Datum Sim 0.1.4

Discrete control: controllers that run at a sample time, as in a microcontroller, and more motor and drive blocks.

Discrete control

• Discrete transfer function and discrete state space.
• Discrete integrator (forward Euler, backward Euler or trapezoidal) with limits and a reset input.
• Discrete PID with a filtered derivative, output limits and anti-windup (clamping or back-calculation).
• Rate transition, to pass a signal between sample times (hold, or a one-sample delay).
• Sample-time colours (View › Sample-time colours): every block is coloured by how often its output changes, with a legend: continuous, each sample time, constant, or several rates.

Blocks

• A reset input on the Integrator (rising, falling or either edge), located exactly.
• Goto and From: send a signal by name without a wire, within one diagram or across the whole model.
• Sources: square wave, triangle wave, chirp (frequency sweep), repeating sequence.
• Terminator, to end an output you do not need.

Motors and drives

• Switched reluctance motor (6/4, 12/8 …) with an asymmetric bridge, and typical ratings.
• DC link (with a diode rectifier that only charges it), inverter DC current, and a current sensor with gain, offset, bandwidth and noise.

Worked examples: a digital PMSM drive (10 kHz current loop, 1 kHz speed loop) whose DC link rises while the motor brakes; a DC motor with a digital and a continuous PID side by side; switched reluctance motor speed control.

Checked: the discrete blocks against their difference equations; power balance for the induction, synchronous, DC and BLDC machines; the switched reluctance motor's torque and energy balance. See the verification record.

Fixed

• A signal resting at exactly zero (such as a reset input between pulses) could make the variable-step solvers take endless tiny steps.