Jean-François Brethé

Modelling of repeatability phenomena using the stochastic ellipsoid approach

A stochastic ellipsoid modelling of repeatability is proposed for industrial manipulator robots. The covariance matrix of angular position is determined introducing the jump process, which reveals to be a first and second order stationary Gaussian process.From this accurate covariance matrix, the stochastic ellipsoid theory gives the density of position in the workspace around the mean position. Hence the pose repeatability index can be computed in different locations. Computed and experimental repeatability are compared. Experimental repeatability variability is studied. A new “intrinsic repeatability index” is proposed. In conclusion, the modelling reflects well the location and load influence on the repeatability.

Determination of the Repeatability of a Kuka Robot Using the Stochastic Ellipsoid Approach

In this paper, we display experimental results about the measurement of repeatability of an industrial Kuka robot. We first study the distributions of the angular positions and show that these distributions can be considered as Gaussian. We compute repeatability in different locations of the workspace using the experimental angular covariance matrix and the stochastic ellipsoid modeling. We measure repeatability and observe a high variability. We explain the phenomenon by drawing the distribution of the 30 sample repeatability index. We then compare the computed andmeasured repeatability and conclude that our modeling gives good results. We analyse the incidence of weight and workspace location on repeatability and bring additional results to the existing literature.

UAV-UGV cooperation for objects transportation in an industrial area

We present in this paper a decentralized multirobot (aerial and ground) cooperation scheme for objects transportation. A team of ground mobile robots guided by a drone and a human operator moves in a coordinated way keeping a predefined formation in order to carry objects (tools, gas masks,...) in unsafe industrial areas. One ground mobile robot (leader) navigates among obstacles thanks to the waypoints provided by the drone and the human operator. The other ground mobile robots (followers) use a predictive vision based target tracking controller to keep a certain distance and bearing to the leader.

Intrinsic repeatability: A new index for repeatability characterisation

The paper deals with the question of robot precision and how to characterise repeatability. Hence ISO and ANSI repeatability indexes advantages and drawbacks are analysed. A new intrinsic repeatability index is proposed that can estimate the robot endpoint position variability satisfying the non-bias and convergence conditions. Computation of this index is performed using simulated straight and drifting trajectories. Influence of load on repeatability is studied using an experimental determination of an angular covariance matrix. Therefrom intrinsic repeatability can be computed in every workspace location using only this covariance matrix and the stochastic ellipsoid theory.

A decentralized interactive architecture for aerial and ground mobile robots cooperation

This paper presents a novel decentralized interactive architecture for aerial and ground mobile robots cooperation. The aerial mobile robot is used to provide a global coverage during an area inspection, while the ground mobile robot is used to provide a local coverage of ground features. We include a human-in-the-loop to provide waypoints for the ground mobile robot to progress safely in the inspected area. The aerial mobile robot follows continuously the ground mobile robot in order to always keep it in its coverage view.

Innovative kinematics and control to improve robot spatial resolution

The paper presents innovative kinematics and control of a planar redundant robot designed to improve spatial resolution by a factor 5. This result is obtained in a restricted area of the workspace using position information from external sensors. This innovation results from a clearer understanding of the factors that influence the robot micrometric behavior: axes control resolution generates a set of attainable points in the robot workspace and different spatial resolution patterns appear when introducing redundancy depending on the final axes chosen to correct the position.

Modeling of the orientation repeatability for industrial manipulators

In this paper, a new method for the estimation of orientation repeatability index is proposed for industrial manipulator robots. First, we compute orientation repeatability in different locations of the workspace using the experimental covariance matrix and the stochastic ellipsoid modeling. Then we display experimental results about the direct measurement of orientation repeatability for an industrial Samsung robot in different workspace locations and with different loads. The two proposed procedures are compared. We analyze the incidence of workspace location on orientation repeatability and bring additional results to the existing literature.

Vision based target tracking using an unmanned aerial vehicle

We present in this paper a backstepping controller for vision based target tracking with an Unmanned Aerial Vehicle. A down facing camera is used with a pose estimation algorithm to extract the position of the target (an Unmanned Ground Vehicle). The output is then fed into the developed controller to generate the necessary movements (pitch and roll) of the Unmanned Aerial Vehicle in order to keep the target in the coverage view of the camera (following it constantly). The developed scheme is used to help the Unmanned Ground Vehicle to navigate among obstacles, and the overall system is designed in order to help human operator to supervise the Aerial and Ground vehicles for area inspection or object transportation in industrial areas (when using multiple Unmanned Ground Vehicles).

Fuzzy logic controller for predictive vision-based target tracking with an unmanned aerial vehicle

Abstract We present in this paper a Fuzzy Logic Controller (FLC) combined with a predictive algorithm to track an Unmanned Ground Vehicle (UGV), using an Unmanned Aerial Vehicle (UAV). The UAV is equipped with a down facing camera. The video flow is sent continuously to a ground station to be processed in order to extract the location of the UGV and send the commands back to the UAV to follow autonomously the UGV. To emulate an experienced UAVs pilot, we propose a fuzzy-logic set of rules. Double Exponential Smoothing algorithm is used to filter the measurements and give the predictive value of the errors in the image plan. The FLC inputs are the filtered errors (UGV position) in the image plan and the derivative of its predicted value. The outputs are pitch and roll commands to be sent to the UAV. We show the efficiency of the proposed controller experimentally, and discuss the improvement of the tracking results compared to our previous work. Graphical Abstract

Towards An Autonomous Warehouse Inventory Scheme

We present in this paper a novel warehouse inventory scheme. The main purpose of this work is to make the inventory process completely autonomous. To this end, an Unmanned Ground Vehicle (UGV) and an Unmanned Aerial Vehicle (UAV) work cooperatively. The UGV is used as the carrying platform, and considered as a ground reference for the indoor flight of the UAV. While the UAV is used as the mobile scanner. The UGV navigates among rows of racks carrying the UAV. At each rack to be scanned, the UGV stops, and the UAV takes off to fly vertically scanning goods in that rack. Once the UAV at the top, the UGV moves to the next rack, and since the UAV takes the UGV as the ground reference, it will follow it autonomously, this results in placing the UAV at the top of the second rack, and scanning goods from top to bottom starts. the process is repeated until the row of racks is fully scanned. The UAV then lands on the UGV, and recharge its batteries while the UGV moves to the next row of racks. We present in this paper the proposed architecture, as well as the first experimental results of the proposed scheme