Hobby Robotics

Removing Weight from Small Cellphone Vibrator Motors

2008-03-12T17:39:00.000-07:00

Robots nowadays are getting smaller and smaller. I wanted to make a very small mobile robot. I found out that cellular phone's vibrators are tiny motors but with unbalanced "weight" at its end rotating. These tiny motors have strong torque and just fit for my purpose. But removing the "weight" is difficult.

I wondered how to remove the "weight" on small cellphone vibrator motors. Forcing it may damage this fragile motors. I tried to search the net and using Google and found this site Tiny Motor. Now I can start building my tiny bot.

Embedded Programming and Electronics Blog

2007-12-27T15:36:00.000-08:00

I have created a new Embedded Programming and Electronics Blog. This site is for my day to day adventure as a technology geek featuring my findings or work to share to other geeks.

Robotic Muscle

2007-12-19T01:27:00.000-08:00

There have been many attempts made to re-create human anatomy through mechanical means. The human body however, is so complex that it is very difficult to duplicate even simple functions. Robotics and electronics are making great strides in this field, of particular interest are limbs such hands, arms, and legs.

In order to reproduce human extremities there are a number of aspects that must be considered:

The gripping force required to manipulate different objects (eggs, pens, tools)
The motion capabilities of each joint of the hand
The ability to feel or touch objects (tactile senses)
The method of controlling movement within the limb
Emulating real human movement (smoothness, and speed of response).

Many different solutions have been proposed for this problem, some include using "muscles" controlled by air pressure, piezoelectric materials, or shape memory alloys. Shape memory alloys mimic human muscles and tendons very well. SMA's are strong and compact so that large groups of them can be used for robotic applications, and the motion with which they contract and expand are very smooth creating a life-like movement unavailable in other systems.

Creating human motion using SMA wires is a complex task but a simple explanation is detailed here. For example to create a single direction of movement (like the middle knuckle of your fingers) the setup shown in Figure 1 could be used. The bias spring shown in the upper portion of the finger would hold the finger straight, stretching the SMA wire, then the SMA wire on the bottom portion of the finger can be heated which will cause it to shorten bending the joint downwards (as in Figure 1). The heating takes place by running an electric current through the wire; the timing and magnitude of this current can be controlled through a computer interface used to manipulate the joint.

There are still some challenges that must be overcome before robotic hands can become more commonplace. The first is generating the computer software used to control the artificial muscle systems within the robotic limbs. The second is creating large enough movements to emulate human flexibility (i.e. being able to bend the joints as far as humans can). The third problem is reproducing the speed and accuracy of human reflexes.

The wires in such robotic hands are modeled through simple experiments. The first link takes you to a video clip showing one of these simple experiments in action. The next link is demonstration of how the interactive applet modeling this experiment works, while the third link goes to the applet itself. Finally, the fourth link is to a game involving an SMA wire in the context of the experiment you have just seen.

Micro Swimming Robots

2006-09-12T21:57:00.000-07:00

Micro Swimming Robots for medical applications

Goal: Developing a microrobot which can travel to currently inaccessible parts of the body and perform user directed tasks such as highly localized drug delivery and screening for diseases that are in their very early stages.

Approach: For such a miniature device to be injected into the body, it has to be 800 µm or smaller in diameter. Miniature, safe and energy efficient propulsion systems hold the key to maturing this technology but they pose significant challenges. Scaling the macroscale swimmimg mechanisms to micro/nano length scales is unfeasible. It has been estimated that a vibrating-fin driven swimming robot shorter than 6 mm can not overcome the viscous drag forces in water. The objective of this fundamental research effort is to explore swimming mechanisms at small length scales and develop a biomimetic swimming robot inspired by micro-organisms motility mechanism. We propose a new type of propulsion inspired by the motility mechanism of bacteria with peritrichous flagellation, such as Escherichia coli, Salmonella typhimurium and Serratia marcescens. These robots are intended to swim in stagnation/low velocity biofluid. Potential target regions to use these robots include the urinary system.

Current Status:Prior to fabrication of the microrobot, the perfomance of the propulsive systems is predicted by modeling the dynamics of the motion. The motion of the moving organelle along with the body is simulated and key parameters such as velocity, force distribution and power requirments for different configurations are determined theoretically. In order to validate the theoretical result, a scaled up prototype of the swimming robot is fabricated and characterized in silicone oil using the Buckingham PI theorem for scaling. The results are compared with the theoretically computed values. These robots are intended to swim in stagnation/low velocity biofluid and reach currently inaccessible areas of the human body for disease inspection and possibly treatment. Potential target regions to use these robots include eyeball cavity, cerebrospinal fluid and the urinary system.

Benefits: We envision this robot having the capability to swim to inaccessible areas in human body and perform complicated user directed tasks such as diagnosis of diseases at early stages and targeted drug delivery.

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DIY Robot :Solar-Bug (Fred)

2006-07-11T21:48:00.000-07:00

2 Transistors 2N3904
2 pager motors, high-efficient motor
1 solar panel, 3 volts
2 Transistors 2N3906
2 pager motor holders
1 capacitor, 2200uF, 16V
2 blinking LEDs (green or red)
2 resistors 3.3k Ohms, 1/4 watt, 5%
copper wires & heat-shrink tubing
2 tantalum capacitors, 0.22uF
2 resistors 30k or 33k Ohms, 1/4 watt, 5%

1. 2N3904, bend the base lead (middle lead) toward you.
The labelled flat-side facing you and the leads are pointing downward.

2. 2N3906, bend the collector lead (the third lead) away.
The labelled flat-side facing you and the leads are...

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Bipolar Stepper Motor Controller

2006-07-11T21:44:00.000-07:00

Here's a little circuit that simplifies interfacing to bipolar stepper motors. It's similar to a common unipolar design available on the internet. However, I modified it to use a pair of MOSFET-based H-bridges. In addition, I added an enable signal so that the motor windings can be disabled to save power. Since there are diodes embedded in the transistors, there's no need to add flyback current protection across the motor windings.

A couple of notes: ORCAD does not explicitly show the power connections for the logic devices so be sure and connect the flip-flop and XOR gate packages to...

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Robot Information Central

2006-07-11T21:40:00.000-07:00

Questions about robots
Robot site of the week
Build your own Robot Article
Robot colleges/universities and Labs
Robot Related FAQs
Robot Competitions & Contests
Robot Construction Toys and Modelling
Robotics resource lists by Arrick Robotics
Find Companies
Looking for robot toys?
Robot Information Web Sites
Want to buy a robot for research?
Robots in the Movies and on TV
Robots in Cartoons and comics
NASA & Space Robots
Patents in Robotics and A.I.
Books and Magazines for Robot Builders
Programming Languages
Law Enforcement Robots
Artifical Muscles
Wearables
Exoskeletons
Parts and Plans for Robot Builders
Robot Groups & Clubs
Robot and Automation Trade Organizations

Robot Search Engine Results
Robotics at Universities
AI, GA, CA, Neural Nets
Stories about Robots
Radio Data links
BEAM Robots
Teleoperated Web Robots & On-Line Cameras
Robot Art, Puppets, Animatronics
Circuits & Electronic & Robot kits
Printed Circuit Boards
Robotics Mailing Lists
Robotics for the Disabled
Software Resources, Linux, Operating Systems
Microcontrollers, Embedded, Desktop Computers
Motors and Motor Control
Sensors, Input Devices
Walking Robots
Robot Games
Robotics Simulation
Vision Related
Some Great Robots and Web Pages
Robots in Hazardous Enviroments and Underwater
Some Robotics Companies
Your tax dollars doing robotics work
Robot-Related Newsgroups
Unsorted

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Tiny Threads - Tiny Multitasking Threads for Microcontrollers

2006-06-29T22:18:00.000-07:00

by: Regulus Berdin

Idea based on http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html.
Only 1 byte RAM needed per thread.
Very small overhead context switching.

Limitations:

Maximum 254 lines per thread.
Thread context switching will not work within a switch block.

Usage example:

     TT_DEF(1)
    {
       TT_BEGIN(1);
     while (1)
       {
          ...
          TT_SWITCH(1);
          ...
          ...
          TT_WAIT_UNTIL(1,keypress);
       }
       TT_END(1);
    }
   
    TT_DEF(LED_TASK)
    {
        TT_BEGIN(LED_TASK);
        while (1)
        {
            LedOn();
            delay=DELAY_1_SECOND;
            TT_WAIT_UNTIL(LED_TASK,delay==0);
            LedOff();
            delay=DELAY_1_SECOND;
            TT_WAIT_UNTIL(LED_TASK,delay==0);
        }
        TT_END(LED_TASK);
    }
    
    void main(void)
    {
        ...
        ...
        while(1)
        {
            TT_SCHED(1);
            TT_SCHED(LED_TASK);
        }
    }

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nBot Balancing Robot

2006-06-28T22:38:00.000-07:00

David P. Anderson

I've been working on a two-wheeled balancing robot, nBot .

This robot was featured as NASA's Cool Robot of the Week for 19 May 2003. Thereafter Scientific American's online website, SCI/Tech Web Awards, honored the NASA page as one of the top 10 engineering and technical web sites for 2003, referencing nBot in its text. nBot is also featured in a new O'Reilly book spun off from Make Magazine in 2006, called The Makers.

The basic idea for a two-wheeled dynamically balancing robot is pretty simple: drive the wheels ...

The robot hardware was built in my home machine shop. Here as some exploded views of the motor platform and drive components, as well as the castering tailwheel, now removed, which was used for testing and calibrating the motors and encoders before nBot was able to balance on two wheels. The robot uses the HC11 robot controller developed for the M.I.T. 6.270 Robotics Course, the same robot controller used on the LegoBot and SR04.

Rev 1. This began as an experiment to learn to control an inverted pendulum. I began with a three wheeled robot with a ball-bearing pivot used to attach a 3 foot wooden pole topped with an orange Nerf Ball. The pivot has a low-friction 5k potentiometer used for measuring the tilt angle of the pole. I moved the battery pack over the rear wheel to give more stability. Here is an mpeg movie (10 Meg) of the robot balancing the pole in my office. Here (3.3 Meg) is a shorter version, and here (3.7) is another.

Rev 2. After learning to balance the pole, the robot was re-built as a two-wheel version, with the battery mounted directly above the wheels. The ball-bearing pivot was attached to the bottom of the robot with a short aluminium feeler touching the floor. In this way the robot can sense it's angle to the floor and, assuming the floor is level, to gravity as well. The aluminium feeler has a teflon pad on the end to help it ride over cracks and joints in the floor.

Rev 3. For the third version a third deck was added and the batteries moved to the top deck. This allows the robot to generate more torque without having to tilt over as far. The side view of the platform shows the battery and user interface on the top deck, the microcontroller and h-bridge on the middle deck, and the motors...

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Using Old Disk Drive Motors

2006-06-26T21:46:00.000-07:00

Hobby Robotics

Hobby roboticists have been around almost as long as computer enthusiasts. They are the ultimate tinkerers, often turning inexpensive or used parts into highly autonomous robotic systems. The success of Lego's Mindstorms™ robot kits, which were developed in collaboration with MIT, punctuates the growing fascination of kids and grown-ups alike with building robots of their own. Then there is the huge success of robot competitions including robot soccer tournaments and robot demolition derbies (e.g. BattleBot).

Just like an industrial manipulator, a medical robot or a haptic device, hobby robotics is about mechatronics, requiring skill in and passion about electromechanical design and software.

Most hobby robots, though not all, have a relatively simply microcontroller (such as Motorola's 68HC11, Parallax's Basic Stamp), rather than the typical high speed microprocessor found in industrial robot controllers (e.g. Motorola 68040 in Adept controllers, PowerPC in Fanuc controllers, etc.).

Often, relatively inexpensive motors and sensors are found on these robots. Some of these robots employ high torque motors found on hobby racecars.

Hobby roboticists are excellent recyclers, often reusing components salvaged from used or surplus disk drives, radios, calculators, etc.

Images courtesy of CMU's Robotics Institute

Regardless of the costs of the system, many of these kit robots have interesting design and performance. Take for example the robot in the above image. This is a PalmPilot-driven robot developed by Carnegie Mellon University's Robotics Institute, which has garnered a great deal of recent press. This is a robot with three omni-wheels, which can rotate in two orthogonal directions, leading to a holonomic design in the sense that the robot can move in any direction at any time (typical wheels can only rotate in the plane normal to its axis, which is a non-holonomic constraint, so that it cannot always from from a given starting point to a given stop point in a direct path). The robot has a Pontech SV203 board for motor and IR sensor control and a PalmPilot for high level control. The use of a popular PDA for control provides relatively powerful computing and a graphical user interface at a low cost. More details about the software and hardware design can be found at CMU's website. Acroname is currently selling an unassembled kit as well as a preassembled version of this robot...

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Open Automation Project

2006-06-25T21:46:00.000-07:00

The objective is to use readily available "off-the-shelf" low-cost consumer components where possible, and to design electronic subsystems where such components are either not readily available or are too expensive. In terms of affordability, the overall goal is to design a robot that can be made for around the price of a PC (US$1,500 to $2,000 is the target, but the actual cost of building a robot can vary greatly depending on how many of the electromechanical components are made in your own workshop versus purchased pre-fabricated).

Overview

The block diagram below identifies the major hardware components that comprise the robot and its accompanying docking station. The cyan coloured blocks represent custom electronic circuits - all microcontroller based with firmware - that have been developed within the scope of this project.

Operating System

The free and open GNU/Linux operating system has been chosen as the foundation for the software in this project. Kernel and device-driver source code is readily available and well supported by the developer community.

Mainboard

The requirements of the mainboard are:

at least two firewire ports
at least two serial ports
at least two USB ports
I²C port (optional)...

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Walking Robots

2006-06-22T22:12:00.000-07:00

Welcome to WalkingRobots.com, a tome of information dedicated to the development of the walking style of robots.

Ever since the very creation of the word Robot, people think that robots should look and act like humans. But until recently, this has only been a fantasy. Making a true robot that can actually walk like a human, or remotely look like a human, has been trapped in the realm of science fiction movies and books.

Though the recent amazing humanoid robotic development efforts have been conducted by large corporations and research universities with multi-million dollar budgets, humanoid robots can actually be built at home by the average person.

I am hoping that the information that is presented here will help to inspire, and will help you to learn how to begin "walking" in your robotics development efforts.

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First Entry

2006-06-20T22:41:00.000-07:00

This is a new robotics site intended for hobbiest. Check out also my other hobby electronics circuits blog site.