Vibration control of two-mass system with low inertia ratio considering practical use

In some industrial motor-drive systems, a torsional vibration is often generated because of an elastic element in torque transmission. Such a mechanical system is modeled as a two-mass system and it is well-known that the suppressing vibration of a low inertia ratio two-mass system where the motor inertia is larger than the load inertia is very difficult. This paper proposes a speed control system of a low-inertia ratio system, taking into account not only the dynamic responses but also a robust stability. The proposed control system is based on the H^∞ control theory and the resonance ratio control due to the feedback of the estimated shaft torque. Combining the H^∞ controller with the resonance ratio controller, the control system with high robust stability can be obtained comparing with the conventional resonance ratio control. The variable feedback gain system and the construction of the disturbance observer are discussed in order to reject the effects of noise. The simulated and experimental results show that the proposed speed control system is useful for the two-mass system with low inertia ratio. ©1998 Scripta Technica, Electr Eng Jpn, 125(2): 1–9, 1998     

Active vibration control of a motor system by using H∞ control theory

This paper considers the vibration control of a motor system which has a motor and a load connected with a flexible shaft. However, this system often generates a shaft torsional vibration. Traditional methods of treating this problem to adjust the PID controller so that the closed-loop frequency response is slower than that of the vibration mode. On the other hand, one method has already been proposed in which the vibration is suppressed by a disturbance observer. This paper proposes a new approach based on H_∞ control theory. For comparison, a PI control system based on classical control theory also is constructed. The results of several experiments show that compared with the PI control system, the H_∞ control system is effective in suppressing the vibration. Further, the H_∞ controller obtained in the study consists of a PI controller and a series compensator that functions as an active vibration controller.     

Speed control system and design of resonant system with disturbance observer

In industrial motor drive systems such as industrial plants and industrial robots, a torsional vibration often is generated because of the elastic elements in torque transmission. This vibration makes it difficult to achieve quick responses of speed and may result in damage to the plant. Such systems simply are modeled as a two mass system. The shaft torque feedback system with the disturbance observer, which is called “resonance ratio control,” is proposed to suppress the vibration for the two-mass system. In this paper, the design of controller gains in the shaft torque feedback system is examined considering not only the control performance such as the vibration suppression and dynamic responses, but also the robust stability against the noise and the model uncertainties. This paper shows the validity of the control system and the examinations by several experiments.     

Measurement of mechanical parameters in two-mass resonant system using disturbance observer

In application fields for two-mass resonant system, control theory-based various techniques that use feed-forward/feedback control have been proposed to achieve high performance motion control. Although these schemes effectively suppress resonant vibration, they are quite sensitive to system parameters because the design of such controllers basically relies on system mechanical parameters. This paper presents a disturbance observer-based novel mechanical parameter measurement scheme for a two-mass resonant system. In the proposed measurement, load inertia and torsional constant of the resonant system can be measured by using error components of the estimated disturbance torque due to setting errors of the parameters in the observer. With this measurement algorithm no additional tool other than the observer is required for parameter measurement. The effectiveness of the proposed measurement scheme is verified by experimental results that are obtained by a prototype. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 19–29, 1997     

Balancing control for dispersed generators considering torsional torque suppression and AVR performance for synchronous generators

Electric utility deregulation enabled PPSs (Power Producers and Suppliers) to enter the electricity market. PPSs are supposed to achieve 30‐minute balancing control for stable power supply of electric power. In addition, load rejection and instantaneous voltage drops greatly affect turbine shafting, that is, torsional torque oscillation. Therefore, PPSs must consider a reduction of torsional torque in order to prevent generator shaft damage. This paper proposes a control system which allows the achievement of both 30‐minute balancing control and reduction of torsional torque by using an H_∞ controller. The effectiveness of the proposed controller is validated by using MATLAB. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 16–25, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20868     

Suppression control of speed variation in an induction motor with fluctuating load by repetitive learning control

Induction motors are robust and inexpensive machines and are used widely for variable speed control because of the recent development of electronic technique. In the case where loads of the motors are compressors, pumps, and so on, the constant V/F control of the induction motors usually is employed because it is difficult to install speed sensors and accurate speed control is not required. In such loads, the rotational speed of the motors fluctuates considerably because the load torque is pulsated. When the frequency of the torque pulsation is close to the resonant frequency of the mechanical system, large vibration and acoustic noise are produced especially in the low-frequency region. This paper proposes a method to suppress the variation of the rotational speed of the V/F controlled induction motor with a fluctuated load by feedforward compensation using a timing sensor of 1 pulse/rev, considering that the load torque varies periodically. The feedforward data by a period for the compensation is obtained by the learning control based on the repetitive control in which the motor speed is controlled by periodically reflecting the past speed error on the present V/F input to the inverter. Effectiveness of the proposed method is confirmed by approximate analysis, simulations and experiments.     

Motion of control of a multijoint robot based on a robust velocity controller

This paper proposes a simple and robust robot motion control method using a robust velocity controller. The robust velocity controller is based on H^∞ control theory, and is called H^∞ velocity controller. The H^∞ velocity controller based motion control method is completely equivalent to the robust acceleration control method using the H^∞ acceleration controller, but it has simpler structure. Therefore, the proposed system can realize a fine robot motion control easily. To confirm the validity of the proposed method, this paper realizes the hybrid control of position and force for a multijoint robot manipulator. Further, the simple realization of hybrid control is proposed considering the attitude of the robot manipulator. This system achieves hybrid control of position and force of the robot manipulator while maintaining a perpendicular attitude to the target environment. The experimental results in this paper show that the proposed system has the desired force and position response to the target environment. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (4): 58–69, 1997     

Stabilization control for multimachine system using decentralized H∞ excitation controller realizing terminal voltage control and damping control

In this paper, to achieve both damping of power system oscillation and terminal voltage control simultaneously on a multimachine power system, we propose a decentralized H_∞ excitation controller. In the proposed method, H_∞ control via the Normalized Coprime Factorization approach is used to achieve the proposed design idea. By the Normalized Coprime Factorization approach, the weighting function in H_∞ control design is simplified, and output feedback controllers that take into account the realities and constraints of the power systems are designed. The proposed controller is subjected to model reduction of H_∞ controllers, and is transformed to a discrete system to perform digital control by computer systems in consideration of application to a real system. We verify that the proposed excitation controller can achieve both damping of power system oscillation and terminal voltage control by computer simulations of a multimachine power system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 33–41, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10254     

A design method of digital robust speed servo system considering output saturation

When a robust servo system having an integral element has a large error input, it often reveals windup phenomena caused by output saturation. It is very difficult for a strictly proper and high‐order controller to avoid having windup phenomena caused by output saturation. This paper newly proposes the digital robust speed servo system with a complete algorithm for consideration of output saturation. The proposed algorithm completely considers the output saturation of a robust speed controller connected to a PI current controller in series. Moreover, this method can be applied to both a PI speed controller and an H^∞ speed controller. The experimental results show that a robust speed servo system using the proposed algorithm has a good and stable response for a large step speed command. © 2000 Scripta Technica, Electr Eng Jpn, 132(3): 68–78, 2000     

Design and implementation of anti-windup controller based on stated feedback H∞ control theory

In the control of an actual plant, there commonly exists a constraint on the control input caused by mechanical constraint on the actuator or in order to protect the plant. This constraint usually exerts an adverse effect on control performance, called windup phenomenon. Anti-windup technique is known as one of the most effective techniques to prevent such windup phenomenon. In this paper, we propose a new design of anti-windup controller based on state feedback H^∞ control theory. This design consists of representation of an anti-windup controller that includes a free parameter, and decision of the free parameter by using state feedback H^∞ control theory. We also discuss the problem on discretization of an anti-windup controller in implementation. In a numerical case study, we demonstrate the performance of the proposed anti-windup controller by computer simulation. © 1998 Scripta Technica, Electr Eng Jpn, 124(1): 33–41, 1998     

A force‐reflecting friction‐free bilateral system based on a twin drive control system with torsional vibration suppression

This paper proposes a new friction‐free bilateral system based on twin drive control system considering resonant frequency for bilateral systems. The twin drive system consists of two motors which are coupled by the differential gear. The output torque becomes a different torque of both motors. The nonlinear friction torque of the twin drive system can be easily compensated. However, the resonant frequency and the antiresonant frequency caused by the tensional vibration exist. This paper proposes a new two‐mass model of twin drive system that supresses torsional vibration by state feedback. The proposed control method is applied to the bilateral robot, and the effectiveness of the control method is confirmed by the experimental results. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 72–79, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20355     

有机械联系的多电机传动系统的负荷均衡控制和扭振抑制

存在两类有机械联系的多电机传动负荷均衡控制系统,经转矩环系统和经转速环系统,主要差别在于对由弹性和间隙引起的扭振抑制能力不同,研究了扭振产生机理,抑制方法,在什么情况下宜选用哪类系统,帮助系统设计者正确选用。还介绍了一种抑制扭振的有效措施——转速差补偿,两类系统都适用。分析结果已在工业产品中得到应用。     

Robust Sliding Mode Speed Controller-based Model Reference Adaptive System (MRAS) and Load Torque Estimator for Interior Permanent Magnet Synchronous Motor (IPMSM) Drives

This paper presents a robust sliding mode control (SMC)-based model reference adaptive system (MRAS) aimed at improving the dynamic performance of interior permanent magnet synchronous motor (IPMSM) drives. MRAS following a speed controller for IPMSM drives is developed. The error signal between the plant speed and MRAS speed is augmented to permit the prescribed specifications be maintained using SMC. The load disturbance is detected using a load torque estimator and is compensated through the q-axis current reference value. The load torque estimator is used to provide a feedforward value in the speed controller in order to decouple the load torque from the speed control. This method can improve IPMSM dynamic performance against the disturbance torque without increasing SMC gain due to both chattering and stability limitations. The complete field-oriented control of an IPMSM drive with the proposed controller is successfully implemented in real time using the DSP-DS1102 control board for a laboratory 1-hp motor. A performance comparison of the proposed controller with the conventional PI controller is also provided. The efficacy of the proposed controller is verified by simulation and experimentation under different operating conditions. It is found that the proposed controller provides an excellent speed response under load torque disturbance and parameter uncertainty.     

Adaptive tracking control design of constrained robot systems

Both dynamic state feedback as well as output feedback tracking control designs are presented in this paper for constrained robot systems under parametric uncertainties and external disturbances. The previous studies on tracking control design, not considering the velocity measurements, address only the unconstrained robot design. In contrast, a dynamic output feedback controller based on a linear and reduced-order observer that uses only position measurements is proposed here for the first time to treat the trajectory tracking control problem of constrained robot systems. Both adaptive state feedback control schemes and adaptive output feedback control schemes with a guaranteed H^∞ performance are constructed. It is shown that all the variables of the closed-loop system are bounded and a pre-assigned H^∞ tracking performance is achieved, in the sense that the influence of external disturbance on the tracking motion error can be attenuated to any specified level. Moreover, it is also shown that the motion and force trajectories asymptotically converge to the desired ones as the dynamic model of robot systems is well-known and the external disturbance is neglected. Finally, simulation examples are presented to illustrate the tracking performance of a two-link robotic manipulator with a circular path constraint by the proposed control algorithms. © 1998 John Wiley & Sons, Ltd.     

Decentralized load frequency based on H∞ control

This paper presents a decentralized load frequency control (LFC) based on H_∞ optimal control theory with an observer. A few LFC schemes have been proposed based on the optimal control theory, but they have not considered the change of system parameters in operation and the characteristics of load disturbances in a target system. In this paper, H_∞ robust control is introduced to address such problems. Owing to its practical merit, the proposed control scheme is a decentralized LFC. Employing observer theory, the proposed method requires only frequency and tie‐line power deviation in each area. Numerical simulations are shown to demonstrate the effectiveness of the proposed method. H_∞ control was proven to show greater effectiveness of damping disturbance over the conventional optimal control by the design of control systems aimed at restricting the H_∞ norm of its transfer function. In particular, when a decentralized LFC is applied, by reducing the system size, H_∞ norm is easier to dampen; thus H_∞ control is more effective in the decentralized control. Future research topics include the design of H_∞ control system with a weight on frequency response. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 28–38, 2001     

ACO based speed control of SRM fed by photovoltaic system

This paper proposes a speed control of Switched Reluctance Motor (SRM) supplied by Photovoltaic (PV) system. The proposed design of the speed controller is formulated as an optimization problem. Ant Colony Optimization (ACO) algorithm is employed to search for the optimal Proportional Integral (PI) parameters of the proposed controller by minimizing the time domain objective function. The behavior of the proposed ACO has been estimated with the behavior of Genetic Algorithm (GA) in order to prove the superior efficiency of the proposed ACO in tuning PI controller over GA. Also, the behavior of the proposed controller has been estimated with respect to the change of load torque, variable reference speed, ambient temperature, and radiation. Simulation results confirm the better behavior of the optimized PI controller based on ACO compared with optimized PI controller based on GA over a wide range of operating conditions.     

Evaluation of torsional oscillations in paper machine sections

Torsional oscillations greatly affect performance and determine the bandwidth (BW) and damping of speed loops. Backlash due to gear reducers can also contribute to the triggering of oscillations, especially when the drive runs at very low load torque. This paper presents a detailed evaluation of these effects in typical electromechanical drive trains applied to paper machine sections. The cases evaluated consider torsional oscillations in two-mass and three-mass systems, and the effect of shaft diameter and length on the resonant frequencies of three typical paper machine sections. Time-domain response plots are evaluated to show the effect of speed response overshoot, reducer backlash, and step or ramp speed commands. Based on these results, mechanical design guidelines are given for the most significant drive train components in order to minimize torsional oscillations of the speed-controlled drive system.     

Adaptive robust H∞ state feedback control for linear uncertain systems with time‐varying delay

This paper considers the problem of adaptive robust H_∞ state feedback control for linear uncertain systems with time‐varying delay. The uncertainties are assumed to be time varying, unknown, but bounded. A new adaptive robust H_∞ controller is presented, whose gains are updating automatically according to the online estimates of uncertain parameters. By combining an indirect adaptive control method and a linear matrix inequality method, sufficient conditions with less conservativeness than those of the corresponding controller with fixed gains are given to guarantee robust asymptotic stability and H_∞ performance of the closed‐loop systems. A numerical example and its simulation results are given to demonstrate the effectiveness and the benefits of the proposed method. Copyright © 2008 John Wiley & Sons, Ltd.     

Artificial intelligence-based speed control of DTC induction motor drives—A comparative study

The design of the speed controller greatly affects the performance of an electric drive. A common strategy to control an induction machine is to use direct torque control combined with a PI speed controller. These schemes require proper and continuous tuning and therefore adaptive controllers are proposed to replace conventional PI controllers to improve the drive's performance. This paper presents a comparison between four different speed controller design strategies based on artificial intelligence techniques; two are based on tuning of conventional PI controllers, the third makes use of a fuzzy logic controller and the last is based on hybrid fuzzy sliding mode control theory. To provide a numerical comparison between different controllers, a performance index based on speed error is assigned. All methods are applied to the direct torque control scheme and each control strategy has been tested for its robustness and disturbance rejection ability.     

Smart bacterial foraging algorithm based controller for speed control of switched reluctance motor drives

In this paper, a innovative methodology for Switched Reluctance Motor (SRM) drive control using Smart Bacterial Foraging Algorithm (SBFA) is presented. This method mimics the chemotactic behavior of the E. Coli bacteria for optimization. The proposed algorithm uses individual and social intelligences, so that it can search responses among local optimums of the problem adaptively. This method is used to tune the coefficients of a conventional Proportion–Integration (PI) speed controller for SRM drives with consideration of torque ripple reduction. This matter is done by applying the proposed algorithm to a multi-objective function including both speed error and torque ripple. This drive is implemented using a DSP-based (TMS320F2812) for an 8/6, 4-kW SRM. The simulation and experimental results confirm the improved performance of adjusted PI controller using SBFA in comparison with adjusted PI controller using standard BFA. Excellent dynamic performance, reduced torque ripple and current oscillation can be achieved when the coefficients of PI controller are optimized by using SBFA.