Mitsubishi MR-508XL Spezifikationen PDF herunterladen (Seite 30)

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Bimba Position Control System

Model PCS

The Bimba Position Control System (Model PCS) is

designed to control any pneumatic Bimba position

feedback actuator. This includes series PFCN, PFCNL,

PFC, and PFCL for linear motion, and the Position

Feedback Pneu-Turn (PTF) for rotary motion. The sys-

tem is a closed-loop electronic controller with pneu-

matic valves that can accurately position the actuator

rod or shaft and hold it in position with a high degree

of accuracy and force. The system uses pneumatic

technology to accurately stop and hold the rod or shaft

at any desired position.

The standard PCS accepts a 0-10 V DC or 4-20 mA

analog command signal (jumper selectable). The com-

mand signal is used as a reference to move to and

hold a specific position. For example, if the application

has a stroke of 10 inches (i.e., the electrical zero and

span is set for a 10 inch stroke), then a 1 volt change in

the command voltage is equal to a 1 inch movement.

Similarly, a change in command signal of 0.005 of a

volt equals a position change of 0.005 of an inch for the

same 10 inch stroke application. If the application has

a stroke of 5 inches, a change of 1 volt in the command

signal represents a

⁄

inch movement. For rotary ap-

plications, the convention is similar. If the application

has a rotation of 180 degrees, then a 1 volt change in

the command signal is equal to 18 degrees of rotation.

The system utilizes the feedback from the actuator to

close the control loop. The control loop compares the

system’s command signal (the 0-10 V DC or 4-20mA

input command signal) to the feedback signal from

the actuator. The difference between the command

and feedback is referred to as the error term. When

the error term is zero, all valves close, trapping air on

both sides of the actuator piston. (The error term is

considered to be zero when it is within the deadband

range. The deadband range is an adjustable range that

determines the final repeatability of the system. The

Application Sizing chart located in our Full Line Catalog

shows recommended deadband ranges for given ap-

plication parameters.) This holds the rod or shaft at it's

commanded position. If some force or weight attempts

to move the rod or shaft out of the commanded posi-

tion, the system will react by increasing the restoring

force eventually to full supply pressure, if necessary.

Likewise, if the command signal changes, the system

will respond to make the feedback equal the command

signal.

There are four adjustments on the PCS system, adjust-

able via four trim pots. They include the Zero, Span,

Decel, and Deadband adjustments. The Zero and Span

adjustments allow you to set the zero and full scale

position of the actuator to match the input (command)

signal. The Decel and Deadband adjustments are used

to optimize the performance of the system based on

application parameters. These adjustments are de-

scribed in detail in the Operating Manual, which is

included with each system.

The actual accuracy and repeatability of the move-

ments will depend on many factors, including signal

noise, load, velocity, supply pressure, supply voltage,

and application friction.

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