Magnetic suspension systems with digital controllers

Carmichael, Alessandra; Hinchliffe, S.; Murgatroyd, Paul; Williams, Ian D.

doi:10.1063/1.1138539

Cited by 21 publications

(3 citation statements)

References 3 publications

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“…) and the PWM frequency ( ) are two crucial parameters for the dynamic performance of the high-speed PEMS transportation system, e.g., the disturbance rejection and the gap tracking 15 . In the literature, is usually set from 75 Hz to 2 kHz 12, [16][17][18] for the digital controller, whereas is usually set from 10 kHz to 20 kHz 3,[11][12][13] . Generally, is at least 5-time smaller than .…”

Section: Introductionmentioning

confidence: 99%

Zero-Power PEMS System with Full-Bridge PWM Inverter: from Mechanism to Algorithm

2021

Preprint

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The permanent-electro magnetic suspension (PEMS) technology takes advantage of the attractive magnetic force between the magnet and the iron core and reduces the power consumption eventually to zero. However, the current of the zero-power PEMS system fluctuates around zero due to disturbances and suffers from the electronic nonlinearity. This work presents that the 2 µs turn-off delay (one electronic defect) of the integrated circuit (IC) L298N (one commercial full-bridge pulse-width-modulation (PWM) inverter produced by STMicroelectronics) leads to the nonlinear current-duty cycle characteristic, which undermines the control stability and limits the PWM frequency of the zero-power PEMS system. Moreover, the nonlinear mechanism is experimentally and theoretically analyzed for the critical PWM frequency and the sensitivity transition. Furthermore, this work proposes the compensation algorithm to overcome the electronic nonlinearity. It is demonstrated that the three-piece linearization approach stabilizes the PEMS system with only a few milliampere current and outperforms the two-piece counterpart with stronger robustness and smoother dynamics under the current-step-change test, especially for the PWM frequency higher than the critical value. Besides, the breakthrough of the critical PWM frequency by the compensation algorithm is of great significance for the dynamic performance of the high-speed PEMS transportation system.

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Section: Introductionmentioning

confidence: 99%

Zero-Power PEMS System with Full-Bridge PWM Inverter: from Mechanism to Algorithm

2021

Preprint

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“…Moreover, in low-resource microcontrollers, the lack of floating-point unit (FPU) represents a disadvantage in the implementation of digital controllers; in other words, when floating-point operations are required to be performed in a microcontroller without FPU, a lot of machine cycle times are consumed; as a consequence, the execution time to complete the operation will be larger than the time consumed by the control algorithm to finish an iteration. Some authors have proposed techniques to implement control algorithms by optimizing the execution time in low-resource microcontrollers; for example, Carmichael et al [5], in 1986 constructed a lookup table to cover all possible floating-point multiplications reducing the execution time. In 2004, Abbadi [1] readjusted the input signal scale with a complex analog interface with specific gain to convert floating-point numbers to integer numbers.…”

Section: Introductionmentioning

confidence: 99%

Digital proportional‐derivative controller implemented in low‐resource microcontrollers

Jiménez-Ramírez

Cardenas-Valderrama

Ordonez-Sanchez

et al. 2020

Comp Applic In Engineering

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The use of software and microcontrollers helps engineering students to gain a better understanding of the different concepts and algorithms of digital control theory, which they can apply in their professional work in industrial environments. Typically, these digital control concepts and algorithms are implemented in high-resources microcontrollers; nevertheless, we show that they can also be implemented in low-resource devices, helping students to acquire fundamental knowledge and develop long-term skills to solve real problems from the learning they achieve in their undergraduate educational programs in control or computer engineering. For this purpose, we provide an algorithm to synthesize a digital proportional-derivative controller oriented to low-resource microcontrollers (microcontrollers without floating-point unit). This algorithm allows implementing solutions for classic controllers in low-resource microcontrollers applied to academic and technological fields. This algorithm reduces the excessive amount of execution time in a low-resource microcontroller, it works with integer numbers and it is designed to implement fast classical controllers, which typically are performed with floating-point operations. Furthermore, we present a brief description of the implemented electronic circuit, serving as a guide for students to develop their own circuits. The experimental results show that the proposed algorithm can be successfully applied to an electromagnetic levitation system, which is commonly used in the academic training of electronics and control engineers, mainly due to its unstable nature. In this case, although the levitation system has a small time constant, the proposed algorithm appropriately leads the system to a stable regime.

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“…They noted that the particular digital control algorithm used was successful but not quite as qood as the corresponding analog one. Carmichael, et al [6] reported the use of digital controls in a single axis vertical support for a 1 in diameter ball. Scudiere, et al [7] employed a microprocessor based digital control system to support small steel spheres and small vertical rotors with masses up to 90 grams.…”

Section: Introductionmentioning

confidence: 99%

Digital Control of Magnetic Bearings Supporting a Multimass Flexible Rotor

Keith

Williams

Allaire

et al. 1990

Tribology Transactions

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This paper considers the characteristics of magnetic bearings used to support a three mass flexible rotor operated at speeds up to 14,000 RPM. The magnetic components of the bearing are of a type reported in the literature previously, but the earlier analog controls have been replaced by digital ones. Analog-to-digital and digital-to-analog converters and digital control software were installed in an AT&T PC. This PC-based digital controller was used to operate one of the magnetic bearings on the test rig. Basic proportional-derivative control was applied to the beatings, and the bearing stiffness and damping characteristics were evaluated. Particular attention is paid to the frequency dependent behavior of the stiffness and damping properties, and comparisons are made between the actual controllers and ideal proportional-derivative control.

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Magnetic suspension systems with digital controllers

Cited by 21 publications

References 3 publications

Zero-Power PEMS System with Full-Bridge PWM Inverter: from Mechanism to Algorithm

Zero-Power PEMS System with Full-Bridge PWM Inverter: from Mechanism to Algorithm

Digital proportional‐derivative controller implemented in low‐resource microcontrollers

Digital Control of Magnetic Bearings Supporting a Multimass Flexible Rotor

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