Modeling of a bulk mixer using Altair EDEM, MotionSolve, PSIM and Activate

Mixing of bulk materials is often used in many industries. The use of continuous mixing is more popular than discrete mixing due to its high efficiency. Ensuring reliable operation of continuous mixing equipment for bulk materials is a key and important factor. However, the complex dynamic load on the electric drive of the mixer and ensuring uninterrupted operation for a long period of time is quite a laborious task. The traditional design approach, which relies heavily on physical prototyping, is time-consuming and expensive. Virtual prototyping using a digital twin allows engineers to develop products at a higher speed and with less effort.

The digital twin of the mixing equipment for mixing bulk materials consists of an electric drive and a bulk material that can be designed and modeled using software solutions Altair EDEM (more details), Altair MotionSolve (more details), Altair PSIM (more details) and Altair Activate (more details), as shown in Figure 1.

Fig.1. Modeling of the digital twin of a bulk mixer using Altair EDEM, Altair Motion Solve, Altair PSIM and Altair Activate solutions

In this example, we will use:

Altair EDEM (more details) to simulate the complex dynamic behavior of bulk materials.
Altair MotionSolve (more details) to build a dynamic model of the mixer shaft, including the inertia of the mixer shaft.
Altair PSIM (more details) for modeling a power electronics system, including a motor, inverter, control circuit and other electrical components.
Altair Activate (more details) to organize and connect all modeling tools together.

The digital double allows you to evaluate the complex behavior of the system resulting from the interaction of the electric drive and the forces created by the particles of bulk material on the shaft, as shown in Figure 2.

Fig.2. A graph showing the dynamic load on the mixer shaft, the motor torque and the shaft rotation frequency

The setup of the simulation process consists of five different parts:

3D modeling of geometry.
Modeling of bulk material in Altair EDEM (more details).
Creating a multibody dynamic model of the mixer shaft using Altair MotionSolve (more details).
Simulation of power electronics using Altair PSIM (more details).
Combining all modeling tools in Altair Activate (more details).

1. CAD modeling
Use Altair CAD tools: Altair Inspire (more details) (or Altair Inspire Studio) to create a 3D model of the mixer shaft and housing (Fig. 3). Save each part as a *.STL file.

Fig.3. CAD model of the mixer shaft and housing in Altair Inspire

2. Modeling in Altair EDEM
To simulate the process of mixing bulk materials using Altair EDEM:

Import the CAD geometry of the mixer body into Altair EDEM and set the material properties.
In the Simulator tab, select Geometries > Add Geometry > Cylinder as shown in Figure 4.

Fig.4. Technical characteristics of the geometry of the mixing chamber in Altair EDEM

Use the powder database to configure the bulk materials to be processed in a continuous mixer. In this guide, we will define only one type of material.
Create a copy of the cylinder geometry with closed ends, do not forget to assign it a virtual type and add factory. Right-click on factory, select change factory type to change it to static factory (static production) (Fig. 5).

Fig.5. Setting up the particle generator in Altair EDEM

3. Modeling in MotionSolve
In MotionView (MotionSolve preprocessor), go through the following steps for a multibody mixer model:

Specify the variable values of the applied torque, as well as the shaft rotation speed (Fig. 6)

Fig. 6. Setting solver variables in Altair MotionSolve

Extract the rotation frequency of the mixer shaft by defining its expression as `WX({sys_Generic Continuous Mixer.Part_1.cm.idstring})`. This will be included in the PSM model.
Import the geometry of the mixer shaft and configure the rotary connection (in the Add > Constraint section Restriction)) (fig. 7).

Fig. 7. Setting up the kinematic model in Altair MotionSolve

Assign the torque coming from the PSIM model to the shaft by assigning the Torque_out value to Tx (in the Add > Force Entity section) using sv_3.VARVAL() (Fig. 8).

Group the torque and speed into Control Input and SystemOutput, respectively. They will be used as input and output connections in Altair Activate (more details).
Create an EDEM assembly in the Assembly tab (Fig. 9).

Fig.9 Creating an EDEM assembly in Altair MotionView

Import the geometry of the mixer shaft into EDEM via MotionView by enabling the interface server (Fig. 10).

Fig. 10 Connecting a server for joint modeling of Altair EDEM and Altair MotionSolve

4. Modeling in PSIM
To simulate the power electronics assembly and control the speed of rotation of the mixer shaft:

Add the PCI motor controller, electric motor, inverter and other components (Fig. 11)

Fig. 11. Mixer motor control in Altair PSIM

4. Modeling in Activate

Add the PSIM and MotionSolve blocks in the Palettes > Activate > section Co Simulation and select the appropriate input files (Fig. 12).

Fig. 12. Setting simulation parameters in Altair PSIM and Altair MotionSolve in Altair Activate

Create a target speed block and connect it to the rpm_ref input for PSIM, then connect the MotionSolve output to the remaining input (shaft_speed_in) of the PSIM block (Fig. 13)

Fig. 13. Joint modeling of Altair PSIM, Altari MotionSolve in Altair Activate

To run the simulation:

Turn on the pairing mode in EDEM (Fig. 9).
Set the total simulation time in the Simulation Setup section in Activate and press the Start button (Fig. 14)

Setting the simulation time in Altair Activate

The comparison of time steps in EDEM - MotionView - Activate - PSIM will provide modeling with high accuracy, the disadvantage of this method is an increase in processing time. To speed up the modeling process, we can increase the time step, but this may affect the results. Table 1 shows the time step settings for all tools.

Table No. 1. Setting up a time step in Altair Activate, Altair EDEM, Altair MotionSolve

Table No. 1. Setting up the time step in Altair PSIM

Conclusions:
The digital twin of the mixer for bulk materials, including the geometry of the mixer, an electric drive and a device for bulk materials, can be created by combining Altair EDEM (more details), Altair MotionSolve (more details), Altair PSIM (more details) and Altair Activate (more details). The digital twin allows you to quickly create virtual prototypes of structures, reducing time and costs.

For the provision of temporary licenses for Altair EDEM (more details), Altair MotionSolve (more details), Altair PSIM (more details) and Altair Activate (more details), testing and purchase, please contact the specialists of NanoTechProm LLP by phone +7(777) 797-89-75, or by e-mail info@nanotechprom.kz.

NanoTechProm LLP is the official distributor of ALTAIR in Kazakhstan and the Central Asia.