DRAPA Challenge, Dynamic Walking 2017.

Introduction


Rando is a dynamic walking robot which was developed with an open-source mindset, to expand accessibility to and involvement in walking robot education and research. In particular this kit is intended to promote the use of Maker-style methods, materials, and components for better robot enginering design as well as the use of such devices for simplified scientific studies of fundamental principles of legged locomotion.

Rando the Walking Robot


Rando has four legs which are operated in pairs to achieve effectively bipedal locomotion, while the leg configuration helps ensure passive lateral stability. The robot uses a prismatic "ankle" to apply discrete push-off actuation, and a foot switch on each of the leg pairs (inner and outer ) to detect ground contact. A very simple control algorithm is used to trigger a push-off event on the trailing leg in walking which is proportional to the amount of time elapsed since the previous ground-contact event of the opposite leg. The effect of this is to restore the appropriate amount of energy lost between each step and continue walking at steady state.
Rando on Schynige Platte
Hiking with Rando on Schynige Platte
(Disclaimer: the robot cannot actually hike over such rough terrain...yet )

side view of Rando front view of Rando
Side and front view of Rando

Build one


A list of necessary components and design files are provided for fabricating a Rando walking robot from scratch. All components are either available off-the-shelf from a variety of suppliers, or fabricated with common hobby or Maker tools.

Rando kit Rando kit

Assembly Instructions

Instructions coming soon

List of Parts and Materials

Mechanical:
QuantityPartSupplierCost
4Micro ServoTower Pro SG90$15.16
4M2.5x10 ScrewMcmaster$0.40
8M3x10 ScrewMcmaster$0.36
4M3x8 ScrewMcmaster$0.12
4M2x10 ScrewMcmaster$0.15
2M4x16 ScrewMcmaster$0.17
2M5x10 ScrewMcmaster$0.16
4M2.5 Hex NutMcmaster$0.04
4M3 Hex NutMcmaster$0.08
2M4 Hex NutMcmaster$0.02
4M5 WasherMcmaster$0.08
8M4 WasherMcmaster$0.15
83/16" ID x 0.135" aluminum grommetMcmaster$0.82
12No.2 x 0.25" wood screwsMcmaster$0.30
16mm OD x 4.9mm ID x5" aluminum tubingMcmaster$1.35
229.3mm x 3.52mm compression spring Mcmaster$0.15
46" length stiff steel wire or un-bent paper clip found in the office$0.15
16mm ID drinking strawMcmaster"found" near an icee vendor
13mm MDF sheet ~12"x12"AlwaysHobbies.com $0.93
11" width x 1.5" length ahesive hook/loopMcmaster $0.25

Electrical:
QuantityPartSupplierCost
1Arduino NanoAmazon$21.95
1LM7805 voltage regulatorDigi-Key$0.95
21K Ohm resistorDigi-Key$0.20
26 pos , 2x3 male headerAmazon$0.84
11.5inx2in PC board Amazon$3.36

Total Cost: $46.78

Substitutions

The largest expense of the current robot model is the Arduino Nano used for control, however this is overkill. Only 4 PWM outputs and two digital inputs are necessary to drive this version of the robot. Many other low cost microcontroller modules are available off-the-shelf that could be used instead. Some possible alternatives include:

  • Teensy LC - $12.95, Sparkfun
  • Raspberry Pi Zero W - $10.00, Adafruit
  • Arduino Pro Mini 328 - $9.95, Sparkfun
  • NodeMCU - $8.79, Amazon
  • ATtiny84 - $2.95, Sparkfun

  • Any component or material can be substituted for another of your choice; in fact, it is encouraged!

    File Downloads

    DXF Parts
    Eagle CAD Schematic
    Arduino code

    Fritzing Rando

    Cool Links


    Useful, inspirational, and creative online resources for building robots and more from rapid, low-cost fabrication techniques.

    thingiverse.com
    Open source CAD models for 3D printing, laser cutting, etc.

    instructables.com
    Detailed tutorials for building many things.

    makezine.com
    Maker news, inspiration, and ideas.

    adafruit.com
    Blog and online electronics store.

    sparkfun.com
    Blog and online electronics store.

    Charles' blog
    A blog by a great Maker

    Shane's blog
    Another blog by a great Maker


    DYNAMIC WALKING 2017
    Matthew Robertson, Jamie Paik, Reconfigurable Robotics Laboratory
    Amy Wu, Auke Ijspeert, BioRobotics Laboratory