Microwave based position measurement system for an electrodynamic direct drive

The invention relates to an electrodynamic direct drive, in particular a linear drive with a movable within a housing rotor which is movable relative to the housing by a drive system which has two drive-interacting, relatively movable drive means in the form of at least one coil comprising coil system and at least one permanent magnet having magnet system containing, to move an input coupled to the rotor Lastmitnehmer.

The <patcit id="pcit0001" dnum="DE19853942C1"><text>DE 19853942 C1</text></patcit> shows a generic linear drive with a housing defining a receiving chamber, are arranged in the drive means. The drive means are part of an electric linear motor which is used as a cartridge-like unit in the receiving space and fixed to the housing. The housing here limits the elongated receiving space within which the drive means are provided. Through electric power supply can move the rotor within the receiving space along the longitudinal axis. With the rotor an Lastmitnehmer is connected, to which a component is mounted to be moved. This is to be moved by the linear motor or linear drive component may for example be a guide carriage of a machine tool.

From the <patcit id="pcit0002" dnum="DE20113014U1"><text>DE 20113014 U1</text></patcit> discloses an electrodynamic linear direct drive. This direct linear drive comprises an elongate housing with a extending in the longitudinal direction of the housing receiving space. Within the housing is an elongate stator in the form of a hollow support tube is arranged on the ring-shaped permanent magnets are arranged coaxially in succession. To act as a return path direction, the elongated stator made of magnetically conductive material may consist, in particular of soft magnetic material. movably on this stator, the rotor is provided with a coil winding. When current is applied to the coil of the rotor can move the rotor relative to the stator in the longitudinal direction of the housing and takes up about the Lastmitnehmer the displaceable component with.

For the electrical control of the electro-dynamic direct drive, it is important to know the position of the rotor and hence also of the fixed thereto over the Lastmitnehmer component. So far, a relative zero point is fixed to the rotor, with respect to the absolute position of the rotor is determined in the operating mode. Such measuring methods are time consuming and require the use of additional personnel, since the position of the rotor must be adjusted or calibrated with respect to the zero point again.

In <patcit id="pcit0003" dnum="US5257014A1"><text>US 5257014 A1</text></patcit> is a generic linear drive disclosed, having a cylindrical housing, which comprises a driving coil and a movable coil in the rotor. The magnetic field generated by the drive coil can be detected with a magnetic field sensor, whose output signal is a measure of the position of the rotor.

There have been already tried various Wegmessverfahren that enable automatic position measurement of the rotor relative to the housing, the use of distance measurements due to electromagnetic waves such as microwaves, radar waves or the like, so far out of the question, since the coils and permanent magnets within the housing have a magnetically conductive surface, along which run the electromagnetic waves and therefore make a position measurement impossible or interfere significantly.

From the <patcit id="pcit0004" dnum="WO9931463A"><text>WO 99/31463</text></patcit> described a distance measuring apparatus and method for determining the distance of a piston within a cylinder. The distance measuring device has a sensor on for example, a microwave sensor that can determine the position of the piston due to the reflection of the microwaves. In contrast to electro-dynamic linear direct drives, the surface of the cylinder and piston already per se has a surface which is not influenced in such a way, the electromagnetic waves that an accurate measurement is not feasible. The cylinder on the inside, for example, of an electrically conductive material or of a plastic, so that a measurement with electromagnetic radiation does anyway. But as soon as magne-table conductive surfaces come as the electrodynamic direct drive to the game, is not yet possible, such a displacement measurement.

The object of the present invention to provide an electrodynamic direct drive with an alternative position measuring system, which is to be mounted easily on direct drive and brings a considerable economic advantage, since the absolute position of the rotor can be electronically processed in the control and regulation system.

This object is solved by the features of independent claim 1. Thereafter, a path measuring space is formed by an end surface of the movable rotor and the walls of the housing and / or the surface of the inside drive means, and a sensor detects the position of the rotor within the housing by means of electromagnetic waves, whereby the removal of the rotor to the sensor due to the maturity of electromagnetic waves can be measured and the end face of the rotor and the inner surfaces of Wegmessraums having an electrically conductive surface material, in order to guarantee a reflection surface for an optimum measurement function of the microwave sensor.

The Mikrowellenwegmesssystem invention can be preferably electrodynamic linear direct drive motors use, but is not limited to this. For example, also electrodynamic direct drive motors can be used, where the runner can be moved is not in a linear direction, but according to a curvilinear path. The decisive factor is only that the drive means comprise a coil system and to electromagnetically koppelndes magnet system. Based on the linear motor drive are usually several coaxially consecutive coils in the coil system included, and a permanent magnet armature moves relative to the stator given by the coil system. On the other hand can also be arranged, the coil system on the rotor and the stator is formed by a plurality of coaxial successive permanent magnets.

Both alternative drive systems are preferably each encapsulated within a housing, and between an end face of the rotor and an end-side housing wall a path measuring space is formed. According to the invention, limited by the housing itself or the driving means and the end faces of the housing or the end faces of the rotor path measuring space is now characterized by an electrically conductive surface. Especially where magnetically conductive materials are arranged, a reflecting surface is provided which is electrically conductive. By means of this reflection surface from about the microwave sensor incoming microwaves are not coupled into the surface but reflected back into the path measuring space. Characterized occur no or only small measurement errors.

The reflection surface may be provided in different ways. It can be either an electrically conductive metal tube, which is inserted on the inside of the housing or on the drive means or within the drive means. The electrically conductive metal tube has two functions, because it serves both as a sliding surface for the rotor and the other part as electrically conductive reflective surface of Wegmessraums. The reflection surface can also be simply provided by a surface coating of electrically conductive material. The reflection surface is formed such that, also an electrically conductive material is applied on the end faces of the rotor, which limit the path measuring space. In addition to training as a metal tube or surface coating, however, a hollow body can be provided which limits the path measuring space in a form differing from the tubular shape. This hollow body would then be adapted to the path measuring space is formed by the drive means or the housing wall.

The microwave transmitter is arranged inside the housing and oriented so that the emitted therefrom microwaves are directed to the end faces of the rotor, and also of the microwave sensor can be arranged within the housing to detect the light reflected by the end faces of the rotor microwaves. Preferably, the microwave sensor is integrated with the microwave transmitter formed. This allows the transmit / receive module in the narrow path measuring space within a cartridge linear motor easily integrated. Such a transmitter / receiver module could also be retrofitted to existing cartridges linear motors. The end faces of the rotor, on which impinge the microwaves by the alignment of the microwave sensor are preferably designed planar. Thus, the microwaves are reflected back to the transmitter / receiver module. Alternatively, if the microwave sensor comprises a deviating from the microwave transmitter position within the housing of the electro-dynamic direct drive, the end face of the rotor can also have an appropriate surface design, so that the reflected electromagnetic microwaves are reflected towards the sensor.

The path measuring space within the housing is formed for example by an electrically conductive metal tube on the inner side of the coil system and the quasi planar end surface of the rotor, so that the reflection of the microwaves in a linear direction from the microwave transmitter to the end face of the rotor and return to the microwave sensor can take place. By the term measurements of the transit time a precise absolute position detection of the rotor is possible.

The microwave transmitter and the Sender are designed such that they operate in a frequency range of 1 to 60 GHz. Microwaves according to this description relate to at least one frequency range of 1 to 60 GHz.

The electrically conductive surface material on the inner surfaces of the Wegmessraums and / or on the surface of the drive means is a metallic coating or a metallic shielding surface. The metallic coating or the screening surface have preferably aluminum or nickel constituents. It is a hollow conductor is provided, for example, limits the path measuring space and consists of a nickel alloy or is coated with a nickel surface layer. On the other hand, by a waveguide made of aluminum profile, which is provided to the moving rotor and within the housing, also an electrically conductive path measuring space can be provided which reflects the microwaves in reflection toward the microwave sensor out.

In a further development of the invention the metallic reflection surface is a hollow conductor or a thin-walled metal tube, which screens the drive means at the surface to the path measuring space and thereby allows the electromagnetic coupling of the direct drive for driving the rotor. Specifically, the hollow conductor or the thin-walled metal tube simultaneously forms a guide bush for the rotor, whereby it is slidably movable in the longitudinal direction of the housing on the surface of the other drive means.

The microwave sensor preferably detects the absolute position of the rotor within the housing and is coupled to an electrical or electronic evaluation unit to evaluate the position for controlling or regulating the direct drive. The microwave sensor allows the distance measurement of the rotor relative to the microwave sensor and the absolute position of the rotor can be uniquely determined with knowledge of the total displacement distance of the rotor. This allows the position of the rotor attached to the component to determine what can be easily used also for controlling or regulating the position of the component.

In one development of the invention, the rotor is designed as a permanent magnet and a stator having coaxially successive coils linearly movable. On the coil windings a sliding surface for the rotor is provided, which simultaneously provides a part of the metallic reflection surface for the path measuring space. For example, when the electrodynamic direct drive is embodied in a cartridge design, it can be formed in very small build construction manner. The housing itself forms a magnetic yoke within which the coil windings are arranged on an electrically conductive coil carrier.

Inside on the coil surface is provided a reflection surface for the path measuring space.

In an alternative embodiment of the invention the rotor is fitted by means of several axially wound coil windings or with a plurality of coaxially arranged coils. The armature is movably supported on a longitudinal stator to be movable in the longitudinal direction of the housing. The stator has a plurality of, arranged in the longitudinal direction of the housing coaxially with the magnet, so that the rotor after electric power supply is movable relative to the stator.

In this development, the path measuring space between the surface of the stator and the inner surface of the housing and the end surfaces of the housing and the rotor is formed. Particularly in the magnetic stator which is a part of the drive means, either an electrically conductive hollow body or an electrically conductive surface has to be deposited to form a reflecting surface for microwaves. In addition, an electrically conductive surface is provided on the end face of the rotor. However, it can also be provided that the rotor itself is electrically conductive, whereby no additional surface on the rotor in the area of ​​the end surface has to be applied.

It must be ensured only by virtue of the present invention that the surfaces of the Wegmessraums consist of electrically conductive materials or are equipped with electrically conductive reflecting surfaces. This is a distance measurement by means of electromagnetic waves, in particular by means of microwaves, does not interfere, because the electromagnetic waves are reflected to the distance measuring sensor out.

Several embodiments of the invention are presented in the claims and the following description, show it, each in schematic representation:<dl id="dl0001"><dt>Fig. 1</dt><dd>an electrodynamic direct drive with a permanently magnetic rotor and a microwave sensor for determining the position of the rotor according to a first alternative of the present invention, and</dd><dt>FIG. 2</dt><dd>an electrodynamic linear direct drive motor. cartridge type having a microwave sensor for determining the position of the rotor according to a second alternative according to the present invention</dd></dl>

The electrodynamic direct drive is provided in an embodiment of a linear motor cartridge type, which within a housing 1, a magnetically conductive rotor 2 is provided, which is axially movable within the housing. 1 For the linear motor is a two part drive system 3 is provided having a plurality of coaxially consecutive coils 4 as the first part. The coils 4 are arranged on an electrically conductive coil carrier sixteenth On the outer side of the rotor 2, a permanent magnet 5 is provided which provides the other of the two relatively movable drive means parts.

The rotor 2 is connected to a rod-like Lastmitnehmer 6 in order to move the displaceable component. The runner 2 slides in a longitudinal movement inside the housing 1 on the inner surface of the coil system 4, whereby a guide is formed within the stator acting as a coil system 4th

Within the housing, a microwave transmitter 7 is provided, the microwaves on the rotor 2 8 9 emits in the direction of one end face and the end face 9 reflektiertten of these microwaves 10 detected by the microwave integrated sensor eleventh

Within the housing 1 of the electro-dynamic drive, a direct path measuring space 12 is formed, which is delimited by different reflection faces. These reflecting surfaces are all electrically conductive, that is covered in the case of permanent-magnetic end surface 9 of the rotor 2 with an electrically conductive surface 13, or formed by a tubular hollow body 14, which forms an electrostatically conductive sliding surface. This sliding surface of the electrostatic hollow body 14 of the rotor 2 can slide. The electrically conductive material of the hollow body 14 is designed so thin that the electromagnetic coupling between the rotor 2 and the coil system 4 is minimum disturbance. In addition, even on the end face 15 of the housing inside an electrically conductive surface may be provided, but this is not essential for the invention.

The linear motor works as follows: If the coil system 4 is appropriately energized by an electrical drive circuit, the rotor is 2 due to the electromagnetic coupling between the two drive means, that is the coil system 4 and the magnet system 5, in the longitudinal direction of the housing 1 in movement. If the current flow is reversed through the coils 4, the rotor 2 and thus also the Lastmitnehmer 6 moves with the attached part of the machine tool in the opposite direction.

The transmitter 7 transmits the microwaves 8 in the direction of end face 9 of the rotor 2, and the reflected microwaves 10 are recorded in the microwave sensor 11 and evaluated in the regulatory or control circuit of the linear motor. This allows the linear motor drive accurately, and the distance measurement can be performed automatically.

The path measuring space 12 within which the microwaves 8, 10 to the end face 9 of the rotor back and move it back away from the sensor 11 is provided according to the present invention with electrically conductive surfaces. Either the materials as in the coil system 4 is already made of electrically conductive metal, or it is provided on the inside of the drive means, a hollow body 14, which increases the electrical conductivity. In particular an electrically conductive surface 13 is provided at the end face 9 of the permanent-magnetic rotor 2, whereby the microwaves 8, 10 can not be attenuated in the magnetic conductive surface.

In FIG. 2, a further electrodynamic direct drive in the form of a linear motor is shown with a movable armature 2, which is coupled via a Lastmitnehmer 17 with a movable member. The driving means 3 of the rotor 2 is wound on a coil bobbin of the rotor 2 coil 18 which is electrically controllable. The runner 2 slides on a stator 19 arranged coaxially with it, the permanent magnet. The housing 1 is made of an electrically conductive material, which forms a magnetic yoke.

Within the casing 1 of the microwave transmitter 7 for transmission of the microwaves 8 in the direction of the end face 9 of the rotor 2 is provided, and the microwaves 10 are reflected from the end face 9 of the rotor 2 to the microwave sensor eleventh In this way, the absolute position of the rotor 2 within the housing 1 can be measured accurately. Since the stator 19 is provided with coaxial permanent magnets, an electrically conductive surface is provided over this, which consists for example by a thin coating of electrically conductive material twentieth Alternatively can be used as electrically conductive surface also arranged one above the stator 19 aluminum tube. The end face 9 of the rotor 2 can also be provided with an electrically conductive layer. 13 Since the housing 1 itself is made of electrically conductive material, the surface is electrically conductive so that no additional action is required here.

By forming the Wegmessraums 12 with the electrically conductive surfaces of the microwave sensor can operate and measure the exact position of the rotor 2 without excessive attenuation or disturbance. Thereby a MikrowellenWegmesssystem can be used effectively in an electrodynamic direct drive with a permanent drive means for the first time.