ABSTRACT:
We present a multi-vehicles system capable to climb a scalar field. The vehicle are capable to move in formation, climbing the intensity of a random positioned light source, and either detect multiple light sources, breaking formation in order to direct singularly along a preferred direction, according to the field measure that each of them detect.
We use simple and reliable test-bed platforms, communicating through an RF-transceiver, and directed from Basic Stamp 2 from Parallax.
MISSION OVERVIEW
We present a moving sensor platform composed of three robots. They are planned to move in a co operative way detecting one or more random positioned random light source. Each platform is equipped of a light detector sensor, a photodiode. The sensing beam of the photodiode has been blinded to reduce the noise coming from external disturbances.
The trajectory of the three vehicles is directed by one of the three agent that acts as a master. The master vehicle, depending on the actual value of measurements that it takes, implements a decision algorithm in order to decide the trajectory and drives the two slave vehicles.
Vehicle in the Neighborhood of a Light Source.
MATHEMATICAL MODELING AND GOVERNING EQUATIONS
This section briefly explain the mathematical model adopted to derive the motion of the three robots.
We adopted some of the tools from classical control theory. As a first hypothesis we reasonably consider
the motion of the vehicles plain. According to this, the state vector of each vehicle x(t) :R+→R4 will be composed of four elements, two describing the position vector p(t) :R+→R2 and two describing the velocity v(t) :R+→R2.
HARDWARE ENVIRONMENT
The hardware implementation we adopted for the moving sensing platform comprises the following components for each vehicle:
- 1 BS2
- One RF-transceiver (912MHz)
- Two servomotors
- 1 photodiode
BS2 Parallax.
BILL OF THE MATERIAL AND PROTOTYPE COST
Mass production cost analysis:
The prototyped system is a proof of concept and such will not be the final end product that will be mass produced. The end product is determined by the specific use of the system, which is formation control. If the application were to be underwater, additional costs of water proofing and propulsion needs to be considered, as well as a means to communicate with the surface operator.
CONCLUSIONS AND FUTURE WORKS
The multi-vehicles sensing platform demonstrate some advantage as easy hardware and software implementation, good reliability working in emergency mode. The system shown good performances also 9 with open loop control design. Anyway it is reasonable to think to improve the design through a closed loop control.
To realize a closed loop controller, for example a proportional controller, we need a inertial platform in order to evaluate the actual state of the vehicle. Otherwise should be sufficient an ultrasonic sensor that is capable to evaluate relative distance between two vehicles, and correct the angular velocity of the servomotors trying to maintain the correct relative position.
Source: NYU
Authors: Francesca Fiorilli | Saran Kakarlapudi | Danny Tan