| 1. Put forward of the questionThe mobile robot is an important branch of robotics, and the study of the mobile robot is a new research field which is raised after the 80's of last century. With the advancements of the fields of computer, sensor and control,the developments of the mobile robot also enter into a higher stage. In general, the mobile robot refers to the robot moving on the ground, and it mainly includes the mobile robot which is used in military affairs and in our daily life. In addition, from wider meaning space exploration robot and under-water robot also belong to the category of the mobile robots. With the development of times, it must press close to our life even more, and it also will play a bigger role too in the military affairs at the same time. So there is a deep actual meaning on this subject's research. But the mobile robot must face the existence of a large amount of uncertain information of external world during the course of its job, so it becomes a key technique of how to enhance the robustness of mobile robots' control system, which make it can carry on the adjustment of the location accurately and fast and the tracking trajectory accurately in the complicated external environment. The purpose of the paper is to seek a kind of control algorithms with great robustness which is easily realized through real-time hardware, and it can make the mobile robot to track the layout trajectory accurately and fast.2. The framework of the mobile robotThe whole structure of the mobile robot is made up of three major parts: sense organization, control organization, moving organization.(1) Sense organization: The mobile robot uses vision navigation, and the sense organization is mainly made up of the image gathered unit, A/D conversion unit and image processing unit.(2) Control organization: The mobile robot uses single-chip microcomputer as the core processing unit of the control algorithms, direct current servomotor as the power drive setting to adjust the state of the mobile robot.(3) Moving organization: The mobile robot uses the wheeled structure of two driving wheel and universal wheel. Speed sensor is fixed on the wheel axes to detect the real-time speed of the mobile robots.3. Difficulties of the study(1) The mobile robot is a very complexly multi-input and multi-output non-linear system, and it has the dynamics characteristic of time variant, coupling and non-linear. So it is complicated to control. Because of the imprecision of measuring and modeling and the influence of changed-load and outside flexibility, in fact we are unable to get the model of the mobile robot accurately and integrally, so we must face the existence of a large number of uncertain factors of the mobile robot.(2) The nonholonomic constraints factor such as the roll-contact with outside environment needs to be considered, so in fact the mobile robot belongs to a kind of nonholonomic constraints system. It is very complicated to control this kind of systems because of the following some new characteristic.1) Essentially, nonholonomic constraints are dynamic constraints, so we are unable to change it into simple algebra constraints equation by integral operation, which make it very difficult to control and locomotion layout.2) Nonholonomic constraints system can't realize linearization exactly and asymptotical stability of balance point by sliding or continuous pure state feedback. So most of the works are mainly based on constructing of sliding, continuous pure state feedback and discontinuous state feedback controller. This method need the exact kinematics model and dynamics model, and the speed of attenuate is slow, so it has undesirable effect to be used on real-time control.4. Research of the paperTo the question that we have analyzed above, combining with the characteristic of our experimental apparatus we make some research as follows: (1) Because the nonholonomic mobile robot is unable be controlled through sliding and continuous pure state feedback, we use discontinuous sli...
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