Application and Study on Heat Transfer Model for Continuous 82B Billet Casting
The centerline segregation in the 82B steel billet reduces seriously the final product quality; it is closely related to the unreasonable secondary cooling water system. This paper has established a two-dimensional non-steady-state heat transfer model for the continuous 82B billet casting process, and optimized the existing secondary cooling water scheme, The results show that: the strand surface temperature falling rate is lower than the center temperature falling rate in the original cooling water scheme; it is necessary to add an additional cooling subzone after the fourth subzone for decreasing centerline segregation; the optimal cooling water scheme is that cooling intensity of the fifth subzone is increased by 150% compared with the original fourth subzone.
Improvement of inner quality of continuously cast billets using electromagnetic stirring and thermal soft reduction
Centreline segregation in continuously cast billets has been decreased using thermal soft reduction (TSR) at the end of solidification in the caster. Full scale experiments have shown that it is possible to decrease the segregation ratio in steel with 0.51%C from 1.23 to 1.10. The segregation ratio is calculated as the mean value plus two standard deviations from 30 samples divided by the ladle composition. Multivariate data analysis (MDA) has been used to find the relationship between observed segregation and registered process variables. The MDA model's ability for explanation is sufficiently high to be used as a model for segregation prediction. The influence of different variables according to the MDA model agrees well with that determined by traditional methods of evaluation. The short range variation of segregation along the centreline can not be explained by the variables in the MDA model. Electromagnetic stirring in the mould alters the best position of the TSR cooling zone in the caster.
L1 Adaptive Controller for Attitude Control of Multirotors
In this work we show an application of L1 Adaptive control theory for attitude control of UAVs. We implement the flight control system on a multirotor to show robustness and precise attitude tracking in the presence of modeling uncertainties and environmental disturbances. We choose backstepping control architecture, since the kinematics and dynamics of multirotors in most cases can be written in strict feedback form. We further exploit the fact that the kinematics of the plant, while free of uncertainties, is nonlinear, which makes it highly suitable for dynamic inversion control at each level of backstepping. On the other hand, plant dynamics is uncertain and is affected by environmental disturbances such as wind gusts, unmodeled dynamics etc. Therefore, we consider 3 variants of the control architecture. The first method uses backstepping to determine the moment demand and augments it with the L1 adaptive controller to account for uncertainties and provide robustness with guaranteed transient performance. The second architecture apply the concept of L1 adaptive backstepping to the same problem; and the third architecture uses L1 backstepping for quaternion representation of the system dynamics, which helps to avoid the singularities associated with Euler angles.