Stress-strain magnetoactive propulsion system

. It is possible to create deformations in magnetically active polymeric materials by applying magnetic fields to them. This work develops a symmetrical design scheme of the device, in which the drive and control are carried out by two actuators located on opposite sides. The symmetric scheme with control from two sides allows transporting objects (cargo) in mutually opposite directions (forward and backward). It is proposed to use a magnetically active gel together with a magnetically active elastomer as magnetically active materials. The resulting force effect in the device actuator is produced by interaction of magnetic fields of electromagnets with magnetic fields of permanent magnets. Expressions for obtaining alternating magnetic fields which create conditions for generating alternating magnetic forces in the actuator of the device are given. A prototype design with a controller control device in which signals are generated for an optimum current pulse generator with adjustable duty cycle and duration is presented.


Introduction
In various areas of industrial production, including transport, there is a need to use composite materials with improved performance properties.
Electric, pneumatic, hydraulic drives and their various combinations are used in numerous production technologies. It is not always economically feasible to use these propulsion systems. They are generally bulky, materially intensive, complex to build and difficult to operate. Various sources of energy can be used in the propulsion devices to drive the actuators.
The paper considers the scheme of device and conditions of application of electromagnetic energy by means of combined electromagnetic drive (EmDrive) using magnetoactive polymeric materials: magnetoactive gel and magnetoactive elastomer.
Composite materials based on magnetoactive elastomers and gels, new materials being created, belonging to so called "smart materials" and "smart materials" belong to a promising class of materials, being developed and constantly improving, which have physical properties, the use of which allows creating propulsion devices. The possibility of using developed composite materials with a porous structure in which it is possible to form a deformation effect under the action of electric impulses coming from the controller -the control brain -can be to some extent analogous to the muscle of a living human body.
Various research centres are conducting research and development of promising materials, which include elastically controlled composite materials capable of deforming and changing their parameters under the action of magnetic fields. Magnetic filler particles can move under the influence of an applied external magnetic field [1,2].
The material under study has shape memory, i.e., the ability to retain its original shape after deformation and deactivation of the influence of magnetic fields [3][4][5]. Various methods can be used in structures to produce elastic and easily reversible deformation of a magnetically active elastomer by applying magnetic fields to it [6][7][8].
When investigating the dynamic properties of magnetically active elastomers on vibrodynamic test benches, it was shown that exposure of the test specimens to magnetic fields resulted in significant shifts in the resonance frequencies [9]. The developed device using the resonance frequency control system made it possible to shift the resonance frequencies and thus, reduce undesirable vibration amplitudes in the operated product [10]. In [11], a scheme of control and operation when using a magnetoactive elastic material to create displacements on the rod of the controlled thruster is proposed.

Developing a double-sided circuit for a magnetoactive actuator
A scheme is proposed for a double-sided magnetoactive propulsion device that generates controlled magnetic fields that create elastic deformation in a magnetoactive composite material.   1 shows a double-sided functional diagram of magnetic actuator device based on interaction of magnetic field of neodymium Nd-magnet with magnetic field of electromagnet and with magnetically active materials using gel and elastomer. The device contains: 1, 4, 11 -magnetic-soft magnetic circuit conductor body; 2, 10 -tinsel wire; 3, 9 -magnetoactive elastomeric element; 5, 8 -electromagnet coils; 6, 14 -niodium (Nd) magnets; 7magnetoactive gel; 12, 15 -moving rods; 13 -magnetic-soft circuit conductor. Figure 1 in the control unit -I contains analog-digital converter, controller, software control; memory unit, digital-to-analog converter and signal amplifier. The displacement of the rod by the set value h is formed by the values of displacements h1 and h2 created in the elastic, magnetically soft elements of the magnetic circuit.
The creation of conditions for the functioning of the proposed transport mover is based on the action of magnetic forces generated in the magnetically soft elements of the magnetic circuit in the interaction of the magnetic field of the neodymium magnet, which has magnetic induction, with the pulse magnetic field created in the coil of the electromagnet, the induction amplitude of which is set by the amplitude of the current pulse entering the electromagnet coil from the controller in accordance with the preset program.
The resulting magnetic force developed in this device can be described using the following expression: In (1) − is net magnetic force; -magnetic induction of neodymium magnet (Nd); -pulsed magnetic field induction amplitude in the solenoid coil; − -area of interaction between Nd-magnet and electromagnet (elm); − -is the distance between the interaction areas of the Nd-magnet and the electromagnet.
The induction amplitude of the pulsed magnetic field in the coil of the electromagnet is determined by the expression: In the expression (2) -is the relative magnetic permeability of the substance in the N-S magnetic field gap, which can be filled as air with = 1, and jelly-like gel with ferromagnetic microparticles embedded in its molecules with 2000; 0 = 4 ⋅ ⋅ 10 −7magnetic constant (Hn/m); Helm -magnetic field strength in the N-S electromagnet gap when flowing through the coils -nelm its current amplitude coils -. The expression (2) can be represented in the form: Amplitude of current -in expression (3) in the coil of the electromagnet, and hence the induction -and, consequently, the magnitude of the magnetic force -FNd-elm can be adjusted from zero to a maximum set in the controller.
The force arising from the interaction of the magnetic fields − drives in mutually opposite directions (forward and reverse), depending on the polarity of the current amplitude , coils of electromagnets 5 or 8 connected through rods in the form of movable rods 15 or 12 on the moving object element shown in Fig. 1. To increase magnetic force − the gap is fitted with an elastically deformable element 3 and 9 made of magnetically active elastomer with magnetic permeability  2000 significantly higher than the magnetic permeability of air (vacuum), which has = 1. To increase magnetic force − gap (N -S) with the coil of the electromagnet is filled with jelly-like gel 7 containing ferro-magnetic microparticles which also increase the magnetic permeability of the gap to values ≅ 2000.
The coil leads of electromagnets 5 and 9 are made with a special multi-core, mishurry wire 2 and 10, resistant to multiple bends, withstanding multiple movements of the coil.
The electromagnet coil is connected directly to the rectangular pulse generator output with amplitude Umelm. The magnitude of this amplitude must be sufficient for the required rectangular pulse current .


In order to obtain significant magnetic forces, it will be necessary to obtain appropriate current pulses. In this case, expression (1) can be represented as follows: As can be seen from the expression (4), for magnetic force control, the current amplitude is the most convenient and optimum for varying it smoothly over a wide range . The oscillator circuit also provides the ability to adjust the duty cycle, duration and period impulses by changing the resistance value of the resistor.
The coil resistance is a complex value for the surge current : where: is active resistance of the solenoid coil, ; = 2 ⋅ ⋅ -circular frequency; in equation (5) -linear frequency of current pulses in the solenoid coil ; coil inductance of the solenoid, ; coil cross-sectional area, 2 ; magnet coil length, ; is the number of turns of the electromagnet.

Results
The resulting dependencies make it possible to determine a given amount of movement of the device's moving rods using resilient, magnetically soft magnetic circuit elements. Fig.2 shows the prototype of the coil magnet device on the left; the controller control unit is shown on the right; the oscilloscope screen in the background shows the impulse loads generated.

Fig. 2. Prototype device.
In order to operate the magnetic actuator in pulse mode, the controller of the control unit contains rectangular pulse generators with solenoid coils connected to their outputs (one of these is shown in Figure 2, left). Fig. 2 on the right shows the prototype microcircuit of one of the generators with adjustable duty cycle and duration, corresponding to the optimum mode, of rectangular pulse current flowing through the coils of solenoids connected to the outputs of the generators in pulse mode of operation of the mechanism. Figure 2 shows a model of the magnetic actuator itself with Nd magnets, coils and ferrite magnetic field conductors on the left-hand side. In the background of Fig.2, the oscilloscope screen shows the rectangular pulses of current flowing through the solenoid coils connected to the outputs of the prototype oscillators assembled on microchips.

Discussion
The proposed development of a double-sided magnetoactive propulsion device using magnetically soft controllable composite materials can find use in various areas of industrial transport engineering. The peculiar advantage and convenience of the developed structural scheme consists in a possibility to create deformation and movements of the device alternately in two mutually opposite directions (with forward and backward motion) depending on the direction of signals to actuators. Expressions are given for the generation of alternating magnetic fields which create conditions for generating alternating magnetic forces in the device actuator and creating transport propulsion.
Developed combinations of constituent components make it possible to create composite elastic polymeric materials with given controllable dynamic properties.
Technological possibilities of using the so called "smart materials" being developed and tested for transport devices will constantly expand, that is why it is advisable to continue research on development of devices based on electro-and magneto-controlled magnetoactive composites and their testing in laboratory conditions.