Zhongfei Wang

Optimal Design of Parallel Robots for the Prescribed Regular Dexterous Workspace

This paper presents a method for determining design parameters of parallel robots (PRs) in its optimal kinematic design. To produce a more compact and economical PR, the determination of an optimal workspace is important. This includes defining a workspace that encases the prescribed regular dexterous workspace (PRDW). Two requirements should be simultaneously satisfied: (i) the local or global performance index; (ii) a regular shape. In this paper, the optimal problem is firstly discussed and translated into two linear problems. Then, an optimal design procedure which adopts the generalized pattern search algorithm in the genetic algorithm and direct search toolbox of Matlab is proposed to solve these problems. Taken as an example, a linear Delta robot is designed for the four different PRDWs, and its optimal result provides some useful information in measuring the distance between a PRDW and the maximal sized normalized robot. On the basis of the value of distance, some wrong solutions of PR are clarified. It is concluded that the optimal design method is useful for the design and comparison of a general PR.

Optimal design of a linear Delta robot for the prescribed cuboid dexterous workspace

This paper presents a new idea to determine a set of optimal design parameters of a linear delta robot (LDR) whose workspace is as close as possible of being equal to a prescribed cuboid dexterous workspace (PCDW). The optimal design procedure on the basis of three algorithms is introduced in this paper. The kinematic problem is analyzed in brief to determine the design parameters and their relation. Two algorithms are designed to determine the reachable, rectangular dexterous workspace, and the maximal inscribed rectangle of dexterous workspace in the O-xy plane. Another algorithm is used to solve the optimal problem. As applying example, the results of four cases PCDW to LDR are presented. And the design result is compared with a new concept of the distance between the best state of the LDR and the requirement of the operation task. The method and result of this paper are very useful for the design and comparison of the parallel robot.

A Methodology for Determining the Reachable and Dexterous Workspace of Parallel Manipulators

A methodology is proposed for determining the reachable and dexterous workspace of parallel manipulators. The determination of two types of workspace is utmost important in optimal design and comparing performances of the manipulators because each configuration or point in this region has specified kinematic dexterity by designer. The method is based on a stratified workspace boundary search technique, which is referred to as stratified workspace boundary determining methodology (SWBDM), and considers the various physical and contrived constraints. After the two similar problems of the determination of two types of workspace boundaries were defined, we propose a unified method to solve these problems. The validity and efficiency of the proposed method are verified with two kinds of representative parallel manipulators, since their relational results were studied in literatures. Finally, we conclude some advantages of the proposed methodology by comparing with other methods.

A Methodology for Determining the Maximal Regular-shaped Dexterous Workspace of the PMs

A methodology for determining the maximal regular-shaped dexterous workspace (MRsDW) of parallel manipulators (PMs) is proposed. The MRsDW is the maximal subset of the dexterous workspace with prescribed dexterity, and has a regular shape such as a circle or rectangle for the planar and a cuboid or cylinder for the spatial situation. It is one of the objects of optimal design of the PMs while the workspace size and shape are considered. The concept of the utilizable ratio of dexterous workspace (URDW) is introduced, which is a new measure for the rationality of design parameters of a PM. The methodology based on the stratified workspace boundary search technique can determine both the dexterous workspace and their MRsDW. After the problem of determination of the MRsDW is defined formally, a numerical method is proposed to solve this problem by three algorithms. Finally, the validity and efficiency of the proposed method are verified through application of the 2-DOF planar PM and the linear delta robot.

Optimal design of a linear delta robot for the prescribed regular-shaped dexterous workspace

This paper follows a method to determine a set of optimal design parameters of a linear Delta robot (LDR) whose workspace is as close as possible of being equal to a prescribed regular-shaped dexterous workspace (PRsDW). The design process proposed in this paper considers the particularity of the LDR. The kinematic problem is analyzed in brief to determine the design parameters and their relation at first. Two kinds of PRsDWs are considered, one is cylindrical dexterous workspace and the other is cuboid dexterous workspace. The optimal design parameters corresponding to the two kinds of PRsDWs are obtained by means of generalized pattern search algorithm (GPSA) in the genetic algorithm and direct search toolbox of Matlab, and the results of each PRsDW are compared to see the reasonability to the different operation tasks. The method and result of this paper are very useful for the design and comparison of the parallel robots.

A Y-Star Robot: Optimal Design for the Specified Workspace

This paper adopts a methodology to determine a set of optimal design parameters of a Y-Star robot whose workspace is as close as possible of being equal to a prescribed cylindrical dexterous workspace (PCDW). Two requirements should be satisfied simultaneously: (i) the local or global performance index; (ii) a regular shape. The kinematic problem is analyzed in brief to determine the design parameters and their relation at first. The optimal design problem with nonlinear constraints is discussed and then translated into two optimal problems without constraints. Then, an optimal design procedure which adopts the generalized pattern search algorithm in the genetic algorithm and direct search toolbox of Matlab is adopted to solve these problems. As an applying example, the results of four cases of PCDW to the robot are presented. And the design results are compared with a concept of the distance between the best state of the robot and the requirement of the operation task. The methodology and result of this paper are very useful for the design and comparison of the Y-Star robot.

Output properties of cellular artificial actuator

This paper focuses on output properties of cellular artificial actuator. The actuator is built from small actuator cells with structural elasticity. These cells are connected together in series to form fibers, which are in turn connected in parallel to form the whole actuator. These cells are controlled to determine whether to be in a contracted, or ON, state or a relaxed, or OFF, state. Arranging the ON cells in different fibers of fixed topology gives different output properties. A model of actuators stochastic behavior is firstly deduced. Then, the output properties of actuator in a fixed topology are exactly calculated. A SMA springs array with three rows and five columns are built to validate the algorithm. Effect of the SMA spring array with different activated cells on tensile is analyzed, and experiment data indicates there exists a serious coupling phenomenon within the SMA springs array. Finally, comparison of application of these two different analysis methods is presented.

A family of spatial translational parallel robots

This paper focuses on the construction approach of a family of spatial translational parallel robots (STPRs) whose actuated joint of each limb is a prismatic joint and is fixed in the base. This family of robots has potentially wide range of application in the field of industry due to their high stiffness and acceleration. A lot of topological limbs were proposed in the literatures. But, how construct all possible STPRs by a topological limb is an open problem. All possible topological limbs are listed firstly, which are consisted of prismatic, revolute, and some compositive joints. Then, all possible layouts of three actuated prismatic joints in the base are analyzed in terms of the number of absolute direction of the prismatic joints, and each layout is depicted fairly through corresponding structure parameters. Additionally, the assembly conditions and the construction approach of a family of STPRs are given respectively. Finally, all possible STPRs belong to this family are obtained.

A family of 3-PRPaR spatial translational parallel robots

This paper focuses on a family of 3-PRPaR spatial translational parallel robots whose the moving platform is linked to the base by three PRPaR topological limbs, and the P joint fixed in the base acted as a actuated one in each limb. A systemic approach is employed to find all possible parallel robots of this family. Firstly, two types of the PRPaR limbs and their normal subgroups are defined base on the geometrical relationships between the passive R joints and actuated P joint on the limb. Then, the assembly condition of three limbs is given by means of the concept of conjugate subgroup. According to the assembly condition and the proposed method in the reference, all parallel robots of this family are finally found and are classified as six subsets by the type of layout of three actuated P joints on the fixed base. Discover the proposed parallel robots with three PRPaR limbs in other literatures are special cases of this family. The analysis method of in this paper is used for finding other family of parallel robot when other type of topological limb is considered.

Optimal Design of a Y‐Star Robot for the Prescribed Cylindrical Dexterous Workspace

This paper determines a set of optimal design parameters of a Y‐Star robot whose workspace is as close as possible of being equal to a prescribed cylindrical dexterous workspace (PCDW). Two requirements should be satisfied: (i) the local or global performance index; (ii) a regular shape. The kinematic problem is analysed in brief to determine the design parameters and their relation. The optimal design problem is discussed and then translated into two linear problems. Then, an optimal design procedure which adopts the generalized pattern search algorithm in the genetic algorithm and direct search toolbox of Matlab is adopted to solve these problems. As applying example, the results of four cases PCDW to the robot are presented. And the design result is compared with a concept of the distance between the best state of the robot and the requirement of the operation task. The method and result of this paper are very useful for the design and comparison of the Y‐Star robot.