Basic Research Of Five-leg Parallel Virtual Machine Tool

The parallel robots based on Stewart platform have gained further development.they have 6-DOF(except that of Northeast University).But there are some structure-design shortcomings in these robots: the six-unstable poles all are jointed with the platform by sphere-chains. The position precise of sphere-chains directly effects the precise of parallel robots, and increases the difficulty of manufacture. The analysis and manipulator of the six-unstable poles is very difficult. Particularly, the DOF rotating with the normal is unnecessary as to parallel machine tool.The new type of virtual machine tool based on compound sphere joint.Use the compound sphere joint replace the moving plantform,the new parallel robot has only five poles. Three of them are joined by a three-layer compound sphere joint. Two of them are joined by a two-layer compound sphere joint. Compared with the six-pole virtual machine tool, this new structure virtual machine tool has the same practical DOF.relieve coupling, its control is easier.the structure of machine tool will be simpler. In addition. resolution and anti-resolution can be processed based on it conveniently, performance of manufacture and assemble of it is nice and high precision can be obtained. Therefore it has a wide prospective outlook in space curve-plane manufacturing fields.This paper has also analyzed the structure of five-pole machine tool. What's more, the structure of compound sphere joint, the key one, is designed and deeply studied, position anti-resolution of model of machine tool, together with speed, acceleration, forces on every pole and workspace, is calculated and analyzed.