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.

Hiking with Rando on Schynige Platte
(Disclaimer: the robot cannot actually hike over such rough terrain...yet )

side 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

Assembly Instructions

Instructions coming soon

List of Parts and Materials

Mechanical:

Quantity Part Supplier Cost

4 Micro Servo Tower Pro SG90 $15.16

4 M2.5x10 Screw Mcmaster $0.40

8 M3x10 Screw Mcmaster $0.36

4 M3x8 Screw Mcmaster $0.12

4 M2x10 Screw Mcmaster $0.15

2 M4x16 Screw Mcmaster $0.17

2 M5x10 Screw Mcmaster $0.16

4 M2.5 Hex Nut Mcmaster $0.04

4 M3 Hex Nut Mcmaster $0.08

2 M4 Hex Nut Mcmaster $0.02

4 M5 Washer Mcmaster $0.08

8 M4 Washer Mcmaster $0.15

8 3/16" ID x 0.135" aluminum grommet Mcmaster $0.82

12 No.2 x 0.25" wood screws Mcmaster $0.30

1 6mm OD x 4.9mm ID x5" aluminum tubing Mcmaster $1.35

2 29.3mm x 3.52mm compression spring Mcmaster $0.15

4 6" length stiff steel wire or un-bent paper clip found in the office $0.15

1 6mm ID drinking straw Mcmaster "found" near an icee vendor

1 3mm MDF sheet ~12"x12" AlwaysHobbies.com $0.93

1 1" width x 1.5" length ahesive hook/loop Mcmaster $0.25

Electrical:

Quantity Part Supplier Cost

1 Arduino Nano Amazon $21.95

1 LM7805 voltage regulator Digi-Key $0.95

2 1K Ohm resistor Digi-Key $0.20

2 6 pos , 2x3 male header Amazon $0.84

1 1.5inx2in 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

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