Project 2 -- Hybrid Deliberative/Reactive Systems

NOTE: The hard copy of the write up for this assignment is due at the beginning of the class period. This means that if you are even a minute late, you lose 20%. If you are worried about potentially being late, turn in your write up ahead of time. Do this by submitting it to me during office hours or by sliding it under my office door. Do not leave it in my departmental mail box.

One problem with purely reactive systems is that they are limited to acting based on their current sensory information. This is a problem because that information may not be sufficient for the robot to efficiently accomplish the task given to it. For example, if you want a robot to get from point A to point B but the robot is unable to sense B from A, then there must be some other way for the robot to know which way to head next or the robot will be likely to take a very inefficient route, if it manages to find B at all. Because it is impractical to create a set of reactive behaviors that will overcome this problem in the general case, robotics researchers often add a deliberative component to the system. This deliberative component can plan an appropriate sequence of actions to carry out based on information not directly available to the robot through its sensors. Such information may be given to the robot from an outside source or recorded by the robot during its previous activities.

This project asks you to design, build, program, and demonstrate a robot that accomplishes a task very similar to the one from the previous project. To accomplish this task you will again need to have the robot autonomously carry out several different activities at appropriate times and in appropriate ways based on its sensing. However, in the present project, you will be graded in part on how efficiently your robot carries out the task. Use of a hybrid deliberative/reactive robotic paradigm is suggested, but not required, for this project.

Goals of this project:

• To give you experience engineering a robot that can makes use of information that is not directly sensed to improve the efficiency of its performance.
• To give you additional experience engineering a robot to carry out a task in an uncertain environment. The uncertainty in this environment will come from "noise" in both sensing and acting as well as the fact that you will not know the exact layout of the objects in the test environment before each test begins.
• To give you additional experience engineering a robot to carry out a task that is complex enough that it will need to engage in several different activities at appropriate and not necessarily sequential times.
• To improve and refine your team structure and method of operation.

You will design, build, program, and demonstrate an autonomous robotic system that carries out the following task: Efficiently finding a target object in the environment and returning it to the robot's base station. You will also turn in written material regarding team structure and organization, timelines and milestones, design and implementation of the robot and its software, and evaluations of team members. One or more team members will present information to the class about their robot.

Details of the task (most were described in class) follow:

• The target objects to be found will be the same as in the previous assignment.
• You will construct both a robot and a base station. These may be of any dimension if made exclusively from the kit materials provided. If you wish to use additional components, you must get prior approval for them and the robot and base station must each be limited to a one foot by one foot "footprint." Even with additional approved components, the primary components of the robot/base station system must be from the kits provided. The robot may be tethered to the base station for communication, power, movement, or other purposes but the tether will not be considered a part of the base station or the robot for purposes of determining the robot's proximity to the station (see below).
• The robot and base station will operate within an enclosure made from 2x4 lumber. The area enclosed is roughly 8 feet by 12 feet. The bottom of the enclosure will be the flooring of the lab. There will also be obstacles placed within the enclosure; these will be rocks of roughly fist size or smaller. Together, the enclosure, the floor, and the rocks will constitute the test environment.
• The robot must start within one inch of the base station (it may be touching). The robot must bring the target object within one inch of the base station (the target object may touch the base station). For purposes of determining proximity, only rigid components of the base station and the robot will be considered.
• The robot must stop after bringing the target object to the base station.
• The robotic system will be demonstrated in a series of tests. In each test, the team will place the robot and base station into the enclosure. After the robot and base station are placed in the enclosure, I will provide the team with a list of the coordinates of obstacles and a target object that will be placed into the enclosure (see below). Once the list has been given to the robot/base station system, I will place the obstacles and target object within the enclosure. At that time, the team will signal the robotic system that the test is to begin immediately.
• The format of the list of coordinates will be:

      x1,y1,x2,y2,...xn,yn
  

  where:
  • each xi,yi is one set of coordinates,
  • x1,y1 through xn-1,yn-1 are the coordinates of n-1 obstacles, and
  • xn,yn is the coordinate pair of a target object.

  The coordinates will be measured in feet with a resolution of one half foot. The x coordinate will measure distance from the north edge of the enclosure. The y coordinate will measure distance from the east end of the enclosure.

  As an example, one coordinate pair might be 3,6.5, indicating the object is 3 feet from the north edge and 6.5 feet from the east end of the enclosure. You would not get coordinates such as 7.3 or 2.25, which are not multiples of six inches.

  I would prefer to enter these coordinates directly into your laptop in this format. If you would like your system to receive the coordinates in some other way, you will need to have this approved in advance.

• Note that the list of coordinates given may be inaccurate in two ways.
  1. The coordinates given for the obstacles may be slightly off. For example, an obstacle said to be at 7.5,9 might really be closer to 7,9.5. Note, however, that the location given for the target object will be accurate to within the measurement system used (i.e., to within three inches in each dimension).
  2. The list may include a few spurious coordinates of obstacles or fail to include the coordinates of a few obstacles or target objects. For example, even though the list may list an obstacle at 1,1, there may not be any obstacle in the environment that corresponds with that coordinate pair. Similarly, there might be an obstacle at 7,11, even though there is no corresponding obstacle in the list. Note, however, that there will be a target object at the coordinates provided. Nonetheless, there may be additional target objects within the environment. If an additional target object is found, your robot may choose to retrieve it instead of the one given in the coordinate list. Remember, part of your grade is based on how efficiently your robot retrieves a target object. So, if it would be more efficient to get the discovered target object, rather than the one given in the coordinate list, you would get more points for retrieving the discovered one.
• Team members may not modify the environment prior to, during, or after each test of the robot on this task, except to clean up and restore the environment to its original state if it is modified by the robot.
• Team members may not modify the robot, the base station, or the code or communicate with the robot or the base station during each test of the robot on this task.
• Team members may modify the robot, the base station, and/or the code and may communicate with the robot and/or the base station between tests of the robot on this task. However, the time used by the team in these operations will be deducted from the half hour demonstration period.
• The robot and base station may make non-destructive, non-permanent changes to the environment during each test of the robot on this task. Team members must clean up and restore the environment to its original state if it is modified by the robot.
• The robot and base station should primarily use the sensors, actuators, electronics, and building materials provided in the kits, including the supplementary components provided since project 0 (the RCX system and sensors and the servo). You may also include a laptop computer as a component. The base station may be plugged into an electric outlet in the room. You may not connect either the robot or the base station to the Ethernet jacks or phone lines in the room, nor otherwise connect the robot and/or base station to other computers. The robot and base station together must form an autonomous system. You may augment these components slightly with such materials as tape, rubber bands, wires, batteries, light bulbs etc., but you will need prior approval for any such materials, including what they are and how they will be used. You may not damage or destroy any of the components from the kits.

Task allocation proposal.

You will turn in a proposal for what tasks need to be carried out and who will carry out each one. This should include reasons for carrying each task as well as for assigning them to particular people, with an eye towards balancing the amount of work each team member has to complete. After this there will be one more project: the final project.

This should be from 1.5 to 2 pages in length (roughly 80 characters per line, 50 lines per page). This should be turned in Monday, April 8.

Timeline with milestones.

You will turn in a list describing milestones to be accomplished and an associated timeline showing when each milestone is to be completed. You will also include a fallback plan describing what will be done in the event that a milestone is not reached on time.

This should be from 1.5 to 2 pages in length (roughly 80 characters per line, 50 lines per page). This should be turned in Monday, April 8.

Robot design

You will turn in a document describing the physical robot design, including its body, suspension, gearing, motors, sensors, and the layout of these components. This does not need to be detailed enough for an exact replica to be made (that is, you don't need to get to the level of the individual Lego pieces). Instead, it should give a high-level description of the parts used and how they are put together. This is the level of description I am looking for (taken with modifications from a description in my Ph.D. thesis of a real robot, constructed for a different task):

"This robot consists of two parts, a truck cab unit and a trailer unit. The cab is an Ackerman-steering 4-wheeled vehicle with rear-wheel differential drive. The front of the cab has a binary bumper switch that lets the robot know when it has contacted something from the front. The trailer is attached to the cab by a hitch constructed from a single-turn potentiometer. A servo with a set of photoresistors (CdS cells) is mounted on the back of the trailer so that the robot can keep track of the goal (a light bulb). The trailer also has a binary bumper switch on its rear to tell the robot when it is in contact with the goal.

"The potentiometer on the hitch measures the angle that the trailer makes with the cab. Valid angles that the trailer can make are within a 180 degree arc due to the physical constraints of the system. The light tracking servo on the trailer is also limited to a 180 degree arc."

This should be from 1.5 to 2 pages in length (roughly 80 characters per line, 50 lines per page). This will be turned in Wednesday April 17.

Robot (and base station) code

You will turn in the actual code you have written to control this robot. This will be written in Interactive C. If your base station is also programmed in any way, you will turn in all code that runs on your base station as well. You will turn in both a hard copy and an electronic copy of all code. Electronic copies should be mailed to hougen@ou.edu as mime enclosures.

Your source code should be well structured and well commented. It should conform to good coding standards (e.g., no memory leaks).

This will be turned in Wednesday April 17.

Robot code documentation

You will turn in a document explaining the data structures and algorithms used in your code.

This should be from 1.5 to 2 pages in length (roughly 80 characters per line, 50 lines per page). This will be turned in Wednesday April 17.

Notes on this assignment

You will demonstrate your robot during a half hour period between 9:00 am and 5:30 pm on Thursday, April 11 and/or Friday, April 12 (or on an earlier date, if you so choose). You may schedule up to two demonstration periods total on either the same or different days. The half hour will include set up and clean up times. You must be ready to demonstrate your robot when your scheduled time arrives.

Your demonstration will be video-taped for later use, including your use in your presentation (see below), if you so choose.

You will also have one or more group members present to the class the key features of your robot, including both its hardware and its software. This presentation will last 8 minutes and will be followed by a 1 minute question and answer period. Your group will be selected for presentation in a random order. You must be ready to present when your group number is called. If you will be using a laptop for your presentation, you should ensure that it works with the departmental projector before April 15.

You will be graded on the following issues:

• 5%: How you organize your team. (One grade for entire team.)
• 5%: How you divide up the tasks. (Either individual or team grades.)
• 5%: How you manage deadlines. (Both individual and team grades.)
• 50%: How you complete the tasks which you have agreed to complete. (Individual grades.)
• 30%: How well the robot accomplishes its task. (One grade for entire team.)
• 5%: How you evaluate the other members of your team. (Individual grades.)

How well the robot accomplishes its task will be scored in each test as follows:

• 5 Points: Robot is able to "find" target object. Up to 5 points will be awarded if the robot successfully distinguishes between the target object and other objects in the environment and demonstrates this in a way I can recognize (e.g., plays a particular tune, flashes lights in a pattern, or simply attempts to drive towards the object in preference to other directions).
• 15 Points: Robot is able to "reach" target object. Up to 15 points will be awarded if the robot successfully moves within one inch of the target object and demonstrates that it is aware of having done so in a way I can recognize.
• 15 Points: Robot is able to "pick up" target object. Up to 15 points will be awarded if the robot successfully picks up or otherwise latches onto the target object such that it can subsequently move the object without accidentally releasing or losing it. If the robot does accidentally release or lose the target object, you may still get most of these points if the robot recognizes this mistake and is able to pick up or otherwise latch onto the target object again, as necessary.
• 5 Points: Robot is able to "find" base. Up to 5 points will be awarded if the robot successfully distinguishes between the base and other objects in the environment and demonstrates this in a way I can recognize.
• 15 Points: Robot is able to return to base. Up to 15 points will be awarded if the robot successfully moves back to within one inch of the base station and demonstrates that it is aware of having done so in a way I can recognize.
• 5 Points: Robot is able to bring target object to base. Up to 5 points will be awarded if the robot successfully brings the target object to within one inch of the base station, stops, and demonstrates that it is aware of having done these things in a way I can recognize.
• 40 Points: Efficiency. Up to 40 points will be awarded based on the efficiency of the route your robot follows in completing the test. Up to 20 points will be awarded for the route taken from the base to the target object and up to 20 points will be awarded for the route taken from the point of target object retrieval to the base. I will primarily look at distance traveled to measure this. However, what we would really like to minimize in a lunar mission is energy used. Therefore, if your robot takes a direct route but engages in actions that would use lots of energy (such as moving obstacles or, to a lesser extent, driving over them), I will penalize your score accordingly.

The page limitations given above do not include figures, which are encouraged and may take up any amount of space.

Other

You may write your programs from scratch or may start from programs for which the source code is freely available (such as on the web or from friends or student organizations). If you do not start from scratch, you must give a complete and accurate accounting of where all of your code came from and indicate which parts are original or changed, and which you got from which other source. Failure to give credit where credit is due is academic fraud and will be dealt with accordingly.