| Summary: | 碩士 === 國立交通大學 === 工學院碩士在職專班精密與自動化工程組 === 98 === The eyeball mechanism is used to carry the vision system to make it freely rotating. The eyeball mechanism studied here is the one with three degrees of freedom which can be serial type (open loop) or parallel type (close loop). The parallel one is much stiffer than the serial one to make it suitable for the heavy loading and high position accuracy applications. However, the parallel one has smaller workspace than the serial one, and it is also harder to analyze its kinematics. These are the challenges and restrictions of implementing the parallel mechanisms in applications.
In this studying, a parallel type eyeball mechanism with three degrees of freedom was discussed, and this mechanism consists of three sets of serial type arms, one base, and one platform. The serial type arm is made of two links of which both ends have revolute joints, and the axis of each joint will coincide in one point. When the axes of the three actuators of this parallel mechanism are in one plane, this mechanism is called coplanar type ; when the axes are coincident, this is called collinear type ; otherwise is called general type.
In this studying,Denavit and Hartenberg Method was used to conduct the forward and reverse kinematic models of the general type eyeball mechanism. By adjusting the parameters of the reverse model of the general type, the reverse models of the coplanar and collinear types can be derived. In this studying,The model proposed here was also compared with the simulation results and the results of some special cases provided in the early literatures to assure the correctness of the proposed model.
The structure of this studying is arranged as follows. First, the mathematical model of the general type was conducted, then the conducted model with some prescribed assumptions and constraints was used to find the workspace and singularity map of the three type mechanisms stated above. After iteratively changing the model parameters and finding the best one, the values of the model parameters were determined and used to fabricate the mockup(NC-AE08) to check the results obtained in this studying.
The contribution of this studying is to providing a model of eyeball mechanism which can be used in the eye or wrist of a robot to carry the vision system to make the robot move faster and trace the moving objects and its surroundings more accurately.
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