RU2347300C2 - Inertial step motor - Google Patents

Abstract

FIELD: physics, measurement.

SUBSTANCE: invention is related to devices for mechanical displacement of objects along single coordinate. It may be used, for instance, in scanning probing microscope (SPM) for approaching of probe and sample. Inertial step motor comprises base with fixed piezoelectric modulus combined with rod of square section, where carriage is installed with the possibility of displacement along rod axis, and carriage comprises the first element with the first V-shaped guides and the second element with the second V-shaped guides. At that the first and second V-shaped guides are conjugated with rod of square section and spring-loaded relative to it, and also control unit connected to piezoelectric modulus. The first and second carriage elements are additionally connected by flat springs, which are installed parallel to axis of carriage displacement.

EFFECT: improved stability of displacement step, and higher reliability of device.

6 cl, 4 dwg

Description

The invention relates to devices for the mechanical movement of objects along one coordinate. It can be used, for example, in a scanning probe microscope (SPM) to bring the probe and sample closer together.

Known linear inertial stepper motor containing a base on which three piezotubes are fixed at the first ends, at the second ends of which are mounted spherical bearings arranged to interact by means of guides with a movable platform [1].

The disadvantage of this device is that due to the one-sided arrangement of the supports relative to the platform, it cannot be used for vertical movement of objects.

An inertial stepper motor is also known, comprising a base with a piezoelectric module mounted on it, connected to a square rod, on which a carriage is mounted to move along the axis of the rod, consisting of a first element with first V-shaped guides and a second element with second V-shaped guides while the first and second V-shaped guides are paired with a square rod and spring-loaded relative to it, as well as a control unit connected to the piezoelectric module [2].

This device is selected as a prototype of the proposed solution.

The first disadvantage of this device is that the carriage elements are not fixed relative to each other along the axis of movement, which can lead to instability of the movement step and, accordingly, an increase in error, as well as reduced reliability in extreme conditions: such as high vacuum and low temperatures.

The second disadvantage is the lack of tools to combat the sticking effect in high vacuum (due to an increase in the friction coefficient of rubbing surfaces), as well as the freezing of rubbing surfaces at low temperatures. It also reduces reliability and leads to instability of the movement step.

The technical result of the invention is to increase the stability of the move step, as well as to increase the reliability of the device.

The specified technical result is achieved by the fact that in an inertial stepper motor containing a base, with a piezoelectric module mounted on it, connected to a square rod, on which a carriage is mounted that can be moved along the axis of the rod, consisting of the first element with the first V-shaped guides and the second element with second V-shaped guides, while the first and second V-shaped guides are paired with a square rod and spring-loaded relative to it, as well as the control unit, connected to the piezoelectric module, the first and second carriage elements are additionally connected by plane springs located parallel to the axis of movement of the carriage.

There is an option in which the stepper motor is equipped with a carriage movement sensor and a carriage start-up module.

There is also an option in which the carriage extreme position sensors are introduced into the stepper motor.

A variant is possible where the piezomodule is fixed on the base and the rod by means of, respectively, the first four grippers made in the base and four second grippers made on the rod.

A variant is also possible in which a latch is mounted on the carriage or base, which is arranged to interact with the base or carriage, respectively.

Figure 1 shows a stepper motor - side view.

Figure 2 - stepper motor - top view.

Figure 3 shows the fastening of the piezoelectric module to the base and the rod.

Figure 4 shows the grips of a stepper motor.

The stepper motor comprises a base 1 (FIG. 1, FIG. 2) with a piezoelectric module 2 mounted on it, connected to a square rod 3. A carriage 4 is installed on the rod 3, consisting of the first element 5 with the first V-shaped guides 6 and the second element 7 with the second V-shaped guides 8. Moreover, the V-shaped guides 6 and 8 are paired with the rod 3 [3]. Flat springs 9, 10, 11 and 12 are fixed to the elements 5 and 7, interconnected by adapters 13. It is important that the flat springs 9, 10, 11 and 12, in addition to the possibility of functional bending, also have the possibility of torsion. For this, it is necessary that, with the size of the working parts A of about 5 mm, the thickness of the springs is about 0.1 mm. This can also be done by performing springs - joints (not shown) in the working parts of the springs. Thanks to the torsion of the springs, a more uniform clamping of the rubbing surfaces is ensured.

On the base 1, a rod 14 is mounted on which a limiter 15 is located, located in the hole 16, for example, of the first element 5. Moreover, the limiter 15 is able to interact with the carriage 4. The piezoelectric module 2 is connected to the control unit 17. The stepper motor contains a motion sensor, consisting of from a fixed part 18, mounted, for example, on the base 1, and a movable part 19 mounted on the carriage 4. Moreover, they (parts) are connected to the motion blocking module 20, which is part of the block 17. The motion sensor can be made in the form of a capacitance Nogo or inductive displacement meter (see., e.g., [4, 5, 6]). Block 17 introduces a motion start module 21, made in the form, for example, of a sinusoidal voltage generator with adjustable frequency and amplitude [6, 7].

There is an option in which, for example, contact sensors 22 and 23 of the extreme position [6] of carriage 4 are introduced into the stepper motor, and into the control unit 17, a power supply disconnection module 24, made in the form of an electronic or electromechanical power voltage interrupter [6].

Elements 5 and 7 can be additionally spring-loaded relative to each other by springs 25 mating with screws 26.

A possible option of fixing the piezoelectric module 2 on the base 1, using the first four capture 27 (figure 3). The thickness B of these grips can be 0.1-0.2 mm, and the piezoelectric module 2 is fixed by means of the first adhesive joint 28.

The fastening of the rod 3 on the piezomodule 2 can be carried out using four second grippers 26 and a second adhesive joint 30.

There is an option in which the coefficient of friction between the rod 3 and the V-shaped guides 6 and 8 have different values in different directions of movement of the carriage 4. This is achieved by the directed formation of microroughness 31 on their surfaces.

There is also an option in which, for example, on the base 1, a latch is made, made in the form of stops 32 (Fig. 4) with friction pads 33 fixed to elastic elements 34. In this case, friction pads 33 are paired with the first 5 and second 7 elements.

The device operates as follows. A sawtooth voltage is supplied from the control unit 17 to the piezoelectric module 1, which changes its linear dimensions in different directions along the Z axis with different speeds. In this case, the carriage 4 moves along the rod 3 along the Z axis in one direction or another. For more information on inertial displacement, see [8, 9]. In the event that the motion sensor does not detect the movement of the carriage 4, include a module 21, which, swinging the carriage 4 at the resonant frequency, starts its movement. Upon reaching the carriage 4 of one of the extreme positions, which is recorded by the sensors 22 and 23, the module 24 disconnects the supply voltage.

To adjust the interaction force between the V-shaped 6 and 8 guides and the shaft 3, flat springs 9 and 10, as well as springs 25, are used.

To increase the force, reduce the thickness of the adapters 13, or tighten the screws 25.

The selection of the necessary coefficient of friction is carried out by directional grinding of the surfaces of the V-shaped guides 6 and 8, as well as the rod 9. After that, graphite lubricant is introduced into the micro-cavities of these surfaces.

When operating a stepper motor using a clamp, an important point is the adjustment of the stops 32. This adjustment can be carried out by bending the elastic elements 34. It is necessary to ensure that, while maintaining the possibility of movement, the nonfunctional vibrations of the carriage 4 on the shaft 3 in the plane perpendicular to the coordinate Z .

The use of flat springs stabilizes the position of the first and second elements relative to each other along the Z axis, which increases the stability of the step of moving the carriage and the reliability of the device.

The supply of a stepper motor with a carriage motion sensor, a carriage start-up module, and carriage extreme position sensors increases the reliability of the device.

The use of grippers on the base and the rod to secure the piezoelectric module increases the reliability and durability of using a stepper motor.

The use of a latch located with the possibility of interaction with the base or carriage reduces non-functional vibrations of the carriage, which reduces the error of movement.

LITERATURE

1. Patent RU 2152103, 1996.

2. Googl, Attocube systems AG Inertial motor Driving controller ANC 150.

3. Patent EP 0823738, 1997.

4. G.F. Afanasyev, A.N. Eremin, Improving the accuracy and resolution of capacitive and inductive sensors. Sensors and Systems Magazine, No. 6, pp. 17-19, 2003

5. D.I. Ageykin, E.N. Kostina, N.N. Kuznetsova, Control and regulation sensors. M., 1965

6. V.A. Dolgov, A.V. Kedin, Electronic sensors for automatic control systems. M., 1968

7. G.Ya. Mirsky, "Electronic Measurement". M., "Radio and Communications", 439 pp., 1986

8. Probe microscopy for biology and medicine. V.A. Bykov et al., Sensory Systems, vol. 12, No. 1, 1998, pp. 99-121.

9. Scanning tunneling and atomic force microscopy in surface electrochemistry. Danilov A.I., Advances in Chemistry, 64 (8), 1995, p. 818-833.

Claims (6)

1. An inertial stepper motor containing a base with a piezoelectric module mounted on it, connected to a square rod, on which a carriage is mounted that can be moved along the axis of the rod, consisting of a first element with first V-shaped guides and a second element with second V-shaped guides while the first and second V-shaped guides are paired with a square rod and spring-loaded relative to it, as well as a control unit connected to the piezoelectric module, the first and second elements of the car The grids are additionally connected by flat springs located parallel to the axis of movement of the carriage. 2. The device according to claim 1, characterized in that it is equipped with a carriage movement sensor. 3. The device according to claim 1, characterized in that it contains a module for starting the movement of the carriage. 4. The device according to claim 1, characterized in that the sensors of the extreme position of the carriage are introduced into it. 5. The device according to claim 1, characterized in that the fastening of the piezoelectric module on the base and the rod is carried out by means of, respectively, the first four captures made in the base, and four second captures made on the rod. 6. The device according to claim 1, characterized in that a latch is mounted on the carriage or base, located with the possibility of interaction with the base or carriage, respectively.

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