Gilderfluke&Co Quad EFB Controller User Manual

GILDERFLUKE & CO. • 205 SOUTH FLOWER ST. • BURBANK, CALIF. 91502-2102 • 818/840-9484 • FAX[phone]

- OPERATINGINSTRUCTIONS-

- for -

- EFB-QUAD ELECTRONIC FEEDBACK CONTROLLER -

- PID-QUAD E

LECTRONIC FEEDBACK CONTROLLER -

- printed February 27, 2006 -

Animation movements come in two basic flavors: 1) Analog, and 2) Digital. Although
we are used to thinking of everything ‘digital’ being superior to anything analog (like
digital CDs vs. analog LP records), this is the one case where it just ain’t so 1. Analog
movements are used in almost all high-end animated figures. They give you a fluid,
lifelike motion that digitals just can’t do.

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Digital electronics are used to create most analog Animation Control Systems.

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GILDERFLUKE & CO. • 205 SOUTH FLOWER ST. • BURBANK, CALIF. 91502-2102 • 818/840-9484 • FAX[phone]

A Digital control is either off or on, just like a light switch. A typical digital animation
movement is at either one end of its travel or the other, or moving between these two
positions 2. The speed of the action is set by the flow controls that control how fast the air
(or oil) can get into and out of the cylinder.

An analog control is like the light dimmer on the wall of your dining room. It can be off,
on, or at any point in between. The rate at which it is moving (within the maximum flow
limitations of the valve) is controlled by how fast you are turning the knob. If you stop
turning the knob half way through the rotation, the movement will stop there too. An
analog movement will follow every nuance of how you turned that knob during
programming and will be able to repeat it exactly. If something tries to push an analog
away from where it was programmed to be, it will actually fight to get back to where it
belongs.

How does it do this? Unlike open loop controls (digital movements are almost always
open loops), the command signal to an analog movement does not control the valve
directly. Instead, the command signal goes to some sort of Electronic Feed Back (EFB)
card. Examples of these are our EFB-Quad, PID-Quad and BS-EFB. Here the command is
compared with the actual position of the movement as measured by a device that is
mounted on the movement (typically a potentiometer). If the movement is off by just a
little, the EFB card will open the valve by just a little to get it back into the proper position. If
the movement is off by a lot, then the EFB card will open the valve as needed until it starts
getting close to where it should be. It then ramps the valve fully closed as the final position
is reached to slow the movement smoothly to a stop.

Despite their added complexity, analog functions tend to be more reliable than digital
moves. The reason for this is simple. Their closed servo loop allows them to adjust
themselves (within limits) to compensate for cylinder wear, leakage and pressure
variations. They are also smoother than digital functions. With less banging into the end
stops of the cylinders, there is simply less wear and tear on the mechanics of the figure.
The two most common failures in an analog movement are a break in the wires leading
to the feedback pot on the cylinder or a clogged valve. A unique feature of all of our
Electronic FeedBack cards is the ability to sense wire breaks, sound an alarm and to turn
‘off’ the affected axis until help arrives.

So why aren’t analog moves used for all animation? One reason. Price. The cost of the
cylinder and its associated hardware is virtually identical for an analog or digital
movement. The analog function does need a bit more electronic control, but this no
longer represents a major cost. The servo valve does. The cost of a solenoid valve for a
digital function might be between $20 and $30. The cost for a servo valve to do the same
movement as an analog would be in the $500 to $1000 range. In addition there needs
to be some sort of ‘feedback’ on the cylinder to tell the EFB card where the movement is at

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There are variations in digital movements that use more than a single digital valve or cylinder. These
allow some variation in speed and/or stopping mid stroke. With open loop controls, the repeatability can
not be guaranteed as it can with an analog function. It is also possible to use a pair of four way valves or
a single five way valve in a closed loop servo system. This will give you positional repeatability, but not
the smoothness you get from a real ServoValve.

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GILDERFLUKE & CO. • 205 SOUTH FLOWER ST. • BURBANK, CALIF. 91502-2102 • 818/840-9484 • FAX[phone]

any given instant. When using a potentiometer, this can add from $25 (for a rotary pot) to
$100 or more (for a linear pot or LVDT).

Electronic FeedBack cards typically use what is called a ‘PID’ loop to control the
position of a movement. This type of loop is available on our new four channel PID-Quad
and BS-EFB Electronic FeedBack cards. The ‘P’, ‘I’ and ‘D’ stand for Proportional, Integral
and Derivative. Forget that. This is what they do:

The basic feedback loop is the Proportional (or ‘gain’). It is what is found on the simple
EFB cards like our EFB-Quad. A simple loop like this has been traditionally used for
controlling most analog functions in animated figures. This is because most figures’
positional requirements are not stringent enough to demand a higher performance
feedback loop.

The ‘P’ function compares the desired position with the actual position (as measured
by a potentiometer or other measuring device that is attached to the movement). The
difference is amplified and fed to a servo valve to open or close it as needed. If the ‘gain’
of the ‘P’ is turned up too high, then the movement will overshoot, and then try to get back,

and overshoot again, and again, and again..... This is what is known as oscillation, and it

is not a good thing. If the gain is tuned too low, then the movement will follow the
commands sluggishly.

The ‘I’ function is the one that is used to suck a movement in when it is too close to the
desired position for the ‘P’ function to open the valve enough to overcome the ‘stiction’ of
the cylinder. If the movement isn’t perfectly positioned, the ‘I’ function generates a slowly
rising voltage to the valve until it opens enough for the cylinder to move the last little bit to
the desired position. If the ‘I’ function is turned up too high, then the movement will
constantly seek the desired position, overshoot, and seek again. Unlike the oscillation that
occurs when the ‘P’ is set too high, the ‘I’ oscillation occurs at a low speed. Although
entertaining, it is rarely destructive. If the ‘I’ is adjusted too low, then the ‘dead band’
around the desired position will be wider.

The ‘D’ function is used so that you don’t have to turn the ‘P’ up too high to get the
movement to accurately follow fast changing commands. The ‘D’ gives an extra ‘kick’ to
the valve when a movement is commanded to start quickly. If it is set too high, then the
movement will start too quickly, overshoot the commanded position, and then slow down
as the ‘P’ error takes over.

Another adjustment that is available on our EFB-Quad or PID-Quad cards is a ‘Velocity
Limit’. This control allows you to set the maximum a valve can be opened by the
FeedBack card. On the EFB-Quad it allows you to set the gain a bit higher to control
oscillations by limiting the maximum opening of the valve. By raising the gain higher and
limiting the velocity, you can narrow the ‘dead band’ of the servo loop.

The PID-Quad also has adjustment to add a 60 Hz dither signal or offset (null) to the
output. The dither is used with some valves whose performance is increased remarkably
when such a signal is applied. The nulling allows you to center the spool of the valve
electronically if it wasn’t centered properly in the factory.

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The PID-Quad also features what are called ‘Compliance’ inputs. This adds a second
‘force’ feedback to an analog movement. This is usually a strain gauge or accelerometer
mounted on the cylinder in addition to the normal position sensor. This measures the force
being applied by the cylinder and feeds this to the FeedBack card. Sometimes an
accelerometer on the movement or differential pressure transducer on the valve are used
for a lower cost.

As a compliant movement is commanded to accelerate quickly, the inertia of the
mass of the movement applies a force to the strain gauge. This gets amplified and
added to the signal that the PID-Quad sends to the valve to open it further than just the
positional error would have made it open. Conversely, when the movement is
commanded to decelerate quickly, the strain gauge picks up the mass of the movement
in the opposite direction and the feedback card can open the valve in the reverse
direction to apply active braking to the movement as it approaches its target position.

The other thing that compliance does to a figure is to ‘soften’ it. If you press on a
compliant movement (one that uses a strain gauge), it will sense this external pressure
and the feedback card will actually open the valve to allow the movement to move out
of your way. In complex figures, as one movement applies forces to other movements,
they will respond to this force and all give a little. Of course, using pneumatics instead of
hydraulics gives this effect even without compliance feedback. With pneumatic figures,
the compliance feedback can be reversed to make the figure act a little stiffer, or a little
more like a hydraulic figure.

An EFB-Quad or PID-Quad controller is used to control up to four independent servo
loops. Each of these loops consists of a servo valve or motor controller, an actuator
(hydraulic or pneumatic cylinder or electric motor), and a transducer (typically a 10 Kohm
variable resistor) linked to the actuator.

In operation, a control voltage (nominally 0 to 10 VDC) is sent to the EFB-Quad or PID­Quad controller. The card’s circuitry compares this incoming voltage with the current
position of the actuator as sensed by the transducer.

The most common failure in animated figures which use EFB analog movements are
broken wires leading to the transducer. For that reason Gilderfluke's EFB-Quad and PID­Quad controller were designed so that they only needs two wires to each transducer
(three are usually required) and it constantly checks the status of these wires. If there is a
wire break, it will immediately switch off that axis. When a break is sensed, or when power is
first applied to the EFB-Quad or PID-Quad controller, it will stay in the error condition for
approximately 10 seconds. This will keep circuits with loose wire connections from jumping
in and out of error condition.

There is a 'broken wire' indicator LED for each of the four channels in the EFB-Quad or
PID-Quad controller. If any of the circuits is in an error condition, then the 'error' LED will light.
This error signal can be be sent to a remote indicator or alarm through the optically
isolated ‘Error’ output. A remotely mounted LED or small relay can be used to indicate a
problem with the figure on a central indicator panel.

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