Conditional RtActivities

RtActivities that start one of two options depending on a sensor measurement.

A ConditionalRtActivity


  // Example Code 
  // retrieve DeviceInterface 
PtpInterface ptpInterface = lwrLeft.use(PtpInterface.class); 
// drive somehow 
ptpInterface.ptp(new double[] { 1, 1, 1, 1, 1, 1, 1 }).beginExecute(); 
// next move to execute... 
PlannedRtActivity ptp2 = ptpInterface.ptp(new double[] { 2, 1, 1, 
    1.5, 1, 1, 1 }); 
// ...if no force is measured 
BooleanSensor torqueSensor = lwrLeft.getJoint(1).getTorqueSensor() 
// linking force condition to move Activity 
ConditionalRtActivity nextMove = new ConditionalRtActivity (torqueSensor, ptp2); 

With the class ConditionalRtActivites, the Robotics API provides the possibility to differentiate between two pre-planned Activites and, depending on the result, chooses one of them to execute.

In order to use the class in an application, it must be fully parameterized upon construction.
The constructor itself needs two separate Activities (which can be ConditionalRtActivites themselfes for further branching) and a special type of Sensor called BooleanSensor. Sensors will be further explained in the next chapter.

A BooleanSensor can only return two values: True and False.
When the ConditionalActivity is executed by the RCC, the current value of the Sensor is checked and based on the result, the first (BooleanSensor returns True) or the second (False) Activity will be executed.

It is also possible to commit just one Activity and a BooleanSensor to a ConditionalRtActivity. Then, the committed Activity will only be executed if the Sensor is True.

The full constructors for both approaches are shown below:

How to create Summary

(BooleanSensor condition, RtActivity ifActivity)
Returns a ConditionalRtActivity
which only executes if the Sensor is ”‘True”’

(BooleanSensor condition, RtActivity ifActivity, RtActivity elseActivity)
Instantiates a new ConditionalRtActivity
which executes the ”‘ifActivity”’
if the Sensor is ”‘True”’,
and the elseActivity if the Sensor is ”‘False”’

Alternative: Invoke RtActivities.ifElse
(condition, ifActivity, elseActivity)
Returns an instantly created and anonymous

Like every Activity, a ConditionalActivity can be given a name too, but the constructors still stay the same:

As stated above in the video, the following Example instructs a lightweight Robot to drive its left arm with two different Activities: The first one will be executed no matter what, while the second one will start only if there was no obstacle in the way of the first movement. Please note that this is just a quick illustration and that the collision-handling, which is vital in a real environment context, is nowhere implemented. It is therefore strongly advised to not use this code with a real robot.

Please Note:

If the application is tested as a simulation, it is recommended to use the class BooleanFromJavaSensor, instead of a BooleanSensor, since the BooleanFromJavaSensor can be parameterized by hand and thus, every possible outcome can be calculated.