Electromagnetic drive

Abstract

FIELD: electrical engineering.SUBSTANCE: electromagnetic drive is designed for space scientific instruments that require the translational motion of individual elements. The drive includes four windings with movable cores and one rod, the length of which is greater than the length of the cores by the value of the working stroke of the rod. The axes of the windings and the rod are parallel. The rod is connected on one side by a jumper to one pair of cores, and on the other side by a jumper to another pair of cores. Thus, two windings provide movement of the rod in one direction, and two in the other. In the extreme positions, the rod is fixed with permanent magnets.EFFECT: increase in the reliability of the drive while simultaneously ensuring the ability to move the core with locking it in extreme positions.1 cl, 3 dwg

Description

[0001] The technical field to which the proposed technical solution belongs

[0002] The invention relates to the field of electrical engineering and can be used in space scientific instruments in which it is necessary to set individual elements into translational motion, for example, in systems for calibrating space X-ray telescopes based on extending a radionuclide calibration source into the field of view of the detector.

[0003] Description of the prior art in this field

[0004] Electromagnetic drives are widely used in virtually all fields of science and technology. However, such drives designed for space applications have specific requirements that preclude the use of most technical solutions developed for ground-based equipment. Traditional requirements for space drives include minimizing weight, size, and power consumption, as well as the ability to operate under the influence of space factors.

[0005] However, their primary requirement is near-absolute reliability under the harsh conditions of space, taking into account the impossibility of replacement or repair. This requirement can be illustrated by the example of Russia's first X-ray mirror telescope, the M.N. Pavlinsky ART-XC, launched into space in 2019 as part of the Spektr-RG space observatory. The lack of domestic experience in creating similar telescopes required the development of virtually all of its components from scratch. In particular, these elements included the calibration source units. They perform the simple function of periodically extending radionuclide X-ray sources into the field of view of each of the telescope's seven X-ray detectors for calibration. At first glance, these devices appear to be auxiliary. However, their failure in some cases means that the entire telescope cannot perform its intended task.If the sources cannot be retracted into the isolated volume, the detectors cease to detect external radiation due to constant exposure to radiation from the extended calibration source. Therefore, the functionality of these devices is critical to the operation of the entire telescope.

[0006] During the development of the ART-XC telescope, extensive prototyping and research was undertaken to explore various schemes for periodically irradiating its detectors with calibrated X-rays. During this process, the most suitable technical solution for the task was identified. It was determined that the optimal kinematic design for such a device should be based on a linear drive. This drive would move the calibration source from a lead-shielded cavity into the detector's field of view and reinsert it after calibration is complete.

[0007] The only ready-made solution at the time of the telescope's creation that met most of the requirements and passed all ground tests was the HaydonKerk 28N47-12-025 Class 1 linear actuator. This actuator was a linear motion drive consisting of a stepper motor with two control windings and a screw-and-nut transmission.

[0008] However, from the point of view of space application, this drive has the following disadvantages:

[0009] - the impossibility of redundant electric drives while maintaining acceptable weight and size characteristics and without significantly complicating the design, which does not allow the use of the standard method for space devices to increase reliability by duplicating systems;

[0010] - at low temperatures there is a risk of the screw-nut transmission seizing in extreme positions, and there is also a critical dependence of the performance of this transmission on maintaining the characteristics of the lubricant used in it when exposed to aggressive factors of outer space;

[0011] - additional reduction in reliability and increase in the overall system's weight and dimensions due to the need to use a complex control unit for this drive.

[0012] In addition, significant disadvantages of this actuator were its high cost and foreign production, which currently made this drive unavailable for purchase.

[0013] Electromagnetic electric drives are potentially free of the above-mentioned disadvantages. However, for use in space devices, particularly in a calibration source unit, they must provide:

[0014] - extremely high degree of reliability with minimal weight, dimensions and power consumption;

[0015] - reciprocating action;

[0016] - fixation in extreme positions;

[0017] - the core stroke is sufficient to perform its functions, usually from 20 to 30 mm.

[0018] Electromagnetic drives with a single winding and a spring are known (Kazakov L.A. Electromagnetic Devices of REA: Handbook. - Moscow: Radio and Communications, 1991. - 352 p.: ill.), which returns the core to its original position when the supply voltage is removed from the winding. However, with this option, the winding remains under voltage for an extended period. In particular, in the ART-XC telescope, the calibration source is extended for 1 hour during each calibration cycle. During this time, the winding consumes electrical energy. Firstly, its reliability decreases due to increased heating, which occurs due to the difficulty of heat dissipation in the vacuum of space. Secondly, the energy efficiency of the device is significantly reduced. Therefore, the optimal option for space-based drives is to use two windings, providing pusher movement in two opposite directions.

[0019] A two-position electromagnetic actuator (USSR Author's Certificate No. 728179) is known, containing two windings and a permanent magnet. The windings provide bidirectional movement of the core. The permanent magnet magnetizes the actuator housing, which ensures the core is fixed in its extreme positions by being attracted to the magnetized housing.

[0020] A drawback of this design is the critical dependence of the entire device's performance on the performance of any single winding, making its reliability unsatisfactory for space applications. Furthermore, this design limits the core's travel, and expanding it requires a significant increase in the overall weight and dimensions.

[0021] The purpose of the proposed solution

[0022] The purpose of the proposed solution is to increase the reliability of the electromagnetic drive and ensure the ability to move the core with the ability to fix it in extreme positions.

[0023] Prototype Description

[0024] The prototype of the proposed device is a reciprocating electromagnetic drive with two windings, a retractable cylindrical core, and a magnetic circuit without a stop with openings at both ends for the passage of the core (USSR Author's Certificate No. 83442), which allows for increased core travel without lengthening the coil. Moreover, the electromagnet windings in this drive are arranged in series, and their alternate activation changes the direction of the core's motion.

[0025] The main drawback of this design for space applications is its poor reliability. Failure of any winding renders the entire device inoperable. Furthermore, the longitudinal dimensions of the design are increased due to the sequential arrangement of the coils, and there is no core locking mechanism at the extreme positions.

[0026] The essence of the proposed technical solution and its description in statics

[0027] To achieve this goal, it is proposed to use four windings on frames (hereinafter referred to as "windings"), each with a separate core. Two windings pull their cores in one direction, and two in the opposite direction. The actuator of the device is a separate rod, rigidly connected to the winding cores. Permanent magnets are used to fix the rod in its extreme positions.

[0028] The basic configuration of the proposed device is shown in Figure 1.

[0029] In this configuration, the proposed device comprises four identical windings 1-4 with separate identical cores 5-8, which are freely movable along the winding axes. The length of cores 5-8 corresponds to the length of windings 1-4. The axes of windings 1-4 are parallel to each other. The ends of windings 1-4 pass through the same plane, with their centers forming a rectangular quadrangle.

[0030] A movable rod 9, which is the actuator of the drive, is located in the middle between windings 1-4. The axis of the rod is parallel to the axes of the windings. The length of the rod 9 is greater than the length of windings 1-4 by the amount of stroke l of the rod 9 required for the device to perform its functions. One end of the rod 9 is connected by means of a jumper 10 to the ends of those two cores 5, 6, the axes of which lie in the same plane with the axis of the rod 9. The other end of the rod 9 is connected by means of a jumper 11 to the other two cores 7, 8. Accordingly, cores 5, 6 of windings 1, 2 located diagonally are shifted along their axes relative to the other two cores 7, 8 by the amount of the required movement l.

[0031] Windings 1-4 and rod 9 are mounted in housing 12, which ensures the mutual arrangement described above. Windings 1-4 are mounted immobile, while rod 9 is movable along its axis. The longitudinal dimensions of housing 12 must not extend beyond the ends of windings 1-4.

[0032] In the jumpers 10, 11, two magnets 13, 14 and 15, 16 are installed symmetrically relative to the axis of the rod 9. In this case, the jumpers 10, 11 are made of a non-magnetic material, and the body 12 contains mating ferromagnetic pads to which magnets 13 - 16 are attracted.

[0033] Dynamic Description

[0034] The operation of the proposed drive is illustrated by Figure 2.

[0035] The initial state of the drive is the absence of power on all windings 1-4, and the presence of rod 9 in one of the two extreme positions due to the holding of one of the jumpers (for example, 11) on the housing 12 by magnets 15, 16 (Figure 2a).

[0036] When power is supplied (corresponds to the "on" designation in Figure 2) to windings 1, 2, into which cores 5, 6 are not fully inserted, a force F is generated, drawing cores 5, 6 into windings 1, 2 (Figure 2b). When the attractive force of magnets 15, 16 holding jumper 11 on housing 12 is exceeded, cores 5, 6 are drawn into windings 1, 2, simultaneously moving rod 9 connected to them and cores 7, 8 connected to this rod. The movement is carried out to the second extreme position of rod 9, in which magnets 13, 14 of jumper 10 are attracted to housing 12 (Figure 2c).

[0037] After this, in order to return the rod 9 to its original position, shown in Figure 2a, it is necessary to supply power to the windings 3, 4. Accordingly, a force F is generated, pulling the cores 7, 8 into the windings 3, 4 (Figure 2g). After the jumper 10 is separated from the housing 12, the cores 7, 8 with the rod 9 and cores 5, 6 move to their original position (Figure 2a).

[0038] The reliability of this device is ensured by the fact that its operation is maintained if at least two of the four windings that ensure the movement of rod 9 in opposite directions remain operational. Turning on the coils only during movement ensures minimal power consumption and eliminates the heat dissipation problem typical of devices operating in a vacuum and generating heat for extended periods. Furthermore, controlling this drive requires a simple, and therefore most reliable, control unit based on a simple cyclogram of winding power supply switching.

[0039] The proposed device configuration is suitable for providing a wide range of piston strokes without additional design complexity. This configuration simultaneously offers two advantages. First, this winding arrangement is the most compact of all possible. Any other arrangement would increase the longitudinal or transverse dimensions of the device. Second, the mechanical connection between the cores and the piston rod proposed for this winding arrangement ensures that the piston rod is not subject to torque during normal operation. This reduces the likelihood of the piston rod or cores becoming jammed in the guide channels.

[0040] Example of the implementation of the proposed solution

[0041] A prototype of an electromagnetic drive was manufactured, shown in Figure 3 (on the left - in the retracted position, on the right - in the extended position).

[0042] The prototype includes a composite housing containing a base 18, end plates 21, a nylon sleeve 20 and two ferromagnetic rings 19 (one ring on each plate 21). Four windings 1-4 are rigidly installed in this housing, the ends of which are rigidly attached to the end plates of the housing 21. The axes of the windings are parallel. Their centers form a rectangular quadrangle. Inside the windings are movable cores 5-8. In the center between the windings, a rod 9 is located, which can move freely inside the nylon sleeve 20. The length of the rod 9 is greater than the length of the windings 1-4 by the amount of rod stroke. The end of the rod 9 is connected by a jumper 11 to the ends of the cores 7, 8, located diagonally in a rectangular quadrangle passing through the centers of the windings 1-4. The other end of the rod 9 is connected to the ends of two other cores 5, 6 by two jumpers 10.

[0043] Magnets 13-16 are glued into jumpers 10 and 11. These magnets are attracted to ferromagnetic rings 19, thus holding rod 9 in its extreme positions. Rod 9 contains calibration source 17.

[0044] The stroke of rod 9 and cores 5-8 is 30 mm. The weight of the entire structure is 380 g. The maximum overall size (length) of the structure is 97 mm.

[0045] Tests of the operation of this prototype, including those conducted after mechanical impacts typical of launch vehicles, confirmed the operability of this prototype.

Claims

An electromagnetic drive containing windings with movable cores, characterized in that it uses four identical windings, each of which has a separate core of the same length, in addition, the drive has a separate movable rod, the length of which is greater than the length of one winding by the amount of the rod stroke, the axes of the windings and the rod are parallel, and the ends of the windings lie on a plane perpendicular to their axes, the intersection of the axes of the windings with this plane are the vertices of a rectangular quadrangle, and the intersection of the axis of the rod with this plane is in the center of this quadrangle, one end of the rod has a rigid mechanical connection with the ends of the cores of two windings located diagonally along this quadrangle, and the opposite end of the rod has a mechanical connection with the opposite ends of the cores of two other windings, in addition, the drive includes a housing,which ensures a fixed position of the windings and the possibility of free axial movement of the rod, while the mechanical connections of the rod and cores are made in the form of parts made of non-magnetic materials in which magnets are installed, and opposite them in the drive housing there are platforms made of ferromagnetic material.

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