Dynamics and Control of Whole Arm Grasps

In this paper we consider the dynamics and control of whole arm grasping systems. We develop a control scheme that employs a minimal set of inputs to control the trajectory of the system while using the surplus inputs to control the interaction forces in order to maintain the unilateral constraints at both rolling and sliding contacts. Since the number of surplus inputs is less than the number of output force variables, we propose a controller that controls the critical contact force components. We emphasize the dynamic models and algorithms for computing contact forces, which are crucial to the development of the control algorithms. Finally, we show how compliant contact models and a previously developed integrated simulation approach [14] are used to overcome the difficulties with uniqueness and existence of solutions. A planar whole arm manipulation system is used as an example to illustrate the basic ideas

Task Accuracy Measure based on Dynamic Process for Cooperating Manipulation System

Abstract-The present paper introduces an evaluation of the manipulation performance of a cooperating robotic manipulator with respect to task accuracy, taking into consideration the effects of the dynamic process between inputs and outputs in the manipulation system. A measure based on the output controllability of the manipulation system is proposed, which shows the relationship between the object's position and orientation and the joint driving force. Computer simulations show the validity of the task accuracy measure and the difference between the proposed measure and the conventional manipulability measure

Randomized Planning and Control Strategy for Whole-Arm Manipulation of a Slippery Polygonal Object

The present paper introduces a planning and control strategy for whole-arm manipulation of a slippery polygonal object. Randomized planning methods are first proposed in order to generate contact state transitions, which help not only to reduce the amount of calculation required, but also to handle a hybrid system composed of a continuous system and a discrete system, which has a large search space and complicated constraints. Second, a novel control strategy, which can switch manipulation modes among quasi-static, dynamic, and caging manipulation depending on the situation, is proposed. This strategy not only can cope with changes in the mechanics of the system caused by contact state transitions, but also can increase the manipulation feasibility and reliability. The validity of the proposed methods is verified through simulations and experiments

Control for throwing manipulation by one joint robot

Abstract-This paper proposes a throwing manipulation strategy for a robot with one revolute joint. The throwing manipulation enables the robot not only to manipulate the object to outside of the movable range of the robot, but also to control the position of the object arbitrarily in the vertical plane even though the robot has only one degree of freedom. In the throwing manipulation, the robot motion is dynamic and quick, and the contact state between the robot and the object changes. These make it difficult to obtain the exact model and solve its inverse problem. In addition, since the throwing manipulation requires more powerful actuators than the static manipulation, we should set the control input by taking consideration of the performance limits of the actuators. The present paper proposes the control strategy based on the iteration optimization learning to overcome the above problems and verifies its effectiveness experimentally

Strain-induced creation and switching of anion vacancy layers in perovskite oxynitrides

Using strain to control oxynitride properties. 京都大学プレスリリース. 2020-12-01.原子空孔の配列を制御する新手法の発見. 京都大学プレスリリース. 2020-12-02.Perovskite oxides can host various anion-vacancy orders, which greatly change their properties, but the order pattern is still difficult to manipulate. Separately, lattice strain between thin film oxides and a substrate induces improved functions and novel states of matter, while little attention has been paid to changes in chemical composition. Here we combine these two aspects to achieve strain-induced creation and switching of anion-vacancy patterns in perovskite films. Epitaxial SrVO3 films are topochemically converted to anion-deficient oxynitrides by ammonia treatment, where the direction or periodicity of defect planes is altered depending on the substrate employed, unlike the known change in crystal orientation. First-principles calculations verified its biaxial strain effect. Like oxide heterostructures, the oxynitride has a superlattice of insulating and metallic blocks. Given the abundance of perovskite families, this study provides new opportunities to design superlattices by chemically modifying simple perovskite oxides with tunable anion-vacancy patterns through epitaxial lattice strain

Complementarity Formulation for Multi-Fingered Hand Manipulation with Rolling and Sliding Contacts

We propose a novel complementarity model for a general three-dimensional manipulation system with rolling and sliding contacts to solve the forward dynamics problem. The key idea is to derive complementary constraints for a rolling contact by decomposing the tangential properties. We also discuss the existence and uniqueness of a solution to the model, and algorithms for solving the problem. We show examples of computer simulation for dynamics of multifingered hand manipulation and discuss how the transition of contact modes varies for applied joint driving torques

Robust hitting with dynamics shaping

Abstract—The present paper proposes the motion planning based on “the dynamics shaping ” for a robotic arm to hit the target robustly toward the desired direction, of which the concept is to shape the robot dynamics appropriately in order to accomplish the desired motion. According to the linear system theory, the positional error of the end-point converges onto near the singular vector corresponding to its maximum singular value of the output controllability matrix of the robotic arm. Therefore, if we can control the direction of the singular vector by applying the dynamics shaping, we will be able to control the direction of the positional error of the end-effector caused by the disturbance. We propose a novel motion planning based on the dynamics shaping and verify numerically and experimentally that the robotic arm can robustly hit the target toward the desired direction with a simple open-loop control system even though the disturbance is applied. I