Degrees of Freedom Control through Three Electromagnets and Three Linear Induction Motors
Configuration that the mover has three electromagnets and three linear induction motor (LIM) has been proposed for contactless flexible conveyance system. Hybrid electromagnet that uses permanent magnet can let power consumption converge to zero in steady state, and its stator becomes simple because the combination of three LIM’s is used for two-dimensional drive. The normal attractive force of LIM can increase the carrying capacity of the mover, although it can be also disturbance force for the stabilization of the magnetic levitation system. Authors have experimentally confirmed that the proposed configuration can realize six-degrees of freedom control of the mover. Position sensing for the closed loop control of two-dimensional linear drive is difficult: one possible approach based on visual sensing combined with dual sample-rate digital observer is proposed and discussed.
4 Poles 3 Degrees of Freedom Magnetic Levitation Control and its Coordination with Two-Dimensional Linear Motor
Electromagnetic suspension (EMS) has been widely used in many industrial fields because of various advantages in practical use. The U-type magnets are often used to generate the levitation force in the EMS system. This conventional electromagnet, however, can only control one degree-offreedom. It cannot construct a levitation system solely by itself. A 4-pole type yoke hybrid electromagnet is proposed instead of the usual U-type magnet and its magnetic levitation control is studied in this paper. The basic structure and characteristics of the proposed magnet are described, and the control systems are designed. The semi-zero-power controller, with a disturbance observer, is proposed to improve the performance of the control system. Furthermore, the combination with the linear motor is discussed.
Sustainable production of toxin free marine microalgae biomass as fish feed in large scale open system in the Qatari desert.
Mass cultivation of microalgae biomass for feed should be cost effective and toxin free. Evaporation loss in Qatar can be as high as 2 cm/d. Hence, production of marine microalgae biomass in Qatar would also require mitigating water loss as there was only very limited groundwater reserve. To address these issues, a combination of four growth conditions were applied to a 25,000 L raceway pond: locally isolated microalgae strain was selected which could grow in elevated salinity; strain that did not require silica and vitamins; volume of the culture would increase over time keeping denser inoculum in the beginning, and evaporation water loss would be balanced by adding seawater only. A local saline tolerant Nannochloropsis sp. was selected which did not require silica and vitamins. When the above conditions were combined in the pond, average areal biomass productivities reached 20.37 g/m(2)/d, and the culture was not contaminated by any toxic microalgae.