6 votes
Accepted

What actuator types exist that remain locked in their last position like hydraulic piston?

Actuators that use a worm gear can't generally be back-driven; these are the same gearing mechanisms that let you twist a guitar string to tune it without the tension being able to back-drive (and ...
user avatar
  • 14.5k
6 votes

What are the calculations for a badminton robot and mechanisms?

In short, what you are trying to do is well beyond the capabilities of top robotics research labs. That said, here is a short list of general areas you need to look into: Robotic arm dynamics (to ...
user avatar
  • 2,669
5 votes
Accepted

Is there a rule of thumb for actuator torque overhead?

When selecting an actuator, you need to consider not just the force but also the power. Power = force x speed The faster you need to lift the lever, the more power you'll need. Companies like Maxon ...
user avatar
  • 6,337
5 votes

Design and construction of universal robotic arm (5kg, 1m)

To answer your questions about the motors/gearing: To lift 5Kg at 1 metre distance - the "shoulder" torque needs to be 500 Kg.cm or about 5000 N.cm. This is far above the torque of most model servos,...
user avatar
  • 1,001
5 votes
Accepted

Why do series elastic actuators have more accurate and stable force control?

Series elastic actuators tend to have more stable force control because the spring filters out the high-frequency motion of the mechanism. A low frequency in the system dynamics means that you can use ...
user avatar
  • 4,205
5 votes
Accepted

How can a coaxial stepper motor be used to drive the Z axis effector of a SCARA robot?

i found out that it is called an RZ tool ... google scara RZ tool there is a captive rotating "nut" on the threaded shaft that causes the shaft to move linearly ...
user avatar
  • 403
4 votes

Can't Read current on Pololu Dual MC33926 Motor Driver Shield for Arduino

When there is miscommunications between the microcontroller and a chip, assuming the electronics are not damaged, there could be a couple of things that can go wrong. Of course, further diagnosis is ...
user avatar
  • 3,210
4 votes
Accepted

How do I decide the size of the time steps between sensing and control actuation?

Regarding point 1, yes you are understanding the problem correctly. Regarding points 1 and 2, I believe what you are looking for is the Nyquist-Shannon sampling theory. This theory says that your ...
user avatar
  • 14.5k
4 votes
Accepted

What types of actuators do these industrial bots use?

Actuation is a complex subject that cannot be reduces to 1 component alone. It is the interaction of software electronics and mechanics. "Toy" servos tend to incorporate everything in one small ...
user avatar
  • 6,322
4 votes

What servos are suitable for a robot like Boston Dynamics’ Atlas?

The Boston Dynamics’ Atlas robot doesn't actually use servo motors. It uses electrically-powered hydraulic actuation. I saw a presentation by Boston Dynamics' Marc Raibert where (if I remember ...
user avatar
  • 1,009
3 votes

Calculate required motor torque through Harmonic Drive

Page 50 of Hamid D Taghirad's 1997 PhD dissertation from McGill University gives a series of equations for harmonic drive torques, and the top of page 51 gives the following fantastic model for the ...
user avatar
  • 14.5k
3 votes

Spring with electronically adjustable stiffness

Like jwpat said, I think the only package you'll find for what you're looking for is active suspension, but good luck getting official support from the manufacturer unless you have some automotive OEM ...
user avatar
  • 14.5k
3 votes

Is there a rule of thumb for actuator torque overhead?

I always add 100-120% overhead (normally this just means the next bigger unit than exactly what I need) but also this comes with experience, a motor that can just barely lift your load will do so very ...
user avatar
  • 1,909
3 votes
Accepted

Vacuum Lifter: Moving Playing Cards

Vacuum gripper - I think. Perhaps something like the lynxmotion version, which generates the vacuum with a motorised syringe: http://www.lynxmotion.com/p-788-vacuum-gripper-kit.aspx Alternatively - a ...
user avatar
  • 1,001
3 votes
Accepted

2Nm small motor

First I would like to caution your choice of motor torque. I don't know how you generated the drawing of your wrist, but CAD packages like Inventor or Solidworks can easily generate masses and ...
user avatar
  • 14.5k
3 votes
Accepted

Adding an Actuator or Force to a (Featherstone) Articulated Rigid Body Model

Actuators Forces Do I get this right: you have a theoretical model of a rigid multibody system and would like to perform rigid body dynamics computations. You have implemented the model and now would ...
user avatar
3 votes
Accepted

Linear actuators in a cartesian robots

I have worked on a cartesian robot with similar requirements† as your own, and we selected direct drive synchronous linear motors for our x/y stages. In our case, both axes were around 2m in ...
user avatar
  • 4,088
3 votes
Accepted

Electronic circuit for heating nylon fishing line muscle

what metal should I use? Copper wire works better than nichrome wire, according to Homemade Artificial Muscles IV. That says Nichrome is used in places like your toaster mainly because it can get ...
user avatar
  • 4,375
3 votes

What types of actuators do these industrial bots use?

A robot like the one you refer to probably has a mix of transmission types that increase in power-to-weight ratio and decrease in size and stiffness as you move outwards on the kinematic chain. The ...
user avatar
  • 86
3 votes
Accepted

Does MIT Cheetah uses Series Elastic Actuator?

It seems that the answer is that it doesn't actually use either of those designs. According to the paper Proprioceptive Actuator Design in the MIT Cheetah: Impact Mitigation and High-Bandwidth ...
user avatar
  • 1,009
3 votes
Accepted

What is the typical intro example for control systems for a spherical joint?

The best example I can think of would be the spherical pendulum. Albeit, this is not exactly the easiest thing to regulate as you have two degrees of freedom and a frictionless contact (well depending ...
user avatar
2 votes

Adding an Actuator or Force to a (Featherstone) Articulated Rigid Body Model

If you haven't come across the Rigid Body Dynamics Library (RBDL) you might want to look at how they implement it, and/or contact the author Martin Felis.
user avatar
2 votes

Building industrial-like robotic arm

A machinedesign.com article, “Exclusive interview: Gill Pratt on how compliant actuators revolutionized robotics”, includes a close-up picture of an SEA (series elastic actuator) mechanism developed ...
user avatar
2 votes

Building industrial-like robotic arm

A series elastic actuator is really just a motor/gearbox with passive compliance built in (hence the spring). A google search finds http://ihmc.us/groups/sea/ (with links to some specs and ...
user avatar
  • 1,001
2 votes
Accepted

How can i make a compact soft robot

I think dielectric mechanism like piezo are suitable for compact designs. These might be usefull http://en.wikipedia.org/wiki/Piezoelectric_motor https://www.google.com/patents/US4812698
user avatar
  • 1,084
2 votes

Can't Read current on Pololu Dual MC33926 Motor Driver Shield for Arduino

I know this thread is old but it's high on Google results and I would like to clarify for anyone who stumbles upon it in the future an answer not yet listed: this chip is not designed to read current ...
user avatar
2 votes
Accepted

Stewart platform as robotic wrist joint

The "best" robot wrist in terms of human analog is probably the omni-wrist by Mark Rosheim. It has a large range of motion, and does not have singularities or gimbal lock that plague other more ...
user avatar
  • 5,215
2 votes

Stewart platform as robotic wrist joint

Bear in mind a Stewart platform has six degrees of freedom - yes it does reproduce the main motions of the human wrist, but it adds extra ones such as the ability to change its overall length. There ...
user avatar
  • 1,001
2 votes

Electronic circuit for heating nylon fishing line muscle

As far as how to heat the nylon muscles, one of the articles that you have linked to provides a number of methods for doing so. The two most promising from an experimental perspective are submersing ...
user avatar
2 votes

How to get started on making a dispenser for Indian spices?

You should have a look at small screw conveyors. Either experimentally find out how much you have to turn for your spices or make a feedback loop with a scale.
user avatar
  • 1,335

Only top scored, non community-wiki answers of a minimum length are eligible