Motor sizing with NX MCD - cache.industry.siemens.com

Motor sizing with NX MCD

NX MCD v1872, SIZER v3.19, SIMOTION SCOUT v5.2

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Motor sizing with NX MCD Entry-ID: 109770271, V1.1, 02/2021 2

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Legal information Use of application examples

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Table of Contents


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Table of Contents Legal information ......................................................................................................... 2

1 Introduction ........................................................................................................ 4

1.1 Overview............................................................................................... 4 1.2 Limitation of the physics simulation with NX MCD ............................... 5 1.3 Software Versions ................................................................................ 5

2 Modeling of the digital twin in NX MCD ........................................................... 6

2.1 Import a Cam profile from SCOUT to NX MCD.................................... 6 2.2 Export Cam profile from MCD to SCOUT .......................................... 10 2.3 Set up a digital twin movement .......................................................... 11 2.4 Advanced settings .............................................................................. 13 2.4.1 Specific settings in MCD .................................................................... 13 2.4.2 Friction models and friction compensation in MCD ............................ 14

3 Transfer of physical simulation results......................................................... 18

3.1 Export a load curve from MCD ........................................................... 18 3.2 Import a load curve to SIZER ............................................................. 20 3.3 Selecting a motor in SIZER ................................................................ 22

4 Examples .......................................................................................................... 26

4.1 Example 1: Rotating Table ................................................................. 26 4.1.1 Comparison of MCD simulation result and measured values of

a real machine .................................................................................... 26 4.1.2 Comparison of MCD simulation result and SIZER result ................... 28 4.2 Example 2: Metal press ...................................................................... 33

5 Additional Information .................................................................................... 36

5.1 Reliability of simulated load curves .................................................... 36

6 Appendix .......................................................................................................... 37

6.1 Service and support ........................................................................... 37 6.2 Application support ............................................................................. 37 6.3 Links and literature ............................................................................. 37 6.4 Change documentation ...................................................................... 38

1 Introduction


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1 Introduction

1.1 Overview

In the process of developing a machine, motor selection is one required step. With NX MCD (Mechatronics Concept Designer), it is possible to do motor selection in collaboration with the software SIZER. Due to the kinematic design, including mechanics and physics simulation in MCD, it’s possible to export the simulation result to SIZER to do further selection. Motor sizing analysis of the virtual model can be performed using custom applications to ensure proper performance and reduce over-sizing. Limitations must be taken into account in order to obtain a realistic result.

Figure 1-1 The Process Motor Selection using MCD and SIZER

The application example contains an introduction about defining a kinematic movement in MCD (Open Kinematic Chain). The definition of a cam profile can be done in NX MCD standalone or in the engineering system, e.g. SIMOTION SCOUT. In this case it is possible to easily import the existing cam profile. It will also be explained how to build a friction model to have realistic results containing a dynamic friction. Furthermore, it is described how to analyze and export speed and torque profile to the software SIZER to do the motor selection. In the end of this document you can find a comparison between simulation and measured results of existing machines.

WARNING NX Mechatronics Concept Designer is based on a numeric calculation (Physics Engine).

It is not a multi-body-simulation with a dynamic motion analysis.

Nevertheless, under certain circumstances NX MCD can be used for exporting loadcurves. Chapter 1.2

1 Introduction


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1.2 Limitation of the physics simulation with NX MCD

The physics engine of NX MCD may not provide proper force and torque results under following conditions:

- Driven axes are part of a Parallel-Kinematic (e.g. Delta Robot Kinematic)

- Driven axes are part of a closed kinematic chain. Figure 1-2

- Collision between the driven axes or its kinematic chain and any other collision body

- Too high mass ratios between attachment and base of joints

Further restrictions:

- Currently, MCD cannot export inertia information. Because of this restriction, the external moment of inertia to motor moment of inertia ratio, cannot be calculated at the end phase of motor selection. It’s not possible to use this parameter to judge the system control stability.

- Within NX MCD, just a rigid body simulation is possible. Missing physics calculation for e.g. flexible bodies like plastic ribbons or cables may have a high influence on torque profiles. Caused by a rigid body simulation, also collisions can influence the torque simulation.

- Dynamic friction model must be modelled manually.

Figure 1-2 Closed -and Open Kinematic Chain

Closed Kinematic Chain Open Kinematic Chain

1.3 Software Versions

The following table lists the software versions used to create this application example.

Table 1-1 Software versions

Software package Version Article number

NX Mechatronics Concept Designer NX1872 NX11113

SIZER V 3.19

SIMOTION SCOUT V 5.2 6AU1810-1BA52-1XA0

2 Modeling of the digital twin in NX MCD


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2 Modeling of the digital twin in NX MCD To obtain the simulation results of a specific movement, including the speed and torque of an axis, it is necessary to define these movements in NX MCD. In this application example it will be explained how to create a movement based on a cam profile.

Cam profiles can be created in NX MCD standalone via cam profile editor or can be imported from an automation engineering system like SIMOTION SCOUT. The import and export functionality are working in both ways as shown in Figure 2-1.

Figure 2-1 Cam profile import and export

MCDSCOUT

Export

Import

Download

Motion ControllerMechanical Cam

2.1 Import a Cam profile from SCOUT to NX MCD

NOTE In order to import a cam profile from SCOUT in NX MCD, the cam profile must be interpolated.

1. Open a cam curve in SCOUT, then choose the option Cam → Export geometry → “As polynomials” to export cam profile, as shown in Figure 2-2.

2. Fill in a file name and format, then press the Save button as shown in Figure 2-3.



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Figure 2-2 Export Cam profile from Scout

Figure 2-3 Fill out the file name and format

After a successful export of the cam profile, it is necessary to import this cam profile to NX MCD.

1. Open the NX MCD project, go to Toolbar “Home - Design Collaboration” and select the Button ”Import Cam Profile” as shown in Figure 2-4. Cam profile is a physics object in NX MCD, which includes a cam curve and specific settings.

2. Click the browse button in Figure 2-4 and select the previously exported cam file (.csv). Add a cam profile name and click the button “OK”.

3. Configuration of a cam profile can be done as shown in Figure 2-5. In this dialog, it’s possible to define and change the information of a cam profile and the simulation preferences. In the Axes part, it’s needed to define the master and slave axis type, these settings must fit to the chosen project and cam profile. Axis type of master can be linear, rotary and time based. The slave axis



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can be a linear or rotary, speed or position. If it’s an imported cam profile, the minimum and maximum value can be filled in automatically. Otherwise, it’s possible to insert the limits manually, based on the information of the curve. Additionally, the cycle type must be selected correctly.

Explanation of cyclic types:

- “Non-cyclic”: Cam profile only cycles once. Only in this mode, it’s possible to export the cam profile from NX MCD.

- “Cyclic”: Cam profile cycles continuously, starting from the same absolute slave position.

- “Relative Cyclic”: Cam profile cycles continuously, starting relative to the end position of the slave’s previous cycle.

Figure 2-4 Import Cam profile in MCD



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Figure 2-5 Configuration of a cam profile



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2.2 Export Cam profile from MCD to SCOUT

In the case of exporting a Cam profile from MCD to SCOUT, it’s necessary to create a cam object in SCOUT in advanced. If a cam is created by “CamEdit”, it’s necessary to select type “Polynomials” to create a cam. If type “Interpolation point table” is chosen, there will be an error caused by incompatibility. After the preparation, choose SCOUT CamEdit in MCD and then export the cam profile. Figure 2-6

If it’s a cam profile created by “CamTool” in SCOUT, it’s necessary to select SCOUT CamTool in MCD cam profile dialog. Figure 2-7

Figure 2-6 Create a cam profile in SCOUT by using “CamEdit”

Figure 2-7 Create a cam profile in SCOUT by using “CamTool”



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2.3 Set up a digital twin movement

In NX MCD a physics object called “Position -or SpeedController” is needed to perform a movement, depending on the application. Via the cam profile dialog, it’s necessary to map a cam profile to the desired controller.

1. Click the extension button in Toolbar “Home - Mechanical” and select “Electronic Cam”. Figure 2-8

2. Select the axes master type in Figure 2-5. As a hint, the master type can also be axis or signal based. Afterwards select the physics object of the slave axis (speed or position controller). Figure 2-9

3. Choose the imported cam profile.

Explanation of additional settings:

- “Initial Time”: Sets the start point of the cam profile relative to the master axis. This is only available, if the Master Type is set to Time.

- “Slave Offset”: Sets velocity offset of the slave axis.

- “Slave Scale Factor”: Sets the dynamic scaling of the slave axis.

If the master type axis or signal has been chosen, there are more specific settings available.

- “Master Offset”: Sets the start point of the cam profile relative to the slave axis. This is only available, if the master type is set to axis.

- “Master Scale Factor”: Sets the dynamic scaling to the master axis. This is only available, if the master type is set to axis.

Figure 2-8 Create Electronic Cam



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Figure 2-9 Configurate Electronic Cam

NOTE Avoid over-determined definitions, like using two motors to drive one gantry. This might lead to unstable calculation results. Try to simplify the model, use one motor to drive one axis.



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2.4 Advanced settings

2.4.1 Specific settings in MCD

The physical calculation in MCD is based on a physics engine. If the complexity of a project increases, it could be necessary to limit the calculation accuracy. Figure 2-10

Explanation of MCD preferences – Physics engine tuning:

- Tolerance: Sets the distance between two objects and still be considered as aligned by a joint. A larger value is solved faster but results in more backlash in the joint positioning.

- Error Reduction Amount: Sets a factor that determines how fast joint positions are solved. A larger value causes the solver to pull joints together in fewer steps, but a value that is too high can cause instability.

- Maximum Iteration: Sets the maximum number of iterations per time step, which the solver uses to solve for the position of the joints and bring all their positions within the tolerance. A larger value gives the solver more time to bring a large number of joints into position, but it can potentially take longer to solve.

- Sticky Force: Sets a bonding force between collision bodies to counteract the repelling force caused by a collision.

The figure below shows the recommended parameters.

Figure 2-10 Parameter about Physics Engine

NOTE In order to make the digital twin closer to the real machine, it’s also very important to define the correct materials to each part. This is a basic function in NX, click “Menu”→ “Tools” → “Materials” to assign a material.



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2.4.2 Friction models and friction compensation in MCD

In theory, the usage of motor torque is divided into the following main parts:

- Acceleration: Considered/Calculated in MCD

- Overcoming gravity: Considered/Calculated in MCD

- Overcoming friction: Friction occurs in all mechanical systems e.g. bearings, transmissions, hydraulic and pneumatic cylinders. Friction exists at the physical connection between two surfaces. If a realistic behavior of friction is needed, a specific friction model is necessary. In this case choose a simple friction model to get an almost realistic calculation.

According to “Friction models and friction compensation1”, the following model was built and evaluated. The meaning of the variables used in the formula is shown in Figure 2-11.

𝐹 = {−𝐹_𝑐𝑜𝑢𝑙𝑜𝑚𝑏/𝑍𝑒𝑟𝑜𝑆𝑝𝑒𝑒𝑑 ∗ 𝑠𝑝𝑒𝑒𝑑 𝑠𝑝𝑒𝑒𝑑 < 𝑍𝑒𝑟𝑜𝑆𝑝𝑒𝑒𝑑 𝑠𝑝𝑒𝑒𝑑 > −𝑍𝑒𝑟𝑜𝑆𝑝𝑒𝑒𝑑−𝐹_𝑐𝑜𝑢𝑙𝑜𝑚𝑏 ∗ 𝑆𝑖𝑔𝑛(𝑠𝑝𝑒𝑒𝑑) − 𝛽 ∗ 𝑠𝑝𝑒𝑒𝑑 − 𝑍𝑒𝑟𝑜𝑆𝑝𝑒𝑒𝑑 ⩽ 𝑠𝑝𝑒𝑒𝑑 ⩽ 𝑍𝑒𝑟𝑜𝑠𝑝𝑒𝑒𝑑

NOTE In the design phase, it’s hard to evaluate the friction of a real machine. This example provides a simple friction model called “Coulomb and Viscous Friction” as shown in Figure 2-11. “ZeroSpeed” represents a very low speed close to the origin point. Within this interval from -ZeroSpeed to ZeroSpeed, the friction is continuously changing. If there is no such interval, the calculation of MCD’s physics engine would be unstable. As a hint: NX MCD is using the “Bullet” physics engine.

Figure 2-11 Coulomb and Viscous Friction model

(ZeroSpeed,F_coulomb)

The slope of the line is β

The next step is to implement the calculation of the physics objects in MCD. To do so, open physics object “Runtime Parameters” as shown in Figure 2-12, to create a reusable object that contains physics parameters. These parameters can be referenced by any physical object in a model. The physics object “Runtime Expression” defines an expression for a runtime parameter.

(Toolbar “Home – Mechanical”, Runtime Parameters / Runtime Expression)

1 Olsson H, Åström K J, De Wit C C, et al. Friction models and friction compensation[J]. Eur. J. Control, 1998, 4(3): 176-195



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Usage of “Runtime Expressions”:

- Create relationships between runtime parameters

- Use mechatronics simulation settings in functions

- Determine the minimum or maximum value from a group of values

- Scale values

- Determine output ranges

- Output a random number

1. Create one “Force/Torque Controller” and add specific friction to each joint if not negligible. In this example we focus on adding friction to the axis which was connected to a PositionController before.

2. Create one “Runtime Parameters” and add the parameters as shown in Figure 2-12. After selecting the parameter attributes, remember to click the green check button.

Figure 2-12 Configurate Runtime Parameters



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3. Create one “Runtime Expression”. Firstly, click “Select object” and choose the Force/Torque control added before.

4. Select the torque property to assign the calculation result to the torque value.

5. Select the physics object and add the needed parameters as shown in Figure 2-13, step 3 to 5. Via double click the step 6 area, it’s possible to change the alias name, which is used for the formula.

6. Click the step 7 button “Insert Conditional”. A conditional builder will be opened to fill in the formula. Figure 2-14

If: speed < ZeroSpeed & speed > -ZeroSpeed

Then: -F_coloumb/ZeroSpeed*speed

Else: -F_coloumb*Sign(speed)-ß*speed

Figure 2-13 Configure Runtime Expression



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Figure 2-14 Fill out the formular of the friction model

1

2

3

NOTE The damping parameters in Mechatronics Concept Designer Preferences – General, will also influence the torque result. If a special friction calculation is used, these damping parameters should be set to 0.

3 Transfer of physical simulation results


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3 Transfer of physical simulation results A drive system, which is correctly dimensioned, will properly work throughout its lifecycle. Taking all necessary factors into consideration, will help to secure trouble-free performance over the system’s design lifetime.

Within the last chapter, an establishment of a simulation model has been completed in NX MCD. This chapter explains, how to do the simulation in MCD. Also how to obtain a “.mdix” file, which contains the load cycle data, like speed and torque values. This “.mdix” file is needed for the SIZER export to do further motor selection. E.g. the configuration of the SINAMICS drives, motors, and controllers. Figure 3-1

Figure 3-1 Export load curve to SIZER

SIZER sizing motorMCD simulation

.mdix file

time

time

Torque

Velocity

3.1 Export a load curve from MCD

1. Open Toolbar “Home – Design Collaboration” the “Export Load Curve” dialog box and select the slave axis at “Axis Control”. Figure 3-2

2. Add the slave axis control to “output axis controls”.

3. In the “Record Load Curve” dialog box, it’s possible to define the trigger for the load curve. For the “Time” option, it’s needed to set the start and end time for data retrieval. For the “operation” option, it’s necessary to use the sequence editor to set the start and end point for data retrieval.

4. Start the simulation with „Play Simulation”.

5. Choose the presentation style of the simulation results.

- “Graph”: The speed and torque data would be displayed as curves in the following box.

- “Table”: More detailed information would be displayed in the following table, which includes “Time”,”Duration”,”Speed”,”Torque” etc..

6. Select a file location where the load curve should be exported, then click “OK”.

NOTE The column of “Inertia” is 0, currently NX MCD cannot calculate the inertia information.



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Figure 3-2 Configure Export Load Curve

NOTE In reality, there would be one or several gearboxes or synchronous belts after a motor shaft. It’s possible to define the gearbox ratios in MCD by using the physics object “Gear” or setting the gearbox ratios, when selecting motors in SIZER. When trying to simplify a digital twin, be careful with combining several speed reduction mechanisms. It may change the speed and torque of some parts and leads to a wrong simulation result. This also depends on the selected record point.



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3.2 Import a load curve to SIZER

During the last chapter, the final steps in NX MCD are done. The next step is to choose an drive system and motor in SIZER. A mechatronic project needs to be created, with this project type, motor configurations can be performed based on the imported mechatronics data. If a project still exists, it is possible to update the load data during further processing via an import. Menu → Project → Update of mechatronic data. Figure 3-3

1. Choose Mechatronic project option to create a project.

2. Fill out the project name and path.

3. Click on the “Browse” Button of “Mechatronic data import file” and select the export file of NX MCD.

4. Click the button “create project” to generate the project.

Figure 3-3 Create Mechatronic project in SIZER

A mechatronic project has been created. Afterwards it’s necessary to assign a temporary system to this project.

NOTE If the project type of Mechatronic project cannot be found in SIZER, one possible reason is that the user didn’t select the complete features when installing it.



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The following components are supported for the creation of a mechatronic project:

- Converter Systems

• SINAMICS S120 DC/AC multi-axis converter built-in units (with Basic Line Module, Smart Line Module or Active Line Module)

• SINAMICS S120 AC/AC single drive

- Motor Types (editable properties)

• 1PH8

• 1FT/1FK (with/without mounted gearbox)

1. If only one axis is contained in the transferred mechatronic data, it can be decided, whether a single-axis or a multi-axis drive system is to be created. The appropriate options are offered in SIZER. If several axes are contained, a multi-axis converter system is always created. Figure 3-4

2. The required type of the Line Module can be selected (BLM, SLM, ALM).

3. Select the motor type and its properties for each axis.

The linked mechanical system cannot be changed in a mechatronic project.

Figure 3-4 Select motor type



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3.3 Selecting a motor in SIZER

The mechatronic project must be converted to a SIZER project to continue selecting a motor. Menu → Project → Convert to a SIZER project. Figure 3-5

Afterwards, the workflow for processing or completing the drive system is provided. All components can be modified, including the load data. A SIZER project contains the functionality of updating and exporting mechatronic data, too.

Figure 3-5 Convert to a SIZER project

There are different ways of choosing a motor, according to the actual requirement as shown in Figure 3-6. The specification of the mechanical system, required for the complete description of a drive, can be facilitated by using pre-configured mechanical systems. For the first example machine, in order to analyze the torque demand of a slip ring, select a motor of type “1FW”.



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Figure 3-6 Reselect the motor type



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Figure 3-7 shows the load cycle curve, which is calculated from the transfered data, including the speed and torque values of the motor shaft. All mechanical variables, in accordance with the mechanical entries are included in the calculated torques. In the following dialog box, it’s possible to select basic type specifications, such as cooling methods, winding systems and clamping elements. With the button “Check all” a suitable motor can be selected, automatically.

Figure 3-7 Load data has been imported to SIZER

In Figure 3-8, the following data of the selected motor can be checked:

- The result of the dimensioning criteria

- The most important calculated load data

- The actual utilization of the motor

- The graph display of the load and motor characteristics

The system checks, whether the selected motor satisfies the required dimensioning criteria, which is indicated by a green check mark. If the motor does not satisfy the dimensioning criteria, a red cross is displayed.



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Figure 3-8 Motor check

4 Examples


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4 Examples

4.1 Example 1: Rotating Table

4.1.1 Comparison of MCD simulation result and measured values of a real machine

This example shows a rotary table machine for testing different slip rings Figure 4-1. It’s a quite simple model. All components of the moving part are connected with a fixed joint to each other. So the inertia of the machine is constant. The motor installed in this machine is the selected one of the previous step (1FW3150…). Figure 3-8

Figure 4-1 A rotation machine for testing slip ring

The simplified model of this machine is shown in Figure 4-2. Since there are many components in the model, each component is composed of multiple materials, it is difficult to obtain theoretical inertia information. If the inertia calculation is not performed by any software but manually calculated, the moment of inertia is first calculated according to the following formula. Afterwards it will be multiplied by the required angular acceleration to obtain the required torque.

4 Examples


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Figure 4-2 A simplified model and the moment of inertia calculation formula2

𝐹 = ( 𝑚 ) = ( 𝑚)𝑟

= 𝑟 𝐹 = ( 𝑚 ) 𝑟

= 𝑟 = ( 𝑚 )𝑟

= = ( 𝑚 ) 𝑟 = ( 𝑚 ) 𝑟

𝑜𝑚𝑒𝑛 𝑜 𝑖𝑛𝑒𝑟 𝑖 = 𝑚 𝑟

𝑜 𝑖𝑜𝑛 𝑙 𝑚𝑜𝑚𝑒𝑛 =

O

Z

𝑟 𝑚

𝐹

ω

The motion of the device moves according to the cam curves in Figure 4-3. In the point of position 1, the cam velocity is 0, but the acceleration is in minimum value as position 2. When the direction of the speed changes, the theoretical applied moment is continuous. The purpose of this design is that it’s obviously able to observe the friction influence at this point.

There are three curves in Figure 4-4:

- The torque traced from the real machine (blue)

- The simulation torque with friction (red)

- The simulation torque without friction (green)

The range of the measured torque values is from -23.7 Nm to 17.0 Nm. There are several steps in the curve which are caused by friction. At each step, the friction direction changes.

The maximum value of the simulation torque curve with friction is 16.9 Nm and the minimum value is -21.6Nm. The simulation torque value is less than the measured one.

Comparing the two curves with the MCD curve without friction reveals, that friction plays a crucial role and partially absorbs the motor torque.

2 Rotational Mechanics & Special Relativity - lectures from University of Cambridge

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Figure 4-3 Cam curve for slip ring

1

2

Cam Position

Cam Velocity

Cam Acceleration

Cam Jerk

Figure 4-4 Comparison of measured and simulation torque

Measured torque

4.1.2 Comparison of MCD simulation result and SIZER result

When using SIZER to perfom motor selection, the first step is to select a mechanical system. After that a traversing profile must be defined. In the selection mechanical system phase, it’s necessary to define efficiency, friction torque, the additional moment of inertia in relation to the motor (e.g. clutch) and moment of inertia of the mechanical system(load). In the phase of defining a traversing profile, if “Other mechanical system” is chosen, a free traversing profile curve will be generated from the entered values, which after the complete input of traversing sections, is displayed as M-t and n-t diagram.

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If the model system in SIZER is chosen, such as “Travel drive”, “Hoist drive” or others, it’s possible to define a traversing profile by using one of the following options in SIZER:

- Time optimization: Time is the value to be determined

- Variants of distance optimization: Distance is the value to be determined

- Optimizations based on dividing the total travel time into three on the sections of the trapezoidal (acceleration, constant velocity, deceleration)

Movement profiles can be defined directly in SIZER. Figure 4-5

It’s more common to use triangular acceleration and it is not possible to use a user-defined CAM profile.

Figure 4-5 Edit the movement profiles in SIZER

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In the Load cycle data dialog, a torque curve is displayed. Fehler! Ungültiger Eigenverweis auf Textmarke.

It’s visible, that there are several jumps as well, which are also caused by friction. The friction calculation in SIZER is based on a constant value, which is effective opposite to the direction of motion, independent of the angle of inclination.

Figure 4-6 Select motor in SIZER

12

After the previous steps, the load curve is visualized in SIZER.

The next step is to define the movement in NX MCD to receive the simulation result. This basic motion profile can be defined via the physics object “Position Control”.

1. Open the physics object “Position Control” and select the type of “Angular Path Options”.

The following types are possible:

- “Track Multiple Turns”

- “Follow Shortest Path”

- “Rotate Clockwise”

- “Rotate Counter-clockwise”

In this example the type “Track Multiple Turns” must be chosen. This specifies the direction of the movement. The position value of the physics object can be used as single coil absolute value encoder. When choosing “Track Multiple Turns”, the position value could be used as multi-loop absolute value.

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2. Insert the values for parameters of destination, speed and acceleration. MCD would calculate the movement profile automatically as shown in Figure 4-7.

Figure 4-7 Basic movement profile in MCD

After defining an equal motion profile in MCD, the simulation must be started to receive the calculated load curve. Afterwards the torque curve calculated in SIZER, the torque curve generated in MCD simulation and the actual curve traced from the real machine are copied into one graph for comparison as shown in Figure 4-8. The torque of the real machine is higher than the simulated torque of MCD and the calculated one of SIZER. It’s also clearly visible, that the simulated torque curve is

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more approximated to the torque curve of the real machine. The comparison indicates also that the slope, while the acceleration phase, is consistent. The curves calculated in MCD and SIZER are always composed of straight lines, which means the calculation result is ideal.

Figure 4-8 Comparison of measured and simulation torque

Measured torque

This example was investigated using the following application data:

Table 4-1 the attached file description

File name Description

1. !MACHINE.prt MCD project of rotating table

2. Cam_1.csv Export from SCOUT, which can be imported to MCD

3. LoadCurve.mdix Generated in MCD, which can be imported to SIZER

4. MechatronicProject.szn Mechatronic project in SIZER, which can be converted to a normal SIZER project

5. SizerProject_1.szp Chapter 3.3

6. SizerProject_TriangleAcc.szp Chapter 4.1.2

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4.2 Example 2: Metal press

This example shows a servo press, which is an ideal application because it requires a variable slide velocity at multiple points in the stroke profile. It’s a machine for metal forming, shallow to medium drawing and forming. Normally a servo press is driven by a servo motor, as opposed to a standard flywheel, including clutch and brake. This provides full energy at any speed, but not full capacity at any stage in the stroke (capacity is best at near bottom center).

The machine is a combination of servo press and flywheel press. It is using a servo motor to drive a small pulley, which drives through a timing belt a large pulley. The large pulley is connected to the rod by a clutch. Because of this connection the ram moves up and down. Figure 4-9 describes the components of the servo press.

Figure 4-9 components of the servo press

1

23

4

1

2

3

4

Small pulley

Large pulley

Rod

Ram

In this example, according to different cam curves, the machine is projected to drive in two different modes depending to process requirements:

- Mode 1: The speed is constantly changing, performed by an acceleration motion. Figure 4-10

- Mode 2: The speed remains constant in some phases. Figure 4-12

The jerk values in the two CAM curves are bounded, thus ensuring continuous movement and reducing the impact.

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Figure 4-10 Cam curve for mode 1

Cam position

Cam velocity

Cam acceleration

Cam jerk

Figure 4-11 The comparison of real data and the simulation data for mode 1

Measured torque

Measured speed

Figure 4-12 Cam curve for mode 2

Cam position

Cam velocity

Cam acceleration

Cam jerk

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Figure 4-13 The comparison of real data and the simulation data for mode 2

The comparisons of the simulated and real curves are shown for mode 1 in Figure 4-11 and for mode 2 in Figure 4-13. These two comparisons of curves are nearly equal. In both figures, precisely in the lower speed part, the dynamic friction is relatively low. If the speed increases, a gap will be visible as shown in Figure 4-132. Therefore, it is proved that using MCD for torque calculation and do motor sizing is reliable.

However, the difference between the measured torque curve and the simulation one, including the dynamic friction calculation, the torque curve is not constant.

The possible reasons are the changes of inertia in motion leads to the change of torque and the friction modifies with the change of speed.

5 Additional Information


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5 Additional Information

5.1 Reliability of simulated load curves

There is a 5% to 10% difference between theory and practice.

Possible reasons:

1. The friction model is not accurate. The actual friction exists on almost all contact surfaces, so it’s difficult to develop a friction model to constitute the real friction.

2. Caused by e.g. assembly errors, usage of different materials or simplified mechanical components like gears, the inertia information of the 3D model and the real device can be inaccurate.

3. The measured torque on a real machine is calculated based on the current. Because of this, the simulated torque cannot be exactly reflected.

The illustration below shows the negative direction friction and positive direction friction traced from the real machine. Figure 5-1

Comparing these two curves, no regularities can be seen.

If needed, special friction coefficients can be added manually from e.g.:

- Mechanical design manual

- Bearing manual

- Motor manual

- Empirical values of previously used devices

Figure 5-1 The actual friction curve in negative and positive direction

6 Appendix


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6 Appendix

6.1 Service and support

Industry Online Support

Do you have any questions or need assistance?

Siemens Industry Online Support offers round the clock access to our entire service and support know-how and portfolio.

The Industry Online Support is the central address for information about our products, solutions and services.

Product information, manuals, downloads, FAQs, application examples and videos – all information is accessible with just a few mouse clicks: https://support.industry.siemens.com/

Technical Support

The Technical Support of Siemens Industry provides you fast and competent support regarding all technical queries with numerous tailor-made offers – ranging from basic support to individual support contracts. Please send queries to Technical Support via Web form: https://www.siemens.com/industry/supportrequest

6.2 Application support

Siemens AG Digital Factory Division Factory Automation Production Machines DF FA PMA APC Frauenauracher Str. 80 91056 Erlangen, Germany

mailto: [email protected]

6.3 Links and literature

Table 6-1

No. Topic

\1\ Siemens Industry Online Support

https://support.industry.siemens.com

\2\ Link to this entry page of this application example


\3\ Sizer for Siemens Drives

https://support.industry.siemens.com/cs/document/54992004/

\4\ Link to online help of NX

https://docs.plm.automation.siemens.com/tdoc/nx/1872/nx_help/#uid:index


https://www.siemens.com/industry/supportrequest

mailto:[email protected]



https://support.industry.siemens.com/cs/document/54992004/

https://docs.plm.automation.siemens.com/tdoc/nx/1872/nx_help/#uid:index

6 Appendix


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6.4 Change documentation

Table 6-2

Version Date Modifications

V1.0 08/2019 First version

V1.1 02/2021 New restrictions

Motor sizing with NX MCD - cache.industry.siemens.com

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