tailieunhanh - Field and Service Robotics - Corke P. and Sukkarieh S.(Eds) P8

Nhiều chương trình CAD hiện nay cho phép tạo ra các mô hình ba chiều để có thể nhìn từ mọi góc độ. Các chương trình CAD mô hình hóa vật thể đặc tiên tiến là một hệ thống thiết kế hiện thực ảo. Những mô hình đặc như vậy có thể được dùng làm cơ sở cho các phân tích phần tử hữu hạn (FEA) và / hoặc tính toán động lực dòng chảy (CFD) của thiết kế. Cho đến ứng dụng gia công với trợ giúp máy tính (CAM), những mô hình này cũng có thể được dùng. | Development of a Control System of an Omni-directional Vehicle 247 Fig-1- Overview of the mechanism Fig-2- Prototype Vehicle and Special wheel Free Roller Side View Front View 2-2 Kinematics The vehicle s configuration position and attitude are defined by the body parameters R1 R2 and wheel rotation velocity values w1 . w7 in Figure 3. Here equation 1 indicates the wheel rotation velocity. Wi kVi i 1 . 7 1 where r radius of the wheel mm wi rotation velocity of the wheel i rad s V rotation velocity of the actuator i rad s k gear ratio between the actuator and the wheel Now X x y Ó T and V V1 V7 T express the motion velocity vector of the vehicle and the rotation velocity vector of the actuators respectively. V is also derived by using X in equation 2 . V J X 2 248 D. Chugo et al. where J is pseudo inverse of Jacobian matrix 1 0 R2 0 -1 R1 J J J -1 JT 1 -10 R2 k 10 r2 0 1 r1 -10 r2 3 Fig-3. Coordination and parameters Problem Specification The developed vehicle has redundant actuation system using seven wheels. Thus our system has to synchronize the wheels with following each control reference which is calculated by equation 2 using Jacobian. However during the robot passes over the irregular terrain the load distribution to each wheel is complex problem. Therefore it is difficult to synchronize among the wheel. If the system fails to take the synchronization among the wheels the vehicle will lose the balance of the body posture as shown in Figure 4. Thus each wheel has to synchronize with the others when the vehicle runs on the rough terrain. In related works some traction control methods for single wheel are already proposed. However they do not discuss synchronization of the wheels for running on rough terrain. For our system we must consider the synchronization among the wheels. We explain our proposed method in next section. 3 Control System Proposed method In order to synchronize the wheels rotation during the vehicle passes over the step calculated .