In this paper, a force/vision control strategy is proposed for the robotic cutting of soft materials. The separation is performed by repeating a series of cuts, called passages, along a deformable three dimensional curve. An image based visual servoing system is proposed to control all six degrees of freedom of the cutting tool. This allows the system to change the cutting depth and angle in response to changes in the profile of the surface. The force is used to ensure the cut is performed cleanly without globally deforming the soft material. The proposed controller is validated experimentally by cutting soft foam material.

In this paper, a force/vision control strategy is proposed in order to separate soft deformable materials using cooperative robots. The separation is performed by repeating a series of cuts, called passages, along a curved trajectory. The vision control is used to locally update the robot trajectory in response to both on-line deformations and off-line modeling errors. The force controller is used to ensure that the cut is performed without global deformation or damage to the surrounding area. The second robot is used to facilitate the cutting by applying external forces to the object. The control scheme is validated experimentally by cutting soft foam material.

Modeling and simulation are fundamental tools to develop new urban vehicles. The aim of this work is to model and simulate a narrow urban tilting car, which should significantly decrease traffic congestion, pollution, and parking problems. The structure of the vehicle contains closed kinematic chains. The modeling approach is based on the modified Denavit and Hartenberg description, which is commonly used in robotics, by considering the vehicle as a mobile robot composed of a multibody poly-articulated system in which the terminal links are the wheels. This description allows automatic calculating of the symbolic expressions of the geometric, kinematic, and dynamic models. A simulator is developed with MATLAB/Simulink, and the simulation of different scenarios is performed and analyzed.

This paper presents a symbolic and recursive calculation of the dynamic model of flexible parallel robots. In order to reduce the computational time, it is necessary to minimize the number of operators in the symbolic expression of the model. Some algorithms have been proposed for the rigid case, for parallel robots with lumped springs or for serial robots with distributed flexibilities, but to the best of our knowledge, nothing has been developed for parallel robots with distributed flexibilities. This paper aims at filling this gap. In order to minimize the number of operations, the Newton- Euler principle is used and combined with the principle of virtual powers. The Jacobian matrices defining the kinematic constraints are computed using recursive calculations that decrease the number of operators. The proposed algorithm is used to compute the elastodynamic model of a planar parallel robot. The obtained results, compared with those obtained with commercial softwares, show the validity of the proposed algorithm.

We propose an efficient stochastic scheme for minimum-time trajectory planning of a nonholonomic unicycle mobile robot under constraints on path curvature, velocities, and torques. This problem, which is known to be complex, often requires important runtimes, particularly if obstacles are present and if full dynamics is considered. The proposed technique is a fast variant of the random-profile approach recently applied to wheeled-mobile robots. It incorporates a trapezoidal-velocity-profile constraint that helps reduce the number of unknown parameters and that speeds up the calculation steps. Results are presented for two- and three-wheel mobile robots in free/constrained workspaces. A comparison with reference solutions, which were obtained independently, shows that the proposed variant is able to achieve almost the same quality of calculated trajectories while reducing the runtime considerably.

In this paper, we present the dynamic modeling of a 3D-hybrid underwater eel-like robot using recursive algorithms based on the Newton-Euler equations. The robot is composed of a sequence of parallel modules connected in series. The algorithm gives the head accelerations and the joint torques as a function of the Cartesian positions, velocities and accelerations of the platform of the modules. The proposed algorithm can be considered as a generalization of the recursive Newton-Euler inverse dynamic algorithm of serial manipulators with fixed base. The proposed algorithm is easy to implement and to simulate whatever the number of degrees of freedom of the robot. An example with 12 parallel modules is presented.

In this paper we present four methods for the identification of the inertial parameters of the load of a manipulator. The knowledge of the values of these parameters can be used to tune the control law parameters in order to improve the dynamic accuracy of the robot. They can also be exploited to verify the load transported by the robot. The methods presented have been validated using Staubli RX 90 robot. The experimentation has been carried out using data collected from the industrial control system (version CS8) of the manufacturer. This version allows to have access to joint positions, velocities and torques. The methods presented are based on solving linear system of equations using weighted least squares solution.

This paper presents the dynamic modeling of a 3-D-serial underwater eel-like robot using recursive algorithms based on the Newton--Euler equations. Both direct and inverse models are treated in the paper. The inverse dynamic model algorithm gives the head acceleration and the joint torques as a function of the joint positions, velocities, and accelerations. The direct dynamic model gives the head and joint accelerations as a function of the joint positions, velocities, and input torques. The proposed algorithms can be considered as a generalization of the recursive Newton--Euler dynamic algorithms of serial manipulators with fixed base. The algorithms are easy to implement and to simulate whatever the number of degrees of freedom of the robot. An example with 12 spherical joints is presented. The fluid forces have been taken into account using a simple model based on Morison's model.

This paper presents a new method to generate suboptimal trajectories for serial manipulators in both configuration and Cartesian space. The method is based first on the dissociation of the search of optimal transfer time T from that of optimal trajectory profiles. Kinematic and dynamic constraints can then be treated in an easy manner because most of them can be transformed into bounds on the value of T. In addition, trajectory profiles are generated using trapezoidal velocity profiles that reduce the number of optimization parameters to two only. This makes the real-time trajectory generation possible and its implementation on existing industrial controllers quite easy. Furthermore, a stochastic optimization method is suggested to obtain a good approximation of the global optimal motion

This paper presents a recursive solution for the inverse dynamic modeling of hybrid robots that are constructed by serially connected parallel modules. The proposed solution generalizes the recursive Newton-Euler algorithm developed for serial robots, and uses the compact form of the inverse dynamic model of parallel robots that was proposed recently by the authors

This paper deals with the problem of dynamic modeling and identification of passenger cars. It presents a new method that is based on robotics techniques for modeling and description of tree-structured multibody systems. This method enables us to systematically obtain the dynamic identification model, which is linear with respect to the dynamic parameters. The estimation of the parameters is carried out using a weighted least squares method. The identification is tested using vehicle dynamics simulation software used by the car manufacturer PSA Peugeot-CitroËn in order to define a set of trajectories with good excitation properties and to determine the number of degrees of freedom of the model. The method has then been used to estimate the dynamic parameters of an experimental Peugeot 406, which is equipped with different position, velocity, and force sensors.

This paper presents the dynamic modeling of a continuous three-dimensional swimming eel-like robot. The modeling approach is based on the "geometrically exact beam theory" and on that of Newton-Euler, as it is well known within the robotics community. The proposed algorithm allows us to compute the robot's Galilean movement and the control torques as a function of the expected internal deformation of the eel's body

In this paper, we present the dynamic modeling of a 3D-serial underwater eel-like robot using recursive algorithm based on the Newton-Euler equations. The algorithm gives the head accelerations and the joint torques as a function of the joint positions, velocities and accelerations. The proposed algorithm can be considered as a generalization of the recursive Newton-Euler inverse dynamic algorithm of serial manipulators with fixed base. The proposed algorithm is easy to implement and to simulate whatever the number of degrees of freedom of the robot. Simulation results with a 12-spherical joint structure are presented.

In this paper, we present a general method to calculate the inverse dynamic models of parallel robots. The model is expressed in terms of one equation, which is a function of the dynamic models of the legs, the dynamics of the platform and three Jacobian matrices. The method is applied on four robots with different degrees of freedom and different structures. Consequently, the computational complexity of the obtained models can be reduced by making use of the techniques.

This paper presents closed-form solutions for the inverse and direct dynamic models of the Gough-Stewart parallel robot. The models are obtained in terms of the Cartesian dynamic model elements of the legs and of the Newton-Euler equation of the platform. The final form has an interesting and intuitive physical interpretation. The base inertial parameters of the robot, which constitute the minimum number of inertial parameters, are explicitly determined. The number of operations to compute the inverse and direct dynamic models are given.

This paper presents the experimental identification of the dynamic parameters of the Orthoglide, a 3-DOF parallel mechanism. The dynamic identification model is based on the inverse dynamic model, which is linear in the parameters. The model is computed in a closed form in terms of the Cartesian dynamic model elements of the legs and of the Newton-Euler equation of the platform. The base inertial parameters of the robot, which constitute the identifiable parameters, are given.

Presents a closed form solution for the inverse and direct dynamic models of a Gough-Stewart platform. The models are calculated in terms of the Cartesian dynamic model elements of the legs and of the Newton-Euler equation of the platform. The final form has an interesting physical interpretation, which can be used to derive the dynamic models of other parallel structures.

Presents a numerical method for the determination of the identifiable parameters of parallel robots. The special case of Stewart-Gough 6 degrees-of-freedom parallel robots is studied for classical and self calibration methods, but this method can be generalized to any kind of parallel robot. The method is based on QR decomposition of the observation matrix of the calibration system. Numerical relations between the parameters which are identified and those which are not identifiable can be obtained for each method.

Presents a method for the modeling of mechanical systems with lumped elasticity. The main applications of the method concern high speed machine tools and robots with elastic joints. The method can provide the kinematic and dynamic models of such systems. To achieve this goal we adapted some well known tools and notations which are widely used for rigid robots. The inverse dynamic model has to be redefined and developed.

Presents a method for the kinematic calibration of six degrees of freedom parallel robots using two inclinometers. The calibration model takes into account the error on the angle between the inclinometers axes. The estimation of the parameters is carried out using the Levenberg-Marquardt algorithm. The number of configurations needed and the effect of noise on sensors data are studied using simulations.

Presents a method for the autonomous calibration of six degrees-of-freedom parallel robots. The calibration makes use of the motorized prismatic joint positions corresponding to some sets of configurations where in each set either a passive universal joint or a passive spherical joint is fixed using a lock mechanism. Simulations give us an idea about the number of sets that must be used, the number of configurations by set and the effect of noise on the calibration accuracy. The main advantage of this method is that it can be executed rapidly without need to external sensors to measure the position or the orientation of the mobile platform.

This article presents a new approach of modeling the dynamics of flexible manipulators composed of slender elastic beams. Contrary to the standard dynamic modeling approaches the model proposed here does not require any assumption on the smallness of the elastic displacement and rotation fields. Thus the given model is completely nonlinear with respect to the elastic kinematics and leads by using Taylor series expansions to the exact first and second order dynamic models.

This paper presents an efficient algorithm for the calculation of the direct dynamic model of flexible manipulators. The algorithm is based on the inverse Newton-Euler model of flexible manipulators as developed previously by the authors (1995). The given algorithm can be considered as a generalization of the rigid manipulators algorithm given by Walker-Orin (1982). The algorithm is programmed using Mathematica to obtain automatically customized symbolic models with reduced number of operations.

This paper presents a new method for the calculation of the filtered dynamic model of robots which is used in the adaptive control of robots and in the identification of its inertial parameters. The main characteristics of the method is that no symbolic differentiation is used. The variables used in the algorithm are obtained from the transformation matrices between successive link frames. The number of operations in the general case and for some industrial robots are given.

This paper presents the experimental results of the identification of the dynamic parameters of the 6 degree of freedom SR400 robot. This industrial robot is characterized by having a parallelogram closed loop and a mechanical coupling between the joints of the hand. The different steps starting from the modelling up to the validation of the results are given. Practical issues are addressed.

In this paper, we propose an efficient recursive computation of the nonlinear computed torque law of flexible manipulators. The algorithm is based on the generalized Newton-Euler model of flexible manipulators and can be considered as a generalization of the computed torque control algorithm of rigid robots proposed by Luh-Walker-Paul (1980). It is programmed using Mathematica to get automatically an efficient customized symbolic model with reduced number of operations.

This paper presents a new method for the calibration of the geometric parameters of the links and tool of serial robots. The main characteristics of the method is that no external sensor is needed (only the position sensors of the joints are required), and that it can be put to practice quickly and precisely. The identifiable parameters given by the proposed method are compared with those of the classical method using an external position sensor. The algorithm has been applied to a Puma 560 robot using its standard control system. Some practical issues concerning the experimental results are given.

The paper presented by Gautier and Khalil (see ibid., vol.6, no.3, p.368-73, 1990) gives a direct and efficient method of calculating most of the minimum inertial parameters of serial robots. Some parameters concerning the translational links between the first two rotational joints that are not parallel need particular calculation; partial results concerning the case where these links are either perpendicular or parallel are given in the above paper. This correspondence presents a direct solution of this particular case, such that all the minimum inertial parameters can be obtained directly without calculating the energy or the dynamic model of any link.>

The authors present two methods for determining the base inertial parameters of robots containing closed loops. This set of parameters is the minimum set which can be identified using the dynamic or energy model. The first method is symbolic; the solution is obtained by first determining the quasi base parameters of a corresponding tree structure robot; the closed-loops are then taken into account to get the quasi base parameters of the robot. Direct general relations are given for the two steps. The second method is numerical; the multiple solutions of the relations expressing the passive variables as a function of active variables are taken into account; the number of the base parameters is seen to be a function of each solution.>

A symbolic method to determine the minimum set of inertial parameters of robots containing parallelogram closed loops is presented. The solution is obtained by determining the minimum inertial parameters of an equivalent tree structure. Then, the constraint equations of the closed loops are taken into account to get the global minimum inertial parameters. Direct general relations are obtained for the two steps.>

A symbolic method of determining the minimum set of inertial parameters of robots containing parallelogram closed loops is presented. The solution is obtained by determining the minimum inertial parameters of an equivalent tree structure robot and then taking into account the constraint equations of the closed loops to get the global minimum inertial parameters. Direct general relations that do not require the calculation of the dynamic model of the system are obtained for the two steps. The method is general whatever the values of the geometric parameters.>

The determination of the minimum set of inertial parameters of robots contributes to the reduction of the computational cost of the dynamic models and simplifies the identification of the inertial parameters. These parameters can be obtained from the classical inertial parameters by eliminating those that have no effect on the dynamic model and by regrouping some others. A direct method is presented for determining the minimum set of inertial parameters of serial robots. The method permits determination of most of the regrouped parameters by means of closed-form relations.>

A direct method is developed to determine the minimum set of inertial parameters of tree-structure robots giving complete information. The method makes it possible to classify most of the regrouped parameters by closed-form relations. A linear model for the identification of the minimum inertial parameters is also presented. The identification model is computationally simple; it is a function of the joint positions and velocities and does not need to calculate the joint accelerations. The identification model is based on the energy theorem, providing a model which is linear in the link parameters.>

An algorithm for the solution of the inverse kinematic problem of the redundant robots is presented. The method has the advantage of generating efficient symbolic solution from the number-of-operations point of view; it gives the null space solution with a computational cost comparable to that of the pseudoinverse solution. The given method can be used to provide most of the optimization criteria used in the literature; an exact solution is proposed for most of them.>

A direct method is presented to determine the minimum set of inertial parameters of robots. The set consists of the classical parameters that affect the dynamic model and the regrouped parameters. The method permits to most of the regrouped parameters to be determined by means of a closed-form function of the geometric parameters of the robot. It is proved that the minimum number of inertial parameters is less than 7n-4, where n is the number of joints. The method is general whatever the values of the geometric parameters. The method can be extended to tree structure robots and will be integrated into the software package SYMORO.>

This paper presents an efficient algorithm for the solution of the pseudo inverse kinematic problem of robots. The given inverse kinematic calculationcan be usedatthe singular positions and for redundant robots. The presented method has the advantages of being explicit and that it reduces considerably the number of operations compared to the numerical methods.

An efficient method for the calculation of the inverse dynamic models of tree structure robots is presented. The given method reduces significantly the computational burden such that the inverse dynamics can be computed in real time at servo rate. The method leads almost directly to models with a minimum number of arithmetic operations. The method is based on a Newton-Euler formulation that is linear in the inertial parameters, on an iterative symbolic procedure, and on condensating the inertial parameters by regrouping and eliminating some of them. The description of the robot is carried out by a new notation inspired from Denavit and Hartenberg notation. A Fortran program has been developed to generate automatically the dynamic models of tree structure robots.

This paper presents a new geometric notation for the description of the kinematic of open-loop, tree and closed-loop structure robots. The method is derived from the well-known Denavit and Hartenberg (D-H) notation, which is powerful for serial robots but leads to ambiguities in the case of tree and closed-loop structure robots. The given method has all the advantages of D-H notation in the case of open-loop robots.

This paper presents an efficient method for the calculation of the inverse dynamic model of robots. The given method reduces significantly the computational burden such that the inverse dynamics can be computed on real time at servo rate. The method leads almost directly to models with minimum number of arithmetic operations. The method is based on Newton-Euler formulation, on an iterative symbolic procedure and on an analysis of the links inertial parameters which leads to condensate their number by eliminating and regrouping some of them. A FORTRAN program has been developed to generate automatically the dynamic models of open chain robots.