This article focuses on a multibody model of a new passive articulated suspension tracked robot. ... more This article focuses on a multibody model of a new passive articulated suspension tracked robot. The model of the vehicle is developed using the multibody software MSC Adams (acronym for automatic dynamic analysis of mechanical systems) in conjunction with the Adams Tracked Vehicle toolkit. The various subsystems that make up the vehicle assembly are described, with particular attention to the modeling strategies of the swing arms that constitute the suspension system and the characterization of the track belt. The multibody model allows the system performance to be evaluated in advance for fine-tuning of the design parameters and using different configurations, for example, with active and locked suspension. Efforts are also presented to validate the multibody twin against the real prototype, showing a good agreement with field experiments. Once validated, the digital twin is used to assess the performance of the innovative suspension system in various challenging environments.
Tracked robots are gaining interest in the current context of off-road mobile robotics, especiall... more Tracked robots are gaining interest in the current context of off-road mobile robotics, especially in soft-terrain applications, because they offer a large contact area with the ground, which provides better traction than wheels or legs. In this paper, a novel passively articulated tracked robot is introduced. On each side, Polibot features a rubber track wrapped around four independently suspended road wheels, an idler wheel, and the sprocket, and it can adapt to many kinds of terrain. An inverse kinematic model for the proposed architecture is also developed to predict the system configuration given the terrain topography. The analytical model is based on constraint equations and a quasi-static force analysis, and it is validated against results obtained from the real prototype, showing good agreement. It can also be used to evaluate the influence of the many suspension design parameters and operating conditions, proving that it can be a useful tool for the proper setup of the robot.
Advanced control and driving assistance systems play a major role in modern vehicles, ensuring hi... more Advanced control and driving assistance systems play a major role in modern vehicles, ensuring higher standards of safety and performance. Their correct operation extensively depends on the knowled...
The continuously variable transmission with infinite ratio range could be utilized in automotive ... more The continuously variable transmission with infinite ratio range could be utilized in automotive industries for automatic change gear without the need of the friction clutch. In this work we study the performance of a mid passenger car provided with Infinitely Variable ...
This paper proposes a one-dimensional continuous model of the steel pushing V-belt, which describ... more This paper proposes a one-dimensional continuous model of the steel pushing V-belt, which describes the shifting dynamics of the CVT transmission during rapid speed ratio variations. The model investigates the influence of the clearance among the steel segments on the belt dynamics. The plates and pulleys strain motion is neglected, with respect to their rigid body motion, for the evaluation of the friction forces. The power transmission is assured only if an active arc exists where the plates are pressed against each other and where compressive forces arise among the steel segments. Conversely on the idle arc the steel plates are separated and no longitudinal compressive forces exist among the metal segments. The paper shows a significant difference in dynamical behavior between the drive and the driven pulley. Moreover, differences also exist between the pitch radius increasing phases and pitch radius decreasing phases.
We present a theoretical approach to estimate the fluid leakage in flat seals. The approach is ba... more We present a theoretical approach to estimate the fluid leakage in flat seals. The approach is based on the analogy between the seal-substrate interface and a porous medium. We assume that the interface is constituted of a random distribution of noncontact patches (the pores) and small but numerous contact spots (islands). Leakage may occur only through the pores, of which the lateral size and height are distributed according to a probability density function that we calculate on the basis of a recent theory of contact mechanics. Our theoretical approach is based on a percolation scheme that has never been proposed before and we believe it could be useful to stimulate further theoretical or experimental investigations. Within this percolation scheme we apply critical path analysis to calculate the hydraulic conductivity of the medium and compare our predictions with other calculations very recently presented to the scientific community.
This paper presents results coming from a non-linear model predictive controller used to generate... more This paper presents results coming from a non-linear model predictive controller used to generate optimized trajectories specifically for an omnidirectional robot equipped with a spraying unit to mark on the floor the perimeter of dangerous areas or to move large palletized goods inside warehouses. Results on different trajectories and with moving obstacles are provided along with considerations on the controller performance.
This article focuses on a multibody model of a new passive articulated suspension tracked robot. ... more This article focuses on a multibody model of a new passive articulated suspension tracked robot. The model of the vehicle is developed using the multibody software MSC Adams (acronym for automatic dynamic analysis of mechanical systems) in conjunction with the Adams Tracked Vehicle toolkit. The various subsystems that make up the vehicle assembly are described, with particular attention to the modeling strategies of the swing arms that constitute the suspension system and the characterization of the track belt. The multibody model allows the system performance to be evaluated in advance for fine-tuning of the design parameters and using different configurations, for example, with active and locked suspension. Efforts are also presented to validate the multibody twin against the real prototype, showing a good agreement with field experiments. Once validated, the digital twin is used to assess the performance of the innovative suspension system in various challenging environments.
Tracked robots are gaining interest in the current context of off-road mobile robotics, especiall... more Tracked robots are gaining interest in the current context of off-road mobile robotics, especially in soft-terrain applications, because they offer a large contact area with the ground, which provides better traction than wheels or legs. In this paper, a novel passively articulated tracked robot is introduced. On each side, Polibot features a rubber track wrapped around four independently suspended road wheels, an idler wheel, and the sprocket, and it can adapt to many kinds of terrain. An inverse kinematic model for the proposed architecture is also developed to predict the system configuration given the terrain topography. The analytical model is based on constraint equations and a quasi-static force analysis, and it is validated against results obtained from the real prototype, showing good agreement. It can also be used to evaluate the influence of the many suspension design parameters and operating conditions, proving that it can be a useful tool for the proper setup of the robot.
Advanced control and driving assistance systems play a major role in modern vehicles, ensuring hi... more Advanced control and driving assistance systems play a major role in modern vehicles, ensuring higher standards of safety and performance. Their correct operation extensively depends on the knowled...
The continuously variable transmission with infinite ratio range could be utilized in automotive ... more The continuously variable transmission with infinite ratio range could be utilized in automotive industries for automatic change gear without the need of the friction clutch. In this work we study the performance of a mid passenger car provided with Infinitely Variable ...
This paper proposes a one-dimensional continuous model of the steel pushing V-belt, which describ... more This paper proposes a one-dimensional continuous model of the steel pushing V-belt, which describes the shifting dynamics of the CVT transmission during rapid speed ratio variations. The model investigates the influence of the clearance among the steel segments on the belt dynamics. The plates and pulleys strain motion is neglected, with respect to their rigid body motion, for the evaluation of the friction forces. The power transmission is assured only if an active arc exists where the plates are pressed against each other and where compressive forces arise among the steel segments. Conversely on the idle arc the steel plates are separated and no longitudinal compressive forces exist among the metal segments. The paper shows a significant difference in dynamical behavior between the drive and the driven pulley. Moreover, differences also exist between the pitch radius increasing phases and pitch radius decreasing phases.
We present a theoretical approach to estimate the fluid leakage in flat seals. The approach is ba... more We present a theoretical approach to estimate the fluid leakage in flat seals. The approach is based on the analogy between the seal-substrate interface and a porous medium. We assume that the interface is constituted of a random distribution of noncontact patches (the pores) and small but numerous contact spots (islands). Leakage may occur only through the pores, of which the lateral size and height are distributed according to a probability density function that we calculate on the basis of a recent theory of contact mechanics. Our theoretical approach is based on a percolation scheme that has never been proposed before and we believe it could be useful to stimulate further theoretical or experimental investigations. Within this percolation scheme we apply critical path analysis to calculate the hydraulic conductivity of the medium and compare our predictions with other calculations very recently presented to the scientific community.
This paper presents results coming from a non-linear model predictive controller used to generate... more This paper presents results coming from a non-linear model predictive controller used to generate optimized trajectories specifically for an omnidirectional robot equipped with a spraying unit to mark on the floor the perimeter of dangerous areas or to move large palletized goods inside warehouses. Results on different trajectories and with moving obstacles are provided along with considerations on the controller performance.
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