Choose the Right Block to Model Motors or Actuators

Simscape™ Electrical™ provides more than one block that can model the same type of motor or actuator. For example, you can use the Motor & Drive (System Level), PMSM, and FEM-Parameterized PMSM blocks to model a permanent magnet synchronous motor (PMSM). It is important to use a block that has sufficient modeling detail for the engineering design questions that you plan to answer using your model. It is also important not to use more detail than you need because this slows down simulation and makes the model more complex to parameterize. The right block to use therefore depends on the level of complexity that you need to meet your design goals. This guide shows you how to:

1. Determine the level of fidelity that you need.

2. Determine the motor characteristics that you need to represent in your model for your type of motor.

3. Select a block that can model a motor with those characteristics at that level of fidelity.

Determine Fidelity Level

Simscape Electrical supports different fidelity levels for modeling motors or actuators. You can define three levels of model fidelity. Each successive level requires increasing modeling complexity which restricts the design space that you can practically explore or optimize against. It is important to develop your model with the right level of complexity.

• Level 1 models use energy balancing or other modeling abstraction methods. With energy balancing, when the block operates as a motor, the electrical power in equates to the mechanical power out plus losses. When the block operates as generator, the mechanical power in equates to the electrical power out plus losses. You can obtain realistic motor drive losses from tabulated loss data from a Level 3 model using the generateMotorDriveROM function. For some actuation systems like piezoelectric travelling wave actuators, you can use a more abstract model that removes cyclic variables. For Level 1 modeling, you often need to draw the component modeling boundary around the drive electronics and the control as well as the motor so that you do not need to model high-frequency current modulation which requires a small simulation step size. Use Level 1 fidelity when you need a long simulation time, for example, to analyze drive cycles for electric vehicles.

• Level 2 models use fixed or parameter-dependent coefficients with a simple equivalent circuit. The fixed coefficients are usually fixed inductance values, for example, Ld and Lq when modeling a PMSM. In the case of a PMSM, the simple equivalent circuit corresponds to Ld, Lq, and the back EMF terms appearing in the Park’s transformed equations of the stator windings and rotor magnetic field terms. Use this level of fidelity to design controls or systems in actuation applications like robotics and mechatronics and for efficiency predictions when saturation and harmonics only weakly impact losses.

• Level 3 models define motor behavior in terms of flux linkage. You can parameterize the model using data from a motor design tool that uses finite element (FE) analysis to derive flux linkage as a function of the stator winding currents and rotor angle. You must also incorporate iron loss information from the FE tool to make good loss predictions at high motor speeds. Use this level of fidelity when you need a high level of modeling detail, for example, to predict efficiency for traction applications or to capture torque and electrical current harmonics.

Determine Characteristics to Model

Once you have determined the level of fidelity that you need, the next step is to determine the characteristics of your type of motor that you need to represent in your model. One important motor characteristic is synchronicity. A motor can be:

• Synchronous or no-slip – the rotor stays synchronized with the stator magnetic field.

• Asynchronous – the rotor is not synchronized with the stator magnetic field and slips.

Another important motor characteristic is the rotor type. The rotor types that you can model in Simscape Electrical are:

• Permanent magnet rotor — The rotor has permanent magnets that create its magnetic field.

• Wound rotor — Electromagnets that are powered via slip rings or a brushless exciter create the magnetic field.

• Permanent magnet and wound rotor — The rotor has permanent magnets that are augmented or modulated by an electromagnet powered via slip rings.

• Squirrel cage rotor — The rotor has the form of parallel bars which carry induced currents when cutting through the stator electromagnetic field.

You can define the flux distribution as:

• Sinusoidal — The flux distribution you can see at a stator winding from the rotating rotor has a sinusoidal form. This flux distribution means that the back EMF induced in each of the stator windings also has a sinusoidal form.

• Trapezoidal — The flux distribution you can see at a stator winding from the rotating rotor has a trapezoidal form. This flux distribution means that the back EMF induced in each of the stator windings is approximately constant allowing you to use simpler and cheaper control strategies.

Choose Right Block

These tables show the blocks that you can use to represent motors with different characteristics at each level of fidelity. The tables also show some common types of motor that have those characteristics. Use these tables to select the right block to model your motor or actuator.

Brushless Motors

Characteristics	Types of Motor	Blocks
		Level 1	Level 2	Level 3
Synchronous Permanent magnet rotor Sinusoidal Rotary	Interior permanent magnet (IPM) motor or Interior permanent magnet synchronous machine (IPMSM) Surface permanent magnet (SPM) motor or surface permanent magnet synchronous machine (SPMSM) Transverse flux motor Axial flux motor PMSM servomotor	Motor & Drive (System Level)	PMSM PMSM (Single-Phase) PMSM (Four-Phase) PMSM (Five-Phase) PMSM (Six-Phase) To build faulted motor models, you also need: Magnetic Rotor Rotating Air Gap For information about this workflow, see Faulted PMSM	FEM-Parameterized PMSM
Synchronous Permanent magnet rotor Trapezoidal Rotary	Brushless DC (BLDC) motor	Motor & Drive (System Level)	BLDC	FEM-Parameterized PMSM
Synchronous Permanent magnet rotor Sinusoidal Linear	Permanent magnet linear synchronous motor (PMLSM) Linear synchronous motor (LSM) Direct drive linear motor	Motor & Drive (System Level) plus Wheel and Axle	PMLSM	FEM-Parameterized PMSM plus Wheel and Axle
Synchronous Permanent magnet and wound rotor Sinusoidal Rotary	Hybrid PMSM	Motor & Drive (System Level)	Hybrid Excitation PMSM PMSM	FEM-Parameterized Synchronous Machine
Synchronous Wound rotor Sinusoidal Rotary	Switched reluctance motor (SRM) Synchronous motor Synchronous machine Synchronous generator	Motor & Drive (System Level)	Simplified Synchronous Machine Synchronous Reluctance Machine Switched Reluctance Machine Switched Reluctance Machine (Multi-Phase) Synchronous Machine Model 1.0 Synchronous Machine Model 2.1 Synchronous Machine Round Rotor Synchronous Machine Salient Pole Synchronous Machine (Six-Phase)	FEM-Parameterized Synchronous Machine (for three-phase motors only) FEM-Parameterized Rotary Actuator (for reluctance machines — For more information about this workflow, see Switched Reluctance Motor Parameterized with FEM Data)
Asynchronous Wound rotor Sinusoidal Rotary	Wound rotor induction motor Asynchronous motor	Motor & Drive (System Level) plus a torque controller Simplified Induction Motor with no torque or speed controller	Induction Machine Wound Rotor Induction Machine (Single-Phase)	FEM-Parameterized Induction Machine (Wound Rotor)
Asynchronous Squirrel cage rotor Sinusoidal Rotary	Squirrel cage induction motor Asynchronous motor	Motor & Drive (System Level) with a torque controller Simplified Induction Motor with no torque or speed controller	Induction Machine Squirrel Cage	FEM-Parameterized Induction Machine (Squirrel Cage)

Mechatronic Actuators

Characteristics	Types of Motor	Blocks
		Level 1	Level 2	Level 3
Rotary Stepping	Stepper motor Unipolar stepper motor	Stepper Motor with Simulation mode set to Averaged Unipolar Stepper Motor with Simulation mode set to Averaged	Stepper Motor Unipolar Stepper Motor	FEM-Parameterized Rotary Actuator (electromagnetic devices only)
Rotary limited travel Non-stepping	Torque motor Torque actuator	Generic Rotary Actuator	Not supported	Not supported
Rotary Non-stepping	Piezoelectric rotary motor Travelling wave motor	Piezo Rotary Actuator	Not supported	Not supported
Linear limited travel Non-stepping	Solenoid Piezo stack Piezo Bender	Generic Linear Actuator	Solenoid Piezo Stack Piezo Bender	FEM-Parameterized Linear Actuator (electromagnetic devices only)
Linear Non-stepping	Piezoelectric linear motor Travelling wave motor Piezo linear actuator	Piezo Linear Actuator	Not supported	Not supported

Brushed Motors

Characteristics	Types of Motor	Blocks
		Level 1	Level 2	Level 3
Permanent magnet DC supply	DC motor	Motor & Drive (System Level) plus a torque controller	DC Motor	Not supported
No magnet DC supply	Shunt motor Compound motor	Motor & Drive (System Level) plus a torque controller	Shunt Motor Compound Motor	Not supported
No magnet AC or DC supply	Universal motor Series wound motor	Motor & Drive (System Level) plus a torque controller	Universal Motor	Not supported
Permanent magnet DC supply Controlled	RC servomotor	Not supported	RC Servo	Not supported