סמינר מחלקה של אלדד סומנר - "מודל דינאמי של רכב היגוי-החלקה ארבע גלגלי".
School of Mechanical Engineering Seminar
Wednesday, July 3, 2024 at 14:00
Wolfson Building of Mechanical Engineering, Room 206
Modeling of a Four-Wheel Drive Skid-Steering Vehicle
Eldad SumneR
Unmanned Ground Vehicle (UGV) is a wheeled mobile robot that autonomously moves on the ground by sensing and interacting with its environment. The usage of UGV is quite extensive and applicable in the civil world, the military world and in space exploration. In the present study we focused on a type of vehicle known as Skid Steering vehicle. In a skid steering vehicle, all wheels or tracks remain parallel to the longitudinal axis of the vehicle. Therefore, steering is achieved by applying on each side of the vehicle's set of wheels, a different velocity.
One of the most significant challenges in modeling of a skid-steer vehicle is the consideration of the interaction between the wheels and the ground, since during motion, most of the time the wheels are not in a state of pure rolling, rather slipping. Furthermore, each wheel is also in a state of lateral slipping in the direction perpendicular to the longitudinal axis. This phenomenon is a fundamental characteristic of the dynamics of that type of vehicles.
numerous studies have been done on the subject of dynamic modeling of a skid steering vehicle over horizontal plane and in some, the slip of the wheels have also been incorporated. However, few studies have been dedicated to the development of a comprehensive dynamic model that includes wheels slippage, which is also capable of simulating the movement of the vehicle on an inclined plane. A main element in a motion on a non-horizontal plane is the effect of gravity on the reaction forces of each wheel with the ground, which directly affects the torque required from each motor, separately, in order for the vehicle to perform the desired maneuver.
In the current study, a comprehensive dynamic model of a 4-wheel steering-skid vehicle was developed, where the wheel slips and the resultant traction forces acting on the wheels were also incorporated in the dynamics. The developed dynamic model is based on a study done for a two-wheeled robot, in which a concept was developed whose essence is integration of the longitudinal and lateral slips of each wheel as generalized coordinates in the vehicle’s dynamics. This concept was tested in simulations and experiments on a real two-wheeled robot and showed a good approximation to reality.
In this study, for the first time, the aforementioned concept was incorporated in the dynamics of a 4-wheeled vehicle.
Another novelty this study presents, in order for the model to simulate motion on an inclined plane, is a concept based on the solution of a statically indeterminate problem for the calculation of the reaction forces on each wheel during the simulation.
The dynamic model was implemented using the Matlab/Simulink environment and has been simulated in several driving scenarios. The results showed that the model responded as expected and thereby, indicated on the model's capability to provide a good approximation to the behavior of a UGV in reality.
