Auto-Manual Button
- Gary Cane
Operator Menu Location: Generic Hardware Operators 
Auto/Manual
Operator Bitmap:
Functional Description:
The Auto/Manual Button operator provides a smooth transition between automatic and manual modes of operation. When in automatic mode, the operator output is equal to its primary input, i.e., y=x. When in manual mode, the operator output value is manually adjusted using with front-panel controls (e.g., keypad buttons).
The operator's boolean output b indicates the mode: it is HIGH when the operator is in manual mode; it is LOW when the operator is in automatic mode.
When the operator transitions from automatic mode to manual mode, its output y remains at the transition value until manually modified (e.g., from front panel buttons).
When the operator switches from manual mode to automatic mode, the transition may be abrupt or smooth (bumpless). If the bumpless transfer property is not selected, the output will switch instantly from the manual output to the automatic output. When the bumpless transfer property is checked, the transition from manual to automatic is guaranteed to be smooth. The nature of the transition (i.e., the transfer profile) can be either exponential or linear.
Let 
be the difference between the manual output and the automatic output at the instant the operator switches from manual to automatic, 
. Under an exponential transfer profile, the operator output will be (approximately)
where r is a time constant expressed in minutes. Under a linear transfer profile, the operator output will be (approximately)
where r is a linear decay rate expressed in (input) units/minute.
Generally, a person will use a keypad button to switch a control station from operating in automatic mode to operating in manual mode (and vice versa). You would also typically rely on a person to make manual output adjustments. However, under certain conditions you may wish to automatically switch the A/M operator from one mode to another-and automatically adjust the "manual" output-without user involvement. The A/M Button operator has two secondary inputs that allow you to do just that. You can use digital input 
to automatically set the auto/manual operating mode. And you can use analog input 
to automatically set the "manual" output. These two inputs are edge-triggered, meaning that they override the keypad buttons and affect the operator output only when their value changes. While these inputs remain fixed, they do not affect the outputs.
When the operator is in manual mode and input 
switches from HIGH (manual) to LOW (auto), the operator will switch into automatic mode and its output y(t) will (over time) match its input x(t). (If the bumpless transfer feature is enabled, the output will vary according to the equations above.) If the operator is in automatic mode and input 
switches from HIGH (manual) to LOW (auto), then it will remain in automatic mode.
When the operator is in automatic mode and input switches from LOW (auto) to HIGH (manual) at time 
, the operator will switch into manual mode and its output y(t) will move toward the value of input 
at the time of the switch. The transfer of the output-from 
to 
--occurs in increments and is rate-limited by a Key Repeat Time property, 
. The output will vary as if a user pressed a A/M keypad button to switch to manual and then pressedand held down-an arrow keypad button until the output reached a desired value, 
. Mathematically, we can express this as:
Whenever the manual-override input changes value, the output will move toward that value according to the equation above. (Of course, this occurs only while the operator is in manual mode; otherwise, the 
input is ignored). In order for the manual input to affect the output, its value must change. Moreover, the magnitude of the change must exceed the Manual Input Activation Threshold 
over a period of time called the Manual Input Activation Time T. In other words,
must be satisfied in for the manual output to begin moving toward 
.
Do keypad buttons on the hardware faceplate have precedence over the inputs 
and ? The answer is that the operator will follow its most recent command. If it is commanded by its inputs to automatically adjust its manual output value, it will do so. If in the process of automatically adjusting the manual output value a person presses one of the arrow keys, the A/M Button operator will follow the key commands. It will not resume its automatic adjustments unless input changes value---remember that this input is edge-triggered!
In Design Pad the A/M Button operator doubles as a special networking operator designed to synchronize the operation of multiple A/M stations. You link the A/M Button operator to a communications channel to broadcast its outputs over a controller network and to receive information from one or more Remote A/M operators from other stations on the network. Together, the network-enabled A/M Button operator and Remote A/M operators offer synchronized auto/manual functionality between multiple stations. For example, consider the case where one station contains a network-enabled A/M Button operator and two other stations on the same controller network each contain a corresponding Remote A/M operator. If you switch any one of the three stations from automatic mode to manual mode, the other two stations will also switch to manual operation. If you then adjust the manual output from any one of the three stations, the other two will match that manual output. If you switch any one of the stations back into automatic mode, the other two stations will also switch into automatic mode. When the stations operate in automatic mode, the output signal of the remote A/M operators will follow the output of the A/M operator.
In order to associate an A/M Button operator in one schema to a Remote A/M operator in another, you must match their signal name property. If you want to associate multiple remote A/M operators with an A/M operator, then you set the signal name property of all operators to the same case-sensitive character string.
User-Defined Properties:
Signal Name. A string label that identifies the operator. When networking is enabled, this character string is used to associate (synchronize) an A/M operator in one schema with remote A/M operator in other schemas.
Initial State. The operator mode (auto or manual) on startup (at time t=0).
Initial Value. The analog output value on startup (at time t=0). Applicable only if the initial state is set to manual.
Minimum. The minimum analog output value. Applies to both auto and manual modes.
Maximum. The maximum analog output value. Applies to both auto and manual modes.
Increment Magnitude. The magnitude of manual output increments when in manual mode. The manual output will be incremented or decremented by this parameter when 
a person presses an increment/decrement keypad button on the hardware front panel (ii) input changes value (see Manual Input Activation Threshold property and Manual Input Activation Hysteresis property).
Bumpless Transfer. When the operator switches from manual mode to automatic mode, the output signal may differ from input x. If this property is not checked, there may be a discontinuity in the output. When bumpless transfer is checked, the transition from manual to automatic is guaranteed to be smooth.
 Transfer Profile. When the bumpless transfer property is set, the output will transition smoothly from manual mode to automatic mode. This property characterizes the nature of the transition: exponential or linear. When the exponential profile is selected, the difference between the manual output and automatic output will decay exponentially. When the linear profile is selected, the difference will decay linearly.
Transfer Rate. The rate at which the difference between manual output and automatic output will decay when the bumpless transfer property is set. When the exponential profile is selected, this parameter defines the exponential decay rate expressed in minutes. When the linear profile is selected, this parameter defines the linear decay rate in input units/minute.
Number of Significant Digits to Display. The number of significant digits to use when displaying the manual output on the alphanumeric displays.
Lock in Manual State. When this property is selected, the operator will only function in manual mode. A person will not be able to switch it into automatic operation.
Broadcast Priority. How critical is the signal the button was pushed.
Display Auto/Manual State Input.
Display Manual Input. This property determines if input pin 
is visible in the schema diagram. Design Pad issues a warning upon processing the schema when the pin is visible but not connected. The warning message is not issued when the pin is not visible (when this property is not checked).
Manual Input Activation Threshold. When the A/M operator is in manual mode, the output can be adjusted automatically using input . In order for automatic adjustments to begin, the manual input must change value. The magnitude of the change must exceed this parameter. (And it must exceed this value for a period of time defined by the Manual Input Activation Time property below.)
Manual Input Activation Time. When the A/M operator is in manual mode, the output can be
adjusted automatically using input . In order for automatic adjustments to begin, the manual input must change value. The magnitude of the change must exceed a threshold value over a period of time (in milliseconds) defined by this parameter.
Key Repeat Time. Controls how long the button must be held down to interpret that as a repeat.
Comments: None.
See Also: Remote A/M Button