Thanks to the efforts of a couple of large companies, many devoted hobbyists, and some dystopian science fiction, robot dogs have firmly entered the zeitgeist of our “living in the future” world. The quadrupedal platform, with its agility and low center of gravity, is perfect for navigating in the real world, where the terrain is rarely even and unexpected obstacles are to be expected.
The robot dog has been successful enough that there are commercially available — if prohibitively priced — dogs on the market, doing everything from inspecting factory processes and off-shore oil platforms to dancing for their dinner. All the publicity around robot dogs has fueled a crush of DIY and open-source versions, so that hobbyists can take advantage of what the platform has to offer. And as a result, the design of these dogs has converged somewhat, with elements that provide a common design language for these electromechanical pets.
Afreez Gan has been exploring the robot dog space for a while now, and his MiniPupper is generating some interest. He’ll stop by the Hack Chat to talk about MiniPupper specifically and the quadruped platform in general. We’ll talk about what it takes to build your own robot dog, what you can do with one once you’ve built it, and how these bots can play a part in STEM education. Along the way, we’ll touch on ROS, lidar, machine vision with OpenCV, and pretty much anything involved in the care and feeding of your newest electronic pal.
Not long ago, Boston Dynamics’ Spot finally went on sale, meaning the dog-like robot can now be purchased online. Previously it was available only to be leased by early adopters willing to pay to see what the robot had to offer. Pricing was tucked behind an NDA, and Spot could be only leased and not actually purchased — until now.
From a hobbyist’s perspective, Spot’s price is of course eye-watering; the cost of the accessories even more so. It would be perfectly understandable to ask what good is a robotic dog and what makes it worth such a cost?
From an industrial equipment point of view, the cost is perhaps less shocking. Maybe it’s a reminder that from an industrial and commercial perspective, the price of a thing matters mainly in relation to what kind of benefits it can bring, and what kind of price or savings can be hung on that.
Personally, I am a fan of the real thing, but dogs aren’t an option for all. Plus, robotic dogs are easier to train and don’t pee on your couch. If you are looking to adopt a robotic companion, Stanford Pupper might be a good place to start. It’s a new open source project from the Stanford Robotics Student group, a group of robotic hackers from Stanford University. This simple robotic quadruped looks pretty simple to build, but also looks like a great into to four-legged robots.
This is the first version of the design, but it looks pretty complete, built around a carbon fiber and 3D printed frame. The carbon fiber parts have to be cut out on a router, but you can order them pre-cut here, and you might be able to adapt it to easier materials. The Pupper is driven by twelve servos powered from a 5200 mAh 2S LiPo battery and a custom PCB that distributes the power. That means it could run autonomously.
Getting a legged robot to stay upright, especially a quadruped or biped, can be a challenging undertaking. To experiment with different approaches, [James Bruton] built robot dog test platform and is playing with “dynamic compliant simulated springs“, or in other words, using the motors to act as though they were springs and dampers..
When robotic legs are kept stiff, they tend to reduce the stability of the platform due to the sudden erratic movements of the robot, especially on uneven surfaces. With a back drivable joint arrangement, [James] is using limited holding current on the motor, and the position of the motor shaft is monitored using an encoder. When a leg experiences a resisting force, with will have some “give” and then the motor will return it to it’s intended position more slowly. Using a IMU on top of the robot, it can detect when it start leaning to a side, and then temporarily soften the other side to balance the robot.
This is quite a common technique in legged robots, but [James] does an excellent job of explaining just how it works. He hopes to use the lessons learned from the test platform to improve or redesign his already impressive OpenDog.
Hackaday Editors Mike Szczys and Elliot Williams take a look at the latest hacks from the past week. We keep seeing awesome stuff and find ourselves wanting to buy cheap welders, thermal camera sensors, and CNC parts. There was a meeting of the dog-shaped robots at ICRA and at least one of them has super-fluid movements. We dish on 3D printed meat, locking up the smartphones, asynchronous C routines, and synchronized clocks.
Take a look at the links below if you want to follow along, and as always tell us what you think about this episode in the comments!
Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!
Every few months or so, a new video from Boston Dynamics will make the rounds on the Internet. This is their advertising, because unless the military starts buying mechanical mules, Boston Dynamics is going to be out of business pretty soon. You’ll see robots being kicked down the stairs, robots walking through doors, and robots acting like dogs. If a hundred or so highly skilled and highly educated roboticists, technologists, and other experts can put together a walking dog robot in a decade, obviously one person can cut through the cruft and build one in a basement. That’s what [Misha] is doing. It’s the Dizzy Wolf, a robotic wolf, or dog, or cat, we don’t actually know because there’s no fur (or head) yet. But it is interesting.
The key component for any quadruped robot is a high-torque, low-noise servo motor. This isn’t a regular ‘ol brushless motor, and for this application nine gram servos go in the trash. This means custom made motors, or DizzyMotors. You’re looking at a big brushless motor with a planetary gearset, all squished into something that could actually fit into the joint of a robotic wolf’s leg.
There’s a driver for these motors, strangely not called the DizzyDriver, that turns a BLDC into a direct drive servo motor. It is effectively a smart servo, that will move to a specific rotation, receive commands over RS-485, and write back the angular position. It also applies constant torque. Of course, there is a video of the DizzyMotor and servo driver below.
Building a robotic dog that will walk around the house is one of the hardest engineering challenges out there. You’ve got fairly crazy kinematics, you’ll need to think about the strength of the frame, control systems, and eventually how to fit everything in a compact design. This project is hitting all the marks, and we can’t wait to see the Dizzy Wolf do a backflip or chase a ball.