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Validate System

This section explains how to evaluate the accuracy of the plant (motor and inverter) model of the physical motor and load connected to the motor. You should validate the plant model and verify that the results are close to the physical system measurements before using the plant model for implementing advanced algorithms. You can validate the system by comparing the step response of speed control and current control in simulation and in target hardware connected to the motor.

Use the example Tune Control Parameter Gains in Hardware and Validate Plant to measure the step response of the current and speed controllers. The host model in this example communicates the current reference to the target hardware and measures the step response of the current controller.

  • You can use any speed control example from Motor Control Blockset™ to validate the system.

  • Validate speed control by comparing the step response in simulation and the hardware test values.

  • Validate the d-axis current control by electrically or mechanically locking the rotor and comparing the step response in simulation and the hardware test results.

    You can use another method to validate the d-axis current control. Run the motor at a constant speed and provide a step change in the reference d-axis current. This requires two modifications in the speed control subsystem of the target model. Set a constant speed reference input. Command Id reference from the host model. Compare the step response of the d-axis current in simulation and in the hardware tests.

  • Validate the q-axis current control by mechanically coupling the motor with an external dynamometer running in speed control. This requires two modifications in the speed control subsystem of the target model. Discard the Id and Iq reference from the speed PI controller output. Command Id reference from the host model. Compare the step response of the q-axis current in simulation and in the hardware tests.

Warning

When capturing the step response in d-axis current control, always use a positive step. Negative values of Id can damage the permanent magnet in the PMSM.

See the example Tune Control Parameter Gains in Hardware and Validate Plant to deploy the model to the hardware. Perform motor parameter estimation because accuracy in the plant model is important so as to match the simulation results with the hardware measurements.

Calculate Physical Motor Load in Target Hardware

Before comparing the controller responses in simulation and in the target hardware, the load torque in plant simulation must match the motor load in the physical system. Follow these steps to calculate the load torque in the physical system and update the calculated load torque in the plant model.

  1. Run the host model and connect the target hardware through serial communication.

  2. In Select Motor operating mode, select Speed control.

    The motor spins in speed control.

  3. Select Id_meas in Monitor Signal #1 and Iq_meas in Monitor signal #2. Read the Id_meas and Iq_meas values from the scope.

  4. Convert the per-unit (PU) current to Amperes by multiplying it with PU_System.I_base.

  5. Calculate the load torque in Nm using this equation:

    Tload=1.5×pole_pair×[(flux_pmIq)+(LdLq)IdIq]

    where,

    flux_pm = Permanment magnet flux linkage (pmsm.Flux_PM)

    Ld, Lq = Inductance in Henry (pmsm.Ld, pmsm.Lq)

    Id, Iq = Current measured in Amperes

    Id_meas, the measured Id current (in PU), equals 0.

  6. In the mcb_pmsm_operating_mode_f28379d/Motor and Inverter/Plant Model (sim) sub system, provide the calculated load torque value as an input to the LdTrq port of the PMSM motor block.

Compare Speed Controller Response in Simulation and in Target Hardware

In simulation, provide a speed step input and note the speed response. On the target hardware, command the speed reference step input and observe the speed feedback. Compare the resulting step response in simulation and in target hardware to determine accuracy of the plant model.

  1. Simulate the model mcb_pmsm_operating_mode_f28379d. Plot the reference speed and measured speed signals. By default, this example provides a step input of 0.2 to 0.5 to the simulation model.

  2. Run the host model to communicate with the target hardware.

  3. In Select Motor operating mode, change the mode from Stop to Speed control.

  4. In the host model, select Speed_ref in Monitor Signal#1 and Speed_meas in Monitor Signal#2.

  5. Open the scope in the host model.

  6. In host model interface, change the speed_ref from 0.2 to 0.5 and observe the step change in the scope.

  7. Compare the step response of the hardware results with the simulation results.

Step Response Analysis for Speed Controller

Compare the step response obtained from simulation with the measurements obtained from the target hardware. The results may vary depending on the tolerances in the plant model. Generally, simulation results are close to the values measured on the target hardware.

 Peak overshoot (%)Peak time (ms)Rise time (ms)Settling time (ms)
Simulation results20.13%16.0235.56161.027
Hardware results22 %14.3245.04151.148

Compare Current Controller Response in Simulation and in Target Hardware

In simulation, provide a step current reference and note the current response. This example needs some changes to simulate the current reference step input. See these steps for the model changes. This applies only to simulation. In the target hardware, command the current reference step input and observe the current feedback. Compare the resulting step response in simulation and in the target hardware to determine the accuracy of the plant model.

  1. For hardware measurements, run the host model.

  2. In Select Motor operating mode, change the mode from Stop to Torque control.

  3. Select Id_ref in Monitor Signal#1 and Id_meas in Monitor Signal#2 in the host model.

  4. Open the scope in the host model.

  5. Change Id_ref from 0.02 to 0.22 and observe the step change in the scope. Ensure that the motor is not running. The scope displays the step response for the Id_ref input.

  6. For simulation, two changes are needed in the simulation model. In the mcb_pmsm_operating_mode_f28379d/TorqueControl/Control Modes/torque_control subsystem add a step input for the d-axis current controller. Choose a step input of 0.02 to 0.22 at 1 second. Select Time sample as -1. In the data-type conversion block, select the output datatype as fixdt(1,32,17).

  7. In the PMSM motor block available in the mcb_pmsm_operating_mode_f28379d/Motor and Inverter/Plant Model (sim) subsystem, change the Mechanical Input Configuration to Speed and input 0 to the Spd input port.

  8. Run the simulation and measure the Idref_PU and Idmeas_PU values in the simulation Data Inspector.

  9. Compare the step response in the hardware with the simulation results.

Step Response Analysis for d-axis Current Controller

Compare the scope image from simulation with the measurements from the target hardware. The results may vary depending on the tolerances in the plant model. With an accurate plant model, the simulation results are closer to the measured results from the target hardware.

 Peak overshoot (%)Peak time (µs)Rise time (µs)Settling time (µs)
Simulation results14 %300150500
Hardware results8.18 %400150800

The accuracy of the plant model improves the accuracy of simulation and matches the test hardware results.

Tip

If the simulation results differ considerably from the hardware measurements, verify the delay and scaling factor in the plant model.

Note

For the q-axis current controller, align the motor to the d-axis and mechanically lock the rotor. Follow this for the d-axis current controller for comparative analysis. You can achieve external mechanical locking through the mechanical braking system or by coupling with a dynamometer motor running in speed control.