If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -This paper presents the design of climbing robots for glass-wall cleaning. Design/methodology/approach -A systemic analysis of the basic functions of a glass-wall cleaning system is given based on the research of working targets. Then the constraints for designing a glass-wall cleaning robot are discussed. The driving method, the attachment principle, mechanical structure and unique aspects of three pneumatic robots named Sky Cleaners follow. In the end a summary of the main special features is given. All three climbing robots are tested on site. Findings -Our groups spent several years in designing and developing a series of robots named Sky Cleaners which are totally actuated by pneumatic cylinders and sucked to the glass walls with vacuum grippers in mid-air. It was found that they can meet the requirements of glass-wall cleaning.Research limitation/implications -The air source, cleaning liquid and control signals should be provided by the supporting vehicle stationed on the ground. Even if the robots are intelligent, the suitable working height is below 50 m because the weight of the hoses has to be taken into account when the robots work in mid-air. Practical implications -The cleaning robotic systems can avoid workers presence in a hazardous environment and realize an automatic cleaning, furthermore reduce operation costs and improve the technological level and productivity of the service industry in the building maintenance. Originality/value -Sky Cleaner robots can move and do cleaning on the plane glass wall or the special curve wall with a small angle between the glasses. The first two prototypes are mainly used for research and the last one is a real product designing for cleaning the glass surface of Shanghai Science and Technology Museum.
The hysteresis band controller offers excellent dynamic performance. It has been widely researched and applied for the voltage source inverter and inverter fed drives, however it has not been investigated within the context of a matrix converter or a matrix converter based motor drive. In this paper, both fixed-band and sinusoidal-band hysteresis current controllers are proposed and developed for a direct matrix converter. A comprehensive comparative evaluation of the two methods is then carried out. Both methods have fast dynamic performance and they inherently integrate the line modulation technique of the virtual rectifier stage into the overall modulation. Surge currents are prevented with the proposed scheme. The sinusoidal-band hysteresis controller demonstrates lower total harmonic distortion at the expense of higher average switching frequency, which is only significantly observable at very high sampling frequencies. The proposed controller is integrated with the field-oriented control to drive a matrix converter fed permanent magnet synchronous machine. The proposed methods are simple and incur a light computational burden, which advances the practical applications of matrix converters in AC motor drives. The simulation and experiment results demonstrate the effectiveness and feasibility of the proposed scheme.
This paper proposes a modified proportional-integral (PI) controller and compares it with a proportional-resonant (PR) controller. These controllers are tested on a three-phase direct matrix converter (MC). The modified PI controller involves current feedforward together with space vector modulation (SVM) to control the MC output currents. This controller provides extra control flexibility in terms of the current error reduction, and it gives improved steady-state tracking performance. When the coefficient of current feedforward is equal to the load resistor (K = R), the steady-state error is effectively minimized even when regulating sinusoidal variables. The total harmonic distortion is also reduced. In order to comparatively evaluate the modified PI controller, a PR controller is designed and tested. Both the modified PI and PR controllers are implemented in the natural frame (abc) in a straightforward manner. This removes the coordinate transformations that are required in the stationary (αβ) and synchronous (dq) reference frame based control strategies. In addition, both controllers can handle the unbalanced conditions. The experimental and simulation results verify the feasibility and effectiveness of the proposed controllers.
This paper investigates the matrix converter when working as the unified power flow controller which can regulate the active reactive power flowing in a transmission line. A conventional unified power flow controller usually has a DC capacitor; this is removed in the proposed controller. This reduces the volume, improves the efficiency and lifetime, and eliminates the DC voltage control. The detailed direct space vector modulation method for the matrix converter is described. Based on this modulation scheme, a PID controller is designed in order to control the power flow. Coupling effects are suppressed by feedback of the coupling components to the controller. The proposed strategy can control the active and reactive power efficiently and effectively. Simulations based on MATLAB/Simulink help verify the feasibility and effectiveness of the scheme.
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