MakerBotControlSystem

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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
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