Position Control Loop Research Articles

산업용 컨버팅 머신의 펜듈럼 덴서 모델링 및 해석

Dancer system is typically used equipment for attenuation of tension disturbances. In industrial converting machines, a composite type of dancer system is applied which is mixture of active and passive dancer. It includes feedback position control loop of roll with pendulum dancer and its characteristics is different from passive and active one. In this paper, a mathematical model of the pendulum dancer was derived including PI position feedback controller and it was analyzed by using a pole-zero map and bode plot under various conditions. It was found out that velocity, length of span and inertia were associated with the performance of regulation. It was suggested that the length of upstream span should be greater than that of the downstream and the inertia should be smaller for improvement of the performance. The results can be used for design guidelines of the industrial dancer system.

Backstepping Approach for Controlling a Quadrotor Using Lagrange Form Dynamics

The dynamics of a quadrotor are a simplified form of helicopter dynamics that exhibit the same basic problems of underactuation, strong coupling, multi-input/multi-output design, and unknown nonlinearities. Control design for the quadrotor is more tractable yet reveals corresponding approaches for helicopter and UAV control design. In this paper, a backstepping approach is used for quadrotor controller design. In contrast to most other approaches, we apply backstepping on the Lagrangian form of the dynamics, not the state space form. This is complicated by the fact that the Lagrangian form for the position dynamics is bilinear in the controls. We confront this problem by using an inverse kinematics solution akin to that used in robotics. In addition, two neural nets are introduced to estimate the aerodynamic components, one for aerodynamic forces and one for aerodynamic moments. The result is a controller of intuitively appealing structure having an outer kinematics loop for position control and an inner dynamics loop for attitude control. The control approach described in this paper is robust since it explicitly deals with unmodeled state-dependent disturbances and forces without needing any prior knowledge of the same. A simulation study validates the results obtained in the paper.

Compensation of nonlinearities in active magnetic bearings with variable force bias for zero- and reduced-bias operation

Compensation of the active magnetic bearing actuator nonlinearities for a variable force bias control is demonstrated. Instead of the classical premagnetization current, a force bias is applied. In the proposed novel compensation method, the magnetic force bias is produced by an on-line tunable set bias current, which may be adjusted by some upper control scheme. The compensation of the nonlinearities for the zero- and reduced-bias operation is implemented as a part of the inner current control loop. In the outer position control loop, an optimal stabilizing controller is employed. With a controller applying the compensation of nonlinearities and the zero-bias current, it is possible to achieve a dynamic performance comparable with that of a controller with the classical bias current. Stable operation under step position references and external impulse disturbance forces with the zero force bias is shown. Additionally, the initial lift up of the rotor with the zero force bias is presented and the robust stability of the compensated controller is verified using sensitivity functions.

Performance Analysis of a Robust Positional Control with an Induction Actuator by Using a Simplified Indirect Field Oriented Control Algorithm

The aim of this paper is to study the performance of a simplified indirect field oriented control algorithm suited for small power induction actuators. The main particularities of the control strategy under study are the use of a disturbance observer in the speed and position control loops, and the absence of any current measurement. The good performance of the proposed control strategy, particularly as concerns the flux control sensitivity to parameter uncertainties, is shown by theoretical results and digital simulations.

Attitude model identification of on‐orbit satellites

PurposeThe purpose of this paper is to propose an identification algorithm to obtain generalized attitude model (GAM) of satellites in on‐orbit environment, which includes missing attitude data and multi‐noise. The identified GAM and noise model are the basis of attitude control and state estimation on‐orbit.Design/methodology/approachTo cope with noises contaminating both input and output of attitude model, the errors‐in‐variables model is transformed into a traditional Box‐Jenkins model according to the attitude control loop. The wavelet denoising (WD) technique is helpful to predict the missing output data using the identified GAM.FindingsBy the numerical simulation, it is verified that the proposal accompanied with WD has a faster prediction capability than that of the algorithm without WD. As a result, the proposed approach is suitable to attitude model identification of on‐orbit satellites.Originality/valueThis identification algorithm can deal with two kinds of on‐orbit conditions and has a fast parameter convergent rate. Therefore, it has a practical application value in on‐orbit environment.

Total ballbar dynamic tests for five-axis CNC machine tools

The linear and rotary axes of a five-axis machine tool are driven simultaneously to generate a specified tool position and orientation in workpiece coordinates. It is crucial that these servo-controlled axes are of balanced dynamics to achieve high tracking accuracy. In this paper, ballbar circular tests for all possible combinations of linear and rotary axes of a five-axis machine tool are investigated and total ballbar dynamic tests are proposed. Through the relational arrangement of the test sequence, the total ballbar dynamic tests can be employed to identify dynamic differences between linear and rotary axes. More importantly, the velocity gains of the position control loops of all servo-controlled linear and rotary axes can be tuned synchronously to eliminate gain mismatch errors. Experimental results have proved the effectiveness of the new methods.

An Observer-Based Friction Compensation Technique for Positioning Control of a Pneumatic Servo System

This paper presents a technique to cope with undesirable frictional effects in positioning control of a pneumatic actuator. This technique is based on an observer for estimating the dynamically varying friction force on-line. The observer is derived from an available nonlinear observer for Coulomb friction by modifying it to fit the pneumatic actuator and to enhance its estimation ability. Our pneumatic servo system for positioning consists of an inner pressure control loop, an outer position control loop, the friction observer, and a velocity observer. In this system, the friction force is compensated by adjusting a desired pressure value sent from the outer loop to the inner loop according to the friction observer output. Experimental comparisons with a conventional control system using friction compensation by means of accelerometer information feedback were carried out and show that our system works with almost the same high positioning accuracy as the conventional system, despite having neither an accelerometer nor a velocity sensor, and is more advantageous from the perspective of cost performance.

Sensorless interior permanent magnet synchronous motor drive system with a wide adjustable speed range

The authors propose a novel extended flux estimating method for an interior permanent magnet synchronous motor. By using the proposed method, an extended flux can be systematically derived. Then, the shaft position and speed of the motor can be obtained. Starting from a standstill and at a low-speed range control, a current-slope estimating method is used to replace the extended flux method because the estimating extended flux decreases as the motor speed is reduced. By combining the extended flux and the current-slope estimating methods, the interior permanent magnet synchronous motor drive system can be controlled in a wide range with satisfactory performance. The adjustable speed range is from 1 to 2000 r/min. In addition, the system performs fast transient responses and good load-disturbance responses. Moreover, a sensorless position control system has been well developed based on the speed control drive system. A TMS 320LF2407 digital signal processor is used to execute the rotor position estimation, rotor speed estimation, current-loop control, speed-loop control and position-loop control algorithms. The hardware circuit therefore is very simple. Several experimental results are provided to validate the theoretical analysis.

Robust motion control of a clamp-cylinder for energy-saving injection moulding machines

This paper deals with the issue of robust motion control of a clamp-cylinder for injection moulding machines driven by a pair of speed-controlled fixed displacement pumps. As a fundamental step prior to tracking controller design, a feedback control system is suggested by implementing a position control loop in parallel with a system pressure control loop. A discrete-time sliding mode control scheme is developed for enhancing the tracking performance under inherent nonlinearities. Consequently, a significant reduction in tracking error is achieved for both position and pressure control applications.

Defect-detection methods in the position-control loop of numerically controlled machine tools

Defect-detection methods in the position-control loop of numerically controlled machine tools

Precision motion control of a three degrees-of-freedom hybrid stage with dual actuators

The author presents a three degrees-of-freedom precision hybrid stage that can move and align an object on it for the measurement of its three-dimensional image using the confocal scanning microscope. The hybrid stage consists of two individually operating x - y - thetas stages, called the coarse stage and the fine stage. The coarse stage is driven by the three linear motors and produces the initial movement of an object. On the other hand, the fine stage is driven by the four voice coil motors and provides the final alignment of it with sub-micron metre accuracy. For control of the hybrid stage, a precision motion controller is proposed. The precision motion controller consists of a position and velocity control loop, an anti-windup compensator to eliminate the windup problem that occurs in the controller, a generator of optimal force, a precision position determiner to determine the exact position of the fine stage and a perturbation observer to observe the perturbation of the fine stage and compensate it. The performances of the precision motion controller of the hybrid stage are evaluated by experiment with a hardware setup.

Contouring accuracy improvement using a tangential contouring controller with a fuzzy logic-based feedrate regulator

In contour-following tasks, contour error reduction is an issue of much concern. Generally speaking, contour error is caused by the mismatched dynamics between each axis. To reduce the contour error, many previous studies have focused on developing proper controllers and/or more accurate contour error estimation algorithms. An alternative method for reducing contour errors is to exploit the idea of desired feedrate adjustment. This paper proposes using the approximate contour error information to develop a fuzzy logic-based feedrate regulator, which adjusts the value of the desired feedrate. Moreover, to further reduce contour error, an integrated motion control scheme is also developed. This scheme consists of a position loop controller with velocity command feedforward, a tangential contouring controller (TCC), a real-time contour error estimator, and the proposed fuzzy logic-based feedrate regulator. Several experiments on free-form contour-following tasks are conducted to evaluate the performance of the proposed approach. The experimental results clearly demonstrate the effectiveness of the proposed approach.

A Flux-Density-Based Electromagnetic Servo System for Real-Time Magnetic Servoing/Tracking

The goal of this paper is to develop an electromagnetic servo system for two kinds of multiaxis motion control, namely magnetic servoing and magnetic tracking. Based on the proposed space vector expression that is a function of magnetic flux density for estimating the relative position from a magnet to a Hall probe, the magnetic servoing can achieve a contouring control with respect to a fixed magnet, and the magnetic tracking can track a moving magnet. The proposed flux-density-based feedback control is a fully closed-loop scheme, which involves an inner position control loop and an outer magnetic control loop. Experiments are presented to demonstrate the validity of the space vector expression in terms of flux density and the feasibility of the electromagnetic servo system using flux density feedback control.

Investigation on full distribution CNC system based on SERCOS bus

A full distribution CNC system based on SERCOS bus is studied in accordance with the limitations of traditional PC-based motion card. The conventional PC-based motion control card is dispersed into several autonomous intelligent servo-control units with the function of servo driver. The autonomous intelligent servo-control units realize the loop control of position, velocity and current. Interpolation computation is completed in PC and the computational results are transferred to every autonomous intelligent servo-control unit by high speed SERCOS bus. Software or hardware synchronization technology is used to ensure all servomotors are successive and synchronously running. The communication and synchronization technology of SERCOS are also researched and the autonomous intelligent servo-control card is developed byself. Finally, the experiment of circle contour process on a prototype system proves the feasibility.

Light-Intensity-Feedback-Waveform Generator Based on MEMS Variable Optical Attenuator

Increasing demands on the dynamical behavior of microelectromechanical systems (MEMS) devices are reaching a point where mechanical design by itself cannot provide further improvements. Alternative approaches based on control theory, such as the open-loop or the closed-loop driving strategies, must be used instead to provide further enhancements in device performance. In this paper, the design of a light-intensity control system for an optical waveform generator is presented. The optical waveform generator is based on the light-modulation ability of MEMS variable optical attenuators (VOA). The VOA is of shutter-insertion type driven by an electrostatic comb drive. The control system consists of an inner position-control loop and an outer light-intensity-control loop. The inner control loop improves the dynamic response of the position of the MEMS electrostatic comb actuator by using position feedback, whereas the outer feedback loop handles both light-intensity regulation and tracking. An experimental setup and a practical system characterization are given. Based on this, the feedback control system is implemented on an actual MEMS VOA. The results verify that the control system proposed in this paper does significantly improve both the accuracy and the dynamical behavior of the existing device.

Nonlinear position controller design with input–output linearisation technique for an interior permanent magnet synchronous motor control system

A novel, advanced position controller design for an interior permanent magnet synchronous motor control system is proposed. The input–output linearisation technique is used to transfer the system model into a linearised system model. Then, based on the linearised system model, an H∞ controller is designed to achieve robust performance of the position control system. To improve the system performance, a load estimator is used to compensate the external load and the influence of the parameter variations as well. In addition, a maximum torque/ampere control is applied to increase the output torque of the motor. A digital signal processor, TMS 320LF2407, is used to execute the speed-loop and position-loop control algorithms. As a result, the hardware circuit is quite simple. Several experimental results show that the proposed system has fast transient responses, good load disturbance rejection responses and good tracking responses.

Robust control of active magnetic suspension: Analytical and experimental results

A robust control of an active radial homopolar magnetic bearing system is considered in the paper. The robust control of a rigid rotor vibration is designed analytically and confirmed by experimental investigations. A digital signal processor (DSP) is used to implement the control algorithm and the position control loop is executed in real time. The stability of system with disturbance interaction is discussed. The success of the robust control is demonstrated through results of computer simulations. Finally, experimental results show the effectiveness of the control system as well as good initial responses/transient responses and robustness of the designed controller.

반작용 휠을 사용하는 인공위성의 내고장 자세제어기법

This paper considers a fault tolerant control problem for a spacecraft using reaction wheels. Faults are assumed to be inherent to only actuators(reaction wheels) and a control algorithm to accommodate actuators` faults is proposed. An attitude control loop includes an angular velocity control loop. The time delay control method is used to make a spacecraft follow the command angular velocity and to accommodate actuators` faults. A stability condition for the proposed algorithm is derived and the performance is demonstrated by computer simulations.

Position Control of an Interior Permanent-Magnet Synchronous Motor Without Using a Shaft Position Sensor

This paper proposes a novel sensorless position control system for an interior permanent-magnet synchronous motor. In this paper, a novel rotor position/velocity estimation technique is proposed. This estimation technique only relates to the slopes of the stator currents and does not relate to the parameters or operating conditions of the motor. Neither an extra circuit nor an external high-frequency exciting signal is required here as compared to other position estimation techniques. In addition, the proposed estimator works well in transient, steady-state, and standstill conditions. As a result, the proposed method is very robust and useful. To improve the performance of the position-control system, an optimal controller is proposed. By using this controller, a fast transient response, good load disturbance rejection capability, and satisfactory tracking ability can be achieved. A digital signal processor, TMS-320-LF-2407, is used to execute the rotor position/velocity estimation, the current-loop control, the velocity-loop control, and the position-loop control. As a result, a fully digital position-control system is achieved. Several experimental results validate the theoretical analysis.

Motion Controller Design for Contour-Following Tasks Based on Real-Time Contour Error Estimation

Reduction of contour error is an important issue in contour-following applications. One of the common approaches to this problem is to design a controller based on contour error information. However, for the free-form contour-following tasks, there is a lack of effective algorithms for calculating contour errors in real time. To deal with this problem, this paper proposes a real-time contour error estimation algorithm. In addition, a motion control scheme that combines a position loop controller (which utilizes a velocity command feedforward) with a tangential-contouring controller (TCC) is employed to improve the contour-following accuracy. When implementing the TCC, a coordinate transformation matrix is needed. Unfortunately, it is difficult to calculate the coordinate transformation matrix when performing the free-form contour-following task. To overcome this difficulty and facilitate the use of contour controllers, a systematic approach is employed to derive the coordinate transformation matrix for the free-form contour-following tasks. Experimental results demonstrate the effectiveness of the proposed contour error estimation algorithm and the motion control scheme