Abstract
Bimanual robots have been studied for decades and regulation on internal force of the being held object by two manipulators becomes a research interest in recent years. In this paper, based on impedance model, a method to obtain the optimal target position for bimanual robots to hold an object is proposed. We introduce a cost function combining the errors of the force and the position and manage to minimize its value to gain the optimal coordinates for the robot end effectors (EE). To implement this method, two necessary algorithms are presented, which are the closed-loop inverse kinematics (CLIK) method to work out joint positions from desired EE pose and the generalized-momentum-based external force observer to measure the subjected force acting on the EE so as to properly compensate for the joint torques. To verify the effectiveness, practicality, and adaptivity of the proposed scheme, in the simulation, a bimanual robot system with three degrees of freedom (DOF) in every manipulator was constructed and employed to hold an object, where the results are satisfactory.
Highlights
Robots were invented mainly to help human being to carry out tasks, reducing the intensity of human labour, for example, grasping, holding, or moving an object
In [4], the object with dynamics parameters and deformable shape is considered and the grasping forces can be regulated based on a similar tactile framework. e application scenarios of these motions vary from daily life
Methods to obtain the optimal solution to such kind of cost function in impedance model-based linear/ nonlinear system can be found in the literature; for example, [26] seeks help from iterative adaptive dynamic programming algorithm, and [27, 28] solve it by constructing the Hamilton-Jacobi-Bellman equation (HJB) while a neural network-based computational method is provided in [29] to handle the algebraic Riccati equation (ARE) that usually accompanies the HJB. e techniques in [29] make the solution to the HJB accessible, which is confirmed by researchers who apply the method into robot-environment interaction [30]
Summary
Robots were invented mainly to help human being to carry out tasks, reducing the intensity of human labour, for example, grasping, holding, or moving an object. Based on relative impedance models, in bimanual robots teleoperation system, [19] improves the internal force control performance by deducing the desired position; [20] implements the proposed method on the two manipulator systems to carry out hold-and-move task in the teleoperation field and the authors separately handle the orientation, position, and force regulation problem. E techniques in [29] make the solution to the HJB accessible, which is confirmed by researchers who apply the method into robot-environment interaction [30] Inspired by these papers, in this paper, we construct a suitable performance measure to fit the bimanual robots’ collaboration situation in order to gain an optimal regulation for force and position. E structure of the paper is organized as follow: Section 2 (Methods) develops the proposed method, including the restatement on the purpose of this paper, some preliminary knowledge, and the introduction of the force observer and the CLIK; right after Methods comes Section 3 (Simulations and Analysis) that involves the simulation configuration, procedures, results, and analysis; the final section (Conclusions) summarizes the whole paper
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