You are presented with multiple paper abstracts, alongside the associated literature review and chapter titles. Given the provided information, you are going to do a literature review. Please generate a coherent literature review that synthesizes the content, draws connections between different works, highlights major findings, and identifies any gaps in the existing research.

Literature Review Title: A Review of Active Mechanical Driving Principles of Spherical Robots 
Chapter Title:  Introduction 
1. Abstract of Cited Paper (BIB001):  This paper presents the design process of a spherical robot capable of autonomous motion, and demonstrates how it can become a tool in child-development studies. The robot, named Roball, is capable of intentional self-propelled movements and can generate various interplay situations using motion, messages, sounds, illuminated parts and other sensors. Such capabilities allow Roball to interact with young children in simple and interesting ways, and to provide the potential of contributing to the development of their language, affective, motor, intellectual and social skills. Trials done with 12-24-month-old children demonstrate how Roball can be used to study children's interest in a self-propelled and intentional device. An experimental methodology to conduct such studies is presented: it is based on quantitative and qualitative techniques to evaluate interactions, thus enabling the identification of challenges and opportunities in child-robot interaction studies. 
2. Abstract of Cited Paper (BIB002):  The use of remotely operated robotic systems in security related applications is becoming increasingly popular. However, the direct teleoperation interfaces commonly used today put a large amount of cognitive burden on the operators, thus seriously reducing the efficiency and reliability of these systems. We present an approach to alleviate this problem by exploiting both software and hardware autonomy. At the software level, we propose a variable autonomy control architecture that dynamically adapts the degree of autonomy of the robot in terms of control, perception, and interaction. At the hardware level, we rely on the intrinsic autonomy and robustness provided by the spherical morphology of our Ground-Bot robot. We also present a prototype system for facilitating the interaction between human operators and robots using our control architecture. This work is specifically aimed at increasing the effectiveness of the GroundBot robot for remote inspection tasks. 
3. Abstract of Cited Paper (BIB003):  In this paper, an omni-directional rolling spherical robot with telescopic manipulator (BYQ-IV) is presented. This robot is designed for territory or lunar exploration. It not only has features like straight line motion, circular motion, zero turning radius and obstacle avoidance, but also is able to accomplish tasks such as stably grabbing and delivering assemblies. The structure of the whole robot is divided into three sub-systems, including the motion driving system; the manipulator system and the stability maintain system. Moreover, the distribute control system of the robot based on ARM processor and wireless communication system are introduced and the software architecture of control system is analyzed. The experiment shows that the prototype of the spherical robot with telescopic manipulator (BYQ-IV) can stably grasp a static target and carry it to a new location. 
4. Abstract of Cited Paper (BIB004):  The driving ahead motion problem was considered for a family of spherical mobile robot which utilizes counter-weight pendulum motion for propulsion mechanism. A simplified dynamic model of driving ahead motion of the system was derived with respect to the drive motor torque as input, and the input-state linearization condition was checked. Based on this result, a full feedback linearization of the system was obtained. The resulting equations were then used to design two novel controllers. The first one was used to control the angular velocity of the shell within an acceptable rang. The second controller was utilized to keep the angle of the shell between the specified limits. Simulation results are provided to show the efficacy of the controllers using realistic data. Experimental results are presented where the controllers are implemented on a spherical robot, BYQ_III, which is developed in our laboratory. The experimental results show that the robot converges to a neighborhood of the desired angular velocity and angle within the acceptable stationary errors. 
5. Abstract of Cited Paper (BIB005):  This paper presents a spherical underwater robot which uses three vectored water-jet propellers as its propulsion system. In this paper we introduced the conceptual design of the spherical underwater robot including the hull, waterproof chamber, propulsion system. Then we develop a prototype of this spherical underwater robot. Finally, we carry out confirmatory experiments to verify the availability of the design of the spherical underwater robot. 
6. Abstract of Cited Paper (BIB006):  In this paper we present the underwater experiments for spherical underwater robot which is developed in our laboratory. First, we give a brief illustration for the dynamics modeling of single water-jet propeller. Then, the coordination of multiple water-jet propellers is introduced. Based on the coordination, we discuss the transforms of three basic motions, surge, heave and yaw. To evaluate the characteristics of these basic motions, we carry out different experiments for each basic motions. And finally, we give the experimental results and analysis for the results.

Literature Review:
Spherical robots are a promising area of research and have many unique features that are of interest to study. They can be designed to be sealed off from harsh environments, to operate holonomically (For the purpose of this paper, a holonomic system will be referred to in the robotics sense and not in the multi-body dynamics sense. A holonomic system in robotics is one whose orientation does not affect its desired direction of travel. For example, an automobile must point its front end towards its intended direction of travel. A spherical robot, if designed so, may change direction at any stage of movement without reorientating itself), and to rebound from collisions in a quick and non-destructive manner BIB001 . Spherical robots have begun to be used in underwater experiments BIB006 BIB007 , child development studies BIB002 , and security reconnaissance  BIB003 BIB004 . Some researchers have even begun to develop swarms of these of robots for task execution  . Due to the nature of a ball, a robot with a spherical shell will also follow the path of least resistance. The quintessential spherical robot would have true holonomy and hence would be able to move in any direction without having to change its orientation. The current research direction of spherical robots is heavily focused on the internal mechanics and the corresponding control systems. One design has not yet emerged dominantly among the others and diverse methodologies of internal driving mechanics have resulted in a wide range of robotic characteristics and capabilities. Due to the fact that research efforts are sporadic and uncoordinated, researchers have yet to create an optimized and efficient system BIB005 . Typically, the drive system of the spherical robot is located inside a shell. In order for the outer shell to rotate, the drive system must be able to transfer power to the outer shell in some manner: a fixed mechanical component such as a gear, an electromagnetic device such as a motor, etc. For true holonomy, the research challenge becomes developing an internal drive mechanism that can provide omnidirectional output torque to a sphere that can arbitrarily rotate around it, regardless of the orientation of either the sphere or the drive mechanism. In essence, the inner mechanics must be able to rotate three-dimensionally independently from the outer shell. Since the outer shell must be connected to the inner mechanics in some manner, this poses a difficult design challenge. However, there are numerous ways to solve this problem, but each method has its own set of obstacles. These obstacles have spawned many variations of internal propulsion devices, each one trading torque for holonomy, control for speed, etc. Some of these systems are simple, and some have complicated designs with even more complicated control algorithms. Teams have even begun to research propulsion by physically transforming the outer shell, which may lead to an entirely new family of robots. The following is a review of spherical robot internal-drive concepts and novel variations, the first being designs based on the concept of barycenter offset. The early and current majority of designs are based on the principle of shifting the equilibrium of a sphere BIB001 , the most common of which is shifting the sphere's center of gravity. This paper discusses the three major types of principles used to propel a spherical robot: barycenter offset (BCO) in Section 2, shell transformation (ST) in Section 3, and conservation of angular momentum (COAM) in Section 4. In the discussion of each type of principle, examples of how these types of principles are utilized will be discussed in the respective subsections. Also, novel enhancements such as legs, sensors, and reconfiguration are discussed where appropriate. Finally, a table of taxonomy in Section 5 will be presented showing the principles, basic utilizations, and power limitations associated with each.