Multi bot nxt programmers
While simple programming for an NXT invention can be done using the control pad on the Intelligent Brick, for more complex programs, users need to use either the NXT-G programming environment that comes bundled with the kit, or purchase a third-party programming environment that interacts with the Brick, of which there are many, including LabVIEW.
The software provided with this set is an evolution on the previous NXT-G programming language. As such, it keeps much of the same functionality, but also adds several new features. Most notably, since the EV3 platform runs Linux, it has access to several new types of ports, including a USB connector and Micro SD slot — which can be used to load alternative operating systems. While the new blocks are mostly backward compatible, plugins are required to use them with the older NXT software, and some features will be unavailable.
NXT blocks can be used with EV3 software, but they will not be able to take full advantage of the newer software features. Whether you're looking for some pre-tested lesson plans or easy-to-follow guides to help teach your kids about programming, these sites should be very useful:.
There are several book available on programming with NXT-G, though most of them cover the same material, because the majority of NXT-G books are designed for young, beginning programmers. The concepts children develop through programming with NXT-G will apply to any language they pick up in the future, whether they stick with another graphical language such as LabVIEW or Pure Data , or transition to a more traditional text-based language.
Designing with NXT-G also allows kids to explore the many applications of programming, beyond simply manipulating images on a computer screen. Through the creation of several types of robots, they will develop real-world, physical devices, while deepening their understanding of programming, robotics, and engineering. Want to know how you can help support our work? We earn a referral fee when you buy services from many of the hosts on our site. Home Resources Nxt G.
This behavior remains active as long as the motors are turning. The method code is:. That was easy enough! Now the standard suppress method will stop this action when it is called:.
So far, so good. Now we need to implement a method to tell Arbitrator when this behavior should become active. As we outlined earlier, this robot will drive forward always, unless something else suppresses it, so this behavior should always want to take control it's a bit of a control freak. The takeControl method should return true, no matter what is happening. This may seem counter-intuitive, but rest assured that higher level behaviors will be able to cut in on this behavior when the need arises.
The method appears as follows:. That's all it takes to define our first behavior to drive the robot forward. The complete code listing for this class is as follows:. The second behavior is a little more complicated than the first, but still very similar. The main action of this behavior is to reverse and turn when the robot strikes an object or detects one close by.
In this example, we would like the behavior to take control only when the touch sensor strikes an object, or the ultrasonic sensor gets an echo from a close object. Here is the takeControl method that does it:. This assumes that a TouchSensor object has been created in an instance variable called touch and a new UltraSonicSensor object has been assigned to the variable sonar.
For the action, we want the robot to back up and rotate when it detects an object, so we will define the action method as follows:. We now have our two behaviors defined, and it's a simple matter to make a class with a main method to get things started.
All we need to do is create an array of our behavior objects, and instantiate and start the Arbitrator as shown in the following code listing:. The above code is fairly easy to understand. The first two lines in the main method create instances of our behaviors. The third line places them into an array, with the lowest priority behavior taking the lowest array index. The fourth line creates the Arbitrator, and the fifth line starts the Arbitration process.
When this program is started the robot will scurry forwards until it bangs into an object, then it will retreat, rotate, and continue with its forward movement until the power is shut off. This seems like a lot of extra work for two simple behaviors, but now let's see how easy it is to insert a third behavior without altering any code in the other classes.
This is the part that makes behavior control systems very appealing for robotics programming. Our third behavior could be just about anything. We'll have this new behavior monitor the battery level and play a tune when it dips below a certain level. Examine the completed Behavior:. The complete tune is stored in the note array at line 6 and the method to play the notes is at line This behavior will take control only if the current battery level is less the voltage specified in the constructor.
The takeControl method looks a little inflated, and that's because it also displays the battery charge to the LCD display. The action method is comparatively easy. Action makes a bunch of noise, then exits the program. Since this behavior stops the program, we might get away without a a suppress method. But just in case we detect a wall, while playing the tune, we use one.
To insert this behavior into our scheme is a trivial task. We simply alter the code of our main class as follows:. The voltage level of the NXT at rest is different from the voltage when in action.
The voltage level at rest might be 7. Make sure the voltage threshold used in the BatteryLow constructor is low enough. This example beautifully demonstrates the real benefit of behavior control coding.
Inserting a new behavior, no matter what the rest of the code looks like, is simple. The reason for this is grounded in object oriented design; each behavior is a self contained, independent object.
When creating a behavior control system, it is best to program each behavior one at a time and test them individually. If you code all the behaviors and then upload them all at once to the NXT brick, there is a good chance a bug will exist somewhere in the behaviors, making it difficult to locate. By programming and testing them one at a time it makes it easier to identify where the problem was introduced.
In order to understand why we recommend this design pattern, it is useful to dig a little deeper into the inner workings of the arbitrator. The Arbitrator contains a monitor thread that cycles through each of the behaviors, checking the takeControl method to see if the behavior should become active. It starts with behavior of largest index because they are are stored in increasing priority order and works down the array. As soon as it comes across a behavior that should take control, this is the highest priority behavior that wants control at the moment.
If this behavior has higher priority than the active behavior, the monitor thread executes suppress on the active behavior, and then starts checking each behavior from the top again. The main thread of the Arbitrator is very simple. It just calls the action method on the highest priority behavior, as determined by the Monitor thread and that behavior becomes the active.
When action exits, either because its task is complete or because the Monitor thread has called suppress in it, that behavior is no longer active, and the loop continues, calling action on the behavior that is now has the highest priority as determined by the Monitor thread. It is possible that the same behavior repeatedly becomes active. It would be nice if all behaviors were as simple as the examples given above, but in more complex coding there are some unexpected results that can sometimes be introduced.
If it is necessary to have a behavior that uses its own Thread, for example, can sometimes be difficult to halt it from the suppress method, which can lead to two different threads fighting over the same resources - often the same motor!
But in this pattern, the suppress method does not try to halt anything. It is the responsibility of the action method to keep testing the suppressed variable, exit as soon as it become true, and leave the robot is a safe state for the next behavior.
Another advantage of this design pattern is that each behavior is coded in the same way without making any assumptions about its priority. You can then change the priority order of your behaviors or reuse them in other applications without reprogramming any of them. Behavior coding is predominantly used for autonomous robots - robots that work independently, on their own free will. A robot arm controlled by a human would likely not use behavior programming, although it would be possible.
For example, a robot arm with four joystick movements could have a behavior for each direction of movement. But as you may recall, behaviors are ordered with the highest order taking precedence over lower order behaviors. Who is to say that pushing left on the joystick would take precedence over pushing up?
In other words, behavior control in anything other than autonomous robots is largely overkill. So why use the Behavior API? The best reason is because in programming we strive to create the simplest, most powerful solution possible, even if it takes slightly more time. The importance of reusable, maintainable code has been demonstrated repeatedly in the workplace, especially on projects involving more than one person.
If you leave your code and come back to it several months later, the things that looked so obvious suddenly don't anymore. With behavior control, you can add and remove behaviors without even looking at the rest of the code, even if there are 10 or more behaviors in the program.