U.S. patent application number 15/108651 was filed with the patent office on 2017-07-20 for construction machine, hybrid hydraulic excavator, and output torque control method for motor generator.
The applicant listed for this patent is KOMATSU LTD.. Invention is credited to Tomotaka Imai, Tsubasa Ohira, Masaru Shizume, Hiroaki Take.
Application Number | 20170204589 15/108651 |
Document ID | / |
Family ID | 56091837 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170204589 |
Kind Code |
A1 |
Ohira; Tsubasa ; et
al. |
July 20, 2017 |
Construction Machine, Hybrid Hydraulic Excavator, And Output Torque
Control Method For Motor Generator
Abstract
A construction machine includes a swing speed detection unit
that detects an actual swing speed of an upper structure, a lever
command speed calculation unit that calculates a lever command
speed based on an operation amount of a swing lever for swinging
the upper structure, a torque command value calculation unit that
calculates a torque command value based on a command speed based on
the calculated lever command speed, a command value output unit
that outputs a command torque to a rotary motor generator based on
the torque command value calculated by the torque command value
calculation unit and the swing speed detected by the swing speed
detection unit, and a command value output restriction unit that
restricts the output of the torque command value from the command
value output unit under predetermined conditions.
Inventors: |
Ohira; Tsubasa;
(Hiratsuka-shi, Kanagawa, JP) ; Imai; Tomotaka;
(Hiratsuka-shi, Kanagawa, JP) ; Take; Hiroaki;
(Hiratsuka-shi, Kanagawa, JP) ; Shizume; Masaru;
(Yokohama-shi, Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KOMATSU LTD. |
Minato-ku, Tokyo |
|
JP |
|
|
Family ID: |
56091837 |
Appl. No.: |
15/108651 |
Filed: |
January 20, 2016 |
PCT Filed: |
January 20, 2016 |
PCT NO: |
PCT/JP2016/051622 |
371 Date: |
June 28, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F 9/2075 20130101;
E02F 9/2095 20130101; E02F 9/123 20130101; E02F 3/32 20130101; E02F
9/2292 20130101; E02F 9/2296 20130101; E02F 3/425 20130101 |
International
Class: |
E02F 9/12 20060101
E02F009/12; E02F 3/32 20060101 E02F003/32 |
Claims
1. A construction machine comprising: an undercarriage; an upper
structure swingably provided to the undercarriage and driven by a
motor generator; working equipment provided to the upper structure;
a swing speed detection unit configured to detect an actual swing
speed of the upper structure; a lever command speed calculation
unit configured to calculate a lever command speed based on an
operation amount of a swing lever configured to swing the upper
structure; a torque command value calculation unit configured to
calculate a torque command value based on a command speed based on
the calculated lever command speed; a command value output unit
configured to output the torque command value to the motor
generator based on the torque command value calculated by the
torque command value calculation unit and the swing speed detected
by the swing speed detection unit; and a command value output
restriction unit configured to restrict the output of the torque
command value from the command value output unit when: the actual
rotation speed detected by the rotary speed detection unit is
smaller than a first threshold; a deviation between the lever
command speed calculated by the lever command speed calculation
unit and the actual swing speed detected by the swing speed
detection unit is greater than a second threshold; and the lever
command speed calculated by the lever command speed calculation
unit is smaller than a predetermined value.
2. The construction machine according to claim 1, wherein the
command value output restriction unit is configured to restrict the
output of the torque command value when the lever command speed
calculated by the lever command speed calculation unit is zero.
3. The construction machine according to claim 1, further
comprising: a jerk command speed calculation unit configured to
calculate a jerk command speed including a gradient for an
acceleration or deceleration of the upper structure based on the
lever command speed calculated by the lever command speed
calculation unit, wherein the command value output restriction unit
restricts the output of the torque command value from the command
value output unit when the jerk command speed calculated by the
jerk command speed calculation unit is smaller than a third
threshold.
4. The construction machine according to claim 3, further
comprising: a reaction-force control command speed calculation unit
configured to calculate a reaction-force control command speed
usable for a position control of the upper structure with reference
to a current position of the motor generator, wherein the command
value output restriction unit restricts the output of the torque
command value from the command value output restriction unit when
the reaction-force control command speed calculated by the
reaction-force control command speed calculation unit is smaller
than the jerk command speed calculated by the jerk command speed
calculation unit.
5. A hybrid hydraulic excavator comprising: an undercarriage; an
upper structure swingably provided to the undercarriage and driven
by a motor generator; and working equipment provided to the upper
structure, the working equipment comprising a boom swingably
provided to the upper structure, an arm swingably provided to the
boom, and a bucket swingably provided to the arm, wherein an
electric power is transferred between the motor generator and a
rechargeable battery or a generator motor, and the boom, the arm,
and the bucket are hydraulically driven, the hybrid hydraulic
excavator further comprising: a swing speed detection unit
configured to detect an actual swing speed of the upper structure;
a lever command speed calculation unit configured to calculate a
lever command speed based on an operation amount of a swing lever
configured to swing the upper structure; a torque command value
calculation unit configured to calculate a torque command value
based on a command speed based on the calculated lever command
speed; a command value output unit configured to output the torque
command value to the motor generator based on the torque command
value calculated by the torque command value calculation unit and
the swing speed detected by the swing speed detection unit; and a
command value output restriction unit configured to restrict the
output of the torque command value from the command value output
unit when: the actual rotation speed detected by the rotary speed
detection unit is smaller than a first threshold; a deviation
between the lever command speed calculated by the lever command
speed calculation unit and the actual swing speed detected by the
swing speed detection unit is greater than a second threshold; and
the lever command speed calculated by the lever command speed
calculation unit is smaller than a predetermined value.
6. An output torque control method for a motor generator performed
in a construction machine comprising: an undercarriage; an upper
structure swingably provided to the undercarriage and driven by the
motor generator; working equipment provided to the upper structure;
and a controller, the method comprising steps below performed by
the controller of the construction machine: detecting an actual
swing speed of the upper structure; calculating a lever command
speed based on an operation amount of a swing lever configured to
swing the upper structure; calculating a torque command value based
on the calculated lever command speed; outputting the torque
command value to the motor generator based on the calculated torque
command value and the detected actual swing speed of the upper
structure; and restricting the output of the torque command value
to the motor generator when: the detected actual swing speed is
smaller than a first threshold; a deviation between the calculated
lever command speed and the detected actual swing speed is greater
than a second threshold; and the calculated lever command speed is
smaller than a predetermined value.
Description
TECHNICAL FIELD
[0001] The present invention relates to a construction machine, a
hybrid hydraulic excavator, and an output torque control method for
a motor generator.
BACKGROUND ART
[0002] A hybrid electric rotary excavator including a motor
generator for driving an upper structure and a hydraulic actuator
for driving other working equipment and a carrier has been known
(see, for instance, Patent Literature 1).
[0003] Since the electric rotary excavator uses the motor generator
in order to swing the upper structure, the motion of the upper
structure is not affected by a lift operation of a boom and/or an
arm even when the upper structure is swung simultaneously with the
lift operation of the hydraulically driven boom and arm.
Accordingly, an energy loss in a control valve and the like can be
reduced as compared to an instance in which the upper structure is
hydraulically driven, so that energy efficiency can be
improved.
[0004] When the swing speed of such an electric rotary excavator is
to be controlled, a lever command speed is calculated based on a
lever signal of a swing lever. Then, the lever command speed is
compared with an actual speed to obtain a deviation, and a torque
command value is calculated based on the deviation to accelerate
and decelerate the swing motion of the electric rotary excavator
using a torque output corresponding to the torque command
value.
[0005] Specifically, a jerk command speed for providing the most
appropriate acceleration (jerk value) for the lever command speed
is calculated based on the lever signal of the swing lever. Then, a
feed-forward torque command value that reduces a constant speed
deviation of the swing speed with respect to the calculated jerk
command speed is calculated to control the swing speed (see, for
instance, Patent Literature 2).
CITATION LIST
Patent Literature(s)
[0006] Patent Literature 1 WO 2005/111322
[0007] Patent Literature 2 WO 2006/054581
SUMMARY OF THE INVENTION
Problem(s) to be Solved by the Invention
[0008] The electric rotary excavator occasionally performs
excavation work while a bucket is lateral-pressed to an excavation
wall. In such a case, it is necessary to operate the boom, the arm
and/or the bucket while the swing lever is operated.
[0009] At this time, though the swing lever is operated by an
operator, the upper structure itself receives a reaction force from
the excavation wall, so that the swing speed is kept at
substantially zero.
[0010] When the operator sets the swing lever in neutral in this
state, since the reaction force is larger than an output torque of
a swing motor, the upper structure is pushed back toward a side
opposite the excavation wall, thereby causing vibrations before the
upper structure stops.
[0011] An object of the invention is to provide a construction
machine, a hybrid hydraulic excavator and an output torque control
method for a motor generator capable of restraining vibrations when
the swing motion is stopped while a lateral-press excavation in
which a swing operation and a working equipment operation are
simultaneously conducted is performed.
Means for Solving the Problem(s)
[0012] A construction machine according to an aspect of the
invention includes:
[0013] an undercarriage;
[0014] an upper structure swingably provided to the undercarriage
and driven by a motor generator;
[0015] working equipment provided to the upper structure;
[0016] a rotation speed detection unit configured to detect an
actual swing speed of the upper structure;
[0017] a lever command speed calculation unit configured to
calculate a lever command speed based on an operation amount of a
swing lever configured to swing the upper structure;
[0018] a torque command value calculation unit that calculates a
torque command value based on a command speed based on the
calculated lever command speed;
[0019] a command value output unit configured to output the torque
command value to the motor generator based on the torque command
value calculated by the torque command value calculation unit and
the swing speed detected by the rotation speed detection unit;
and
[0020] a command value output restriction unit configured to
restrict the output of the torque command value from the command
value output unit when: the actual rotation speed detected by the
rotary speed detection unit is smaller than a first threshold; a
deviation between the lever command speed calculated by the lever
command speed calculation unit and the actual swing speed detected
by the rotation speed detection unit is greater than a second
threshold; and the lever command speed calculated by the lever
command speed calculation unit is smaller than a predetermined
value.
[0021] According to the above aspect of the invention, when the
actual swing speed of the upper structure is smaller than the first
threshold and the deviation between the lever command speed and the
actual swing speed is greater than the second threshold, the upper
structure is not swung irrespective of the operation on the swing
lever, and thus it can be judged that the construction machine is
in the lateral-press excavation work. Then, when it is found that
the lever command speed is smaller than the predetermined value, it
can be judged that an operator stops the lateral-press excavation
work. At this time, since the command value output restriction unit
restricts the output of the torque command value from the command
value output unit, the command value output unit is kept from
outputting a torque command value in the same direction as a
direction of a reaction force applied to the working equipment, so
that the generation of vibrations on the upper structure can be
prevented.
[0022] A hybrid hydraulic excavator according to another aspect of
the invention includes:
[0023] an undercarriage;
[0024] an upper structure swingably provided to the undercarriage
and driven by the motor generator; and
[0025] working equipment provided to the upper structure, the
working equipment comprising a boom swingably provided to the upper
structure, an arm swingably provided to the boom, and a bucket
swingably provided to the arm, where
[0026] an electric power is transferred between the motor generator
and a rechargeable battery or a generator motor, and
[0027] the boom, the arm, and the bucket are hydraulically driven.
The hybrid hydraulic excavator further includes:
[0028] a rotation speed detection unit configured to detect an
actual swing speed of the upper structure;
[0029] a lever command speed calculation unit configured to
calculate a lever command speed based on an operation amount of a
swing lever configured to swing the upper structure;
[0030] a torque command value calculation unit that calculates a
torque command value based on a command speed based on the
calculated lever command speed;
[0031] a command value output unit configured to output the torque
command value to the motor generator based on the torque command
value calculated by the torque command value calculation unit and
the swing speed detected by the rotation speed detection unit;
and
[0032] a command value output restriction unit configured to
restrict the output of the torque command value from the command
value output unit when: the actual rotation speed detected by the
rotary speed detection unit is smaller than a first threshold; a
deviation between the lever command speed calculated by the lever
command speed calculation unit and the actual swing speed detected
by the rotation speed detection unit is greater than a second
threshold; and the lever command speed calculated by the lever
command speed calculation unit is smaller than a predetermined
value.
[0033] According to this aspect of the invention, the same
effect(s) and advantage(s) as those of the above aspect of the
invention can be obtained.
[0034] An output torque control method for a motor generator
according to still another aspect of the invention is performed in
a construction machine including: an undercarriage; an upper
structure swingably provided to the undercarriage and driven by a
motor generator; working equipment provided to the upper structure;
and a controller. The method includes steps below performed by the
controller of the construction machine:
[0035] detecting an actual swing speed of the upper structure;
[0036] calculating a lever command speed based on an operation
amount of a swing lever configured to swing the upper
structure;
[0037] calculating a torque command value based on the calculated
lever command speed;
[0038] outputting the torque command value to the motor generator
based on the calculated torque command value and the detected
actual swing speed of the upper structure; and
[0039] restricting the output of the torque command value to the
motor generator when:
[0040] the detected actual swing speed is smaller than a first
threshold;
[0041] a deviation between the calculated lever command speed and
the detected actual swing speed is greater than a second threshold;
and
[0042] the calculated lever command speed is zero.
[0043] According to this aspect of the invention, the same
effect(s) and advantage(s) as those of the above aspect of the
invention can be obtained.
BRIEF DESCRIPTION OF DRAWING(S)
[0044] FIG. 1 is a perspective view showing a structure of a
construction machine according to an exemplary embodiment of the
invention.
[0045] FIG. 2 is a block diagram showing a structure of a drive
system of the construction machine according to the exemplary
embodiment.
[0046] FIG. 3 is a functional block diagram of a swing controller
according to the exemplary embodiment.
[0047] FIG. 4 is a graph for explaining a jerk command speed
calculation unit of the exemplary embodiment.
[0048] FIG. 5 is a flow chart for explaining a function of the
exemplary embodiment.
[0049] FIG. 6 is a perspective view for explaining an effect of the
exemplary embodiment.
[0050] FIG. 7 is a graph for explaining the effect of the exemplary
embodiment.
DESCRIPTION OF EMBODIMENT(S)
[0051] Exemplary embodiment(s) of the invention will be described
below with reference to the attached drawings.
[1] Overall Arrangement
[0052] FIG. 1 shows a working machine according to the exemplary
embodiment in a form of a hybrid electric rotary excavator 1. The
electric rotary excavator 1 includes an undercarriage 2, an upper
structure 3 and working equipment 5.
[0053] Though not illustrated, the undercarriage 2 includes a truck
frame and a pair of travel devices 2A (sometimes collectively
referred to as a travel device 2A hereinafter) provided on both
ends of the truck frame in a vehicle-width direction orthogonal to
a travel direction. Each of the travel devices 2A includes a drive
wheel and an idler wheel provided to the truck frame, and a crawler
2B wrapped around the drive wheel and the idler wheel. The travel
device 2A moves the electric rotary excavator 1 forward and
backward by driving the drive wheel in an extension direction of
the crawler 2B.
[0054] The upper structure 3 is swingably provided on the truck
frame of the undercarriage 2 via a swing circle. The upper
structure 3 is driven by a motor generator (detailed later).
[0055] A cab 4 is provided at a front left side of the upper
structure 3 in the travel direction. The working equipment 5 is
provided at a front center of the upper structure 3 in a manner
adjacent to the cab 4. A counterweight 3A is provided to a rear
side of the upper structure 3 (i.e. a side opposite the cab 4 and
the working equipment 5). The counterweight 3A is provided to keep
a weight balance during the excavation work of the electric rotary
excavator 1.
[0056] An operator gets in the cab 4 to handle the electric rotary
excavator 1. Though not illustrated in FIG. 1, an operator's seat
is provided in the cab 4. Control levers are provided on both sides
of the operator's seat. Travel pedal(s) are provided on the floor
surface of the cab 4.
[0057] The working equipment 5 includes a boom 6, an arm 7, a
bucket 8, and cylinders including a boom cylinder 6A, an arm
cylinder 7A, and a bucket cylinder 8A respectively for moving the
boom 6, the arm 7 and the bucket 8.
[0058] A base end of the boom 6 is movably connected to the upper
structure 3. The boom cylinder 6A having ends respectively
connected to the upper structure 3 and the boom 6 is configured to
be extended and retracted to vertically move the boom 6.
[0059] The arm 7 has a base end swingably connected to a distal end
of the boom 6, so that the arm 7 can be vertically moved by an
extension and retraction of the arm cylinder 7A having ends
respectively connected to the boom 6 and the arm 7.
[0060] The bucket 8 has a base end swingably connected to a distal
end of the arm 7, so that the bucket 8 can be moved by an extension
and retraction of the bucket cylinder 8A having ends respectively
connected to the arm 7 and the bucket 8.
[0061] The boom cylinder 6A, the arm cylinder 7A, and the bucket
cylinder 8A are hydraulic cylinders driven by hydraulic oil
discharged by a hydraulic pump.
[0062] It should be noted that, though the upper structure 3 is
driven by the motor generator in the exemplary embodiment, the
scope of the invention is not limited thereto. Specifically, the
electric rotary excavator 1 may alternatively be a hybrid or
electrically driven electric rotary excavator in which at least one
of the boom 6, the arm 7, the bucket 8 and the undercarriage 2 is
driven by the motor generator.
[0063] FIG. 2 shows an overall arrangement of a drive system of the
electric rotary excavator 1. It should be noted that a swing center
of the upper structure 3 is defined as an origin, the travel
direction of the undercarriage 2 is referred to as a front-back
direction and a direction orthogonal to the travel direction is
referred to as a right-left direction in the description
hereinbelow.
[0064] The electric rotary excavator 1 includes an engine 11 (drive
source), a generator motor 13 driven by the engine 11 to generate
electric power, a rechargeable battery 17 configured to store the
electric power, inverters 13I, 171, a transformer 17C, a hydraulic
pump 12, control levers 20L, 20R, a hydraulic control valve 14, an
engine controller 11A, a pump controller 14A, a hybrid controller
16 and a multimonitor 23. The electric power generated by the
generator motor 13 and/or the electric power discharged by the
rechargeable battery 17 is supplied to a rotary motor generator 19
to drive the rotary motor generator 19 to cause a swing motion of
the upper structure 3.
[0065] The engine 11 is driven by a control command from the engine
controller 11A to drive the hydraulic pump 12 and the generator
motor 13.
[0066] The hydraulic drive system includes the hydraulic control
valve 14, the above-described boom cylinder 6A, the arm cylinder
7A, the bucket cylinder 8A, and a travel motor 15, which are driven
by the hydraulic pump 12 (hydraulic source). The hydraulic control
valve 14 is driven by a pilot hydraulic pressure (PPC pressure)
generated by operating the control levers 20L, 20R. The hydraulic
pump 12 is a variable displacement pump having a variable
displacement unit (e.g. a swash plate and an axle). The hydraulic
pump 12 includes a swash-plate-angle detection sensor for detecting
a swash plate angle of the hydraulic pump 12. The detected swash
plate angle is inputted to the pump controller 14A and the pump
controller 14A issues a control command to variably control an
output flow of the hydraulic pump 12.
[0067] A motor drive system includes the generator motor 13, the
hybrid controller 16, the rechargeable battery 17, the rotary motor
generator 19, the inverters 13I, 19I, and the transformer 17C.
[0068] The hybrid controller 16 includes an input unit, an output
unit, a calculation unit, and a storage.
[0069] The input unit of the hybrid controller 16 receives a swing
operation command of the upper structure 3, and information
acquired by a sensor provided mainly to the motor drive system
(e.g. a position information of the rotary motor generator 19 and
voltage between systems connected with the inverters 13I, 19I and
the transformer 17C).
[0070] The output unit of the hybrid controller 16 issues a command
to the inverters 13I, 19I and the transformer 17C. The inverters
13I, 19I and the transformer 17C are connected with each other via
power lines. In response to the command from the hybrid controller
16, the electric power is transferred between the inverter 13I and
the generator motor 13, between the inverter 19I and the rotary
motor generator 19, and between the transformer 17C and the
rechargeable battery 17.
[0071] The calculation unit of the hybrid controller 16 calculates
a rotation speed of the rotary motor generator 19 and a drive
command for the rotary motor generator 19 (described later).
[0072] The storage of the hybrid controller 16 stores drive
characteristics of the rotary motor generator 19.
[0073] The rotary motor generator 19 is driven by the power from
the generator motor 13 and/or the rechargeable battery 17. The
rotary motor generator 19 converts a braking force into the
electric power when the upper structure 3 is braked and supplies
the electric power to the generator motor 13 and the rechargeable
battery 17.
[0074] The rotary motor generator 19 includes a sensor 24 (e.g. a
resolver), which detects a rotary position of the rotary motor
generator 19 and outputs the detected rotary position to the hybrid
controller 16. It should be noted that the electric power to the
rotary motor generator 19 is calculated using a voltage between the
systems and the electric current or the rotation speed of the
rotary motor generator 19.
[0075] These drive systems are configured to be driven in response
to an operator's operation on a left control lever 20L and a right
control lever 20R provided in the cab 4.
[0076] Specifically, the boom 6 is configured to be moved upward or
downward when the operator operates the right control lever 20R in
the front-back direction. The bucket 8 is configured to conduct the
excavation/damping operation when the operator operates the right
control lever 20R in the right-left direction. The arm 7 is
configured to conduct the damping/excavation operation when the
operator operates the left control lever 20L in the front-back
direction. The upper structure 3 is configured to be swung in the
right-left direction when the operator operates the left control
lever 20L in the right-left direction.
[0077] When the left control lever 20L is operated in the
right-left direction in order to swing the upper structure 3, the
PPC command detected by the PPC pressure detection unit 21 is
received by the pump controller 14A and the hybrid controller
16.
[0078] The hybrid controller 16 outputs a swing command to the
inverter 19I. The inverter 19I supplies the electric power to the
rotary motor generator 19 to drive the rotary motor generator
19.
[0079] Further, in response to the operation on the control levers
20L, 20R, the PPC pressure is directly inputted to the hydraulic
control valve 14 to control the hydraulic oil from the hydraulic
pump 12 to drive the cylinders 6A, 7A, 8A, and the travel motor
15.
[0080] A throttle dial 22 and the multimonitor 23 are provided in
the cab 4 on the upper structure 3.
[0081] A control command to the engine controller 11A is issued by
operating the throttle dial 22 to control the output of the engine
11.
[0082] The multimonitor 23 includes a control unit 23A and a
display 23B. The multimonitor 23 may be a touch panel configured to
be operated by a direct touch on the display.
[0083] The control unit 23A includes a plurality of operation
buttons independent of the monitor and is configured to switch the
display status and input an operation command.
[0084] The status of the engine 11 (e.g. a residual fuel amount and
cooling water temperature) as well as temperature conditions and
the like of the generator motor 13, the rechargeable battery 17 and
the rotary motor generator 19 is displayed on the display 23B.
[2] Arrangement of Calculation Unit 18 of Hybrid Controller 16
[0085] FIG. 3 shows a functional block diagram of a calculation
unit 18 of the hybrid controller 16 according to the exemplary
embodiment of the invention. The calculation unit 18 of the hybrid
controller 16 includes a lever command speed calculation unit 31, a
jerk command speed calculation unit 32, a reaction-force control
command speed calculation unit 33, a torque command value
calculation unit 34, a command value output unit 35, and a command
value output restriction unit 36.
[0086] Further, the hybrid controller 16 is connected with a rotary
speed detection unit 37 configured to detect the swing speed of the
upper structure 3 driven by the rotary motor generator 19, a rotary
position detection unit 38 configured to detect the rotary position
of the rotary motor generator 19, and an output torque detection
unit 39 configured to detect an output torque of the rotary motor
generator 19, so that an actual swing speed and an actual rotary
position of the upper structure 3, and a detection value of the
output torque of the rotary motor generator 19 are fed back to the
hybrid controller 16. The swing speed to be detected by the rotary
speed detection unit 37 and the rotary position of the rotary motor
generator 19 to be detected by the rotary position detection unit
38 are obtained based on the detection value of the above-described
sensor 24 (see FIG. 2). The output torque of the rotary motor
generator 19 is obtained based on the above-described voltage
between the systems, and the rotation speed of the rotary motor
generator 19 or the electric current inputted to the rotary motor
generator 19. It should be noted that, in the description below,
the operation on the left control lever 20L in the right-left
direction for operating the upper structure 3 will be referred to
as the operation on the "swing lever 20L."
[0087] The lever command speed calculation unit 31 calculates the
lever command speed based on a lever operation amount of the swing
lever 20L detected by the PPC pressure detection unit 21. The lever
command speed calculation unit 31 includes a table in which the
lever operation amount is associated with the lever command speed,
and calculates and outputs the lever command speed with reference
to the table.
[0088] The jerk command speed calculation unit 32 calculates a jerk
command speed including a gradient of the acceleration or
deceleration of the upper structure 3 based on the lever command
speed calculated by the lever command speed calculation unit 31.
Specifically, as shown in FIG. 4, the jerk command speed
calculation unit 32 receives a lever command speed Vi of the swing
lever 20L during an acceleration period (receives a lever operation
command changed from Vi to 0 during a deceleration period), and
calculates the acceleration (deceleration) G so that a constant
jerk value Ja can be obtained until the acceleration reaches a
predetermined acceleration Ga (or the deceleration G reaches
deceleration Gb during the deceleration period). In order to avoid
sharp acceleration (deceleration) of the upper structure 3 when the
lever command speed Vi is inputted (when the lever command speed
input is changed from Vi to 0 during the deceleration period), the
acceleration Ga (deceleration Gb during the deceleration period) is
calculated based on the jerk value Ja in a form of the gradient of
the acceleration (a jerk value Jb in a form of the gradient of the
deceleration during the deceleration period) and a jerk command
speed Vo is calculated and outputted in order to perform a smooth
acceleration (deceleration). It should be noted that, when the
upper structure 3 is in a low-speed state where the swing speed is
at a first threshold (described later) or less, the jerk command
speed calculation unit 32 exceptionally outputs the lever command
speed as the jerk command speed in a section where the lever
command speed is changed from Vi to 0. Then, the above exceptional
process is cleared when the swing speed falls below the first
threshold (i.e. immediately before the swing motion is
stopped).
[0089] The reaction-force control command speed calculation unit 33
calculates a reaction-force control command speed for controlling
the position of the upper structure 3 with reference to the current
position (origin) of the rotary motor generator 19. Specifically,
the reaction-force control command speed calculation unit 33
calculates the origin position of the rotary motor generator 19
based on the current position of the rotary motor generator 19
detected by the rotary position detection unit 38, the actual swing
speed detected by the rotary speed detection unit 37, the output
torque of the rotary motor generator 19 detected by the output
torque detection unit 39, the calculated lever command speed, and
the jerk command speed.
[0090] When the upper structure 3 is actually swung in a direction
different from the direction indicated by the lever operation
command of the swing lever 20L, the reaction-force control command
speed calculation unit 33 calculates the reaction-force control
command speed by applying a gain to a difference between the origin
position and the current position of the rotary motor generator 19.
The calculated reaction-force control command speed is a command
speed at which a lock torque for locking the position of the upper
structure 3 is applied so that the rotary motor generator 19 is not
reversely rotated in spite of an external force applied while the
upper structure 3 is stopped or the lever command speed.
[0091] The torque command value calculation unit 34 calculates a
feed-forward torque command value (referred to as an FF torque
command value hereinafter) based on the acceleration G calculated
by the jerk command speed calculation unit 32 and a predetermined
inertial value. It should be noted that the torque command value
calculation unit 34 calculates the FF torque command value to be
zero when the output of the torque command value is restricted by
the command value output restriction unit 36 as described
later.
[0092] The command value output unit 35 outputs the torque command
value calculated by the torque command value calculation unit 34 to
the rotary motor generator 19. Specifically, the command value
output unit 35 adds the calculated jerk command speed to the
reaction-force control command speed to set a command speed, and
subtracts the actual swing speed detected by the rotary speed
detection unit 37 from the command speed to define a difference.
Then, the command value output unit 35 applies a torque conversion
to the difference to define a speed deviation torque command
value.
[0093] Subsequently, the command value output unit 35 adds the
torque-converted speed deviation torque command value to the FF
torque command value calculated by the torque command value
calculation unit 34 to calculate the torque command value and
outputs the torque command value to the rotary motor generator
19.
[0094] The command value output restriction unit 36 restricts an
output of the torque command value from the command value output
unit 35 under predetermined conditions.
[0095] The output of the torque command value is restricted by the
command value output restriction unit 36 when all of the following
conditions are satisfied.
[0096] Condition 1: The actual swing speed detected by the rotary
speed detection unit 37 is smaller than a first threshold.
[0097] Condition 2: The operator sets the swing lever 20L at a
neutral position when the inclination angle of the swing lever 20L
is smaller than a predetermined angle and is trying to stop the
swing motion of the upper structure 3.
[0098] Condition 3: The jerk command speed calculated by the jerk
command speed calculation unit 32 is smaller than a third
threshold.
[0099] Condition 4: A deviation between the command speed obtained
by adding the reaction-force control command speed to the
calculated jerk command speed and the actual swing speed is larger
than a second threshold (i.e. an excavation work is performed while
an external force is applied on the bucket 8 in the swing
direction).
[0100] In the exemplary embodiment, the second threshold is defined
as a rotation speed larger than the rotation speed defined as the
first threshold, and the third threshold is defined as a rotation
speed larger than the rotation speed defined as the second
threshold.
[0101] The following judgment is made according to the
above-described conditions. With the use of the conditions 1 and 2
as part of the judgment conditions, it can be judged that the swing
speed of the upper structure is low and the operator hopes to stop
the swing motion. With the use of the condition 3 as one of the
judgment conditions, it can be judged that the jerk command speed
is low and the swing speed is low. With the use of the condition 4
as one of the judgment conditions, it can be judged that the swing
command speed is different from the actual swing speed due to an
external force.
[0102] Using the above conditions 1 to 4 for restricting the output
of the FF torque command, unintentional output of the FF torque
generated when the speed of the swing motion is low and the
reaction force is applied and the upper structure is moved in an
unintended direction can be avoided. It should be noted that the
above condition 3 in the above conditions is not requisite.
[0103] Further, the command value output restriction unit 36 sets
the FF torque command value at zero to restrict the output of the
torque command value from the command value output unit 35 also
when the reaction-force control command speed calculated by the
reaction-force control command speed calculation unit 33 is smaller
than the jerk command speed calculated by the jerk command speed
calculation unit 32.
[0104] On the other hand, the command value output restriction unit
36 does not set the FF torque command value at zero when the
following conditions are satisfied.
[0105] Condition 5: The external force is not applied on the bucket
8 and the actual swing speed is not greatly different from the jerk
command speed.
[0106] Condition 6: The speed deviation torque obtained based on
the deviation between the command speed and the actual swing speed
is in the same direction as the FF torque command value (the
absolute value of the actual swing speed>the absolute value of
the jerk command speed).
[0107] When the above conditions are satisfied, the command value
output restriction unit 36 does not set the FF torque command value
at zero but directly outputs the calculated FF torque command value
to the command value output unit 35 even if the conditions 1 to 3
are satisfied.
[3] Effects of Embodiment (Output Torque Control Method for Motor
Generator)
[0108] Next, effects of the exemplary embodiment will be described
below with reference to a flowchart shown in FIG. 5.
[0109] Initially, the PPC pressure detection unit 21 detects the
operation amount of the swing lever 20L (step S1), and outputs the
detected lever operation amount to the lever command speed
calculation unit 31.
[0110] The lever command speed calculation unit 31 calculates the
lever command speed based on the lever operation amount (step S2),
and outputs the lever command speed to the jerk command speed
calculation unit 32.
[0111] The jerk command speed calculation unit 32 calculates the
jerk command speed based on the calculated lever command speed
(step S3).
[0112] The torque command value calculation unit 34 calculates the
FF torque command value based on the acceleration G calculated
based on the jerk command speed, and the inertial value (step
S4).
[0113] The reaction-force control command speed calculation unit 33
calculates the origin position of the rotary motor generator 19 and
the difference between the origin position and the actual swing
position, and applies a gain and integration to the difference to
calculate the reaction force command speed (step S5).
[0114] The command value output restriction unit 36 judges whether
the actual swing speed (above-described condition 1) is smaller
than the first threshold (step S6).
[0115] When the condition 1 is satisfied (Yes in step S6), the
command value output restriction unit 36 judges whether or not the
lever command speed is zero (second condition) to determine whether
or not the operator is trying to stop the swing motion of the upper
structure 3 (step S7).
[0116] When the second condition is satisfied (Yes in step S7), the
command value output restriction unit 36 judges whether the jerk
command speed is at or less than the third threshold (the third
condition) (step S8).
[0117] When the third condition is satisfied (Yes in step S8), the
command value output restriction unit 36 judges whether or not the
command value obtained by adding the reaction-force control command
speed to the jerk command speed is greater than the second
threshold (the fourth condition) (step S9). When the fourth
condition is satisfied (Yes in step S9), the command value output
restriction unit 36 sets the FF torque command value at zero and
outputs the FF torque command value to the command value output
unit 35 (step S11).
[0118] On the other hand, when one of the first to fourth
conditions (S6 to S9) is not satisfied (S6 to S9: No), the command
value output restriction unit 36 judges whether or not the
reaction-force control command speed is greater than the jerk
command speed (step S10). When the reaction-force control command
speed is not greater than the jerk command speed (step S10: No),
the torque command value calculation unit 34 outputs the FF torque
determined based on the acceleration G and the inertial value to
the command value output unit 35 (step S12).
[0119] When the command value output restriction unit 36 judges
that the reaction-force control command speed is greater than the
jerk command speed (Yes in step S10), the torque command value
calculation unit 34 sets the FF torque command value at zero and
outputs the FF torque command value to the command value output
unit 35 (step S11).
[0120] The command value output unit 35 adds the speed deviation
torque command value to the FF torque command value to define the
torque command value and outputs the torque command value to the
rotary motor generator 19 (step S13).
[4] Advantage(s) of Exemplary Embodiment(s)
[0121] The exemplary embodiment offers the following
advantages.
[0122] It is assumed that an excavation work is performed while a
left side of the bucket 8 is in contact with an excavation wall W
as shown in FIG. 6. The operator handles a bucket control lever to
downwardly apply an excavation force F1 and simultaneously handles
the swing lever 20L leftward. In this state, since a reaction force
F2 from the excavation wall W acts on the bucket 8, the actual
swing speed of the upper structure 3 is substantially zero
irrespective of the constant output of the jerk command speed.
[0123] When the operator sets the swing lever 20L to a neutral
position at a time t1 (see FIG. 7), the leftward jerk command speed
is reduced until the jerk command speed immediately before the
swing motion is stopped is commanded based on the lever command
speed. At the jerk command speed immediately before the swing
motion is stopped, since the reaction force F2 from the excavation
wall W exceeds the output torque of the rotary motor generator 19,
the upper structure 3 swings rightward. At this time, since the FF
torque command value F3 is outputted to cause a rightward swing
motion, a large torque fluctuation occurs to cause vibrations on
the rotary motor generator 19. The subsequent reaction-force
control command speed enlarges the speed deviation torque, which is
balanced with the reaction force F2, thereby stopping the upper
structure 3.
[0124] The above is observable in a graph shown in FIG. 7. It
should be noted that the upper side of an ordinate axis of the
graph indicates a left side in the swing direction in FIG. 6 and
the lower side indicates a right side in the swing direction in
FIG. 6. When the operator operates the swing lever 20L to press the
bucket 8 onto the excavation wall W and then sets the swing lever
20L to the neutral position, since the actual swing speed is low,
the jerk command speed decreases in conformity with the lever
command speed until a time immediately before the swing motion is
stopped and slowly comes close to zero based on the jerk command
speed from the time immediately before the swing motion is
stopped.
[0125] A description is made on a comparative example having no
command value output restriction unit 36 (i.e. an instance before
no countermeasures are taken). The actual swing speed of the upper
structure 3 does not increase while the working equipment 5 is
pressed onto the excavation wall W by an operation of the swing
lever 20L, since the output torque of the rotary motor generator 19
is balanced with the reaction force F2. When the operator sets the
swing lever 20L to the neutral position at the time t1, the upper
structure 3 is swung in a direction (a minus direction) opposite
the direction in which the working equipment 5 is pressed onto the
excavation wall W due to the reaction force F2 from the excavation
wall W.
[0126] At this time, the output torque outputted by the command
value output unit 35 rapidly decreases when the swing lever 20L is
set to the neutral position. This is because the speed deviation
torque rapidly decreases in conjunction with the decrease in the
jerk command speed and the rightward FF torque is outputted. When
the FF torque command value F3 is outputted, the torque command
value is outputted to the rotary motor generator 19 in a direction
promoting the rapid decrease in the output torque outputted by the
command value output unit 35 to promote the rightward swing motion.
Subsequently, in accordance with the enhancement of the reaction
force control, the output torque outputted by the command value
output unit 35 is outputted leftward to keep the position of the
working equipment at a time t2 to stop the working equipment.
[0127] In contrast, in the arrangement modified according to the
exemplary embodiment (i.e. an instance after the countermeasures
are taken), since the FF torque command value is set at zero and
the FF torque command value is not outputted from the command value
output unit 35 when all the above-described conditions starting
from the condition 1 are satisfied as shown in dashed lines in FIG.
7, the reduction in the output torque of the rotary motor generator
19 can be restrained, so that the change in the actual swing speed
of the upper structure 3 can be restrained and the vibrations are
reduced.
[0128] Further, since the FF torque command value is set at zero
when the reaction-force control command speed exceeds the jerk
command speed, priority is given to the torque command value based
on the reaction-force control command speed, so that the upper
structure 3 can be rapidly stopped by the torque command value in a
direction resisting the reaction force F2.
[5] Modification(s) of Embodiment(s)
[0129] It should be understood that the scope of the invention is
not limited to the above-described exemplary embodiment(s), but
includes modifications as described below.
[0130] In the above-described exemplary embodiment, the
reaction-force control command speed calculation unit 33 is
provided and the command value output restriction unit 36 restricts
the FF torque command value when the reaction-force control command
speed calculated by the reaction-force control command speed
calculation unit 33 is greater than the jerk command speed
calculated by the jerk command speed calculation unit 32. However,
the scope of the invention is not limited to the above arrangement
but the magnitudes of the reaction-force control command speed and
the jerk command speed are not necessarily compared.
[0131] The FF torque command value is calculated based on the
acceleration calculated by the jerk command speed calculation unit
32 in the above-described exemplary embodiment. However, the scope
of the invention is not limited to the above arrangement but the FF
torque command value may alternatively be calculated by calculating
the acceleration using other methods.
[0132] The specific structure and shape in implementing the
invention may be altered in a different manner as long as such an
alteration is compatible with an object of the invention (e.g. the
upper structure is driven using a motor generator and a hydraulic
drive mechanism).
EXPLANATION OF CODE(S)
[0133] 1 . . . electric rotary excavator, 2 . . . undercarriage, 2A
. . . travel device, 2B . . . crawler, 3 . . . upper structure, 4 .
. . cab, 5 . . . working equipment, 6 . . . boom, 6A . . . boom
cylinder, 7 . . . arm, 7A . . . arm cylinder, 8 . . . bucket, 8A .
. . bucket cylinder, 11 . . . engine, 11A . . . engine controller,
12 . . . hydraulic pump, 13 . . . generator motor, 13I . . .
inverter, 14 . . . hydraulic control valve, 14A . . . pump
controller, 15 . . . travel motor, 16 . . . hybrid controller, 17 .
. . rechargeable battery, 17C . . . transformer, 18 . . .
calculation unit, 19 . . . rotary motor generator, 19I . . .
inverter, 20L . . . swing lever, 20R . . . right control lever, 21
. . . PPC pressure detection unit, 22 . . . throttle dial, 23 . . .
multimonitor, 23A . . . control unit, 23B . . . display, 24 . . .
sensor, 31 . . . lever command speed calculation unit, 32 . . .
jerk command speed calculation unit, 33 . . . reaction-force
control command speed calculation unit, 34 . . . torque command
value calculation unit, 35 . . . command value output unit, 36 . .
. command value output restriction unit, 37 . . . swing speed
detection unit, 38 . . . rotary position detection unit, 39 . . .
output torque detection unit, 3A . . . counterweight, W . . .
excavation wall.
* * * * *