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In this article, we introduce the notion of bounded energy collision for physical human–robot collaboration to allow safe interaction with the environment, by keeping the collision impact within predetermined bounds. The proposed method is based on energy dissipation, implemented by a variable damping strategy along the direction of imminent collisions with the environment, and fully complies with any physical human–robot interaction strategy that combines an indirect force control (e.g., impedance control) with an estimation of the human motion intention. Finally, extensive experimental studies clarify and verify the proposed scheme.

In this paper, we present a distributed hybrid control strategy for multiagent systems with contingent temporal tasks and prescribed formation constraints. Each agent is assigned a local task given as a linear temporal logic formula. In addition, two commonly seen kinds of cooperative robotic tasks, namely, service and formation, are requested and exchanged among the agents in real time. The service request is a short-term task provided by one agent to another. On the other hand, the formation request is a relative deployment requirement with predefined transient response imposed by an associated performance function. The proposed hybrid control strategy consists of four major components: 1) the contingent requests handling module; 2) the real-time events monitoring module; 3) the local discrete plan synthesis module; and 4) the continuous control switching module, and it is shown that all local tasks and contingent service/formation requests are fulfilled. Finally, a simulated paradigm demonstrates the proposed control strategy.

In various interaction tasks using Underwater Vehicle Manipulator Systems (UVMSs) (e.g. sampling of the sea organisms, underwater welding), important factors such as: i) uncertainties and complexity of UVMS dynamic model ii) external disturbances (e.g. sea currents and waves) iii) imperfection and noises of measuring sensors iv) steady state performance as well as v) inferior overshoot of interaction force error, should be addressed during the force control design. Motivated by the above factors, this paper presents a model-free control protocol for force controlling of an Underwater Vehicle Manipulator System which is in contact with an unknown compliant environment, without incorporating any knowledge of the UVMS’s dynamic model, exogenous disturbances and sensor’s noise model. Moreover, the transient and steady state response as well as reduction of overshooting force error are solely determined by certain designer-specified performance functions and are fully decoupled by the UVMS’s dynamic model, the control gain selection, as well as the initial conditions. Finally, a simulation study clarifies the proposed method and verifies its efficiency.

Multi-robot motion planning from local connectivity specifications in unknown workspaces necessitates for reconfigurability, since real-time obstacle detection is likely to raise contradictions between collision avoidance and local connectivity specifications. Thus, a key issue in control synthesis is to allow topological changes in the communication graph in case of infeasibility, while maintaining the global connectivity of the robotic network and guaranteeing collision-free motion. Towards this direction, we propose: i) a distributed algorithm that coordinates robots, whenever feasible, based on local connectivity as well as collision avoidance specifications and ii) a novel decentralized algorithm that dynamically reconfigures the communication topology in case of conflicts with the collision avoidance specifications, without compromising the global connectivity of the communication graph. In the continuous control system, provably correct collision avoidance and robust synchronized motion are secured, employing the prescribed performance control methodology that ensures predefined transient and steady state response. Finally, simulated examples clarify the proposed methodology and verify its efficiency.

In this paper, novel event-triggered strategies for the design of model predictive (MPC) controllers are presented. The MPC framework consists in finding the solution to a constraint optimal-control problem at every time-step. The case of triggering the optimization of the MPC only when is needed, is investigated. The centralized case is treated first and the results are then extended to a decentralized formulation. We consider a system composed by a number of interconnected subsystems, each one of them controlled by a robust MPC algorithm. Using the Input-to-State (ISS) property of the decentralized MPC controller we reach to an event-triggering rule, for each of the subsystems.

In this paper we use the centralized multirobot navigation function methodology established by the authors, augmented with an enhanced dipolar navigation field suitable for non-holonomic vehicls. A properly designed discontinuous feedback control law is applied to steer the nonholonomic vehicles. The esulting high frequency switching behavior, known as chattering, which is inherent in discontinuous controllers, is tackled with an appropriately designed discontinuous backstepping controller, which effectively reduces chattering. The vehicles are assumed to have limitations on their maximum achievable velocities. Those issues are taken into account in the control law design. The resulting closed form control scheme provides robust navigation withguaranteed collision avoidance and global convergence properties, as well as fast feedback, rendering the methodology particularly suitable for real time implementation, on systems with limited actuation capabilities. Collision avoidance and global convergence properties are verified through non - trivial computer simulations.

A wheeled mobile manipulator system is modeled using Kane's dynamic equations. Kane's equations are constructed with minimum effort, are control oriented and provide both physical insight and fast simulations. The powerful tools of Kane's approach for incorporating nonholonomic motion constraints and bringing noncontributing forces into evidence are exploited. Both nonholonomic constraints associated with slipping and skidding as well as conditions for avoiding tipping over are included. The resulting equations, along with the set of constraint equations provide a safe and complete framework for developing control strategies for mobile manipulator systems.

We present the design of a pre-shaping module that feeds an industrial robot controller with a pseudo-reference trajectory and guarantees that the controller output acts as a required nonlinear control scheme. This is to enable the rapid testing and prototyping of control schemes on real robots without having to intervene with the hardware and low level software of their industrial controllers.

In this work we construct a general dynamic model for a system with multiple mobile manipulators which carry a deformable object, It incorporates all dynamics and significant mechanical constraints. In the model we consider the mobile platforms and the onboard manipulators as a single system, we take into account the nonholonomic constraints imposed on the platforms and provide necessary conditions for stability of the mechanism against tipping over. Finally, the properties of the set of admissible reaction forces, defined by the constraint equations, are discussed.

Robots are rapidly becoming part of our lives, coexisting, interacting, and collaborating with humans in dynamic and unstructured environments. Mapping of human to robot motion has become increasingly important, as human demonstrations are employed in order to “teach” robots how to execute tasks both efficiently and anthropomorphically. Previous mapping approaches utilized complex analytical or numerical methods for the computation of the robot inverse kinematics (IK), without considering the humanlikeness of robot motion. The scope of this work is to synthesize humanlike robot trajectories for robot arm-hand systems with arbitrary kinematics, formulating a constrained optimization scheme with minimal design complexity and specifications (only the robot forward kinematics (FK) are used). In so doing, we capture the actual human arm-hand kinematics, and we employ specific metrics of anthropomorphism, deriving humanlike poses and trajectories for various arm-hand systems (e.g., even for redundant or hyper-redundant robot arms and multifingered robot hands). The proposed mapping scheme exhibits the following characteristics: (1) it achieves an efficient execution of specific human-imposed goals in task-space, and (2) it optimizes anthropomorphism of robot poses, minimizing the structural dissimilarity/distance between the human and the robot arm-hand systems.