Autonomous Robotic System for the Monitoring and Inspection of Unstructured Environments (Archaeological, construction, disaster sites)

Autonomous robotic systems are increasingly deployed to perform monitoring and inspection operations in unstructured environments such as archeological, construction, amd disaster sites. However, the unmanned ground vehicles used in these fields face uneven terrain and large obstacles which cause severe vibrations of the vehicle. These vibration leads to a reduced accuracy and reliability of the sensors which are used both for navigation and environment inspection. Therefore, vibration reduction is a critical aspect. However, vibrations can also be exploited to extend the range and the survivability of the autonomous system by means of pieozelectric energy harvesting devices. In this dissertation the dynamics of small autonomous vehicles is studied with the aim with the aim of characterizing vehicles vibrations induced by terrain unevennes. Indeed, these vehicles have particular characteristics compared to standard road vehicles such as soft non-pneumatic tires. Experimental tests including measurements of inertial and stiffness properties and modal analysis are presented. Mathematical models are developed using experimental data and used to investigate the vibrational behaviour of the vehicle and the effect of the tires with small stiffness. Vibrations of light autonomous vehicles are measured and analysed in various scenario including asphalt road, cobblestone road and offroad applications. Experiments show that most of vibration appear at low frequencies owing to the filtering effect of soft tires and suspensions. Moreover, the excitation due to the tread blocks impacting on a smooth hard surface is observed. The second part of the thesis aims to develop an hybrid harvester able to collect energy from vehicle vibrations and from wind. After an introduction to energy harvesting from road induced vibrations of vehicles, vortex-induced-vibration (VIV) harvesters are studied, analyzing experimentally the effects of the design parameters on the performance. Then, a novel mathematical model of the hybrid harvester is proposed and validated in the case of vortex excitation combined with harmonic and random base vibration. Finally, the proposed model is used to investigate the harvester behaviour in other conditions. In particular, the effect of the measured vehicle vibrations is simulated. Experimental and numerical results demonstrates that the harvester can collect energy synergically from both the source of excitation.