Search

Connecting a complex control system with various sensors, actuators, and controllers as a networked control system by a shared data network can effectively reduce complicated wiring connections. This system is also easy to install and maintain. The recent trend is to use networked control systems for time-sensitive applications, such as remote dc motor actuation control. The performance of a networked control system can be improved if the network can guarantee Quality-of-Service (QoS). Due to time-varying network traffic demands and disturbances, QoS requirements provided by a network may change. In this case, a network has to reallocate its resources and may not be able to provide QoS requirements to a networked control application as needed. Therefore, the application may have to gracefully degrade its performance and perform the task as best as possible with the provided network QoS. This paper proposes a novel approach for networked dc motor control systems using controller gain adaptation to compensate for the changes in QoS requirements. Numerical and experimental simulations, and prototyping, are presented to demonstrate the feasibility of the proposed adaptation scheme to handle network QoS variation in a control loop. The effective results show the promising future of the use of gain adaptation in networked control applications. Index Terms--Adaptive control, communication networks, control systems, dc motors, decentralized control, distributed control, real-time systems, stability.

A photovoltaic (PV) generator is a nonlinear device having insolation-dependent volt-ampere characteristics. Because of its relatively high cost, the system designer is interested in optimum matching of the motor and its mechanical load to the PV generator so that maximum power is obtained during the entire operating period. However, since the maximum-power point varies with solar insolation, it is difficult to achieve an optimum matching that is valid for all insolation levels. In this paper it is shown that for maximum power, the generator current must be directly proportional to insolation. This remarkable property is utilized to achieve insolation-independent optimum matching. A shunt dc motor driving a centrifugal water pump is supplied from a PV generator via a step-up converter whose duty ratio is controlled using a current-locked feedback loop.

This paper contains a comparison between actual laboratory-measured performance of a brushless dc motor drive system, with skewed permanent magnet mounts on its rotor, and two computer-simulated motor drive system performance characteristics. These simulated motor drive system performance results were once obtained using motor parameters computed from rigorous three dimensional-finite element (3D-FE) magnetic field solutions detailed in two companion papers, and once obtained using motor parameters from more conventional 2D-FE magnetic field solutions. The comparison demonstrates that 3D-FE based motor parameters lead to drive system performance simulations which are much closer to test results for this type of brushless dc drives with skewed permanent magnet mounts. Torque ripples computed from 3D-FE based and 2D-FE based motor parameters are also included. The results clearly show advantages to basing the drive system simulations on 3D-FE computed motor parameters.

The coupled magnetic vector potential - magnetic scalar potential (CMVP-MSP) method of computation of 3D magnetic fields by finite elements (3D-FE), whose theoretical development and formulation were detailed in a companion paper together with 3D-FE grid developments, is applied here to a brushless dc motor with skewed permanent magnet mounts on its rotor. Results of the CMVP-MSP and 3D-FE computation of the magnetic field and associated motor parameters (emfs and armature inductances) are detailed in this paper. These results demonstrate vividly the three dimensional nature of the computed flux distributions, caused by the torque ripple reduction design employing skewed magnet mounts on the rotor. Experimental evidence supporting the validity of the 3D-FE field computations, through comparison between computed and measured armature emf waveforms is also provided in this paper.

A three dimensional finite element (3D-FE) method for the computation of global distributions of 3D magnetic fields in electric machines containing permanent magnets is presented. The formulation of this 3D-FE method including 3D permanent magnet modeling, which is based on a coupled magnetic vector potential - magnetic scalar potential (CMVP-MSP) approach, is given. The development of the necessary 3D-FE grids and algorithms for the application of the method to an example brushless dc motor, whose field is three dimensional due to the skewed permanent magnet mounts on its rotor, is also given here. A complete set of results of application of the method to the computation of the global 3D field distributions and associated motor parameters under no-load and load conditions are detailed in a companion paper.

A new pulsewidth-modulated zero-voltage-switching quasi-resonant boost converter operating at constant switching frequency is presented. In contrast to the frequency-modulated zero-voltage-switching quasi-resonant boost converter, this converter possesses better controllability and higher operating performance, and overcomes the instability caused by the parasitic oscillation. The principle of operation and performance of the converter are presented. Its two-dimensional state trajectories and steady-state characteristic curves are derived which are useful for the converter design. Both the SPICE simulation and experimental result agree with the theoretical prediction.

The pole-teeth-winding configuration in brushless dc motors determines torque and unbalanced magnetic force which are the resultants of the tangential and the normal magnetic force in a small air gap, respectively. This paper calculated torque and unbalanced magnetic force using FEM, Maxwell stress tensor to investigate the influence of pole-teeth-winding patterns on the performance from two common designs, i.e. the rotational symmetric 12-pole 9-tooth (12P9S) motor and the rotational unsymmetric 8-pole 9-tooth (8P9S) motor, and proposed the rotational unsymmetric 10-pole 9-tooth (10P9S) motor which achieves the high average torque of 12P9S motor and the low cogging torque of 8P9S at the same time. The analyses show that 8P9S and 10P9S motor tend to have less cogging torque because their bigger values of the least common multiple of pole and teeth reduce the cogging torque. The torque efficiency depends on pole-teeth-winding configuration. ABC-winding of 12P9S motor and three consecutive teeth winding of 10P9S motor utilize all six energized coil effectively to produce the high average torque. The normal magnetic force in a rotational unsymmetric design is not balanced and results in unbalanced magnetic force.

A brushless dc motor for air-conditioned fan is studied by using finite element method in order to identify the noise source. The results have shown that acoustic resonance is more dominant than structural resonance.