Design and Analysis of a Novel Schönflies Motion Parallel Robot with Full Cycle Rotation

Due to the complex structures of multi-limbed parallel robots, conventional parallel robots generally have limited workspace, complex kinematics, and complex dynamics, which increases the application difficulty of parallel robot in industrial engineering. To solve the above problems, this paper proposes a single-loop Schönflies motion parallel robot with full cycle rotation, the robot can generate Schönflies motion by the most simplified structure. The novel Schönflies motion parallel robot is a two-limb parallel mechanism with least links and joints, and each limb is driven by a 2-degree of freedom (DOF) cylindrical driver (C-driver). The full cycle rotation of the output link is achieved by “…R-H…” structure, where the revolute (R) and helical (H) joints are coaxial. Mobility, kinematics, workspace and singularity analysis of novel Schönflies motion parallel robot are analyzed. Then, dynamic model is formulated based on the principle of virtual work. Moreover, a pick-and-place task is implemented by proposed Schönflies motion parallel robot and a serial SCARA robot, respectively. The simulation results verify the correctness of the theoretical model. Furthermore, dynamics performances of Schönflies motion parallel robot and serial SCARA robot are compared, which reveal the performance merits of proposed Schönflies motion parallel robot.

Kinematic Analysis and Optimal Design of a Novel Schönflies-Motion Parallel Manipulator with Rotational Pitch Motion for Assembly Operations

This paper presents a novel Schönflies-motion Parallel Manipulator with Rotational Pitch motion (SPM-RP) based on a single-platform fully-parallel mechanism. The analysis of position, workspace, velocity, and singularity of the SPM-RP is carried out in detail, and a dimensionless Jacobian is proposed to evaluate the manipulability of the SPM-RP. It is shown that the SPM-RP is kinematically position-decoupled, which possesses a large singularity-free workspace and excellent manipulability. The SPM-RP is actuated by four parallel prismatic actuators, enabling the manipulator to provide identical kinematic performance at all generic cross-sections perpendicular to the prismatic joint axes within its workspace. This paper thus proposes a reduced design optimization formulation, where the traditional optimization over the entire workspace is reduced to one on a representative workspace cross-section of the SPM-RP. The design optimization of the SPM-RP has been carried out by maximizing its manipulability over the total orientation workspace, which is crucial for precision assembly. A SPM-RP prototype has been developed based on the achieved optimal design. The mobility, orientation capability, total orientation workspace, and repeatability are tested and verified for the developed SPM-RP prototype. Experiments show that the SPM-RP achieves a large total orientation workspace with excellent precision performance.

Elastodynamics of a parallel Schönflies-motion generator

The authors propose a model of the elastodynamics of the Peppermill Carrier, a parallel isostatic Schönflies-motion generator designed for pick-and-place operations. The Cartesian spring and the finite element method are used to build the elastodynamics model of the robot. The stiffness and mass matrices are introduced to obtain the natural frequencies of the robot along a test trajectory — the Adept test cycle — that serves to evaluate the performance of the robot with respect to the operation speed.