Juan González Gómez, Estanislao Aguayo y Eduardo Boemo

Escuela Politécnica Superior

Universidad Autónoma de Madrid

Locomotion of a Modular Worm-like Robot using a FPGA-based embedded MicroBlaze Soft-processor

7th International Conference on Climbing and Walking Robots

September 22-24. Madrid. Spain. 2004.

Introduction

Mechanical description

Locomotion algorithms

Locomotion Controller

Implementation results on FPGA

Conclusion and future work

Index

Introduction (I):
Modular reconfigurable Robotics

Started in 1994 by Mark Yim

It concentrate on the construction of robots composed of modules

The design is focused on the modules, not the whole robot

Modules are capable of attach and detach one to each other

Therefore, the shape of the robot changes

Introduction (II):
Polybot

One of the most advanced systems

Designed at Palo Alto Research Center (PARC)

Now working on the third generation of modules

G1

No sensors

Electronic and

power outside

Servo

No self-reconfigurables

G1.4

Electronic and

power inside

8-bit microcontroller

Servo

No self-reconfigurables

G2

DC Motor

CPU: Power PC

1MB RAM

CAN Bus

Self-reconfigurable

G3

In development

More sensors

5x5x4.5mm

Introduction (III):
Modular reconfigurable Robotics

An example of reconfiguration (Polybot)

Loop (rolling gait)

Snake (sinusoidal gait)

Spider

Introduction (IV):
Main objetives

...An additional step on modularity is the use of FPGA technology instead of a conventional microprocessor chip.

It gives the designer the possibility of implementing new architectures, faster control algorithms or dinamically modify the hardware to adapt it to a new environment

We are just starting to research on this area

We have designed the simplest kind of modular robot, composed of 8 equals linked modules

The control system is centralized

The locomotion controller is embedded into an FPGA

Mechanical description

Y1 Modules

Based on G1 Polybot modules

Simple and cheap

No sensors

One degree of freedom, actuated by a servo

CAD rendering

Material: PVC

Dimensions: 52x52x72mm

Weight: 50gr

Rotation Range: 180 degrees

Mechanical description(II)

Y1 Modules can be connected in two different ways:

Connection in phase

Connection out of phase

Ground

Articulation's plane

Articulations rotate on the same plane, perpendicular to the ground

Ground

Articulations rotate on different planes

The robot designed consist of 8 Y1 modules connected in phase

It is very chep and easy to construct

Electronic and power supply are off-board

Locomotion is restricted to a straight line

Mechanical description(III)

Locomotion(I)

Locomotion is achieved by the propagation of waves that traverse the worm, from the tail to the head

Gait control tables are used

Each row defines the position of the articulations at an instant

[-19 -9 24 -4 -22 17 12 -18 ]

[-17 -14 21 4 -25 11 19 -15 ]

[-12 -20 18 11 -25 3 23 -7 ]

.

.

[21 0 -23 12 17 -21 -6 22 ]

[19 9 -24 4 22 -17 -12 18 ]

Instant t1

Instant t2

Instant t2

.

.

.

Instant tn

1 2 3 4 5 6 7 8

Locomotion(II)

Algorithm for automatic generation of control tables:

Locomotion(III)

RESULT: We obtain a control table that makes the robot move

An example sequence follows:

Changing the kind of wave and its parameters, different locomotion movement are achieved

we can generate movements based only on the wave parameters

Locomotion(IV)

Low amplitud wave

Ex. Crawling through a tube

Higer amplitud wave

Ex: crossing over an obstacuble

semi-sinusoidal wave

Ex: caterpillar locomotion

Locomotion controller(I)

Gait control table

PWM generator

Movement

generator

Wave parameters:

Wavaform

Amplitude

Wavelength

Servo 8

Servo 1

Software

(Write in C)

Hardware

core

(VHDL)

(MicroBlaze)

Spartan IIE400

PWM

Locomotion controller(II)

MicroBlaze

32 bit soft-processor, created by Xilinx

Soft-processors are written in VHDL. You can design your own hardware

cores and connect them to the processor.

Follows the IBM Core Connect standard Bus, for the connection of peripherals

A comercial board is used:

RS-232

(Software downloading)

Power Supply

5(v)

Expansion

board

(servo conection)

FPGA: SpartanIIE400

2MB RAM

4MB Flash

50Mhz Clock

BRAM

Slices (Area)

I/O pins

Total

Used

Available

14

8

43%

2352

1312

146

10

93%

Implementation results

The Microblaze and the pwm core occupy the 56% of the FPGA resources.

44% of the resource of the FPGA are avaiblable for future improvements

The Software is loaded into external RAM

44%

Implementations results for the synthesis of the locomotion controller into an Spartan IIE400 Xilinx FPGA:

Conclusions

A modular worm-like robot has been constructed, capable of moving on a straight line

Locomotion controller is based on gait control tables, generated automatically from the parameters of the wave applied

The controller has been implemented on a FPGA

A versatile working platform has been developed for further research on Modular reconfigurable robotics in general and Worm-like locomotion in particular

FPGA makes Modular robots even more versatile. New architectures can be designed and new topics are introduced:

Hardware/software codesign

Dynamic Hardware reconfiguration

Future work

Currently, we have two research areas opened:

Modular reconfigurable Robotics:

The design of a new generation of modules, with embedded FPGAs

The construction of new more complex robots, not just worm-like

Work-like robots locomotion

Generation of Gait control tables using genetic algorithms, in order to determinate the optimal table that minimize the power consumption and maximize the stability and speed.

Locomotion on a plane, not just on a straight line

Let's see some videos...

THANK you for your attention

Juan González Gómez, Estanislao Aguayo y Eduardo Boemo

Escuela Politécnica Superior

Universidad Autónoma de Madrid

Locomotion of a Modular Worm-like Robot using a FPGA-based embedded MicroBlaze Soft-processor

7th International Conference on Climbing and Walking Robots

September 22-24. Madrid. Spain. 2004.

2003-04-25T18:22:37