Study On The Joint Rotation Space (JRS), Workspace And Path Generation Of Planar Parallel Manipulators

Planar parallel manipulators can follow precisely any planar path in their workspace with high kinetic precision, high rigidity ,high capacity and good dynamic performances. Planar five-bar linkages are fundamental forms of planar parallel manipulators. Their joint rotation space(JRS) of both side bars and workspace of coupler points are basic issues in designing planar parallel manipulators. The study of the synthesis method for this kind of linkages is of practical significance.The main content of this thesis includes the following parts:(1) In Chapter 2, the conditions of link lengths are derived for the side bars to rotate as cranks. Two types of cranks are defined and then five-bar linkages are divided into four types, i.e. the full double-crank linkage, the double quasi-crank linkage and the double rocker linkage, and the crank-rocker linkage. The rotational ranges of the two side links for each type of the mechanism are analyzed, and the corresponding numerical algorithm is developed. Several examples are given to show the effectiveness of the analysis..(2) In Chapter 3, the conditions for the coupler point of the five-bar linkage to locate at the boundary of the workspace are derived , and an algorithm to draw the workspace boundary is put forward. Some examples are given to validate the algorithm. Two types of singularity are defined and then the whole workspace is cut into several singularity-free sub-workspaces. At last, a software about the JRS and workspace is developed in virtue of VC++ with which we can easily obtain the JRS of both side links and workspace of coupler points in any configuration mode of mechanism only if we input the dimensions of a five-bar mechanism.(3) Planar full-crank five-bar mechanisms without uncertainty singularity are chosen to construct a hybrid mechanism generating the given path. A mathematical model is set up to optimize the dimensions of five-bar mechanism with the minimal power consume of the controlling motor by the improved genetic algorithms. An example is given to show the effectiveness of the mathematical model.(4) A hybrid mechanism is designed and produced. The dimensions of this hybridmechanism is"from the result of the example in Chapter 4. A rotary encoder is used to gather the position signal of the crank, according to which micro-computer control the rotation of the setup motor assembled with the other side link in order to adjust the position of this side link. Only if we turn arbitrarily the crank connected to the rotary encoder, a given path is generated precisely.