Robot base design

A few factors need to be considered when design a robot base.

• Driving power
• Complexity of mechanics design
• Complexity of kinematics
• Complexity of open loop control and feedback control

Following diagram layout a few commonly used design:

There is another important design call Omni-directional drive system with "Mecanum wheel". There is a video footage on http://www.airtrax.com/ website clearly shows vehicles moving sideways, turning on the spot, moving diagonally, and combining these movements.




References:
Thomas Bräunl, Embedded Robotics, 2nd edition, 2006
Christof Roehrig, Controller Design Experiments,1999

Plate-Bot joined my robot team

Here is the Plate-Bot (I named it) that has joined my robot team very recently, the size is about 4 times lager than the first arriver Boe-Bot. Plate-Bot joined my robot team with minimum electronics or call it just a robot base should be more suitable. A lot of add-on electronic components are required to make it suitable to perform my project tasks.



Below is the draft layout that indicates the changes.



Thanks to Mr. Chia our lab technician, who has helped me to source this robot and given me a lot of valuable advices!

plan to change the bigfoot-Bot

After a few days of analysis, I decide to make a few changes on the Bigfoot-Bot (I named it). Due to all wheels are connected to motor by rigid shafts, the kinematics for the robot to turn around will be different from Boe-bot. The way it can turn around is by wasting large amount energy on sliding wheels, where control of the robot in many aspects will be difficult. Hence I decide to modify the robot base and change the electronics, so that it can be better fit into my project.

Lots of works needed to make the changes…

I layout the following graphs to make everything in plan and allow myself to have more directed view on it. (Some friends asked me what is the software that I usually do the layouts, it is Microsoft Visio.)

List of the changes

• One set of gear train and one encoder will be added. (parallel with the other side)
• One set of Parallax education board, Basic Stamp 2 and embedded Bluetooth will be added.
• Two front wheels and dc motors will be replaced by one swivel wheel.

Wireless Communication implementation accomplished

The wireless communication link has been established, which means PC can remotely control the robot and transfer data with the robot. There are some tricky parts during the process, which made the process become more challenging.

Example like, the newly released Microsoft Robotics Studio 1.5 CTP does not work well with BoeBot, I was trying figure out the problem in every parts that involved in the communication link other then the Microsoft Robotics Studio 1.5 but the whole comm. system did not turn out right, in the end with the help from a friend who is familiar with Labview testing, we conclude the problem must due to the software part. When I reversed to the Microsoft Robotics Studio 1.0, the whole system worked fine.


A new robot has joined my robot team. This robot has been used by other people previously for another project. This robot looks like to have a robust base but an old weak "heart" and only one wheel attached with encoder. I think there should be a lot of works to do to make it suitable for the tasks in my project.

BoeBot has been initialized with basic functions

The close-up for Bluetooth communication pair.



The electrnoic compass for finding the orientation of the robot. I have to say thanks to Yue Khing over here, he generously lend this cool chip to me to test on my robot. In future, I will write an article to list out the sensors that I have tried and some analyses regarding that.



The close-up for the BoeBot.

Concept plan for Multi-robot system implementation : part 1 the project settings

The multi-robot system lab implementation setting consist the followings:

• Three mobile robots all equip with Bluetooth and IR, differentiate each other by motor power output.
• An overhead camera system integrated with localization capability.
• Cubical paper boxes with different sizes, and size made proportional to mass.

Initialization of the Boe-Bot

Yeah! Exam is over and I can fully concentrate on the project works.

The second robot did not arrive in expected time, due to various reasons, but luckily it is confirmed that it will arrive soon.

The guide book come together with BoeBot kit is comprehensive, which make the robot initialization become a very enhancive learning process. I doing the initialization according to the flow chart shown in left.

The Subsystem testing includes write small programs for testing the microcontroller I/O, testing and centering the servos.

Assembly the robot kit is really a fun job, it's like dream come true kind of feeling.

There are some sensors included in the BoeBot kit can be used for navigation. Like tactile navigation with Wiskers, Light Sensitive Navigation with Photoresistors, also can navigate with Infrared Headlights.

For the wireless communication, the plan is to adapt to Bluetooth and all robots as well as servers are equipped with Bluetooth transceivers, so that within the wireless network all info can be shared.

The Localization implementation will be talked in later days.