Modeling of Ironless Permanent Magnet Planar Motor Structures

In this paper, finite element analysis is used to develop a fast model that includes end-effects and allows performance and controllability analysis without specifying a commutation scheme or control method is for ironless permanent magnet planar motor structures

The Role of IGF-1 for Fracture Risk in Men

Growth hormone and insulin-like growth factor-1 (IGF-1) are essential for the achievement of normal longitudinal bone growth and bone mass. Preclinical studies using various knockout models have shown that both endocrine (mostly liver-derived) IGF-1 and bone-derived IGF-1 contribute to normal longitudinal skeletal growth and cortical bone size. Since bone size is an important determinant of bone strength, and hence fracture risk, we evaluated the predictive role of serum IGF-1 for fracture risk. The population-based Osteoporotic Fractures in Men Sweden cohort recently showed for the first time that older men with low serum IGF-1 levels have an increased fracture risk, especially for the two most important fracture types, hip and vertebral fractures. This association between serum IGF-1 and incident fracture risk is partly mediated via bone mineral density. Future studies are required to identify the mechanisms by which endocrine and local IGF-1 regulate skeletal growth and bone size. In addition, possible mediators affecting the impact of IGF-1 on fractures in men remain to be elucidated

Natural circulating current control of a cycloconverter

In order to perform experimental verifications of theoretical analyses and simulations related to field-oriented controlled AC drives, especially at low frequencies, a 20 kVA power converter was needed. This converter should act as a voltage amplifier, allowing the load current to change direction without discontinuities. For this purpose, a six-pulse cycloconverter with natural circulating current was chosen. A control strategy is introduced for this device which is based on the shape of the natural (uncontrolled) circulating current. Simulations show that, using this method, with a relatively simple control circuitry, the circulating current can be controlled in such a way that it never becomes zero. As a result, the load current is free to change direction without becoming discontinuous and without a dead zone, and the output voltage can be controlled independently of the load current. Practical experiments confirmed the theory and the simulation

Design of a Magnetic Bearing

A popular approach to nano-positioning requirements in precision engineering in general and micro-lithography in particular is to subdivide the stage positioning architecture into a coarse positioning module with micrometer accuracy (Long Stroke), onto which a fine positioning module (Short Stroke) is cascaded. The latter is responsible for correcting the residual error of the coarse positioning module to the last nanometers. High accuracy positioning in 6 Degrees Of Freedom put severe constraints on the actuators and/or bearing systems. Actuators are used for generating a varying force being part of a control loop. Bearing systems should generate a force as constant as possible in the bearing direction, but the force perpendicular to that direction should be as low as possible. Actuators could serve as a bearing system, but on the one hand this would require the actuators to be large and thus heavy and on the other hand a substantial amount of heat is continuously dissipated in order to generate the static forces. Such heat generation does not contribute to the positioning performance of the actuators, but significantly affects the thermal stability of the application. The latter implication will be overcome if the bearing system is established by a system with permanent magnets

Contactless Planar Actuator with Manipulator

The accuracy and reliability of high-precision machines is compromised by friction and disturbances due to cables to moving machine parts. These problems can be solved by applying three contactless techniques in one system: contactless generation of forces and torques, contactless energy transfer to a moving load and wireless control. This paper presents an overview of the research performed at Eindhoven University of Technology to create a contactless planar actuator with manipulator, a system which combines all three contactless techniques