Jean-Guy Fontaine

Grasping, coordination and optimal force distribution in multifingered mechanisms

In the field of multifingered mechanisms the control/command problem is mainly a problem o1 coordination. The problem is not only to coordinate joints of a chains but also to coordinate the different chains together. This paper presents a general and efficient method for implementing the control/command of such systems, taking into account the force distribution problem. To solve this problem it is necessary to pay great attention to dynamic effects. To do this, we broke down the Inverse Dynamic Model (I.D.M.) problem into two main levels; One level is devoted to I.D.M. computation; it can be called the Finger Level (F.L.). As we wanted to divide up the work to be done as much as possible, we subdivided the Finger Level according to the number o1 kinematic chains. In addition, we considered a second level, the Coordinator. This level has to control all the chains using the Fingers-to-Object-Interaction Model (F.O.LM.). Next, we will also introduce new grasping systems: Polyvalent Gripper Systems (P.G.S). There are a new solution to multicomponent assembly problems. As they can be equipped with several multifingered mechanisms, they can also use the control/command scheme.

Dynamic walk of a bipedal robot having flexible feet

The objective of the work is to evaluate the contribution of flexibilities in the feet of a bipedal robot during a dynamic walk. The two major effects are the diminution of the intensity of the normal force when the heel touches the ground and the increase of the phase of double support allowing a better stability of the system. Another notable effect is the analogy between the passive flexion amplitude of the tiptoes and the measured results of human subjects.

Wheel+legs - A new solution for traction enhancement without additive soil compaction

This paper presents the tractive performance of a one-wheeled vehicle equipped with a rotative leg appendage. Traction tests of the vehicle are performed and the maximum coefficient of traction is determined. Tests to measure the pressure distribution created by the legs on a soil bin are conducted to illustrate traction enhancement.

Virtualized reality interface for tele-micromanipulation

Operators suffer much difficulty in manipulating micro/nano-sized objects without the assistance of human-machine interfaces due to scaling effects. We developed an immersive telemanipulation system using haptic/visual/sound interfaces for observation of micro-objects under an optical microscope. As the image of the microscope is two-dimensional, so it is hard to observe the workspace in the 3-D space. To improve the real-time observation and manipulation, we proposed real-time 3-D reconstruction of the microworld using image processing and virtualized reality techniques. Then, feasible haptically-generated paths based on potentials fields reaction forces are selected for efficient pushing-based manipulation without collisions. The proposed system guides the operators gesture fully immerged in the virtual workspace.

Study of a distributed control architecture for a quadruped robot

Looking at legged robots, it is sometimes very important to take into account some of the practical aspects (when focusing on theoretical ones) in order to implement control-command levels.In this way, we have treated the problem of the realization of dynamic or quasi-dynamic gaits with a quadruped robot using a new approach from which we have derived an efficient control/command scheme. This is based on a simple consideration which lies in the fact that the Dynamic Model (DM) can be decomposed into two main parts. From our point of view, we consider a part devoted to the command of the legs which could be called a Leg Inverse Dynamic Model (LIDM). We consider a second part dealing with the global characteristics of the platform. At this level, one can control the system. It will be called the LPIM (Leg to Platform Interaction Model).This goal is reached assuming a dichotomy in a distributed architecture and by the way we present it. Further justification of our method will be given in several stages throughout the paper. We paid great attention to time-saving considerations with respect to communication protocols and data exchange at the same level and between the three levels we derived from our basic investigations.

Comparative study of adaptive controllers for a pneumatic driven leg

Makes a comparative study between two adaptive control strategies applied to a leg of a quadruped. This leg is composed of two rigid links with pneumatic actuators driving rotational joints. In order to enable nonlinear control approaches, a model of this system is built. The control design is based on one hand on MRAS and on the other hand on passive system theory which ensure the asymptotic stability of the whole. Adaptation laws are proposed, grounded either on the number of operations keeping in mind real time implementation facilities, or on the robustness toward disturbances. These control laws are compared using simulation results.<<ETX>>

Unified approach for m-stability analysis and control of legged robots

In this paper we address the issue of controlling the stability of legged robots based on the virtual generalized stabilizer (VGS) introduced in [J. Foret, et al.,2002]. The proposed approach is a theoretical framework that gives a unified point of view to design and to control the walking gaits. Although the presented work is general, the application focuses on the particular problem of static stability maintenance of a biped robot subject to a destabilizing impulsive force applied on its trunk.

Study of the dynamic behavior of RALPHY

The authors propose a control/command scheme for the quadruped robot RALPHY (French acronym for legged robot with pneumatic actuators) which takes into account both dynamical and real time aspects as well as theoretical and practical approaches. They decompose the dynamic model for the whole robot into two parts in order to distribute hierarchically the tasks to be realized as much as possible. In this architecture, the lowest level (leg level) is assigned to command the leg movements through a leg inverse dynamic model computation. At an upper level (coordinator level), the control of the platform is handled by the leg-to-platform interaction model computation. The behavior of the robot is simulated.

High parallel disparity map computing on FPGA

In this paper we present a method for disparity map computing and its correspondent high parallel hardware accelerator. Our solution considers a two step processing algorithm. First, we compute a one-dimensional biased sum of absolute differences, and later a spurious removal technique is performed to eliminate wrong estimations. The hardware accelerator introduces a memory organization, an address generation scheme and data-path units that have scalable features for several resolutions, frame rates, silicon use, and power consumption instantiations. We have implemented a five stage pipelined organization that operates at 174.5 MHz over an VIRTEX II PRO 2vp30fg676-7 FPGA device, carries out an equivalent of 9.074 GOPS and processes 142 frames per second of Common Intermediate Format (CIF).

Highly parallel implementation of Harris Corner detector on CSX SIMD architecture

We present a much faster than real-time implementation of Harris Corner Detector (HCD) on a low-power, highly parallel, SIMD architecture, the ClearSpeed CSX700, with application for mobile robots and humanoids. HCD is a popular feature detector due to its invariance to rotation, scale, illumination variation and image noises. We have developed strategies for efficient parallel implementation of HCD on CSX700, and achieved a performance of 465 frames per second (fps) for images of 640×480 resolution and 142 fps for 1280×720 resolution. For a typical real-time application with 30 fps, our fast implementation represents a very small fraction (less than %10) of available time for each frame and thus allowing enough time for performing other computations. Our results indicate that the CSX architecture is indeed a good candidate for achieving low-power supercomputing capability, as well as flexibility.