Zhao Ximei

Synchronous Control of Gantry Moving Type Boring-Milling Machining Centers Based-on Disturbance Observer

For gantry-moving type boring-milling machining centers, although the two sides pillars of the gantry have the same drive mechanisms, the synchronous error between two drifts of the dual linear motor is still generated by non-balanced forces adding to the cross rail, blade carrier and other moving parts, position variation of blade carrier and various uncertainty disturbances during the working process. The synchronous error causes mechanical coupling and makes the synchronous movement of the two pillars difficult. For this, the disturbance observer is designed in dual linear motor X-drifts of gantry-moving type boring-milling machining to limit the asynchronization caused by the parameters variation and external torques in this paper. Besides, load dynamic compensation of Y-drift is applied to decrease disturbance to X-drifts. The simulation results indicate that the proposed scheme has stronger robustness and better rapidity, and smaller dynamical synchronous error. So the control method can meet the demand of the controlled plant in the high precision synchronous control

Neural-network-based self-tuning PI controller for Permanent Magnet Synchronous Motor

In the servo motor drive system applications, the variation of load inertia will degrade drive performance severely. Good dynamic and static performance of servo system requires controlling inertia robustly. In this paper, in order to get the moment of rotational inertia, online identification methods based on model reference adaptive identification (MRAI) were developed. Then a well-trained neural network supplies the PI controller with suitable gain according to each operating condition pair detected. To demonstrate the advantages of the proposed neural-network based on self-tuning PI control technique, the simulations was executed in this research. Result of simulations show that the newly developed dynamic PI approach outperforms the fixed PI scheme in rise time, precise track of angular velocity, and robustness when the inertia varied.

H∞ Robust Control for Dual Linear Motors Servo System

The gantry-moving milling machining tools that adapts dual linear motors drive is a high precision and fast motion system, the factors that influence the synchronous performances of the system are not only unknown bounded disturbances but also have parameters variety, unmodelled dynamic and the nonlinear uncertainty. These factors will make the performance of the servo system worse, so they must be considered in the servo drive system of high precision and tiny-feed numerical control machine, thus the satisfying control effect can be achieved. It is difficult to meet the requirement of the synchronous performance only by the position loop; the dynamic synchronous control in the velocity inner loop should be implemented. The problem of Hinfin control for synchronous drive of dual linear servo motors used in gantry-moving milling machining center is researched in this paper. A synchronous drive controller is designed based on Hinfin control theory. When loads or disturbances are changed suddenly, the Hinfin synchronous controller can regulate rapidly so as to ensure the synchronous precision of the dual linear motors servo system. The Hinfin feedback controller guarantees synchronous precision of the synchronous linear servo system and eliminate the inferences that are the unknown and bounded disturbance, parameter uncertainties and unmodelled dynamics. The system will automatically tune the parameters of the controller so that the influences can be suppressed effectively. The simulation results show that the proposed scheme is reasonable and effective

The Study of Self-tuning Robust Control in Dual Linear Motors Synchronous Servo System

The gantry-moving boring-milling machining tools that adapts dual linear motors drive is a high precision and fast motion system, the factors that influence the synchronous performances of the system are not only unknown bounded disturbances but also have parameters variation, unmodelled dynamic and the nonlinear uncertainty. These factors will make the performance of the servo system worse, so they must be considered in servo drive system of high precision, tiny-feed numerical control machine. A new self-tuning regulator control method is presented for the dual linear motors synchronous servo system in the paper. Recursive least squares identification algorithm with insensitive region and projection tuning is applied for parameters real-time identification of the controlled plant, and Hinfin robust control algorithm is used for parameters real-time calculation of the regulator. Hinfin robust self-tuning controller is applied for the unknown and bounded disturbance, parameter uncertainties and unmodelled dynamics. The system will automatically tune the parameters of the robust controller so that the influences can be suppressed effectively. The simulation results indicate that the proposed scheme is effective and has a stronger robustness, and meets demand of speed synchronized control as well as position synchronized control for the dual linear motors synchronous servo system

H ∞ Robust Control Based on Internal Model Theory for Linear Permanent Magnet Synchronous Motor

For linear permanent magnet synchronous servo motor (LPSM), the influence of mechanically driven chain from rotation motion to linear motion in rotation servo motor is cancelled by using LPSM. But the uncertainty factors in working of LPSM, such as the quality change of active cell, the variation of coefficient of friction and push ripples caused by magnetic density distribution fluctuation and time harmonic etc, greatly influence the performance of the system. Therefore, based on the internal model control (IMC) theory and robust control theory, a new Hinfin speed controller with strong robust stability is designed for speed servo system by seeking the solutions to the standard Hinfin control problem in the paper. The approach of output point mixed sensitivity is adopted to restrain the disturbance of speed servo system dynamically and eliminate the static error and guarantee robust stability. In the process of seeking the solutions to the standard Hinfin control problem, an approximate internal model is introduced into disturbance path to simplify the design and satisfy the high-powered servo requirement. On the other hand, Hinfin load disturbance observer is designed to overcome thrust ripples of LPSM more effectively. The simulation results show the proposed method is quite effective

Individual variable pitch control of wind turbines

Focusing on the tilt moment and yaw moment caused by asymmetric wind, aerodynamic model for individual pitch control of large-scale wind turbine was established. As the aerodynamic model have characteristics of multiple variables, strong coupling and time-varying. First, we convert it into a linear time-invariant and non-coupled model utilizing a coordinate transformation, and so the controller design was simplified. Finally, take wind shearing as a disturbance and designed two independent PID controllers. The simulation results show that individual pitch control greatly reduced the moment and yaw moment of wind turbine.

Self-tuning Robust Control for Linear Permanent Magnet Synchronous Motor

The gantry-moving boring-milling machining tools that adapts dual linear motors drive is a high precision and fast motion system, the factors that influence the synchronous performances of the system are not only unknown bounded disturbances but also have parameters variation, unmodelled dynamic and the nonlinear uncertainty. These factors will make the performance of the servo system worse, so they must be considered in servo drive system of high precision, tiny-feed numerical control machine. A new self-tuning regulator control method is presented in the paper. Recursive least squares identification algorithm with insensitive region and projection tuning is applied for parameters real-time identification of the controlled plant, and H_\infty robust control algorithm is used for parameters real-time calculation of the regulator. H_\infty robust selftuning controller is applied for the unknown and bounded disturbance, parameter uncertainties and unmodelled dynamics. The system will automatically tune the controller parameters so that the influences can be suppressed. The simulation results indicate that the proposed scheme is effective, has stronger robustness, and meets demand of speed synchronized control as well as position synchronized control for the system.

Zero phase two-degrees of freedom H/sub /spl infin// robust tracking control for permanent magnet linear synchronous motor

For the direct-drive servo system of permanent magnet linear synchronous motor (PMLSM), a two-degrees of freedom (2-DOF) robust tracking control strategy based on combining zero phase error tracking control (ZPETC) with H/sub /spl infin// robust control is proposed in this paper. The control scheme solves the conflict between fast tracking performance and interference rejection of the linear servo system. The zero phase error tracking controller is designed to ensure that the system has fast tracking performance and implements exactly tracking, especially when it is used for contour control, better effect is obtained, it can effectively improve positioning accuracy and the fast tracking performance. While H/sub /spl infin// robust controller can overcome the influences of uncertainties of the parameters perturbation and the external load disturbances, achieve the stability and robustness of the system. The simulation results show that the control scheme not only can enhance the fast tracking performance in the linear servo system, but also has the stronger robustness to parametric variations and resistance disturbances.