Mechatronics | PartQuest™ Explore

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC (First Robotics Competition) CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

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Copy of PID Speed Control Loop - Switching - on Tue, 08/04/2020 - 15:40

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Description

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC (First Robotics Competition) CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

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Copy of robot servo motor control - on Sat, 08/01/2020 - 16:39

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Copy of Automotive Electrical Power Distribution System - on Sat, 08/01/2020 - 09:35

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Copy of Loudspeaker with Simple Amplifier - on Thu, 07/30/2020 - 14:49

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This "Live" example design includes a simple analog electronic amplifier, intended only to demonstrates the importance of multi-discipline system modeling.

A swept frequency response test, from 40 Hz to 1000 Hz, shows the effect of the complex amplifier loading by the voice-coil and speaker-cone dynamics*. The electro-mechanical resonances strongly affect the current that must be supplied, in order to maintain a flat (controlled) output voltage over the specified frequency range. For example, the current in the voice-coil reaches a null at time 0.1 seconds, which corresponds to the effective "spring-mass" resonance frequency (60 Hz). The loudspeaker reaches its minimum impedance around 600 Hz, or at 0.6 seconds where the peak load current is observed.

The simulation results also show that the average power (q1/npn/pwr_avg) in the BDP947 BJT exceeds its 5 Watt rating across the entire range, but especially at lower frequencies. The red "hot part monitor", with the junction to ambient thermal resistance set to 10 C/Watt, as given in the datasheet, shows the part temperature rising to over 100 C. These diagnostic indicators make it obvious that we need a bigger transistor!

All of the parameters in blue can be changed by the user and a new simulation run. The updated scope waveform results will show the effect of that change. You can change the electrical resistance and inductance of the voice-coil, as well as the speaker cone mass and linear spring rate that affect the resonance frequency.

* Note: Please refer to this companion example, that shows the input impedance frequency response of the loudspeaker alone:

https://www.systemvision.com/design/loudspeaker-only-frequency-response

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Copy of Loudspeaker with Simple Amplifier - on Tue, 07/28/2020 - 16:30

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Description

This simple* analog electronic amplifier design demonstrates the importance of multi-discipline system modeling. A swept frequency response test, from 40 Hz to 1000 Hz, shows the complex amplifier loading effect of the voice-coil and speaker-cone dynamics. The electro-mechanical resonances strongly affect the current that must be supplied, in order to maintain a flat (controlled) output voltage over the specified frequency range. For example, the current in the voice-coil reaches a null at time 0.1 seconds, which corresponds to the effective "spring-mass" resonance frequency. The loudspeaker reaches its minimum impedance around 600 Hz, or near 0.6 seconds, where the peak load current is observed.

Normalized component stress monitoring signals are provided in all “datasheet specified” electronics models. For example, the simulation results show that the average power (bjt1/pwr_avg) in the BDP947 NPN BJT exceeds its 5 Watt rating across the entire range, but especially at lower frequencies. The corresponding stress monitor (bjt1/stress_ratio_power_avg) normalizes the transistor's average power relative to its 5W rating, so it is easy to see that the component is stressed (i.e. stress_ratio_power_avg &gt; 1.0). Also, the red "hot part monitor", with the junction to solder-point thermal resistance set to 10 C/Watt as given in the datasheet, shows the part temperature rising to well over 100 C. These diagnostic indicators make it obvious that we need a bigger transistor!

*Note: This is not intended to be a practical amplifier design. There is no blocking capacitor at the output, so it allows undesirable DC current into the voice coil. The purpose is to focus attention on the dynamic characteristics of the loudspeaker and not the circuit itself.

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Copy of PID Speed Control Loop - Switching - on Tue, 07/28/2020 - 14:20

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Description

This example shows a more detailed circuit- and logic-level implementation of the PID Control Loop shown in the companion example, “PID Speed Control Loop – Continuous”. The ideal motor drive block of the “Continuous” version is expanded here, to include both a H-bridge motor drive, and also the digital logic necessary for converting the continuous PID controller output into the desired PWM signals that are distributed to drive the gates of the power MOSFET switches. The MOSFET model was calibrated to represent an IRF3710, using only information published on the manufacturer’s datasheet.

The rest of the system, including the PID block-diagram controller, the mechanical fan load and the DC Motor characterized to represent an FRC (First Robotics Competition) CIM Motor, are the same as in the Continuous version. While the simulation time for this switching version is significantly longer, more detailed information about practical circuit performance and component sizing is available. For example, the fan speed step response is somewhat different from the conceptual design, because of the losses in the MOSFETs under high current conditions, as well as voltage drop in the battery. Also, information regarding component stress levels within the “datasheet specified” MOSFETs and Diodes is provided.

About text formats

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