Method for carrying out automatic surface finishing work with electro-hydraulic excavator vehicle

A method for carrying out a surface finishing work with an electronically controlled hydraulic excavator is disclosed. The present invention includes the steps of: selecting an automatic surface finishing work, and inputting a desired work angle (S1); detecting the current positions of the respective attachment (S32); deciding the bucket maintaining angle relative to the horizontal plane (S3); correcting the work angle relative to the equipment inclination (S4); judging as to whether the control lever for the dipper stick is manipulated by the operator (S7); judging as to whether or not there is a swinging operation by the operator (S9); correcting the swinging angle and the inclination angle when carrying out the swinging operation (S10); compensating the departure amount of the bucket end from the initially inputted work plane during the swinging (S11); calculating the linear velocity of the bucket end L which is proportionate to the actuation of the control lever for the dipper stick (S12); deciding a velocity for satisfying the positions of the cylinders corresponding to the intended angles of the bucket, the dipper stick and the boom (S15); making corrections for feasible velocities calculating the target velocities of the respective cylinders for arriving to the target positions (S17); correcting the velocities of the cylinders compensating the velocity of the cylinders and the fluid discharge amount of the pump (S19); and terminating the operation after the end of the work (S21).

BACKGROUND OF THE INVENTION 
1. Field of the invention 
The present invention relates to a method for carrying out an automatic 
surface finishing work with an electro-hydraulic excavator vehicle, in 
which the operator can carry out the generally most difficult surface 
finishing work in an easy manner with an electro-hydraulic excavator 
vehicle. 
2. Description of the prior art 
Electro-hydraulic excavator vehicles have complicated structures including 
various sensors, electronic proportional valves, and micro-processors. In 
this context, there appeared a need for an excavator vehicle in which a 
non-skilled person can carry out the operation in an easy and speedy 
manner. 
In the surface finishing work with a conventional excavator vehicle, the 
operator has to manipulate three control levers manually, and therefore, 
an accurate manipulation of the control levers is very difficult. 
Particularly, if the excavator vehicle is inclined, it is very difficult to 
attain the intended slope. 
Particularly, in the case where the surface finishing work is carried out 
while performing swinging, that is, in the case where the surface 
finishing work is carried out by manipulating four control levers, the 
operation becomes a highly difficult task. 
In the conventional auto surface finishing work with prior art 
electro-hydraulic excavator vehicles, sensors are installed only on the 
three pivot points of the boom, the dipper stick and the bucket, and a 
predetermined straight line is tracked, thereby carrying out the surface 
finishing work. 
In conventional automatic surface finishing work in which only a straight 
line is traced, running has to be made each time when work is carried out. 
If the slope of the ground is not the same after the running, the work 
surface can be made even with the already worked work surface only by 
arbitrarily varying the work angle. Therefore, the operator experiences a 
feeling of difficulty. 
SUMMARY OF THE INVENTION 
On the other hand, in the present invention, even if a swinging is 
additionally carried out, a departure is not made from the pre-set work 
plane. For this purpose, a swinging sensor and a slope sensor are 
additionally installed, so that the boom, the bucket and the dipper stick 
can be automatically controlled, thereby improving the operation 
efficiency. 
Under this condition, swinging is not made by tracking along a straight 
line but instead by tracking a plane, and therefore, surface finishing 
work can be carried out in an easy manner on any sloped surface. 
Therefore, in the present invention, the three attachments for the boom, 
the bucket and the dipper stick are driven by using only a single control 
lever for the dipper stick. Under this condition, when swinging is carried 
out, the end of the bucket geometrically departs from the plane. 
Thus if the control lever for the dipper stick is manipulated 
simultaneously with swinging, then the surface finishing work is done 
along the pre-set work plane, while if a swinging is made, a departure is 
made from the work plane. 
Therefore, a smooth returning has to be made by manipulating the control 
lever for the dipper stick, and the surface finishing work has to be 
carried out again. 
Thus the three attachments are driven in such a manner that a movement is 
made along a straight line so as to be fit to the work angle, and a 
control is made so that the bucket is maintained at a certain angle 
relative to the horizontal plane, thereby carrying out the surface 
finishing work. 
The present invention is intended to overcome the above described problems 
of the conventional techniques. 
Therefore it is the object of the present invention to provide a method for 
carrying out an automatic surface finishing work with an electronically 
controlled hydraulic excavator, in which the work angle can be varied 
during the swinging of the excavator for continuing the surface finishing 
work on the work plane. 
In achieving the above object, the method for carrying out a surface 
finishing work with an electronically controlled hydraulic excavator 
according to the present invention, includes the steps of: selecting an 
automatic surface finishing work on a key pad 5, and inputting a desired 
work angle .theta.w into the main processor 10 by the operator (S1); 
detecting and reading the current signal values of the angles of a boom 
100, dipper stick 110 and a bucket 120, the turning angle of the swinging, 
and the slope of the upper portion of excavator vehicle, through position 
sensors (S2); deciding the bucket maintaining angle relative to the 
horizontal plane based on the read signal values (S3); correcting the work 
angle .tau. to make the inputted work angle (based on the inclination of 
the equipment) fit to the absolute horizontal plane (S4); deciding the 
initial positions of the bucket end L and the bucket joint J with respect 
to a rectangular coordinate system whose origin is point A and, an upper 
rotary portion of the excavator vehicle (S5); deciding the initial 
position of the bucket end L with respect to a rectangular coordinate 
system whose origin is point O (S6); judging as to whether or not the 
control lever for the dipper stick as an arbitrary control lever is 
manipulated if the control lever has not been manipulated carrying out 
step S20 (S7); deciding the current position of the bucket joint J with 
respect to the rectangular coordinate having an origin at point A, after 
manipulation of the control lever for the dipper stick (S8); judging as to 
whether there is a swinging operation by the operator, and then, carrying 
out step S12 if there is none (S9); reading the swinging angle and the 
inclination angle of the upper portion of the equipment to correct the 
work angle .tau. when carrying out the swinging operation (S31); 
calculating the departure amount h of the bucket end from the initially 
inputted work plane, when the buck end L departs from the work plane 
during the swinging (S11); calculating the linear velocity of the bucket 
end L which is proportionate to the actuation of the control lever for the 
dipper stick (S12); deciding the next position to which the pivot point of 
bucket J is to be positioned with respect to the rectangular coordinate 
system having an origin at point O (S13); deciding a boom angle .theta.bm, 
a dipper stick angle .theta.ds for the position of bucket pivot point J 
and a bucket angle .theta.bk for maintaining the initial bucket angle with 
respect to horizontal line, which correspond to the positional values of 
step S13 (S14); deciding a speed for satisfying positions d.sub.bm, 
d.sub.ds and d.sub.bk of the cylinders of the respective attachment 
corresponding to the intended angles of the bucket 120, the dipper stick 
110 and the boom 100 calculated at step S14 (S15); making corrections for 
possible velocities without varying the velocity ratio of the respective 
cylinders within the range of the dischargeable fluid amount from the pump 
currently, and then, re-setting the intended positions d.sub.bm, d.sub.ds, 
and d.sub.bk of the cylinders (S16); calculating the target velocities of 
the respective cylinders for positioning at the target positions by 
utilizing the position values d.sub.bm, d.sub.ds, and d.sub.bk by a 
position control section 130 (S17); correcting the velocities of the 
cylinders and the current amount of the fluid dischargeable by the pump, 
while maintaining the target velocity ratio of the respective cylinders 
(S18); compensating the velocity based on the position values obtained 
based on the current work status which is measured by a position sensor 15 
and based on the discharging amount of the pump (S19); converting the 
digital signals of the compensated velocity signals into analog signals by 
means of first and second D/A converters 35 and 40 for outputting voltages 
to a first amplifier 36 and to a second amplifier 41 for a main control 
valve so as to output currents through first and second electronic 
proportional valves 50 and 45, and activating the pumps with the currents 
to drive respective hydraulic cylinder or motor 90, 91, 92, 93, 94 and 95 
within a main control valve 80 (S20); and terminating the operation after 
an end of the work if the operator has inputted a releasing signal for the 
surface finishing work, and returning to step S7 if the releasing signal 
has not been inputted (S21).

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a block diagram showing the constitution of the hydraulic control 
system according to the present invention. 
The constitution and operation of the system of FIG. 1 will be described. 
First, the operator presses an "automatic surface finishing" selection 
button of a key pad 5, and inputs a work angle which is suitable to the 
work environment. Then the automatic surface finishing function and the 
work angle are transmitted through a communication port to a main 
processor 10 which is the controller. 
When the work angle is transmitted, the main processor 10 reads respective 
position sensors 15 to detect the position and the inclination of the 
equipment for the current boom, dipper stick, bucket and swing through a 
system bus. The analogue signals thus read are transmitted through a 
system bus to a first A/D converter 20 which then converts the signals 
into digital signals. 
An equation for the work plane is set up based on the work angle and the 
initial position of the bucket end of the excavator utilizing the position 
signals which were read in the above described manner. Then a control 
lever for the dipper is manipulated by the operator. Then the analog 
signals which correspond to the manipulations are converted into digital 
signals by a second A/D converter 30, so that the main processor 10 can 
determine the linear velocity of the bucket end in accordance with the 
manipulation amount. 
Proportionately to the linear velocity, the next point of a pivot point of 
bucket J is determined. Then if the control lever 25 is manipulated, the 
swing and inclination angle are read again to calculate the deviation of 
the bucket end from the initially set work plane. Thus the work angle is 
re-determined to determine the position of the point J, so that the bucket 
end would not deviate from the work plane. 
In order to reach the position of the point J, the positions (angles) of 
the cylinders of the boom and dipper stick are determined. 
The position of the bucket makes it possible to calculate the bucket angle 
relative to the horizontal plane at the time of the starting of the work. 
The calculated angles for the boom, the dipper stick and the bucket are 
converted into positions of the cylinders, and, based on these position 
values, target velocity is formed. For this purpose, the required fluid 
amounts are discharged from an auxiliary pump 55, a first pump 60 and a 
second pump 65. 
The main processor 10 outputs command digital signals of the fluid amount 
to be discharged for the respective attachments, and these digital signals 
are converted by a first D/A converter 35 and a second D/A converter 40 
which output them in the form of analog signals. Then voltages are 
supplied to a first amplifier 36 for the second pump 65, the first pump 60 
and the auxiliary pump 55 (which are driven by an engine 70), and to a 
second amplifier 41 which is for a main control valve 80. 
The outputted voltages are converted by the first amplifier 36 into 
currents. Thus the currents which are outputted from the first amplifier 
36 are supplied to a first electronic proportional valve 50 for a pump, 
while the current signals which are outputted from the second amplifier 41 
are supplied to a second electronic proportional valve 45 for the main 
control valve 80. 
Under this condition, the first electronic proportional valve 50 produces a 
pilot pressure to adjust a swash plate of the first pump 60 or the second 
pump 65, so that the desired discharge amount of the fluid would be sent 
to the main control valve 80. 
The second electronic proportional valve 45 for the main control valve 80 
also produces a pilot pressure. Thus, there are adjusted the respective 
strokes of the spools such as a rightward running motor control spool, a 
leftward running motor control spool, a swinging motor control spool, an 
arm control spool, a bucket control spool, and a boom control spool within 
the main control valve 80. Thus, the hydraulic fluids from the pumps 55, 
60 and 65 are distributed to a boom cylinder 90, an arm cylinder 91, a 
bucket cylinder 92, a swinging motor 93, a leftward running motor 94 and a 
rightward running motor 95, thereby driving them. 
The automatic surface finishing work with an electronically controlled 
hydraulic excavator based on the system of FIG. 1 will be described 
referring to the flow chart of FIG. 2. 
For making descriptions referring to FIG. 2, referring will be made to the 
side view of the excavator of FIG. 3, to the work plane setting 
illustration of FIG. 4, and to work angle compensating illustration of 
FIG. 5 during a swinging. 
First, at step 1 (S1) of FIG. 2, the operator selects automatic surface 
finishing work, and inputs the desired work angle .theta.w. Then, reading 
is made of the signal values for a current angle .theta.bm of the pivot 
point of the boom 100, a current angle .theta.ds of the dipper stick 110, 
a current angle .theta.bk of the bucket 120, a turning angle .theta.sw of 
the swinging, an inclination angle .theta.p (pitching) of the upper 
portion of the equipment, and a rolling angle .theta.r of FIG. 3. At step 
2 (S2), the positions of the respective attachments are detected through 
the respective position sensors 15. 
At step 3 (S3), based on the position angle, a bucket maintaining angle 
.PHI. (=.theta.bm+.theta.ds+.theta.bk) relative to the horizontal surface 
is decided. Then, at step 4 (S4), the current status of the equipment is 
analyzed, and the operator corrects the work angle .tau. in such a manner 
that the work angle inputted by the operator would be suitable for the 
absolute horizontal surface relative to the equipment inclination. For 
this purpose, the following formula is utilized. 
EQU .tau.=a tan (tan .theta.w cos .DELTA..theta.sw(cos .theta.r+sin .theta.r 
tan (.theta.r-a tan (tan .theta.w sin .DELTA..theta.sw)))) 
At step 5 (S5), initial positions of the bucket end L and the pivot point 
of bucket J which is the connection point between the dipper stick 110 and 
the bucket 120 are determined on a rectangular coordinate which has an 
original point A at the point where the upper rotary portion 135 and the 
boom 100 of FIG. 3 are connected together. 
EQU Jx30=lbm cos (.theta.bm+.theta.p)+lds cos (.theta.bm+.theta.ds+.theta.p) 
EQU Jy30=lbm sin (.theta.bm+.theta.p)+lds sin (.theta.bm+.theta.ds+.theta.p) 
EQU Lx30=Jx30+lbk cos (.theta.bm+.theta.ds+.theta.bk+.theta.p) 
EQU Ly30=Jy30+lbk sin (.theta.bm+.theta.ds+.theta.bk+.theta.p) 
In the above formulas, lbm, lds and lbk indicate respectively the lengths 
of boom, dipper stick and bucket. 
At step 6 (S6), an initial position (XO, YO, ZO) of the bucket end is 
determined on a coordinate which has an original point O which is the 
contact point between the plane and the bottom center of the wheel of FIG. 
3. 
EQU XO=cs cp(lx+LEN.sub.-- AN)-cs sp cr(ly+LEN.sub.-- NO)+ss sr(ly+LEN.sub.-- 
NO) 
EQU YO=sp(lx+LEN.sub.-- AN)+cp cr(ly+LEN.sub.-- NO) 
EQU ZO=-ss cp(lx+LEN.sub.-- AN)+ss sp cr(Ly.sub.-- LEN.sub.-- NO)cs 
sr(ly+LEN.sub.-- NO) 
In the above formulas, the new symbols are defined respectively as follows. 
EQU lx=lbm cos (.theta.bm)+lds cos (.theta.bm+.theta.ds)+lbk cos 
(.theta.bm+.theta.ds+.theta.bk), 
EQU cp=cos (.theta.p), sp=sin (.theta.p), cr=cos (.theta.r), 
EQU sr=sin (.theta.r), cs=cos (.theta.sw), ss=sin (.theta.sw). 
Further, LEN.sub.-- AN indicates the straight length of the distance 
between the point A and N of FIG. 3. 
At step 7 (S7), when the surface finishing work is carried out by driving 
the 3 attachments or 2 attachments of the boom, the dipper stick and the 
bucket, the main processor 10 makes a judgment as to whether the operator 
used the control lever 25 for the dipper stick as an arbitrary one of the 
control levers, or used other executing means. If not used it, a next step 
20 (S20) is carried out. 
If it is found a step 7 (S7) that the operator used the control lever 25 
for the dipper stick or other executing means, then not the initial value 
but the current value of the pivot point of bucket J is calculated. That 
is, a calculation is made as to the current value of the bucket joint J on 
a rectangular coordinate which has the point A of FIG. 3 as the original 
point, at step 8 (S8). 
EQU Jx3=lbm cos (.theta.bm+.theta.p)+lds cos (.theta.bm+.theta.ds+.theta.p) 
EQU Jy3=lbm sin (.theta.bm+.theta.p)+lds sin (.theta.bm+.theta.ds+.theta.p) 
At step 9 (S9), the main processor 10 makes a judgment as to whether the 
operator has made a swinging operation. If there has been no swinging 
operation, a next step S12 is carried out. 
If there has been a swinging operation at step S9, then, at step 10 (S10), 
the swinging angle and the inclination angle of the upper portion of the 
equipment are read, and then, the work angle .tau. is modified. 
EQU .tau.=a tan (tan .theta.w cos .DELTA..theta.sw(cos .theta.r+sin .theta.r 
tan (.theta.r-a tan (tan .theta.w sin .DELTA..theta.sw)))) 
At step 11 (S11), when the bucket end L departs from the work plane as a 
result of the swinging, the departure amount of the bucket end is 
calculated and compensated, so that the bucket end L would not be departed 
from the initially set work plane. 
For this purpose, the initial position (Jx30, Jy30) of the bucket joint are 
re-set based on the following formula. 
EQU -sin (.theta.w) cos (.theta.swo) X+cos (.theta.w) Y+sin (.theta.w) sin 
(.theta.swo) Z=-sin (.theta.w) cos (.theta.swo) XO+cos (.theta.w) YO+sin 
(.theta.w) sin (.theta.swo) ZO 
When the swinging operation is begun, the position of the bucket end L 
departs from the work plane, and therefore, a compensation has to be 
carried out as much as the departure amount. 
Based on the method of step 8 (S8), the position (X, Y, Z) of the bucket 
end L is determined in a rectangular coordinate having a point O of FIG. 3 
as the origin point. At this position, the amount h of the departure from 
the work plane is calculated. 
##EQU1## 
In the above, .theta.swo indicates the initial swinging position, and other 
symbols are as follows. 
EQU sga=sin (.theta.w), cga=cos (.theta.w), Tga=tan (.theta.w), 
EQU cgs=cos (.theta.swo), sgs=sin (.theta.swo). 
The initial positions of the bucket end and the pivot point of bucket are 
shifted as much as the departure amount. 
At step 12 (S12), a calculation is made on a linear velocity J of the pivot 
point of bucket J (or the bucket end) which is proportionate to the 
operation amount of the control lever 25 for the dipper stick of FIG. 1. 
At step 13 (S13), a determination is made of the position to which the 
pivot point of bucket J is destined on a rectangular coordinate having the 
point A of FIG. 3 as the origin point. 
EQU Jx3=Jx3+J cos (.tau.)ts 
EQU Jy3=tan (.tau.) (Jx3-Jx30)+Jy30 
At step 14 (S14), correspondingly with the values of Jx3 and Jy3, 
calculations are made on the boom angle .theta.bm, the dipper stick angle 
.theta.ds and the buck angle .theta.bk for maintaining the initial bucket 
angle. 
EQU .theta.bm=a tan (Jy3/Jx3)+a cos ((lbm.sup.2 -lds.sup.2 +Jx3.sup.2 
+Jy3.sup.2)/(2 lbm.sqroot.(Jx3.sup.2 +Jy3.sup.2).sup.2))-.theta.p 
EQU .theta.ds=-a cos (Jx3.sup.2 +Jy3.sup.2 -lbm.sup.2 -lds.sup.2)/(2 lbm.lds)) 
.theta.bk=.PHI.-.theta.bm-.theta.ds 
At step 15 (S15), cylinder positions of the respective attachments are 
calculated based on the target angles .theta.bm, .theta.bk and .theta.ds 
of the boom 100, the bucket 120 and the dipper stick 110 which have been 
calculated at step 14 (S14). 
EQU d.sub.bm =(LEN.sub.-- AB).sup.2 +(LEN.sub.-- AC).sup.2 -2*LEN.sub.-- 
AB*LEN.sub.-- AC*cos (ANG.sub.-- CAE+ANG.sub.-- BAX3+.theta.bk)).sup.2 
EQU d.sub.ds =(LEN.sub.-- DE).sup.2 +(LEN.sub.-- EF).sup.2 -2*LEN.sub.-- 
DE*LEN.sub.-- EF*cos (ANG.sub.-- ALPH7-.theta.ds)).sup.2 
EQU d.sub.bk =((LEN.sub.-- GH).sup.2 +(LEN.sub.-- HI).sup.2 -2*LEN.sub.-- 
GH*LEN.sub.-- HI*cos (.phi.)).sup.2 
EQU .alpha.=.pi.-(.theta.bk+ANG.sub.-- LJK+ANG.sub.-- HJE) 
EQU c6=((LEN.sub.-- JK).sup.2 +(LEN.sub.-- HJ).sup.2 -2*LEN.sub.-- 
JK*LEN.sub.-- HJ*cos (.alpha.)).sup.2 
EQU .PHI.=a cos (c6).sup.2 +(LEN.sub.-- HI).sup.2 -(LEN.sub.-- IK).sup.2 
/(2*LEN.sub.-- HI*c6) 
EQU .beta.=a cos (LEN.sub.-- HJ).sup.2 +(c6).sup.2 -(LEN.sub.-- 
JK).sup.2)/(2*c6 LEN.sub.-- HJ)) 
EQU .phi.=ANG.sub.-- GHJ-.PHI.-.beta. 
In the above, LEN.sub.-- AB indicates the distance between the joint A and 
the joint B, and ANG.sub.-- ABC indicates the angle between the line AB 
and the line BC. Further, ANG.sub.-- ALPHA7 is defined as follows. 
EQU ANG.sub.-- ALPHA7=.pi.-ANG.sub.-- JEF-ANG.sub.-- CED-ANG.sub.-- BEC 
Then the cylinder velocities, which can satisfy the cylinder positions 
d.sub.bm, d.sub.bk and d.sub.ds for the boom, the bucket, and the dipper 
stick, are calculated. 
At step 16 (S16), the velocities of the respective cylinders are modified 
without varying the velocity ratio between the cylinders within the range 
of the discharge fluid amount of the current pump. Then, the target 
cylinder positions d.sub.bm, d.sub.ds and d.sub.bk are re-determined 
correspondingly with the boom angle .theta.bm, the dipper stick angle 
.theta.ds, and the bucket angle .theta.bk for the cylinders. 
At step 17 (S17), by utilizing the position values d.sub.bm, d.sub.ds and 
d.sub.bk, the controller 130 calculates the target velocities of the 
respective cylinders for moving to the target positions. 
At step 18 (S18), while maintaining the velocity ratio between the 
respective cylinders and the amount of the fluid dischargeable by the 
pumps 55, 60 and 65 are corrected. 
At step 19 (S19), the position values, which correspond to the current 
work, and are detected by the position sensor 15 and are compensated, 
while the fluid amounts dischargeable by the pumps are also compensated. 
At step 20 (S20), the compensated values are the commanded values of the 
main control valve 80 commanding that the required amounts of fluid should 
be discharged for the respective cylinders. These compensated velocity 
values of a digital form are converted into analog signals by the first 
and second D/A converters 35 and 40. 
The voltage signals of the converted analog signals are supplied to the 
first and second amplifiers 36 and 41 to be outputted therefrom in the 
form of current signals. These current signals are supplied to the first 
electronic proportional valve 50 and to the second electronic proportional 
valve 45 for the main control valve. 
Thus, the first electronic proportional valve 50 generates a pilot pressure 
for adjusting the swash plate to send the required amount of fluid to the 
main control valve 80. Then the spool strokes for the respective 
attachments (boom, arm, bucket, swinging motor, leftward running motor and 
rightward running motor) are adjusted by the main control valve 80, so 
that the fluid from the pumps would be distributed to the respective 
cylinders. 
At step 21 (S21), a judgment is made as to whether or not the operator has 
inputted a signal for release of the automatic surface finishing work. If 
a release is inputted, the operation is terminated (exit), while if not 
inputted, then the system returns to step 7 (S7) (go to S7). 
According to the present invention as described above, the automatic 
surface finishing work with an excavator vehicle is rendered easy, and the 
work efficiency is improved. Further, non-skilled persons can carry out 
the surface finishing work, and therefore, labor cost is saved. Further, 
the surface finishing work is carried out in an automatic manner, and 
therefore, the work is done precisely.