Modeling of autoresonant control of a parametrically excited screen machine

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.Modelling of nonlinear dynamic response of a screen machine described by the nonlinear coupled differential equations and excited by the system of autoresonant control is presented. The displacement signal of the screen is fed to the screen excitation directly by means of positive feedback. Negative feedback is used to fix the level of screen amplitude response within the expected range. The screen is anticipated to vibrate with a parametric resonance and the excitation, stabilization and control response of the system are studied in the stable mode. Autoresonant control is thoroughly investigated and output tracking is reported. The control developed provides the possibility of self-tuning and self-adaptation mechanisms that allow the screen machine to maintain a parametric resonant mode of oscillation under a wide range of uncertainty of mass and viscosit

Theoretical background for the bionic substantiation of parameters of the stubble cultivator working bodies

In the southern regions of Russia, the technology of cultivation of grain crops in the variant of partial sowing has been widely used. In this regard, it became necessary to create effective working bodies of a stubble cultivator that would have fundamentally new resource-saving ways of influencing the area under cultivating and meet the requirements of modern advanced technologies. The shapes of the working bodies surfaces of the cultivators were improved taking into account the mechanic-bionic approach. The main parameters of the toothed cutting surface were determined by the method of bionic comparisons, with a scarab beetle as a bionic prototype. Use of the serrated shape of the cutting edge is consistent with the bionic principle of multi-contact exposure and leads to the fact that the tops of the teeth become stress concentrators and, with a significantly smaller indentation force, cause soil destruction processes, which reduces the energy costs of cutting the soil layer. The optimal curvilinear shape of the working surface made in the form of a logarithmic spiral, is characterized by a constant value of the angle between the normal and the radius vector, and the value of this angle, equal to the angle of internal friction of the soil φ2, will ensure the sliding of the soil and plant residues with minimal energy consumption. The number (n = 4), height (h = 5...7 mm) and tooth placement step (S = 10...12 mm) of the bit tip of the stubble cultivator are analytically justified. The shape of the profile of the working surface of the stubble cultivator bit in the form of a logarithmic spiral with a variable angle of crumbling is proposed. The studies were conducted in the period from September to October 2018 in the soil channel of the research Laboratory of Bionic Agroengineering of the Department of Mechanization and Technical Service in Agro-Industrial Complex. They have shown the decrease in the traction resistance of the proposed working body of the stubble cultivator by 16.5% in comparison with the traction resistance of the serial sample

Theoretical prerequisites for the bionic substantiation of spring soil leveler working bodies parameters

In the system of measures for pre-sowing tillage, special attention should be given to leveling the soil, ensuring an increase in the uniformity of seeding in depth, which has a significant impact on increasing yields. The main solution to this problem is to improve the design of aligners using a mechanical-bionic approach for the analytical description of the optimal forms and parameters of their working bodies. The design of the working body of the spring soil leveler is proposed, the cutting edges of the undercutting wings of which have ridges and hollows in the form of a logarithmic curve with a positive convexity of curvature inside the depressions, developed by the bionic prototype of the mole cricket (Gryllotalpa). Using the methods of agricultural mechanics, the theoretical dependence of the rational depth of the working bodies and the value of the tractive resistance of spring soil leveler on the travel speed, design parameters and physical-mechanical soil properties, which are proved by the results of experimental research on the south carbonated middle loamy black earth have been established. The experimental spring soil leveler provided the reduction of traction resistance by 7...8% (40...49 N) and had the best stability of motion in depth by an average of 1.5 times (± 0.5 cm) in comparison with the serial model of the working bodies of the leveler VPN-5.6 A

Effect of ultrasonically-assisted drilling on carbon-fibre-reinforced plastics

NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Sound and Vibration. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Sound and Vibration, Volume 333, Issue 23, 24 November 2014, Pages 5939–5952 DOI: 10.1016/j.jsv.2014.05.042This research focuses on the effect of ultrasonically-assisted drilling (UAD) on carbon fibre-reinforced plastics. High-frequency vibration was used to excite a drill bit during its standard operation. An extensive experimental study of drilling forces, temperature, chip formation, surface finish, circularity, delamination and tool wear was conducted using ∅3 mm drill and presented here. UAD showed a significant improvement in drill quality when compared to conventional drilling processes. A finite-element study was also conducted to understand the nature of drilling-force reduction in UAD

Substantiation of parametres of springs vibro tines

The most energy-intensive operation in cultivation of agricultural crops is a soil treatment, which spent up to 40% energy. Among the system of measures to reduce the energy intensity of tillers most important is the use of vibration of working bodies. Vibration of working bodies can be carried out using a forced drive. However, the energy costs of a forced drive to work sometimes exceed the energy costs of passive working bodies. Therefore, it is more appropriate to imparting elastic vibration tillage working bodies due to variable soil resistance in accordance with the phases of deformation and destruction of the soil. The most effective is a vibro-impact effects of the working body on the ground with the use of vibro-impact self-adjusting mechanisms. The object of theoretical study is selected construction of cultivators' paws on the resilient C-shaped stand, the upper part of which is designed as a helical coil spring with hemispherical strikers. When making parameters of vibro spring force action it was considered in view of the current soil resistance. In justifying the design parameters and operating conditions it were used theoretical methods and agricultural mechanics, continuum mechanics, elasticity theory, integral and differential calculus. Given the known forces of resistance to movement through the soil of cultivators paws with vibro-impact spring and sediment spring, taking into account the radius of hemispheric drummers on coils of vibro-impact springs theoretical dependences for definition of key parameters of vibro-impact springs were obtained: wire radius, the radius of the vibro-impact spring, and the number of its active coils. Taking into account the maximum permissible load vibro-impact spring should be used for the manufacture of spring wire. Vibro-impact spring will contribute to self-oscillation

Experimental analysis on autoresonant control of ultrasonically assisted drilling

The target of this paper is to employ autoresonant control technique to maintain the nonlinear oscillating mode at resonance (ultrasonic vibration at the tip of a drill bit at a desired level) during vibro-impact process. In order to achieve this, an autoresonant control system which intends to provide the possibility of self-tuning and self-adaptation mechanism for an ultrasonic vibrating system to maintain the resonant regime of oscillations automatically by means of positive feedback was developed and manufactured. The autoresonant control system was implemented through a ‘controlled variable’ transformation and amplification. Three feedback control strategies were employed depending on the attributes of the ‘manipulated variables’. Mechanical feedback control uses the displacement signal at the end of an ultrasonic transducer. The other two control strategies are current feedback control and power feedback control. The current feedback control employs the current flowing through the piezoceramic rings as the ‘controlled variable’ while power feedback control takes into account both current and power of an ultrasonic vibrating system.In order to investigate the tool effect on the established autoresonant control system, two sizes of drill bits with diameters 3mm and 6mm were employed in combination with three autoresonant control strategies. These were executed in drilling aluminium alloys 1050 with hardness 45HV with a fixed rotational speed combined with several feed rates. Controlled variables, responding variables, feed force reduction were monitored. Holes quality and surface finish examinations supplement the analysis of the efficiency of the control systems

Vibration control of linear split Stirling cryogenic cooler for airborne infrared application

Modern infrared imagers often rely on the split Stirling cryogenic coolers the linear compressors of which are the wellknown sources of harmonic disturbance. The traditional method of their passive isolation fails to meet the restraints on the static and dynamic deflections which are originated by the combined action of the airborne g-loading and harsh random vibration. The vibration protection system, which combines a stiff and heavily damped vibration isolator with tuned dynamic absorber, is studied and optimised for use in the design of an airborne infrared device. Such a design is aimed, primarily, at essential dynamic suppression of the harmonic force which is produced by the linear compressor and, secondarily, at minimisation of environmental vibration loads transmitted through the infrared device to the linear compressor. Experimental testing backed up the theoretical results

Optimization of a universal matchbox on an ultrasonic vibrating system

The main scope of the article is to investigate the effect of ferrite cores gap in a universal matchbox on an ultrasonic vibrating system. A gapped transformer mechanism in a universal matchbox has been thoroughly studied. Characteristics of an ultrasonic vibrating system have been recorded such as mechanical vibrations, inductance, resonant frequencies, current and voltage levels as the gap of ferrite cores gradually increases. In addition, the phase difference between the supplied voltage and the current is also computed and displayed in a Lissajous curve in order to determine the optimal gap between two ferrite cores in the universal matchbox. Explanations supplement the experiment results