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About IDMARS
When there are situations which are dangerous for humans, or when humans are not capable of performing certain tasks, there is a necessity for the use of robots. Such situations include clean up of radiation sites, deep-sea research, and the exploration of space. The UNM NASA ACE and NASA PURSUE programs have recognized the need for robots and have undertaken a project to develop autonomous mobile robots. Mobile robots, as is implied by their name, are robots that can move from one location to another. This means that without having to be transported, they can move around freely within their environment. Non-mobile robots include servo arms and manufacturing equipment. While these robots do have moving parts, the robot overall does not change positions. Examples of mobile robots include: land based tracked or wheeled robots, hover craft and flying robots, boat or submarine robots, and deep space probes. Currently, the robots being developed at UNM are land based tracked robots. This means they move around on the ground in a manner similar to tanks. In order to achieve autonomy these robots are equipped with a variety of technology. This technology includes: mechanical hardware, electronics and software, sensors, and communication equipment.
Autonomous Robots
The UNM NASA programs intend to design robots that are capable of being fully autonomous. The move towards robotic autonomy is still in its infancy. Traditionally robots have been used with very little self-autonomy. This means that they are controlled directly by humans, either through a cable or with wireless communication. However, sometimes human control may not be possible. It is a possibility that the robot may exit communication range or communications may be too slow for instantaneous control. Such is the case with robots used for space exploration. Communication with robots in deep space is plagued by lengthy time delays since the communication signal travels considerable distances. In addition, while exploring a planet such as Mars, a robot may find itself in a situation in which there is a communication blind spot due to a cave or a canyon. This results in the need for robots capable of autonomous behavior. This means that when human control is not possible the robots should control themselves in order to fulfill their mission objectives. This is by no means an easy task to accomplish. In order to achieve many meaningful goals a single robot will probably not be sufficient. Therefore, multiple robots must be employed in order to carry out a mission objective. These robots must be able to cooperate with each other in order to work together effectively. This implies that the robots must be able to communicate with each other. Therefore, the robots have to be equipped with wireless communication.
To meet these goals NASA PURSUE and NASA ACE have constructed two mobile robots. These robots are designed to be fully autonomous. As such, they are capable of exploring an unknown environment while avoiding potentially dangerous obstacles. In addition, they have full wireless capabilities. They can communicate both with each other and with a base station. In the event the base station is not able to communicate with them, they are still fully capable of exploring the environment.
Robot Communications
The robots are designed to cooperate with each other. In order for cooperation they must be able to talk with each other. This leads to the need for wireless communication equipment. This equipment, located on the smaller platform, is centered on the Stamp micro controller. The Stamp is connected to a transceiver made by Parallax Inc., shown in Figure 1. A transceiver is a device that transmits and receives radio signals.
Figure 1
The Stamp runs a program that constantly checks for an incoming message. If a message is received the program checks to see if the message is intended for that particular robot. This is done with a robot ID number. Each robot has a unique ID. Thus, all other robots ignore a message that is intended for another robot. This communication scheme allows many individual robots to communicate with each other without confusion. A unique feature of this communication scheme is that it does not rely on a central base station. A base station is not a robot but instead is a stationary computer. Many communication schemes require that all messages first be sent to the base station. The base station then relays the message to the appropriate robot. While this scheme does work, it has some serious limitations. Therefore, the robots being developed at UNM can communicate directly to each other without using a base station. This makes the communication scheme much more flexible and less prone to failure. Since communications are not all sent to a single point, they are not vulnerable to a single failure. Even if one of the robots has a malfunction, the other robots will still be able to communicate. This is not the case in a centralized base station scheme, where if the base station malfunctions all communications are lost. In addition, the robots can explore a larger area since they do not have to remain in the range of a non-mobile base station. Currently, the non-centralized communication scheme being used by the robots has been implemented with great success.
Mechanical Parts
The mechanical hardware is the body of the robot. It consists of the robot’s tracks, motors, and platforms. Each robot has two tracks, a design similar to that of a tank. The tracks and bottom base of the robot come from a remote control vehicle found at Radio Shack. This vehicle has been stripped down leaving only the tracks and the bottom base. The bottom base can be seen on the next page in Figure 2.
Figure 2
A single Futaba motor, shown in Figure 3, moves each track. The Futaba motors have been converted into standard DC motors. This means that the gear attached to the motor is continuously spun in a complete 360-degree circle.
Figure 3
The Futaba motors are held into place by posts made from Legos. The plastic posts are secured to the base with screws.
Above the motors lies a platform. The platform is connected to the bottom base of the Bedlam by four posts, one on each corner. The platform and posts are secured by screws. The platform serves as a work area. The robot’s electronics and sensors lie on top of the platform. A second smaller platform has also been mounted on top of the larger platform at the rear of the robot. Beneath this platform lies the battery which powers the robot. On top of the platform is the communication equipment. Both the top and bottom platforms are shown in Figure 4.
Figure 4
Robot Electronics
The electronic components of the robots center on two micro controllers. A micro controller is in essence a small computer. The first micro controller is the Handy Board shown in Figure 5.
Figure 5
The Handy Board is built around the Motorola 68HC11 microprocessor. The 68HC11 is the brain of the Handy Board, similar to the way a Pentium processor is the brain of a computer. The Handy Board controls the robot navigation. This is done by loading three computer programs into the Handy Board. These programs have been developed at UNM. The first program is the core program. This program is the main coordinator. It tells the other programs what to do and when to do it. The second program controls the robot’s movements. It uses the sensors to look for objects near the robot. It then controls the motors so that the robot moves around without colliding with any objects. This is an important part of autonomous behavior since it allows the robot to move without human intervention. The third program allows the Handy Board to talk with the other micro controller, the BASIC Stamp 2sx shown in Figure 6.
Figure 6
The Stamp is located on the smaller platform. The Stamp is the computer that handles the robot’s communications. It is through the Stamp that the robot can talk wirelessly with other robots and with a base station.
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