Soft Motion Trajectory Planner for Service Manipulator Robot

Human interaction introduces two main constraints: Safety and Comfort. Therefore service robot manipulator can't be controlled like industrial robotic manipulator where personnel is isolated from the robot's work envelope. In this paper, we present a soft motion trajectory planner to try to ensure that these constraints are satisfied. This planner can be used on-line to establish visual and force control loop suitable in presence of human. The cubic trajectories build by this planner are good candidates as output of a manipulation task planner. The obtained system is then homogeneous from task planning to robot control. The soft motion trajectory planner limits jerk, acceleration and velocity in cartesian space using quaternion. Experimental results carried out on a Mitsubishi PA10-6CE arm are presented

Manipulation robotisée et interaction

Humans build more and more evolved machines to facilitate their life. The next stage of this evolution will be the construction of robots capable of choosing, defining and finally achieving a task autonomously in the middle of humans. To accomplish this objective, planning and control tools for manipulation tasks are presented. The concept of soft motions that are constituted by cubic functions enables, on the one hand, to plan trajectories that take into account time, and security and comfort constraints for users, and on the other hand, to do a link between planning and control. The grasp planning and the study of the stability of grasps constitute a key element of the manipulation planning. The study of dynamic and friction are indispensable to the understanding of manipulation. Interaction between humans and robots is tackled from the study of the hand over of an object that is equipped with sensors to measure interaction forces.Les humains construisent des machines de plus en plus évolués pour se faciliter la vie. La prochaine étape de cette évolution sera la construction de robots capables de choisir, définir et enfin accomplir une tâche de manière autonome au milieu des humains. Pour atteindre ce but, des outils de planification et de contrôle pour des tâches de manipulation sont présentés. La notion de mouvements souples constitués de suites de fonctions cubiques permet, d'une part, de planifier des trajectoires en prenant en compte le temps et les contraintes de confort et de sécurité des utilisateurs, et d'autre part, de faire le lien entre planification et commande. La planification de prises et l'étude de leurs stabilités constitue un élément clé de la planification de tâches de manipulation. L'étude de la dynamique et des frottements sont indispensables à la compréhension de la manipulation. L'interaction entre humains et robots est abordée à partir de l'étude de l'échange d'un objet équipé de capteurs pour mesurer les forces d'interaction

Raisonnement geometrique et synthese de strategies d'assemblage en robotique

SIGLEINIST T 73977 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Online task space trajectory generation

International audienceAs the kinematic of the robots becomes complex and the task to realize are more and more demanding, we need tools to better define and manipulate the movements of the robots. To cope with this problem, we propose a family of trajectory, which we name the Soft Motion trajectories, defined by polynomial functions of degree three. Based on these trajectories we propose a set of tools to generate trajectories and control the robots. We present some experimental results showing the interest of the approach that unify the data exchanged from the planning level to the control level of the robot

Trajectory Smoothing using Jerk Bounded Shortcuts for Service Manipulator Robots

International audienceThis paper aims to smooth jerky trajectories for high-DOF manipulators with Soft Motion [1] shortcuts which are bounded in velocity, acceleration and jerk. The algorithm presented here iteratively picks two points on the trajectory and attempts to replace the intermediate trajectory with a shorter and collision-free segment. The objective of this algorithm is to shorten the execution time of an input trajectory as much as possible while retaining the feasibility. Simulation and real-world experimental results on reaching tasks in human environments show that this technique can generate smooth and collision-free motions for a KUKA LightWeight Robot

ON-LINE TRAJECTORY GENERATION CONSIDERING KINEMATIC MOTION CONSTRAINTS FOR ROBOT MANIPULATORS

International audienceThis paper aims to propose an on-line trajectory generation algorithm that is able to address not only constant but also time-variant kinematic motion constraints for multi-DOFs robot manipulators. By using a concatenation of cubic polynomials, the proposed method can provide a smooth trajectory that is synchronized and bounded in the robot kinematic motion constraints which are expressed as upper bounds on the absolute values of velocity, acceleration, and jerk. An additional decision tree will select intermediate motion profiles when the motion constraints are abruptly changed. Due to direct computation without optimization computation or randomized algorithms, the proposed solution requires only a short execution time. Simulations and experiments were conducted to verify the feasibility and effectiveness of this algorithm in smooth trajectory generation from arbitrary states of motion. With the proposed approach, robot motion can be limited by the kinematic motion constraints which will reduce manipulator wear and improve tracking accuracy and speed. The proposed algorithm can be used in real time due to the low computational complexity

Dynamic Obstacle Avoidance using Online Trajectory Time-Scaling and Local Replanning

International audienceIn various circumstances, planning at trajectory level is very useful to generate flexible collision-free motions for autonomous robots, especially when the system interacts with humans or human environment. This paper presents a simple and fast obstacle avoidance algorithm that operates at the trajectory level in real-time. The algorithm uses the Velocity Obstacle to obtain the boundary conditions required to avoid a dynamic obstacle, and then adjust the time evolution using the non-linear trajectory time-scaling scheme. A trajectory local replanning method is applied to make a detour when the static obstacles block the advance path of the robot, which leads to failure of implementing time-scaling approach. Cubic polynomial functions are used to describe trajectories, which brings sufficient flexibility in terms of providing higher order smoothness. We applied this algorithm on reaching tasks for a mobile robot. Simulation results demonstrate that the technique can generate collision-free motion in real time

Calibrated measurement of the behaviour of mechanical junctions from micrometre to subnanometre scale: the friction force scanner

International audienceWe describe an instrument called a friction force scanner (FFS) able to perform calibrated measurements of the behaviour of mechanical junctions with more than four orders of magnitude of resolution for both displacement and force. A probe carrier is suspended by fibres in an arrangement that provides exactly two degrees of freedom of motion. The suspension makes it possible to measure the carrier displacement by interferometry. A novel differential electrostatic actuator with linear response mounted on the carrier was used to precisely determine the force experienced by a junction. The single-stage design is easily calibrated and can be used for force measurement and scanning, allowing the study of friction at multiple length scales. Measurements involving mica-mica and steel-steel junctions are reported while using the instrument in open loop

Improving Human-Robot Object Exchange by Online Force Classification

International audienceHanding an object over to a human is a challenging task for a robot to perform, especially when the human partner has no experience interacting with robots. This paper presents our work to enable a robot to learn how to achieve this task with wrist force/torque sensing. Firstly, we present a device to record the data, then we discuss the techniques used for the teaching. We choose to focus on the classification problem defined to enable the robot to find the finger opening movement. The main challenge is that the classification should be run online, at a comparable rate to the controller. To achieve a computationally efficient classifier, the Wavelet Packet Transformation is used for feature extraction, and then we used the Fisher criterion to reduce the dimension of features. A Relevance Vector Machine is used for the continuous classification procedure mainly for its sparsity. Some recorded data and the results from dimension reduction are shown, then we discuss the accuracy and sparsity of the classification by Relevance Vector Machine in this application. The software of continuous classification on forces is then tested on the robot for interactive object exchange between human and robot, which gives promising results

Improving Human-Robot Object Exchange by Online Force Classification

International audienceHanding an object over to a human is a challenging task for a robot to perform, especially when the human partner has no experience interacting with robots. This paper presents our work to enable a robot to learn how to achieve this task with wrist force/torque sensing. Firstly, we present a device to record the data, then we discuss the techniques used for the teaching. We choose to focus on the classification problem defined to enable the robot to find the finger opening movement. The main challenge is that the classification should be run online, at a comparable rate to the controller. To achieve a computationally efficient classifier, the Wavelet Packet Transformation is used for feature extraction, and then we used the Fisher criterion to reduce the dimension of features. A Relevance Vector Machine is used for the continuous classification procedure mainly for its sparsity. Some recorded data and the results from dimension reduction are shown, then we discuss the accuracy and sparsity of the classification by Relevance Vector Machine in this application. The software of continuous classification on forces is then tested on the robot for interactive object exchange between human and robot, which gives promising results