Autonomous Agile Rovers (A2R)

The goal of this project is to develop concepts and methodologies, and carry experimentation for a low cost agile rover to traverse distances of up to 20 miles over rough terrain autonomously with minimal or no human intervention. There are many applications for such a rover, such as scientific investigations (e,g. observation and sample collection), planetary explorations, and information gathering in hostile environments. Because of the low cost, a number of such rovers can be deployed to explore the environment in a collaborative manner and the loss a rover due to malfunction or accident would not pose a major problem in term of cost or disruption of the mission.

Koli is the first generation in the series of A2Rs being developed at the Intelligent Machines and Systems Lab. It is a small size (approximately cm) rover designed for autonomous traversals of 5 -7 miles. Fig. 1 shows several phases of Koli’s construction. Currently, all mechanical design and assembly of electronic components have been completed. Despite its small size, the challenges we will need to overcome are similar to ones found in larger scale autonomous vehicles. Navigation will be achieved through a combination of several sensing technologies and intelligent control systems for robust path following and collision avoidance.

Figure 1 . Several phases of construction of Koli.

Fig. 2 shows an overview of the sensor architecture implemented in Koli. We believe that the most important sensor for a mobile platform is vision. We have two cameras for Koli, one CCD that is fixed pointing forward and another CMOS camera that is mounted on top of a pan and tilt actuator mechanism. The general idea is to implement a behavior similar to that of a human when driving a car. Position acquisition will be performed in two different ways. Absolute positioning will be obtained through two GPS chips. Since speed is a fundamental factor in Koli, one of the GPS chips gets 4 position fixes per second. The other GPS chip is calibrated for very weak signals, which makes it possible to operate it in environments that are challenging to traditional GPS units such as under heavy foliage, short tunnels and canyons. When absolute positioning is not available, we will use dead reckoning techniques to obtain relative positioning using a digital compass, wheel encoders and gyroscopes. The 3 gyroscopes will also serve for sensing pose and avoiding tipover.

Actuation is simplified since the platform is already remote controlled, all we need is to interface with regular servos and controllers to change direction and speed. Koli will also have an emergency mechanism that will allow taking control from the computer and giving it back to the remote control. We also plan to implement an actuation mechanism for restoring the rover after a tipover.

Figure 2.

Collision avoidance behavior will be based on vision and a set of sonar sensors, also mounted on the pan and tilt platform. Koli has special front and rear bumpers (see Fig. 1), designed to both reduce shock forces in case of inevitable impacts and collision detection through 6 switches installed within the bumpers.

The battery module and the engine module in Fig. 2 will be responsible for collecting internal information. The CPU may decide to slow down or even halt if internal parts reach dangerous temperature or voltage levels. The suspension module in Fig. 2 is formed by a set of activity sensors installed in each of the platform shock absorbers. These sensors give feedback on the type of terrain the rover is traveling. Over time using this feedback Koli will be able to learn that certain terrain textures correspond to adverse conditions (e.g. the terrain is too bumpy and therefore the speed must be reduced).

The greatest challenge will be implementing algorithms that will quickly make sense of all information being provided by sensors, and issuing actuation commands that will perform the desired navigation. Many challenging problems in such diverse areas as control, vision, pattern recognition and learning, are currently being resolved.

1 Koli in Persian means gypsy or nomad who travels in deserts and mountains in search of better pastures.