EP4347301A1

EP4347301A1 - Transport device and method for operating a transport device

Info

Publication number: EP4347301A1
Application number: EP22731221.2A
Authority: EP
Inventors: Andreas Weber; Alexander Almeder; Jesper Spanggaard RASMUSSEN
Original assignee: B&R Industrial Automation GmbH
Current assignee: B&R Industrial Automation GmbH
Priority date: 2021-06-02
Filing date: 2022-06-01
Publication date: 2024-04-10
Also published as: CN117529421A; WO2022253883A1

Abstract

In order to enable determination of the position of a transport unit (TE1, TE2) as accurately as possible in a transport device (1) having at least one transport segment (TS) along which at least one transport unit (TE1, TE2) is moved at least one-dimensionally and on which a plurality of position sensors spaced apart from each other in the direction of movement are provided, independently of the input of heat during the operation of the transport device (1), provision is made according to the invention that a plurality of temperature sensors spaced apart from each other in the direction of movement are provided for detecting a local temperature of each transport segment (TS) and/or that a temperature model for calculating the local segment temperatures is stored in the control unit (6) and that the control unit (6) is configured to correct the position of the transport unit by means of a defined correction model on the basis of the determined local segment temperatures in order to incorporate a thermal expansion of the transport segment (TS).

Description

Transport device and method for operating a transport device

The invention relates to a transport device with at least one transport segment, along which at least one transport unit can be moved at least one-dimensionally, a plurality of position sensors spaced apart from one another in the direction of movement being provided on the transport segment in order to generate a sensor signal in each case when the transport unit is in a sensor region of the respective Position sensor is located, wherein a control unit is provided in the transport device, which is designed to determine a transport unit position of the transport unit relative to a fixed reference point of the transport device as a function of the sensor signals received from the position sensors. The invention also relates to a method for operating a transport device with at least one transport segment, along which at least one transport unit is moved at least one-dimensionally, a plurality of position sensors spaced apart from one another in the direction of movement being provided on the transport segment, with the position sensors each generating a sensor signal when the transport unit is moved into a sensor area of the respective position sensor, with a control unit determining a transport unit position of the transport unit relative to a specified reference point of the transport device on the basis of the sensor signals received from the position sensors.

In a linear motor, a primary part (stator) and a secondary part (rotor) are provided, with the secondary part being movable relative to the primary part. Drive coils are arranged on the primary part and drive magnets on the secondary part, or vice versa. The drive magnets are designed either as permanent magnets, electrical coils or short-circuit windings. The drive coils are electrical coils that are energized to generate an electromagnetic field by applying a coil voltage. Due to the interaction of the (electro)magnetic fields of the drive magnets and the drive coils, forces act on the secondary part that move the secondary part relative to the primary part. The linear motor can be designed, for example, as a synchronous machine or as an asynchronous machine. The drive coils of the linear motor are either arranged one behind the other in a direction of movement or in one plane of movement. The secondary part can be moved along this one direction of movement or can be moved at least two-dimensionally in the plane of movement in the two directions of movement. A distinction can also be made between short-stator linear motors and long-stator linear motors, with the secondary part being shorter or smaller than the primary part in the long-stator linear motor and the primary part being shorter or smaller than the secondary part in the short-stator linear motor. Long-stator linear motors are both linear long-stator linear motors with one-dimensional movement of the secondary part in one movement direction and planar long-stator linear motors with at least two-dimensional movement of the secondary part in one movement plane, which are often also called planar motors. In the case of long-stator linear motors, a number of secondary parts are usually moved simultaneously and independently of one another along the primary part (in a direction of movement or in a plane of movement). Long-stator linear motors are therefore often used in electromagnetic transport systems in which several transport units (secondary parts) are moved simultaneously to carry out transport tasks. The primary part (stator) forms a transport section or a transport plane along which the transport units can be moved.

It is also already known to construct a long-stator linear motor in a modular manner. The transport route or transport level (primary part) can be subdivided into several separate elements, which are also referred to below as transport segments. Each transport segment thus forms part of the primary part, it being possible for a specific number of drive coils to be arranged on each transport segment. Individual, preferably standardized transport segments can then be combined to form a transport section or transport level of the desired length and/or shape. For example, WO 2015/042409 A1 shows such a modularly constructed linear long-stator linear motor. US Pat. No. 9,202,719 B1 shows a long-stator linear motor in the form of a planar motor with stator modules.

Power electronics are generally provided for energizing the drive coils, which converts the required electrical manipulated variables of the drive coils, for example a coil voltage, a coil current or a magnetic flux. Electrical components are installed in the power electronics, which are loaded during operation, for example by electrical currents flowing through them. However, the permissible electrical currents are limited by the components and/or the electrical configuration of the power electronics. By energizing the drive coils by applying a coil voltage, heat is also generated at the transport segment, as a result of which the temperature of a transport segment can rise. It is therefore already known to cool the stator of a linear motor. For example, US Pat. No. 5,783,877 A or US Pat. No. 7,282,821 B2 shows cooling of a stator of a linear motor, with lines being arranged in the stator or in a component in contact with the stator, through which lines a coolant is fed. The coolant thus absorbs heat from the stator and dissipates it. In contrast, the cooling of the stator of a long-stator linear motor, which can extend over a great length, is structurally complex and also increases the costs, especially with large stator lengths such as when used as a transport device. Cooling is therefore often not provided for.

The movement of the individual transport units is usually controlled via one or more suitable control unit(s) of the transport device. In this case, for example, permanently specified movement profiles, e.g. a specific path-time profile or speed-time profile, can be implemented in the control unit or e.g. specified by a higher-level system control unit. From this, the control unit calculates suitable manipulated variables for the drive coils, e.g. current, voltage, and controls the drive coils accordingly via the power electronics in order to set, in particular to regulate, the respective movement profile. In this case, one or more suitable controllers can also be provided in order to adjust certain desired values, for example a desired position of a transport unit along the transport route or the transport plane. In order to provide an actual variable required for the regulation, one or more sensors are usually also provided along the transport section or the transport plane.

Suitable position sensors, for example, are often provided, e.g. in the form of known magnetic position sensors, in particular anisotropic magnetoresistive sensors, also called AMR sensors, or tunnel magnetoresistive sensors, also called TMR sensors. With these sensors, the presence of the transport units can be detected without contact when the transport unit or a part of it is located in the sensor area, in particular the magnetic field generated by the drive magnets of the transport unit. Since the installation positions of the sensors relative to a defined reference point of the transport device are generally known, the positions of the transport units can be clearly assigned to the reference point of the transport device or to another known reference point.

During operation of the transport device, different thermal expansions of individual components of the transport device, in particular a transport segment, can occur as a result of the heat input mentioned. Under certain circumstances, this can lead to the position of a transport unit determined by the control unit using the position sensors deviating from an actual position. This can lead to problems, for example, in transport processes in which the movement of the transport units is synchronized with the movement of one or more external devices. For example, it can be provided that an object transported with a transport unit is to be picked up at a predetermined position by a handling device, such as an industrial robot, or an object is to be placed on the transport unit, or an object on a moving transport unit is to be processed during movement target. If the position determination of the If the transport unit and thus the position control are not correct, a position deviation can lead to problems with storage or recording or processing, which is of course undesirable.

It is therefore an object of the invention to provide a transport device and a method for operating a transport device that enable the most accurate possible position determination of a transport unit independent of the heat input during operation of the transport device.

The object is achieved according to the invention with a transport device mentioned at the outset in that a plurality of temperature sensors spaced apart from one another in the direction of movement are provided in the transport device, preferably on the transport segment, for detecting a local segment temperature of the transport segment and/or in that a temperature model for the calculation is provided in the control unit of the local segment temperatures is stored and that the control unit is designed to correct the transport unit position on the basis of the determined local segment temperatures using a predetermined correction model in order to take thermal expansion of the transport segment into account. As a result, the position of the transport unit can be corrected during operation as a function of local thermal expansion of the transport segment, which results, for example, from heat input from the drive coils. As a result, locally different heat inputs and consequently locally different thermal expansions of the transport segment can be taken into account, as a result of which a more precise position correction is achieved. Locally different heat inputs can arise, for example, if the drive coils are controlled individually and are loaded to different degrees. As a result, different thermal expansions at different points of the transport segment can be taken into account in an advantageous manner.

In the simplest case, a characteristic could be stored in the control unit, for example, in which the corrected transport unit position is mapped as a function of the segment temperature. However, a characteristic map could also be stored in which the corrected transport unit position is mapped as a function of the segment temperature and one or more other parameters. The temperature sensors could be arranged directly on the transport segment, for example. However, temperature sensors could also be used, for example, which are arranged at a distance from the transport segment and are suitable for detecting the temperature from a distance, such as infrared sensors.

The correction model preferably contains a temperature-dependent correction factor of the transport segment and the control unit is designed to multiply the determined transport unit position by the temperature-dependent correction factor, to correct the transport unit position. As a result, the thermal expansion is taken into account in a simple manner by a factor that can be determined experimentally, for example.

According to an advantageous embodiment, it is provided that for each of the plurality of position sensors, a sensor position is defined for a predefined reference temperature, that the correction model contains the determination of a sensor offset for each of the position sensors based on the determined local segment temperatures, the reference temperature and a predefined expansion factor of the transport segment, and that the control unit is designed to determine a corrected sensor position for each position sensor based on the determined sensor offsets and to correct the transport unit position based on the corrected sensor positions. As a result, a physical relationship between the thermal expansion as a function of a temperature difference and as a function of an expansion factor can be used to correct the position of the transport unit. In the simplest case, an empirical factor or an experimentally determined factor, for example, can be used as the expansion factor.

At least one of the temperature sensors is preferably arranged in the same position as one of the position sensors on the transport segment and/or at least one of the position sensors and at least one of the temperature sensors are structurally combined. As a result, on the one hand, the temperature can advantageously be measured directly at the location of the position measurement and, on the other hand, fewer sensors are required, which simplifies the design.

It is advantageous if the transport segment has a segment carrier, which is attached, preferably centrally in the direction of movement, to a stationary guide device of the transport device with a fixed bearing with a known attachment position relative to the specified reference point of the transport device, with the plurality of position sensors being arranged on the segment carrier and that the control unit is designed to correct the transport unit position based on the fastening position, in particular to determine the sensor offsets of the position sensors based on the fastening position. This allows essentially free thermal expansion in the direction of movement, which keeps thermally induced stresses low. Because the thermal expansion starts from a known point, a simple two-way position correction can be performed.

At least one stator unit is preferably provided on the transport segment, preferably on the segment carrier, on which a plurality of drive coils are arranged in at least one, one The arrangement direction defining the direction of movement of the transport unit are arranged one behind the other, the drive coils being controllable by the control unit in order to interact electromagnetically with the transport unit to generate a drive force for at least one-dimensional movement of the transport unit in the direction of movement. Alternatively, a stator unit can be provided on the transport segment, preferably on the segment carrier, on which several drive coils are arranged one behind the other in at least two different arrangement directions, each of which defines a direction of movement of the transport unit, with the drive coils being controllable by the control unit in order to move with the transport unit to the Generating a driving force for the at least two-dimensional movement of the transport unit to interact electromagnetically in the two directions of movement. As a result, the position correction can be used both in a long-stator linear motor with a one-dimensional direction of movement of the transport unit and in a planar motor with a multi-dimensional direction of movement.

The plurality of position sensors and/or the plurality of temperature sensors are preferably arranged on a sensor plate running parallel to the transport segment, in particular to the stator unit, in the direction of movement, the sensor plate preferably being arranged on the segment carrier. This simplifies the construction and assembly of the transport segment.

The stator unit is preferably made of a ferrous material with a known coefficient of expansion and/or the segment carrier is made of a material, preferably containing aluminum, with a known coefficient of expansion and the coefficient of expansion of the stator unit and/or the coefficient of expansion of the segment carrier are taken into account in the correction model. As a result, a modular construction of the transport device can be made possible, with an advantageous material being able to be used for each component, the thermal expansion properties of which can be taken into account in the position correction.

According to a further advantageous embodiment, it is provided that the correction model contains the determination of a displacement of the sensor plate based on a temperature of the sensor plate, a displacement coefficient of the sensor plate and the reference temperature, and that the control unit is designed to calculate a total sensor displacement of the sensor plate from the displacement of the sensor plate and the determined sensor displacement determine at least one position sensor and use the total sensor offset to determine the corrected sensor position. As a result, a displacement of the entire sensor plate that is the same for each position sensor can also be taken into account when calculating the corrected transport unit position. Furthermore, the object is achieved by the method mentioned at the beginning in that a local segment temperature of the transport segment is detected by means of a plurality of temperature sensors spaced apart from one another in the direction of movement and/or that local segment temperatures of the transport segment (TS) are determined by means of a temperature model of the transport segment implemented in the control unit. are determined and that the control unit corrects the position of the transport unit on the basis of the determined local segment temperatures by means of a predetermined correction model in order to take thermal expansion of the transport segment into account.

Advantageous developments of the method are specified in the dependent claims 11 to 16.

The present invention is explained in more detail below with reference to FIGS. 1 to 2, which show advantageous configurations of the invention by way of example, schematically and not restrictively. while showing

1 shows a transport device in the form of a long-stator linear motor in a preferred embodiment,

2 shows a transport segment of the transport device in a plan view and in a side view

In FIG. 1, a transport device 1 in the form of a long-stator linear motor (hereinafter LLM) is shown schematically in a view from above. The structure and function of an LLM are well known, which is why only the points that are essential to the invention are discussed in more detail. The transport device 1 has a transport route 2 which is constructed in a modular manner from a plurality of transport segments TS. One or more transport units TE can be moved along the transport route 2 in a known manner by generating electromagnetic forces. For this purpose, a multiplicity of drive coils 4 are arranged one behind the other in a known manner on the transport path 2 in a direction which forms a direction of movement for the transport units TE. A plurality of drive magnets 5 of different magnetic polarity are arranged one behind the other in the direction of movement on the transport units TE. The drive magnets 5 face the drive coils 4 of the transport path 2 and interact magnetically with the drive coils 4 to generate a drive force by which the transport unit TE can be moved along the transport path 2 . For example, several permanent magnets of different magnetic polarity can be provided as drive magnets 5 .

An air gap, in which a magnetic circuit is formed, is generally provided between the drive magnets 5 and the drive coils 4 . In addition to the driving force a holding force can also be generated, by which the transport units TE are held on the transport route 2. In the case of an LLM designed as a planar motor, instead of the holding force, a reverse levitation force can also be generated, by means of which the transport unit TE is held in levitation in order to maintain the air gap. A suitable guide device 8 (see FIG. 2) can also be provided on the transport path 2, which cooperates with suitable guide elements of the transport units TE, for example rotatably mounted wheels 9. On the one hand, this can ensure that the transport units TE do not become detached from the transport section 2 in an undesired manner, for example due to cornering forces. On the other hand, this also allows the air gap to be kept essentially constant, which improves control.

In the example shown, the direction of movement is specified by the structure or the shape of the transport section 2, so that a one-dimensional movement of the transport units TE in the specified direction of movement is possible. However, the “one-dimensional” embodiment shown is only to be understood as an example, because, as mentioned at the beginning, an LLM can of course also be designed as a so-called planar motor, in which the transport segment or segments TS form a transport level in which one or more transport units TE are at least two-dimensional can be moved in several directions. In a planar motor, therefore, the drive coils are not only arranged one after the other in a one-dimensional arrangement direction, but in several arrangement directions.

For example, a first group of drive coils 4 may be arranged in a row in a first arrangement direction and a second group of drive coils 4 may be arranged in a row in a second arrangement direction different from the first arrangement direction. For example, the first group of drive coils 4 can be arranged in a first plane and the second group of drive coils 4 can be arranged in a second plane, lying above or below the first plane. However, an arrangement in the same plane would also be possible. The two arrangement directions can, for example, be perpendicular to one another or at a different angle to one another. The invention is described below by way of example using the illustrated one-dimensional transport device 1 . Of course, the invention also includes a multi-dimensional transport device in the form of a planar motor.

The transport route 2 here has two separate transport route sections 2a, 2b, each of which is made up of a plurality of transport segments TS. Of course, more or fewer transport route sections 2i could also be provided. In the simplest case, only a single transport segment TS could be provided that Transport route 2 forms. The transport segments TS can be attached to suitable stationary holding devices 3, which in turn are arranged in a stationary manner, for example on the ground.

In the example shown, the holding devices 3 are connected by a guide device 8 (not shown in FIG. 1). The holding devices 3 and the guide device 8 together form a stationary structure on which the individual transport segments are held.

The areas in which the two transport route sections 2a, 2b overlap are so-called transfer positions at which suitable transport units TE can be transferred between the transport route sections 2a, 2b. A suitable transport unit TE is to be understood here as a transport unit TE which has drive magnets 5a, 5b on opposite sides, as is shown by way of example using the transport unit TE2. The transport unit TE2 can therefore be moved along the closed first transport path section 2a by the drive coils 4 of the first transport path section 2a interacting with the drive magnets 5a, as indicated by the movement path B1. However, the transport unit TE2 can also be transferred to the second transport path section 2b, which is open here, and moved along the second transport path section 2a by the drive coils 4 of the second transport path section 2a interacting with the drive magnets 5b.

The movement of the transport units TE is controlled via a suitable control unit 6, which can be designed, for example, as suitable hardware and/or software. The control unit 6 can, for example, in turn communicate with a higher-level system control unit (not shown), for example in order to synchronize the movement of the transport units TE with a movement of an external device, for example a handling device such as an industrial robot. A suitable controller can also be implemented in the control unit 6, with which specific movement variables of the transport units TE, e.g. position, speed, etc., can be regulated. For example, further subordinate control units can also be provided, which are controlled by the control unit 6 .

For example, a separate segment control unit 7 can be provided for each transport segment TS in order to control the drive coils 4 of the respective transport segment TS. In FIG. 1, this is represented only for two transport segments TS. Power electronics (not shown) are usually also provided on the transport segments TS, which makes the required electrical variables (current, voltage) available for the drive coils 4 in a suitable manner. Depending on the desired movement profile of a transport unit TE, the control unit 6 controls the drive coils 4 accordingly in order to apply a moving magnetic field in the direction of movement generate through which the transport units are moved in the desired manner. Each drive coil 4 can preferably be activated individually and independently of the other drive coils 4 .

In FIG. 2, on the left, a section of the transport route 2 in the area of a transport segment TS is shown in a view from the front (normal to the direction of movement) without a transport unit TE. 2 on the right shows the side view (in the direction of movement) with transport unit TE. As was described with reference to FIG. 1, the transport segments TS can be fastened to one or more suitable stationary holding devices 3, only one holding device 3 being shown in FIG. A guide device 8 is provided on the holding device 3 . The guide device 8 preferably extends continuously, ie without interruption, along the entire transport route 2. The guide device 8 can, for example, be permanently connected to the holding device 3, for example screwed. In the example shown, the guide device 8 has an upper guide rail and a lower guide rail. Rotatable rollers or wheels 9 which interact with the guide device 8 can be arranged on the transport unit TE. For example, the transport unit TE can have a base body 10 on which the drive magnets 5 are arranged on one side (or on opposite sides). The wheels 9 can be arranged in a rotatably mounted manner on the side of the base body 10 . In the example shown, the upper guide rail 8 has a groove in which the wheel or wheels 9 roll. As a result, the transport unit TE can be guided laterally, ie transversely to the direction of movement.

The transport segments TS are attached to the guide device 8 in the example shown. The attachment is preferably carried out in such a way that thermal expansion of the transport segment TS is possible in the direction of movement, so that undesirable mechanical stresses and possible deformations do not occur. In the example shown, the transport segment TS is attached to a fixed bearing 12 arranged centrally in the longitudinal direction of the transport segment TS and two loose bearings 13 each provided in the region of the ends on the guide device 8 . The bearings 12, 13 are only shown schematically in FIG. 2 and can be constructed in a suitable manner. The transport segment TS is thus firmly connected to the guide device 8 at the fixed bearing 12, so that there is no relative movement in the event of thermal expansion of the transport segment TS. The thermal expansion is absorbed by the loose bearings 13 so that the transport segment TS can expand essentially symmetrically around the center in opposite directions, starting from the fixed bearing 12 . Consecutive transport segments TS are therefore seen in the direction of movement preferably at a segment distance s spaced from each other at the Guide device 8 is arranged, as is indicated in FIG. 2 by way of example using the transport segments TSi, TSi+1, TSi-1.

In the example shown, the transport segment TS has a segment carrier 14 and a stator unit 15 arranged on the segment carrier. The segment carrier 14 can be formed, for example, from aluminum or a material containing aluminum. The stator unit 15 is preferably made of iron or a suitable ferrous material. The drive coils 4 are attached to the stator unit 15 in a suitable manner. The stator unit 15 thus advantageously forms the iron core for the drive coils 4 . A segment cover 16 made of a suitable metallic material can also be provided on the side of the transport segment TS facing the transport unit TE in order to shield at least the drive coils 4 and to form an essentially closed surface. The power electronics 17 can be arranged on the rear side of the transport segment TS opposite the drive coils 4 and is electrically connected to the drive coils 4 in a suitable manner. The power electronics 17 can be designed, for example, in the form of one or more known circuit boards or printed circuit boards, on which corresponding electronic components are provided.

Furthermore, a plurality i of position sensors 18i spaced apart from one another in the direction of movement, each having a fixed sensor position X, is provided on the transport segment TS. The position sensors 18i each generate a sensor signal when a transport unit TE, in particular the magnetic field generated by the drive magnets 5, is located in a sensor area of the respective position sensor 18. The position sensors 18i are preferably arranged at fixed sensor positions Xi on the transport segment TS, with the sensor positions Xi being able to be fixed, for example, relative to a stationary reference point PB of the transport device 1, which can be located, for example, on the guide device 8 or at any other desired location (Fig. 1 ). The sensor positions Xi of the position sensors 18i are preferably defined for a predefined reference temperature qb, for example an average ambient temperature in the range from 20°C to 30°C.

The position sensors 18i are arranged spaced apart from one another in the direction of movement at fixed and preferably constant sensor distances L=constant, as shown in FIG. However, irregular distances L ^ constant could also be provided. The sensor distances L can be measured, for example, from the middle of two adjacent position sensors 18i and can be, for example, in the range from 5 to 30 mm. For example, all position sensors 18i could be spaced at constant intervals apart from the two position sensors 18i at the two ends of the transport segment TS. The two position sensors 18i at the ends can, for example, have a smaller distance to the sensor in front of them, so that there is a sufficiently large distance to the respective segment end is provided. In addition, an additional (not shown) position sensor 18 could be provided in the area of the transition between two transport segments TSi-1, TS, TSi+1 for the special consideration of the conditions in the transition area between the transport segments TSi-1, TS, TSi+1 .

The sensor positions X defined for the number i of position sensors 18i can, for example, in turn be related to the fixed reference point PB (FIG. 1) of the transport device 1. The sensor signals detected by the position sensors 18i are transmitted to a control unit, such as the control unit 6 (FIG. 1) of the transport device 1. The control unit 6 then uses the sensor signals received from the position sensors 18i to determine the transport unit position of the transport unit TE relative to the reference point BP of the transport device 1. Based on the reference point PB, the transport unit position can, for example, be synchronized with a handling device such as an industrial robot.

The position sensors 18i can be arranged, for example, on a sensor plate 20 running parallel to the stator unit 15 in the direction of movement. In the example shown, two separate sensor plates 20 are provided, for example, which are arranged between the upper guide rail of the guide device 8 and the stator unit 15 on the segment carrier 14 . Of course, more or fewer sensor plates 20 could also be used, and the arrangement of the sensor plate(s) 20 could also be at a different point on the transport segment TS. In any case, the at least one sensor plate 20 is arranged in such a way that the position sensors 18i located thereon can detect the presence of a transport unit TE in the sensor area. Analogously to the power electronics 17, the sensor plates 20 can be designed, for example, as known circuit boards or printed circuit boards, and the position sensor or sensors 18 can be designed in the form of known AMR sensors or TMR sensors.

As mentioned at the beginning, during operation of the transport device 1, heat is usually generated on the transport segment TS, particularly in the area of the drive coils 4 and the power electronics 17. This leads to an increase in the segment temperature qe of the transport segment TS, which subsequently leads to a Thermal expansion of the transport segment TS leads in the direction of movement. The level of thermal expansion depends, for example, on the reference temperature qb, the segment temperature qe and the materials used for the components of the transport segment TS.

In the example shown, segment carrier 14 is made of aluminum with a corresponding coefficient of expansion aAL, stator unit 15 is made of iron with a corresponding coefficient of expansion aFE, and sensor plates 20 are made of a suitable plastic with a corresponding coefficient of expansion aKU educated. In this case, aAL > aFE > aKU applies, where aKU is essentially negligible. From this it can be seen that the sensor plate(s) 20 is subject to negligible thermal expansion compared to the stator unit 15 and the segment carrier 14 . When the temperature increases, the stator unit 15 and the segment carrier 14 expand differently, but the position sensors 18i and the sensor plate(s) 20 only expand very slightly. In addition, the entire sensor plate 20 can be subject to displacement due to the mechanical stresses that occur. These effects lead to certain sensor offsets ÄXi of the position sensors 18i relative to the respectively known sensor position Xi when the temperature increases, seen in the direction of movement, so that the transport unit position determined by the control unit 6 is no longer correct.

According to the present invention, a plurality i of temperature sensors 19i spaced apart in the direction of movement are therefore provided in the transport device 1, in particular on the transport segment TS, for detecting a local segment temperature qe _ί of the transport segment TS. Alternatively or additionally, a temperature model for determining the local segment temperatures qei of the transport segment TS can be stored in the control unit 6 . The control unit 6 is designed to correct the position of the transport unit on the basis of the determined local segment temperatures qei using a predefined correction model in order to take thermal expansion of the transport segment TS into account. The temperature sensors 19i can, for example, be arranged directly on the transport segment TS, preferably on the sensor plate 20, in order to record the local segment temperatures qei of the transport segment TS directly, as shown in FIG. In principle, however, suitable sensors which can remotely detect the local segment temperatures qei of the transport segment TS, such as infrared sensors, could also be used as temperature sensors 19i. Such sensors therefore do not necessarily have to be arranged directly on the transport segment TS, but could, for example, also be arranged at a distance from the transport segment TS, for example on a suitable stationary structure (not shown).

In the simplest case, for example, a characteristic can be used as a correction model, in which the corrected transport unit position is mapped as a function of the local segment temperatures qei. However, a characteristic map could also be used as a correction model, in which the corrected transport unit position is mapped as a function of the local segment temperatures qe _ί and at least one other parameter. By or the other parameters, for example, other influencing variables can be considered that affect the thermal expansion of the transport segment TS, such as a structural design of the transport segment TS, materials used or the reference temperature qb, at which the sensor positions Xi have been set. The correction model (in particular the characteristic curve or the characteristic map) can be stored, for example, as a known look-up table in the control unit 6 or in a higher-level (system) control unit with which the control unit 6 communicates. Depending on the recorded or determined local segment temperature qei, the control unit 6 can determine a corrected transport unit position from the correction model during operation of the transport device 1 .

The correction model can contain, for example, a temperature-dependent correction factor of the transport segment TS and the control unit 6 can be designed to multiply the determined transport unit position by the temperature-dependent correction factor in order to correct the transport unit position and thus determine a corrected transport unit position. The correction model in general and the correction factor in particular can, for example, be determined experimentally through tests or can also be based on physical relationships. For example, the transport unit position could be measured at different temperatures, and the measured transport unit positions could be stored in the correction model as corrected transport unit positions as a function of the local segment temperatures qei.

The sensor positions Xi of the position sensors 18i on the transport segment TS are advantageously fixed for a predetermined reference temperature qb of 20-30°C, for example, and the correction model contains the determination of a sensor offset ÄXi for each position sensor 18i (seen in the direction of movement) based on the (by the temperature sensors 19i and/or the temperature model) determined local segment temperatures qei, the reference temperature qb and a predetermined expansion factor K of the transport segment TS. The control unit 6 can then use the respectively determined sensor offset ΔXi to determine a corrected sensor position Xi _corr for the position sensors 18i and correct the transport unit position using the corrected sensor position Xi _CO rr .

To determine the sensor offsets ÄXi, a characteristic curve or a characteristic map (e.g. as a look-up table) can be stored in the control unit 6, in which the sensor offset ÄXi or the corrected sensor position Xi _corr of the position sensors 18i is mapped at least as a function of the segment temperature qe . This means that, for example, a known physical relationship between the thermal expansion can be used to determine the sensor offsets ÄXi or directly to determine the corrected sensor positions Xi _CO rr of the position sensors 18i, which includes a temperature difference between the local segment temperature qei and the reference temperature qb (e.g. the average ambient temperature) and a Expansion factor K taken into account. The expansion factor K essentially depends on the materials used as well as on the structural design and the installation situation of the transport segment TS and can be regarded as known. An empirical value can be used as the expansion factor K, for example, or the expansion factor K can also be determined experimentally, for example by measuring the thermal expansion at different temperatures. However, the expansion factor K could also be determined analytically, for example. If the transport segment TS, in particular the segment carrier 14, is fastened to the stationary structure of the transport device 1 (guide device 8 + holding device 3) with a central fixed bearing 12 with a known fastening position relative to the fixed reference point PB of the transport device 1, as in the example shown, then it can the control unit 6 determine the sensor offsets DCί of the position sensors 18i starting from the fastening position of the fixed bearing 12 . This results in a positive sensor offset DC ⁺ and a negative sensor offset DC as indicated in FIG.

Determining local segment temperatures qei is advantageous in order to be able to take into account locally different temperatures and consequently locally different thermal expansions. This can be the case, for example, when different drive coils 4 are loaded to different degrees in the direction of movement, e.g. due to a certain specified transport process, so that they generate different heat inputs.

At least one of the temperature sensors 19i is preferably arranged in the same position as one of the position sensors 18i, or at least one of the position sensors 18i is structurally combined with one of the temperature sensors 19i. In the example shown, for example, every second position sensor 18i is also designed as a temperature sensor 19i for detecting the local segment temperature qei in the area of the respective temperature sensor 19i, as symbolized by the hatched blocks. The AMR sensor mentioned, for example, can be used as a combined sensor for detecting the position and temperature. The local segment temperature qei in the area of a position sensor 18i located between two temperature sensors 19i, at which no temperature measurement takes place, can be averaged from the local segment temperatures of the neighboring temperature sensors 19i. The temperature sensor(s) 19i can, for example, be arranged analogously to the position sensors 18i on the sensor plate 20 running parallel to the stator unit 15 in the direction of movement. In the example shown, two separate sensor plates 20 are provided, for example. Of course, more or fewer sensor plates 20 could also be used.

The stator unit 15 preferably forms the iron core for the drive coils 4 and can therefore, as mentioned, be made of a ferrous material with a known Expansion coefficient OFE be formed. The control unit 6 can then take into account the expansion coefficient OFE of the stator unit 15 in the correction model for correcting the transport unit position, for example in the expansion factor K, when determining the sensor offsets ΔXi or the corrected sensor positions Xi _CO rr of the position sensors 18i. As described, the segment carrier 14 is preferably made of aluminum with a corresponding known expansion coefficient O _A L . The control unit 6 can thus possibly also take into account the expansion coefficient O _A L of the segment carrier 14 in the correction model for correcting the transport unit position, for example again in the expansion factor K of the correction model when determining the sensor offsets AXi of the position sensors 18i.

The transport segment TS can, for example, be subdivided into a plurality j of extension zones nj, viewed in the direction of movement, and an extension ΔL _nj can be calculated for each extension zone nj. The sensor offset DC for a specific position sensor 18i can then be determined from a sum or an integral of the individual extensions ΔL _nj of the extension zones nj. For example, the length of the expansion zones nj can correspond to the sensor spacing L, so that a position sensor 18i is provided for each expansion zone nj, as indicated in FIG. In this case, the number j of expansion zones nj corresponds to the number i of position sensors 18i. In principle, however, a plurality of position sensors 18i could also be arranged in an expansion zone nj. In this case, the same sensor offset DC is determined for all position sensors 18i of an expansion zone nj.

If the position sensor 18i of an expansion zone nj is also a temperature sensor 19i, the local segment temperature s _nj for the respective expansion zone nj can be detected directly, ie s _nj = qei. For an expansion zone nj without a temperature sensor 19i, the respective local segment temperature snj can be averaged, for example, from the detected local segment temperatures s _nj of the adjacent expansion zones nj+1, nj-1. If the transport segment TS is fastened according to FIG 12 arranged position sensor 18i has a lower sensor offset DC, as a further from the fixed bearing 12 arranged position sensor 18i (eg in the region of the floating bearing 13). The extension ΔL _nj of an extension zone nj can be determined by the following relationship. with an expansion factor K _nj and a (local) segment temperature s _nj of the respective expansion zone nj and with a reference temperature qb of, for example, 20-30°C. if the length of the expansion zones nj corresponds to the sensor spacing L, as shown, then the local segment temperature qe _ί recorded by the temperature sensors 19i can be used as the local segment temperature s _nj of the expansion zones nj. However, for example, the same expansion factor K _nj =K can also be used for all expansion zones nj. The above relationship then simplifies to AL _ni =K*(3 _{Sn] -} 3 _B ) . The individual expansions ΔL _m can then be summed up in both directions, starting from the fixed bearing 12, in order to obtain the sensor offset DC i of the respective position sensor 18i.

In addition, a displacement of the entire sensor plate 20 can optionally also be taken into account in the correction model in accordance with the following context. The displacement of the entire sensor plate 20 is thus the same for each position sensor 18i on the sensor plate 20 .

X _offset =K _p *{3 _{p -} 3 _B )

Where X _offset is the displacement of the entire sensor plate 20, KP is the displacement coefficient and qr is the temperature of the sensor plate 20, which can correspond, for example, to a measured or modeled local segment temperature qei (or an average local segment temperature qe _ί ) qb is in turn the reference temperature.

The sequence of a preferred position correction is briefly summarized again below. The determination of the transport unit position of a transport unit TE results from the detected sensor signals of the available position sensors 18i and the known sensor positions X relative to a reference point PB of the transport device 1. Using the detected or modeled local segment temperatures s _nj per expansion zone nj, the temperature-dependent sensor offset DC for each position sensor 18i can be determined, preferably in relation to a defined reference temperature qb (eg: B=30 ^O C).

The transport segment TS has, for example, a number j of expansion zones nj of equal size, each with a specific length which corresponds, for example, to the sensor distance L (from sensor center to sensor center). A position sensor 18i is thus assigned to each expansion zone nj. In addition, two expansion zones nj with a shorter length can be provided for the segment ends (e.g. each L minus a certain sensor edge distance LR<L). All available temperature sensors 19i (here every second sensor, which is also position sensor 18 and temperature sensor 19) are read in by the control unit 6. The local segment temperature s _nj of an expansion zone nj, in which a temperature sensor 19i is arranged, can be detected directly by the respective temperature sensor 19i, ie s _nj =qe _ί . The local segment temperature s _nj one Expansion zone nj without its own temperature sensor 19i can be averaged from the neighboring temperature sensors 19i+1, 19i-1. The measured temperature of the respectively preceding temperature sensor 19i, for example, can be used as the segment temperature s _nj for the two expansion zones nj at the end of the segment.

Each sensor offset DC ⁺ , DCG of a position sensor 18i can be determined by adding up the changes in length ÄL _nj of each expansion zone nj according to the above relationship K _n] * (3 _Sn] -3 _b ) starting from the fixed bearing 12 for the respective sensor position X in both directions will. The following applies to the first half (on the left in Fig.2):

AX ⁺ = +^AL _nj and for the respective other half (e.g. on the right in FIG. 2) the following applies: AX = -^AL _nj .

In addition, according to the above relationship, X _offset =K _P *($ _p -S _B ) a

Shift X _offset of the entire sensor plate 20 are taken into account. The displacement X _offset of the sensor plate 20 can then be added to the determined sensor offset DC as follows to give a total sensor offset ÄXi_ _total : D _total =X _offset +D . The so determined

Total sensor offsets ΔXi_ _total can then be added to the sensor position X known at the reference temperature qb according to the following relationship in order to obtain the corrected sensor position Xi _corr of interest for a position sensor 18i.

As mentioned at the outset, a cooling device (not shown) can also be provided for cooling the transport segment TS. For this purpose, for example, a suitable heat sink can be provided between the drive coils 4 and the power electronics 17 in order to dissipate the heat generated during operation of the transport device 1 (eg from the drive coils 4 and/or the power electronics 17) from the transport segment TS. For example, a suitable heat exchanger through which a cooling medium flows can be provided as a heat sink. If necessary, the cooling device can also be controlled via the control unit 6 of the transport device 1 . For example, the (local) (actual) segment temperature qe _ί detected by the temperature sensors 19i could also be used in the cooling device as an actual value for regulation to a desired predetermined (set) segment temperature qe.

Claims

patent claims

1. Transport device (1) with at least one transport segment (TS), along which at least one transport unit (TE) can be moved at least one-dimensionally, a plurality (i) of position sensors (18i) spaced apart from one another in the direction of movement being provided on the transport segment (TS), to generate a sensor signal in each case when the transport unit (TE) is located in a sensor range of the respective position sensor (18i), a control unit (6) being provided in the transport device (1) which is designed to function as a function of the sensor signals received of the position sensors (18i) to determine a transport unit position of the transport unit (TE) relative to a fixed reference point (PB) of the transport device (1), characterized in that in the transport device (1), preferably on the transport segment (TS), a plurality (i ) of temperature sensors (19i) spaced apart from one another in the direction of movement for detecting one loka len segment temperature (qei) of the transport segment (TS) are provided and/or that a temperature model for calculating the local segment temperatures (qei) is stored in the control unit (6) and that the control unit (6) is designed to use the determined local segment temperatures (qei) to correct the transport unit position by means of a predetermined correction model in order to take thermal expansion of the transport segment (TS) into account.

2. Transport device (1) according to Claim 1, characterized in that the correction model contains a temperature-dependent correction factor of the transport segment (TS) and that the control unit (6) is designed to multiply the determined transport unit position by the temperature-dependent correction factor in order to correct the transport unit position correct.

3. Transport device (1) according to claim 1, characterized in that for each of the plurality (i) of position sensors (18i) a sensor position (X i ) is defined for a predetermined reference temperature (qb), that the correction model is used to determine a sensor offset ( DC,) for each of the position sensors (18i) based on the determined local segment temperatures (qei), the reference temperature (qb) and a specified expansion factor (K) of the transport segment (TS) and that the control unit (6) is designed to use the determined sensor offsets (DC,) to determine a corrected sensor position (Xi_ _CO rr) for each position sensor (18i) and to correct the transport unit position based on the corrected sensor positions (Xi _corr ).

4. Transport device (1) according to any one of claims 1 to 3, characterized in that at least one of the temperature sensors (19i) on the same Position as one of the position sensors (18i) on the transport segment (TS) is arranged and / or that at least one of the position sensors (18i) and at least one of the temperature sensors (19i) are structurally combined.

5. Transport device (1) according to one of Claims 1 to 4, characterized in that the transport segment (TS) has a segment carrier (14) which, preferably centrally in the direction of movement, is connected to a fixed bearing (12) with a known fastening position relative to the fixed Reference point (PB) of the transport device (1) is attached to a stationary guide device (8) of the transport device (1), the plurality (i) of position sensors (18i) being arranged on the segment carrier (14) and that the control unit (6) is designed to correct the transport unit position based on the fastening position, in particular to determine the sensor offsets (DCί ⁺ , DCί ) of the position sensors (18i) based on the fastening position.

6. Transport device (1) according to one of Claims 1 to 5, characterized in that at least one stator unit (15) is provided on the transport segment (TS), preferably on the segment carrier (14), on which several drive coils (4) are connected in at least one , an arrangement direction defining a direction of movement of the transport unit (TE) are arranged one behind the other, wherein the drive coils (4) can be controlled by the control unit (6) in order to work with the transport unit (TE) to generate a drive force for at least one-dimensional movement of the transport unit (TE) in to interact electromagnetically with the direction of movement, or that a stator unit (15) is provided on the transport segment (TS), preferably on the segment carrier (14), on which several drive coils (4) are arranged in at least two different directions, each of which defines a direction of movement of the transport unit (TE). , are arranged one behind the other, the drive coils (4) from the control unit (6) can be controlled in order to interact electromagnetically with the transport unit (TE) to generate a driving force for at least two-dimensional movement of the transport unit (TE) in the two directions of movement.

7. Transport device (1) according to one of Claims 1 to 6, characterized in that the plurality (i) of position sensors (18i) and/or the plurality (i) of temperature sensors (19i) are arranged in a direction parallel to the transport segment (TS ), In particular to the stator unit (15), running sensor plate (20) are arranged, wherein the sensor plate (20) is preferably arranged on the segment carrier (14).

8. Transport device (1) according to any one of claims 5 to 7, characterized in that the stator unit (15) made of a ferrous material with a known coefficient of expansion (OFE) and/or that the segment carrier (14) is made of a material, preferably containing aluminum, with a known coefficient of expansion (OAL) and that the coefficient of expansion (OFE) of the stator unit (15) and/or the coefficient of expansion ( OAL) of the segment carrier (14) are taken into account in the correction model.

9. Transport device (1) according to one of Claims 7 to 8, characterized in that the correction model is used to determine a displacement (Xoffset) of the sensor plate (20) using a temperature (qr) of the sensor plate (20), a displacement coefficient (KP) of the sensor plate (20) and the reference temperature (qb) and that the control unit (6) is designed to use the displacement (Xoffset) of the sensor plate (20) and the determined sensor offset (DC) to calculate a total sensor offset (ÄX_ _total ) of the at least one To determine the position sensor (18) and to use the total sensor offset ( _{ÄX_total} ) to determine the corrected sensor position (X _CO rr).

10. Method for operating a transport device (1) with at least one transport segment (TS), along which at least one transport unit (TE) is moved at least one-dimensionally, with a plurality (i) of position sensors (18i ) is provided, with the position sensors (18i) each generating a sensor signal when the transport unit (TE) is moved into a sensor area of the respective position sensor (18i), with a control unit (6) based on the sensor signals received from the position sensors (18i) determining a transport unit position of the transport unit (TE) relative to a specified reference point (PB) of the transport device (1), characterized in that a local segment temperature (qei) of the transport segment (TS ) is recorded and/or that by means of a tax ng unit (6) implemented temperature model of the transport segment (TS) local segment temperatures (qei) of the transport segment (TS) are determined and that the control unit (6) corrects the transport unit position on the basis of the determined local segment temperatures (qei) by means of a predetermined correction model in order to avoid thermal expansion of the transport segment (TS) into account.

11. The method according to claim 10, characterized in that the correction model contains a temperature-dependent correction factor of the transport segment (TS) and that the control unit (6) multiplies the determined transport unit position by the temperature-dependent correction factor in order to correct the transport unit position.

12. The method according to claim 10, characterized in that for the plurality (i) of position sensors (18i), a respective sensor position (X,) is defined for a predetermined reference temperature (qb), that the correction model is used to determine a sensor offset (DC,) for each of the position sensors (18i) based on the determined local segment temperatures (qei), the reference temperature (qb) and a specified expansion factor (K) of the transport segment (TS) and that the control unit (6) based on the determined sensor offsets (DC,) contains a Corrected sensor position (Xi _corr ) determined for each position sensor (18i) and the transport unit position based on the corrected sensor positions (Xi _corr ) corrected.

13. The method according to any one of claims 10 to 12, characterized in that at least one of the temperature sensors (19i) is arranged in the same position as one of the position sensors (18i) and/or that at least one position sensor (18) and one temperature sensor (19 ) are used, which are structurally united.

14. The method according to any one of claims 10 to 13, characterized in that the transport segment (TS) has a segment carrier (14) which, preferably centrally in the direction of movement, is connected to a fixed bearing (12) with a known fastening position relative to the specified reference point (PB ) of the transport device (1) is attached to a stationary guide device (8) of the transport device (1), the plurality (i) of position sensors (18i) being arranged on the segment carrier (14) and the control unit (6) determining the transport unit position corrected by the fastening position, in particular the sensor offsets (DCί ⁺ , DCί ) of the position sensors (18i) are determined starting from the fastening position.

15. The method according to any one of claims 10 to 14, characterized in that a stator unit (15) is provided on the transport segment (TS), preferably on the segment carrier (14), on which a plurality of drive coils (4) in at least one, one direction of movement of the arrangement direction defining the transport unit (TE), the drive coils (4) being controlled by the control unit (6) in order to interact electromagnetically with the transport unit (TE) to generate a drive force, by which the transport unit (TE) moves at least one-dimensionally in the direction of movement or that a stator unit (15) is provided on the transport segment (TS), preferably on the segment carrier (14), on which a plurality of drive coils are arranged one behind the other in at least two different arrangement directions, each of which defines a direction of movement of the transport unit (TE). are, wherein the drive coils (4) from the control unit (6) ang be controlled in order to interact electromagnetically with the transport unit (TE) to generate a driving force, by which the transport unit (TE) is moved at least two-dimensionally in the at least two directions of movement.

16. The method according to any one of claims 10 to 15, characterized in that the plurality (i) of position sensors (18i) and / or the plurality (i) of temperature sensors (19i) on a direction of movement parallel to the transport segment (TS), in particular sensor plate (20) running to the stator unit (15), the stator unit (15) and/or the sensor plate (20) preferably being arranged on the segment carrier (14).