MakerBotControlSystem

From Clothbot

Jump to: navigation, search

Contents

MakerBot: Control System Design, Implementation and Characterization

Time to brush off some of that rusty old control system design knowledge I once majored in.

Goals

My goals will be to:

  • Describe the MakerBot thermal, electrical and mechanical system in terms of a state-space model.
  • Model said system using the GNU Octave free open-source software (FOSS) suite of tools.
  • Design test and measurement criteria and data to generate a set of parameter estimation functions to calibrate the control system model.
  • Generate discrete-time state-space octave model.
  • Implement discrete-time algorithm using microcontroller or DSP (as required).

The Model

Controllable Parameters

Extruder

  • Heater On/Off (PWM control code)
  • DC Motor Voltage (PWM control code)
  • Nozzle aperture diameter (fixed)
  • Incoming filament diameter (fixed)

X Axis

  • Stepper Velocity (step rate)

Y Axis

  • Stepper Velocity (step rate)

Z Axis

  • Stepper Velocity (step rate)

Observable Parameters

Extruder

  • Relative Nozzle Temperature (thermistor ADC code)
    • Closed loop
  • Calibrated Nozzle Temperature (thermocouple based digital thermometer)
    • Open loop
  • Incoming filament position (with encoder wheel/sensor)
    • Closed loop
  • Incoming filament travel (callipers)
    • Open loop
  • Outgoing filament diameter (callipers)
    • Open loop
  • Outgoing filament length (callipers)
    • Open loop
  • Outgoing filament mass (scale)
    • Open loop
    • Possibly closed loop with build platform integrated weight cells.

X Axis

  • Endstop activation
    • Closed loop
  • Position (ruler)
    • Open loop

Y Axis

  • Endstop activation
    • Closed loop
  • Position (ruler)
    • Open loop

Z Axis

  • Endstop activation
    • Closed loop
  • Position (ruler)
    • Open loop

Variable Definition Table

Global Variables

Subsystem Variable Units Description
Global Tra Celcius Room Ambient temperature

Build Platform and Chamber

Subsystem Variable Units Description
Build Platform Vbp Volts Build Platform, PWM generated voltage through nichrome
Tbp Celcius Build Platform temperature, ADC sampled thermistor
Mbp grams Build Platform mass, including deposited material over time.
Build Chamber Tbc Celcius Build Chamber temperature, ADC sampled thermistor

Extruder

Subsystem Variable Units Description
Extruder Vem Volts Extruder Motor, geared DC, PWM generated voltage
θwe Degrees Rotational Extruder displacement of drive motor shaft.
Veh Volts Extruder Heater, PWM generated voltage through nichrome
Ten Celcius Extruder nozzle temperature, ADC sampled thermistor
Dif mm Input Filament diameter, entering extruder
Def mm Exiting Filament diameter, emerging from nozzle
Den mm Exit Nozzle diameter

Motion Control

Subsystem Variable Units Description
X Axis Vlx mm/s Linear X velocity
Dlx mm Linear X position
θwx Degrees Rotational X displacement of drive motor shaft.
Y Axis Vly mm/s Linear Y velocity
Dly mm Linear Y position
θwy Degrees Rotational Y displacement of drive motor shaft.
Z Axis Vlz mm/s Linear Z velocity
Dlz mm Linear Z position
θwz Degrees Rotational Z displacement of drive motor shaft.

References

Books

  • Digital Control Systems Design
  • Modern Control Systems

Online Course Material

MIT OpenCourseWare

Electrical Engineering and Computer Science

Mechanical Engineering

Materials Science and Engineering

Personal tools