Design and Prototyping of Autonomous Ball Wheel Mobile Robots

Mobile robots are platforms that are able to move autonomously. Now a day, their use is increased in different areas like, autonomous vehicles, flexible manufacturing and service environments and lunar explorations. A large number of wheeled or tracked platform mechanisms have been studied and developed to prove their mobility and capability as autonomous robot vehicles (Pin, and Killough, 1994), ( Kim, et al. , 2003), ( Wada, et al. , 2000), (Jung, et al., 2000), (Mori, et al., 1999). For large and heavy outdoor robots, four-wheel car-like driving mechanisms or skid–steer platforms have traditionally been used. These vehicles are quite restricted in their motion ( Jarvis, 1997), particularly when operating in tight environments. In recent years, study of nonholonomic systems has been an area of active research. Nonholonomic systems are characterized by nonintegrable rate constraints resulting from rolling contact or momentum conservation. Nonholonomic behaviors are sometimes introduced on purpose in the design of mechanism, in order to obtain certain characteristics and performances such as those in. One advantage offered by nonholonomic systems is the possibility of controlling a higher number of configurations than the number of actuators actually employed in the system, which is sometimes useful in terms of reducing the system’s weight and cost. The nonholonomic constraints cause complexities in trajectory planning and designing of control algorithms for feedback stability of the vehicle system. It is required that a suitable desired trajectory satisfying the above constraint be designed to control a nonholonomic mobile mechanism ( Fierro & Lewis, 1997). On the other hand, holonomic vehicles have been proposed with several advantages and disadvantages, so that there is introduced a control strategy to avoid a nonholonomic constraint of a wheel to implement a holonomic omnidirectional vehicle ( Asada & Wada, 1998). Holonomic vehicles, also, have some problems in practical applications such as low payload capability, complicated mechanism and limited accuracy of motion ( Ferriere & Raucent, 1998). Several omnidirectional platforms have been known to be realized by developing a specialized wheel or mobile mechanism. From this point of view, such specialized mechanisms suitable for constructing an omnidirectional mobile robot are summarized as following: 1. Steered wheel mechanism (Chung, et al., 2010), ( Wada, et al. , 2000)..