Deducing Stepper Motor Wiring

July 25, 2019 by Al Williams 12 Comments

There are a lot of fun projects you can do with stepper motors salvaged from old printers or disk drives. However, it isn’t always clear how to connect to some strange motor with no markings or schematics. [Corvetteguy50] has a video showing his trick for working out the connections easily, and you can see it below.

The basic idea is simple. Using a special jig, he connects an LED across two random pins and spins the motor. If the LED lights, you’ve found a coil. You just don’t know which coil, yet. You can also short two wires and note when you feel resistance when you spin the shaft.

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Getting Hackers Excited About Cable Robots

July 18, 2019 by Tom Nardi 22 Comments

Ever since he looked into them as a way to water and care for his plants, [Tom] has been fascinated with cable robots. These high-flying gadgets can move in three dimensions over huge areas, provided you’ve got the ability to string up the aforementioned cables. But despite their flexibility, there hasn’t been a whole lot of hobbyist level development with these unique systems.

With his entry into the 2019 Hackaday Prize, [Tom] is hoping to change that. He’s learned a lot by building his own cable robots, and now wants to take it to the next level. Ideally with collaboration from the community, if he can find other hackers looking to outfit their homes or workshops with their own miniature sky cranes.

So what can you do with a cable robot? In the video after the break, [Tom] shows one of his creations dutifully transporting beer cans across the room and stacking them into a pyramid. Admittedly this isn’t a particularly useful capability (unless you run a bar, perhaps), but it does show the speed and dexterity of the system even when crossing large distances. If you’ve ever wanted to play the home edition of “Automate the Freight”, this one’s for you.

The system uses a trio of 36 volt stepper motors powered by a homebrew SLA7078 driver that [Tom] designed himself. Each stepper turns a geared-down spindle to which a strong cable is attached. With some clever routing around the workspace, careful orchestration of these small winches can be used to move the point where all the cables meet in 3D space. All that’s left is mounting your gadget of choice to this central point, and away you go.

We’ve seen the concept used commercially, but as far as hobbyist projects go, the most activity we’ve seen in this space would have to be the various room sized 3D printers that have popped up over the years. It would be interesting to see what kind of interesting projects the community could come up with if they had something with a little more muscle.

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Robotic Dishwashers And Dishwashing As A Service

July 11, 2019 by Dan Maloney 53 Comments

There’s a story that goes back to the 1980s or so about an engineering professor who laid down a challenge to the students of his automation class: design a robot to perform the most mundane of household tasks — washing the dishes. The students divided up into groups, batted ideas around, and presented their designs. Every group came up with something impressive, all variations on a theme with cameras and sensors and articulated arms to move the plates around. The professor watched the presentations respectfully, and when they were done he got up and said, “Nice work. But didn’t any of you idiots realize you can buy a robot that does dishes for $300 from any Sears in the country?”

The story may be apocryphal, but it’s certainly plausible, and it’s definitely instructive. The cultural impression of robotics as a field has a lot of ballast on it, thanks to decades of training that leads us to believe that robots will always be at least partially anthropomorphic. At first it was science fiction giving us Robbie the Robot and C3PO; now that we’re living in the future, Boston Dynamics and the like are doing their best to give us an updated view of what robots must be.

But all this training to expect bots built in the image of humans or animals only covers a narrow range of use cases, and leaves behind the hundreds or thousands of other applications that could prove just as interesting. One use case that appears to be coming to market hearkens back to that professor’s dishwashing throwdown, and if manufacturers have their way, robotic dishwashers might well be a thing in the near future.

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Robot Harvesting Machine Is Tip Of The Agri-Tech Iceberg

July 9, 2019 by Pat Whetman 24 Comments

Harvesting delicate fruit and vegetables with robots is hard, and increasingly us humans no longer want to do these jobs. The pressure to find engineering solutions is intense and more and more machines of different shapes and sizes have recently been emerging in an attempt to alleviate the problem. Additionally, each crop is often quite different from one another and so, for example, a strawberry picking machine can not be used for harvesting lettuce.

A team from Cambridge university, UK, recently published the details of their lettuce picking machine, written in a nice easy-to-read style and packed full of useful practical information. Well worth a read!

The machine uses YOLO3 detection and classification networks to get localisation coordinates of the crop and then check if it’s ready for harvest, or diseased. A standard UR10 robotic arm then positions the harvesting mechanism over the lettuce, getting force feedback through the arm joints to detect when it hits the ground. A pneumatically actuated cutting blade then attempts to cut the lettuce at exactly the right height below the lettuce head in order to satisfy the very exacting requirements of the supermarkets.

Rather strangely, the main control hardware is just a standard laptop which handles 2 consumer grade USB cameras with overall combined detection and classification speeds of about 0.212 seconds. The software is ROS (Robot Operating System) with custom nodes written in Python by members of the team.

Although the machine is slow and under-powered, we were very impressed with the fact that it seemed to work quite well. This particular project has been ongoing for several years now and the machine rebuilt 16 times! These types of machines are currently (2019) very much in their infancy and we can expect to see many more attempts at cracking these difficult engineering tasks in the next few years.

We’ve covered some solutions before, including: Weedinator, an autonomous farming ‘bot, MoAgriS, an indoor farming rig, a laser-firing fish-lice remover, an Aussie farming robot, and of course the latest and greatest from FarmBot.

Video after the break:

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RC Trike Handles Great With Rear Steering

July 2, 2019 by Lewin Day 5 Comments

Small robotics builds with three wheels are plentiful. The most typical configuration is to have the two front wheels drive and turn the vehicle in a skid-steer configuration. The third wheel is often a simple caster. However, this isn’t the only way to go, and [markus.purtz] has put together a build that does things differently.

The build is a small, radio-controlled FPV trike. Instead of the usual skid-steer setup, the rear wheel is mounted on a pair of horizontal bearings which allows it to pivot left and right. A servo is used to control the rear wheel position, with a pair of tie rod ends used to connect the horn to the rear steering assembly. It’s not the only unconventional design choice, either – magnets are used to affix the top plate to the vehicle chassis, rather than screws or clips. For video, the user can mount either a small dedicated FPV camera, or a GoPro with the included mount.

Without any code or control details posted, we can’t be 100% sure how it all works. However, from the video, it appears that both front wheels are being driven at the same speed, with steering handled solely by the rear wheel. This is apparent when driving on a smooth surface, where the vehicle can be seen to slide when turning. While it’s unlikely this setup has many advantages over a simpler differential steering build with a caster, it does show that rear steering can be effective on its own.

It’s a build that shows off the benefits of using proper bearings and mechanical parts in a design. With today’s online marketplaces, it’s never been easier to find what you need. Parts are on Thingiverse for those interested in replicating the design. Meanwhile little FPV bots remain popular, and we’re sure we’ll continue to see them coming in. Video after the break.

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Fish Hooks Embedded In Robot Toes Make Them Climb Like Cockroaches

June 28, 2019 by Pat Whetman 5 Comments

Take a dozen or so fish hooks, progressively embed them in plastic with a 3D printer and attach them to the feet of your hexapod and you’ve got a giant cockroach!

A team of researchers at Carnagie Mellon University came up with this ingenious hack which can easily be copied by anybody with a hexpod and a 3D printer. Here you can see the hooks embedded into the ends of a leg. This ‘Microspine technology’ enables their T-RHex robot to climb up walls at a slightly under-whelming 55 degrees, but also grants the ability to cling on severe overhangs.

Our interpretation of these results is that the robot needs to release and place each foot in a much more controlled manner to stop it from falling backwards. But researchers do have plans to help improve on that behavior in the near future.

Sensing and Closed Loop Control: As of now, T-RHex moves with an entirely open-loop, scripted gait. We believe that performance can be improved by adding torque sensing to the leg and tail actuators, which would allow the robot to adapt to large-scale surface irregularities in the wall, detect leg slip before catastrophic detachment,and automatically use the tail to balance during wall climbs.This design path would require a platform overhaul, but offers a promising controls-based solution to the shortcomings of our gait design.

No doubt we will all now want to build cockroaches that will out perform the T-RHex. Embedding fish hooks into plastic is done one at a time. During fabrication, the printer is stopped and a hook is carefully laid down by human hand. The printer is turned on once again and another layer of plastic laid down to fully encapsulate the hook. Repeat again and again!

Your robot would need the aforementioned sensing and closed loop control and also the ‘normal’ array of sensors and cameras to enable autonomy with the ability to assess the terrain ahead. Good luck, and don’t forget to post about your projects (check out Hackaday.io if you need somewhere to do this) and tip us off about it! We’ve seen plenty of, sometimes terrifying, hexapod projects, but watch out that the project budget does not get totally out of control (more to be said about this in the future).

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A Better Motor For Chickenwalkers

June 24, 2019 by Brian Benchoff 27 Comments

The last decade or so has seen remarkable advances in motor technology for robotics and hobby applications. We’re no longer stuck with crappy brushed motors, and now we have fancy (and cheap!) stepper motors, brushless motors for drones, and servo motors. This has led to some incredible achievements; drones are only barely possible with brushed motors, and you can’t build a robot without encoders.

For his entry into the Hackaday Prize, [Gabrael Levine] is taking on one of the hardest robotics challenges around: the bipedal robot. It’s a chickenwalker, or an AT-ST; either way, you need a lot of power in a very small space, and that’s where the OpenTorque Actuator comes in. It’s a quasi-direct-drive motor that was originally pioneered by the MIT Biomimetics Lab.

The key feature of the OpenTorque Actuator is using a big brushless motor, a rotation encoder, and a small, 8:1 planetary gear set. This allows the motor to be backdrivable, capable of force-sensing and open-loop control, and because this actuator is 3D printed, it’s really cheap to produce.

But a motor without a chassis is nothing, and that’s where the Blackbird Bipedal Robot comes in. In keeping with best practices of robotic design, the kinematics are first being tested in simulation, with the mechanical build happening in parallel. That means there’s some great videos of this chickenwalker strutting around (available below), and so far, everything looks great. This bipedal robot can turn, walk, yaw, and work is continuing on the efforts to get this bird-legged bot to stand still.