actuator

31 Articles

3D Printed Absolute Encoder Is Absolutely Wonderful

November 10, 2021 by 25 Comments

When you need to record the angle of something rotating, whether it’s a knob or a joint in a robotic arm, absolute rotary encoders are almost always the way to go. They’re cheap, they’re readily available, and it turns out you can make a pretty fantastic one out of a magnetic sensor, a zip tie, and a skateboard bearing.

When [Scott Bezek] got his hands on a AS5600 magnet sensor breakout board, that’s just what he did. The sensor itself is an IC situated in the middle of the board, which in Scott’s design sits on a 3D-printed carrier. A bearing mount sits atop it, which holds — you guessed it — a bearing. Specifically a standard 608 skateboard bearing, which is snapped into the mount and held securely by a zip tie cinched around the mount’s tabs. The final part is a 3D-printed knob with a tiny magnet embedded within, perpendicular to the axis of rotation. The knob slides into the bearing and the AS5600 reads the orientation of the magnet.

Of course, if you just wanted a rotary knob you could have just purchased an encoder and been done with it, but this method has its advantages. Maybe you can’t fit a commercially-available encoder in your design. Maybe you need the super-smooth rotation provided by the bearing. Or maybe you’re actually building that robotic arm — custom magnetic encoders like this one are extremely common in actuator design, and while the more industrial versions (usually) have fewer zip ties, [Scott]’s design would fit right in.

Continue reading “3D Printed Absolute Encoder Is Absolutely Wonderful” →

How To Improve A Smart Motor? Make It Bigger!

November 7, 2020 by 25 Comments

Brushless motors can offer impressive torque-to-size ratios, and when combined with complex drive control and sensor feedback, exciting things become possible that expand the usual ideas of what motors can accomplish. For example, to use a DC motor in a robot leg, one might expect to need a gearbox, a motor driver, plus an encoder for position sensing. If smooth, organic motion is desired, some sort of compliant mechanical design would be involved as well. But motors like the IQ Vertiq 6806 offered by [IQ Motion Control] challenge those assumptions. By combining a high-torque brushless DC motor, advanced controller, and position sensing into an integrated device, things like improved drone performance and direct-drive robotic legs like those of the Mini Cheetah become possible.

IQ Vertiq 6806 brushless DC motor with integrated controller, driver, and position sensing.

First, the bad news: these are not cheap motors. The IQ Vertiq 6806 costs $399 USD each through the Crowd Supply pre-order ($1499 for four), but they aren’t overpriced for what they are. The cost compares favorably with other motors and controllers of the same class. A little further than halfway down the Crowd Supply page, [IQ Motion Control] makes a pretty good case for itself by comparing features with other solutions. Still, these are not likely to be anyone’s weekend impulse purchase.

So how do these smart motors work? They have two basic operating modes: Speed and Position, each of which requires different firmware, and which one to use depends on the intended application.

The “Speed” firmware is designed with driving propeller loads in mind, and works a lot like any other brushless DC motor with an ESC (electronic speed control) on something like a drone or other UAV. But while the unit can be given throttle or speed control signals like any other motor, it can also do things like accept commands in terms of thrust. In other words, an aircraft’s flight controller can communicate to motors directly in thrust units, instead of a speed control signal whose actual effect is subject to variances like motor voltage level.

The “Position” mode has the motor function like a servo with adjustable torque, which is perfect for direct drive applications like robotic legs. The position sensing also allows for a few neat tricks, like the ability to use the motors as inputs. Embedded below are two short videos showcasing both of these features, so check them out.

Continue reading “How To Improve A Smart Motor? Make It Bigger!” →

Cable Driven Robotic Joint

April 26, 2020 by 14 Comments

Even the oldest of mechanisms remain useful in modern technology. [Skyentific] has been messing with robotic joints for quite a while, and demonstrated an interesting way to use a pulley system in a robotic joint with quite a bit of mechanical advantage and zero backlash.

Inspired by the LIMS2-AMBIDEX robotic arm, the mechanism is effectively two counteracting sets of pulley, running of the same cable reel, with rollers allowing them to act around the bend of the joint. Increasing the mechanical advantage of the joint is simply a matter of adding pulleys and rollers. If this is difficult to envision, don’t work as [Skyentific] does an excellent job of explaining how the mechanism works using CAD models in the video below.

The mechanism is back drivable, which would allow it to be used for dynamic control using a motor with an encoder for position feedback. This could be a useful feature in walking robots that need to respond to dynamically changing terrain to stay upright, or in arms that need to push or pull without damaging anything. With properly tensioned cables, there is no backlash in the mechanism. Unfortunately cables can stretch over time, so it is something that needs to be considered when using this in a project.

Pulley systems have been with us for a very long time, and remain a very handy tool to have in your mechanical toolbox. A similar arrangement is used in the Da Vinci surgical robots to control their tiny manipulators. It would also be interesting to see this used in the already impressive robots of [James Bruton]. Continue reading “Cable Driven Robotic Joint” →

Humanoid Robot Has Joints That Inspire

October 20, 2019 by 8 Comments

One of the challenges with humanoid robots, besides keeping them upright, is finding compact combinations of actuators and joint mechanisms that allow for good range of smooth motion while still having good strength. To achieve that researchers from the IRIM Lab at Korea University of Technology and Education developed the LIMS2-AMBIDEX robotic humanoid upper body that uses a combination of brushless motors, pulleys and some very interesting joint mechanisms. (Video, embedded below.)

The wrist mechanism. Anyone willing to tackle a 3D printed version?

From shoulder to fingers, each arm has seven degrees of freedom which allows the robot to achieve some spectacularly smooth and realistic upper body motion. Except for the wrist rotation actuator, all the actuators are housed in the shoulders, and motion is transferred to the required joint through an array of cables and pulleys. This keeps the arm light and its inertia low, allowing the arms to move rapidly without breaking anything or toppling the entire robot.

The wrist and elbow mechanisms are especially interesting. The wrist emulates rolling contact between two spheres with only revolute joints. It also allows a drive shaft to pass down the centre of the mechanism and transfer rotating motion from one end to the other. The elbow is a rolling double jointed affair that allows true 180 degrees of rotation.

We have no idea why this took two years to end up in our YouTube feed, but we’re sure glad it finally did. Check out some of the demo videos after the break. Continue reading “Humanoid Robot Has Joints That Inspire” →

Moped Turn Signals, Now With More Cowbell

June 7, 2019 by 14 Comments

Cue up the [Christopher Walken] memes, it’s time for moped turn signals with more cowbell. Because moped turn signals with less cowbell are clearly the inferior among moped turn signals.

It seems that [Joel Creates] suffers from the same rhythm recognition disorder that we do. The slightest similarity between a rhythmic sound such as turn signals, and any song in our seemingly infinite intracranial playlist cues up that song for the rest of the day. [Joel] heard “(Don’t Fear) The Reaper” in his turn signals, and that naturally led to a need for More Cowbell. So with a car door lock actuator, a relay, an improvised clapper, and a lot of hot glue and cable ties, the front of his scooter is now adorned with a cowbell that’s synchronized to the turn signals. The video below shows that it’s of somewhat limited appeal in traffic, but at least [Joel’s dad] was tickled pink by it.

Kudos to [Joel] for marching to the beat of his own [Gene Frenkle] on this one. It may be a little weird, but not as weird as an Internet of Cowbells.

Continue reading “Moped Turn Signals, Now With More Cowbell” →

Flexible PCB Contest Round Up

April 15, 2019 by 19 Comments

The 2019 Hackaday Prize, which was announced last week, is very much on everyone’s mind, so much so that we’ve already gotten a great response with a lot of really promising early entries. As much as we love that, the Prize isn’t the only show in town, and we’d be remiss to not call attention to our other ongoing contest: The Flexible PCB Contest.

The idea of the Flexible PCB Contest is simple: design something that needs a flexible PCB. That’s it. Whether it’s a wearable, a sensor, or a mechanism that needs to transmit power and control between two or more moving elements, if a flexible PCB solves a problem, we want to know about it.

We’ve teamed up with Digi-Key for this contest, and 60 winners will receive free fabrication of three copies of their flexible PCB design, manufactured through the expertise of OSH Park. And here’s the beauty part: all you need is an idea! No prototype is necessary. Just come up with an idea and let us know about it. Maybe you have a full schematic, or just a simple Fritzing project. Heck, even a block diagram will do. Whatever your idea is for a flexible PCB project, we want to see it.

To get the creative juices going, here’s a look at a few of the current entries

The Flexible PCB Contest goes through May 29, so you’ve got plenty of time to get an idea together.

Save A Few Steps On Your Next Build With These Easy Linear Actuators

November 2, 2018 by 18 Comments

A lot of projects require linear motion, but not all of them require high-accuracy linear slides and expensive ball screws. When just a little shove for a door or the ability to pop something up out of an enclosure is all you need, finding just the right actuator can be a chore.

Unless someone has done the work for you, of course. That’s what [Ali] from PotentPrintables did with these 3D-printed linear actuators. It’s a simple rack-and-pinion design that’s suitable for light loads and comes in two sizes, supporting both the 9-g micro servos and the larger, more powerful version. Each design has a pinion that has to be glued to a servo horn, and a selection of rack lengths to suit your needs. The printed parts are nothing fancy, but seem to have material in the right places to bear the loads these actuators will encounter. [Ali] has included parts lists and build instructions in with the STL files, as well as sample Arduino code to get you started. The video below shows the actuators in action.

We’re heartened to learn that [Ali] was at least partly inspired to undertake this design by a previous Hackaday post. And we’re glad he decided to share his version; it might save us a few steps on our next build.

Continue reading “Save A Few Steps On Your Next Build With These Easy Linear Actuators” →