Laboratoire de commande et de robotique

A robust internal force-based impedance control scheme for coordinating manipulators is introduced. Internal force-based impedance control enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects and requires no knowledge of the object dynamic model. Each manipulator's nonlinear dynamics is compensated by a robust auxiliary controller which is insensitive to robot-model uncertainty and payload variation. The controller is only weakly-dependent on each manipulator's inertia matrix. Stability of the system is analyzed. The scheme is computationally inexpensive and suitable for general-purpose microcomputer implementation. Rigorous experimental investigations are performed and the results presented which validate the proposed concepts.

In 1868, James C. Maxwell published a paper, "On Governors," in Proceedings of the Royal Society of London [1]. This paper was overlooked for a long time because it was deemed by many to be difficult to comprehend. However, since Norbert Wiener drew attention to this paper in 1948, it has been recognized as the first significant paper on control theory; as a result, Maxwell has been regarded as the "father of control theory" [2]. The purpose of this article is to provide historical information on the origin of stability analysis in Maxwell's paper and to rederive his key equations using illustrative figures to improve the readability of that paper.

Providing a safe and rich environment to achieve ambulatory rehabilitation of the elderly, accident victims, or physically impaired patients, has motivated many researchers to develop lower limb prosthetic systems able to transmit physical stimuli at the skin surface. To this end, we propose a novel event-based method of synthesizing the vibratory characteristics of different types of material, such as broken stone, concrete, snow, sand, and earth, during walking, by using automatically generated Infinite Impulse Response (IIR) filters with pseudo-randomized coefficients to ensure a unique vibration at every step. As a first step, theoretical results were obtained by providing a simulated force input signal into the IIR filter's Real-Time Simulink model. The outcomes proved to be promising and demonstrated that the synthesized signals are highly comparable to the measured material response in both time and frequency domains. A comparison of the signals obtained by the proposed IIR filter approach and a physical model based technique is presented. Finally, this paper presents a new lower limb prosthetic-skin interface with the capabilities of rendering interactions measured at the foot such as vibrations and pressure points.

An arm-wrestling robot called Robo Armwrestler has recently been developed in our Intelligent Control and Robotics Laboratory to benefit the health care of senior citizens. In this article we have presented the system design, implementation, force feedback control, and generation of intelligent arm-wrestling scenarios of an arm-wrestling robot. Although Robo Armwrestler works as expected with the designed autonomy and reasonable control performance, we plan to further pursue research to provide the device with the ability to recognize facial expressions of a human using a Webcam and thus emotionally communicate with the player. Moreover, we plan to add degrees-of-freedom for more human-like motion and to eventually integrate arm-wrestling functions into a humanoid robot.

This paper deals with an extended output- feedback positioning tracking of a servo-system with friction based on generalized Maxwell-slip (GMS) friction observer dynamics with fixed model parameters. We succeed in designing a linear time invariant (LTI) compensator which ensures exponential stabilization and additional multi-objective features (e.g. closed-loop pole location). These conditions are expressed in terms of linear matrix inequalities (LMIs). Numerous simulations results illustrate the effectiveness of the proposed compensator and state a comparison with the similar LuGre closed-loop friction compensator.

This article describes design, hard- and software implementation of devices and a workflow for acquisition, processing, storage and analysis of multispectral material signatures. An approach for a consistent process from measurement to analysis is presented, utilizing standard formats for multi-dimensional image data. Finally applications are demonstrated that make use of the material signatures database.

While collaborative robotic arms offer significant safety benefits, safety of the overall manipulator system cannot be guaranteed unless equally strict safety requirements are satisfied by the accompanying end-effector. Current robot grippers are not made in a way that fulfills such a requirement, resulting in collaborative robots needing to operate in a protected environment. This paper presents a novel permanent magnet actuator inside of a conventional industrial electric gripper which results in an end-effector that has an unmatched force range of 1-2N to 43N and exhibits interesting characteristics suited to the requirements of a safe gripper such as torque holding without power, variable stiffness and force sensing.