Praveen Kumar Agarwal

Fault-tolerant control of three-pole active magnetic bearing

Active magnetic bearings have many advantages over conventional bearings due to contactless operation and adjustable force dynamics. However, one of the obstacles associated with these bearings is failure modes, which may result in destructive rotor dynamic behaviour. One of the important failure modes is electric power outage which may be due to failure of power amplifier, coil or electric wiring. In the present work, a fault tolerant controller has been designed for three-pole magnetic bearings to provide unaltered performance in the event of fault occurrence. The controller has been designed by incorporating the nonlinear fuzzy logic control. The present design of fuzzy logic controller is done by reducing the number of rules of its rule base. Simulations have been carried out to test the performance of the controller for different failure conditions. The designed controller is able to stabilize the rotor for large deviations from the origin even in the presence of failure. The controller is found to be robust as it provides satisfactory operation in the presence of uncertainties.

Neural networks and fuzzy logic-based spark advance control of SI engines

Research highlights? A combined neural network and fuzzy logic-based control scheme is designed for SA control. ? The controller is designed to maintain LPP of SI engine close to 160 ATDC. ? The controller works in conjunction with RNN model for cylinder pressure identification. ? The controller gives desired performance and is found to be robust. In SI engines, spark advance (SA) needs to be controlled to get Maximum Brake Torque (MBT) timing. Spark advance can be controlled either by open loop or by closed loop controller. The open loop controller requires extensive testing and calibration of engine, to develop look up tables. In closed loop controller, empirical rules relating variables deduced from cylinder pressure are used. One of such empirical rules is to fix location of peak pressure (LPP) at a desired value of the crank angle. In the present work, a combined neural network and fuzzy logic-based control scheme is designed for SA control to get MBT timing. The fuzzy logic controller is designed to maintain LPP of SI engine close to 16? ATDC. The controller works in conjunction with Recurrent Neural Network model for cylinder pressure identification. LPP is estimated from cylinder pressure curve reconstructed using neural network model and is used as feedback signal to fuzzy logic controller. The simulations have been carried out to test the performance of the combined neural network and fuzzy logic-based control strategy. The simulation results show that the proposed strategy can quite satisfactorily control LPP to its desired value.

Fuzzy logic control of three-pole active magnetic bearing system

Active magnetic bearings have many advantages over conventional bearings due to non-contact operation and adjustable force dynamics. The major disadvantage of magnetic bearings is its cost. In the present work, a three-pole magnetic bearing has been considered which helps in reducing the cost by having the minimum number of poles. The power loss is minimised by determining the optimum bias currents for different pole orientations. However, the strongly non-linear nature of three-pole magnetic bearing due to flux coupling necessitates the application of non-linear control techniques for its controller design. A fuzzy logic controller has been designed for the stable operation of magnetic bearing. The present design of fuzzy logic controller is done by reducing the number of rules of its rule-base. The provision for mass unbalance compensation has also been provided by combining the fuzzy logic approach with iterative learning control (ILC) approach. Simulations have been carried out to test the performance of the controller for different initial conditions. The designed controller is able to stabilise the rotor even for large deviations from the origin. The controller is found to be robust as it provides satisfactory operation in the presence of uncertainties in the magnetic bearing system.

Design of compact active magnetic bearing with higher load carrying capacity

Active magnetic bearings (AMB) are suitable for high speed applications because of their contactless operation. In many vital applications compact magnetic bearings with higher load carrying capacity are required for better utilization of available space, material and also for efficient operation. Hence in this present work efforts are made to design the AMB to achieve higher load carrying capacity and compact size. Two basic design parameters like number of poles and pole winding pattern are considered and their effect on the load carrying capacity and size of the AMB is presented. Eight-pole AMB of symmetric configuration with trapezoidal winding pattern has given the compact size with higher load carrying capacity.

Type-2 fuzzy logic controller for conical AMB-rotor system

In the present work, the design of controller for complete support of a rotor by Conical Active Magnetic Bearings (AMBs) is presented. These bearings eliminate the requirement of an axial AMB which results in reduction of cost and required mounting space. The presented controller is designed with the aim to reduce the requirement of exact system modelling. Fuzzy logic controller (FLC) satisfies this requirement since it can be designed by the knowledge of system behaviour or performance. However, the determination of different parameters of FLC is based on the designer knowledge and experience about the operational characteristics of the system. In the present work, efforts are made to enhance the system performance by designing the Interval Type-2 fuzzy logic controller (IT2FLC) with uncertain bound algorithm. This structure is better suited for handling parameters uncertainty. The simulations are carried out and performance of the designed controller is validated by comparing it with that of normal FLC.

Comparative analysis of conical and conventional active magnetic bearings for complete support of a 5-dof rotor system

Conical Active Magnetic Bearings (AMBs) eliminate the requirement of axial bearing for complete support of a 5-dof rotor system. In the present work, the design of conical AMB for a 5-dof rotor system is presented. A comparative analysis between conical and conventional AMB structure is done on the basis of maximum outer diameter, maximum current, maximum load capacity and power losses. Magnetic Path Reluctance (MPR) is also considered during the analysis and its effect on various design and operating parameters is analysed. It is found that MPR affects the maximum current and copper loss significantly. The conical design saves the axial space approx. by 37% with 8% reduced magnetic material volume. Maximum current requirement gets reduced for same load capacity and it leads to the reduction in copper loss.