It is shown that the required motion and force trajectories of a given task can be abstracted by a series of desired manipulability ellipsoids and that task-oriented dual-arm manipulability (TODAMM) can be mathematically defined by quantifying how the manipulability of one arm affects the other and measuring the geometrical closeness between the desired and the actual manipulability ellipsoids. TODAMM can be used in the optimization of dual-arm joint configurations. The task-oriented manipulability measure (TOMM) developed can also be used in the joint configuration optimization of a single arm, providing efficient joint configurations in terms of joint motions and joint torques for the required Cartesian motions and static forces. The dual-arm joint configuration optimization based on TODAMM can be applied to a variety of asks which require dual-arm cooperation. >

Dual redundant arm configuration optimization with task-oriented dual arm manipulability

The motion and internal loads induced on an object manipulated by two or more robotic mechanisms are con sidered. In particular, for a desired motion trajectory of the object, the question of load distribution among the arms is analyzed, with particular attention given to the internal loading of the object. A new representation of the load distribution problem is given by the introduction of a particular "nonsqueezing" pseudoinverse, which is shown to possess properties that expose the underlying structure of the problem. It is expected that by using this pseudoin verse new insight will be gained and necessary analysis simplified in a number of aspects of multiple manipulator research. A number of these aspects are detailed and illustrated using a two-armed example.

Analysis of motion and internal loading of objects grasped by multiple cooperating manipulators

A new control method is presented for the coordinated control of two robot arms based on exact system linearization by appropriate non-linear feedback. The two arms are assumed to be working on the same object simultaneously. The control method uses a dynamic coordinator acting on relative position and velocity error and/or on relative force-torque errors between the two arms. Simulation results are presented for the coordinated control of two PUMA 560 robot arms using an optimal dynamic coordinator. For completeness, the paper also presents (i) a new revised set of inertia parameters for all six links of PUMA 560 robot arm, (ii) the form of nonlinear feedback and diffeomorphic state transformation which linearizes the control of PUMA 560 working in all six degrees of freedom, and (iii) the reduced numeric form of all dynamic equations for PUMA 560 working in three (positioning) degrees of freedom.

Coordinated control of two robot arms

Multiple coordinated robot arms are modeled by considering the arms as closed kinematic chains and as a force-constrained mechanical system working on the same object simultaneously. In both formulations, a novel dynamic control method is discussed. It is based on feedback linearization and simultaneous output decoupling technique. By applying a nonlinear feedback and a nonlinear coordinate transformation, the complicated model of the multiple robot arms in either formulation is converted into a linear and output decoupled system. The linear system control theory and optimal control theory are used to design robust controllers in the task space. The first formulation has the advantage of automatically handling the coordination and load distribution among the robot arms. In the second formulation, it was found that by choosing a general output equation it became possible simultaneously to superimpose the position and velocity error feedback with the force-torque error feedback in the task space. >

New nonlinear control algorithms for multiple robot arms

An an application of robotics in physical rehabilitation therapy, a robotic system consisting of two planar robot arms, each with two degrees of freedom, is considered. This robotic system, when coupled across a human joint, provides a vehicle for rehabilitation of the joint following surgery or trauma. A novel approach for estimation of body segment parameters is formulated that uses state and output information from the robot system to improve these estimates. In addition, redundant sensors are used to improve the accuracy of the estimates. The dynamic equations for a single robot arm are provided and the system is simulated. Therapeutic applications of the robotic system are discussed and the sensitivity of the measured forces with respect to the robot arm joint angles is studied in order to find an optimum orientation of the system for the best possible estimation. The application of this system to both rehabilitation and sports medicine is also discussed. >

An intelligent robotic system for rehabilitation of joints and estimation of body segment parameters

This paper presents a new control method for coordinated control of two robot arms. The two arms are assumed to work on the same object simultaneously. The control method uses a dynamic coordinator acting on relative position and velocity task space errors and on relative force-torque errors between the two arms as sensed at the end effectors. This method is novel because we could superimpose the position and velocity error feedback with the force-torque error feedback in the task space simultaneously.

Dynamic coordination of two robot arms

It is shown that nonlinear feedback with diffeomorphic state transformation is applicable to dynamic control of PUMA 560 robot arm. This new dynamic control method externally (or exactly) linearizes the whole system and provides simultaneous output decoupling. To render the control robust, the nonlinear feedback is augmented with optimal error correcting controller which operates on the error in the task space. A key feature of this dynamic control method is that the nonlinear gains in the controller do not need readjustment from task to task. In that sense this controller is "intelligent" since it directly responds to changing task commands. A complete dynamic model in state equation form and with the necessary geometric and inertial parameters is also presented for PUMA 560 restricted to motions at the first three joints. This model is necessary to specify the nonlinear feedback and diffeomorphic transformation.

X. Yun

Papers

Dynamic coordination of two robot arms

Nonlinear feedback control of PUMA 560 robot arm by computer

Robust Robot Arm Control with Nonlinear Feedback