16-782: Planning and Decision-Making in Robotics Homework 3: Symbolic Planning
16-782: Planning and Decision-Making in Robotics
Homework 3: Symbolic Planning
Due: Friday November 17, 11:59pm
Professor: Maxim Likhachev Fall 2023 TAs: Abigail Breitfeld, Tejus Gupta
Description
In this homework, you will implement a generic symbolic planner. We have provided the code for reading an environment description from a file by using regular expressions and generating the cor- responding environment object. Your job is to write a planner that gets an environment object as an input and outputs a sequence of actions to go from the start to the goal. An example of the environment description for the Blocks world that was taught in the class is below:
A
B
C
B
C
A
Symbols: A, B, C, Table
Initial Conditions: On(A,B), On(B,Table), On(C,Table), Block(A), Block(B), Block(C), Clear(A),
Clear(C)
Goal Conditions: On(B,C), On(C,A), On(A,Table)
Actions:
MoveToTable(b,x)
Preconditions: On(b,x), Clear(b), Block(b), Block(x)
Effects: On(b,Table), Clear(x), !On(b,x) Move(b,x,y)
Preconditions: On(b,x), Clear(b), Clear(y), Block(b), Block(y)
Effects: On(b,y), Clear(x), !On(b,x), !Clear(y)
In the provided code, we parse the description files for you and provide you with the environment object (Env class) which includes the 1) initial conditions, 2) goal conditions, 3) actions, and 4) symbols. An object of the Env class is passed to your planner.
The Env class uses the data structures below. Feel free to add more functions to them as needed. However, DO NOT change the main function.
• Condition: this class includes 3 member variables: 1) name of the condition, 2) the arguments, and 3) if the condition is negated or not.
1
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GroundedCondition: this class includes 3 member variables: 1) name of the condition, 2) the values for the arguments, and 3) if the condition is negated or not.
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Action: this class includes member 4 variables: 1) name of the action, 2) action arguments, 3) preconditions, and 4) effects.
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GroundedAction: this class includes 2 member variables: 1) name of the action and 2) values for the arguments.
In this homework, we provide the environment description files for three environments: 1) Blocks World, 2) Blocks and Triangles, and 3) Fire Extinguisher.
We will explain these environments later on. These environment description files are parsed and an environment object (Env) is passed to your planner. Your job is to write a general planner that outputs a sequence of steps to get from the initial condition to the goal condition. The output of your planner is a list of GroundedActions (std::list<GroundedAction>).
Environments
Blocks and Triangles EnvironmentThis environment is similar to the Blocks World problem explained in the class. In addition to the blocks, this environment has triangles that can be moved in the exact same way as blocks with the exception that nothing can be put on top of them. A simple example of this environment with only three objects is shown below.
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C |
A |
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B |
||
We provide a description file for an environment with 5 blocks (B0, B1, B2, B3, B4), 2 triangles (T0, T1) and a Table. The start and goal conditions are below:
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Startconditions: B0isonB1,B1isonB4,B2isonTable,B3isonB2,B4isonTable,T0is on B0, and T1 is on B3.
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Goal conditions: B0 is on B1, B1 is on B3, and T1 is on B0.
For easier debugging, we provide a trivial environment (BlocksEasy.txt) with 3 blocks (A,B,C).• Start conditions: A is on B, B is on Table, C is on Table. • Goal conditions: A is on Table.
Fire Extinguisher Environment1
The goal of this problem is to have a pair of robots put out a fire. This domain has two robots 1) aquadcopter and 2) a mobile robot.
The mobile robot can travel between locations. The quadcopter only moves between locations by landing on the mobile robot and having the mobile robot travel to the other location. The quadcopter can fly around a single location (cannot navigate between locations) if its battery level is High, but it won’t be able to take off if its battery level is Low.
1Inspired by the final challenge at 1st Summer School on Cognitive Robotics at MIT
Whenever the quadcopter is on the mobile robot, it can charge its battery by calling the charge action. The quadcopter has a tank that can be filled with water when the quadcopter is on the mobile robot at location W (where there is water).Every time the quadcopter pours water on the fire, its battery level becomes low and its water tank becomes empty (it should go back to W to fill its tank). The robots will each start at one of five different locations (A, B, C, D, E), which are far from W and F. The quadcopter cannot land on the ground.
• Start conditions: the quadcopter is flying and at location B. The mobile robot is at location A. The quadcopter’s water tank is empty.
• Goal: The fire is extinguished.
Compiling and Executing the Code
To compile the code:
>> g++ planner.cpp -o planner.out (optional but may be necessary: -std=c++11)
To run the code add the name of the input file to your command:
>> ./planner.out <path to environment description file>
Once your planner returns the plan, it will be printed out. It is your responsibility to check whether the plan is valid with respect to the start conditions, actions, and goal conditions.
