Another aspect of the present disclosure relates to a work vehicle.
The work vehicle includes a boom assembly having an end effector. An actuator
engaged to the boom assembly. The actuator is adapted to position the boom
assembly. An actuator sensor is adapted to measure the displacement of the
actuator. A flow control valve is in fluid communication with the actuator. A
controller is in electrical communication with the flow control valve. The controller
is adapted to actuate the flow control valve in response to an input signal. The
controller includes a motion control scheme that includes a coordinate
transformation module, a deflection compensation module, an axis control module,
and an input shaping module. The coordinate transformation module converts a
desired coordinate of the end effector of the boom assembly from Cartesian space to
actuator space. The deflection compensation module calculates a deflection error of
the end effector based on measurements from the actuator sensor. The axis control
module generates a control signal based on the desired coordinate, the deflection
error and the measurements from the actuator sensor. The input shaping module
shapes the control signal transmitted to the flow control valve to reduce vibration of
the boom assembly.
Another aspect of the present disclosure relates to a method of
calibrating the damping ratio and the natural frequency of a boom assembly using a
flow control valve. The method includes receiving pressure signals from pressure
sensors regarding pressure in an actuator. High and low pressure values and times
associated with those pressure values are recorded for a first cycle. High and low
pressure values and times associated with those pressure values are recorded for a
second cycle. Natural frequency and damping ratio are calculated based on the
pressure values and times associated with those pressure values for the first and
second cycles.
Another aspect of the present disclosure relates to a method for
shaping a control signal for a flexible structure. The method includes generating a
control signal based on a desired coordinate. The control signal is shaped using a
time-varying input shaping scheme. The time-varying input shaping scheme '
receives a measurement from a sensor, estimates a natural frequency and damping
ratio of the flexible structure based on the measurement of the sensor and shapes the
control signal based on the measurement and the estimated natural frequency and the
damping ratio.

MOTION CONTROL OF WORK VEHICLE
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is being filed on 16 October 2009, as a PCT
International Patent application in the name of Eaton Corporation, a U.S. national
corporation, applicant for the designation of all countries except the U.S., and
QingHui Yuan, a citizen of China, Jae Y. Lew, a citizen of the U.S., and Damrongrit
Piyabongkarn, a citizen of Thailand, applicants for the designation of the U.S. only,
and claims priority to U.S. Provisional Patent Application Serial No. 61/105,952
filed on 16 October 2008.
BACKGROUND
Construction vehicles can be used to provide temporary access to
relatively inaccessible areas. Many of these vehicles include a boom having
multiple joints. The boom can be controlled by controlling the displacements of the
joints. However, such control is dependent on an operator's proficiency.
As the boom is extended, vibration becomes a concern. Conventional
techniques to reduce or eliminate vibration typically result in systems that are not
responsive to their operators.
SUMMARY
An aspect of the present disclosure relates to a method for controlling
a boom assembly. The method includes providing a boom assembly having an end
effortor. The boom assembly includes an actuator in fluid communication with a
flow control valve. A desired coordinate of the end effector of the boom assembly is
converted from Cartesian space to actuator space. A deflection error of the end
effector based on a measured displacement of the actuator is calculated. A resultant
desired coordinate of the end effector is calculated based on the desired coordinate
and the deflection error. A control signal for the flow control valve is generated
based on the resultant desired coordinate and the measured displacement of the
actuator. The control signal is shaped to reduce vibration of the boom assembly.
The shaped control signal is transmitted to the flow control valve.

A variety of additional aspects will be set forth in the description that
follows. These aspects can relate to individual features and to combinations of
features. It is to be understood that both the foregoing general description and the
following detailed description are exemplary and explanatory only and are not *
restrictive of the broad concepts upon which the embodiments disclosed herein are
based.
DRAWINGS
FIG.1 is a side view of a work vehicle having exemplary features of
aspects in accordance with the principles of the present disclosure.
FIG. 2 is a schematic representation of a control system for the work
vehicle of FIG. 1.
FIG. 3 is a schematic representation of a flow control valve suitable
for use in the control system of FIG. 2.
[0012] FIG. 4 is a schematic representation of a motion control scheme used
by a controller of the control system of FIG. 2.
[0013] FIG. 5 is a schematic representation of deflection of a boom assembly
of the work vehicle of FIG. 1.
[0014] FIG. 6 is a schematic representation of a joint-actuator space
transformation.
[0015] FIG. 7 is a representation of a method for determining a damping
ratio and a natural frequency of the boom assembly.
[0016] FIG. 8 is a representation of a method for calibrating the damping
ratio and the natural frequency using the flow control valve.
DETAILED DESCRIPTION
Reference will now be made in detail to the exemplary aspects of the
present disclosure that are illustrated in the accompanying drawings. Wherever
possible, the same reference numbers will be used throughout the drawings to refer
to the same or like structure.
Referring now to FIG. 1, an exemplary work vehicle, generally-
designated 10, is shown. The work vehicle 10 includes multiple joints that are
actuated using linear and/or rotary actuators (e.g., cylinders, motors, etc.). These

linear and rotary actuators are adapted to extend or retract a boom assembly and to
control a work platform disposed on an end of the boom assembly.
The work vehicle 10 includes a plurality of flow control valves and a
plurality of sensors. The flow control valves are controlled by an electronic control
unit of the work vehicle 10. The electronic control unit receives desired inputs from
an operator and measured inputs from the plurality of sensors. Using a motion
control scheme, the electronic control unit outputs signals to the flow control valves
to move the work platform to a desired location. The motion control scheme is
adapted to reduce vibration in the boom assembly and to maintain good
responsiveness to operator input.
While the work vehicle 10 could be one of a variety of work vehicles,
such as a crane, a boom lift, a scissor lift, etc., the work vehicle 10 will be described
herein as being an aerial work platform for ease of description. The aerial work
platform 10 is adapted to provide access to areas that are generally inaccessible to
people at ground level due to height and/or location.
In the depicted embodiment of FIG. 1, the aerial work platform 10
includes a base 12 having a plurality of wheels 14. The aerial work platform 10
further includes a body 16 that is rotatably mounted to the base 12 so that the body
16 can rotate relative to the base 12. The rotation angle of the body 16 is denoted by
θ1 A first motor 18 (shown in FIG. 2) rotates the body 16 relative to the base 12. In
one aspect of the present disclosure, the first motor 18 is coupled to a gear reducer.
A flexible structure 20 is mounted to the body 16 with a revolute
joint. For ease of description, the flexible structure 20 will be described herein as a
boom assembly 20. The boom assembly 20 can move upwards and/or downwards.
This upwards and/or downwards movement of the boom assembly 20 is denoted by
a rotation angle θ2 of the boom assembly 20. A first cylinder 22 (shown in FIG. 2)
is adapted to raise and lower the boom assembly 20. A first end 24 (shown in FIG.
2) of the first cylinder 22 is connected to the boom assembly 20 while a second end
26 (shown in FIG. 2) is connected to the body 16.
The boom assembly 20 includes a base boom 28, an intermediate
boom 30 and a tip boom 32. The base boom 28 is connected to the body 16 of the
aerial work platform 10. The intermediate and tip booms 30, 32 are telescopic
booms that extend outwardly from the base boom 28 in an axial direction. As
shown in FIG. 1, the intermediate and tip booms 30, 32 are in a retracted position.

The length l3 of the boom assembly 20 can be changed by retracting or extending the
intermediate and tip booms 30,32. The length l3 of the boom assembly 20 is
changed via a second cylinder 34 and corresponding mechanical linkage 36.
A work platform 38 is mounted to an end 40 of the tip boom 32. The
pitch of the work platform 38 is held parallel to the ground by a master-slave
hydraulic system design while a yaw orientation θ5 of the work platform 38 is
controlled by a second motor 42.
Referring now to FIG. 2, a simplified schematic representation of a
control system 50 for the aerial work platform 10 is shown. The control system 50
includes a fluid pump 52, a fluid reservoir 54, a plurality of flow control valves 56, a
plurality of actuators 58 and a controller 60.
In one aspect of the present disclosure, the fluid pump 52 is a load-
sensing pump. The load-sensing pump 52 is in fluid communication with a load
sensing valve 150. The load-sensing valve 150 is adapted to receive a signal 152
from the controller 60. In one aspect of the present disclosure, the signal 152 is a
pulse width modulation signal.
The plurality of actuators 58 includes the first and second cylinders
22,34 and the first and second motors 18,42. The plurality of flow control valves
56 is adapted to control the plurality of actuators 58. By controlling the plurality of
actuators 58, the work platform 38 can reach a desired location with a desired
orientation within the work envelope of the aerial work platform 10.
In one aspect of the present disclosure, a first flow control valve 56a
is in fluid communication with the first cylinder 22, a second flow control valve 56b
is in fluid communication with the second cylinder 34, a third flow control valve 56c
is in fluid communication with the first motor 18 and a fourth flow control valve 56d
is in fluid communication with the second motor 42. A valve suitable for use as
each of the flow control valves 56a-56d has been described in UK Pat. No.
GB2328524 and U.S. Pat. No. 7,518,523, the disclosures of which are hereby .
incorporated by reference in their entirety. Each of the flow control valves 56a-56d
includes, a supply port 62 that is in fluid communication with the fluid pump 52, a
tank port 64 that is in fluid communication with the fluid reservoir 54, a first control
port 66 and a second control port 68 that are in fluid communication with one of the
plurality of actuators 58.

The control system 50 further includes a plurality of fluid pressure
sensors 70. In one aspect of the present disclosure, a first pressure sensor 70a
monitors the fluid pressure from the fluid pump 52 while a second pressure sensor
70b monitors the fluid pressure going to the fluid reservoir 54. The first and second
pressure sensors 70a, 70b are in communication with the controller 60. In one
aspect of the present disclosure, the first and second pressure sensors 70a, 70b are in
communication with the controller 60 through the load sensing valve 150.
Each of the fluid control valves 56a-56d is in fluid communication
with a third pressure sensor 70c and a fourth pressure sensor 70d. The third and
fourth pressure sensors 70c, 70d monitor the fluid pressure to and from the
corresponding actuator 58 at the first and second control ports 66,68, respectively.
In one aspect of the present disclosure, the third and fourth pressure sensors 70c, 70d
are integrated into the flow control valves 56a-56d.
The control system 50 further includes a.plurality of actuator sensors
72 that monitor the axial or rotational position of the plurality of actuators 58. The
plurality of actuator sensors 72 is adapted to send signals to the controller 60 ,
regarding the displacement (e.g., position) of the plurality of actuators 58.
In the depicted embodiment of FIG. 2, first and second actuator
sensors 72a, 72b monitor the displacement of the first and second cylinders 22,34.
In one aspect of the present disclosure, the first and second actuator sensors 72a, 72b
are laser sensors. Third and fourth actuator sensors 72c, 72d monitor the rotation of
the first and second motors 18,42. In one aspect of the present disclosure, the third
and fourth actuator sensors 72c, 72d are absolute angle encoders.
Referring now to FIGS. 2 and 3, the flow control valves 56a-56d will
be described. As each of the first, second, third and fourth flow control valves 56a-
56d is structurally similar, the first, second, third and fourth flow control valves 56a-
56d will be referred to as the flow control valve 56. The flow control valve 56
includes at least one pilot stage spool 80 and at least one main stage spool 82. In the
depicted embodiment of FIG. 3, the flow control valve 56 includes a first pilot stage
spool 80a and a second pilot stage spool 80b and a first main stage spool 82a and a
second main stage spool 82b.
The positions of the first and second pilot stage spools 80a, 80b
control, the positions of the first and second main stage spools 82a, 82b, respectively,
by regulating the fluid pressure that acts on either end of the first and second main

stage spools 82a, 82b. The positions of the first and second main stage spools 82a,
82b control the fluid flow rate to the corresponding actuator 58.
The positions of the first and second pilot stage spools 80a, 80b are
controlled by first and second actuators 84a, 84b. In one aspect of the present
disclosure, the first and second actuators 84a, 84b are electromagnetic actuators,
such as voice coils.
First and second spool position sensors 86a, 86b measure the
positions of the first and second main stage spools 82a, 82b and send a first and
second signal 88a, 88b that corresponds to the positions of the first and second main
stage spools 82a, 82b to the controller 60. In one aspect of the present disclosure,
the first and second spool position sensors 86a, 86b are linear variable differential
transformers (LVDT).
Referring now to FIGS. 1,2 and 4, the controller 60 is adapted to
receive signals from the plurality of actuator sensors 72 regarding the plurality of
actuators 58 and the plurality of spool position sensors 86 regarding the position of
the main stage spools 82 of the flow control valves 56. In addition, the controller 60
is adapted to receive an input 90 regarding a desired output from the operator. The
controller 60 sends signals 92 to the first and second actuators 84a, 84b of the flow
control valves 56a-56d for actuation of the plurality, of actuators 58. In one aspect of
the present disclosure, the signal 92 are pulse width modulation signals.
In the depicted embodiment of FIG. 2, the controller 60 is shown as a
single controller. In one aspect of the present disclosure, however, the controller 60
includes a plurality of controllers. In another aspect of the present disclosure, the
plurality of controllers 60 is integrated in the plurality of flow control valves 56.
The controller 60 includes a motion control scheme 100. The motion
control scheme 100 is a closed loop coordinated control scheme. The motion
control scheme 100 includes a trajectory generator, a coordinate transformation
module 104, a deflection compensation module 106, an axis control module 108 and
an input shaping module 110.
The trajectory generator generates the desired Cartesian coordinate
Xd=[x0,y0,z0,0]T end effector (e.g., work platform 38) of the work,
vehicle 10 based on the input 90 from the operator. The Cartesian coordinate
includes the position and orientation of the end effector.

In equation 114, the Denavit-Hartenberg notation is used to describe
the kinematic relationship. is the length of the common normal, di is the
distance between the origin and the intersection of the common normal to
is the angle between the joint axis zi and with respect to and
is the angle between and the common normal with respect to The
parameters for the work platform 38 are given in Table II.

The end effector position and orientation can be obtained by using the
values of the joint displacements in equation 116 below. In
this particular case θ4 is not an independent variable since as shown in FIG.
l.
To solve equation 116, take the origin of as an end
effector. If the position of 0$ relative to and the angle
20 there is a homogeneous transformation matrix of

accounts for deflection of the boom assembly 20. The deflection compensation
module 106 receives measurements from the plurality of actuator sensors 72, which
monitor the actual axial and/or rotational position of the plurality of actuators 58.
Using these measurements, the deflection compensation module 106 calculates a
corresponding error correction in joint space.
For a long flexible structure, such as the boom assembly 20,
deflection of that structure can cause a large error between an ideal end effector
coordinate and the actual end effector coordinate. This deflection error is a function
of the end effector coordinate. For example, for different lifting heights and lengths,
the deflection will be different The deflection error in joint space primarily comes
from the rotation angle θ2 of the boom assembly 20, as shown in FIG. 5. The
deflection errors for the other degrees of freedom are negligibly small. Therefore,

A quasi-steady analysis of deflection compensation is provided
below. This quasi-steady analysis is appropriate in this case since vibration in the
boom assembly 20 is reduced or eliminated as a result of the input shaping module
110, which will be described in greater detail below.
The deflection of the boom assembly 20 is affected by gravity acting
on .the boom assembly 20 and the load acting on the work platform 3 8. The
deflection of the boom assembly 20 is a function of the length l3 of the boom
assembly 20 and the rotation angle θ2 of the boom assembly 20. Assuming a
uniformly distributed cross section of the boom assembly 20, the deflection can be
calculated using the following equation:

where E is the modulus of elasticity of the beam material, / is the moment of inertia
of the cross section of the beam, p is the mass length density, and m is the mass of
the load. A rigid boom assembly with a rotation angle θ2 can have the same tip
position if is given by the following equation:


Equation 130 is in joint space while the actual measurements of the
actuator sensors 72 are in actuator space. Therefore, an actuator-to-joint space
transformation would be needed for this conversion.
Referring now to FIGS. 1,2,4, and 6, the second coordinate
transformation module 104b will be described. The second coordinate
transformation module 104b converts the resultant desired coordinate
in joint space to actuator space. Actuator space refers to the
plurality of actuators 58. In one aspect of the present disclosure, actuator space
refers to the first and second cylinders 22,34 and the first and second motors 18,42.
Table I, which is provided above, lists the independent variables for Cartesian space,
joint space and actuator space. There is direct correspondence between the
independent Variables in joint space and the corresponding
independent variables in actuator space. The relationship between I3, and LAB,
however, will now be described.
Referring now to FIG. 6, a schematic representation of the boom
assembly 20 and the first cylinder 22. The second end 26 of the first cylinder 22 is
mounted to the body 16 of the work vehicle 10 at point A while the first end 24 of
the first cylinder 22 is mounted to the boom assembly 20 at point B. Point A is a
fixed point in reference frame associated with the body 16 while point B
is a fixed point in the reference frame associated with the boom
assembly 20. The length between the points A and B is a function of the rotation
angle θ2 of the boom assembly 20 and can be calculated using the following
equation:


With the resultant desired coordinate converted to actuator space
the resultant desired coordinate Yd and the actual
measurements Ya from the plurality of actuator sensors 72 are received by the axis
control module 108. The axis control module 108 generates the control signal U for
the flow control valves 56.
The control signal U is a vector of flow commands qn. The flow
commands qn correspond to the plurality of actuators 58. In one aspect of the
present disclosure, a velocity feedforward proportional integral (PI) controller is
used to generate the flow commands qn. The velocity feedforward PI controller
could be:

where qn is the flow command for valve n, are the feedforward,
proportional and integral gains, respectively, and yd,n and ya,n are the desired and
actual displacements for axis number n = 1,2, 3,4. For the first and second
cylinders 22,34, the gains will be slightly different for each direction
due to piston area ratio.
An exemplary control signal U generated by the axis control module
In one aspect of the present disclosure, the flow control
valves 56 include embedded pressure sensors 70, embedded spool position sensors
88 and an inner control loop. These sensors and inner control loop allow the axis
control module 108 to send flow commands q„ directly to the flow control valves 56
as opposed to sending spool position commands.
Referring now to FIGS. 1 and 4, the input shaping module 110 will
be described. The input shaping module 110 is adapted to reduce the structural
vibration in the boom assembly 20 of the work vehicle 10.
An input shaping scheme suppresses vibration by generating shaped
command inputs. The effects of modeling errors can be reduced by increasing the
number of impulses in an input shaping scheme. However, as the number of
impulses in the input shaping scheme increases, the responsiveness of the command
input decreases.

In one aspect of the present disclosure, the input shaping scheme is a
time-varying input shaping scheme. The time-varying input shaping scheme reduces
the amount of vibration while maintaining good responsiveness. In one aspect of the
present disclosure, the time-varying input shaping scheme utilizes only two
impulses. In addition, the time-varying input shaping scheme uses measurements
from the plurality of actuator sensors 72 to provide a control signal having time-
varying parameters.
The time-varying input shaping scheme first estimates a damping
ratio and a natural frequencyof the boom assembly 20 based on the
actual measurements Ya from the plurality of actuator sensors 72. The equations for
damping ratio and natural frequency are:

where and are functions based on the length l3 of the boom assembly 20.
These functions and can be determined from modeling or by experimental
calibration with the assumption that is the only dominant variable among all the
fζ and fω,
measured variables and the effect from the payload is negligibly small. In one
aspect of the present disclosure, the flow control valve 56 determines the damping
ration function and the natural frequency function fζ and fω, respectively. This
determination of the damping ration function and the natural frequency function
and by the flow control valve 56 will be described in greater detail subsequently.
Next, the amplitudes of the two impulses are given by the following



The shaped control signal Us is sent to the flow control valves 56 so
that fluid can be passed through the flow control valves 56 to the actuators 58 to
move the work platform 38. As previously provided, the input shape module 110 is
potentially advantageous as it reduces or eliminates vibrations in the boom assembly
20 while maintaining responsiveness of the boom assembly 20.
Referring now to FIGS. 1 and 7, an exemplary method 200 for the
determining the damping ratio ζ(t) and the natural frequency will be .
described. In step 202, the actuators are actuated to a first position. For example,
the first and second cylinders 22,34 are moved to positions in which damping ratios
and natural frequencies are expected (e.g., full extension of first and second
cylinders 22,34, partial extension of first and second cylinders 22, 34, etc.).
In step 204, the boom assembly 20 is vibrated. In one aspect of the
present disclosure, the boom assembly 20 is vibrated by applying a force to the
boom assembly 20. In another aspect of the present disclosure, the boom assembly
20 is vibrated by quickly moving an input device (e.g., joystick, etc.) on the work
vehicle that controls the movement of the boom assembly 20. This movement
imparts a short pulse of hydraulic fluid to the first and/or second cylinders 22, 34
which causes the boom assembly 20 to vibrate.
In step 206, the damping ratio and the natural frequency
are calibrated. In one aspect of the present disclosure, the calibration of the damping
ratio and the natural frequency is done by the flow control valve 56.
Referring now to FIGS. 1, 7 and 8, a method 300 of calibrating the
damping ratio and the natural frequency using the flow control valve 56 will be

described. In step 302, a cycle counter N is set to an initial value, such as 1. As the
flow control valve 56 includes integrated pressuresensors 70, the flow control valve
56 receives signals from the pressure sensors 70 in step 304. The flow control valve
56 records the pressure when the pressure signal is at its highest value (peak)
and the time at which the peak pressure PHI,I occurs in step 306. The flow
control valve 56 also records the pressure when the pressure signal is at its
lowest value (trough) and the time tLO,,i at which the pressure PLo,i occurs in step
308.
In step 310, the cycle counter N is indexed (N=N+1) when the
pressure is at its next peak value. In step 312, the cycle counter N is compared to a
predefined value. If the cycle counter N equals the predefined value, the flow
control valve 56 records the pressure PHI,2 when the pressure signal is at its highest
value (peak) for that given cycle and the time at which the peak pressure PH1,2
occurs for that given cycle in step 314. The flow control valve 56 also records the
pressure when the pressure signal is at its lowest value (trough) for that given
cycle and the time at which the pressure occurs for that given cycle in step
316.
In step 318, the natural frequency is calculated. The natural
frequency can be calculated for small damping systems where the vibration is
typically large using the following equation:


Referring again to FIGS. 1 and 7, with the damping ratio and natural
frequency calculated for a given actuator 58 position, the actuator 58 is moved to a
second position in step 208 and the damping ratio and the natural frequency
are determined for that actuator position using steps 204-206.
While the damping ratio and natural frequency are only calibrated at
discrete actuator positions, interpolation can be used to determine the damping ratio
and natural frequency for actuator positions other than these discrete actuator
positions. In one aspect of the present disclosure, linear interpolation can be used.
Various modifications and alterations of this disclosure will become
apparent to those skilled in the art without departing from the scope and spirit of this
disclosure, and it should be understood that the scope of this disclosure is not to be
unduly limited to the illustrative embodiments set forth herein.

we claim
1. A method for controlling a boom assembly, the method comprising:
providing a boom assembly having an end effector, the boom assembly
including an actuator that is in fluid communication with a flow control valve;
converting a desired coordinate of the end effector of the boom assembly
from Cartesian space to actuator space;
calculating a deflection error of the end effector based on a measured
displacement of the actuator;
calculating a resultant desired coordinate based on the desired coordinate and
the deflection error;
generating a control signal based on the resultant desired coordinate and the
measured displacement of the actuator;
shaping the control signal to reduce vibration of the boom assembly; and
transmitting the shaped control signal to the flow control valve.
2. The method of claim 1, wherein the control signal is shaped using a time-
varying input shaping scheme.
3. The method of claim 2, wherein the time-varying input shaping scheme
includes two impulses.
4. The method of claim 1, wherein a first coordinate transformation converts
the desired coordinate from Cartesian space to joint space and a second coordinate
transformation converts the desired coordinate from joint space to actuator space.
5. The method of claim 4, wherein the deflection error is provided in joint
space coordinates.
6. The method of claim 1, wherein the shaped control signal is given by:


7. The method of claim 1, wherein the actuator sensor is a laser sensor.
8. The method of claim 1, wherein the actuator sensor is an absolute angle
encoder.
9. A work vehicle comprising:
a boom assembly having an end effector;
an actuator engaged to the boom assembly,, wherein the actuator is adapted to
position the boom assembly;
an actuator sensor adapted to measure the displacement of the actuator;
a flow control valve being in fluid communication with the actuator;
a controller being in electrical communication with the flow control valve,
the controller being adapted to actuate the flow control valve in response to an input
signal, wherein the controller includes a motion control scheme that includes:
a coordinate transformation module that converts a desired coordinate
of the end effector of the boom assembly from Cartesian
space to actuator space;
a deflection compensation module that calculates a deflection error of
the end effector based on measurements from the actuator
sensor;
an axis control module that generates a control signal based on the
desired coordinate, the deflection error and the measurements
from the actuator sensor; and
an input shaping module that shapes the control signal transmitted to
the flow control valve to reduce vibration of the boom
assembly.
10. The work vehicle of claim 9, wherein the work vehicle is an aerial work
platform.
11. The work vehicle of claim 9, wherein the end effector is a work platform.

12. The work vehicle of claim 9, wherein the flow control valve includes a
plurality of pressure sensors that are integrated into the flow control valve.
13. The work vehicle of claim 9, wherein the input shaping module is a time-
varying input shaping scheme.
14. The work vehicle of claim 13, wherein the time-varying input shaping
scheme includes only two impulses.
15. The work vehicle of claim 13, wherein the time-varying input shaping
scheme estimates the damping ratio and natural frequency of the boom assembly
based on measurements from the actuator sensor.
16. The work vehicle of claim 15, wherein the flow control valve determines a
damping ratio function and a natural frequency function used to estimate the
damping ratio and natural frequency.
17. A method of calibrating the damping ratio and the natural frequency of a
boom assembly using a flow control valve, the method comprising:
receiving pressure signals from pressure sensors regarding pressure in an
actuator;
recording high and low pressure values and times associated with those
pressure values for a first cycle;
recording high and low pressure values and times associated with those
pressure values for a second cycle; and
calculating natural frequency and damping ratio based on the pressure values
and times associated with those pressure values for the first and second cycles.
18. The method of claim 17, wherein the pressure sensors are integrated in the
flow control valve.
19. A method for shaping a control signal for a flexible structure, the method
comprising:
generating a control signal based on a desired coordinate;

shaping the control signal using a time-varying input shaping scheme,
wherein the time-varying input shaping scheme:
receives a measurement from a sensor;
estimates a natural frequency and damping ratio of the flexible
structure based on the measurement of the sensor; and
. shapes the control signal based on the measurement and the estimated
natural frequency and damping ratio.
20. The method of claim 19, wherein the control signal is based on a resultant
desired coordinate that accounts for deflection errors associated with the flexible
structure.

A method for controlling a boom assembly (20) includes
providing a boom assembly having an end effector (38).
The boom assembly includes an actuator (22, 34) in
fluid communication with a flow control valve. A
desired coordinate of the end effector of the boom
assembly is converted from Cartesian space to actuator
space. A deflection error of the end effector based on
a measured displacement of the actuator is calculated.
A resultant desired coordinate of the end effector is
calculated based on the desired coordinate and the
deflection error. A control signal for the flow control
valve is generated based on the resultant desired
coordinate and the measured displacement of the
actuator. The control signal is shaped to reduce
vibration of the boom assembly. The shaped control
signal is transmitted to the flow control valve.