Week 04
Speed Loops
I use my PSIM report and PI calculation file to revisit the DC-motor model, cascaded current-speed loops, and field weakening.
What I connect in this unit
Assuming the current loop produces torque quickly, the speed-loop mechanical plant reduces to inertia and friction. Speed-feedback error creates a torque command, load torque enters as a disturbance, and response time depends on the mechanical time constant and outer-loop bandwidth.
Concept map
- Mechanical plant
- Speed feedback
- Load torque
- Response time
Technical anchor
Torque-to-speed dynamics are G_omega(s) = 1/(J s + B), with tau_m = J/B, so the crossover must be slower than the current loop to preserve the cascade assumption.
How I review it
Sketch expected waveforms for a speed-reference step and a load-torque step separately, then inspect acceleration slope during current limiting and response time after the limit clears.
Connection to the full course
Unit 4 of 12. Unit numbers follow the control structure in the saved design files and do not claim attendance weeks.