Sungbok Kim

Kinematic analysis of generalized parallel manipulator systems

This paper investigates the kinematic features of a general form of parallel manipulator systems, in terms of deficiency, singularity and redundancy, and its kinematic performance in terms of dexterity or load capacity. First, the task space is decomposed into three orthogonal instantaneous motion spaces (IMSs) of a parallel manipulator: deficient, uncontrollable, and controllable IMSs. Based on the IMSs, the deficiency and singularity of a parallel manipulator are described and explored to devise their remedies. Three types of redundancies of a parallel manipulator are then introduced by increasing actuators and limbs in three different ways. Next, the manipulabilities of a parallel manipulator are defined under the hypothetical actuation of joints, such as actuation, unactuation and freezing. Based on the characterization of the manipulabilities, the IMSs are identified to derive the formulas for the deficiency and singularity. The derived formulas serve as an effective tool for analyzing the kinematic features and kinematic performance of a parallel manipulator. The three types of redundancies are shown to improve either dexterity or load capacity of a parallel manipulator, as well as to prevent its singularity.<<ETX>>

Kinematic feature analysis of parallel manipulator systems

This paper presents an in-depth analysis on the kinematic features of parallel manipulators, such as deficiency, singularity, and redundancy. Parallel manipulators under consideration are of a general form, with no restriction on their structure. Three orthogonal instantaneous motion spaces (IMSs) of a parallel manipulator are identified, including deficient, uncontrollable, and controllable IMSs. Based on the IMSs, the deficiency and singularity of a parallel manipulator are described and analyzed, and their remedies are devised. Three types of redundancies of a parallel manipulator are introduced, including the redundancies in serial chain, joint actuation, and parallelism. The three types of redundancies are shown to overcome the singularity of a parallel manipulator, as well as to improve either its dexterity or load capacity.<<ETX>>

Efficient inverse kinematics for serial connections of serial and parallel manipulators

This paper presents a unified and efficient method of solving the inverse kinematics for six degree-of-freedom serial connections of two three degree-of-freedom serial and parallel manipulators. Based on the kinematic analysis of three degree-of-freedom serial and parallel manipulators, the forward kinematics are formulated for six degree-of-freedom serial connections, including parallel-parallel, serial-parallel, parallel-serial, and serial-serial types. A unified method of solving the inverse kinematics for the serial connections is established: for a given task velocity, the inverse kinematics of two arms are obtained separately, thereby significantly reducing a computational cost. This is made possible by projecting a given velocity onto the infeasible velocity space of one arm independently. Through computational analysis, the proposed method is shown to be effective for the serial connections having at least one parallel manipulator.

Manipulabilities Of Serial-parallel Manipulator Systems

This paper presents two different ap- proaches of deflning the manipulabilities and resistivi- ties of serial-parallel manipulator systems. In the flrst approach, the manipulability (resistivity) of the serial- parallel structure is dehed by imposing the kinematic constraint on the local manipulabilities (local resistiv- ities), each of which is obtained from the unit sphere in the joint velocity Ljoint torque) space of an individ- ual arm. In the second approach, the manipulability (resistivity) of the serial-parallel structure is defined by imposing the kinematic constraint directly on the unit sphere in the extended joint space formed by all the arms. The two approaches are shown to be com- plementary to each other: the fist approach is useful for the geometrical analysis of the interactions among local arms, while the latter is useful for the quanti- tative analysis of the performance of a serial-parallel structure as a whole.

Dynamic coordination of a self-reconfigurable manipulator system

The authors present the dynamic coordination of a self-reconfigurable manipulator system capable of changing its mechanical structure according to given task requirements. The self-reconfiguration is achieved by reconfiguring the topology of a dual-arm system through serial, parallel, and bracing structures. Particular emphasis is placed on the dynamic coordination of two arms having three different dual-arm topologies. The authors develop the Cartesian space dynamic models of a dual-arm system of three dual-arm topologies and derive the kinematic and dynamic constraints imposed on two arms in cooperation. Dual-arm dynamic manipulabilities are defined to quantify the dynamic performance of three dual-arm topologies in terms of the efficiency of generating Cartesian accelerations. A methodology of selecting serial, parallel, and bracing structures based on dual-arm dynamic manipulabilities is provided.<<ETX>>

Cartesian space dynamic model of serial-parallel manipulator systems and their dynamic performance evaluation

A Cartesian space forward and inverse dynamic model of serial-parallel manipulator systems is presented. The systems dynamic manipulability is defined as the capability of generating Cartesian accelerations within joint torque limits of individual arms. The dynamic performance of serial-parallel manipulator systems is then evaluated by analyzing the effects of object loading, parallel structure, bracing, and joint locking on the dynamic manipulability.<<ETX>>

A self-reconfigurable manipulator system with dextrous bracing structure

The authors present a dextrous bracing structure of a dual-arm system as a means of implementing a self-reconfigurable manipulator system. The dextrous bracing structure allows a dual-arm system to relocate the bracing point between two arms, select the type of contact as the bracing point, and lock or release the joints of individual arms. The self-reconfigurable dual-arm system is now capable of reconfiguring its topology through serial, parallel and bracing structures, supporting general types of contact, rigid or sliding, as well as locking or releasing some of its joints as needed. The focus is on an analysis of the effects of the dextrous bracing on the performance of a dual-arm system in terms of dual-arm manipulabilities and resistivities. The analysis shows that a self-reconfigurable dual-arm system with a dextrous bracing structure gives continuously varying performance characteristics ranging from serial to parallel structures.<<ETX>>

Dual redundant arm system operational quality measures and their applications: dynamic measures

The authors present dual-arm system static operational quality measures which quantify the efficiency and capability of a dual-arm system in generating Cartesian velocities and static forces. First, they define and analyze the kinematic interactions between the two arms incurred by the various modes of dual-arm cooperation, such as transport, assembly, and grasping modes of cooperation, and specify the kinematic constraints imposed on individual arms in Cartesian space due to the kinematic interactions. Dual-arm static manipulability is presented. Finally, dual-arm operational quality is scaled by a task-oriented operational quality measure (TOQ/sub s/) obtained by the comparison between the desired and actual static manipulabilities. TOQ/sub s/ is used in the optimization of dual-arm joint configurations. Simulation results are shown.<<ETX>>

Self-Reconfiguration of a Dual Redundant ARM System

Abstract This paper presents the self-reconfiguration of a dual redundant arm system, which can dynamically adapt itself to given task requirements. The self-reconfiguration proposed in this paper is performed by reconfiguring the structure of a dual redundant arm system through serial, parallel and bracing structure, along with locking or releasing some of its joints as needed. This paper in particular investigates the dextrous bracing of a dual-arm system as a general form of dual-arm topologies for the self-reconfiguration. First, we derive the kinematic constraints of a dual-arm system having bracing structure in terms of Cartesian motions and static forces of individual arms. Dual-arm manipulabilities and resistivities are then defined to represent the performance characteristics of the dual-arm bracing structure. The dual-arm self-reconfiguration is achieved by selecting an optimal bracing point, based on the task distribution among local arms according to their efficiency and capability in task execution.