Sustainable movement planning for electromagnetic transport systems

Abstract

Embodiments of the present disclosure relate to sustainable movement planning for electromagnetic transport systems. In order to provide a method for continuously operating an electromagnetic transport system (1) for moving at least one mover (3), a first maximum (amax1, vmax1) of a first trajectory (t1) of at least one amount of movement (x, v, a) of the mover (3) is determined, and a second maximum (amax2, vmax2) of a second trajectory (t2) of the at least one amount of movement (x, v, a) of the mover (3) is determined. If the first maximum value (amax1, vmax1) is less than or equal to the second maximum value (amax2, vmax2), the first trajectory (t1) is selected as a target trajectory (t *), and if the second maximum value (amax2, vmax2) is less than the first maximum value (amax1, vmax1), the second trajectory (t2) is selected as the target trajectory (t *), and then the mover (3) is moved according to the target trajectory (t *).

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for operating an electromagnetic transport system having a stator along which at least one mover is moved, and to an electromagnetic transport system, in particular a long-stator linear motor or a planar motor. BACKGROUND

[0002] In modern transport systems, it is often necessary to transport transport units, i.e. parts, components, other goods, etc., between stations that are spatially far apart, for example processing stations, production stations or service stations. For this purpose, various transport systems are known. In recent years, however, electromagnetic transport systems, such as long-stator linear motors (LLM) and planar motors (PM), have been used for this purpose. In particular, LLMs and PMs are used to meet the high demands for flexibility and efficiency that modern transport systems usually place. In LLMs and PMs, the goods to be transported are picked up and moved by a large number of movers. Planning and coordinating the movement of a large number of movers is a crucial and often complex task that requires particular care when operating an LLM or PM.

[0003] LLMs, their applications and their operating modes are widely known from the prior art. LLMs generally consist of a stator (also referred to as "long-stator linear motor stator" or "LLM stator") and at least one mover (also referred to as "shuttle" or "transport unit") for transporting components or other goods. As described in US patent US 6,876,107 B2, LLMs generally consist of a plurality of stator segments, a plurality of drive coils (also referred to as "LLM coils") being fixedly arranged on the stator or the stator segments next to each other. The stator segments can have different geometrical shapes, such as straight lines, curves, switches, etc., and can be assembled into the desired LLM stator by stringing them together. The LLM forms a set of at least one path along which one or more transport units can be moved. The transport units are held and guided along the stator.

[0004] PMs are also known from the prior art. For example, US patent US 9,202,719 B2 discloses the basic structure and the basic operating mode of a PM. Like LLMs, PMs also include a stator, which, unlike LLMs, forms a transport plane in which one or more transport units can move in at least two dimensions. In PMs, the drive coils are usually arranged within the transport plane and in some designs also within a plurality of planes stacked on top of each other.

[0005] For achieving a controlled movement of the mover in a PM or LLM, for transporting parts, goods or components, in addition to the drive coils mounted on the stator, drive magnets (permanent magnets or electromagnets) are provided on the mover and position sensors (AMR sensors, Hall elements, etc.) are provided on the stator. By controlling the drive coils, a moving magnetic field ("magnetic drive field") can be generated, which interacts with the drive magnets of the mover and moves the mover. In a known manner, the drive coils are controlled, inter alia, by means of a control unit provided for this purpose, which outputs trigger pulses to semiconductor switches, in particular IGBT modules, in order to apply a corresponding coil voltage to the drive coils, to generate a drive current in the coils and ultimately the magnetic drive field. The drive coils that are controlled for generating the magnetic drive field and are thus energized are referred to as "active" drive coils. In order to move the mover along the stator, some of the drive coils are active drive coils, usually the case being that the drive coils that are not energized become active drive coils and the active drive coils become drive coils that are not energized. In this way, the mover can be moved in the direction of the moving magnetic drive field.

[0006] Further explanations regarding the LLM, the PM and numerous design variants of the LLM and the PM can be found in the documents WO 2013 / 143783 A1, WO 98 / 50760 A2, US 6,876,107 B2, US 2013 / 0074724 A1, WO 2004 / 103792 A1 or EP 1 270 311 B1, etc., so that further implementation details of these drive forms are not discussed here.

[0007] As mentioned in the introduction, when designing an operating strategy for a LLM or PM system, it is a key task to plan suitable trajectories for the movers in the LLM or PM system. In the important case of multiple movers, coordinating a large number of possible trajectories is particularly critical, for example, in order to avoid collisions, save energy, reduce wear, etc. Previous approaches to the movement planning of movers in a LLM or PM system, such as EP 3 868 005 B1, mainly focus on the goal of optimizing throughput. Thus, the movers are usually moved with the maximum acceleration possible, i.e. with the maximum speed, even if this means that the movers can have to wait in a "traffic jam" in front of the target handling station. By following this approach, in many cases, energy is wasted in the acceleration and braking intervals, ultimately resulting in traffic jams, which obviously have a negative impact on indicators such as energy balance, sustainability, component lifetime, etc. SUMMARY

[0008] Against this background, it is an object of the present application to provide a method for operating an electromagnetic transport system in a more sustainable manner.

[0009] For the electromagnetic transport system and method mentioned at the beginning, the object is achieved in that at a previously described planning point in time, a first maximum of a first trajectory is determined for at least one movement quantity of the mover, which first trajectory is configured to move the mover from a starting position at a starting point in time to a target position at a target point in time; a second maximum of a second trajectory is determined for the at least one movement quantity of the mover, which second trajectory is also configured to move the mover from the starting position at the starting point in time to the target position at the target point in time; if the first maximum is less than or equal to the second maximum, the first trajectory is selected as the target trajectory; if the second maximum is less than the first maximum, the second trajectory is selected as the target trajectory; and from the starting point in time, the mover is moved according to the target trajectory.

[0010] Preferably, the at least one movement quantity can correspond to a mover velocity, so that the first maximum and the second maximum can correspond to a maximum velocity; or the at least one movement quantity can correspond to a mover acceleration, so that the first maximum and the second maximum can correspond to a maximum acceleration; or the at least one movement quantity can correspond to a mover jerk, so that the first maximum and the second maximum can correspond to a maximum jerk; or the at least one movement quantity can correspond to another physical quantity associated with the mover, which other physical quantity allows to plan the movement of the mover. As is well known from the literature, a trajectory corresponds to a time curve of a physical quantity. In the above cases, the trajectory thus corresponds to a time curve of the mover velocity, mover acceleration or mover jerk, respectively, resulting in a time curve of the mover position connecting the starting position and the target position.

[0011] By operating the electromagnetic transport system according to the above strategy, the invention has a number of advantages, such as reduced energy consumption, reduced wear, reduced thermal load and simple application (no or only simplified manual optimization) which are mainly due to the fact that by selecting the target trajectory from a set of trajectories (i.e. at least two trajectories) whose respective maximum is the smallest, the trajectory is automatically selected which is most advantageous for achieving these advantages. It should be mentioned that different methods can be used to find the maximum. For example, in a simple and effective method, the maximum positive value of a trajectory can be searched for and used as the maximum. However, it is also possible to use the maximum absolute value of a trajectory as the maximum, or the maximum squared value of all values included in a trajectory as the maximum, or to apply another norm, such as the L1 norm, the L2 norm or another norm, to the trajectory before determining the maximum.

[0012] Within the scope of the present application, the trajectory can be calculated and planned in its entirety before it is evaluated by determining the maximum. Planning a trajectory essentially requires determining a time profile of the respective movement quantities, which results in a position time profile connecting the start position and the target position. For this planning step (also referred to as "path planning" in the literature), a range of planning methods known from the literature can be employed, for example the methods described in Karur, K.; Sharma, N.; Dharmatti, C.; Siegel, J. E. A Survey of Path Planning Algorithms for Mobile Robots. Vehicles 2021, 3, 448-468. https: / / doi.org / 10.3390 / vehicles3030027, or in other scientific publications, such as Gasparetto, Alessandro, et al. "Path planning and trajectory planning algorithms: A general overview." Motion and Operation Planning of Robotic Systems: Background and Practical Approaches (2015): 3-27. After the trajectory has been planned, the respective maximum can be calculated and the method of the present application can be implemented. Within the scope of the present application, of course more than two trajectories can also be considered and the most suitable trajectory selected from a larger set of trajectories, for example from a set of several thousand trajectories.

[0013] However, as will be explained later, there are also some attempts in the teaching of the present invention to allow determining the maximum values related to the trajectories without fully elaborating the trajectories themselves, which simplifies the method of the present invention, to decide which trajectory to select to continue. In fact, it is sufficient to only obtain the maximum values to be compared to each other. As will be explained later, there are some methods to allow determining such maximum values without specifically calculating the trajectories themselves, for example stopping the planning routine once a limit value for the movement quantity is reached. However, it is also possible to plan the trajectories before comparing the maximum values, i.e. before deciding which trajectory to use as the target trajectory. If the trajectories are not planned and thus not known in advance, at least the trajectory selected as the target trajectory has to be calculated at some possibly later point in time in order to be able to follow the trajectory when moving the actor according to the target trajectory. If at least one limit value is provided to limit at least one movement quantity, then during such planning process, the at least one limit value can of course be taken into account to plan the first trajectory and / or the second trajectory and / or the target trajectory to be considered when following the target trajectory. As mentioned above, planning only the target trajectory can reduce the computational costs and computational complexity.

[0014] In various important practical applications, in order to limit the movement of the actor, not only one limit value is provided, but a series of limit values, so that different limits can be imposed on different movement quantities, for example, which can be adapted to different spatial portions of the stator or the track or path on which the actor moves. In such scenarios, in which for a spatial portion from a starting position to a target position a second limit value is provided which is different from the at least one limit value to replace, adjust or modify the at least one limit value in this spatial portion, then this second limit value can also be followed and used for planning the first trajectory and / or the second trajectory and / or the target trajectory.

[0015] In another preferred embodiment, it is also possible to provide that the planning point in time is selected as a point in time before the movement of the actor starts, i.e. is selected offline before the operation; or the planning point in time is selected as a point in time during the operation of the electromagnetic transport device, so that the target trajectory is selected when the actor moves during the operation, i.e. is selected online. This variation allows the present invention to adapt to different scenarios, for example scenarios in which an online optimization is not possible, or scenarios in which the trajectory on which the actor travels is known in advance and needs to be updated.

[0016] In both cases, i.e. in the case of an offline selection of the target trajectory and in the case of an online selection of the target trajectory, a second planning time point after the planning time point can be provided during operation of the electromagnetic transport device. And at the second planning time point, a further first maximum of a further first trajectory describing a movement of the actor from a further starting position at a further starting time point to a further target position at a further target time point can be determined for the at least one movement quantity of the actor, thus allowing for a further planning during operation, i.e. online. In this embodiment, according to the concept of the present application, a further second maximum of a further second trajectory describing a second movement of the actor from the further starting position at the further starting time point to the further target position at the further target time point can be determined for the at least one movement quantity of the actor. If the further first maximum is smaller than or equal to the second maximum, the further first trajectory is selected as the further target trajectory; if the second maximum is smaller than the further first maximum, the further second trajectory is selected as the further target trajectory. After the selection of the appropriate target trajectory, the actor can be moved further according to the further target trajectory from the further starting time point of the actor. In this way, the advantages of offline and online optimization can be combined.

[0017] Preferably, in many practical applications of modern mechatronics, in order to obtain an optimal solution, an optimization method can be used to select a trajectory as the target trajectory. This optimization method determines a plurality of maxima, each maximum being associated with a respective trajectory of the at least one movement quantity of the actor, and selects the trajectory associated with the smallest maximum. Such an optimization method is preferably selected from the group comprising a Pareto optimization method, a linear programming method, a nonlinear optimization method, an artificial intelligence-based method or a neural network-based method, thus selecting an algorithm suitable for the requirements of the specific scenario.

[0018] At the target position, for example, a processing station can be provided, at which the goods transported by the actors of the electromagnetic transport device are processed, i.e. processed, modified, exchanged or assembled with other components, etc. Within the scope of the present application, in the planning of at least one trajectory considered when selecting a target trajectory, a so-called workload parameter of such a processing station can be taken into account, which describes the state of the processing station, thus enabling the existence of these processing stations to be taken into account, which achieves a series of further advantages. For example, if it is known that a traffic jam consisting of other actors also trying to enter the processing station already exists in front of the processing station, the actors can be made to drive more slowly towards the processing station.

[0019] Furthermore, in a series of related practical applications, there can be a plurality of movers in the electromagnetic transport system. In such a case where there is more than one mover and thus at least one further mover is moving towards the target position, at least one value of a further movement quantity related to the at least one further mover can be considered for planning the trajectories considered when selecting the target trajectory. Specifically, by considering the position of the movers present in the transport system, the first and second trajectories can be planned such that during operation of the electromagnetic transport device a pre-described buffer distance, i.e. a safety distance, between the mover and the at least one further mover is ensured to ensure that no collision between consecutive movers occurs. Preferably, the buffer distance can at least correspond to the longitudinal extension of the mover moving in the electromagnetic transport system, i.e. for example its length in the direction of movement, or to a multiple of the longitudinal extension of the mover moving in the electromagnetic transport system, for example twice, three times or four times the longitudinal extension of the mover moving in the electromagnetic transport system.

[0020] Furthermore, traffic parameters representing the traffic situation in the electromagnetic transport device can also be considered for planning the trajectories considered when selecting the target trajectory and thus for moving the mover. Such traffic parameters can represent several important indicators influencing the movement of the mover in the electromagnetic transport device, for example the average speed of the mover moving in the electromagnetic transport device, the average distance between adjacent movers moving in the electromagnetic transport device, or the minimum speed reached by the mover moving in the electromagnetic transport device within a pre-described traffic observation time interval. BRIEF DESCRIPTION OF DRAWINGS

[0021] The application will be described below in more detail with reference to Figure 1 The application will be described below in more detail with reference to

[0022] Figure 1 for an embodiment of the stator in the form of a long stator linear motor;

[0023] Figure 2a , Figure 2b different views for a possible embodiment of the planar motor;

[0024] Figure 3 for a speed profile of the mover;

[0025] Figure 4a - figure c is a position profile, a speed profile and an acceleration profile of the mover obtained by the application;

[0026] Figure 5 for a stator with a covered segment;

[0027] Figure 6for a stator with traffic jams and flexible zones;

[0028] Figure 7a - figure b is a stator segment with a different embodiment of buffer zones. DETAILED DESCRIPTION

[0029] With reference to what was said in the introduction, the present application can be used in particular for operating electromagnetic transport devices 1 in the form of long-stator linear motors or planar motors. Before explaining the present application in detail, these motor types will first be briefly discussed.

[0030] Figure 1 An arbitrary structural example of a long-stator linear motor (LLM) 1 is shown, which comprises a stator 2 and a plurality of movers 3i The movers 3i are movable along the stator 2. The stator 2 is essentially defined by the stationary long stator 2 of the LLM 1. In the example embodiment shown, a plurality of stator segments FSj A path is defined for the movers 3i. The stator segments FSj are arranged on a suitable structure. Each stator portion FAk comprises at least one stator segment FSj, and usually several stator segments FSj. The individual stator portions FAk can be partially overlapping along the stator 2 in the movement direction x, possibly on different sides of the mover 3i, and in particular at the switching positions W of the stator 2, the mover 3i can transition from a first stator portion FAk on one side to another stator portion FAk on the other side (such as from stator portion FA1 to stator portion FA2).

[0031] Each stator segment FSj comprises n drive coils ASj,n These drive coils are arranged next to each other in the movement direction x, wherein for each stator segment FSj the value of n is not necessarily the same. In Figure 1 In the figure, for the sake of clarity, only some of the drive coils ASj,n of the stator segments FSj are shown. Each mover 3i comprises m excitation magnets EMi,m (Permanent magnets or electromagnets), preferably on both sides of the movers 3i. The drive coils ASj,n generate a moving magnetic field and interact in a known manner with the excitation magnets EMi,m of the movers 3i in the magnetic field of the drive coils ASj,n according to the principle of electro-dynamics in the LLM 1 operation. If the drive coils ASj,n in the area of a mover 3i are supplied with a coil current by applying a coil voltage to the coils, a magnetic flux is generated which, in interaction with the excitation magnets EMi,m, generates a force on the mover 3i. Depending on the coil current, this force can comprise, according to the prior art, a propulsion or drive force component for moving the mover 3i in the desired direction and / or a lateral force forming force component for holding the mover 3i on the stator 2. The propulsion force component is mainly used for the movement of the mover 3i in the direction of movement, while the lateral force component can be used to guide the mover 3i and, if necessary, also to turn the mover 3i. In this way, each mover 3i can be moved individually and independently along the stator 2 by providing the drive coils ASj,n in the area of each mover 3i with a corresponding coil current depending on the movement to be performed.

[0032] In the case shown, it can be desirable to move the movers from a first position A to a second position B. The positions A and B can be, for example, positions of a handling station at which the movers 3i can load goods to be transported or at which the goods transported by the movers 3i can be handled or exchanged, etc., such as bottles filled with liquid, etc. As will be discussed in detail hereinafter, when developing an operation strategy for an electromagnetic transport system like the LLM 1 presently discussed, it is essential to plan a trajectory for moving the movers 3i from A to B or vice versa. In order to describe the movement of the movers 3i in the LLM 1 as well as in the PM 1, hereinafter movement quantities such as position x, velocity v and acceleration a will be used. These movement quantities x, v, a, or parts of these movement quantities x, v, a, can be represented by vectors, as Figure 1 are shown, but other representations as well as other movement quantities x, v, a are conceivable.

[0033] To control the movement of the individual movers 3i, a mover control unit 13 (hardware and / or software, e.g. FPGA, microcontroller, etc.) is provided in which a setpoint value S for the movement of the mover 3i is generated or determined. The setpoint value S can comprise a desired velocity, a desired acceleration or a desired jerk to be achieved during the movement of the mover 3i. The setpoint variable S can thus specify setpoint values for the above-mentioned movement quantities x, v, a, which are decoded in a trajectory for moving the mover 3i from a position A to a position B. Of course, a plurality of mover control units 13 can also be provided, each of which is assigned to a portion of the stator 2, e.g. a stator portion FAk, and controls the movement of the mover 3i in this portion only by appropriately powering the drive coils ASj,n. Furthermore, a segment control unit 14 (hardware and / or software) can also be provided, which is assigned to one stator segment FSj (or several stator segments FSj, or also a portion of a stator segment FSj) and converts the setpoint specifications for the mover 3i from the associated mover control unit 13 into coil currents for the associated drive coils ASj,n.

[0034] When moving a plurality of movers 3i, it must be ensured in the stator control unit 15 or the mover control unit 13 that no impermissible states occur on the stator 2. This mainly includes avoiding collisions between two or more movers 3i, in particular when more than one mover 3i is to be moved from a position A or a processing station A to a position B or a processing station B. The present application can be used in particular for this purpose, as will be discussed in detail later. Since the basic working principle of LLMs is well known, no further details will be discussed here.

[0035] Figure 2a and Figure 2b A simplified example embodiment of an electromagnetic transport device 1 in the form of a planar motor (PM) 1 is further shown. In particular, Figure 2a A partial sectional plan view of the PM 1 is shown, Figure 2b A partial sectional side view of the PM 1 is shown. In the case of the PM 1, the stator 2 is in the form of at least one movement plane 30. The at least one mover 3i is two-dimensionally movable along the movement plane 30 in at least two main movement directions H1, H2. In the case shown, two example movers 3i, 3i+1 are depicted, which are both moved towards a target position B. Likewise, in the case of the PM 1, the start position A and the target position B can be positions of processing stations at which goods transported by the planar movers 3i are processed, loaded, modified, handled, etc.

[0036] The movement plane 30 can be oriented in space in any way. For simplicity, Figure 2aOnly one transport segment is shown. Of course, multiple (possibly different) transport segments can be arranged adjacent to each other to form the stator 2 and a larger moving plane 30. Thus, the transport device 1 can be modular in design, allowing for moving planes 30 of varying shapes and sizes to be connected in various ways to the processing stations and, thus, the starting position A and the target position B. Of course, this modular design is optional; it is also possible to provide only a single assembled transport segment. As previously mentioned, several movers 3i can also move simultaneously and independently of each other within the moving plane 30 of the transport segment.

[0037] In the specific case of the PM 1 currently shown, a first coil group SG1 having several drive coils AS1 defining a first main movement direction H1 and a second coil group SG2 having several drive coils AS2 defining a second main movement direction H2 are arranged on the transport section 20. Usually, the drive coils are denoted by ASi, where "i" is an index in order to distinguish the drive coils when necessary. The drive coils AS1 of the first coil group SG1 are arranged adjacent to each other in a specific direction (in this case the X direction of the Cartesian coordinate system) so as to form the first main movement direction H1 for the movement of the mover 3i, which direction in this case extends along the X axis. The drive coils AS2 of the second coil group SG2 are arranged adjacent to each other in a specific direction (in this case the Y direction of the Cartesian coordinate system) so as to form the second main movement direction H2 for the mover 3i, which direction in this case extends along the Y axis. As Figure 2a As shown, the drive coils AS1 , AS2 of the first and second coil groups SG1 , SG2 are preferably arranged relative to each other such that the two main movement directions H1 , H2 are orthogonal to each other.

[0038] With through Figure 1 As in the case of the LLM discussed above, several drive magnets 4 are arranged on at least one mover 3i, which electromagnetically interact with the drive coils AS1, AS2 of at least one of the two coil groups SG1, SG2 in the region of the mover 3i in order to move the mover 3i. To this end, the mover 3i generally has a body 9, on the underside of which (facing the movement plane 30) the drive magnets 4 are arranged, as shown in FIG. Figure 2b As shown. Figure 2a In FIG, the main body 9 is mostly cut away to be able to show the arrangement of the drive magnet 4. Figure 2b As shown, the drive magnets 4 are arranged in several magnet groups MGa, MGb. The drive magnets 4 are usually arranged with alternating polarity, such as Figure 2bAs shown. The drive magnets 4 can also have different orientations in different magnet groups MGa, MGb. For the PM 1 shown, for example, the mover 3i can basically move without restriction in the two main movement directions H1, H2 in the movement plane 30 of the transport section 20. For example, in this case, the mover 3i can move only along the X axis or only along the Y axis. The mover 3i can also move simultaneously in the two main movement directions H1, H2, for example, along a two-dimensional movement path BPn located in the movement plane 30 and having X and Y coordinates, as shown. Figure 2a As the basic working principle of PM 1 is well known, further details will not be given here.

[0039] As mentioned at the outset, planning the appropriate movements and trajectories of the movers 3i to be moved within LLM 1 or PM 1 (for example, moving mover 3i from position A to position B) is a crucial task when designing an operating strategy for an LLM 1 or PM 1. Previous approaches to planning mover movements within LLM or PM systems have primarily focused on driving at maximum acceleration and / or deceleration and / or maximum velocity, solely with the goal of optimizing throughput. In many cases, such strategies are energy inefficient and often even increase the risk of collisions, making them unsustainable.

[0040] The impact of this unsustainable mobility planning is as follows Figure 3 As shown in Figure 1, the velocity signal-time curve of mover 3i moving in LLM 1 is presented. Mover 3i moves from starting position A to target position B while interacting with a series of other movers 3i+1, 3i+2, 3i-1, and so on. Encounters with other movers 3i+1 necessitate a series of acceleration and braking processes, particularly to avoid collisions and maintain a minimum buffer distance. This is obviously detrimental to the various components involved in the transport system (e.g., coils, brakes, stator 2, etc.). Frequent acceleration and braking consumes a large amount of energy, which is converted into heat and cannot be recovered.

[0041] To solve these problems, for an LLM 1, a PM 1 or a general electromagnetic transport system 1 having a stator 2 along which at least one mover 3 is moved, e.g. a magnetic levitation system, according to the present application, at a pre-described planning time point tP, a first maximum amax1, vmax1 of a first trajectory t1 is determined for at least one movement quantity x, v, a of the mover 3, the first trajectory t1 being configured to move the mover 3 from a start position A at a start time point tA to a target position B at a target time point tB; further a second maximum amax2, vmax2 of a second trajectory t2 is determined for said at least one movement quantity x, v, a of the mover 3, the second trajectory t2 also being configured to move the mover 3 from the start position A at the start time point tA to the target position B at the target time point tB; then a selection is made between these trajectories, i.e. if the first maximum amax1, vmax1 is smaller than or equal to the second maximum amax2, vmax2, the first trajectory t1 is selected as the target trajectory t*; if the second maximum amax2, vmax2 is smaller than the first maximum amax1, vmax1, the second trajectory t2 is selected as the target trajectory t*. After the selection process, the mover 3i moves according to the target trajectory t* from the start time point tA onwards towards the target position B. The trajectories t1, t2, t* describe a time curve of setpoint values of the above-mentioned movement quantities x, v, a and can be converted into appropriate setpoint variables S, which are implemented by the above-mentioned control unit. The time points, i.e. the planning time point tP, the start time point tA and the target time point tB, as well as the start position A and the target position B, can be selected by an operator operating the electromagnetic transport system 1, or be prescribed by an operating strategy stored in the control unit 13 of the electromagnetic transport system 1, or be provided in another way. Depending on the specific circumstances of the application of the present application, the skilled person will select an appropriate method to provide these parameters.

[0042] In this way, the present application has a number of advantages, such as reduced energy consumption, reduced wear, reduced balancer load, reduced (static) thermal load and simple application (no or simplified manual optimization) is required, since from a set of trajectories, i.e. at least two trajectories, the one is specifically selected which is most advantageous to achieve these advantages. Within the scope of the present application, it is possible to completely calculate and plan the trajectories before evaluating them by determining the maximum values. However, there are also methods which allow determining the maximum values associated with the trajectories without elaborating on the trajectories, so as to decide which trajectory to continue with, e.g. by stopping planning the trajectory as soon as a limit value is reached. Within the scope of the present application, it is of course also possible to consider more than two trajectories and select the most suitable one from such a larger set of trajectories. The at least one movement quantity can correspond to a mover velocity v, a mover acceleration a, or to another physical quantity associated with the mover which can be used to plan a movement.

[0043] Fig. 4 shows two example trajectories t1, t2 that can be considered in the above process. For example, the first trajectory t1 can be given a priori as a specification provided by an operator. It is obvious by simple visual inspection that the second trajectory t2 is more sustainable, as the number of acceleration and deceleration processes that need to be performed is less. In this regard, it is found that, in particular, the maximum speed vmax, the maximum acceleration amax, or the maximum jerk that is achieved during the movement can be considered as a measure of sustainability. Of course, combinations of these measures are conceivable as well. If it is possible to reduce the maximum speed during the movement of the mover 3i from the start position A to the target position B while keeping the duration of the movement constant, in many practically relevant cases less energy can be consumed, wear can be reduced, and in general a more sustainable movement can be achieved. For this purpose, the core of the present invention is to reduce the above-mentioned maximum values, in particular the maximum speed and / or the maximum acceleration and / or the maximum jerk, while keeping the duration of the movement constant, so that a more smooth movement is achieved, which is beneficial for the mover 3i, the LLM 1 or the PM 1, and the goods to be transported. Furthermore, it can be seen from Figure 4c Fig. 4 that the number of changes in acceleration that are required for the “sustainable” trajectory t2 is also less, which can be considered as another measure of sustainability. If a second trajectory cannot be found for which the maximum speed vmax is smaller and still allows for the transportation of the mover within the same time, the first trajectory can still be used for guiding the mover 3i.

[0044] In the scenario shown in Fig. 4, the planning time point tP is chosen as a time point before the operation of the electromagnetic transport device 1 starts, so that the target trajectory t* is chosen before the mover 3 starts moving. It can be seen that the speed v(tP) assumed at the planning time point tP is zero. However, the planning time point tP can also be chosen as a time point during the operation of the electromagnetic transport device 1, so that the target trajectory t* is chosen while the mover 3 is already moving. This means that both online selection and offline selection are possible within the scope of the present invention.

[0045] Furthermore, a combination of offline and online optimization can also be performed, or the target trajectory t* is re-planned or re-selected at least once online planning has been performed. To this end, as shown in Fig. 4, a second planning time point tP2may be provided after the planning time point tPduring operation of the electromagnetic transport device 1. At the second planning time point tP2, a further first maximum amax1, vmax1may be determined for the at least one movement quantity x, v, a of the mover 3 of a further first trajectory t1describing a movement of the mover 3 from a further starting position A at a further starting time point tAto a further target position B at a further target time point tB; a further second maximum amax2, vmax2may be determined for the at least one movement quantity x, v, a of the mover 3 of a second trajectory t2describing a second movement of the mover 3 from the further starting position A at the further starting time point tAto the further target position B at the further target time point tB. The selection steps according to the present application can then be repeated, i.e. if the further first maximum amax1, vmax1is smaller than or equal to the second maximum amax2, vmax2, the further first trajectory t1is selected as the further target trajectory t*; if the second maximum amax2, vmax2is smaller than the further first maximum amax1, vmax1, the second trajectory t2is selected as the further target trajectory t*. Finally, the mover 3 moves according to the further target trajectory t* starting from the further starting time point tA. It is to be mentioned that the second planning time point tP2may also be chosen as a time point between the first starting time point tAand the first target time point tB, such that the target trajectory t* can even be re-selected before the previously pre-described target position tBis reached. This approach is particularly useful in case new obstacles occur, or another mover 3i+1moves unexpectedly and an appropriate reaction is required.

[0046] Generally, in motion and movement planning, limit values need to be respected. Depending on the object to be moved (in this case the mover 3i), and depending on the structure of the stator 2, generally a maximum velocity value vlimhas to be respected to avoid damage or other adverse effects. In most practically relevant cases, also limits for acceleration and jerk need to be considered.

[0047] In the control or software concept implemented in the control unit 13 for controlling the LLM 1 or PM 1 to move the movers 3i, a common option is to provide a maximum speed limit vlim and / or a maximum acceleration limit alim for a certain mover type. Depending on the specific circumstances of a certain mover 3i, such as its structural parameters, weight, load, etc., it can be necessary to limit the allowed speed and / or the allowed acceleration and / or the maximum allowed jerk. In this respect, it is also possible to define local speed and acceleration limits, which can be lower or higher than the global limits for certain spatial regions. Figure 5 Such a region is shown, in which a second speed limit vlim2 is provided, which is smaller than the first global speed limit vlim. Figure 5 The idea behind this is to limit the allowed speed in the processing station region at position B to a smaller value in order to operate particularly carefully within this processing station region. These smaller values are referred to as "override parameters" hereinafter.

[0048] In particular when commissioning the LLM 1 or PM 1, or when problems occur during operation, it can not be desirable to apply the maximum speed, but rather to operate carefully first and test everything at a lower speed and / or lower acceleration before everything is running properly.

[0049] These limits can of course also be incorporated into the application. In particular, at least one limit value vlim, alim can be provided for this purpose to limit at least one movement quantity x, v, a. When planning the second trajectory t2 and / or when planning the first trajectory t1, i.e. when the trajectory planning considered in the selection process according to the application, of course also the at least one limit value vlim, alim is taken into account. This can become even more important for an adaptive LLM or PM 1, if different products (of different masses) are moved and it is only discovered during operation that smaller limit values need to be used.

[0050] In the case of the override function described above, for the spatial portion from the start position A to the target position B, a second limit value vlim2, alim2 can be provided instead of the at least one limit value xlim, vlim, alim for this spatial portion. Of course, this second limit value xlim2, vlim2, alim2 can also be used for planning the second trajectory t2 and / or the first trajectory t1. In an electromagnetic transport system like the LLM 1 or PM 1, it is conceivable that such override parameters can not only be applied globally, but also only locally in certain portions of the assembly, for example Figure 5The reasonable movement limits depend not only on the distance to the next processing station, but also on the geometry and physical limitations of the components. In particular, the speed of a fully loaded mover 3i driving on a curve can not be as fast as when driving on a straight or when shuttling empty. In principle, it might be possible to drive as fast, but the energy required and the wear caused would be disproportionate, so it is more appropriate to accelerate on a straight to make up for time. Therefore, it is particularly advantageous for the LLM to reduce the above maximum in the curve area.

[0051] While a variety of trajectory planning methods are known from the literature, in the context described herein, it has proven particularly useful to plan at least the second trajectory t2 using an optimization method. The optimization method aims to minimize an objective value J while keeping the target time tB to reach the target position B unchanged. In the optimization process, the second maximum amax2, vmax2, preferably the maximum speed, the maximum acceleration or the maximum jerk, or any combination thereof, can be used to formulate the objective J; or the electromagnetic energy E consumed when moving the mover 3 from the start position A to the target position B em can be used as the objective value J; or the number of changes in the acceleration sign is used as the objective value J; or a combination of the above objective values J is used as the objective value J. Among the numerous available optimization methods, linear programming methods and non-linear optimization methods in particular can produce particularly good results. However, as will be explained further below, other methods, such as the Pareto optimization method, have also proven to produce reliable results.

[0052] It should be mentioned that the above optimization methods can in particular be combined with a priori simulation in order to plan the trajectories before the operation of the LLM or PM actually begins. In combination with the Pareto optimization, it is possible to efficiently and automatically optimize the movement parameters of the segments between the processing stations. For the Pareto optimization, it can be necessary to perform several simulations of the entire system consisting of the LLM or PM in order to obtain data such as the simulated throughput times and / or the number of movers in the processing stations. During these simulations, the above-mentioned limit parameters such as vmax max , amax max , and other parameters such as the number of tickets at the processing stations, the number of movers in the system, etc. can be varied in order to find a setting of the various parameters that produces the optimal value. The objective function to be optimized can include the above-mentioned throughput, energy efficiency, duration of complete acceleration / deceleration of the shuttles, number of movers, etc., or a combination thereof. Then the combination of parameters that brings the best result for the objective function is selected.

[0053] The optimization-based approaches described so far generally rely on some assumptions made when setting up the optimization. These assumptions can relate to so-called workload parameters of the processing stations, i.e. throughput times in the processing stations, number of movers 3i waiting in front of the processing stations, energy consumption of the processing stations, etc., but also to the distance of travel covered by the movers 3i, the number of movers 3i present in the LLM 1 or PM 1, etc. However, finding the optimal parameters is often not trivial and can therefore require an extension of the optimization by additional heuristic approaches, further complex simulations or further theoretical considerations. However, if the boundary conditions change, for example because a certain processing station stops operating, or because a different product is produced, thereby changing the respective load on the movers 3i, the a priori optimization can not lead to satisfactory results. In this case, the concept of the present application can be extended by an automatic adjustment during runtime.

[0054] To this end, the target trajectory t can be adjusted by modifying at least one setpoint value of at least one of the movement quantities x, v, a while moving the mover 3i along the target trajectory t. In the prior art, it is common to calculate the shortest path between the current position and the target position to move the mover 3i from a starting position A, where a first processing station can be located, to a target position B, where a second processing station can be located. However, if such a path is suddenly blocked, for example by an obstacle closing, a traffic jam, other moving objects slowing down, other movers 3i breaking down, or an accident between other movers 3i, it can be better, or even necessary, to choose an alternative path, and thus the adaptive re-planning function described above needs to be applied. In principle, the decision to perform the adaptive re-planning process can also be made at any intersection during operation, either automatically or triggered by an operator. Ultimately, it is crucial that the mover 3i reaches its intended destination.

[0055] If the mover 3i is on its way from one processing station to the next, the throughput of the second processing station can generally be calculated based on throughput data (nominal or actual throughput, for example the throughput of the last 5 minutes, or an average value of past throughputs) about the second processing station in the past, or the distance between the two processing stations. For example, the processing stations can count the number of parts per minute (PPM) and inform the shuttles when they can expect to be immediately processed at the processing station without having to wait any longer (“receive a ticket”). If there are other movers 3i on their way to the processing station, or if other movers 3i are already waiting in front of the second processing station, i.e. in front of the target position B, a traffic jam TJ can result, as Figure 6In order to avoid unnecessary acceleration (as this would only lead to an earlier arrival at the congestion point TJ), such information can be incorporated into the planning process of the second trajectory in order to further reduce the movement parameters, as a later arrival at the congestion point TJ does not increase the total time to arrival at the processing station B compared to the first trajectory which rushes towards the end of the congestion point TJ at high speed. With this information, not only can energy be saved further, but wear can also be reduced additionally, while still ensuring that the mover 3i arrives at the desired time. In particular, in order to incorporate information such as about traffic congestion into the operating strategy according to the application, traffic parameters which represent the traffic situation in the electromagnetic transport device 1 can be considered for planning the trajectories ti, t2 which are considered for the selection of the target trajectory t* and thus for the movement of the mover 3i. Such traffic parameters can represent the average speed of the movers 3i moving in the electromagnetic transport device, the number of movers waiting in front of the processing station, the average distance between adjacent movers in the electromagnetic transport device 1, or the minimum speed reached by the movers 3i moving in the electromagnetic transport device 1 within a previously described traffic observation time interval.

[0056] Simple path-time calculations can be used to determine these movement parameters, but big data methods can also be used. In other words, the system learns which movement parameters help to minimize the time of the processing station shuttle and the time the shuttle waits in front of the processing station. Within the scope of the present application, big data methods are based in particular on long-term data collection and the use of large data sets resulting from such long-term collection. In particular, long-term data collection and subsequent analysis can lead to better estimates and predictions, for example about throughput, which can depend on other parts of the transport device (i.e. LLM or PM), other transport devices (which can be periodic), or on external parameters, etc. All these potential sources of influence on throughput can be integrated, their data collected and evaluated to arrive at an estimate.

[0057] The movement parameters x, v, a are preferably selected and adjusted appropriately before the mover 3i starts a new movement, as this makes it easier to handle the possibly large number of movers 3i. In general, as Figures 7a-7b As shown, there are multiple movers 3i in the LLM or PM, so that there can be interactions between different movers 3i. These interactions should be taken into account when considering, evaluating or planning a new trajectory, such as the second trajectory t2 described above. Therefore, within the scope of the present application, at least one value of at least one other movement parameter x2, v2, a2 of at least one further mover 3i+1 can be considered for planning the first trajectory ti or other considered trajectories.

[0058] If more than one actor 3i is on the way to the target position B (e.g. a processing station can be located at the target position B) and these actors 3i queue in front of this processing station, the first trajectory t1 and the second trajectory t2 can be planned such that during operation of the first trajectory t1 and the second trajectory t2 it can be ensured that the pre-described buffer distance dmin between an actor 3i and at least one further actor is maintained. Maintaining the minimum buffer distance is particularly important to avoid collisions between the actors 3i.

[0059] In a preferred embodiment, in this case the buffer distance dmin can be modified depending on the values of the at least one further movement quantity x2, v2, a2 of the at least one further actor 3i+1. This means that the buffer distance dmin can be increased or decreased, for example, depending on the speed of the two actors 3i, 3i+1 separated by this buffer distance dmin. In particular, if the second actor 3i+1 moves faster than the first actor 3i, i.e. the distance between the two actors 3i, 3i+1 is decreasing, it can be reasonable to increase the buffer distance dmin. In addition to avoiding collisions, the purpose of this particularly advantageous embodiment is also to reduce the number of start movements or oscillations in the stop-and-go traffic, in particular to avoid the so-called "accordion effect" (i.e. a "squeezing and zooming effect" between the vehicles) which is well known in conventional street traffic planning. In particular when one actor 3i follows another actor 3i, smaller accelerations can also be employed, as it is very likely that a sharp deceleration will be required, in particular when one actor 3i can be (too) close to another actor 3i in front of the first actor.

[0060] Furthermore, it also seems inappropriate to always immediately approach (the vehicle in front). In many cases, it can be better to define an elastic interval (a, b) to describe the distance between two adjacent actors. Only when an actor 3i+1 exceeds this elastic interval (a, b), i.e. as Figure 6 shown in Fig. 6, the movement to approach (the vehicle in front) is started when the distance is greater than b. However, once a sufficient distance between these actors 3i is reached, it can be provided that this distance is no longer increased further. In this respect, the so-called following actor, i.e. the actor 3i+1 following behind the other actors 3i, can be moved by employing a different acceleration profile to ensure that there is sufficient distance. For example, the acceleration profile of the following actor can be less steep and include a smaller maximum acceleration value. Furthermore, in particular when the following actor approaches (the vehicle in front), the movement can be reduced in its severity by employing a smaller maximum value and driving more slowly, even if the following actor is closer to the further actor.

[0061] By connecting several buffers in series, i.e. creating a cascade of buffers, a similar effect as with the elastic section can be achieved. The last buffer in such a series, i.e. the buffer immediately in front of the processing station, is preferably set according to the requirements of the target processing station and can allow the shuttles to pass individually. The upstream barriers near the processing station are opened at a low level of the last barrier's buffer, but then allow several shuttles to pass simultaneously, so that the first buffer is filled again. Of course, the same principle can also be applied iteratively to several barriers connected in series, like at an airport.

Claims

1. A method for operating an electromagnetic transport device (1) having a stator (2), at least one mover (3) moving along the stator (2), characterized in that, At a previously described planning time point (tP), a first maximum value (amaxl, vmaxl) of a first trajectory (tl) is determined for at least one movement quantity (x, v, a) of the mover (3), the first trajectory (tl) being configured to move the mover (3) from a start position (A) at a start time point (tA) to a target position (B) at a target time point (tB), wherein a second maximum value (amax2, vmax2) of a second trajectory (t2) is determined for the at least one movement quantity (x, v, a) of the mover (3), the second trajectory (t2) being configured to move the mover (3) from the start position (A) at the start time point (tA) to the target position (B) at the target time point (tB), wherein the first trajectory (tl) is selected as a target trajectory (t*) if the first maximum value (amaxl, vmaxl) is equal to or smaller than the second maximum value (amax2, vmax2), the second trajectory (t2) is selected as the target trajectory (t*) if the second maximum value (amax2, vmax2) is smaller than the first maximum value (amaxl, vmaxl), and the mover (3) is moved according to the target trajectory (t*) starting from the start time point (tA).

2. The method of claim 1, wherein, The planning time point (tP) is selected as a time point before the mover (3) starts moving.

3. The method of claim 1, wherein, The planning time point (tP) is selected as a time point at which the mover (3) is moving. The planning time point (tP) is selected as a time point at which the mover (3) is moving.

4. The method according to claim 1, 2 or 3, characterized in that, A second planning time point (tP2) is provided at which the mover (3) is moving after the planning time point (tP), wherein at the second planning time point (tP2) a further first maximum value (amax1, vmax1) of a further first trajectory (t1) describing a movement of the mover (3) from a further start position (A) at a further start time point (tA) to a further target position (B) at a further target time point (tB) is determined for at least one movement quantity (x, v, a) of the mover (3), a further second maximum value (amax2, vmax2) of a further second trajectory (t2) describing a second movement of the mover (3) from the further start position (A) at the further start time point (tA) to the further target position (B) at the further target time point (tB) is determined for the at least one movement quantity (x, v, a) of the mover (3), the further first trajectory (t1) is selected as a further target trajectory (t*) if the further first maximum value (amax1, vmax1) is equal to or smaller than the second maximum value (amax2, vmax2), or the further second trajectory (t2) is selected as a further target trajectory (t*) if the second maximum value (amax2, vmax2) is smaller than the first maximum value (amax1, vmax1), and the mover (3) is moved according to the further target trajectory (t*) starting from the further start time point (tA).

5. The method according to any of the preceding claims, characterized in that, The at least one movement quantity (x, v, a) corresponds to a mover velocity (v) and the first maximum value (amax1, vmax1) and the second maximum value (amax2, vmax2) correspond to a maximum velocity (vmax), or the at least one movement quantity (x, v, a) corresponds to a mover acceleration (a) and the first maximum value (amax1, vmax1) and the second maximum value (amax2, vmax2) correspond to a maximum acceleration (amax), or the at least one movement quantity (x, v, a) corresponds to a mover jerk (j) and the first maximum value (amax1, vmax1) and the second maximum value (amax2, vmax2) correspond to a maximum jerk (jmax).

6. The method according to any of the preceding claims, characterized in that, At least one limit value (vlim, alim) is provided to limit the at least one movement quantity (x, v, a), and the at least one limit value (vlim, alim) is considered in the planning process for planning the first trajectory (t1) and the second trajectory (t2) which are considered when selecting the target trajectory (t*).

7. The method according to any of the preceding claims, characterized in that, A second limit value (vlim2, alim2) different from the at least one limit value (xlim, vlim, alim) is provided for a spatial portion between the start position (A) and the target position (B) to replace the at least one limit value (xlim, vlim, alim) in the spatial portion, and the second limit value (xlim2, vlim2, alim2) is used for planning the second trajectory (t2).

8. The method according to any of the preceding claims, characterized in that, An optimization method is used to select a trajectory as the target trajectory (t*), the optimization method determining a plurality of maxima (amax1, vmax1), each maxima being associated with a respective trajectory (t1, t2,...) of the at least one movement quantity (x, v, a) for the mover (3), the optimization method preferably being selected from the group comprising a Pareto optimization method, a linear programming method, a nonlinear optimization method, an artificial intelligence-based method, or a neural network-based method.

9. The method according to any of the preceding claims, characterized in that, A processing station is provided at the target position (B), and a work load parameter of the processing station is taken into account for planning at least one of the trajectories considered when selecting the target trajectory (t*).

10. The method according to any of the preceding claims, characterized in that, At least one further mover (3i+1) is moved towards the target position (B), and at least one value of a further movement quantity (x2, v2, a2) of the at least one further mover (3i+1) is taken into account for planning the trajectories (t1, t2) considered when selecting the target trajectory (t*).

11. The method of claim 10, wherein, The first trajectory (t1) and the second trajectory (t2) are planned such that a pre-described buffer distance (dmin) between the mover (3) and the at least one further mover is guaranteed during operation of the electromagnetic transport device (1).

12. The method according to claim 10 or 11, characterized in that, A traffic parameter representing a traffic situation in the electromagnetic transport device (1) is taken into account for planning the trajectories (t1, t2) considered for the target trajectory (t*).

13. The method of claim 12, wherein, The traffic parameter represents an average speed of the mover (3i, 3i+1, 3i-1) moving in the electromagnetic transport device (1), or the traffic parameter represents an average distance between adjacent movers (3i, 3i+1, 3i-1) moving in the electromagnetic transport device (1), or the traffic parameter represents a minimum speed reached by a mover (3) moving in the electromagnetic transport device (1) within a pre-described traffic observation time interval.

14. The method according to any of the preceding claims, characterized in that, A long-stator linear motor is provided as the electromagnetic transport device (1), or a planar motor is provided as the electromagnetic transport device (1).

15. An electromagnetic transport device (1) having a stator (2) and a control unit, at least one mover (3) moving along the stator (2), characterized in that, The control unit is designed to determine a first maximum value (amaxl, vmaxl) of a first trajectory (tl) for at least one movement quantity (x, v, a) of the mover (3) at a pre-described planning time point (tP), the first trajectory (tl) being configured to move the mover (3) from a starting position (A) at a starting time point (tA) to a target position (B) at a target time point (tB), and the control unit is further designed to determine a second maximum value (amax2, vmax2) of a second trajectory (t2) for the at least one movement quantity (x, v, a) of the mover (3) at the planning time point (tP), the second trajectory (t2) also being configured to move the mover (3) from the starting position (A) at the starting time point (tA) to the target position (B) at the target time point (tB), the first trajectory (tl) being selected as a target trajectory (t*) if the first maximum value (amaxl, vmaxl) is smaller than or equal to the second maximum value (amax2, vmax2), or the second trajectory (t2) being selected as the target trajectory (t*) if the second maximum value (amax2, vmax2) is smaller than the first maximum value (amaxl, vmaxl), and the mover (3) being moved according to the target trajectory (t*) starting from the starting time point (tA).

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