# Susceptibility Modeling of a Rubber Track for Lightweight Mobile Robots
## 1 Introduction  
With the development of technology, mobile robots and UGVs (Unmanned Ground Vehicles) are gaining more and more widespread use in many areas of life [1; 2]. Their main capability is to directly replace humans in hazardous work environments. To achieve the necessary functionality, they are required to have an adequate mobility level for the working conditions, effectiveness in task performance [3], and sufficient energy reserve for the expected working time [4].  
In order to increase mobility, robots and UGVs are often equipped with tracked running gear [5; 6]. Compared with wheeled traction systems, tracked systems are characterized by lower pressures, a higher ability to overcome terrain with low load capacity, the ability to develop higher traction forces with less slip, and a greater ability to overcome terrain obstacles [7]. More and more often, instead of metal tracks, rubber tracks are used. They allow for driving on both paved roads and off-roads while ensuring quieter operation [8], a longer service life, and lower operating costs [9], as well as better traction characteristics and an advantageous distribution of ground pressure [10; 11], typical for tracks. For these reasons, they can be increasingly used in low-speed transport vehicles and agricultural tractors of various sizes, where they replace wheeled chassis [10; 11; 12; 13; 14].  
Experimental and simulation studies in the field of rubber track applications focus mainly on the prediction of traction forces and rolling resistance on deformable soils, taking into account the principles of terramechanics [15; 16; 17]. These studies show the high compatibility of heavy vehicle models; using them to model light robots and UGVs does not always bring satisfactory results [18]. Similar problems occur when modeling the energy efficiency of driving. Experimental studies show that the resistance and energy consumption, especially of lightweight robots, can be relatively higher than in the case of classic heavy-tracked vehicles with metal tracks [19; 20; 21]. The rolling resistance coefficient may be the main component of energy loss. Even on non-deformable surfaces, it may exceed 20% [3; 22].  
Research [19; 23] indicates factors that have a significant impact on the internal motion resistance of rubber track running gear: track scrolling speed, diameters of driving, idler,and road wheels, as well as stiffness and damping of the track belt, depending on the type of rubber and structure of the track belt. These properties not only increase the track bending resistance but also cause the track belt to heat up and increase its temperature [24; 25]. This may change its stiffness, lead to track elongation and shedding while driving, cause devulcanization, and accelerate the degradation of the track structure [26]. In addition, the stiffness of the track belt (its susceptibility to deformation) and the track tension have a dominant effect on the contact with the ground. Increased track-terrain contact improves ground pressure, tractive forces, and the general ability to overcome obstacles [17], which also depends on the applied running gear solutions [27; 28; 29]. It is therefore advisable to take these factors into account in the track modeling process, especially in systems with complex kinematics, moving on rough surfaces, and overcoming obstacles.