Input shaping techniques for vibration control of flexible structures received many interest due to its simplicity and efficiency proven in various practical cases. This paper proposes an adaptation of those techniques by addressing two main specificities of robot manipulators. As a first contribution, the design of input shapers for multiple-input and multiple-modes complex robot is studied. Design indicators based on elastic-dynamic model are proposed in order to choose one input shaper design among thousands of possible combinations. As a second contribution, the vibration mode frequency evolution of robot manipulators over their workspace is compensated by an adaptive control scheme. It is proposed to interpolate the modal variations over the workspace and tune the input shaper parameters dynamically. This contribution is implemented on a large scale flexible robot and shows promising results.

In this paper, we propose a physically meaningful energy-related safety indicator for robots sharing their workspace with humans. Based on this indicator, a safety criterion accounting for the breaking capabilities of the robot is included as a quadratic constraint in the control algorithm. This constraint is modulated by the distance between the human operator and the end-effector of the robot. The control algorithm is formulated as an optimization problem and computes the actuation torque of a robotic manipulator given some task to be performed and physical constraints to respect. The overall framework is validated in a physics simulation software on a Kuka LWR4 and different behaviours of the robot towards a considered obstacle in its environment are evaluated and discussed.

A novel formulation of the synthesis of motor coordination for humanoid whole-body motion is proposed in this paper, in order to ensure robust control of postural stability. It relies on the distributed model predictive control framework to coordinate, in an optimal way, several objectives. The effectiveness of this control technique to maintain postural stability of a biped against strong external disturbances is shown. Control of the horizontal dynamics of the center of mass can withstand limited perturbations. Thus postural stability criteria are specified with respect to the robot center of mass vertical and horizontal dynamics, and to the angular dynamics of its torso. Formulating the balance problem in a predictive form and distributing at different time scales significantly increases the robustness of the system to external disturbances, in terms of both tip-over and slippage risks. This original control architecture is validated through the simulation of an iCub robot performing a walking activity under unknown external actions.

Balance strategies range from continuous postural adjustments to discrete changes in contacts: their simultaneous execution is required to maintain postural stability while considering the engaged walking activity. In order to compute optimal time, duration and position of footsteps along with the center of mass trajectory of a humanoid, a novel mixed-integer model of the system is presented. The introduction of this model in a predictive control problem brings the definition of a Mixed-Integer Quadratic Program, subject to linear constraints. Simulation results demonstrate the simultaneous adaptation of the gait pattern and posture of the humanoid, in a walking activity under large disturbances, to efficiently compromise between task performance and balance. In addition, a push recovery scenario displays how, using a single balance-performance ratio, distinct behaviors of the humanoid can be specified.

Assistance to walking is a key point in improving autonomy during daily living activities of elderly and disabled people. Despite the significant number of active robotized walkers and canes proposed in the literature, only few studies focused on the mechanical influence of assistive devices on the gait generation process. A deeper analysis of assisted walking dynamics is very likely to help improving the design and the adequacy of the robotized assistants. In this paper a simulation framework of impaired and cane assisted gaits is developed. Simulations of common passive cane assistance allow a deeper analysis of its contributions to the locomotion. The behaviour of an active cane and its beneficial impact on the energetics of impaired gaits are exposed.

In this paper, we propose a novel idea to address the problem of fast computation of enveloping grasp configurations for a multi-fingered hand with 3D polygonal models represented as polygon soups. The proposed method performs a low-level shape matching by wrapping multiple cords around an object in order to quickly isolate promising grasping spots. From these spots, hand palm posture can be computed followed by a standard close-until-contact procedure to find the contact points. Along with the contacts information, the finger kinematics is then used to filter the unstable grasps. Through multiple simulated examples with a twelve degrees-of-freedom anthropomorphic hand, we demonstrate that our method can compute good grasps for objects with complex geometries in a short amount of time. Best of all, this is achieved without complex model preprocessing like segmentation by parts and medial axis extraction.

This paper presents an environment for design of interactive behaviors for social robots. Its structure consists of three levels which are: perception, decision and action. Their principles are briefly described and we detail more specifically implementation of people searching and monitoring in cluttered environments. We describe in particular the methods for people detection, state estimation and trajectory generation for interactive monitoring. We demonstrate experimentally that the designed reasoning system is able to regulate the robot behavior in complex situations. The robustness of the framework is evaluated experimentally for person following in his home space that may lead the system to lose the person detection because of occlusions and to use shortcuts.

This paper proposes a robust whole-body control formulation for biped balance in disturbed conditions by manipulation tasks. In order to include the effects of the interaction of the robot with its environment, required by the manipulation task in the balance control, we introduce a distributed preview control which captures both balance and manipulation behaviors and enables the regulation of the interaction impedance. The initial ZMP preview control is extended to take into account the disturbance resulting from the manipulation task and the preview control of adaptive impedances used to drive the upper-limbs. The resulting behavior is illustrated in a simple scenario. Its aptitude to dynamically extract an optimal control strategy improving tracking performances of both manipulation and balance tasks is also assessed when complex perturbations have to be compensated.

We present a novel approach to deal with transitions while performing a sequence of dynamic tasks with a humanoid robot. The simultaneous achievement of several tasks cannot be ensured, so we use a strategy based on weights to represent their relative importance. The robot interacts with a changing environment, and the input torques are different depending on whether the robot performs tasks in a constrained state (e.g. in contact) or not. We develop a solution with smooth weights variations and transitional tasks which avoids sharp torque evolutions. In order to validate this approach, simulations are carried out on a virtual iCub robot which is assigned the realization of a complex mission involving various changing tasks.

This paper focuses on the problem of robust obstacles crossing for a high mobility wheel-legged robot. To improve the obstacle clearance capability, a method dealing with the contact stability optimization is developed. A specific stability criterion taking the friction into account is proposed. The optimization algorithm uses both the kinematic redundancy in order to modify the position of the Center of Mass (CoM), modifying the resulting distribution of contact forces, and the actuation redundancy to improve the stability of frictional contacts by adapting the internal forces. We show that the choice of this particular criterion allows us to maximize the robustness of contacts stability relatively to the modeling errors affecting force control (friction in mechanical transmission). Performances of this algorithm are evaluated in simulation and the necessity for a CoM trajectory planning is highlighted by an analysis of obstacle crossing using this criterion.

The paper provides a method to determine and compare the reconfigurability of lattice systems. First it shows the difference that exists between the reconfigurability and self-reconfigurability features of a lattice system. Then a method using displacement groups is introduced to characterize these features. Based on this method, these features are then compared for some existing lattice systems.

Most of the literature reactive control laws have much difficulties to handle properly constraints such as joint limits, obstacles and saturations, including them as equalities in the Inverse Velocity Kinematics (IVK) problem. Actually, it seems relevant to handle them through inequalities, as the constraints are more numerous than the number of DOFs. However, the intuitive constraints expression can lead to incompatibilities between constraints, which necessarily induces constraints violations. This paper brings two distinct contributions. First, the usual constraints inequalities are modified to make them compatible permanently. Second, an intuitive and efficient constraint compliant control law is proposed.

Human-robot interaction (HRI) takes place especially through interfaces. The design of such interfaces is a very delicate and crucial phase because it influences the robot accessibility and usability by the user. In this paper, we describe and analyze the results of 2 tests conducted so as to understand some of the optimal features that should characterize the robot voice and graphical-based user interfaces. Our test platform is an assistive robot developed for the elderly with mild cognitive impairments. Therefore, the user interfaces must be clear and simple. The ambiguities must be eliminated so as to facilitate the use of the robot and hence not to discourage the elderly population to use new technologies.

The paper develops a method for analyzing and improving by control obstacle clearance capacities of articulated multi-wheeled rovers. On uneven ground surface, load and traction force distributions through the wheel/ground contact system are highly coupled. They are both conditioned by the global equilibrium of the mechanical system and the contact stability constraints. The optimal traction force distribution problem is formulated here as a convex optimization problem using Linear Matrix Inequalities (LMIs). Velocity and force transmissions in articulated multi-wheeled mobile robots are introduced under a generic form decomposed in task, joint and contact levels. A tyre-model is used for the evaluation of the robustness of the solution with respect to slippage phenomena. Simulation results show that the traction distribution forces which is so determined lead to a significant increase in obstacle clearance capacities compared to an usual velocity control technique.

A robust dynamic feedback controller is designed and implemented, based on the dynamic model of the six-wheel skid-steering RobuROC6 robot, performing high speed turns. The control inputs are respectively the linear velocity and the yaw angle. The main object of this paper is to elaborate a sliding mode controller, proved to be robust enough to ignore the knowledge of the forces within the wheel-soil interaction, in the presence of sliding phenomena and ground level fluctuations. Finally, a 3D simulation is performed with an accurate physical engine to evaluate the efficiency of this designed control law.

We identify three fundamental properties of lattice robots such as (1) discreteness (2) translational symmetry and (3) composition, and explain the analogy of lattice robots kinematics and crystal symmetry described by space groups. Then we give the possible connectors symmetries and orientations compatible with space groups, and the possible sliding and hinge joints locations and orientations compatible with the displacements in such groups. We present a framework for the design of lattice robots by assembling compatible joints and connectors into a space group and give a 3D example.

This paper deals with design and implementation of a stabilization algorithm for a car like robot performing high speed turns. The control of such a kind of system is rather difficult because of the complexity of the physical wheel- soil interaction model. In this paper, it is planned to analyze the complex dynamic model of this process to elaborate a stabilization algorithm only based on the measurement of the system yaw rate. Finally, a 3D simulation is performed to evaluate the efficiency of this designed stabilization algorithm.

This paper concerns the control of an autonomous high mobility wheel-legged rover crossing uneven terrains. A new control strategy, using active redundancies of the robot, leads to elaborate a posture control based on the potential field approach of the stability measurement. Then a decoupled posture and trajectory control algorithm based on the velocity model of the robot is proposed. Last, simulation results showing performance of the control algorithm are presented.

This paper presents a generic kinematic modeling approach for articulated multi-monocycle mobile robots. The formulation proposed to deduce the input/output velocity equations for such kinematic structures is an extension of the reciprocal screw based method of asymmetrical and constrained parallel mechanisms. The efficiency of this methodology for setting up the differential kinematic model is illustrated through application: the RobuRoc mobile robot. Its complex kinematic structure is first transformed into a spatial parallel mechanism which encapsulates the differential driving wheels system. Then, the analytical form of the reciprocal screw system which corresponds to the actively controlled wrenches applied on the controlled body is established. Reciprocally, it describes the way the wheel velocities are transferred to the output body. It also provides a geometrical information for an exhaustive singularity analysis and traction distribution optimization during the evolution of the system on highly irregular surfaces. From the differential kinematic model, the concept of traction ellipsoid is introduced for evaluating quantitatively the obstacle clearance capabilities when the configuration of the system and the contact conditions are highly variable

This work presents some general considerations on self-reconfigurable robots design, and proposes an original design of mechatronic modules. Geometrical and kinematical features of these modules, offer the ability to be used as well as wheels to produce rolling motion, and as joints for building kinematic chains as legs, arms or snakes.

This paper addresses the control of a hybrid wheel-legged system evolving on rough terrain. First, the posture and trajectory parameters are introduced. Then, a decoupled posture and trajectory control algorithm based on the velocity model of the robot is proposed. Last, the performance and feasibility of the control algorithm are evaluated through simulations and experiments with the Hylos robot.

This paper introduces an original, dextrous, active and modular minimally invasive instrument dedicated to coronary artery bypass grafting surgery. Its design is obtained by a generic evolutionary optimization process using Pareto-based multi objective genetic algorithms and including highly realist simulations and experimental models of the surgical gesture. The optimal instrument has 5 intra-body DOFs, is actuated by brush-less micro motors and is position controlled. Its optimization, mechanical design and performances are discussed.

This paper presents an original use of evolutionary algorithms in order to approximate by a closed form the inverse kinematic model of analytical (non-analytical) and general manipulators. The objective is to provide a fast and general solution to the inverse kinematic problem when it is extensively evaluated in the design processes of manipulators. A mathematical function is evolved through genetic programming according to the known direct kinematic model to determine an analytical expression which approximates the joint variable solution for a given end-effector configuration. As an illustration of this evolutionary symbolic regression process, the inverse kinematic models of the PUMA and GMF Arc Mate are approximated before applying the algorithm to general 6R manipulators.

Compliant mechanisms are particularly well to applications with small range of motions such as in microsystems. This paper focuses on the design of compliant mechanisms based on a compliant beam network for mechanical transmission problems. The aim is to define an set of mechanical structures subject to technological constraints, by integrating fabrication process particularities which here lead to bending efforts and preload. Here a method is described to determine by an optimization process adapted structures to mechanical tasks such as rigidification tasks or motion transmission. Basic examples illustrate this method.

In this paper, we propose an original design for a manipulation system of rigid micro-objects by adhesion (50 /spl mu/m/spl sim/200 /spl mu/m) in open air. The design is based on a precise analysis of the mechanical conditions for manipulation by adhesion. Simulations using a dynamic model of a canonical manipulation (capture and release of micro-objects) have shown that it exists an "end-effector initial acceleration" windows for which manipulations are possible. The end-effector we have developed integrates a highly sensitive contact sensor and two piezo-accelerators (/spl sim/10/sup 6/ m.s/sup -2/). Successful manipulations by adhesion of silicon chips with a gold coated piezoresistive silicon cantilever have been carried out and are presented as conclusion of this paper.

We present a haptic interface dedicated to endoscopy training, where the endoscope is allowed to react to contact forces along six degrees of freedom. The model takes into account end point position and appropriate contact forces. The illusion of physical movement inside the environment is obtained by computing control inputs based on the impedance environment. The user can manipulate and react with the simulated virtual environment.

The paper proposes an original method for the design of complex mechatronic systems such as locomotion systems. A modular approach is used in the hardware and software design of these robotic systems. The objective of the design process is to find the optimal combination of hardware and software components to achieve a locomotion task in a complex environment. For this we use an evolutionary algorithm, integrating a dynamic simulation of the mobile robot in its environment. A hybrid encoding allows us to evolve the robot structure and its control system simultaneously. Specialized genetic operators have been designed to manipulate this encoding and to adapt their action to the evolving population. The robot performances are evaluated through a simulation in which all criteria are computed and exploited in real time. The process is illustrated through a set of design examples. An improvement of computing time using a hierarchical evaluation is analyzed.

Proposes a method for the design of complex mechatronic systems consisting more precisely of locomotion systems. This method is based on a modular approach to the system design. The objective in the design process is to find an optimal mechanical architecture and an associated control to achieve displacements over complex surfaces. For this, we use an evolutionary algorithm integrating a dynamic simulation of the robotic system in its environment. We use a hybrid encoding which allows for a simultaneous evolution of the mechanical structure and its control system. Specialized genetic operators have been designed to manipulate this encoding and to adapt their action to the evolving population. The robot performances are evaluated through a simulation in which all criteria can be computed and exploited in real time. Hierarchical evaluation is then suggested for the improvement of computing time and the process is illustrated through a set of design examples.

In aim to optimize the control for an off-road robot and specially a robot with a crawling motion mode named peristaltical motion, it is essential to understand robot-soil interaction. We present an efficient method for simulating this interaction. This method can simulate the dynamic behavior of a 6-wheeled/3-axles Marsokhod type robot on different kinds of soils. With this simulation, we have defined the necessary conditions for using the peristaltical motion on sand or loose soil.

This paper proposes a method for task based design of modular robotic systems using genetic algorithms (GA). We introduce a 3D kinematic description for modular serial manipulators and a two-level GA to optimize their topology from task specifications. Revolute and prismatic joints are considered and the number of DOF is let to the GA to determine (allowing redundant manipulators). The upper-level GA is dedicated to the topology evolution and uses the lower-level GA to search for inverse kinematics problem solutions. The topology is evolved for adaptation to a global task constituted by several required end effector configurations (subtasks). The implemented GA optimizes several performance criteria under constraints. To illustrate the method capacities, an example is presented for a redundant manipulator in a cluttered workspace.

This paper proposes the distributed impedance approach as a new formulation of multiple robot systems control. In this approach, each cooperating manipulator is provided with its own independent impedance controller. In addition, along selected degrees of freedom, force control is achieved through an external loop, in order to improve control of the object's internal loading. Extensive stability analysis is performed based on a realistic model that includes robots impedance and object dynamics. Experiments are performed using two cooperating industrial robots holding an object through point contacts. Force and position control actions are suitably dispatched to achieve both internal loading control and object position control. The performance of the system is demonstrated for transporting tasks.

This paper presents a shape memory alloy (SMA) actuator aimed to be integrated in the phalanx of a dexterous micro-gripper. Its original design mechanically decouples motion transmission from force transmission. After a brief discussion on the operating principles of the actuator, the kinematics of the mechanism and its general features are specified. A thermo-mechanical model of the SMA fibers dynamics is then derived from an experimental analysis. Based on this model, a rational design methodology is proposed for the actuator. The last part of the paper shows experimental results. A prototype has been developed using the proposed design methodology. The paper shows the open loop results of this device. Additionally, a position switching mode controller is designed to improve precision and robustness.

Proposes an adaptative multi-chromosome evolutionary algorithm (AMEA) to perform task based design of modular robotic systems. The kinematic design is optimized by the AMEA which uses both binary and real encoding (for kinematic and configuration parameters). In the problem considered for illustration, the robotic system consists in a mobile base and a manipulator arm which may be built with serially assembled link and joint modules. The manipulator has to reach a predefined set of goal frames in a 3D cluttered environment. Its design is evaluated with geometric and kinematic performance measures. Optimization results for a 3D task are given and compared with a simple genetic algorithm. They clearly show the superiority of the multi-chromosome representation and adaptive operators in term of computing time and criteria optimization performance.

We apply analytical methods of workspace determination of mechanical systems to Stewart platforms. Four main tools are needed. The modelling gives the relationships between the parameters of the system. Mathematical analysis leads to a universal (i.e. not personal) approach and results. Mathematical optimization is used for the analytical approach to function minimization. The computer algebra used is both theoretical and practicable, since the calculations involved are likely to be very complex.

Conventional force control of manipulators is drastically degraded in the presence of external dynamic disturbances. Such difficulties may occur during unexpected environment motions or sudden changes in the environment dynamics. The solution the authors have developed provides robustness with respect to these disturbances. It consists of encapsulating a dynamic impedance controller with a reactive external force loop. This paper focuses on the external loop, which takes into account both interaction forces and environment displacements to modify the reference trajectory of the inner impedance controller. It is also capable of rapid self tuning when the environment dynamics are changed. The reactive external loop is implemented using fuzzy logic techniques. Observation of the real behavior of the experimental system is used to design some simple fuzzy rules. Experimental results illustrate the efficiency and the robustness of this control method on dynamically complex tasks involving interactions between two industrial manipulators.

The authors address the navigation of wheeled vehicles over the rough terrains. They present a system for simulating vehicle motions over 3-D terrain which considers the kinematics of the locomotion mechanism, the physics of the interaction between the wheels and the ground being obtained by integration of some basic aspects of terramechanics. This system is exploited to search for paths which guarantee that the vehicle remains maneuverable and stable and rolls without sliding. Paths are mapped by deforming a nominal path joining a set of subgoal points. The choice of the best path can based on different performance criteria, e.g., covered distance, energy consumption, and risk factor.

Recent advances in robotics research show that applications of robot manipulators to complex assembly problems require the use of an intelligent terminal to generate compliant micro-motions. A new approach for complex assembly tasks consisting in the use of a manipulator-gripper, like a left hand, is presented here. Previous works have been concerned with the analysis and development of the manipulator-gripper to grip and manipulate objects of various shapes, and control grasp and contact forces. Experiments are being carried out to correct small variations in the relative position and orientation of assembly parts require further development towards high-level programming system.