## 1 Introduction
It is also necessary to define the control system for both the analyzed structures and adopt a model of the robot's drive units, which may allow for the analysis of the energy efficiency of individual solutions. Therefore, the research methodology adopted in this work assumes the following:  
* Adopting the nominal parameters of the robot and the desired motion trajectory for simulation studies, as well as selecting the parameters of the control system;
* Introducing the quality indices for a quantitative assessment of the research results;
* Conducting simulation studies for the assumed range of the ratio of the wheel track to the wheel axle distance;
* Discussing the obtained results, taking into account the obtained motion path, and time histories of the selected physical quantities and quality indices;
* Formulating conclusions and answers to research questions;
* Indicating directions for further scientific work based on the obtained research results. The paper concerns the optimization of the design of a hypothetical robot, so its subject is in the area of applied sciences. The main contributions of the paper include the following:  
* The development of a robot dynamics model that can be used to optimize the robot design and test various solutions of control systems;* The application of a modified version of the Kiencke tire model, which is less common than other tire models, such as Pacejka [2];
* The development of a new variant of the pose controller;
* Simulation studies based on the developed robot model and the adopted control system structures, allowing us to answer the research questions regarding the influence of the robot's wheel track on the accuracy of movement and energy efficiency. The content of the further sections of the paper is as follows:
* Section 2 includes an introduction to the state of the art in the field of the modeling of wheeled mobile robots, in particular with non-steered wheels and taking into account the slip of the wheels. This section also covers a brief introduction to the state of the art in the area of tracking control of wheeled mobile robots. * Section 3 concerns modeling issues and a discussion of the kinematics of the analyzed six-wheeled skid-steered mobile robot, and the derivation of the robot dynamics model based on the Newton-Euler formalism, as well as supplementing the robot model with a model of drive units. * Section 4 concerns the problem of the motion tracking control of the analyzed mobile robot and covers a general description of the desired robot motion trajectory, as well as defining the structures of the robot control system, including the wheels' controller and an additional pose controller. * Section 5 focuses on simulation studies and includes the assumption of the nominal parameters of the robot, the type of desired motion trajectory, the selection of the settings of the wheels' and pose controllers, the adoption of quality indices, the presentation of the simulation study results, including the motion path of the selected robot point, and time histories of the selected physical quantities and quality indices, as well as a discussion of the obtained results. * Section 6 is a summary of the work and includes answers to key research questions, as well as an indication of directions for potential further scientific work.