Introduction

Stepper-Lab is a Scilab/Xcos model of a two-phase hybrid stepper motor with its power stage and current measurement. It lets you run the control code of Stepper-C against that model on a PC, drive it with any signal, and read the results, before the code reaches hardware.

What it does and does not do

It does	Why
Runs the real C code of Stepper-C inside an Xcos diagram (software in the loop, SIL)	The code under test is the code that ships: ADC counts in, PWM compare values out
Runs a Scilab prototype of the same controller in the same layout (model in the loop, MIL)	An algorithm can be changed and studied without compiling it
Accepts any Xcos source as motion command, run current or load torque	Step, sine, ramp and your own signals use the same three inputs
Models the power stage as averaged or switching, with results from ngspice	The fast model is enough for most runs; the slow one shows ripple and dead time
Checks itself: tests against theory, against a Python twin, and between MIL and SIL	Each model is checked by something other than itself

It does not	Why
Replace measurements on your motor	Back-EMF constant, friction and detent torque of the example motor are derived or assumed; Configuration marks which
Control a real motor	It is a simulation; the firmware that uses Stepper-C is a separate matter
Include Stepper-C	The library has its own repository; you select its folder
Run ngspice	The window only selects a stage file that sfs-stepper-power-spice has exported
Model temperature, saturation or the motor beyond its two-phase equations	The equations are in Motor and Control Model

Who it is for

Embedded and control engineers who work with stepper motors and want to see what a controller does before the first power-up. No Scilab knowledge is needed for the first runs: the Lab window holds the choices, and the scenarios are ready to run.

Related projects

Project	Role here
Stepper-C	The control library under test. Its sources are compiled into the SIL blocks
sfs-stepper-power-spice	ngspice models of the power stage. Its export is the stage file: leg resistance, diode voltage, effective dead time and the leg voltage error table

Rule of this project: the Scilab model follows the algorithm of the library. A change in Stepper-C is ported to the prototype and to the Python twin in the same step, and the tests show whether they still agree.

Key properties

Property	Value
Tool	Scilab 2027 with Xcos; a C compiler for the plant and the library
Example motor	17HS19-2004S1: 1.60 Ω, 3.0 mH, 2.0 A, 200 steps per revolution
Example board	B-G431B-ESC1: 24 V, 20 kHz PWM, three legs with a shared leg
Controllers	SIL (C, FIXED or FLOAT backend), MIL (Scilab)
Stepper-C version used for the results	main at commit 3ef0f7e, which reports itself as 1.1.0 and has stall detection fixes made after the tag v1.1.0
Tests	433 checks, 0 failures on the final full run (Verification)
Platform of all results	Windows 10 with Scilab 2027.0.0
License	Apache License 2.0

Terminology

Term	Meaning
SIL	Software in the loop: the compiled C library runs against the model
MIL	Model in the loop: the Scilab prototype of the controller runs against the same model
Plant	Power stage, motor and current measurement: everything the controller acts on
Prototype	The Scilab implementation of the controller (model/ctrl_period.sci and the functions it calls)
Python twin	Independent Python implementation of parts of the model, in tools/; it checks the Scilab results
Stage file	JSON export of sfs-stepper-power-spice with the measured values of a power stage
Scenario	A ready experiment of the window: context lines and source blocks
Backend	The numeric form of Stepper-C: FIXED (Q15) or FLOAT
Fast loop, slow loop	The two periods of Stepper-C: 20 kHz current control, 1 kHz motion
Load angle	Electrical angle between the commanded field and the rotor; beyond 90° the rotor is past its pull-out point

Conventions

• Units are SI unless stated. Positions are in microsteps, with 3200 microsteps per revolution at 16 microsteps per full step.
• Functions are written sil_report(), and files by their path from the repository root.
• The current vector is iA = I cos(phi), iB = I sin(phi), and the rotor settles at p theta = phi. Increasing phi turns the rotor forward. Stepper-C uses the same convention.