Dae-Sik Lee

Continuous variable structure controller for BLDDSM position control with prescribed tracking performance

The continuous, accurate, and robust sliding mode tracking controller based on a disturbance observer for a brushless direct drive servo motor (BLDDSM) is presented. Although the conventional sliding mode control (SMC) or variable structure control (VSC) can give the desired tracking performance, there exists an inevitable chattering problem in control which is undesirable for a direct drive system. With the proposed algorithm, not only are the chattering problems removed, but also the prescribed tracking performance can be obtained by using the efficient compensation of the disturbance observer. The design of the sliding mode tracking controller for the prescribed, accurate, and robust tracking performance without the chattering problem is given based on the results of the detailed stability analysis. The usefulness of the proposed algorithm is demonstrated through the computer simulations for a BLDDSM under load variations. >

Direct calibration methodology for stereo cameras

This paper describes a new technique for stereoscopic 3D position measurement. By defining stereo cameras as a system for image-to-world mapping, the mapping function is determined. The direct representation of 3D coordinates of a world point with corresponding stereo image coordinates is derived using the pin-hole model. One camera frame is related to the other before being related to the world frame so that the stereo itself rather than each camera can be directly related with the 3D world. The equations obtained are simple, straightforward, and closed-form. However, since the nonlinearity of actual imaging system is not considered, high accuracy is difficult to be expected when the equation is employed for 3D measurements. For tackling this problem a multilayer feedforward neural network trained by back- propagation algorithm is used. The network played the role of fine correction satisfactorily using its function learning capability after rough mapping by the linear equations in our experiment.