tailieunhanh - Mobile Robots Navigation 2008 Part 11

Tham khảo tài liệu 'mobile robots navigation 2008 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 388 Mobile Robots Navigation 14 Here the plus minus sign of 14 denotes that the reference dcirc will generate a left or right turn. That is the robot will turn left right if it is following an object at its left right side. Then replacing 14 into 13 and considering its time derivative we obtain ề écirc -M m. 15 In order to analyze the stability of this control system consider the following Lyapunov candidate function and its time derivative v e 2 16 Vg ẽể è - w . Now to achieve the control objective the following control actions are proposed V Vmax tà Kg tanh fcgff Kg o kg 0. 17 Finally by replacing 18 in 17 the asymptotic stability of the control system can immediately be proved. That is this controller guarantees that the robot will perform a circular path by acting only on the robot angular velocity. Handling possible collisions This behavior is activated when an obstacle appears in front of the robot at a distance dimpact dfront being dimpact the smallest distance to the obstacle measured inside the robot safety-area which is also characterized by and angle dimpact on the laser range finder framework. Also dfront defined in Section2 is selected to be equal to the actual robot wall distance dwall and dtat dfront. The objective of this behavior is to avoid possible collisions by rotating the robot until a free-path condition characterized by an empty safety-area is again achieved and dk T dk where k is the obstacle detection instant and T is the time during this behavior was active until switching to the wall-following behavior. Under the above mentioned conditions this behavior will always achieve a free- path condition satisfying dk T dk see Figure 9 . Analogously to the behavior described in it could be assumed that d 0 considering that d does not change at the beginning and at the end of this behavior. Stable Switching Control of Wheeled Mobile Robots 389 ddes dimpaat. front ddes Fig. 9. Handling possible collision situations a .