Natural redundancy resolution in dual-arm manipulation using configuration dependent stiffness (CDS) control

Abstract

Incorporation of human motor control principles in the motion control architectures for humanoid robots or assistive and prosthesis devices will permit these systems not only to look anthropomorphic and natural at the body ware level but also to generate natural motion profiles resembling those executed by humans during manipulation and locomotion. In this work, relying on the observations on human bimanual coordination, a novel realtime motion control strategy is proposed to regulate the desired Cartesian stiffness profile during the execution of bimanual tasks. The novelty of the proposed control scheme relies on the use of common mode stiffness (CMS) and configuration dependent stiffness (CDS) to regulate the size and directionality of the task space stiffness ellipsoid. Thanks to the CDS control, the proposed scheme is not only proved to be effective in regulating the desired stiffness ellipsoid but also permits to resolve the manipulator redundancy in a natural manner. The effectiveness of the controller is evaluated in an experimental setup in which two cooperating robotic arms are executing an assembly task. Experimental results demonstrate that the proposed dual-arm CDS-CMS controller is effective in tracking the desired stiffness ellipsoids as well as in producing human-like natural motions for the two robotic arms.

Effective Capture of Nongraspable Objects for Space Robots Using Geometric Cage Pairs

“…Generally, dual-arm motion strategies can be classified as symmetric or asymmetric [36]. For the symmetric motion, both arms play the same role; the asymmetric motion is a more general manner, in which each arm performs a different role, such as in assembly or machining tasks [37]. In outer space, considering the particularity of caging non-graspable objects, we choose the symmetric capture motion based on two reasons.…”

A Lyapunov-Based Approach to Exploit Asymmetries in Robotic Dual-Arm Task Resolution

“…Relative tasks can be described solely through a relative motion of the robot's end-effectors. These include challenges such as the assembly of two components [1]- [3], drawing [4], [5] or machining [6]- [8]. Absolute tasks, conversely, consist in problems that can be solved by assuming a rigid connection between the robot end-effectors.…”

“…Alternatively to a master-slave approach, the Cooperative Task Space (CTS) [15] formulation specifically defines an absolute and a relative motion space along which the two 1 Division of Robotics, Perception and Learning, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden diogoa@kth.se 2 Dept. of Electrical Eng., Chalmers University of Technology, SE-412 96 Gothenburg, Sweden yiannis@chalmers.se Fig.…”

On the role of robot configuration in Cartesian stiffness control

“…Relying on the above observations, the Common-Mode Stiffness (CMS) and Configuration Dependent Stiffness (CDS) concepts were previously introduced to describe the effect on end-point stiffness of uniformly stiffening all joints and of changing the redundancy resolution configuration, respectively [7], [8]. In these schemes, the CMS control implements a coordinated stiffening profile in robot joints and contributes to modification in size of the stiffness ellipsoid, with no or small effect on its shape.…”

“…due to underactuation [7], [8], or to the use of decoupled joint stiffness control when using passive stiffness via Variable Stiffness Actuators (VSA) at the joints [9]. On the other hand, in a torque controlled robot (in which no such constraints are present), it is known [10] that in principle, any arbitrary endpoint stiffness matrix can be realized in any arbitrary configuration.…”