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Planning and Navigation

                           6.2.2.11   Other approaches                                         287
                           The approaches described above are some of the most popularly referenced obstacle avoid-
                           ance systems. There are, however, a great many additional obstacle avoidance techniques
                           in the mobile robotics community. For example Tzafestas and Tzafestas [148] provide an
                           overview of fuzzy and neurofuzzy approaches to obstacle avoidance. Inspired by nature,
                           Chen and Quinn [56] present a biological approach in which they replicate the neural net-
                           work of a cockroach. The network is then applied to a model of a four-wheeled vehicle.
                             The Liapunov functions form a well known theory that can be used to prove stability for
                           nonlinear systems. In the paper of Vanualailai, Nakagiri, and Ha [153] the Liapunov func-
                           tions are used to implement a control strategy for two-point masses moving in a known
                           environment. All obstacles are defined as antitargets with an exact position and a circular
                           shape. The antitargets are then used when building up the control laws for the system. How-
                           ever, this complex mathematical model has not been tested on a real-world robot to our
                           knowledge.

                           6.2.2.12   Overview
                           Table 6.1 gives an overview on the different approaches for obstacle avoidance.


                           Table 6.1
                           Overview of the most popular obstacle avoidance algorithms
                                       model fidelity     other requisites          performance

                             method                  view                sensors  tested  robots
                                       shape  kinematics  dynamics  local  map  global  map  path  planner  cycle  time  architecture  remarks




                                 Bug1  [101, 102]  point  local         tactile                very inefficient,  robust




                             Bug  Bug2  [101, 102]  point  local        tactile                inefficient,  robust


                                 Tangent Bug  [82]  point  local  local tangent  graph  range  efficient in many  cases, robust
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