When we last left [Wes] amidst the torn-open guts of his Logg Dogg logging robot, he had managed to revitalize the engine and dug into the hydraulics, but one big obstacle remained: the lack of the remote control unit. In today’s installment of the Logg Dogg series, [Wes] summarizes weeks of agony over creating a custom circuit based around a microcontroller, a joystick and a lot of relays and other bits and pieces to drive the solenoids inside the logging machine that control the hydraulics.
Most of the struggle was actually with the firmware, as it had to not only control the usual on/off solenoids, but also a number of proportional solenoid valves which control things like the track speed by varying the hydraulic flow to the final drives.
This requires a PWM signal, which [Wes] generated using two MOSFETs in a closed-feedback system, probably because open loop controls with multi-ton hydraulic machinery are not the kind of excitement most people look forward to.
Ultimately he did get it sorted, and was able to take the Logg Dogg for its first walk since being rescued from a barn, which both parties seemed to rather enjoy. The background details of this machine and the project can be found in our first coverage.
We’re looking anxiously forward to the next episode, where the controller goes wireless and the sketchiness gets dialed down some more.
With the popularity of robot dogs, many people have gotten on the bandwagon and tried building DIY versions. Most of them end up attaching a gearbox to an off-the-shelf brushless motor and call it a day. Not everyone goes that way, though, which is why this internal cycloidal drive actuator caught our eye.
Taking design cues from the MIT Mini Cheetah, [Aaed Musa] approached his actuator from the inside out, literally. His 3D printed cycloidal gearbox is designed to fit inside the stator of a BLDC motor. And not just any BLDC motor, but one built mostly from scratch using a hand-wound — and unwound, and wound again — stator along with a rotor that started as a printed part but was eventually machined from steel. Apart from its fixed ring, the cycloidal drive was mostly 3D printed, with everything fitting nicely inside the stator.
The video below shows the design and assembly process as well as testing of the finished drive. It seems to do really well with speed and positional accuracy, and it delivers a substantial amount of torque. Maybe a little too much, though; testing it with a heavy weight on the end of an arm got the stator coils hot enough to warp the printed parts within. But no matter; this was only a prototype after all. [Aaed] says improvements are in the works, including replacing all the plastic parts with metal ones.
If you haven’t seen a chain printer in action before, definitely check one out. They’re big, loud, and sound a bit like a turbine when they spool up. The type chains on these printers never stops moving. This means the printer has to know exactly where a particular letter is before launching one of 66 hammers at it. If the timing is off, parts will fly. To the average computer user, they’re quite intimidating.
Thankfully [Usagi’s] printer was in pretty good shape. When he flipped the big power switch, there was plenty of strange noises, culminating in the test pattern of dollar signs. Probably an early reminder to customers that they needed to order more print supplies.
Although there’s been considerable excitement over the past half century of a Jetsons-like robotic future, outside of a few niche uses of our day-to-day lives there hasn’t been much in the way of robotic assistants coming to ease our physical household workloads. Sure, robots exist in manufacturing and other industrial settings, but the vast majority of us won’t see a robotic revolution unless we make it for ourselves. To that end, [Jim] has begun construction of a robot that can at least mow his lawn and eventually plow his driveway, among other potential tasks.
The robot, called the Lawny Five, is a tracked vehicle currently under remote control but with a planned autonomous capability. The frame includes a set of caster wheels at the front to take advantage of the differential steering of the tracks, and between everything is where the mower, plow, or other tool can sit. The attachment system is based on a 2″ receiver hitch, allowing the robot to eventually change tools at will while still preserving the usefulness of the tools in their original state. The robotic platform has been tested with the mower on a wet lawn with a 20° slope and showed no signs of struggle (and didn’t damage the grass) so it’s ready to take on more challenging tasks now as well.
With the core of the build out of the way, [Jim] is well on his way to a robotic lawnmower and potentially even an autonomous one, not to mention one with interchangeable tools that he hopes will be put to work in other ways like parking his boat in a small space by his house. For those maintaining a piece of land a little more involved than suburban turfgrass, there are other robotic platforms capable of helping out farmers with things like planting, watering, and weeding.
On autonomous robots, the most difficult challenges usually lie in the software and electronic realms, but the mechanics can also be very time consuming. To help address this challenge, [Nikodem Bartnik] is working on the Open Robotic Platform (ORP), a modular robotics chassis system designed to make prototyping as easy and affordable as possible. Video after the break.
The ORP is governed by a set of design rules to maintain interchangeability. Most of the design rules are very open, but the cornerstone of ORP is its standardized mounting plates featuring a 20 mm grid pattern of 3.5 mm mounting holes. These plates can be stacked using connecting rods, creating a versatile foundation upon which various components can be mounted.
[Nikodem] is on a mission to create and collect an entire library of these modular components. From custom 3D-printed holders that accommodate sensors, motors, wheels and dev boards to homemade PCBs that snap directly onto the chassis, everything to get your robot rolling as soon as possible. While manufacturing methods and materials are not limited, 3D printing and laser cutting will likely be the most popular manufacturing technologies for making your own parts.
The robot is the work of doctoral students at ETH Zurich, working with the Swiss Federal Institute for Forest, Snow, and Landscape research. The design is optimized for navigating the canopy of the rainforest, where a lot of the action is. Traditional methods of locomotion are largely useless up high in the trees, so another method was needed.
The avocado robot is instead tethered to a cable which is affixed to a high branch on a tree, or even potentially a drone flying above. The robot then uses a winch to move up and down as needed. A pair of ducted fans built into the body provide the thrust necessary to rotate and pivot around branches or other obstacles as it descends. It also packs a camera onboard to help it navigate the environment autonomously.
Braille is a method of physical writing used to allow humans to read by touch — most commonly used as a substitute for printed text by those who may be visually impaired. Both displaying Braille and reading it is difficult to do with machines, but there has been a development in the latter area. A research team has trained a robot to read Braille at a speed far exceeding humans.
The robot was developed by a team at the University of Cambridge. Rather than trying to read Braille by touch, it instead uses a camera and an image recognition algorithm to do the job. Their solution is a bit ironic in a way, given the purpose Braille was created for. The robot can quickly sweep across a Braille display, working at a rate of up to 315 words per minute at 87% accuracy. That’s roughly twice as fast as a human reading Braille, with a similar level of accuracy. Some nifty de-blurring algorithms were needed to achieve this speed from the camera’s video feed.