Team Momo · University of Pennsylvania ESE 5190

Interactive Soft Tentacle Robot with Ultrasonic-Aware Embedded Control

A soft robotic tentacle project that combines embedded sensing, animated LCD expression behavior, and tendon-driven actuation. The curated firmware separates ultrasonic-driven emotion state from joystick-driven tentacle motion.

ATmega328PBPCA9685UltrasonicADCSPI LCDServo control
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Overview

Project Strengths

  • Bare-metal ATmega328PB firmware integrating ultrasonic sensing, LCD graphics, joystick ADC input, and I2C/PCA9685 servo control.
  • US-100 distance measurements classified into interaction states used for LCD emotion behavior.
  • Joystick Cartesian input mapped into direction angle and bending amplitude for `Tentacle_Move()`.
  • Three SG92R servos pull fishing-line tendons to bend the TPU tentacle in different directions.

My Contribution

  • Implemented LCD emotion graphics, animation behavior, and interaction-state presentation on top of existing display support.
  • Implemented and integrated ultrasonic sensing logic that converts successive distance measurements into LCD expression states.
  • Handled a substantial share of debugging across display behavior, sensing, firmware timing, peripheral interaction, and hardware/software integration.
  • Contributed to PCA9685-based three-servo control and tentacle motion integration.

System / Architecture

Architecture

  1. 01Ultrasonic path: US-100 distance measurements -> relative motion classification -> interaction/emotion state -> LCD facial expression.
  2. 02Motion path: joystick ADC -> Cartesian offset -> direction angle and bending magnitude -> `Tentacle_Move()` -> PCA9685 -> three SG92R servos.
  3. 03ESP32/Blynk remote-control path is documented in the final report and demo; the companion ESP32 firmware is not included in the curated snapshot.

Implementation

Implementation

  • LCD behavior includes Joy, Smile, Angry, and Cry expressions with state flags to reduce repeated blocking redraw behavior.
  • The ultrasonic implementation measures echo timing, derives distance, filters implausible jumps, compares successive samples, and classifies approach/retreat behavior.
  • The tentacle motion layer maps direction angle and bending amount into three phase-shifted servo commands.
  • The mechanical design uses an octopus-inspired TPU spiral, 3D-printed base/housing, and three fishing-line tendons.
Hardware integration and bring-up evidence: servos, PCA9685 path, wiring, power, and embedded electronics.

Visual Evidence

Hardware and system artifacts

Mechanical prototype photo showing the flexible tentacle structure during development.
LCD emotion collage used for interaction-state feedback.
Historical system diagram retained by the curated project repository.

Results / Validation

  • Joystick-driven polar-coordinate three-servo motion control and preset motion primitives were demonstrated.
  • Four LCD emotion states and ultrasonic motion-state classification for LCD behavior were demonstrated.
  • Force/current-feedback interaction was planned but remained future work, not a completed closed-loop feature.

Challenges / Decisions

  • LCD animation and refresh were initially too slow due to repeated blocking redraw behavior.
  • Combined actuator/display integration exposed timing and interrupt conflicts.
  • Joystick ADC deadzone and mapping problems required serial/debug instrumentation and threshold correction.