Stefano Pagano

Rocker–bogie suspension systems have been extensively employed in planetary exploration rovers due to their ability to traverse highly irregular terrains while maintaining ground contact. Traditionally, their mechanical behavior has been analyzed using quasi-static models, given the low operational speeds typical of space missions. However, similar configurations are now being proposed for terrestrial applications in agriculture, defense, and logistics, where higher traversal speeds and more varied terrain conditions require a deeper understanding of the system’s dynamic response. This study analyzes some aspects of the kinematic and dynamic behavior of a rover with rocker–bogie suspension while traversing an obstacle with a harmonic profile. Both quasi-static and dynamic simulations are conducted, focusing on the time-varying contact forces at the wheels. Key findings include identifying the rate at which load reduction at which the load on one wheel becomes zero and the wheel tends to lift off the ground. These threshold speeds are mapped as a function of height and wavelength of the bump, providing design insights for applications requiring higher traversal speeds on uneven terrain. The analysis may also prove valuable for rovers equipped with visual sensor systems capable of mapping their surroundings and identifying obstacles, to determine whether they can be traversed and, if so, at what maximum speed. An experimental investigation was conducted with a small-scale rover to verify the theoretical results, for which the threshold speed was found to be 0.3 m/s, calculated for h = 16 mm and λ = 80 mm.

This paper aims to analyze a six-wheeled mobile manipulator as a solution for brush clearing difficult areas. To this end, a rover with a rocker–bogie suspension system, like those used for space explorations, is considered; the cutting head is moved by a robotic arm fixed to the rover so that it can reach areas to clean in front of the rover or on its sides. The change of the pose of the robotic arm shifts the centre of mass of the rover and, although the shift is not important, it can be used to improve stability, to overcome an obstacle, or to change the load distribution between the wheels to prevent the wheels from slipping or sinking. Some analyses of the interaction between the rover and robotic arm are reported in this paper. To prevent the rover from entering a low-grip area, the possibility of estimating the grip conditions of the terrain is considered, using the front wheels as tactile sensors. By keeping the rear wheels stationary and gradually increasing the torque on the front wheels, it is possible to evaluate the conditions under which slippage occurs. In case of poor grip, using the other drive wheels, the rover can reverse its direction and look for an alternative path.

Periodic monitoring of large industrial and civil structures is carried out through static and dynamic measurements. The monitoring, carried out over many years, offers important information for evaluating the health of structures and their management. Dynamic tests are carried out starting from measurements of the vibrations of the structure induced by mechanical devices or by the surrounding environment. If a ground support element is available, it is possible to exert a forcing action on the structure using actuators fixed to the support. When a ground support is unavailable, the structure can be forced using devices comprised of masses with rotary or reciprocating translational motion. These masses must be large enough to excite appreciable mechanical vibrations of the structure. In this paper, a vibration exciter, based on a mass suspended on an air spring and forced to vibrate at the resonant frequency, is proposed. Thanks to the resonant condition, the force transmitted to the structure is amplified compared to that applied to the mass. The excitation frequency can be adjusted by altering the inflation pressure of the air spring to modify the natural frequency of the system. In the paper, after the presentation of some mechanical devices used as vibration exciters for large structures, the proposed device is described and the first experimental results are reported.

The protection of structures and machines from ground vibrations is a deeply felt and widely studied problem. These vibrations are typically generated by the operation of machines, vehicular traffic, seismic events, shocks, explosions, etc., and are generally characterized by frequencies that are not known a priori, making the use of passive isolation systems problematic. Just away from the source, ground vibrations have a predominantly horizontal component. To meet the conflicting requirements of passive isolation systems, which should have higher stiffness when the structure is at rest and lower stiffness when the ground forces it to vibrate, active or semi-active isolation systems can be adopted. In the following article, the possibility of adopting a hybrid isolator is evaluated; it consists of shear-stressed elastomeric pads coupled with an electromagnetic actuator; the latter consists of three coils, two of which are connected to the ground and the other one to the body to be isolated. This kind of isolator has the same flexibility and adaptability as the active ones, with the advantage of ensuring its functioning even in the absence of an external energy source. Its flexibility is due to the presence of a smart element that allows one to tune the characteristics of the isolator to consider the instantaneous isolation requirements. The proposed solution allows one to modify the isolation system’s characteristics in a sufficiently wide range of displacements equal to that defined by the maximum allowed deformation of the elastomeric pads. This paper reports the description of the isolation system and an analytical model to describe its restoring force; then, an experimental setup is adopted to identify the parameters of the analytic model; finally, several simulations are reported to compare the analytical and the experimental trends of the restoring force and to characterize the isolator.