Taking inspiration from the principle of locality in the field theories of physics [1], we aim to generate an impedance-related velocity field on SE(3) that characterizes the local interaction behaviors associated with specific tasks. Thanks to its locality, the desired impedance at each point of SE(3) can be effectively rendered by following the velocity field, without invoking the geometrical inconsistency of active stiffness [3].First, we will introduce a nonlinear impedance equipped with a guided wrench and a velocity output to portray the global interaction behaviors. The guided wrench will be conceived to ensure that the velocity output at each point of SE(3) accurately reflect the local interaction behaviors. Next, we will employ model-matching approaches to regulate the robot’s end-effector based on the velocity output. Finally, we will conduct a case study on the Peg-in-Hole (PiH) task to demonstrate this impedance control technique.

Since the shape of industrial endoscopes is passively altered according to the contact around it, manual inspection approaches of aeroengines through the inspection ports have unreachable areas, and it’s difficult to traverse multistage blades and inspect them simultaneously, which requires engine disassembly or the cooperation of multiple operators, resulting in efficiency decline and increased costs. To this end, this paper proposes a novel continuum manipulator with push-pull multisection structure which provides a potential solution for the disadvantages mentioned above due to its higher flexibility, passability, and controllability in confined spaces. The ultra-slender design combined with a tendon-driven mechanism makes the manipulator acquire enough workspace and more flexible postures while maintaining a light weight. Considering the coupling between the tendons in multisection, a innovative kinematics decoupling control method is implemented, which can realize real-time control in the case of limited computational resources. A prototype is built to validate the capabilities of mechatronic design and the performance of the control algorithm. The experimental results demonstrate the advantages of our continuum manipulator in the in-situ inspection of aeroengines’ multistage blades, which has the potential to be a replacement solution for industrial endoscopes.

Interaction with the environment is arguably one of the necessary actions for many robot applications such as haptic devices, manipulation, parts assembly, cooperation with humans, and the use of tools. Taxonomy of interaction behaviours is classified into three categories: cooperation, collaboration, and competition. In theory, interaction dynamics may be modelled by D'Alembert's principle or nonsmooth mechanics through seeking equality and/or inequality kinematic constraints. However, it is hard to gain these kinematic constraints in practice since they may be variable or be hardly described in a mathematical form. As a result, bond graph methodology is preferred in interaction dynamics modelling.In this paper, passivity and passivity indices with the differential operator are put forward by restricting its domain from the whole extended Hilbert function space to a set of all continuous function with finite derivative, and then the input-output stability condition, in this case, is derived. Next, mechanical impedance and admittance are defined, and a linear spatial impedance representation is given from the energetic point of view. Base on the bond graph theory, an ideal model is presented to model the idealized interaction, and invariance of port functions derived from the ideal interaction model is introduced; An interaction model is then proposed accounting for nonidealized factors and to describe cooperative, collaborative, and competitive interactions in a unified way. Finally, interaction stabilities are analyzed corresponding to different interaction models, and robustness of interaction stability is addressed based on the passivity indices.

In this paper, contact dynamics of robot massage is described by the port-Hamiltonian modelling approach. In order to capture accurately the inherent characteristics of the human body in lumped-parameter manners, the conventional linear Kelvin-Voigt models are replaced by the nonlinear Hunt-Crossley models. As an application of the contact dynamics, coupled stability of compliant robotic arm with impedance control is theoretically analyzed from energetic viewpoints. Experiments are done to verify the massage stability. The proposed contact dynamics evidently has great potential on performance improvement of robot massage, which will be our research subject.

For reproducing the manipulation of TCM remedial massage and meanwhile guaranteeing safety, a 4-DOF anthropomorphic BIT soft arm with integrated elastic joints is developed, and a passivity-based impedance control is used. Due to their series elasticity, the integrated joints may minimize large forces which occur during accidental impacts and, further, may offer more accurate and stable force control and a capacity for energy storage. Then, human expert's fingertip force curve in the process of massage therapy is acquired in vivo by a dedicated measurement device. Three massage techniques, pressing, kneading and plucking, are implemented by the soft arm, respectively, on torso model in vitro and on human body in vivo. Experimental results show that the developed robotic arm can effectively imitates the TCM remedial massage techniques.

By redefining multiplier associated with inequality constraint as a positive definite function of the originally-defined multiplier, u2j,i = 1,2, ----, m, say, the nonnegative constraints imposed on inequality constraints in Karush-Kuhn-Tucker necessary conditions are removed completely. Hence it is no longer necessary to convert inequality constraints into equality constraints by slack variables in order to reuse those results concerned only with equality constraints. Utilizing this technique, improved Lagrange nonlinear programming neural networks are devised, which handle inequality constraints directly without adding slack variables. Then the local stability of the proposed Lagrange neural networks is analyzed rigourously with Liapunov's first approximation principle, and its convergence is discussed deeply with LaSalle's invariance principle. Finally, an illustrative example shows that the proposed neural networks can effectively solve the nonlinear programming problems.