DE102010054603B4 - Electro-mechanical angular position control device - Google Patents

Abstract

Electro-mechanical angular position control device for position-stabilized camera platforms in airborne ground observation, comprising a stepper motor (4) having a stator (2) and rotor (3), an angle sensor (5) connected to the stepper motor (4) and an angle sensor (5) ) connected digital control electronics (6) which controls the stepping motor (4) in response to the signal of the angle sensor (5), wherein the stator (2) of the stepping motor (4) has a soft magnetic smooth ring (14) for guiding the magnetic flux and the soft magnetic Glattring (14) has a ring chain (22) of field coils (13) with axial conductor direction in the air gap (23) between the stator (2) and the rotor (3).

Description

The invention relates to an electro-mechanical angular position control device, in particular for position-stabilized camera platforms in airborne ground observation.

Such camera platforms are usually stabilized by at least two spatial axes of rotation. Each of these axes of rotation is stabilized by means of a control device by angular position sensors and / or angular velocity sensors determine the actual movement relative to the inertial space or against a carrier aircraft, an electronic position controller the actual movement (controlled variable) with the predetermined target movement (command variable) compares and determines therefrom Stellbefehle (manipulated variable) for an electromagnetic actuator, which then performs this actuator. This makes it possible to keep the camera platform stable.

As a servo or rotary drives are usually used DC motors with gear reduction or stepper motors, the latter usually come in gearless direct drive used.

A disadvantage of both conventional drive forms in use for position-stabilized camera platforms that unavoidable strong idle moments are present in the de-energized state. In the case of the aforementioned DC motor, this is the holding torque of the transmission, in the case of the aforementioned stepping motor to the design-related Polastastung between the stator and rotor. These quiescent moments mean that the corresponding drives must always be actively operated with high accuracy, since otherwise the idle moments would change the position of the camera platform immediately.

Another technical possibility for the formation of such drives is to use suitable, quiet torque-free AC resolver for this application. These are usually used without gears. They are available as torque versions. Although these resolvers usually have a three-phase pole structure; However, no Polrastmomente occur through the use of exclusively soft magnetic materials. The only moments of rest are frictional moments of the axle bearings, which are usually designed as a miniature ball bearings, and designed as spring wires contact brushes of the rotor.

A disadvantage is that resolvers are highly accurate and therefore costly analog components that can be further adapted only by means of complex signal converter to digital data processing processes. For this reason, resolvers are practically no longer used today.

For example, an electro-mechanical angular position control device for camera platforms in airborne ground observation is off US 2004/0173726 A1 known. The drive motors are not disclosed here.

From the DE 28 05 363 C2 a device for the controlled control of a stepping motor is known, which is a control with a stepping motor as an actuator, a coupled angle sensor as a measuring sensor and an evaluation circuit for determining the control deviation. The stepping motor described here has the property of executing a damped oscillation each in stepwise switching as shown in FIG 5 This font is shown.

This oscillation must have subsided before the measurement of the control deviation, which is realized according to this document by waiting times in the algorithmic sequences. The example of this font shows a cross-over projector for displaying the location in a topographic map. To avoid step losses, the stepper motor is usually kept energized for the task mentioned in this document usually. An operating state without current supply and, moreover, with missing cogging torque is not desirable here, because then disturbance torques can easily lead to movements of the stepping moment which correspond to non-activated pulses.

From the US 4,645,961 A. So-called Hall sensors are known for generating signals for the control of the rotation phase-correct pole change to the stator coils (commutation). This is referred to as a possible modification of an exemplified procedure. This operation is concretized by a five-segment commutator connected to a pair of contact brushes. In this one-magnetic-pole pair arrangement, a certain coil energization corresponds to an angular position in the range 0 ° to 360 °. In a more than two-magnetpolpaarigen arrangement, the Bestromungsfolge repeats for each pair of poles. But with an N-magnetpolpaarigen arrangement over the circumference 0 ° to 360 °, the angular position at a given energization is N-times ambiguous. In order to establish a uniqueness for the range 0 ° to 360 °, a zero mark (N) is required and usually provided in incremental angle encoders.

The invention has for its object to provide an electro-mechanical angular position control device of the type mentioned above, which is more economical to operate and in particular the control of the position stabilization is simplified.

This object is achieved by an electro-mechanical angular position control device with the features of claim 1. Advantageous developments are the subject of the dependent claims.

The electro-mechanical angular position control device has a stator and rotor stepper motor, an angle sensor connected to the stepper motor, and a digital positioner connected to the angle sensor that drives the stepper motor in response to the signal from the angle sensor. The stator of the stepping motor is formed to have a soft-magnetic smooth ring for guiding the magnetic flux. Such a stepper motor has the considerable advantage that it does not exert any idle moments when de-energized and can be easily integrated into digital control systems. In this respect, according to the invention, a soft-magnetic smooth ring is used instead of the pole comb of the stator, which is customary in stepper motors, on the stator. This has in contrast to a commonly used Polkamm on no Polastron. This results in the particular advantage that in the angular position control device according to the invention the inertial, given by its moment of inertia Lagebeharrungsvermögen the camera platform for the position stabilization is available. As a result, the passive-inertial position stabilization of the camera platform can be used physically in the device according to the invention. The reduction in torque, which eliminates the pole comb, does not pose a problem for the position stabilization of camera platforms since only small torques are required for this in any case. In this respect, the regulation to be carried out by the regulating device is much simpler and more economical to carry out. The inertia of the camera platform can thus be used for their position stabilization. According to the invention, the stator of the stepping motor on the soft-magnetic smooth ring on a ring chain of field coils with axial conductor direction in the air gap between the stator and the rotor. As a result, the torque in the direction and magnitude according to digital grading can be set quasi-steadily, whereby the control can be refined and thereby improved.

According to an advantageous development, the stepper motor is a flat rotary drive and designed as an internal rotor or as an external rotor, preferably as a two-phase external rotor. Such a stepper motor requires only little space and has only a low weight, so that thereby the economic use of the control device according to the invention can be further improved.

According to another embodiment of the invention, the angle sensor is a digital angle encoder, which is preferably integrated as an optical or magnetic angle encoder in the stepper motor, that on the rotor, an optical or magnetic encoder disc and read out on the stator photocells or magnetic field sensors are provided. This creates an extremely compact control device, which has only a small footprint. This development also contributes to the improvement of the economic use of the control device according to the invention.

Embodiments of the subject invention are explained in more detail with reference to the drawing, wherein all described and / or illustrated features alone or in any combination form the subject matter of the present invention, regardless of their combination in the claims or their dependency. Show it:

1 a partial perspective, schematic view of an electro-mechanical angular position control device;

2 a partial cross section through a stepper motor of the control device; and

3 a longitudinal section through the stepping motor along a line III-III in 2 ,

In 1 is a partially perspective schematic view of an electromechanical angular position control device 1 especially for position-stabilized (not shown in detail) camera platforms shown in the airborne ground observation.

The control device 1 has a stator 2 and rotor 3 having stepper motor 4 , Furthermore, the control device has 1 one with the stepper motor 4 connected angle sensor 5 and one with the angle sensor 5 Connected digital control electronics 6 , The adjusting electronics 6 controls the stepper motor 4 depending on the signal of the angle sensor 5 at. angle sensor 5 and control electronics 6 are via a signal line 7 connected with each other. A power line 10 connects the control electronics 6 with the stepper motor 4 , A preferably digital, alternatively also analogue control signal 11 becomes the control electronics 6 supplied externally. The stepper motor 4 is the rotor side over the axis of rotation 12 coaxial with the angle sensor 5 connected. In this respect, the output signals of the angle sensor 5 over the signal line 7 to the control electronics 6 guided. The control electronics in turn leads over the power line 10 the coil currents at field coils 13 of the stepper motor 4 , The field coils 13 will be explained in more detail below.

The structure of the stepper motor 4 is more accurate in the 2 and 3 shown, where 2 a schematic, partial cross section through clarifies the stepper motor and 3 a longitudinal section along the line III-III in 2 shows.

The stator 2 of the stepper motor 4 has a soft-magnetic smooth ring 14 for guiding the magnetic flux.

With the cylindrical inner circumference 15 of the Glatring 14 is a carrier body 16 connected, which according to 2 cruciform with carrying arms 17 and shell-shaped support surface 20 is trained. About the support surface 20 is the carrier body 16 with the smooth ring 14 connected. The smooth ring sits, as shown, circumferentially on the carrier body 16 ,

The stepper motor 4 is a flat rotary drive 21 and designed as an internal rotor or as external rotor. According to a particularly preferred embodiment of the invention is the stepper motor 4 , as shown, formed as a two-phase external rotor.

The stator 2 of the stepper motor 4 has at its soft magnetic smooth ring, more precisely on the outer surface, a ring chain 22 from the field coils 13 with axial conductor direction in the air gap 23 between stator 2 and rotor 3 on.

The angle sensor 5 is a digital angle encoder according to a preferred embodiment of the invention. The angle encoder is in such a way not shown in the stepper motor according to a particularly preferred embodiment of the invention as an optical or magnetic angle encoder 4 integrated, that on the rotor an optical or magnetic encoder disc and on the stator reading light barriers or magnetic field sensors are provided.

Radial to the stator 2 closes towards the outside of the rotor 3 like this 2 and 3 can be seen. The rotor 3 has radially outward lying a soft magnetic smooth ring 24 , in the inside permanent magnets 25 in alternating radial polar direction, NS alternating with SN, are used. The polarity of the two within an in 2 shown step cycle 26 shown permanent magnets 25 is shown as an example.

The stator 2 points next to his smooth ring 14 as previously mentioned, the alternating field coils 13 on which according to 2 are designated by different hatching. These field coils 13 are outside on the soft magnetic smooth ring 14 lined up. Each field coil 13 has an element that flows into the drawing plane with electricity 27 and an element flowing out of the plane of the drawing 30 , The current direction applied to the plane of the drawing is symbolized by "+"; the direction of flow coming out of the drawing plane is symbolized by "·".

The bold hatched elements 27 and 30 thus form a common field coil 13 , Likewise, weakly hatched elements form 31 and 32 a field coil 13 , 2 that shows up between the elements 27 and 30 a field coil an element 31 another field coil. 2 also shows that between the elements 31 and 32 (weakly hatched) a field coil an element 30 another field coil. In this respect is located within the in 2 shown step cycle 26 a bold hatched field coil with the elements 27 and 30 and a weakly hatched field coil with the elements 31 and 32 ,

It is clear that the entire outer circumference of the Glatring 14 of the stator with the field coils 13 is provided, as described, elements of different field coils alternate with each other. The adjacent elements 27 and 31 different field coils 13 are like 2 illustrates, in the current direction "+" leading into the plane of the drawing, the adjoining elements 30 . 32 The two aforementioned field coils are in turn in the same direction, this time out of the plane and therefore marked with "-", with current flowing through.

3 further shows that each field coil 13 U-shaped, with legs 33 . 34 each field coil over the smooth ring 14 in the radial direction to the carrier body 16 extend.

As previously mentioned, the stepper motor is 4 according to 2 in the design as a two-phase external rotor, ie with external rotor 3 and inside stator 2 , educated. The stepper motor shown here by way of example has sixteen step cycles distributed over its circumference 26 , The number of permanent magnets 25 over the circumference corresponds twice the number of field coils over the circumference in each phase. In each phase are according to the embodiment, sixteen field coils and 32 permanent magnets before. The illustrated embodiment with sixteen step cycles 26 Therefore has 32 permanent magnets and sixteen field coils for each phase, which can be connected in series or in parallel. The course of the current-carrying core of the field coils 13 of the stator 2 in the air gap 23 to the rotor 3 is directed in the axial direction, so that the electromotive force produced by the radially acting magnetic field acts in the circumferential direction and generates a torque.

In this respect, a stepper motor with a ring-like, permanent-magnetic rotor is provided by the current switching in the field coils 13 a likewise ring-like stator 2 one common rotational symmetry axis is moved or set under torque about this axis. The angle sensor 5 is an electronic angle sensor. The digital control electronics 6 controls the field coils 13 of the stator 2 of the stepper motor 4 as previously indicated, according to externally given commands or signals, taking into account the signal of the angle sensor and optionally further position sensors.

It is clear that in a design of the stepping motor as a so-called internal rotor, the stator is arranged radially outside and that in a design of the stepping motor as a so-called external rotor of the stator is arranged radially inward.

It is also possible to arrange stator and rotor axially in series. Due to the large and structurally (especially in bearings) magnetic attraction forces between the stator and the rotor, which are effective axially in such an arrangement, such a construction can have advantages in exceptional cases. As a rule, the radial arrangement described and illustrated here is advantageous, since in this case the forces of attraction between the field coils and the permanent magnets cancel out over the circumference and otherwise act only as material-internal tensile stresses.

The angle sensor 5 For example, an absolute angle encoder or an incremental angle encoder may usually be with additional digital step counter electronics. As previously indicated, the angle sensor may be externally coaxial or integral with the design of the rotary actuator. The coil construction of the rotary drive can be two-, three- or multi-phase. For the sake of simplicity is usually a two-phase design, as in the 2 and 3 shown is advantageous.

The control device is constructed so that the digital control electronics, the signals of the angle encoder and optionally other position signals, for example, from the position sensor system of the carrier aircraft with the predetermined command variable (see guide signal 11 ) compares and calculates the required current feed of the coil currents of the rotary drive from it and put into effect.

The rotary actuator can also be operated as a simple stepper motor without position or angular velocity feedback by the field coil currents are controlled "blind" to a fixed timing program.

Trained as a stepper motor rotary drive is operated as a torque sensor whose torque in the direction and magnitude according to digital gradation is quasi-continuously adjustable, regardless of the current angular position or relative phase position of the stator and rotor. For this purpose, the signals of the angle sensor are evaluated in the digital control electronics such that the respectively appropriate for the current angular position, d. H. angularly offset field coil phase is energized in the appropriate polarity. The control of the amount of torque is carried out in an expedient manner by digital pulse width modulation of the field coil currents.

In the de-energized state are the drive side, as mentioned above, only the friction moments of the axle bearings, z. As ball bearings, effective, which are usually negligible in the practice of instrument making. In this way, the passive-inertial stabilization capability of the statically balanced camera platform can be utilized by decoupling the camera platform practically without torque from the rotational movements of the carrier aircraft in the de-energized state and weak correction torque effects of the digital rotary drive being sufficient to compensate for residual misplacements.

When integrated in the stepper motor angle sensor, the optical or magnetic encoder is annular and mounted on the rotor. The angular position of the encoder is, as mentioned, read by mounted on the stator photocells or magnetic field sensors.

The control device 1 is thus characterized by a digital flat rotary drive, which has a ring-like rotor with a ring chain of permanent magnets in an alternating axial polar direction and soft magnetic field closure as a motor part. Coaxial and coplanar with this, the stator is provided with soft magnetic smooth ring and attached ring chain of field coils with axial conductor direction in the air gap between the stator and rotor.

As previously indicated, in the described embodiment, there are ultimately sixteen positions due to the step cycle 26 to disposal. The angle sensor acts as an encoder. The provided in conventional stepper motors for the Feldspulwindungen are not present in the control device according to the invention, so that no torque is applied in the idle state. The usual "latching" in conventional stepper motors does not occur in the control device according to the invention.

Thus, an electro-mechanical angular position control device is provided, which is constructed and operated particularly economical and in particular the control process is simplified.

Claims (5)

Electro-mechanical angular position control device for position-stabilized camera platforms in airborne ground observation, with a stator ( 2 ) and rotor ( 3 ) having stepper motor ( 4 ), one with the stepper motor ( 4 ) associated angle sensor ( 5 ) and one with the angle sensor ( 5 ) connected digital control electronics ( 6 ), which the stepper motor ( 4 ) in dependence of the signal of the angle sensor ( 5 ), wherein the stator ( 2 ) of the stepper motor ( 4 ) a soft magnetic smooth ring ( 14 ) for guiding the magnetic flux and the soft-magnetic smooth ring ( 14 ) a ring chain ( 22 ) of field coils ( 13 ) with axial conductor direction in the air gap ( 23 ) between stator ( 2 ) and rotor ( 3 ) having. Regulating device according to claim 1, characterized in that the stepping motor ( 4 ) a flat rotary drive ( 21 ) and is designed as an internal rotor or as external rotor. Regulating device according to claim 1 or 2, characterized in that the stepping motor ( 4 ) is designed as a two-phase external rotor. Regulating device according to one of the preceding claims, characterized in that the angle sensor ( 5 ) is a digital angle encoder. Control device according to claim 4, characterized in that the angle encoder as an optical or magnetic angle encoder in the stepper motor ( 4 ) is integrated on the rotor ( 3 ) an optical or magnetic coding disc and on the stator ( 2 ) reading photocells or magnetic field sensors are provided.

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