A DIY self-balancing robot

3D-Printed Self-Balancing Robot Brings Control Theory To Life

Stabilizing an inverted pendulum is a classic problem in control theory, and if you’ve ever taken a control systems class you might remember seeing pages full of differential equations and bode diagrams just to describe its basic operation. Although this might make such a system seem terribly complicated, actually implementing all of that theory doesn’t have to be difficult at all, as [Limenitis Reducta] demonstrates in his latest project. All you need is a 3D printer, some basic electronic skills and knowledge of Python.

The components needed are a body, two wheels, motors to drive those wheels and some electronics. [Limenitis] demonstrates the design process in the video below (in Turkish, with English subtitles available) in which he draws the entire system in Fusion 360 and then proceeds to manufacture it. The body and wheels are 3D-printed, with rubber bands providing some traction to the wheels which would otherwise have difficulty on slippery surfaces.

A PCB driving two stepper motors
The PCB has just a few components, with most of the complexity handled by plug-in modules.

Two stepper motors drive the wheels, controlled by a DRV8825 motor driver, while an MPU-9250 accelerometer and gyroscope unit measures the angle and acceleration of the system. The loop is closed by a Raspberry Pi Pico that implements a PID controller: another control theory classic, in which the proportional, integral and derivative parameters are tuned to adapt the control loop to the physical system in question. External inputs can be provided through a Bluetooth connection, which makes it possible to control the robot from a PC or smartphone and guide it around your living room.

All design files and software are available on [Limenitis]’s GitHub page, and make for an excellent starting point if you want to put some of that control theory into practice. Self-balancing robots are a favourite among robotics hackers, so there’s no shortage of examples if you need some more inspiration before making your own: you can build them from off-the-shelf parts, from bits of wood, or even from a solderless breadboard.

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Homebrew Biped Bot Shows Off Some Impressive Moves

We’ve seen enough DIY robotic platforms here on Hackaday to know that most of them take the literal and figurative path of least resistance. That is, they tend to be some type of wheeled rover. But of course, there are plenty of other forms of locomotion, should you want to take on something a bit more challenging.

This biped robot from [Tast’s Robots] is a perfect example. While it’s still technically wheeled, its self-balancing nature makes things quite a bit more complex. It doesn’t just stand upright either, it also has a unique ability to crouch down by rotating its motorized knees and hips. As demonstrated in the video below, it can even navigate relatively uneven terrain — pulling off such a smooth transition between hardwood and carpet is no easy feat for a self-balancing bot like this.

But the best part? It isn’t just fully open source, it’s also designed to be built with only the tools and capabilities available to the average home gamer. That means 3D printed components, wooden dowels, and RC car parts. Even the power supply, a Ryobi 18 V tool battery, is easy to source and relatively hacker friendly.

Just as impressive as the hardware is the suite of software packages developed to handle things like balancing, locomotion, and reverse kinematics. Each one is maintained and documented as their own individual Apache-licensed projects, making them far easier to utilize than they would be if it was all implemented as one monolithic system.

If you really want to ditch the wheels, we’ve seen a few biped walkers in the past. But frankly, none of them can compare to the capabilities and scope of this project.

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Unique Strandbeest Stands Tall With Line Of Legs

Multiple rows of intricately articulated legs are the defining characteristic of the Strandbeest, but [James Bruton] wondered if he could reduce that down to a single row using the same principles at work in a self-balancing two wheeled robot. While it’s perhaps a bit early to call his experiments a complete success, the first tentative steps taken by his (relatively) svelte Strandbeest certainly look promising.

Initially the robot only had two pairs of legs, but in testing [James] found this arrangement to be a bit unstable. By bringing the total count to four legs per side and improving the counterweight arrangement, the bot has been able to walk the length of the workshop. Unfortunately, an issue with the leg design seems to be preventing the Strandbeest from taking any backward steps.

Normally this wouldn’t be that big of a problem, but in this case it’s keeping the Strandbeest from being able to self-balance while standing still. In other words, the robot needs to keep moving forward or it will fall over. Still, [James] thinks the idea has promise and wants to continue experimenting with the bot in a larger area.

Specifically, he wants to see if the dual-motor robot can turn by varying the speed the two sets of legs are running at. If it can walk in a tight enough circle, it could keep right on marching until the power runs down. Sounds more than a little nightmarish to us, but we’d still like to see it.

Reader’s may recall [James] from this other another robotic projects, such as the phenomenal OpenDog. We don’t know where his obsession of legged robots comes from, but we certainly aren’t complaining.

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Sonic The Self-Balancing Robot: Face-Plants And The Challenges Of Sensor Integration

Watching a child learn to run is a joyous, but sometimes painful experience. It seems the same is true for [James Bruton]’s impressive Sonic the Self-Balancing robot, even with bendable knees and force sensitive legs.

We covered the mechanical side of the project recently, and now [James] has added the electronics to turn it into a truly impressive working robot (videos after the break). Getting it to this point was not without challenges, but fortunately he is sharing the experience with us, wipe-outs and all. The knees of this robot are actuated using a pair of motors with ball screws, which are not back drivable. This means that external sensors are needed to allow the motors to actively respond to inputs, which in this case are load cells in the legs and an MPU6050 IMU for balancing. The main control board is a Teensy 3.6, with an NRF24 module providing remote control.

[James] wanted the robot to be able to lean into turns and handle uneven surfaces (small ramps) without tipping or falling over. The leaning part was fairly simple (for him), but the sensor integration for uneven surfaces turned out to be a real challenge, and required multiple iterations to get working. The first approach was to move the robot in the direction of the tipping motion to absorb it, and then return to level. However, this could cause it to tip over slightly larger ramps. When trying to keep the robot level while going over a ramp with one leg, it would go into wild side-to-side oscillations as it drops back to level ground. This was corrected by using the load cells to dampen the motion.

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Sonic The Hedgehog Self-Balancing Robot Can Bend At The Knees

Building your own self-balancing robot is a rite of passage for anyone getting into the field of robotics. Master of robots, [James Bruton] has been there, done that, and collected a few T-shirts. Now he’s building a large Sonic the Hedgehog self balancing robot that can bend at the knees and hip, allowing it to lean while turning and handle uneven terrain. Check out the first video embedded after the break.

Standing about 1 m tall, the robot is inspired by Boston Dynamic’s box handling bot, Handle. It’s “skeleton” consists of 20×20 aluminium extrusions, bolted together using a bunch of 3D printed fittings in the signature blue and red of Sonic. The wheels and tyres are also 3D printed, and driven by brushless motor via a toothed belt. The knee/hip mechanism is actuated using a ball screw, also driven by a brushless motor.

[James] intends to implement an active shock absorption system into the leg mechanism, using the same technique he tried on his OpenDog robot. It works by bolting a load cell onto one of the leg extrusion to sense when it flexes under load, and then actuating the knee mechanism to absorb the force. His first version of the system on OpenDog used PWM signals to send the load cell data to the main controller, but the motors on the legs induced enough noise in the signal wires to make it unusable. He has since started experimenting with the CAN bus protocol, which was specifically designed to work reliably in noisy systems like modern automobiles. If he gets it working on the two legs of this Sonic robot, he plans to also implement it on the quadruped OpenDog.

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Augmented Arthropod Gets A Self-Balancing Ride

There are many people who find being around insects uncomfortable. This is understandable, and only likely to get worse as technology gives these multi-legged critters augmented bodies to roam around with. [tech_support], for one, welcomes our new arthropod overlords, and has even built them a sweet new ride to get around in.

The build follows the usual hallmarks of a self-balancing bot, with a couple of interesting twists. There’s twin brushed motors for drive, an an Arduino Uno running the show. Instead of the more usual pedestrian IMUs however, this rig employs the Bosch BNO055 Absolute Orientation Sensor. This combines a magnetometer, gyroscope, and accelerometer all on a single die, and handles all the complicated sensor fusion maths onboard. This allows it to output simpler and more readily usable orientation data.

The real party piece is even more interesting, however. Rather than radio control or a line following algorithm, this self-balancer instead gets its very own insect pilot. The insect is placed in a small chamber with ultrasonic sensors used to determine its position. The insect may then control the movement of the bot by moving around this chamber itself. The team have even developed a variety of codes to dial in the sensor system for different types of insect.

It’s not the first time we’ve seen insects augmented with robotic hardware, and we doubt it will be the last. If you’re working on a mad science project of your own, drop us a line. Video after the break.

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Balancing Robots From Off-The-Shelf Parts

In this day and age, we are truly blessed as far as the electronics hobby is concerned. Advanced modules such as gyros and motor controllers are readily available, not just as individual parts, but as pre-soldered modules that can be wired together with a minimum of fuss and at low cost. This simple balancing robot is a great example of what can be done with such parts (Google Translate link).

The robot has an ESP32 running the show, which provides both the processing power required, as well as the WiFi interface used to control the ‘bot from a smartphone. This is achieved using an app from JJRobots, an open-source robotics teaching resource. Stepper motors are controlled by DRV8825 modules sourced from amazon, and an MPU6050 gyro rounds out the major components. Naturally, source code is available on GitHub for your reading pleasure.

It’s remarkable that in this day and age, it’s possible to build such a project with little to no soldering required at all. With a credit card and a healthy supply of patch leads, it’s possible to whip up complex digital projects quite quickly. We’ve seen a similar approach before, too. Video after the break.

[Thanks to Baldpower for the tip!]
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