Actions_quiz cannot be evaluated by the system


I have completed actions_quiz and wanted to submit it for evaluation. The system gave error as in the image below.

Screenshot from 2020-05-25 17-33-40

Hi @enderayhan,

May I ask that you try again, please? I was able to run the evaluation successfully just now.

Before that, please run your package and ensure it’s not generating any errors. It could be that the package contains some code that crashes the grader.

Hi @bayodesegun,

I resubmitted. It works. Thanks.

As for quiz result, I got 7.5 mark. Evaluation screen showed that drone is taking off. However, it did not correct that drone is also landing. In deed, my code is working like a charm, without any problem. Why would that happen?

To be sure, After I send TAKEOFF command through /drone_action_server/goal topic via rostopic pub, should it be terminated automatically after taking off? Because I manually terminate rostopic pub … on terminal. Afterwards, I send LAND command through the same topic. They are all working. Can you please clarify this problem?

Hi @enderayhan,

What reason did the grader give for reducing your score to 7.5?

Here are some hints:

  • Check that your action does not publish more than once. It should just publish the message once and exit.
  • Ensure that publishing works the first time, every time:

Please let us know.

Hi @bayodesegun,

I have checked what you said and tried many things. My drone still obeys the commands. It takes off and lands when the command is sent. Also, grader did not give any reason for 7.5. It just showed lastly that drone takes off (mark: 7.5). Afterwards, grading was completed without providing any negative reason.

I am publishing land or takeoff command in a while loop for 3 seconds by using time.sleep. I m using two terminals which one is for roslaunch, and the other one is for publishing the message. After I send the goal message through the topic via rostopic pub command, should it exit? For example, after I send takeoff command, the drone takes off. And then, I apply ctrl+c to kill the process on terminal and send the land command via rostopic pub command. Is that wrong? If so, I could not figure out how to do? Can I share my code here, at least a snippet of code?


This might work, but I’d recommend you use the logic for publishing only once as this guarantees that it will work and wastes no time putting the node to unnecessary sleep :slight_smile:.

Regarding the Quiz grader not giving reasons for marking you down, please let’s look into that and get back to you.

No, please don’t share it. Let’s check what’s going on.

Dear @bayodesegun,

This might work, but I’d recommend you use the logic for publishing only once as this guarantees that it will work and wastes no time putting the node to unnecessary sleep :slight_smile:.

But, sending takeoff or land command once will not work. Also, in drone exercise that you taught us, you are also sending landing and taking off command in a loop.

By the way, I have submitted my quiz 3rd time just for validating whether grader provides reason or not. It again did not give any output. Please see the screen shot below.
grader grader2

It will work if you use the logic explained in this post: How to publish once (only one message) into a topic and get it to work

Sending the command in a loop is a rough hack to fix the problem described in that post, but it’s not the best solution imho. We should probably update the notes.

We’ll look into it, but what seems to be happening here is that the drone is not landing after taking off. Did you see the drone land while the grader ran?

No, in deed, I did not see the drone neither took off or landed during grading. I particularly paid attention on that.

Then I suggest you review your Quiz vs the expectation given, carefully. The grader could obviously not takeoff and land your drone properly, so there’s one or more sneaky bugs somewhere… :bug:

Please check the names you have used carefully, comparing with the names specified in the Quiz instructions. I’ve been informed that you did not use the specified name for your Action…

My bad and it is big time! Yes, my action server name was wrong.

However, I still need an answer for the question that I asked earlier which is:

Thanks a lot.

No problem, it happens. just be careful next time.

No, it’s perfectly right.

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