DEVICE AND METHOD FOR CONTROLLING A FLUID ACTUATOR
TECHNICAL AREA
[0001] A hydraulic actuator control device for implementing a distributed control
architecture for regulating the performance of one or more hydraulic actuators according to
command signals from a single, on-board, user programmable microprocessor.
PRIOR ART
[0002] A device for controlling a hydraulic actuator is disclosed in DE 195 30 935 C2.
Disclosed in this reference is a displacement sensor for indicating the position of the valve
piston with an electrical signal which is supplied to a position controller. The controller for
controlling the position of the valve piston is arranged in its own housing, which is mounted
on the housing of the valve. The controller ensures that the valve piston follows a position
set point, which is supplied to the controller as an electrical input variable. In this case, the
position of the valve piston determines the magnitude of the passage cross-section of the
valve to control fluid flow to and from an actuator such as a hydraulic cylinder.
[0003] U.S. Pat. No. 6,901,315 to Kockemann discloses a controller device for controlling a
hydraulic actuator which includes an electrically operated hydraulic control valve that
controls the flow of a pressure medium in the actuator in response to the signals generated by
three separate controllers. The first controller regulates the position of a piston in the control
valve. The second controller commands movement of the actuator (such as a hydraulic
cylinder). And a third controller electronically controls a sequence of movements of the
actuator. The three controllers are arranged in a common housing which is mounted on the
control valve. The first and second controllers are pre-programmed by the manufacturer of
the control device. In this device, only the third controller can be freely programmed by the
user. This prior art device does not allow the user to program the second controller with a
state feedback control algorithm for controlling the hydraulic actuator. Also, in this prior art
device, there is no capability to control slave actuators using a user programmed state
feedback control algorithm in the device as disclosed and claimed. Also, in this prior art
device, there is no capability to receive and process the input from a variety of external
sensors or devices such as slave valves. Also, in this prior art device, all controllers are

comprised of separate micro-processors or electrical circuits rather than being integrated into
a single micro-controller.
[0004] The prior art control architecture, hereafter referred to as a "centralized control
architecture", consists of a single PLC that is responsible for coordinating the movements of
all hydraulic axes. This necessitates the need of all sensor signals to be routed to the single
machine PLC. This also necessitates the need for this single PLC to simultaneously run
several state feedback, closed-loop control algorithms for all of the hydraulic axes. The
single machine PLC then sends a command or manipulation to each hydraulic control valve.
The drawbacks of the prior art centralized control architecture are that it results in significant
cost to route cabling throughout the machine and significant wiring complexity in the PLC
panel. Furthermore a costly, high end PLC is required to simultaneously coordinate all of the
hydraulic axes and run the several state feedback control algorithms at a sufficient control
rate to achieve required dynamic performance of each hydraulic axis.
[0005] Also in the prior art as an improvement to a "centralized control architecture" is
where the analog interfacing of all sensors and control valves with the PLC has been replaced
by a field bus or network in some prior art installations. This installation can reduce cabling
cost and wiring complexity because several nodes can be connected to the PLC in a ring
topology. The drawback to this variation of a centralized control architecture with digital
communication between nodes and PLC is that control update rates are now limited by the
bandwidth of the field bus or network. Considering that all nodes need to continuously
broadcast their feedback values in the form of 8 to 16 bit words and considering that the PLC
needs to continuously broadcast manipulations to the control valves in the form of 8 to 16 bit
words means that the rate at which information can be transferred is limited by the constant
bandwidth of the field bus or network. The end result is that the performance of the hydraulic
axis suffers from the latency of manipulations received from the central controller.
SUMMARY
[0006] The solution to these problems is to employ a "distributed control architecture" of the
type disclosed in this application where the state feedback control algorithm for each
hydraulic axis is executed locally on the hydraulic valve controlling that specific axis. The
advantage of the "distributed control architecture" is that the sensors can be connected
directly to the relevant hydraulic control valve and no longer take up valuable bandwidth on

the field bus or network. Furthermore, the hydraulic control valve can generate its own
command trajectory locally rather than needing to receive it from the central PLC which
further reduces data transfer on the network or field bus. Since state-feedback control
algorithms are embedded on the microprocessor of the hydraulic controller 10, the control
instructions can be executed and a much higher rate thereby significantly improving the
dynamic performance of said hydraulic axis. Lastly, the responsibilities of the central PLC
get significantly simplified allowing the use of a less complex and lower cost unit. The new
central computer becomes a supervisory PLC that coordinates the movements of each
hydraulic axis but no longer needs to continually monitor and continually manipulate each
hydraulic axis. Instead the supervisory PLC would transmit a "Start Profile" bit to a
distributed controller. The distributed controller would receive this "Start Profile" bit, then
execute its profile then respond with a "Profile Complete" bit. The new supervisory PLC
would monitor the state and fault status of each distributed controller and take appropriate
action if any distributed controller raises a fault flag. The network or field bus
communication traffic in a distributed control architecture gets reduced from the continuous
broadcast of digital sensor words and digital manipulation words to the periodic broadcast of
state and fault bits.
[0007] In addition, the configuration of the exemplary hydraulic control system allows the
micro processor based control algorithms to be programmed by the user and not exclusively
by the manufacturer. This permits more flexibility in programming and protects the
intellectual property of the user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic illustration of the exemplary fluid control device connected to a
hydraulic actuator;
[0009] FIG. 2 is a schematic illustration showing the arrangement of the modules in the
control circuit board and various inputs and outputs;
[0010] FIG. 3 is a schematic representation of the exemplary fluid control device connected
to a series of slave actuators;

DETAILED DESCRIPTION
[00111 Referring now to the discussion that follows and also to the drawings, illustrative
approaches to the disclosed systems and methods are shown in detail. Although the
drawings represent some possible approaches, the drawings are not necessarily to scale
and certain features may be exaggerated, removed, or partially sectioned to better illustrate
and explain the present disclosure. Further, the descriptions set forth herein are not
intended to be exhaustive or otherwise limit or restrict the claims to the precise forms and
configurations shown in the drawings and disclosed in the following detailed description.
[0012] Moreover, a number of constants may be introduced in the discussion that follows. In
some cases illustrative values of the constants are provided. In other cases, no specific values
are given. The values of the constants will depend on characteristics of the associated
hardware and the interrelationship of such characteristics with one another as well as
environmental conditions and the operational conditions associated with the disclosed system.
[00131 PIG- 1 shows a schematic view of a control device 10 for controlling a hydraulic
actuator 12. A housing 14 is mounted to a hydraulic control valve 16. The control valve 16
is illustrated as a perspective view from the side. The control valve 16 controls the flow of
working fluid such as hydraulic oil, that is pressurized from a pump 18, through the control
valve 16 and ultimately to a hydraulic actuator 12 and back from the actuator 12 to a return
tank 20. In the exemplary embodiment, the actuator 12 is a hydraulic cylinder which, in
FIGS. 1, 2 and 3, is illustrated as a double-ended cylinder but could be any type of suitable
actuator. For example, the actuator 12 may be a differential cylinder or a hydraulic motor.
The hydraulic hose or tube connections from the control valve 16 to the actuator 12 are
designated by the pump connection P for connection to the pump 18, tank connection T for
the connection from the control valve to the tank 20 and A and B for the hose or tube
connections from the control valve to the double-ended cylinder actuator 12. A displacement
sensor 28 for measuring the position x of a shuttle or a spool valve (not shown) or other type
of valving device is contained within the control valve 16. The displacement sensor 28 is
connected into the controller circuit board 26 which converts the position x of the valve
piston into an electrical signal xi which, in the controller 11 is processed and supplied as the
processed position of the actual value of the spool position.. The software functionalities
within the microprocessor 32 together with input and output interfaces and other features of
the controller 11 are discussed in more detail with regard to FIG. 2.

[0014] Now again referring to FIG. 1 of the drawings, a schematic illustration of the
exemplary hydraulic control device 10 hydraulically connected to a hydraulic actuator 12 is
shown. A housing 14 containing a controller 11 is mounted to a hydraulic control valve 16.
The control valve 16 is illustrated in a perspective view from the side. The control valve 16
controls the flow of pressurized hydraulic oil or other working fluid from a pressure pump 18
through pressure line P to the hydraulic actuator 12 and back to a holding tank 20 via tank
line T. In FIG. 1 the hydraulic actuator 12 is shown as a double acting hydraulic actuator
having an output shaft 22 which is driven in one direction and in the opposite direction by
pressurized fluid acting on either side of a piston 24 which is connected to the output shaft 22.
Internally, the control valve 16 contains at least one high speed electromagnetic actuator (not
shown) which receives and reacts to signals from the controller 11 to position the spool
within control valve 16. The control valve 16 can use staged spool valves where a first spool
valve is used to control the flow of pressurized hydraulic fluid to a second spool valve and so
on, until the final stage controls the flow of pressurized hydraulic oil to an actuator such as a
cylinder or motor where in FIG. 1 a cylinder actuator 12 is shown.
[0015] Referring again to FIG. 1, shows the block circuit diagram of the controller 11
illustrated in FIG. 1 for controlling the double-ended cylinder 12. The controller 11 for
controlling the position x of the control valve and consequently the position of the piston of
the actuator 12 is supplied with the output signal xi from the displacement sensor 28 as actual
value, and a set point xs, as input signals to the controller 11 using this signal along with a
position or pressure signal from the actuator 12 to provide a closed loop control system for
controlling the performance of the actuator 12.. The output stage of the controller 11
supplies the coils of the electromagnetic actuators contained in the control valve 16 with the
currents ia and ib, which serve to position the spool to control the flow of pressurized
hydraulic oil or other pressurized fluid to the actuator 12 through fluid lines A and B so as to
move the actuator piston 24 so as to assume the position predefined by the signal xs in order
that the actual value of the position of the actuator piston 24 or piston rod 22 follows its
desired set point as quickly as possible. Importantly, the controller 11 is based upon a micro-
chip or micro- controller 32 that is freely programmable by a user via the communication line
48 or 34 which can be also programmed by the manufacturer if desired.
[0016] The fluid connections A and B between the valve actuator 16 and the double-ended
cylinder 12 are connected via commonly used hydraulic connection lines and fittings. The
piston rod 22 of the double ended cylinder 12 is provided with a displacement sensor 23

which converts the position of the piston rod 22 into an electrical signal si Cp. The signal si
Cp is supplied to the controller 11 and specifically to the microprocessor 32 as an actual
position value. By differentiating the signal xi Cp, the actual value of the speed of the piston
rod 22 of the double ended cylinder actuator 12 can be obtained as required for speed control
if required. Pressure sensors 25 integral to the control valve 16 measure the pressure in the
work port lines A and B as well as in the interface lines P and T and supply signals Pa, Pb, Ps,
and Pt to the controller 11. In addition to the signals Pa, Pb, Ps, and Pt the controller 11 is
supplied with the actual value xi of the position of the valve piston from the position sensor
28. From the weighted pressure difference between the signals Pa and Pb an actual pressure
value pi which is also a measure of the force acting on the piston rod 22 of the double ended
cylinder actuator 12 can be calculated. Interface pressures Ps and Pt can also be used in
conjunction with port pressures Pa and Pb and with valve piston position xi to calculate the
flow into or out of the cylinder actuator 12. The controller 11 is constructed as a single
microprocessor 32 and is part of a closed loop digital control system. The microprocessor 32
is therefore capable of processing the algorithms of the pressure or flow control to ultimately
control the fluid pressure supplied to the cylinder actuator 12 in addition to the algorithms for
the position control of the piston rod 22 of the cylinder actuator 12. Instead of the position
control described, speed control, force control or pressure control can also be implemented by
the digital controller 11. The device provides a platform for the end user to program their
own state feedback control algorithms and their own sequencing logic and command profiles
directly into the single microprocessor 32. Alternatively this control software can be
programmed by the manufacturer. In addition to the position control described any other
application control conceivable to the user can be programmed into the controller 11
including but not limited to:
• pQ pump control
• pQ cylinder control
• Load sensing pump control
• Single axis control
• Pressure and temperature compensated flow control
• Pressure control
• Synchronous axis control (master/slave)
• Twin spool Meter in / Meter out control (master/slave)
• Parallel flow control
• Control of safety shutoff(s)
• Prognostics & Diagnostics (valve and machine related)

[0017] The controller 11 is centered around the microprocessor 32 which is a freely
programmable sequence controller with NC and/or PLC functionality. In this case, NC is the
designation used in machine control systems for "numeric control", and PLC is the
designation used for "programmable logic controllers". The microprocessor 32 also provides
a platform for freely programmable state feedback control algorithms. The programming of
the microprocessor 32 can be carried out by the user to protect the intellectual property of the
user from outside entities. Many OEM's that utilize hydraulic valves to control hydraulic
axes on machines want to protect, their intellectual property in the area of hydraulic axis
control. They consider the control of the hydraulic axis to be their core competency and
competitive advantage against other machine manufacturers. The hydraulic control system
10 claimed herewith provides a platform for the end user to program their own control logic
and state command profiles and state feedback algorithms and therefore, provides the
machine manufacturer with the ability to protect their IP.
[0018] In addition to providing a freely programmable platform, the hydraulic control system
claimed herewith also enables a "distributed control architecture" for multi axis control. On a
typical machine there are several hydraulic axes that need to be controlled simultaneously.
The current state of the art control architecture, hereafter referred to as a "centralized control
architecture", consists of a single PLC that is responsible for coordinating the movements of
all hydraulic axes. This necessitates the need of all sensor signals to be routed to the single
machine PLC. This also necessitates the need for this single PLC to simultaneously run
several state feedback, closed-loop control algorithms for all of the hydraulic axes. The
single machine PLC then sends a command or manipulation to each hydraulic control valve.
The drawbacks of a centralized control architecture are that it results in significant cost to
rout cabling throughout the machine and significant wiring complexity in the PLC panel.
Furthermore a costly, high end PLC is required to simultaneously coordinate all of the
hydraulic axes and run the several state feedback control algorithms at a sufficient control
rate to achieve required dynamic performance of each hydraulic axis.
[0019] As an improvement to a "centralized control architecture" the analog interfacing of all
sensors and control valves with the PLC has been replaced by a fieldbus or network in some
installations. This installation can reduce cabling cost and wiring complexity because several
nodes can be connected to the PLC in a ring topology. The drawback to this variation of a
centralized control architecture with digital communication between nodes and PLC is that
control update rates are now limited by the bandwidth of the fieldbus or network.

Considering that all nodes need to continuously broadcast their feedback values in the form
of 8 to 16 bit words and considering that the PLC needs to continuously broadcast
manipulations to the control valves in the form of 8 to 16 bit words means that the rate at
which information can be transferred is limited by the constant bandwidth of the fieldbus or
network. The end result is that the performance of the hydraulic axis suffers from the latency
of manipulations received from the central controller.
[0020] The solution to these problems is to employ a "distributed control architecture" where
the state feedback control algorithm for each hydraulic axis is executed locally on the
hydraulic valve controlling that specific axis. The advantage of the "distributed control
architecture" is that the sensors can be connected directly to the relevant hydraulic control
valve and no longer take up valuable bandwidth on the fieldbus or network. Furthermore, the
hydraulic control valve can generate its own command trajectory locally rather than needing
to receive it from the central PLC which further reduces data transfer on the network or
fieldbus. Since state-feedback control algorithms are embedded on the microprocessor 32 of
the hydraulic controller 10, the control instructions can be executed and a much higher rate
thereby significantly improving the dynamic performance of said hydraulic axis. Lastly, the
responsibilities of the central PLC get significantly simplified allowing the use of a less
complex and lower cost unit. The new central computer becomes a supervisory PLC that
coordinates the movements of each hydraulic axis but no longer needs to continually monitor
and continually manipulate each hydraulic axis. Instead the supervisory PLC would transmit
a "Start Profile" bit to a distributed controller. The distributed controller would receive this
"Start Profile" bit, then execute its profile then respond with a "Profile Complete" bit. The
new supervisory PLC would monitor the state and fault status of each distributed controller
and take appropriate action if any distributed controller raises a fault flag. The network or
fieldbus communication traffic in a distributed control architecture gets reduced from the
continuous broadcast of digital sensor words and digital manipulation words to the periodic
broadcast of state and fault bits.
[0021] Now referring to FIG. 2, a schematic illustration showing the arrangement of modules
in the control circuit board and various inputs and outputs are shown. The controller 11 has a
first interface 113 to a global bus system 34 via which the control device 10 is connected to a
higher order controller such as a supervisory PLC 60. The controller 11 has a second
interface to a local bus system 33. Further devices and sensors for controlling additional
cylinders or other actuators in each case are connected to this bus system 33 which can be

through a network or field bus interface 113 as illustrated in FIG. 2. The bus systems 33 and
34 are connected to the circuit board 26 as illustrated in FIGS. 1. and 2. By replacing a
circuit board component such as the network bus interface 113, the control device 10 can be
connected in a simple way to different bus or network systems.
[0022] The controller 11 is connected to the supervisory PLC 60 via the global bus system 34.
In this global bus system 34 the Supervisory PLC 60 is designated as the "master" and the
valve controller 11 is designated as a "slave". A second bus system, designated as the local
bus system 33, is provided for use when a hydraulic axis must be controlled by two or more
hydraulic actuators 12B and hydraulic control valves 50. An example of this is in a press
application where two hydraulic cylinders must follow an identical trajectory parallel to each
other. In this case the controller 11 would be designated as a master and a second hydraulic
control valve 50 would be designated as a slave node on the local bus system 33. The
controller 11 would be responsible for controlling its own hydraulic control valve 10 and
controller 11 would also be responsible for controlling the second hydraulic control valve 50.
The local bus system is for example a CAN bus via the local bus 33. It connects the devices
and possible further devices having proper communication capability to one another since the
local and global bus 33, 34 permit the exchange of data between a plurality of devices. This
exchange of data between the global bus system 34 and the local bus system 33 is enabled by
the Expanded Object Dictionary Database 124. Via this data exchange, for example,
synchronous control of the piston rods of two actuator cylinders can be implemented. The
global bus system 34 connects the devices to the higher order controller such as the
supervisory computer 60. It is used for communication between the individual devices and
the supervisory computer 60. In FIG. 2, the supervisory computer 60 is illustrated as a
programmable logic controller (PLC) but can also be implemented by a PC. Via the global
bus system 34, the supervisory computer 60 can be supplied with the different actual values
from the actuator 12, or from sensor data contained in the object dictionary database 124, or
control valve state information or fault bits or diagnostic data for monitoring or control
purposes.
[0023] The pressurized hydraulic fluid such as hydraulic oil, enters the actuator 12 through
either hydraulic lines A and/or B whose flow rate and pressure is in response to the motion of
the spool valve (not shown) in the control valve 16 based on a variety of sensor inputs and
desired movement commands using algorithms supplied by either the manufacturer, the user
or some third party provider. The controller 32 can be connected to a global or a local digital

communication system or both. The global or local digital communication system can be a
field bus such as a CAN or a network such as Ethernet. Connectors 33 and 34 are the shown
illustrations of the electrical connections to the local and the global digital communication
system respectively. Also illustrated are electrical connections 48 and 46 where the
connector 48 can be used to flash program the microprocessor 32 and connector 46 can be
connected to a variety of external sensors 42 such as displacement, pressure, temperature, or
vibration sensors. Another approach to transfer external sensor data into the controller 11 is
through a serial communication line using a system such as multiplexing to encode and then
decode the serially sent sensor values using the microprocessor 32 or a separate
communications device such as the A to D 123 or the SSI interface 126 shown in FIG, 2.
[0024| Now again referring to FIG.2 of the drawings, an illustrative diagram of the controller
11 of the exemplary control device 10 is shown. The on-board application controller 103 is
shown contained within the dashed box drawn in Fig. 2 and includes both a processor section
102 that handles the state feedback application control algorithm and a sequencing logic
section 104 that handles both the sequencing logic and CNC command profiles.
[0025] In the exemplary control device 10, a software platform is provided so the application
control algorithm can be programmed by the user but could instead be programmed by the
manufacturer. The software platform also allows the user to program the sequencing logic
and CNC profiles or can instead be programmed by the manufacturer.
[0026] The exemplary hydraulic control devices 10 use a cascaded control architecture
whereby the Sequencing Logic and NC controller 104 operates at the highest level. This
controller's function is to receive "start profile" commands from the supervisory PLC 60 and
transmit "profile complete" status to the supervisory PLC 60. The Sequencing Logic and NC
controller 104 can also transmit other various status words to the supervisory PLC 60 such as
the current state of the state machine or diagnostic or fault information. Lastly the
Sequencing Logic and NC controller 104 provides the command profile and sequencing
information to the next lower controller in the cascade which is the Application State
Feedback controller 102.
[0027] The Application Controller 103 has read/write access to the Object Dictionary
Database 124. This database is a repository for fetching sensed data written to it by the A/D
123 or SSI Interface 126. This database 124 is also a repository for storing status information
to be broadcast by the network/fieldbus interface 113. The next lower controller in the
cascade is the Application State Feedback controller 102. This controller's function is to

execute software instructions at a rapid, fixed sample rate to execute real-time, state feedback
control algorithms. The Application State Feedback controller 102 receives its command
trajectory from the Sequencing Logic and NC controller 104 and receives the sensed state
feedback parameters via the Object Dictionary Database 124. Based on these commands and
feedbacks the Application State Feedback controller 102 calculates a manipulation to be
passed to the next lower controller in the cascade. The Application State Feedback controller
102 can be programmed by the user or it can be pre-programmed by the manufacturer. The
next1 lower controller in the cascade can be the control valve piston position controller 114 or
the Control Valve Actuator Current Controller 116 or the Control Valve Actuator PWM
controller 112. This selection is software selectable by the application controller 103 via a
"Control Mode" parameter in Object Dictionary Database 124. This software selection of
Control Mode is depicted as switch 110 in FIG 2.
[0028] The position of switch 107 is selected by the processor section 102 such that either the
flow controller 106 is connected to the switch 110 or the pressure controller 108 is connected
to the switch 110. The control valve piston position controller 114 contains software logic to
calculate and generate a current command based on the error between commanded piston
position and actual piston position xi. This signal is transmitted to the current controller 116.
The current controller 116 generates a PWM command signal based on the error between
commanded current and sensed actuator current ia or ib. The PWM signals are sent to a
Pulse Width Modulated (PWM) current driver 112. The PWM current driver 112 generates
current ia and ib that is sinked through Electromagnetic Valve Actuator A 118 and B 120 to
exert forces to move the control valve piston. The Electromagnetic Valve Actuators 118 and
120 determine the position of the control valve piston which in turn, controls the flow of
pressurized hydraulic oil to the hydraulic actuator 52.
[0029] As an example, the Sequencing Logic and NC controller 104 would call either the
flow control state feedback controller 106 or the pressure control state feedback 108
controller based on user programmed logic 104 to execute a pQ control application
commonly used on injection molding machines. The Sequencing Logic and NC controller
104 would provide the selected state feedback controller with the user programmed flow
command profile or pressure command profile while in said operating state. The output of
the selected state feedback controller would be a manipulation to 114 116 or 112 based on the
state of switch 110 to ultimately position the control valve spool.

[0030] In a like manner, additional hydraulic actuators could be controlled by the Application
Controller 103 via slave valves 50 on the local field bus. If desired either the position
controller 114 or the current controller 116 or both can be eliminated from the processing
chain using a "software switch" through the selection of "Valve Control Mode" in the in the
Object Dictionary Database 124. The state of this "software switch" as depicted as item 110
in Fig 2 is controlled by the application controller 103. Using this mechanism the control
signal generated by the application controller 104 can be fed to the Postion Controller 114 or
to the Current Controller 116 or directly to the PWM Current Driver 112.
[0031] To coordinate the high level motion of one distributed hydraulic axis 12A and 12B
with other distributed hydraulic axes on the machine, a supervisory PLC computer 60 is
connected to the global network bus line 34 which is in turn connected to the application
controller 103. The user can program the application controller 103 to command the desired
motion or performance of the hydraulic axis as directed by the supervisory PLC 60. The
application controller 103 then generates a required control signal which is transmitted to the
downstream controllers in the cascade 112, 114, 116 and to a slave hydraulic control valve 50
via the local bus network connection 33 in the case of synchronous axis control. Two
actuators are shown in this example although one or a plurality of actuators could be used
with the exemplary system.
[0032] The motion of the actuators 12A and 12B are of a closed loop control through use of
the application controller 103 where a selection of sensors is used to provide the closed loop
control input. Shown in FIG.5 1, item 25 and in Fig 2 item 130 are pressure sensors
comprised of sensors Pa and Pb for the measurement of the work port pressures from the
control valve 10 to its respective actuator 12. Pressure sensor Ps measures the pressure of the
high pressure fluid supply line and pressure sensor Pt measures the fluid level in a return tank
(not shown). Sensor Vp measures the position of a second stage control valve spool (not
shown) while sensor Cp measures the position of the hydraulic actuator piston 12. It is
recognized that to provide maximum flexibility for a user to program their own control logic
and algorithms into the application controller 103 that additional sensor data may be required.
For this purpose an external sensor interface 125 has been provided to pass externals sensor
data into the controller 11. This external sensor data becomes available to the application
controller 103 through read access to the Expanded Object Dictionary Database 103.
[0033] An expanded object dictionary 124 is connected to the A to D 123, to the network bus
interface 113 to the application controller 103 and to an SSI interface 126. The SSI interface

126 acts to pass signals from external digital sensors (not shown) to the object dictionary 124
unlike the A to D 123 which digitizes signals from external analog sensors 130. The object
dictionary 124 can include information and other data such as calibration settings, sensor
parameters, diagnostic flags, control algorithm parameters, gain tables, signal thresholds and
dead bands.
[0034] Now referring to FIG. 3 of the drawings, a schematic illustration of the controller 17
connected to a series of slave actuators is shown. A circuit board 11 contains a variety of
electronic components such as a microprocessor 32 and interface modules. The local
communication signal line 33A is connected to the local communication field bus or network
such as a CAN bus or Ethernet network. The global communication signal line 34 is
connected to a global communication field bus or network such as CAN or ethernet. The
microprocessor 32 can be an Application Specific Integrated Circuit (ASIC) microchip or a
similar device that provides the signal processing and algorithm support required to generate
a variety of signals such as the control signal that is sent to the hydraulic control valve 16 and
the slave hydraulic control valves 50A and 50BA variety of hydraulic control valves are
shown in FIG. 3 connected to controller 11 as nodes 50A and 50B on a bus or network
communication system 33. Controller 11 is designated as the "master" and the additional
hydraulic control valves are designated as slaves. Each hydraulic control valve 10, 50A and
50B is also connected to a cylinder actuator 12A, 12B, and 12C via hydraulic connections.
Each cylinder actuator is instrumented with a sensor 23A, 23B, and 23C for sensing the
position and/or speed of the actuator piston. Each actuator sensor is connected to the
controller 11 via interface 56A, 56B, and 56C. Interface 56A, 56B, and 56C can be an analog
interface or a digital interface such as SSI or a discrete interface such as output by and
encoder. The actuator sensors 23A, 23B, and 23C can also be interfaced to the controller 11
as additional slave nodes on the local network or bus system 33. In this fashion controller 11
can control the hydraulic actuator 12A controlled by the hydraulic control valve 10 that
controller 11 resides within and one or more additional hydraulic actuators 12B and 12C.
The control logic and state feedback algorithms for each hydraulic actuator can be
programmed into controller 11 by the user as described herein.
[0035] Now again referring to FIG. 3 of the drawings, a schematic illustration of the
exemplary hydraulic control system 11 is shown where the controller 17 is used to send
control signals to at least one slave control valve unit such as control valves 50A, 50B,. The
controller 17 is electrically connected to the local bus 33 which can be what is known as a

CAN bus which has been discussed previously. Electrical communication signals are sent
over the local bus 33 which is connected to each of the slave control valves 50A, 50B. The
signals sent are encoded so that the proper slave actuator 50A and 50B only responds to its
slave control signal. The slave control signal represents a variable such as a desired cylinder
position or control valve position or a pressure level or a force level, for example. The
variables associated with the performance of the slave actuators are transmitted by way of the
communication lines 56A, 56B and 56C which are connected to the sensor at each of the
actuators 23A, 23B, and 23B which sense movement of the hydraulic cylinders 12A, 12B,
and 12C. The signals from the sensors are then transmitted to the controller 17 where they
are processed and a new control signal is sent via the local bus line 33 to the control valves
10, 50A, 50B. The position of the hydraulic cylinders 12A, 12B, and 12C are transmitted to
the controller 17 through slave communication lines 56A, 56B and 56C. The amplitudes of
the signals produced by the sensors can be coded and multiplexed or the sensors such as the
actuator sensors 23 A, 23B, and 23B can be directly connected to the controller 17.
[0036J The controller 17 is electronically communicates with a central supervisory computer
60 which can be a PLC, through a global bus communication line 34. The supervisory
computer 60 can be programmed to regulate the master hydraulic control device 10' and in
turn, the performance of the slave actuators which respond to control signals generated by the
master control device 10' and specifically by the microprocessor 32. For example, the user
can program a request that the movement of the master and slave actuators 12A-C move in
sequence. The microprocessor 32, which has been flash programmed by the user, then
generates control signals that are sent to the master control valve 10 and to each of the slave
hydraulic control valves 50A and 50B to generate the desired motion of the actuators 12A,
12B and 12C. In this fashion a single controller 11 can work in a distributed control
architecture to control a distributed function on a machine requiring two or more hydraulic
control valves. Examples of distributed, multi-control valve functions include but are not
limited to the following applications:
• Synchronous axis control (master/slave)
• Twin spool Meter in / Meter out control (master/slave)
• Parallel flow control
• Distributed Control of safety shutoff(s)

[0037] The master hydraulic control valve 17 acts as a slave on the global network or
fieldbus interface 34 which is mastered by the supervisory PLC 60. The supervisory PLC 60
monitors and coordinates other distributed controllers on the machine such as 17, 17', 17".
[0038] This disclosure has been particularly shown and described with reference to the
foregoing illustrations, which are merely illustrative of the best modes for carrying out the
disclosure. It should be understood by those skilled in the art that various alternatives to the
illustrations of the disclosure described herein may be employed in practicing the disclosure
without departing from the spirit and scope of the disclosure as defined in the following
claims. It is intended that the following claims define the scope of the disclosure and that the
method and apparatus within the scope of these claims and their equivalents be covered
thereby. This description of the disclosure should be understood to include all novel and non-
obvious combinations of elements described herein, and claims may be presented in this or a
later application to any novel and non-obvious combination of these elements. Moreover, the
foregoing illustrations are illustrative, and no single feature or element is essential to all
possible combinations that may be claimed in this or a later application.

We claim:
1. A fluid control system having control algorithms for controlling the motion of an
actuator comprising:
a microprocessor containing all of the control algorithms which can be programmed
by a user;
a control valve for controlling the flow of a pressurized fluid to the actuator;
a valve position sensor connected to said control valve and generating a position
signal;
where the microprocessor generates a command signal that is transmitted to said
control valve which moves so as to allow pressurized fluid to enter the actuator to cause the
actuator to move thereby causing said valve position sensor to transmit a changed position
signal to said microprocessor for use in a closed loop control algorithm.
2. The fluid control system of claim 1 further comprising an analog to digital converter,
said analog to digital converter connected between an external sensor and said
microprocessor.
3. The fluid control system of claim 1 further comprising an SSI device, said SSI device
connected between an external sensor and said microprocessor.
4. The fluid control system of claim 1 wherein said microprocessor includes a
application control algorithm and a sequencing logic section.
5. The fluid control system of claim 1 further comprising a network bus interface for
communication with a supervisory controller and slave actuators.
6. A fluid actuator control system for a fluid actuator comprising:
A programmable microprocessor containing all of the control algorithms for regulating the
motion of said fluid actuator;

a control valve electrically connected to said microprocessor and hydraulically
connected to the hydraulic actuator;
a position sensor connected to said control valve for generating a position signal
indicative of the position of said control valve;
Said position sensor electrically connected to said microprocessor.
7. The fluid actuator control system of claim 6, further comprising a sensor
communication line where said communication line is connected to one or more sensors.
8. The fluid actuator control system of claim 6 where a working fluid is hydraulic oil.
9. The fluid actuator control system of claim 6 further comprising a local
communication bus connected to said microprocessor and connected to at least one external
sensor.
10. The fluid actuator control system of claim 6 further comprising a global communication
bus connected to said microprocessor and connected to a supervisory computer.
11. A method of controlling a fluid powered actuator comprising:
providing a controller, said controller including a programmable micro-processor;
providing a control valve electrically connected to said controller and hydraulically
connected to the fluid actuator control algorithm circuitry that is programmed into said
controller by a user.
12. The method of claim 11 further comprising providing an actuator sensor, said actuator
sensor being connected to the fluid powered actuator and electrically connected to said
controller where said controller generates a signal to said control valve to control the output
of said actuator sensor.
13. The method of claim 11 further comprising providing a valve position sensor
connected to said control valve, said valve position sensor generating a signal indicative of a
state of said control valve and providing a signal line connecting said valve position sensor
and said controller.

14. The method of claim 11 further comprising providing a local bus for communication
between said controller and at least one external sensor or slave actuator.
15. The method of claim 11 further comprising providing a global bus for communication
between said controller and a supervisory computer.
16. A hydraulic actuator control system for controlling the motion of a master actuator
and at least one slave actuator comprising:
an external supervisory computer for sending command signals;
a hydraulic control system connected to the master actuator and connected to said
supervisory computer, said control system including a microprocessor and a master hydraulic
control valve for controlling the flow of a pressurized fluid to said master actuator based on
said command signals; and
at least one slave actuator having at least one slave sensor connected to said
microprocessor and having at least one slave control valve for controlling the flow of
pressurized fluid to said slave actuator, where said slave control valve and said slave sensor is
controlled by said microprocessor.
17. The hydraulic actuator control system of claim 16 wherein said microprocessor
includes an application control algorithm that is programmable by a user.
18. The hydraulic actuator control system of claim 16 further comprising a network bus
interface connected to said microprocessor and connected to sakd said slave actuator.
19. The hydraulic actuator control system of claim 16 further comprising a flow controller
and a pressure controller where said microprocessor selects to use either said flow controller
or said pressure controller.
20. The hydraulic actuator control system of claim 16 further comprising an analog to
digital converter, said analog to digital converter connected to said microprocessor and to at
least one external sensor.