A decoupled path-following control algorithm based upon the decomposed trajectory error

This paper proposes a new path-following control algorithm for the machine tool servo systems. The control system first decomposes the contouring error into the normal tracking error and the advancing tangential error. A dynamic decoupling procedure is then applied to the system dynamics. Finally, a dynamic decoupled controller is proposed to compensate the decomposed tangential and the normal tracking errors. The normal control minimizes the perpendicular tracking error while the tangential control maintains a desired feed rate. The proposed method is applied to the control of an experimental x–y table. Experimental results show that the proposed control can achieve good tracking and trajectory following characteristics. The new algorithm also enables the design of a non-overshooting controller along the path. This will result in a no-overcutting process for the machine tool operation.     

Oscillations and transfer properties of relay servo systems—the locus of a perturbed relay system approach

A frequency-domain method of the input-output analysis of a class of relay feedback systems is proposed. The approach is based on the notion of the locus of a perturbed relay system (LPRS). The proposed LPRS is defined as a characteristic of the response of a linear part to an unequally spaced pulse control of variable frequency in a closed-loop system. Consequently, the LPRS comprises oscillatory and transfer properties of the relay system. Formulas for computing the LPRS are derived. An example of input-output analysis is given.     

Servo parameter tuning for a 5-axis machine center based upon GA rules

This paper addresses the use of the genetic algorithm (GA) to tune the servo controller in a multi-axis CNC machine center. Because the number of parameters in a CNC controller is usually very large and their effects are highly coupled, tuning these parameters is a task requiring great skill. In this paper, the genetic algorithm is applied to tune the servo parameters in a commercial CNC machine controller. The controller is a PC-based open architecture system, thus allowing the GA to be implemented on a personal computer. In this study, a dynamic mutation amplitude process is also introduced to improve the quality of evolution. Experimental results obtained on a Siemens 840D CNC controller indicate that the proposed method is able to automatically identify the effect of each parameter and to tune the controller so as to achieve expert level performance.     

Design and dynamic characterization of a gyroscopic system for aerobatic UAV helicopters

This paper describes the design, development and dynamic characterization of a high performance MEMS-based gyroscopic control system for the yaw channel of Unmanned Aerial Vehicles (UAVs) Radio Controlled (RC) helicopters for aerobatic maneuvers. A new asymmetrical controller has been developed that compensates the torque of the main rotor thus providing equal dynamic response in clockwise and anticlockwise pirouettes. The “in flight” dynamic characterization showed that the proposed system can be up to five times faster than the state of the art for commercial gyros at higher yaw rates; the regime yaw rate characterization demonstrated a high and constant pirouette speed. Aerobatic tests demonstrated high accuracy entry into the maneuvers.