertical partition plate 29. Further, as shown
in Fig. 4, a side danger plane A2is defined at a predetermined distance
rightward (outward) from a side surface of the vertical partition plate 29
opposed to the boom assembly 3. These danger planes Al and A2 are set
up by the control unit 19.
o The bucket 6 is connected to a distal end of the arm 5 through a bucket
pin 6a. As shown in Fig. 2, the front danger plane Alis defined such that,
when the bucket 6 is brought closest to the driver's section 27 with the
bucket pin 6a lying on the front danger plane Al, a tip end of the bucket 6
is on a locus El having a predetermined di~t~nce from the vertical partition
plate 29. As shown in Fig. 4, the side danger plane A2is defined such
that, when the bucket 6 is brought closest to the driver's section 27 with
the bucket pin 6a lying on the side danger plane A2, a side surface of the
bucket 6 is on a locus E2 having a predetermined distance from the vertical
partition plate 29. Further, caution planes Cl and C2 are defined, each at
a predete"nilled distance forward or rightward from the front or side danger
plane Al or A2. Spaces between the caution planes Cl and C2 and front
and side danger planes Al and A2 are set up by the control unit 19 as front
and side danger zones Bl and B2, respectively.
The backhoe may engage in an operation to excavate the ground G
with the boom assembly 3 disposed generally below the predetermined
level D. In this case, there is a limitation to movement of the boom
assembly 3 toward the running device 1. This mechanical operating
16 2 K6350
limitation of the boom assembly 3 itself is determined in advance. A
locus described by the bucket pin 6a when the boom assembly 3 is operated
in the above limit condition is also computed in advance. As shown in
Fig. 2, a boundary plane F is defined below the predetermined level D,
5 which is also set up by the control unit 19. The boundary plane F has a
small margin (outward) with respect to the locus of the bucket pin 6a in
the limit condition, and is smoothly continuous with the front danger plane
Al. When the bucket 6 is brought closest to the running device 1 with the
bucket pin 6a Iying on the boundary plane F, the tip end of the bucket 6 is
o on a locus E3.
The above front and side danger planes Al and A2, front and side
danger zones B 1 and B2 and boundary plane F are set up in relation to the
swivel deck 2. Thus, these planes and zones are movable with the swivel
deck 2 in swiveling movement.
Controls of the boom assembly 3 with respect to the front and side
danger planes Al and A2 and front and side danger zones Bl and B2 will
be described next with reference to the flowchart shown in Fig. 6.
At step Sl, the control unit 19 shown in Fig. 5 constantly computes
positions of the bucket pin 6a from a vertical angle of the boom 4 (first
20 boom portion 4a), a horizontal angle of the second boom portion 4b and a
fore and aft angle of the arm 5 based on the signals inputted from the
potentiometers 36-38, and from lengths of the first boom portion 4a, second
boom portion 4b and arm 5.
At step S2, the control unit 19 checks whether the bucket pin 6a is
25 above the predetermined level D or not. If the bucket pin 6a is at or above
the predetermined level D, the operation proceeds to step S3. If the bucket
pin 6a is below the predetermined level D, the operation proceeds to step
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21 0 2 ~ 6 2 K6350
S8.
At step S3, the control unit 19 checks whether the bucket pin 6a is
inside the front or side danger zone Bl or B2. If the bucket pin 6a is
outside the danger zones Bl and B2, the hydraulic cylinders 11, 12 and 7
are operable in a normal way, at the rates corresponding to operation of
the right and left control levers 9 and 10 and control pedal 26. Step S4 is
execllted when the bucket pin 6a is found, at step S3, to be inside the front
or side danger zone Bl or B2.
At step S4, the control unit 19 computes a current direction and
o velocity of movement of the bucket pin 6a as velocity vector Vl or V2, as
shown in Figs. 1 and 3, by dir~e~.~ ting detection values provided by the
potentiometers 36-38.
At step S5, the control unit 19 computes, from the current position and
velocity vector Vl or V2 of the bucket pin 6a, a distance Ll or L2 along
the velocity vector Vl or V2 from the current position of the bucket pin 6a
to the front or side danger plane Al or A2.
At step S6, the control unit 19 computes time Tl or T2 expected to be
taken for the bucket pin 6a to move from the current position to the front
or side danger plane Al or A2, based on the distance Ll or L2 and taking
into account a predetermined deceleration rate for the current velocity
vector Vl or V2. This deceleration rate means a negative acceleration
rate, which basically is set to a fixed value. In this way, the control unit
19 determines the current position, velocity vector Vl or V2, and estim~te~
time Tl or T2 nee~led to reach the front or side danger plane Al or A2.
At step S7, the pilot pressures of the pilot valves 31a, 31b, 32a, 32b,
35a and 35b are lowered to reduce the opening degrees of control valves
21, 22 and 25. As a result, the hydraulic cylinders 11, 12 and 7 are slowed
2 ~ 0 2 1 ~ 2 K6350
down to equalize the time Tl or T2 substantially to a predetermined time
T(x). The predetermined time T(x) is time taken for the bucket pin 6a to
move from current position "x" to the danger plane Al or A2 in an ideal,
uniformly accelerated motion having a predetermined deceleration rate.
This predeleQ~ined time T(x) is set as a continuous function of a miniml-m
horizontal ~i~t~nce "x" of the bucket pin 6a to the front or side danger
plane Al or A2. Fig. 8 shows a typical example thereof. As seen from
Fig. 8, the predetermined time T(x) becomes progressively shorter toward
the front or side danger plane Al or A2. That is, the time consumed
o before the bucket pin 6a stops at the danger plane Al or A2 is adjusted
only on the basis of the horizontal distance "x" of the bucket pin 6a to the
danger plane Al or A2, regardless of the direction of movement of the
bucket pin 6a.
As shown in Fig. 3, the bucket pin 6a is at distance Ll to the front or
side danger plane Al or A2 when the bucket pin 6a has velocity vector
Vl, and at distance L2 when the bucket pin 6a has velocity vector V2.
Although di~t~nce Ll is shorter than distance L2, the predetermined time
T when the bucket pin 6a has velocity vector Vl has the same value as the
predetermined time T(x) when the bucket pin 6a has velocity vector V2.
Thus, the hydraulic cylinders 11, 12 and 7 are decelerated when the
bucket pin 6a is inside the front or side danger zone Bl or B2. This
control is based on the constant computation of the current position, velocity
vector Vl or V2, and estimated time Tl or T2 needed to reach the front or
side danger plane Al or A2. As a result, the bucket pin 6a reaches the
front or side danger plane Al or A2 after the predetermined time T(x)
whether the bucket pin 6a moves horizontally, obliquely upward or obliquely
downward from the current position.
~ ~ ~ 216 2 K6350
Conversely, the hydraulic cylinders 11, 12 and 7 are accelerated when
the boom assembly 3 is operated in a direction to move the bucket pin 6a
in the front or side danger zone Bl or B2 and away from the front or side
danger plane Al or A2. Once the bucket pin 6a is out of the danger zone
5 Bl or B2, the normal speed is restored.
If, at step S8 in Fig. 6, the operation is continued to move the bucket
pin 6a even slightly past the front or side danger plane Al or A2 toward
the driver's section 27, the next step S9 is e~ecute-1 to elimin~te the pilot
pressures of pilot valves 31a-32b, 35a and 35b for c-fl--sing the control
valves 21, 22 and 25 to stop the hydMulic cylinders 11, 12 and 7 of the
boom assembly 3. Thus, step S9 in Fig. 6 may be termed safety means.
The hydraulic cylinder 13 for actuating the bucket 6 is still operable when
the bucket pin 6a is on the front or side danger plane Al or A2. In this
condition, the boom assembly 3 may be opeMted in a way to cause the
15 bucket pin 6a to move at ultra-slow speed along the danger plane Al or
A2.
As described above, the front and side danger zones Bl and B2 are
defined above the predetermined level D shown in Fig. 2. Such front and
side danger zones are not defined below the predetermined level D. Thus,
20 when the bucket pin 6a is below the predetermined level D, the operation
jumps from step S2 to step S8. In this case, the hydMulic cylinders 11, 12
and 7 of the boom assembly 3 are operated at speeds based on operation of
the right and left control levers 9 and 10 and control pedal 26 until the
bucket pin 6a reaches the boundary plane F. If the operation is continued
25 to move the bucket pin 6a even slightly past the boundary plane F toward
the running device 1, the pilot pressures of pilot valves 31a-32b, 35a and
35b are eliminated for causing the control valves 21, 22 and 25 to stop the
-13-
~1~ 216 ~ K6350
hydraulic cylinders 11, 12 and 7 of the boom ~eemhly 3.
The hydraulic cylinder 13 for actuating the bucket 6 is still operable
when the bucket pin 6a is on the boundary plane F, to cause the bucket pin
6a to move along the boundary plane F. Thus, after the bucket 6 scoops
soil from the ground G adjacent the running device 1, the bucket 6 may be
raised along the boundary plane F. With this movement, the bucket pin 6a
moves smoothly from the boundary plane F to the front danger plane A1,
and enters the front danger _one B1.
(Second Embo(lim~nt)
o Fig. 9 shows a flowchart of boom ~semhly controls in this embodiment.
As distinct from the prece-lin~ embodiment, this embodiment basically
employs, instead of the predeleQnilled time T(x), a velocity V(x) for re~li7ing
the predetermined time T(x). The hydraulic cylinders 11,'12 and 7 are
decelerated when the bucket pin 6a is in the danger _one B1 or B2, to
equali_e an actual reduced velocity to the predeten.~ ed velocity V(x).
That is, in the preceding embodiment, a position and direction and
velocity of movement of the bucket pin 6a are computed at steps S4 and
S5. The predetermined time needed for the bucket pin 6a to move in an
ideal, uniformly accelerated motion and stop at the danger plane A1 is
given as a function of a horizontal distance of the bucket pin 6a to the
f~nt danger plane A1. The hydraulic cylinders 11, 12 and 7 are decelerated
so that the time the bucket pin 6a is expected to consume in moving from
the current instantaneous position "x" to the danger plane A1 agree with
the predetermined time expressed as a function of a horizontal distance.
Instead of setting the stopping time T(x) based on the ideal, uniformly
accelerated motion as in the prece~in~ embodiment, the second embodiment
employs an ideal velocity V(x) of the bucket pin 6a inside the danger zone
-14-
2 ~ fi ~
to realize a predetermined, ideal, uniformly accelerated motion. In other
words, assumin~ an ideal motion by which the bucket pin 6a moves
hori70nt~11y at a predetermined velocity into the danger zone Bl having a
width (hori_ontal ~list~nce) defined by the caution plane Cl and danger
plane Al, moves at a unlro~ eceleration through the danger zone Bl
and stops at the danger plane Al, a velocity of the bucket pin 6a for
re~li7in~ an ideal motion in a given position "x" within the danger zone
Bl is ~e~ermine~ by a horizontal di~tance "x" of the bucket pin 6a from
the danger plane Al. Thus, this embodiment sets a dec~lerated motion of
10 W i~olm nC~lPration having an ideal initial velocity of the bucket pin 6a
as noted above. The hydraulic cylinders ll, 12 and 7 are operated to
approxim~te the decelerated motion of the bucket pin 6a to the above
ideal, uniformly accelerated motion when the pin 6a moving at varied
velocities and in varied directions enters the danger zone Bl and advances
lowa~ the danger plane Al.
The bucket pin 6a enters the danger zone Bl with a .n~x;.nlJ.n degree
of freedom at 180 degrees to the caution plane Cl in side view and at 180
degrees thereto in plan view. It is therefore necessary to compute a
con-po!-e.-t Vx in the direction of x-axis of the velocity of the bucket pin
20 6a in order to check with the ideal velocity. The x-axis is set in relation to
the swivel deck 2, and is movable with the swivel deck 2 in swiveling
movement.
Thus, at step S6 in this embo liment, the x-axis component Vx of the
moving velocity V of the bucket pin 6a is derived from the values computed
at steps S4 and S5.
Next, at step S7, the hydraulic cylinders l l, 12 and 7 are decelerated to
e llJali7e the x-axis velocity component Vx of the bucket pin 6a computed
-15-
B
2~ ~2~ 6~
above to the ideal velocity V(x). This is carried out every unit time ~ t
until the bucket pin 6a ~clles the danger plane Al.
Needless to say, the closer t-he bucket pin 6a moves to the danger plane
Al, the lower becomes the pre~ete~mine~ velocity V(x). The velocity of
the bucket pin 6a is adjusted only on the basis of a ~i~t~nce in the direction
of x-axis (ho~,~n~l and min,lnum) to the danger plane Al, regardless of
the direction of movement of the bucket pin 6a.
The control unit 19 has decelerating means to effect the greater
~eceleration of hydraulic cylinders 11, 12 and 7, the closer the bucket pin
o 6a in the danger zone Bl moves to the front danger plane Al.
When the bucket pin 6a is in the danger zone B2 also, the hydraulic
cylinders 11, 12 and 7 are ~çcelerated to subs~ lly equalize a velocity
com~llent Vy in y-a~s direction of the bucket pin 6a to an ideal, ul~iro~ ly
accelerated motion set as above. Again, the y-axis is set in relation to the
swivel deck 2, and is movable ~nth the s~vivel deck 2 in swivelirlg n~o~el~ent.
(Third Embo~imp~nt)
Fig. 10 sho~vs a flowel~l of boom ~sç .-bly cont~ls in this embodimqnt.
This embo~liment b~ lly is the same as the first embodiment up to step
S5 in the flo~.~clla,l, with the following steps S6 and S7 employed in this
20 çmhor1imP.nt,
At step S6, the following operation is carried out to cletçQnine whether
the left term is larger than zero or not:
-x+ ~r(sEr~, o
where x is a tiict~nce of the bucket pin along a direction of nlo~telllent
to the danger plane Al or A2, x is an absolute value of an in~t~nt~neous
velocity vector of the bucket pin, and T(SET) is set time required for a set
-16-
~ ~ ~ 21 ~ 2 K6350
stop. Generally, the set time T(SET) is 0.5 to 0.6 seconds. When the left
term in the above expression is larger than zero, it is considered possible
that, if the motion of the bucket pin 6a having the velocity and direction of
the instant continues for the set time T(SET), the bucket pin 6a moves
5 inwardly of the danger plane A1 or A2. Then, the next step S7 is executed.
At step S7, deceleration of the hydraulic cylinders 11, 12 and 7 is
started, simultaneously with the decision made at step S6, to control the
boom assembly 3.
If, at step S6, the above e~pfession is not satisfied, i.e. if the left term in
10 the above expression is found smaller than zero, it is considered that the
bucket pin 6a will not move inwardly of the danger plane A1 or A2 even if
the motion of the bucket pin 6a having the velocity and direction of the
instant continues for the set time T(SET). Then, the hydraulic cylinders
11, 12 and 7 are not decelerated but the bucket 6 is allowed to m~int~in
15 the motion of the instant although the bucket pin 6a is inside the danger
zone B1 or B2.
The operation of step S6 is repeated the next in~t~nt, i.e. upon lapse of
~ t seconds. If the above expression is satisfied at this time, the hydraulic
cylinders 11, 12 and 7 are decelerated imm~di~tely. In sum, though the
20 bucket pin 6a is inside the danger zone B1 or B2, the boom assembly 3
may continue to operate ~vithout being decelerated until the above expression
is satisfied.
Thus, whether the bucket pin 6a has velocity vector V1 or velocity
vector V2 as shown in Fig. 3, the bucket 6 is decelerated only when the
25 bucket pin 6a with either velocity is considered to move past the danger
plane upon lapse of set time T(SET) seconds. Once the deceleration
control is initiated, whether the bucket pin 6a has velocity vector V1 or
~10 21 & 2 K6350
V2, the bucket pin 6a stops subst~nti~lly in the set time T(SET) seconds.
Consequently, even when the bucket pin 6a inside the danger zone Bl or
B2 has a large angle to the danger plane Al or A2, the bucket pin 6a will
not move for an excessively long time before stopping. The set time
5 T(SET) may have a value best suited to the operator.
(Fourth Emb~iment)
In the first to third embodiments described above, the front and side
da-nger plane Al and A2 are deleQ~ined with reference to a position of the
bucket pin 6a as shown in Fig. 2. Alternatively, a potentiometer (not
o shown) may be installed adjacent the bucket pin 6a to enable the control
unit 19 to constantly compute positions of the tip end of the bucket 6. In
this case, the loci Cl and C2 shown in Figs. 2 and 4 define the danger
planes according to the present invention.
In the preceding embodiments, the potentiometers 36-38 are used to
15 determine the position and velocity vector Vl or V2 of the bucket pin 6a.
These potentiometers 36-38 may be used exclusively for detecting a position
of the bucket pin 6a, with velocity vector Vl or V2 detected by means of
other sensors.
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