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Mechanics and Construction / Actuators too small to simulate human arm?
« Last post by Michael7S on March 07, 2017, 03:55:08 PM »
To simulate human arm action,  I can build an aluminum test cage and the arm that pivots in the same dimensions as an adult human arm.

Actuator choice will be pivotal ( ;) ) to design of the arms and I could use some pointers on which style/sizes of actuators would be a good starting point.

Some more info: The arm action simulates the plunging of a 12 pound tool, e.g., a soil tamper or post hole digger, for up to 36 inches of vertical travel, at the 'hand'.  Simlar to this video:
  The cage can remain stationary.   Ultimate goal is to measure the impact force of various designs of hand-operated soil compaction tools.

Thank you for pointers -- either to devices or places where more research can be done.  Most of my searches have included terms like "simulate human arm" and "actuators for axial acceleration" among others, but the results seem to be focused on human performance and medical. 

Electronics / Will this still work with a more powerful dc motor?
« Last post by byrlle09 on March 02, 2017, 07:35:26 AM »
So I have this project(RC Multipurpose planter with solar panel) for my final year in mechanical engineering, and i have been researching on electronic schematic diagrams. I don't have much knowledge on making circuit diagrams so i searched for one.

And this is what i have found, a simple and small diy remote controlled robot schematic diagrams. (See site and pics) (Credits to the publisher)


Transmitter Circuit:

Receiver Circuit:

It is relatively simple and easy to build. I think this is gonna work for my project.

I'm gonna need a larger dc motor since the weight of my robot is about 30kg (about two 40W power of a 12VDC motor)(Moving at 2km/hr)
And im gonna add a solar panel for recharge-ability and sustain.

My questions are:
1. Will this still work and not fry up even if i use a larger motor? (Since ill have a larger motor, ill have a higher amperage for a constant 12V DC motor)
2. How do i configure this circuit to meet my required power to drive my 30kg robot.
3. How and where do i install my solar panel?
4. Any recommendations?

Misc / GTF ROBOTS Omni wheels
« Last post by GTFRobots on March 01, 2017, 05:02:11 AM »
GTF ROBOTS has been in design, manufacture and supply of robotics and electronics since 2006. Production of robotic wheels is the main field of our company. Today we can supply the demand of many manufacturers, suppliers, students, and participants in the robotic competition for the robot wheels. We are main supplier of ?Omni Directional Wheel". There are highly qualified and committed staffs in the workshop and new facilities can solve lots of production needs.

Multi-directional ability powerful Aluminum body with high friction rubber to move straight, thin body in order to make it able to place easily in all kinds of robots without wasting space, Especially when Robot size is limited.
The assembly consists of a main wheel and traversal rollers.

Some of the advantages of this product are:
? Multi-directional ability
? no need to turn around
? saving time and energy
? able to circle arrangement with only 3 wheels
? 3 cyclic arrangements.

We make sizes between 50mm to 150mm with hole diameter of 4mm or 6mm with 4 Grades.
Our Omni directional wheels can be customized according to the customer order. We can change material or size of the Omni wheels and add bearing to the wheels.
Mechanics and Construction / Re: 1 inch OD Omni-wheel
« Last post by aika2016 on March 01, 2017, 03:48:02 AM »

Look at these Omni wheels: www.gtfrobots.com

good luck
Robot Videos / impressive new Boston Dynamic biped
« Last post by Admin on February 27, 2017, 02:14:53 PM »
Watch to the end, its insane!

I think Boston Dynamics is trying to marry bipedal locomotion with the efficiency of wheeled locomotion, and this is by far the best attempt I've seen.
I have attached 4 Ultrasonic Sensors on my motor driven autonomous robot. It has a servo-driven steering.
I am using Arduino mega to program the robot. The values of all 4 sensors are pretty accurate when I see them on the serial monitor with the motors off. But as soon as I turn the motors on, I start getting junk and inconsistent distance values on the serial monitor. I did this test while the bot is on the Jack, so it is not moving when I turn the motors on.

I guess this is happening due to the interface to ultrasonic sensors due to vibrations of the motors. Therefore I am guessing these junk values would increase as soon as I keep my bot on the ground.

Please helm me remove these junk values and figure out a way to get exact distance readings while the motors are running.
Misc / all Axon prices reduced ~7% starting today
« Last post by Admin on February 22, 2017, 04:43:18 PM »
New year, new prices.

7% reduction on all Axon, Axon II, and Axon Mote prices.


Mechanics and Construction / Gearbox cleaning
« Last post by ericthet on February 21, 2017, 03:41:53 PM »
I picked up a used liberty differential drive wheelchair and started stripping it down.  I added a Sabertooth 2x32 motor controller and noted that the current pulled on one of the motors was about twice the other one.  This wheel also ran about 10RPM slower and struggled more.  After taking it apart (I thought it might be the electronic brake) it appears it might be the gear box.  I only have the other motor to compare to but the gearbox takes about twice the power to turn and feels "sticky".  I don't hear a lot of grinding or mechanical noise it is just slower/gummier.

I did pull the gearbox apart real quick and noticed it full of gear oil or grease.  This is where I am kind of stuck.  I am not sure if the oil/grease is the problem (went bad?) or if maybe the bearings went bad.  My guess is the bearings as the oil/grease appears a healthy color.  However I don't know what kind of lube is in it or what to replace it with if I rebuild.

From what I can tell it is a 1:19.3 reduction (printed on a sticker) and the manufacture is MTM.  There is a serial code but searching doesn't pull anything up.  I am hoping to rebuild this gearbox as all the mechanics work nicely together.  I have a metal lathe (and know a bit how to use it) and have some basic mechanical knowledge. I am stronger in the electronics side which is why I am starting with this base to get going.

My big questions are:
1. What gear oil/grease should I rebuild this with and is there a way to tell what it is currently?
2. Is there an easy way to tell why the gearbox is struggling? 
3. Is there a way to test the bearings?

To rule out the motor I am thinking of putting the suspect gearbox on the good motor and vice versa and see if the problem persists with the gear box.  I am pretty confident it is, as the current was the same on both motors when the gear boxes were removed.  Also it is very noticeable that the suspect box has lag when hand turning.

For some reference the motors are 200W 24V.  With the gearboxes the good one only averages around 1-2 amps with no load.  The suspect unit was about 4-5amps no load and ran about 10RPM slower.  Without the gearboxes the motors were under 1amp no load. 

If I rebuild the one I might need to just rebuild the other if I need to ship bearings to get them to a known good state....

Any help would be.. helpful!

Misc / Hello
« Last post by M on February 21, 2017, 05:17:26 AM »
Hello. I am a mechanical engineering student. I am very interested in learning robotics. Its a part of my journey to find my passions. Anyways, I don't know where to start. My experience in robotics is that three years ago I made an RC car on aurdino, with wired, wireless controller and also controlled by laptop. I didn't learn the whole language, only the one needed to make the car. The basics. Then, two years ago, I made a line follower and a wall follower two years ago and last year, I learned to make a robotic arm in a seminar by A set. Since all the lessons were in seminars, they were quick and event based. No permanent learning, I hope that makes sense.

 So now I am here. I decided to learn how to make a drone. I read some notes about it and I am not sure what exactly to do in order to start. The first step?? And what is the purpose of learning the kinematics and dynamics of it. Is it helpful in programming? And how to learn programming a quad copter. And is making a quadcopter a good choice? Or should I start with something else?
Edit: Sorry I didn't see the "For the beginners" thread. I still hope that people will help. sorry and thank you.
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