Scaled Teleoperation Controller Design for Micromanipulation over Internet Moussa Boukhnifer Antoine Ferreira Jean-Guy Fontaine Laboratoire Vision et Robotique, ENSI de Bourges-Université d’Orléans, 10 Bld. Lahitolle, 18020 Bourges, France, antoine.ferreira@ensi-bourges.fr Abstract: Recent developments on micro/nano manipulation and internet technologies allow potential impacts on networked- micro-automation of small industrial products. However, reliable and efficient tele-micromanipulation systems with haptic feedback over the Internet face to strong problems due to the nonlinear nature of microenvironment and time-varying delays in communication lines. Towards this end, this paper presents a robust bilateral controller design using H ∞ -optimal control and µ-synthesis frameworks. This approach allows a convenient means of tradeoff the optimization of various performance criteria (micro scale force/position) and robustness for a pre- specified time-delay margin and force scaling factors. The validity of the proposed method is demonstrated by simulations and experiments for a pick-and-place micromanipulation task. Key words: teleoperation, time delay, scale factors I. INTRODUCTION The field of micromanipulation is still in its initialisation stage and a wide variety of applications are emerging – ranging from high-precision assembly of mechanical microcomponents from MEMS industry [1] to the handling of cells in medical or biological applications. However, to make these systems efficient and safe, multimedia information should be provided to the operator, which transfers human feeling to remote microenvironment through bilateral teleoperation. Different problems should be solved. As visual feedback of scaled environment is of low quality and offer limited information, force/tactile sensor information should be provided to the operator for force reflection during manipulation. The general structure of this scheme is shown in Fig.1, where the operator sends position commands and receives force feedback and video feedback. However, in bilateral micromanipulation the scaling effects, i.e., the dominant physical quantities in the micro world are different from those of macro world. Adhesive forces (electrostatic force, van der Waals force and surface tension) tend to be more dominant than the gravity [2]. In the design of a bilateral controller for efficient and robust micromanipulation, scaling between micro and macro environments’ forces should be carefully examined and tuned [3],[4],[5]. In addition variable delays in the communication line have so far been neglected in the analysis of bilateral micromanipulation. Untreated, even small delays (in the order of several hundred milliseconds) can lead to unstabilities of current microteleoperation systems. The commonly proposed approaches to deal with bilateral teleoperation with time-varying delays are mainly based on the scattering theory formalism [6], wave variable concept [7], or event-based controller [8]. These methods have proved their robustness in presence of time-delays less than one second. However, their application in presence of different-scaled worlds with scaling effects problems have never been validated. Figure 1: The video and force feedback control scheme of the internet-based microteleoperation system used in the experiment. Recent controller designs using robust H ∞ control theory and µ-synthesis/analysis are very effective for teleoperation. At the macro scale, Kazerooni [9] established an H ∞ based framework to design a teleoperation controller which transmits only force information and no position data. Yan and Saculdean [10] used H ∞ -optimization to design controllers for motion scaling. Finally, Leung et al. used µ-synthesis to design controllers for teleoperation under time-delay [11]. None of the above papers solves the problem of robust stability and performance of bilateral micromanipulation in the presence of a time-varying delay, force scaling effects and environment variation. In this study, the design of time-varying H ∞ controller with on-line control of the scaling parameters for a network-based force- reflecting teleoperation is examined. The paper is organized as follows. In section 3, the design of the time varying H ∞ controller with compensation of time-delay and on-line control of the scaling parameters is discussed. In Section 4, the I N T E R N E T Vision feedabck x s Force feedback f s Gripper command Micromanipulator Remote Operator Force feedback f m Master command Vision feedback x m f h f hd Proceedings of the 2004 IEEE International Conference on Robotics & Automation New Orleans, LA • April 2004 0-7803-8232-3/04/$17.00 ©2004 IEEE 4577