Mobile Robots - Moving Intelligence Part 6

Tham khảo tài liệu 'mobile robots - moving intelligence part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | A Fuzzy Logic Controller for Autonomous Wheeled Vehicles 191 The following is a sample of the rules of this module If v is B d0 is Z and Av is P then AAgb3is NB The rule states that if the velocity is big the minimum measured distance to the nearest obstacle is zero and the change of velocity is positive the controller should supply a big brake angle. If v is S d0 is S and Av is N then AAgb3is Z This rule states that if the velocity is small the minimum measured distance to the nearest obstacle is small and the change of velocity is negative the controller should do nothing. The full rule set of this module is shown in Table 7. v h do Av h Z S B Z N PS PS Z Z PS PS Z P NS Z Z S N PS Z Z Z PS Z Z P NS NS Z M N NS Z Z Z NB NS Z P NB NB Z B N NS NS Z Z NB NS Z P NB NB Z Table 7. Rules for Cornering Throttle Fuzzy Module. 6. Tuning Target Throttle Fuzzy Module Tests show that cornering throttle and obstacle avoidance modules performed adequately after little manual tuning. However the Target Throttle Fuzzy module consistently produces an oscillatory vehicle velocity profile as the vehicle approaches the target. Manual tuning of the membership functions and rules fails to improve the performance of this module. While the rules of this module generally fit within the driving patterns of most drivers this oscillatory behavior can be easily explained by considering that two objectives of this module compete with each other near the target i. Slowing down the vehicle as the vehicle approaches the target. ii. Maintaining a non-zero velocity to ensure that the vehicle does not stop before reaching the target. Usually drivers solve this problem by pressing the gas or brake pedals lightly when they approach their final target. Narrowing the ranges of the membership functions of the output variable of a fuzzy controller may simulate this behavior. The design presented here proposes an adaptive tuning method to smooth the velocity of the vehicle as it approaches the target. Since

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