DE102022110546A1 - Control unit and control method - Google Patents

Abstract

The present invention relates to a control unit and a control method for controlling a movement of a machine while taking variable dynamic limits of the machine into account. The control unit as well as the control method can be used in particular to calculate the trajectory of the movement of a coordinate measuring machine, but are not limited to this purpose.

Description

The present invention relates to a control unit for controlling a movement of a machine part of a machine with at least one movable axis. The present invention further relates to a control method for controlling a movement of a machine part of a machine with at least one movable axis. Furthermore, the present invention also relates to a computer program product and the machine itself, which has such a control unit.

The control unit according to the present invention is preferably used in a device for dimensional measuring. Such a device can be, for example, a coordinate measuring machine, a robot that is used for dimensional measuring, or another dimensional measuring device. However, it should be noted that the control unit and the control method according to the present invention are not limited to this application. They can also be used in any other machines with at least one movable axis, the movement plan of which presents similar problems to those in coordinate measuring machines or robots for dimensional measurement.

Dimensional measuring devices in the present sense are, for example, coordinate measuring machines or microscopes. Roughness measuring devices or other devices for measuring distances and/or surface properties of an object are also understood to be dimensional measuring devices in the present sense.

Coordinate measuring machines with tactile and/or optical measuring sensors are used in dimensional measurement technology to determine the shape of a workpiece surface, for example by scanning. Since dimensional measurement technology is generally used in industries in which very high levels of accuracy are required, for example for subsequent processing steps or for quality assurance, error-free measurement execution is of great importance.

In order to ensure a reproducible, error-free measuring process of a coordinate measuring machine, the most detailed planning and control of the measuring process is necessary. For this purpose, it is particularly necessary to define various measurement parameters and machine-related control parameters in the form of setting parameters. These setting parameters can include, for example, a number of measuring points to be approached, the type of measurements to be carried out at the measuring points and/or a measuring direction.

As soon as these so-called measurement tasks have been determined, the measurement path must be determined or calculated in order to fully plan the measurement process and in the course of this the speed and acceleration profile of the measuring or scanning movement must also be calculated.

For this purpose, in a first step, individual measuring points are usually specified manually by the user and/or based on CAD data of the object to be measured. A rough measurement path is then created in a superimposed software layer that is installed in a computing unit, for example a server, which has a temporal sequence of discrete spatial planning points at a certain clock rate. These spatial planning points are written by the superimposed software layer to the control unit, which preferably carries out real-time control. The control unit then interpolates a certain number of spatial intermediate points between the individual spatial planning points. This is due, among other things, to the fact that the control unit typically has a higher clock rate than the higher-level software layer. With the help of the interpolated spatial intermediate points, target position values are obtained for each control cycle of the control unit.

An exemplary control method, which generates control data in the form of point clouds from the geometry data of the measurement object and calculates a speed and acceleration profile from the distances between the individual points to one another, with which the coordinate measuring machine moves its probe, is from the EP 0 762 250 A1 known.

Although that comes from the EP 0 762 250 A1 Although well-known control procedures have been established in practice, there is still reason for improvement.

The already known control method makes very strong simplifications, which are due, among other things, to the fact that the already known control method comes from a time when the computing power of such control units was lower and, in particular, real-time computing power was only available to a limited extent.

In the from the EP 0 762 250 A1 With the known control method, a trajectory created as a spline is determined from the individual planning points and it is determined that the individual planning points, which are used as base points for the spline, travel through the individual planning points, which are used as base points for the spline, at an equidistant time Need to become. In other words, according to this method, a fixed number of planning/base points must be passed through per unit of time. Speed and acceleration are already determined. Dynamic limits, i.e. maximum permissible values for speed and acceleration of the individual machine axes that are defined on an axis-by-axis basis, cannot be taken into account, or at least not reliably. It is the responsibility of the higher-level software layer to take this into account.

The higher-level software layer handles this, for example, as in EP 0 762 250 A1 described and delivers planning points to the control, which are then executed at a fixed time cycle. In order to generate the temporal sequence of the planning points, the maximum speed is first determined at defined points so that the centrifugal acceleration resulting from the curvature of the trajectory is just as large as the permitted acceleration. The speed along the path is defined by the geometric distance between two planning points, the acceleration as its derivative, i.e. analogously as the difference between two speed values. Tangential and centripetal acceleration are considered and limited independently of each other as scalar quantities.

Dynamic limits that vary locally or over time are determined from the EP 0 762 250 A1 known procedures are not taken into account.

From a pre-registration by the applicant that was not yet published at the time of this registration (registration number: DE 10 2021 102 619 ) a control method emerges, the aim of which is that the real-time control takes over the entire temporal behavior of a machine travel command. This means that it is no longer necessary for the planning points transmitted by the superimposed software layer to comply with the speed and acceleration limits of the individual axes of the measuring machine.

Although this control method has proven to be quite advantageous, this method is still associated with a comparatively high amount of computing effort that must be applied for real-time control.

It is therefore an object of the present invention to provide a control unit and a corresponding control method that enables reliable compliance with the dynamic limits of the machine, can be implemented on a real-time controller and enables a dynamic response to changes in the dynamic limits of the machine. In particular, it is a task to enable a dynamic response to changes in the dynamic limits of the machine within the real-time control, despite the described division of tasks between the superimposed software layer and the real-time control.

• - eine vorgegebene zeitliche Abfolge diskreter räumlicher Planungspunkte zu empfangen;
• - eine zeitliche Abfolge einer Vielzahl von räumlichen Zwischenpunkten zwischen den Planungspunkten durch Interpolation anhand einer von einem skalaren Bahnparameter abhängigen mathematischen Funktion zu berechnen, wobei ein Wert des Bahnparameters zur Berechnung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten jeweils zwischen den Planungspunkten mit einer Bahnparametergeschwindigkeit, welche ein Maß für die betragsmäßige Änderung des Bahnparameters pro Zeitinkrement ist, verändert wird;
• - anhand von Eingangsinformationen ein unvorhergesehenes, dynamisches Ereignis, das eine Anpassung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten notwendig macht, zu identifizieren und einen der Anpassung entsprechenden Anpassungsbetrag anhand der Eingangsinformationen mithilfe einer vordefinierten mathematischen Logik zu berechnen;
• - die Bahnparametergeschwindigkeit im Falle der Identifikation eines unvorhergesehenen, dynamischen Ereignisses bei der Berechnung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten basierend auf dem berechneten Anpassungsbetrag zu verändern; und
• - das Maschinenteil zur Bewegung entlang der berechneten zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten zu steuern.

This object is achieved according to a first aspect of the present invention by a control unit according to claim 1, wherein the control unit is set up to:

• - to receive a predetermined temporal sequence of discrete spatial planning points;
• - to calculate a temporal sequence of a large number of spatial intermediate points between the planning points by interpolation using a mathematical function dependent on a scalar path parameter, whereby a value of the path parameter is used to calculate the temporal sequence of the large number of spatial intermediate points between the planning points with a path parameter speed, which is a measure of the absolute change in the path parameter per time increment;
• - based on input information, identify an unforeseen, dynamic event that requires an adjustment of the temporal sequence of the plurality of spatial intermediate points and calculate an adjustment amount corresponding to the adjustment based on the input information using a predefined mathematical logic;
• - to change the trajectory parameter speed in the event of identification of an unforeseen, dynamic event when calculating the temporal sequence of the plurality of spatial intermediate points based on the calculated adjustment amount; and
• - to control the machine part to move along the calculated temporal sequence of the large number of spatial intermediate points.

According to a second aspect of the present invention, a machine with a control unit of the above-mentioned type is provided.

• - Empfangen einer vorgegebenen zeitlichen Abfolge diskreter räumlicher Planungspunkte;
• - Berechnen einer zeitlichen Abfolge einer Vielzahl von räumlichen Zwischenpunkten zwischen den Planungspunkten durch Interpolation anhand einer von einem skalaren Bahnparameter abhängigen mathematischen Funktion, wobei ein Wert des Bahnparameters zur Berechnung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten jeweils zwischen den Planungspunkten mit einer Bahnparametergeschwindigkeit, welche ein Maß für die betragsmäßige Änderung des Bahnparameters pro Zeitinkrement ist, verändert wird;
• - Identifizieren eines unvorhergesehenen, dynamischen Ereignisses, das eine Anpassung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten notwendig macht, anhand von Eingangsinformationen und Berechnen eines der Anpassung entsprechenden Anpassungsbetrags anhand der Eingangsinformationen mithilfe einer vordefinierten mathematischen Logik;
• - Verändern der Bahnparametergeschwindigkeit im Falle der Identifikation eines unvorhergesehenen, dynamischen Ereignisses bei der Berechnung der zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten basierend auf dem berechneten Anpassungsbetrag; und
• - Steuern des Maschinenteils zur Bewegung entlang der berechneten zeitlichen Abfolge der Vielzahl von räumlichen Zwischenpunkten.

The above-mentioned task is further solved by a control method according to claim 13, which has the following steps:

• - Receiving a predetermined temporal sequence of discrete spatial planning points;
• - Calculating a temporal sequence of a large number of spatial intermediate points between the planning points by interpolation using a mathematical function dependent on a scalar path parameter, wherein a value of the path parameter for calculating the temporal sequence of the plurality of spatial intermediate points between the planning points is changed with a path parameter speed, which is a measure of the absolute change in the path parameter per time increment;
• - identifying an unforeseen, dynamic event that requires an adjustment of the timing of the plurality of spatial intermediate points based on input information and calculating an amount of adjustment corresponding to the adjustment based on the input information using predefined mathematical logic;
• - Changing the trajectory parameter speed in the event of identification of an unforeseen, dynamic event when calculating the temporal sequence of the plurality of spatial intermediate points based on the calculated adjustment amount; and
• - Controlling the machine part to move along the calculated temporal sequence of the multitude of spatial intermediate points.

Furthermore, a computer program product according to the present invention is provided, which has software which, when executed on a computer, is designed to carry out the above-mentioned method.

The following essentially explains the control unit according to the first aspect of the present invention. However, it is understood that the following explanations and the features defined in the dependent claims 2-10 relate not only to the control unit according to the invention, but also in an equivalent manner to the control method according to the invention.

In the control unit according to the invention, this is the case EP 0 762 250 A1 The well-known principle of task distribution between the superimposed software layer and the real-time control implemented in the control unit is retained, according to which a temporal sequence of discrete spatial planning points is specified by the superimposed software layer and written to the control unit. This temporal sequence of the discrete spatial planning points is specified by the superimposed software layer in such a way that the speed and acceleration limits of the individual axes of the machine are adhered to.

According to the invention, however, the control unit now has additional functionality that allows a reaction to changes in the dynamic limits (speed and acceleration limits) of the machine.

For this purpose, as previously known, the control unit calculates a time sequence of a large number of spatial intermediate points between the individual planning points by interpolation based on a mathematical function dependent on a scalar path parameter. This mathematical function is preferably an nth degree polynomial with n ≥ 3. In particular, but not necessarily, this mathematical function includes a spline function.

To calculate the spatial intermediate points, four or more of the temporally successive planning points are preferably used as support points for a spline. Between two planning points, the value of the path or spline parameter is then typically changed in amount increasing from 0 in constant steps in order to calculate the individual intermediate points between these two planning points. In this way, a temporal sequence of a large number of spatial intermediate points is obtained, with each intermediate point being assigned a corresponding time value and the time increment or the time distance between two successive intermediate points being constant, as is also the case for those specified by the superimposed software layer temporal sequence of the spatial planning points applies. The time interval between two successive intermediate points is correspondingly smaller than the time instance between two successive planning points, depending on the number of intermediate points between two successive planning points. As previously known, this adjusts the clock rate of the superimposed software layer to the clock rate of the control unit.

However, unlike what was previously known, the control unit according to the invention is able to dynamically change the path parameter speed in the event of an unforeseen, dynamic event that makes it necessary to adapt the temporal sequence of the large number of spatial intermediate points. For this purpose, an adjustment amount is calculated using predefined mathematical logic according to the input information that indicates the unforeseen, dynamic event, and the path parameter speed is changed based on this calculated adjustment amount.

However, it is important to understand that the path parameter speed mentioned is not the same as the machine speed or the absolute speed of the moving machine part. Between these two sizes there is a linear relationship. However, the path parameter speed is a measure of the amount of change in the path parameter per (constant) time increment. In other words, the path parameter speed expresses the amount by which the value of the path parameter is changed per time increment in order to calculate the coordinates of the temporally successive intermediate points using the mathematical function dependent on the path parameter (e.g. spline function). Expressed figuratively, the trajectory parameter speed is a measure of how quickly the trajectory described by the mathematical function is traversed.

The present invention therefore follows the idea of not switching off or stopping the machine completely in the event of an unforeseen, external, dynamic event, but rather adjusting the path parameter speed depending on the event based on a predefined mathematical logic.

Compared to the pre-registration mentioned at the beginning DE 10 2021 102 619 This approach involves significantly less computing effort within the control unit. Since the specified time sequence of the spatial planning points specified by the superimposed software layer already comply with the dynamic limits of the machine and the intermediate points calculated by the control unit are calculated on the basis of these planning points, it is still ensured that the dynamic limits of the machine are still observed the approach proposed here must be adhered to. In addition, the jerk limitation specified by the superimposed software layer is almost always retained. This makes it very easy to react to unforeseen events within the control unit while adhering to the specified dynamic limits, without requiring a lot of computing effort.

The above task is therefore completely solved.

An unforeseen, dynamic event in the present sense can include, for example, a triggering of a safety device of the machine, a departure from a predetermined working area of the machine and/or an impending collision with another machine, a subject or an object.

If such an event is recognized on the basis of input information received by the control unit, the path parameter speed is reduced, for example, in accordance with the event, whereby the machine speed is consequently also reduced accordingly. The adjustment amount by which the path parameter speed is adjusted depends on the respective event and is calculated by the mathematical logic stored in the control unit. As already mentioned, path fidelity, i.e. the need for the moving machine part to ultimately adhere to the specified chronological sequence of planning points, is automatically given.

According to one embodiment, the adjustment amount for adjusting the path parameter speed depending on the unforeseen, dynamic event corresponding to the input information is a time-constant adjustment amount or a time-varying adjustment amount.

If the event is, for example, the triggering of a light barrier, through which the machine speed must be reduced to a predetermined amount, the adjustment amount by which the path parameter speed is reduced is set to a time-constant adjustment amount, so that the machine speed remains constant for the duration of the event is permanently limited to a constant maximum value. If, on the other hand, a departure from the working area of the machine or a collision with another machine is detected, so that the machine has to come to a standstill at a certain point, the adjustment amount by which the path parameter speed is reduced can be designed to vary over time, so that the machine or the moving machine part is consequently braked gradually to zero. The cases mentioned are explained in more detail below.

According to one embodiment of the present invention, the input information includes signals that the control unit receives from a detector and/or that are obtained by evaluating the predetermined temporal sequence of the discrete spatial planning points.

The signals are preferably redundant signals, which are typically used for such applications in machine safety. The detector can be, for example, a light barrier, a protective door, a camera and/or a switch. All of these safety devices are designed to detect the presence and/or entry of a person or other object into a dangerous area of the machine and, based on this, to pass on appropriate signals to the control unit in order to slow down the machine speed or switch off the machine .

The moving machine part leaving a predetermined working area of the machine can also be determined within the control unit based on the temporal sequence of planning points specified by the superimposed software layer. An additional detector/sensor does not necessarily have to be used to detect an unforeseen event. The identification of such an event can in principle also take place within the control unit on the basis of the control information that is already available and which the control unit receives from the higher-level software layer.

According to a further embodiment, the input information contains information that requires a reduction of a maximum permitted speed of the machine part to a predetermined value v _{max_reduced} , and wherein the predefined mathematical logic for calculating the adjustment amount includes the calculation of a quotient v _{max_reduced} / v _{max_planned} , where v _{max_planned} is a maximum speed of the machine part, which is the basis of the specified temporal sequence of the discrete spatial planning points.

Such a calculation of the adjustment amount for adjusting the path parameter speed is particularly suitable if the unforeseen, dynamic event involves the triggering of a safety device on the machine, due to which the maximum machine speed should be limited to a maximum permitted amount.

With the quotient v _{max_reduced} / v _{max_planned,} the variable v _{max_reduced} corresponds to the maximum speed of the machine part permitted at the current time. This variable changes when a dynamic event occurs. In contrast, the variable v _{max_planned} is the maximum speed of the machine part during the complete temporal sequence of spatial planning points, which is specified by the superimposed software layer. Both v _{max_reduced} and v _{max_planned} can be specified for individual machine parts or for the entire moving machine. Likewise, the mentioned speed variables v _{max_reduced} and v _{max_planned} can be described axis by axis, so that these speed values differ for different axes of the machine or the moving machine part.

At most, the variable v _{max_planned} can correspond to the maximum possible speed of the machine part or the axis under consideration. However, since it is also conceivable that the planning points that come from the superimposed software layer were not planned at all with the maximum possible speed of the respective axis or the maximum possible machine speed, the value v _{max_planned} does not necessarily correspond to the maximum possible speed the axis or the machine.

According to a preferred embodiment, the control unit is set up to calculate v _{max_planned} based on the predetermined time sequence of the discrete spatial planning points.

In other words, according to this embodiment, the control unit extracts v _{max_planned} by calculating the maximum speed that results from the temporal sequence of the spatial planning points planned by the superimposed software layer. For this purpose, the spatial distances between the individual planning points are considered and compared with each other, which is preferably done on an axis-by-axis basis. Ultimately, this should identify the largest spatial distance between two immediately consecutive planning points, since this leads to the largest speed value v _{max_planned} by dividing by the known constant time distance between the planning points. In this way, the control unit can easily calculate v _{max_planned} from the information received from the superimposed software layer.

The calculation of v _{max_planned} is so important because a ratio of v _{max_reduced} to the maximum possible speed would otherwise always lead to an excessive speed reduction in the event of an event if the originally planned time sequence of the planning points was not based on the maximum possible machine speed .

According to a further embodiment, the input information contains information that requires the machine part to come to a standstill at a predetermined first planning point, the control unit being set up to identify a preceding second planning point at which a deceleration of the speed of the machine part begins, and where the predefined mathematical logic for calculating the adjustment amount includes the calculation of a time-varying adjustment amount, in which the adjustment amount is gradually adjusted from planning point to planning point, starting from the second planning point.

Preferably, the adjustment amount is based on the second planning point of Planning point to planning point adjusted in constant steps. However, this does not necessarily have to be the case, but it simplifies the calculation.

Such a calculation of the adjustment amount for adjusting the path parameter speed comes into question in particular if the unforeseen, dynamic event is an event as a result of which the machine must come to a standstill, for example when leaving a predetermined working area of the machine and/or an impending one Collision with another machine, subject or object.

In such a case, as described, the planning point is first identified (herein referred to as the “second planning point”) at which the braking process must begin. Then, when calculating the time sequence of the large number of spatial intermediate points, the path parameter speed is gradually reduced from planning point to planning point by adjusting the adjustment amount from planning point to planning point accordingly, so that the machine reaches the end point to be maintained (herein referred to as the “first planning point”). comes to a standstill.

It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

• 1 ein Koordinatenmessgerät als Beispiel für eine Maschine, in der die erfindungsgemäße Steuereinheit zum Einsatz kommen kann;
• 2 ein Ablaufdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Steuerungsverfahrens;
• 3 ein Diagramm zur schematischen Veranschaulichung einer beispielhaften Bahnkurve;
• 4 ein Diagramm, das ein erstes Beispiel für eine zeitliche Veränderung eines Bahnparameters zeigt;
• 5 ein Diagramm, das ein zweites Beispiel für eine zeitliche Veränderung des Bahnparameters zeigt;
• 6 ein Diagramm, das ein drittes Beispiel für eine zeitliche Veränderung des Bahnparameters zeigt;
• 7 ein Diagramm zur Veranschaulichung einer Veränderung der Maschinengeschwindigkeit gemäß einem ersten Ausführungsbeispiel;
• 8 ein Diagramm zur Veranschaulichung der Veränderung der Maschinengeschwindigkeit gemäß einem zweiten Ausführungsbeispiel;
• 9 ein Diagramm zur Veranschaulichung einer Veränderung der Maschinengeschwindigkeit gemäß einem dritten Ausführungsbeispiel; und
• 10 ein Diagramm zur Veranschaulichung einer Veränderung der Maschinengeschwindigkeit gemäß einem vierten Ausführungsbeispiel.

Exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description. Show it:

• 1 a coordinate measuring machine as an example of a machine in which the control unit according to the invention can be used;
• 2 a flowchart of an exemplary embodiment of the control method according to the invention;
• 3 a diagram for schematically illustrating an exemplary trajectory;
• 4 a diagram showing a first example of a change in a trajectory parameter over time;
• 5 a diagram showing a second example of a change in the orbit parameter over time;
• 6 a diagram showing a third example of a change in the orbit parameter over time;
• 7 a diagram illustrating a change in machine speed according to a first embodiment;
• 8th a diagram for illustrating the change in machine speed according to a second embodiment;
• 9 a diagram illustrating a change in machine speed according to a third embodiment; and
• 10 a diagram to illustrate a change in machine speed according to a fourth exemplary embodiment.

1 shows an embodiment of an exemplary measuring device in which the control method according to the invention or the control unit according to the invention can be used. The measuring device is marked in its entirety with the reference number 100. The associated control unit is in 1 marked in its entirety with the reference number 40.

In the present example, the measuring device 100 is a coordinate measuring machine in a so-called portal design. In other exemplary embodiments, the measuring device 100 can also be a robot, for example an articulated arm robot, which is used to measure any measurement object.

This in 1 Coordinate measuring machine 100 shown has a base 10. The base 10 is preferably a stable plate, which is made of granite, for example. A workpiece holder 12 is arranged on the base 10 and is designed to hold a measurement object 14. The workpiece holder 12 can also be designed as a turntable, with the help of which the object 14 to be measured can be positioned along one or more axes.

On the base 10, a portal 16 is arranged to be displaceable in the longitudinal direction. The portal 16 serves as a movable support structure. The portal 16 has two columns projecting upwards from the base 10, which are connected to one another by a cross member and have an overall inverted U-shape.

The direction of movement of the portal 16 relative to the base 10 is commonly referred to as the Y direction. A carriage 18 is arranged on the upper cross member of the portal 16 and can be moved in the transverse direction. This transverse direction is becoming more common wisely referred to as the X direction. The carriage 18 carries a quill 20, which can be moved in the Z direction, i.e. perpendicular to the base 10.

The reference numbers 22, 24, 26 designate measuring devices by means of which the X, Y and Z positions of the portal 16, the carriage 18 and the quill 20 can be determined. Typically, the measuring devices 20, 24, 26 are glass scales which serve as measuring scales. These measuring scales are designed in conjunction with corresponding reading heads (not shown here) to measure the current position of the portal 16 relative to the base 16, the position of the carriage 18 relative to the upper crossbar of the portal 16 and the position of the quill relative to the To determine carriage 18.

A measuring head 28 is arranged at a lower, free end of the quill 20. The measuring head 28 is set up to record measuring points on the measurement object. The measuring head is part of a measuring sensor, the measuring sensor system of which can be arranged separately from the measuring head 28 or integrated into it and can be connected to it via one or more cables or wirelessly. The measuring head 28 has a tactile stylus 30 projecting in the Z direction towards the base.

The stylus 30 is set up to scan a surface of the measurement object 14 using a probe 32. The probe 32 is, for example, a ruby ball. However, instead of a tactile stylus, an optical measuring probe, which optically scans the measurement object 14, can also be used.

When scanning the surface of the measurement object 14, the probe 32 generates an electrical measurement signal in the measurement head 28, on the basis of which the dimensional properties of the measurement object 14 to be measured can be determined. To approach a measuring point on the measurement object 14, the measuring head 28 is moved relative to the workpiece holder 12 or relative to the measurement object 14. For this purpose, the movements of the portal 16 relative to the base 10, the carriage 18 relative to the portal 16 and the quill 20 relative to the carriage 18 are controlled by a control unit 40 by a large number of predefined control commands, for example via a CNC control.

The control unit 40 is in the 1 spaced from the coordinate measuring machine 100 (eg next to the coordinate measuring machine 100) arranged as a separate unit and connected to the base 10 of the coordinate measuring machine 100 via one or more cables. Of course, this connection can also be designed to be wireless.

The control unit 40 has a computing unit 34 and a display device 36. The computing unit 34 is typically a computer that can be designed as a PC or physical server or as a cloud server. The display device 36 is preferably a screen or a display.

Typically, the control unit 40 is used not only to control the coordinate measuring machine 100, but also in advance of the measurement to support a user in creating a measurement plan.

Before a measurement of the measurement object 14 begins, a measurement sequence is typically defined in a measurement plan. In particular, it is determined which geometric elements (measuring elements) of the measurement object 14 are to be measured and which dimensional measurement variables (test characteristics) of these measuring elements are to be quantitatively recorded by the coordinate measuring machine 100. These measurement elements and test characteristics are typically set manually by a user. However, they can also be determined automatically or at least partially automatically from a CAD data set.

As soon as the measuring elements and the test characteristics are available, the measuring process is calculated in the control unit 40. In particular, a trajectory is defined along which the probe 32 is to be moved. A superimposed software layer for trajectory planning first determines a predetermined temporal sequence of discrete spatial planning points. The point sequence (here called “time sequence of discrete spatial planning points”) is written to the control by the superimposed software layer by transporting the points to the control point by point one after the other using a command. 3 shows an exemplary trajectory 44, which is calculated based on several planning points 42. As a rule, the planning points are calculated by the superimposed software layer in such a way that there is always a constant time distance between two immediately consecutive points. This constant time distance is, for example, 100 ms, but it can also have any other value, for example in the range of 50 ms - 300 ms, but must always be constant during a planning point stream.

During planning, the superimposed software layer ensures that the spatial distance between two immediately successive planning points 42 is selected so that the speed and acceleration values zen of each axis of the coordinate measuring machine 100 must be adhered to.

Since the real-time control implemented in the control unit 40 generally operates at a higher clock rate than the superimposed software layer, for example with a clock rate of 1000 Hz, the real-time control requires a target position value every 1 ms. Therefore, the clock rate of the time sequence of the spatial planning points 42 obtained from the superimposed software layer in step S101 is adjusted in step S102 to the clock rate of the real-time control (see 2 ). For this purpose, the control unit 40 calculates in step S102 a time sequence of a large number of spatial intermediate points 46 between two of the immediately successive planning points 42. In 3 This is indicated schematically for the planning point section between the planning points 42'' and 42'''. The calculation of the temporal sequence of the intermediate points 46 is carried out by interpolation using a mathematical function dependent on a scalar path parameter u. This mathematical function is, for example, a third-order spline, which results from the following calculation formula: $$\text{Q}\left(\text{u}\right)={\text{a}}_3\cdot {\text{<figure-callout id="3" label="u" filenames="DE102022110546A1\_0009.png" state="{{state}}">u</figure-callout>}}^3+{\text{a}}_2\cdot {\text{<figure-callout id="2" label="u" filenames="DE102022110546A1\_0009.png" state="{{state}}">u</figure-callout>}}^2+{\text{a}}_1\cdot \text{u}+{\text{a}}_{\text{0}}$$

In order to calculate the coefficients a _x of the spline, the control unit 40 uses, for example, four temporally successive planning points 42 as support points. After the coefficients a _x have been determined, the intermediate points 46 can be calculated using the determined spline by varying the path parameter u.

If, for example, the superimposed software layer has a clock rate of 10 Hz and the control unit 40 or the real-time control has a clock rate of 1000 Hz, a time interval between two immediately successive intermediate points 46 of 1 ms is selected in step S102. This results in, for example, a hundred intermediate points 46 between two successive planning points 42. These hundred points can be determined using the above formula (1) by changing the value of the path parameter u as a function of time. Formula (1) is calculated 100 times, with a planning point interval of 100 ms. Starting from a planning point 42, for example, the value of the path parameter u is increased in amount by 0.01 in equidistant time steps starting from 0, so that at u = 0.99 the intermediate point 46 is reached, which coincides with the next planning point 42. 4 shows an exemplary time course of the change in the value of the path parameter u, whereby, for example, the intermediate points 46 between the planning points 42'' and 42''' are calculated in the time range 0-100 ms and the intermediate points 46 between the planning points 42' are calculated in the period 100-200 ms. '' and 42'''' can be calculated.

It is important to note at this point that the coefficients a _x are recalculated for each spline section between two planning points 42. The support points of the spline are each moved forward by a planning point 42. Once the new coefficients a _x have been calculated, the values of the orbit parameter u are varied again from 0 to 0.99. In this way, the coordinate measuring machine travels exactly at the speeds and accelerations that are communicated to the control unit 40 by the superimposed software layer based on the planning points. All speeds and accelerations as well as the speed and acceleration limits of the individual axes of the coordinate measuring machine 100 are therefore still handled by the superimposed software layer.

According to the invention, it is now provided that the control unit 40 can use input information to identify an unforeseen, dynamic event that makes it necessary to adapt the temporal sequence of the intermediate points 46. If such an event is identified by the control unit 40, it calculates an adjustment amount corresponding to the adjustment based on the input information using predefined mathematical logic (see step S103).

In step S104, the path parameter speed is then changed when calculating the intermediate points 46 based on the calculated adjustment amount. Exactly how this is done is explained below.

In 5 An example of the change in the temporal behavior of the running parameter u is shown. In the first time interval between 0 and 100 ms, the coordinate measuring machine 100 is moved exactly at the speed that was specified by the superimposed software layer through the planning points 42 (similar to this in the example 4 was the case). In the second time interval between 100 and 300 ms, the path parameter speed is reduced by 50% by the control unit 40 due to a detected dynamic event. In the present case, the path parameter speed is understood to mean the absolute change in the path parameter per time increment (in the present case 1 ms).

The reduction of the orbit parameter speed in the mentioned second time interval in 5 can be seen from the slope, which is only half as large, in the second time interval 100-300 ms in the ver right at the first time interval 0-100 ms. The value of the orbit parameter u is only increased per millisecond by half of the increase amount used in the first time interval.

This principle thus causes a stretching of the time axis, so to speak, in which switching is made from one planning point 42 to the next.

6 shows another example to illustrate that the change in the trajectory parameter speed can not always only occur when moving from one control point to the next, but also somewhere in between. In the in 6 The example shown is driven in the time interval 0-50 ms at exactly the speed that the superimposed software layer specifies based on the planning points 42. From 50 ms onwards, the speed is only half the speed specified by the superimposed software layer through the planning points 42.

The control unit 40 is preferably set up to prevent the bend from becoming too “sharp” during transitions from exactly the speed specified by the superimposed software layer through the planning points 42 to a reduced speed. A speed ramp is therefore implemented so that the slowest axis of the coordinate measuring machine 100 is only braked or accelerated with a maximum of the maximum permitted acceleration.

Analogous to the previously described reduction in the path parameter speed, the speed of the machine can also be increased again using the described method of manipulating the temporal behavior of the running parameter u. This is done by increasing the path parameter speed accordingly. It is therefore possible to slow down but also accelerate again within a planning point stream, which is received from the superimposed server layer.

During the braking and acceleration phases as well as during the phases in which driving is slower but at a constant speed, this procedure always ensures that the specified trajectory, which is specified by the planning points of the superimposed software layer, is adhered to becomes. Compliance with the dynamic limits of the coordinate measuring machine 100 is already in the planning points that were calculated by the superimposed software layer. This means it doesn't matter whether these planning points are moved through a little slower or faster.

The following explains an example of how the adjustment amount can be calculated to adjust the path parameter speed. This can be done, for example, using the following quotient: $${\text{v}}_{\text{max\_reduced}}/{\text{v}}_{\text{max\_planned}}$$

In formula (2) above, the variable v _{max_reduced} corresponds to the maximum speed of the machine permitted at the current time. This is a variable that can change when a dynamic event occurs. In contrast, the variable v _{max_planned} corresponds to a maximum speed of the machine, which is the basis of the specified time sequence of the planning sequence. At most, this variable v _{max_planned} can correspond to the maximum possible speed of the machine. However, since it is also conceivable that the planning points 42, which are received from the superimposed software layer, were not planned at the maximum possible machine speed, this value should not simply be used. Rather, the maximum speed at which this spline planning point sequence was generated should be calculated from the planning points 42. Otherwise, if the machine is already traveling slower than the possible maximum speed, it would slow down again.

v _{max_planned} can be calculated based on the planning points 42 as follows: While the planning points 42 are being written to the control by the superimposed software layer (at this point in time, the machine/coordinate measuring machine 100 is either still standing or has just started running through the planning points - Sequence started), the control unit 40 always calculates the distance from one control point 42 to the next on an axis-by-axis basis. This is possible from the second checkpoint 42, which is written to the control. The control unit 40 compares whether the axis-wise position distance that has just been determined is greater than the maximum axis-wise position distance that the control unit 40 has previously recognized. At the beginning, the control unit 40 sets the maximum axis-wise position distance to the value zero. In this way, the control unit 40 can very quickly calculate the maximum axis-wise position distance between two temporally successive planning points 42 in the entire planning point stream.

Every time the axis-wise position distance just determined between two temporally successive planning points 42 is greater than the previously determined maximum axis-wise position distance, the maximum speed v _max is planned and correctly scaled for the respective axis and taken over. This is done by the control unit 40 correctly scaling the current point distance (which corresponds to the first derivative of the position and thus already a speed value). This is easy to calculate because the time distance between the planning points and the overlaid software layer is known. As mentioned, this time interval is typically in the range of 50-300 ms.

If the control unit 40 has determined v _{max_planned} in the above manner, the adjustment amount for adjusting the path parameter speed can be calculated very easily using the above quotient from formula (2), provided that v _{max_reduced} is already specified and / or based on the input information that the control unit 40 receives, is changed. v _{max_reduced} corresponds to the maximum possible speed of the respective axis of the machine or at least v _{max_planned} until the control unit 40 detects an event that makes an adjustment of the path parameter speed necessary.

Such an event could be, for example, the triggering of a safety device in the machine. This would be the case, for example, if a person approaching the coordinate measuring machine 100 triggers a light barrier. In such a case, the control unit 40 receives a corresponding signal from the safety device, which causes the control unit 40 to reduce the value of v _{max_reduced} to a predefined value.

7 shows such an example in which v _{max_reduced} is suddenly reduced due to the triggering of a light barrier at a time of 5.1 s. Curve 48 shows the time course of v _{max_reduced} . The curve 50 in 7 shows the time course of the adjustment amount, which is shown here as a percentage value. Curve 52 shows the time course of the resulting machine speed. Out of 7 It can be seen that the adjustment amount 50 changes at the same times as v _{max_reduced} . This is easy to understand based on the ratio given in formula (2) above. It's still over 7 It can be seen that from the time of 5.1 s the speed of the machine or the machine axis reduces until the speed is within a permitted speed range (see curve 52). Since the specified path of the planning points 42 must also be adhered to during the braking process, braking is not constantly carried out with the full permitted acceleration, but only with the acceleration that the trajectory curve currently allows.

8th On the other hand, shows the acceleration process after the safety device (e.g. the light barrier) is left again in the example above. From the time of 12.1 s onwards, the currently maximum permitted speed v _{max_reduced} (see curve 48) and the calculated adjustment amount (see curve 50) jump upwards. The corresponding axis of the machine then begins to increase the speed until the maximum possible machine speed or at least the maximum speed specified by the planning points is reached again (see curve 52).

9 shows a further example which illustrates how the control unit 40 reaches an end position (software end position and/or fence grid) when an end position is reached. In other words, this example refers to a case in which the machine threatens to leave a specified work area.

In such a case, the control unit 40 must initiate a braking process before the event occurs (exceeding the end position), so that the machine comes to a stop exactly at the end position. The control unit is therefore set up to carry out pre-processing of the planning points as soon as the planning points 42 are received from the superimposed software layer. Since this typically happens some time before the respective planning points are executed, this can be viewed as a type of lookahead procedure.

The lookahead method mentioned can be implemented, for example, as follows: Similar to the previous examples 7 and 8th While the control unit 40 is writing the planning points 42 received from the superimposed software layer to the control, an evaluation of the planning points is carried out. The control unit 40 checks each individual planning point 42 to see whether it is within a permitted working area of the machine. If one of these planning points 42 is identified outside of the machine's workspace, an indication, such as a flag, is set, which indication/flag indicates that an event will occur in the near future. In addition, each planning point 42, which is received from the superimposed software layer, is numbered in ascending order. The control unit 40 therefore stores the planning point number at which the machine must have come to a standstill. The control unit 40 then calculates the maximum braking time based on the maximum possible speed and the maximum possible acceleration of each individual axis. The control unit 40 then uses the longest brake time of all axes and multiplies them, for example, by a factor of 1.5. This additional factor may be necessary because the axes of the machine cannot always brake with the maximum possible acceleration, since the trajectory, which is specified by the planning points 42, must be adhered to. In the next step, based on the maximum braking time, the control unit 40 can now calculate the planning point 42 from which the braking process must begin. The control unit 40 stores the corresponding number of the identified planning point.

Since an indication or a flag was already set in the above-mentioned manner in the preprocessing that an event will occur while the planning points are being driven, it can now always be checked when the planning points 42 are being driven whether the planning point with the number is currently at which the braking process must begin. Once this planning point number is reached, the following steps are processed by the control unit 40: First, the control unit 40 calculates the difference in the planning point numbers from the start to the end of the braking process. In this way, the control unit 40 calculates the number of planning points within which the machine must be braked. The full 100%, which corresponds to driving at the maximum speed specified by the planning points 42, is then divided by the number of planning points. The control unit 40 thus calculates how much additional less speed may be permitted per completed planning point 42. In the next step, the new adjustment amount is calculated as a percentage that is lower than the full 100% of the current maximum permitted speed. For each planning point 42 passed through, the maximum permitted speed is then further reduced in percentage terms, so that a kind of braking ramp is created.

The braking ramp mentioned above can be expressed, for example, using the following formula: $$\text{processNew}=\left(100\text{/pointAnzComp}\right)\cdot \text{pointAnzBistillst}$$

In formula (3) above, the variable punktAnzKomp corresponds to the complete number of planning points from the start of the braking process until the machine comes to a standstill. The variable punktAnzBBisStillst corresponds to the number of planning points 42 that have not yet been processed from the current point in time until the machine comes to a standstill.

This means that after each planning point is traveled, the adjustment amount or the percentage by which the path parameter speed is reduced is reduced. If the variable punktAnzBbisStillst has reached the value 0, the path parameter speed is also 0. The machine would therefore stop. However, it may be that the end position has not yet been completely reached. Therefore, you can then continue driving very slowly at 1 or 2% permitted speed until a separate control function has detected that the end position has been reached and the control unit 40 reacts accordingly.

In 9 An example of such a braking process due to a software end position is illustrated. It can be seen that the braking process begins again from approx. 2.6 s. From then on, the adjustment amount 50 begins to gradually reduce accordingly. After each individual planning point 42 has been reached, the adjustment amount 50 is reduced in accordance with formula (3) above.

The time course of v _{max_reduced} is based on curve 48 in 9 recognizable. As can be seen, v _{max_reduced} is initially reduced parallel to the adjustment amount 50. v _{max_reduced} then jumps back to the maximum possible speed of the machine axis under consideration at approx. 4 s. The reason for this is that in this case, from the point in time mentioned onwards, another axis of the machine has an even lower speed than is permitted for this axis in question. Accordingly, the staircase from v _{max_reduced} continues on another axis of the machine. However, since the adjustment amount 50 is based on the axis with the slowest permitted speed across all axes, the curve 50 still continues downwards in a staircase manner from the point in time 4 s.

At turn 52 in 9 the reduction in machine speed can be seen. In this example, the machine comes to a standstill after approx. 5.6 s. At this point the machine is then very precisely in the software end position.

In addition to the advantages already described, the procedure described above has the following advantage: If the machine is already traveling at a slower speed for some reason, then it continues to travel exactly at the same speed as before until the control unit 40 adjusts the adjustment amount prozNew to a correspondingly smaller value . This means that the machine only then begins to brake further.

The last mentioned effect can be seen using the in 10 Explain in more detail the example shown. 10 shows an exemplary time course for a case in which an event is first detected which results in a one-off, time-constant adjustment amount of the path parameter speed (for example the triggering of a safety device) and then an event occurs which results in a time-varying adjustment amount of the path parameter speed, i.e a step-like braking (e.g. leaving the specified working range of the machine (software end position)).

Out of 10 For example, it can be seen that the braking phase from approx. 9 s is much shorter than in the previous example 9 . This is because the path parameter speed was reduced much earlier (from approx. 1.5 s) due to the safety device being triggered.

In order to keep the above-mentioned basic principle the same for all applications, the control unit 40 can be set up to calculate the maximum permitted path parameter speed based on reaching an end position via the percentage adjustment amount prozNeu and the determination of v _{max_planned} . This value is then assigned to the variable v _{max_reduced} if the speed has to be reduced due to end positions. In this way, end positions can be controlled using the same basic principle of the method as was described in the above-mentioned case of triggering a safety device.

It should be noted that the control principle mentioned here can also be applied to the so-called dynamic stand locking. Dynamic stand locking describes a cage around the tool center point of a coordinate measuring machine. This is particularly necessary if two coordinate measuring machines share the same measuring or traversing space. A virtual cage is then stretched around the tool center point on each of the two coordinate measuring machines. The first coordinate measuring machine is informed of the position and extent of the cage of the second coordinate measuring machine via a network. This also works in the other direction.

The control unit can thus detect each of the two coordinate measuring machines when its cage would come into contact with the cage of the other coordinate measuring machine. At least one machine must have come to a standstill by this point.

If, for example, the second coordinate measuring machine moves away again and makes room for the first coordinate measuring machine, it can be achieved with the help of the control method according to the invention that the first coordinate measuring machine then even moves on again.

In comparison to the last described application of reaching an end position or leaving a predetermined working range of the coordinate measuring machine, the dynamic stand locking describes, so to speak, a software end position that can change constantly, even while a planning point stream is being processed.

In this case, too, the braking time of the slowest axis is determined again, i.e. the longest braking time of the machine. The control unit 40 can thus calculate how many planning points it has to “look into the future” so that braking is still possible. Now, because of the dynamic changeability, while the planning points are being driven, all future planning points must be checked within the longest braking time after each planning point has been reached to see whether they violate the dynamic software end position or not. If a violation of the dynamic software end position is detected by the control unit 40, a braking process is initiated in an analogous manner as described above.

If the control unit 40 then detects that the number of planning points within the braking process does not become smaller, but remains larger or the same again (which indicates that the other coordinate measuring machine is moving away again), then the braking process does not slow down to a standstill, but the control unit starts again to increase the path parameter speed and thus the machine speed.

When the coordinate measuring machine has come to a standstill, the control unit 40 preferably does not stop processing the planning points. Instead, the control unit waits to see whether the other coordinate measuring machine moves away again. If this is the case, the number of planning points within the braking range increases again until the dynamic software end position is reached. Then the control unit 40 can cause the coordinate measuring machine to accelerate again.

All of this can be achieved with the lookahead method described, in that the control unit 40 identifies the future planning points 42, which it receives from the superimposed software layer but which have not yet been processed, and uses them to calculate whether these within a dynamic software end position. It is understood that this type of check must be done frequently as the software end position can change very quickly in the case of dynamic stand locking. It is therefore preferably carried out at the clock rate of the control unit 40 or at least at the clock rate of the superimposed software layer.

In contrast, the above-mentioned check of the normal software end positions, fence grids, etc. only needs to be carried out once when the planning points are received.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 0762250 A1 [0008, 0009, 0011, 0012, 0013, 0022]
• DE 102021102619 [0014, 0029]

Claims (14)

Control unit (40) for controlling a movement of a machine part of a machine (100) with at least one movable axis, the control unit (40) being set up to: - to receive a predetermined temporal sequence of discrete spatial planning points (42); - to calculate a temporal sequence of a large number of spatial intermediate points (46) between the planning points (42) by interpolation based on a mathematical function dependent on a scalar path parameter (u), whereby a value of the path parameter (u) is used to calculate the temporal sequence of the multitude from spatial intermediate points (46) between the planning points (42) with a path parameter speed, which is a measure for the absolute change in the path parameter (u) per time increment, is changed; - based on input information, to identify an unforeseen, dynamic event that requires an adjustment of the temporal sequence of the plurality of spatial intermediate points (46) and to calculate an adjustment amount corresponding to the adjustment based on the input information using a predefined mathematical logic; - to change the trajectory parameter speed in the event of identification of an unforeseen, dynamic event when calculating the temporal sequence of the plurality of spatial intermediate points (46) based on the calculated adjustment amount; and - to control the machine part to move along the calculated time sequence of the large number of spatial intermediate points (46). Control unit according to Claim 1 , wherein the unforeseen, dynamic event (i) a triggering of a safety device of the machine (100), (ii) a departure from a predetermined working area of the machine (100), and / or (iii) an impending collision with another machine (100) , a subject or object. Control unit according to Claim 1 or 2 , whereby the adjustment amount is a time-constant adjustment amount or a time-varying adjustment amount depending on the unforeseen, dynamic event corresponding to the input information. Control unit according to one of the Claims 1 - 3 , wherein the input information includes signals that the control unit (40) receives from a detector and/or that are obtained by evaluating the predetermined temporal sequence of the discrete spatial planning points (42). Control unit according to Claim 4 , where the signals are redundant signals, and the detector comprises a light barrier, a protective door, a camera and / or a switch. Control unit according to one of the Claims 1 - 5 , wherein the input information contains information that requires a reduction of a maximum permitted speed of the machine part to a predetermined value v _{max_reduced} , and wherein the predefined mathematical logic for calculating the adjustment amount includes the calculation of a quotient v _{max_reduced} / v _{max_planned} , where v _{max_planned} is a maximum Speed of the machine part is which forms the basis of the predetermined temporal sequence of the discrete spatial planning points (42). Control unit according to Claim 6 , wherein the control unit (40) is set up to calculate v _{max_planned} based on the predetermined time sequence of the discrete spatial planning points (42). Control unit according to one of the Claims 1 - 7 , wherein the input information contains information that requires the machine part to come to a standstill at a predetermined first planning point, the control unit (40) being set up to identify a preceding second planning point at which a deceleration of the speed of the machine part begins, and wherein the predefined mathematical logic for calculating the adjustment amount includes the calculation of a time-varying adjustment amount, in which the adjustment amount is gradually adjusted from planning point (42) to planning point (42), starting from the second planning point. Control unit according to Claim 8 , whereby the adjustment amount is adjusted in constant steps from planning point (42) to planning point (42), starting from the second planning point. Control unit according to one of the Claims 1 - 9 , where the mathematical function dependent on the scalar path parameter (u) comprises a spline function. Machine (100) with a control unit (40) according to one of the preceding claims. Machine (100) according to Claim 11 , wherein the machine (100) comprises a device for dimensional measuring. Control method for controlling a movement of a machine part of a machine (100) with at least one movable axis, the method having the following steps: - receiving a predetermined temporal sequence of discrete spatial planning points (42); - Calculating a temporal sequence of a plurality of spatial intermediate points (46) between the planning points (42) by interpolation based on a mathematical function dependent on a scalar path parameter (u), whereby a value of the path parameter (u) is used to calculate the temporal sequence of the plurality of spatial intermediate points (46) between the planning points (42) are changed with a path parameter speed, which is a measure of the absolute change in the path parameter (u) per time increment; - Identifying an unforeseen, dynamic event that requires an adjustment of the temporal sequence of the plurality of spatial intermediate points (46) based on input information and calculating an adjustment amount corresponding to the adjustment based on the input information using predefined mathematical logic; - Changing the trajectory parameter speed in the event of identification of an unforeseen, dynamic event when calculating the temporal sequence of the plurality of spatial intermediate points (46) based on the calculated adjustment amount; and - controlling the machine part to move along the calculated temporal sequence of the plurality of spatial intermediate points (46). Computer program product that has software that is designed to execute the method according to when executed on a computer Claim 13 to carry out.

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