Keynote Speaker 1:
Prof. Shyh-Leh Chen

Professor, National Chung Cheng University, Taiwan


Topic: Contouring Control of Multi-axis Motion Systems with Equivalent Contour Errors

Abstract:  Contouring control is an important motion control task for multi-axis motion systems. It requires that the output position of the system follow a given path in the task space. The contouring control problem can be found widely in the applications of robotics, computer-numerical-controlled (CNC) machine tools, etc. It aims at reducing the contour error, which is defined by the minimum distance between the actual output position of the system and the desired path. Improving contouring accuracy is an important problem since it directly affects product quality. One major difficulty in this problem is the representation of the contour error in terms of the measurable axis displacements. In general, such representation requires complicated nonlinear functions and analytical form may not be available. Most approaches adopt linear approximation and hence the performance of the contouring controller may be degraded.

In this talk, the concept of equivalent contour error will be introduced. The equivalent contour error is based on the algebraic equations that describe the desired path. It is equivalent to the actual contour error in the sense that reducing it is equivalent to reducing the actual contour error. Thus, the equivalent contour error can be taken as an alternative control objective. No approximations are needed and excellent contouring performance can be achieved. We have developed the method for systems without constraint, with holonomic or non-holonomic constraints. The method has been successfully applied to a variety of practical systems, including multi-axis machine tools, robot manipulators, Stewart platform, and two-wheeled inverted pendulum system.


Keynote Speaker 2:
Prof. Radom Pongvuthithum

Professor, Chiang Mai University, Thailand

Topic: Control Designs for Time-Delay Nonlinear Systems with Lower-Triangular Structures and Unknown Control Directions

Abstract: A class of nonlinear systems in the lower triangular form has attracted considerable attention from researchers because many physical systems, including mechanical, electrical and bio-chemical systems, can be transformed into a lower-triangular form. System uncertainties naturally arise due to a lack of knowledge of the system, or system conditions changing from internal or external factors. These uncertainties can include structural uncertainties, parametric uncertainties, time-delays and control directions. The less system information is used in the control design, the more robust the controller becomes.

This presentation discusses various control designs for nonlinear systems in the lower-triangular form and beyond that can deal with structural uncertainties, parametric uncertainties and recent developments in control designs for unknown time-delays in states and unknown control directions.