机械电子毕业设计外文文献翻译--一个简单的方法来控制运动中的自重构机器人(编辑修改稿)

机械电子毕业设计外文文献翻译--一个简单的方法来控制运动中的自重构机器人(编辑修改稿)内容摘要：

modules are powered through cables. Refer to for more details and videos of the experiments reported later. 5. Experiments In this section we describe three different lootion gaits implemented using rolebased control. For each gait we have chosen to report the length of our programs as a measure of the plexity of the control algorithm. These results are used to support our claim that the implemented control systems are minimal. We also report the speed of the lootion patterns, but this should only be considered an example, the reason being that in our system the limiting factors are how robust the modules physically are, how powerful the motors are, and how much power we can pull from the power source. To report a top speed is not meaningful before we run the robot autonomously on batteries. . Caterpillar lootion We connect eight of our modules in a chain and designate the male opposite the female connector to be the parent connector. We then implement the algorithm described above with the following parameters. T = 180, _ pitch(t) = 50◦ sin 2π t , T yaw(t) = 0, d = 51 T. (1) Pitch and yaw is measured in a coordinate system where a yaw and a pitch of zero mean that the joints are straight. The motor control of our modules makes the joint go to the desired angle as fast as possible. This means that waypoints have to be specified to avoid jerky motion. The period T can be used to control the number of waypoints and therefore the smoothness and speed of the motion. The action sequence is an oscillation around 0◦ with an amplitude of 50◦ for the pitch angle and the yaw joint is kept straight. Each module is delayed onefifth of a period pared to its parent. The modules are connected and after they synchronize a sine wave is traveling along the length of the robot. Refer to Fig. 2. This produces caterpillarlike lootion at a speed of 4 cm/s. Note that it is easy to adjust the parameters of this motion. For instance, the length of the wave can be controlled using the delay. The program is simple. The main loop contains 13 lines of code excluding ments and labels (shown in Fig. 2). The initialization including variable and constant declaration amounts to 18 lines of code. Fig. 3. A snapshot of sidewinderlike lootion. lines of code. The parameters for the eight module rolling track are: T = 180, 2π 60◦ 21 T, pitch(t) 1 − sin t if t ≤ _ _ T __ = 60◦ if t 1 yaw(t) 2 T, = 0, d = 41 T. (3) Unlike the controller for the sidewinder gait and the caterpillar gait this controller only works with eight modules, because of the physical constraint. It might be possible to make a more general solution by making pitch(t) and d a function of the number of modules. The number of modules in the loop could be obtained by the leader by including a hop count in the signal. 6. Handling a general configuration We saw in the previous section that we had to introduce IDs to find a unique leader in a configuration that contains loops. Introducing the ID mechanism unfortunately ruins the opportunity to use the synchronization algorithm to automatically find a leader in a tree structure, because synchronization signals are only propagated down in the configuration tree. In fact, the loop algorithm will fail in this situation unless the module with the highest ID also happens to be the root. In order to make a general algorithm the synchronization signal has to be propagated both upward and downward in the tree. 7. Discussion An important issue in the design of control algorithms for selfreconfigurable robots is that the algorithms should still be efficient in systems consisting of many modules. Rolebased control is only initially dependent on the number of modules, because it decides how long it takes for the synchronization signal to be propagated through the system. After this startup phase it takes constant time to keep the modules synchronized implying that the algorithm scales. In rolebased control all modules run identical programs and there is no representation of a modules position in the configuration. Therefore, the system is highly robust to reconfiguration. In fact, the caterpillar can be divided in two and both parts still work. If they are reconnected in a different order they will quickly synchronize to behave as one caterpillar again. This also implies that the system is robust to module failure. If a module is defect and it can be detected this module can be ejected from the system and the remaining modules when reconnected can continue to perform. Finally, if a synchronization signal is lost it is not crucial for the survival of the system. If a signal is lost it just means that the receiving module and its children will be synchronized a period later. In rolebased control the synchronization signal is only sent once per period. This means that in order for the modules to stay synchronized the time to plete a period has to be the same for all modules. In the experiments presented here the cycles take the same amount of time, but in more plex control systems where other parts of the control system use random amounts of putation time this cannot be assumed to be true. This problem can easily be handled by using timers. Even though timers are not precise enough to keep modules synchronized over a long period of time they can be used for this purpose. In the work presented here we have shown what can be achieved using as simple a control algorithm as possible. In related work we have investigated how we can extend the algorithm to handle more plex lootion gaits. W。