Redundant Field Survey Data of Cyclotron with Imperfect Median Plane

An accurate and detailed field map is important for cyclotron beam dynamics studies. During the long history of cyclotron studies, many techniques have been developed by cyclotron pioneers for the treatment of median plane field map. In this paper, we take the TRIUMF 500 MeV cyclotron as an example to study the asymmetric field resulting from the imperfect median plane symmetry. The ``Gordon approach'' and a highly accurate compact finite differentiation method are used to investigate the historical field survey data. The redundancy in the survey data is revealed by the expansion method, which also makes it possible to correct the error in the measurement. Finally, both the azimuthal field $B_\theta$ and the axial gradient of the axial field $dB_z/dz$ in the median plane are corrected using the radial field map $B_r$. The influence of the correction is examined by recalculating the equilibrium orbit properties of the TRIUMF cyclotron. The result shows significantly increased vertical centering errors of the closed orbits. Further simulation study suggests that these centering errors can be reduced to below 1.5 cm by adjusting the trim coils' $B_r$ field within the output limits of our trim coils' power supplies. The error in the measurement field data may explain why the calculated trim coils' settings during the cyclotron commissioning in 1974 encountered difficulty

High frequency parameter sensitivity in hydraulically interconnected suspensions

In this paper, the development of a hydraulically interconnected suspension (HIS) system model and its integration into a four degree-of-freedom half-car system is briefly introduced. Frequency response functions are derived in order to simulate the system response to a stochastic road profile. The sprung mass vertical and roll accelerations are considered in the frequency domain up to 1000 Hz. Four key hydraulic system parameters which affect the system’s high frequency dynamics but not its low frequency response are identified and investigated. The results indicate that HIS system performance in the high frequency range (50-1000 Hz) can be greatly affected by these hydraulic parameters, while the favourable ride characteristics typical of HIS vehicles are retained

Design of mechanical metamaterials using a level-set based topology optimization method

Metamaterials are a family of artificially engineered materials consisting of an array of periodically arranged microstructures, offering unusual material properties that may not be easily found in nature. This paper will propose a new topological shape optimization method for the design of mechanical metamaterials with negative Poisson’s ratios, by integrating the numerical homogenization method with a powerful level set method. The homogenization method is used to calculate the effective properties of the microstructure, and the level set method is utilized to implement shape and topology optimization of the microstructure until the desired material properties are obtained. The proposed method can retain the unique features of the level set methods, while avoid unfavourable numerical issues occurred in the conventional level set methods. Several typical numerical examples are used to showcase the effectiveness of the proposed design method

Fuzzy PID control of a two-link flexible manipulator

For a flexible manipulator system, the unwanted vibrations deteriorate usually the performance of the system due to the coupling of large overall motion and elastic vibration. This paper focuses on the active vibration control of a two-link flexible manipulator with piezoelectric materials. The multi flexible body dynamics (MFBD) model of the two-link flexible manipulator attached with piezoelectric sensors and actuators is established firstly. Based on the absolute nodal coordinate formulation (ANCF), the motion equations of the manipulator system are derived and motion process and dynamic responses of the system are simulated. According to the time varying feature of system, a fuzzy PID controller is developed to depress the vibration. This controller can tune control gains online accommodating to the variation of the system. Control results obtained by the fuzzy PID control and the conventional PID control indicate that the fuzzy PID controller can effectively suppress the elastic vibration of the manipulator system and performs better than the conventional PID controller

Determination of Modal Parameters of a Half-Car Fitted with a Hydraulically Interconnected Suspension from Simulated Free decay Responses

This paper presents an alternative approach for determining the vibration modal parameters, in terms of natural frequencies, damping ratios and modal shapes of a roll-plane half-car fitted with a general hydraulically interconnected suspension system. The dynamic model of the system, which consists of the sprung mass and the HIS and the wheels, is formulated using the state space representation approach. The state variables describing rigid body motions of the sprung and unsprung masses are heavily coupled with those describing the dynamics of HIS fluid circuits. A numerical simulation scheme is developed to obtain the transient and free decay responses of the half car vehicle using specific initial conditions or road inputs. The obtained results are compared with those determined from the free vibration analysis of the system using the transfer matrix method. Discussions on the advantages and limitations of the presented method are also provided

Microembossing of ultrafine grained Al: microstructural analysis and finite element modelling

Ultra fine grained (UFG) Al-1050 processed by equal channel angular pressing (ECAP) and UFG Al-Mg-Cu-Mn processed by high pressure torsion (HPT) were embossed at both room temperature and 300 °C, with the aim of producing micro-channels. The behaviour of Al alloys during the embossing process was analysed using finite element (FE) modelling. The cold embossing of both Al alloys is characterised by a partial pattern transfer, a large embossing force, channels with oblique sidewalls and a large failure rate of the mould. The hot embossing is characterised by straight channel sidewalls, fully transferred patterns and reduced loads which decrease the failure rate of the mould. Hot embossing of UFG Al-Mg-Cu-Mn produced by HPT shows a potential of fabrication of microelectromechanical system (MEMS) components with micro channels

Robust sampled-data control of structures subject to parameter uncertainties and actuator saturation

This paper presents a robust sampled-data controller design approach for vibration attenuation of civil structures considering parameter uncertainties and actuator saturation. The parameter uncertainties belong to polytopic form and are assumed to be the variations of the structural stiffness and damping. Regarding the uncertain sampling problem encountered in real world applications, the sampling period designed for the controller is allowed to be variable within a given bound. In order to obtain reduced peak response quantities, the energy-to-peak performance used to describe the peak values of the control output under all possible energy-bounded disturbances is optimised. The robust sampled-data state feedback controller is obtained in terms of the solvability of certain linear matrix inequalities (LMIs). The applicability of the proposed approach is demonstrated by a numerical example on vibration control of a building structure subject to seismic excitation. It is validated by the simulation results confirming that the designed controllers can effectively attenuate the structural vibration and keep the system stability while there are parameter uncertainties and actuator saturation constraints. (C) 2011 Elsevier Ltd. All rights reserved