An Accurate Linearization of Electromagnetic Force of Heteropolar Magnetic Bearings With Redundant Structures

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Cheng Xin ◽  
Cheng Baixin ◽  
Liu Han ◽  
Allen G. M
Keyword(s):  
Current Distribution ◽  
Electromagnetic Force ◽  
High Performance ◽  
Fault Tolerant ◽  
Taylor Series Expansion ◽  
Magnetic Bearings ◽  
Optimization Approach ◽  
Rotor Position ◽  
Distribution Matrix ◽  
Emf Model

Abstract Fault tolerance is one of the practical and effective approaches to improve the reliability of magnetic bearings. The linearization of the electromagnetic force (EMF) from the redundant structures is the crucial basis of the design of a fault-tolerant controller. In this paper, we propose an accurate linearization approach for the heteropolar magnetic bearings with redundant structures by solving the Taylor series expansion equation of the current distribution matrix (W) in the nonequilibrium position and introducing a set of displacement compensation matrices to establish a unified accurate EMF model including the controlled current and rotor position. The proposed approach can effectively decrease the EMF error between the actual physical model and the linearized model compared with the existing methods for the consideration of the rotor position. Moreover, the solutions of the current distribution matrix and the relevant optimization approach have been presented on the basis of the proposed approach to help to design a high-performance fault-tolerant controller in the entire rotor displacement range. The numerical results demonstrated the noticeable accuracy advantages of the proposed EMF model.

Optimized Realization of Fault-Tolerant Heteropolar Magnetic Bearings

2000 ◽  
Vol 122 (3) ◽  
pp. 209-221 ◽  
Author(s):  
Uhn Joo Na ◽  
Alan Palazzolo
Keyword(s):  
Fault Tolerant ◽  
Load Capacity ◽  
Fault Tolerant Control ◽  
Optimization Method ◽  
Magnetic Bearing ◽  
Magnetic Bearings ◽  
Control Voltage ◽  
Distribution Matrix ◽  
Control Forces ◽  
Multiple Poles

Flux coupling in heteropolar magnetic bearings permits remaining active coils to assume actions of failed coils to produce force resultants identical to the un-failed actuator. This fault-tolerant control usually reduces load capacity because the redistribution of the magnetic flux which compensates for the failed coils leads to premature saturation in the stator or journal. A distribution matrix of voltages which consists of a redefined biasing voltage vector and two control voltage vectors can be optimized in a manner that reduces the peak flux density. An elegant optimization method using the Lagrange multiplier is presented in this paper. The linearized control forces can be realized up to certain combination of 5 poles failed for the 8 pole magnetic bearing. Position stiffness and voltage stiffness are calculated for the fault-tolerant magnetic bearings. Simulations show that fault-tolerant control of the multiple poles failed magnetic bearings with a horizontal flexible rotor can be achieved with reduced load capacity. [S0739-3717(00)01103-X]

The Fault-Tolerant Control of Magnetic Bearings With Reduced Controller Outputs

2000 ◽  
Vol 123 (2) ◽  
pp. 219-224 ◽  
Author(s):  
Uhn Joo Na ◽  
Alan Palazzolo
Keyword(s):  
Current Distribution ◽  
Fault Tolerant ◽  
Fault Tolerant Control ◽  
Industrial Applications ◽  
Magnetic Bearings ◽  
Necessary Condition ◽  
Control Scheme

The fault-tolerant control scheme utilizes grouping of currents to reduce the required number of controller outputs. Reduced current distribution matrices can be calculated with the constraint conditions of the controller outputs and the necessary condition for linearization. Decoupling chokes are not required for the control scheme with grouped currents since fluxes are isolated in C-cores. By reducing controller outputs and removing decoupling chokes the fault-tolerant control scheme is more efficient and practical in terms of industrial applications.

BISWSRBS: A Winograd-based CNN Accelerator with a Fine-grained Regular Sparsity Pattern and Mixed Precision Quantization

2021 ◽  
Vol 14 (4) ◽  
pp. 1-28
Author(s):  
Tao Yang ◽  
Zhezhi He ◽  
Tengchuan Kou ◽  
Qingzheng Li ◽  
Qi Han ◽  
...  
Keyword(s):  
High Performance ◽  
State Of The Art ◽  
The State ◽  
Optimization Approach ◽  
Quantization Scheme ◽  
Model Accuracy ◽  
Sparsity Pattern ◽  
Computing Platform ◽  
Energy Efficiency Improvement ◽  
Mixed Precision

Field-programmable Gate Array (FPGA) is a high-performance computing platform for Convolution Neural Networks (CNNs) inference. Winograd algorithm, weight pruning, and quantization are widely adopted to reduce the storage and arithmetic overhead of CNNs on FPGAs. Recent studies strive to prune the weights in the Winograd domain, however, resulting in irregular sparse patterns and leading to low parallelism and reduced utilization of resources. Besides, there are few works to discuss a suitable quantization scheme for Winograd. In this article, we propose a regular sparse pruning pattern in the Winograd-based CNN, namely, Sub-row-balanced Sparsity (SRBS) pattern, to overcome the challenge of the irregular sparse pattern. Then, we develop a two-step hardware co-optimization approach to improve the model accuracy using the SRBS pattern. Based on the pruned model, we implement a mixed precision quantization to further reduce the computational complexity of bit operations. Finally, we design an FPGA accelerator that takes both the advantage of the SRBS pattern to eliminate low-parallelism computation and the irregular memory accesses, as well as the mixed precision quantization to get a layer-wise bit width. Experimental results on VGG16/VGG-nagadomi with CIFAR-10 and ResNet-18/34/50 with ImageNet show up to 11.8×/8.67× and 8.17×/8.31×/10.6× speedup, 12.74×/9.19× and 8.75×/8.81×/11.1× energy efficiency improvement, respectively, compared with the state-of-the-art dense Winograd accelerator [20] with negligible loss of model accuracy. We also show that our design has 4.11× speedup compared with the state-of-the-art sparse Winograd accelerator [19] on VGG16.

Flow-Rate Observers in the Suppression of Compressor Surge Using Active Magnetic Bearings

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Se Young Yoon ◽  
Zongli Lin ◽  
Wei Jiang ◽  
Paul E. Allaire
Keyword(s):  
Flow Rate ◽  
High Performance ◽  
Flow Instability ◽  
Characteristic Curve ◽  
Estimation Method ◽  
Industrial Applications ◽  
Magnetic Bearings ◽  
Active Magnetic Bearings ◽  
Initiation Point ◽  
Surge Margin

Surge is a dynamic flow instability that can cause extensive damage to compressors and other components. One common challenge that many surge control methods in the literature face when implemented in industrial applications is the unavailability of the high performance actuators and accurate flow rate measurements that are required to suppress surge. In this paper we present the experimental results of employing active magnetic bearings in order to suppress the surge instability in a centrifugal compressor. In addition, we compare how the selection of the flow estimation method affects the effectiveness of the implemented surge suppression controller. The experimental data demonstrates that the best combination of controller and flow estimator tested in this work allows the compressor to operate deep into the former surge region when the controller is activated, moving the minimum flow rate at the surge initiation point by 21%. This allows the compression system to operate at the highest efficiency/pressure point in the characteristic curve, while still retaining a very conservative surge margin separating the allowed compressor operating region from the surge inception point even if unexpected system changes occur.

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