there are different types of control systems used in robotics
in open-loop control the computer send signals based on the current state
without taking into account feedback from the system
this type of system is also called non-server
or pick in place and is used in about 35 percent other robots
in the United States
open-loop control systems signals are percent by a computer controller
to the system driver
the system driver then can birch those signals into an operation for the
process
or robot to perform
the system driver can be anything from a pneumatic actuator
a hydraulic flow valve or an electrical controller
in open loop systems the program link that time the signal is applied
as well as the integrity other signal are critical for ensuring that the new
operation
is completed
this is because there is no feedback to the computer
from the system driver or the robot and thus
no updates to the signal outputs can be made
the term process in this illustration simply means
any piece of equipment that accomplishes work this could be a robotic arm
a motor oren engine for the purposes up this module
will focus on robots once the signal is received
the robot performs the appropriate action in an open-loop system the
signals that go from the computer to the system driver
to the robot are never checked with a feedback loop to ensure that the robot
has completed
its task
a simple example oven open-loop system is an industrial sprinkler system
in this example the programmer updates the computer controller
which will turn the sprinkler on at a designated time
when the computer sends the signal the water valve will turn on
when the Val turns on water flows to the sprinkler
and drives a motor that allows the sprinkler to simultaneously move along
the field
and water the crop
some good examples for open-loop control systems
are stopping go conveyor systems with constant loading
and manufacturing applications with high repeatability
and load variation such as punching holes at a piece of sheet metal
or reorienting work pieces
material handling and machine tending operations
also account for many open loop design applications
due to their lack of speed control and lack a flexible work positions
open-loop control is useful for well-defined systems
where the relationship between input and the resultant state can be modeled
the positions are the robot can be predetermined
and the loading environment does not change
open-loop control systems are typically low cost due to their simplistic design
high repeatability and controllers simplicity
they should be used where motion is predefined
repeatable and is not very
the second type up control system is called closed-loop control
or servo control a servo is a device that uses
error sensing feedback to control the motion another device
the primary difference in an open versus closed loop system
is the addition a feedback loop that allows the controller to make
adjustments
to the robot
our previous example have a sprinkler the system was open loop because the
controller received no feedback
but if I moisture sensor is added it becomes
a closed-loop system
the sensor measures the moisture density above the soil
and send that information back to the computer controller
the computer can then make adjustments to the quantity of water coming from the
sprinkler
the advantage is a closed loop control systems include flexible program control
ease up changing program two points the capacity for complex manufacturing tasks
and multiple program storage and execution capabilities
these flexible capabilities allow the same machine to utilize multiple
programs with different operations
based on the work being presented all without a change
in machinery closed-loop systems require a larger up-front capital investment and
highly skilled maintainers
but the pay back comes from a much larger range ok capabilities
closed-loop controllers are used in machining
welding coating and sealer application material handling
machine tending arc and waterjet cutting
inspection and assembly operations
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