High-speed visual servoing of a 6-d.o.f. manipulator using multivariable predictive control

This paper presents a new approach to model and control high speed 6 DOF visual servo loops. The modeling and control strategy take into account the dynamics of the velocity controlled 6 DOF manipulator as well as a simplified model of the camera and acquisition system in order to significantly increase the bandwidth of the servo loop. Multi-Input Multi-Output (MIMO) Generalized Predictive Control (GPC) is used to optimally control the visual loop with respect to the proposed dynamical model. The predictive feature of the GPC is used for optimal trajectory following in Cartesian space. Experimental results on a 6 DOF industrial robot are presented that validate the proposed model. The visual sensor used in the experiments is a high speed camera that acquires 120 non interlaced images per second. Using this camera, sampling rate of 120 Hz is achieved for the visual loop. Furthermore, a precise synchronization method is used to reduce the delays due to image transfer and processing. The experiments show a drastic improvement of the loop performance with respect to more classical control strategies for 6 DOF visual servo loops.