Slip Gain Research Articles

Adaptation of Slip Gain for Modified Transient Vector Estimator-Based Speed Control of Induction Machine Drive

Modified transient vector estimator (MTVE) based speed control scheme that combines the high transient-performance features of rotor field oriented control with the robustness features of scalar control is presented in literature. However, MTVE scheme involves the calculation of slip gain to obtain torque reference. Either inaccurate estimation or variation in the estimated slip gain can result in the degradation of performance of MTVE control. In order to overcome this problem, this paper proposes a slip gain adaptation scheme, that is independent of speed of operation. The proposed method uses d-axis component of stator voltage to obtain expression for disorientation factor and works by matching all the control side variables with that of actual machine variables, and uses a simple PI controller to implement slip gain adaptation. The impact of inaccurate slip gain estimate on the dq-components of various currents, voltages, feed-forward components, and hence on the torque and flux of the machine are analyzed in this paper. The proposed adaptation scheme is suitable for wide speed range operation, in contrast to the existing slip gain adaptation methods, where open loop gain is dependent on the synchronous frequency information. The proposed adaptation scheme is validated using detailed simulation and experimental results. Comparison of the proposed adaptation method with the existing methods is also presented in this paper.

Detuning Minimization of Induction Motor Drive System for Alternative Energy Vehicles

This paper evaluates different types of AC machines and various control techniques for their suitability for the drive system of Alternative Energy Vehicles (AEV). An Indirect Field Oriented (IFO) drive system for the AEV application is chosen and its major problem of detuning is addressed by designing an offline and an online rotor resistance adaptation technique. The offline scheme sets the slip gain at various operating conditions based on the fact that if the rotor resistance is set correctly and field orientation is achieved, then there should be a linear relationship between the torque current and the output torque. The online technique is designed using Model Reference Adaptive System (MRAS) for the rotor resistance adaptation. For an ideal field oriented machine, the rotor flux along the q-axis should be zero. This condition acts as a reference model for the proposed MRAS scheme. The current model flux observer in the synchronous frame of reference is selected as an adjustable model and its rotor resistance is tuned so that the flux along the q-axis becomes zero. The effectiveness of the offline tuning scheme is evident through performance validation of the drive system, which is implemented in a real Ford vehicle. The experimental results obtained while driving the test vehicle are included in the paper while the proposed online scheme is validated on a 3.75 kW prototype induction motor.

Research on Mechanical Property of Top Drive Casing Running Tool’s Slips

Top drive casing running tool, because of its convenience, speed and safety, has been widely received by the research enterprises of petroleum mechanism and instrument. Now, there have been developed several kinds of casing running tools which have gradually been used by the drilling corporation at home and abroad. The slips system’s parameters, such as the axial thrust, slips length, teeth form, teeth interval, etc., directly affect the performance and safety of casing running tools. Those have no reports about correlative theoretical investigation results. Here, we found the mechanical analysis model between slip and casing and gain the minimum primitive axis thrust of slips. Then the minimum teeth interval of the slips is deduced by contact mechanics. And then the slips available working length is worked out through the shell theory and empirical formulas. Finally, based on finite element method, we obtain tooth form angles’ recommendable range by studying the tooth form. This study supplies theoretical basis to structural design of slips system of the top drive casing running tool.

Performance Analysis of Field Oriented Induction Motor using Fuzzy PI and Fuzzy Logic based Model Reference Adaptive Control

This paper presents the dynamic performances of an indirect vector controlled induction motor (IVCIM) using a fuzzy logic (FL) based model reference adaptive control (MRAC) slip gain tuner for speed regulation in the drive. In high performance AC drives the motor speed should closely match with the specified reference speed irrespective of the variations in the load, motor parameters and model uncertainties. Two fuzzy controllers combined with MRAC reactive power and stator direct axis (d-axis) voltage estimator have been used to tune the slip gain of the IVCIM drive against parameter variations and model uncertainties. An integrated mathematical model of the control scheme has been developed and simulated in MATLAB for Indirect vector control of an Induction motor. The simulated performances of the FL-MRAC slip gain tuner based IVCIM drive is compared to fuzzy PI controller. The simulated results in different dynamic operating conditions such as sudden change in command speed, step change in load, etc are demonstrated through necessary waveforms. The comparison of simulated results show that the fuzzy logic MRAC slip gain tuner based IVCIM drive is more robust and effective in minimizing the detuning effect in the drive due to parameter variations and model uncertainties.

Slip-gain estimation in field-orientation-controlled induction machines using the system transient response

Field-oriented control of induction machines is well established and widely used in applications where high-bandwidth torque control of ac machines is needed. A key parameter in the implementation of indirect field orientation is the slip gain (inverse of the rotor time constant), which is used to estimate the rotor flux angle. A new method for estimating the slip gain is presented in this paper. The method uses the transient response of the stator voltages following a change torque for these purposes. The method is independent of any machine or system parameter and can be easily integrated into standard drives and used in many industrial applications.

Induction motor dynamic and static inductance identification using a broadband excitation technique

The performance of indirect vector control depends upon accurate prediction of the motor slip angular frequency (/spl omega//sub s/) for the demand torque. The required slip gain depends upon the rotor time constant of the motor (T/sub r/). This value varies significantly over the operating temperature range and saturation level of a typical motor. This variation, if not compensated for, results in a significant degradation in torque production from a vector control system. The saturation effect can be compensated by an adaptive flux model if precise knowledge of the induction motor magnetizing curve is available. The aim of this paper is to present the application of an advanced system identification methodology enabling the off-line estimation of the magnetizing curve (dynamic and static inductance) of induction motors.

Indirect field-oriented induction motor drive with fuzzy detuning correction and efficiency optimisation controls

The detuning correction and efficiency optimisation of an indirect field-oriented induction motor drive for achieving higher efficiency and better field-orientation characteristic are presented. First, the operating characteristics of an indirect field-oriented motor drive under detuned condition are studied. A fuzzy controller is used to tune the slip gain online in the field-orientation mechanism to obtain a better decoupling control characteristic. At heavy loads the rated flux of the motor is set to increase its torque generating capability. The determination of the stator flux current component for obtaining rated flux is suggested. At light loads, with the motor running at steady state, in addition to fuzzy slip gain adaptation another fuzzy controller is used to reduce the stator flux current component from its rated value to minimise the stator input current and thus improve the efficiency of the motor drive. As the transient due to command or load torque change occurs the current adjustment action is temporary inhibited and the rated flux component current is set instead to obtain higher torque generating capability. Measured results show that both the efficiency and rotor speed dynamic responses are improved by the proposed fuzzy detuning correction control and efficiency optimisation control approaches.

SLIP GAIN TUNING IN INDIRECT FIELD ORIENTED CONTROL DRIVES

ABSTRACT The paper presents a simple technique for correctly and fastly tuning the slip gain in Indirect Field Oriented Control drives. To this aim no other transducers than the tachogenerator, usually included in such drives, are needed, as the tuning operation is performed by processing the effects of a suitable test signal injected in the system. The proposed approach can be used either for on-line retuning of working drives, either for the initial tuning of new installed drives. Simulation and experimental tests show that the procedure is effective and does not Interfere with normal operations of the drive.

A new slip gain adaptation algorithm for indirect field-oriented drive systems

The performance of the indirect field-oriented control using the slip frequency depends heavily on the accuracy of the induction machine parameters. It has been shown that the changes in rotor resistance have a dominant effect on the machine performance. An important requirement for obtaining good performance is to find the real machine parameters in the field-oriented controller. A slip gain adjustment algorithm for the field-oriented control proposed is simple and does not need any additional circuitry. It has been shown through the digital simulation that the correct slip frequency can be obtained at any machine parameter deviations by almost one adaptation. >

An automated rotor time-constant measurement system for indirect field-oriented drives

An automated scheme to measure the open-circuit rotor time constant and set the slip gain of a field-oriented controller is presented. The test utilizes the pulse-width-modulated inverter of the drive itself and is conducted at zero speed so that the result can be used for automated calibration of the slip gain in the controller of an indirect field-oriented drive system. The accuracy of the test is verified by a simple measurement that checks for the existence of a linear relation between the input torque command and output torque at steady state.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>