hiwonder xarm – ROBOFIESTA

August 5, 2024August 14, 2024

MechArm 270 Pi- Learning Curve

Some entry-level robots come with an easy-to-use programming interface that allows a user to start making motion sequences right out of the box. It would be remiss of me to say that was my experience with the Mecharm 270 Pi. The robot has some nice features, but it doesn’t have an intuitive slider or drag UI that a beginner could use to quickly program a motion sequence.

My Mecharm 270 Pi came with an Ubuntu OS version 18.04 (desktop pictured above). I was unable to get any form of ROS interface to work with that system, and finally switched to Ubuntu 20.04. This requires a re-burn of the the Pi microSD card.

On the Ubuntu 20.04 update, I could get an RVIZ panel opened using ROS2. There is a basic slider control which will move the robot, though I found it unpredictable.

After experimenting for a while trying to program using the ROS2 interface, I gave up and went back to the myBlockly option which comes pre-installed. It does allow you to program simple motion sequences using “Set Angle” and “Sleep” function blocks, but if there’s a way to program acceleration / deceleration or a “wait” command, I was unable to find it.

myBlockly has logical commands which allow for use of IO and peripherals, but my goal was just smooth & repeatable motion before going any further. I did eventually learn how to use the positioning control to automatically send joint values to the command blocks, which made general positioning easier, but the process requires several keystrokes for each new position and takes a while to get used to.

With the Elephant Robotics gripper installed on the MechArm, I wanted to program a short sequence of the robot playing a xylophone. It seemed like a simple task which didn’t require fine motion. Unfortunately, the gripper doesn’t close all the way, and the gripper force is very weak. It wouldn’t hold a small wooden xylophone mallet steady, even during slow motions. I printed off a simple square grip, in the hopes that it would increase the stability of grip on the mallet, but it didn’t work very well. This is the result of several hours of work:

LInk to video on YouTube: Mecharm 270 Pi – Learning Curve

During this experimentation, I wanted to try using Python to control the robot instead of myBlockly. My favorite lighter IDE is Thonny, which can be downloaded at Thonny.org

I installed Thonny on the Pi desktop. If you haven’t programmed in a Python environment before, there are many resources to help you get started at Python.org

One frustration of the myBlockly app- while it will show you the python equivalent of your myBlockly commands (just click the Python tab), there isn’t an easy way to copy the python code.

Insofar as I could tell, it would copy one time, then something got messed up in the clipboard and it wouldn’t copy again. Not sure if this is an Ubuntu thing, or a myBlockly thing, but it was annoying.

Trying to play to the Mecharm 270’s strengths, I decided to try a simple sequence with a toy the gripper would be able to pick up without difficulty. This sequence was done using Thonny to run the robot:

Link to video on Youtube: Mecharm 270 Pi Grommit Grab

In the next blog, the xylophone playing improves…

Product Links

Elephant Robotics MechArm270 Pi

MechArm 270 Gripper

Mecharm 270 Robot Stage

SAMSUNG PRO Plus microSD Card

To get started with your Mecharm 270 Pi, you’ll need a keyboard, mouse, and monitor to plug in.

This is a great package deal for all 3:
https://amzn.to/4eSRZaJ

Separately:

compact USB keyboard
https://amzn.to/3We57jx

Basic ergonomic USB mouse
https://amzn.to/4bF5hF9

Good quality HDMI monitor
https://amzn.to/3LiNMQ4

DON’T FORGET THE MONITOR CABLE!
The Mecharm 270 Pi monitor port is a micro-HDMI. With an HDMI monitor, you’ll need an HDMI to micro-HDMI cable:
https://amzn.to/3WdGYcK

I use an ergonomic mouse pad which reduces the strain on your wrist:
Ergonomic Mouse Pad with Wrist Support
https://amzn.to/4eXRAnn

Printing Supplies:

Green Printer Filament:
Gizmo Dorks 3mm ABS Green

Black Printer Filament:
Gizmo Dorks 3mm ABS Black

Blue Printer Filament:
Gizmo Dorks 3mm ABS Blue

Brown Printer Filament:
Gizmo Dorks 3mm ABS Brown

Clear Printer Filament:
Gizmo Dorks 3mm ABS Clear

Red Printer Filament:
Gizmo Dorks 3mm ABS Red

3D Printer

We highly recommend the Flashforge line of 3D printers for printing your robotic EOAT and staging parts:

FLASHFORGE 3D Printer Guider II Large Size Intelligent Industrial Grade 3D Printer

FLASHFORGE Guider IIS 3D Printer Auto Leveling with High Temperature Nozzle

FLASHFORGE Adventurer 5M Pro 3D Printer with 1 Click Auto Printing System

FLASHFORGE Adventurer 5M 3D Printer with Fully Auto Leveling

FLASHFORGE 3D Printer Adventurer Series with Auto Leveling with Quick Removable Nozzle

Disclaimer: As a participant in the Amazon Affiliate program, we earn a small commission if you make a purchase through one of these links, at no additional cost to you.

April 2, 2023

The Hurling Video

Playing around with TCP settings on the Mecademic one day, and this morphed into the thought that it would be fun to have a robotic sporting match to showcase this very useful function.

Basketball was out (couldn’t figure out how to dribble the ball repeatably), and soccer didn’t seem practical given the lack of legs in the participants. Irish Hurling came to mind while contemplating ice hockey (the hurley and the hockey stick have vaguely similar shapes).

Ok, so we have the sport identified, now what about props… The first time I watched a hurling match, I was sure the hurleys must have a scoop-type feature to keep the sliotar in place as the players raced up and down the field. The face of the hurley is in fact NOT concave, it’s the skill of the hurlers (camogie-ers?) and the slightly raised stitching on the sliotar that keeps it in place. It’s as if the players have their own TCP functions to keep the center point firmly in the middle of the flattened end of the hurley!

Here’s a great YouTube video from GAA MAN with players demonstrating their hurling skills: https://youtu.be/44Gi2IarBiI

Amazingly enough, miniature hurleys and sliotars aren’t for sale on Amazon or Etsy (and I did a lot of searching). Looking at some online images, I designed a model hurley in AutoDesk 360 that at least keeps the shape, if not proportions, of the real thing. Here’s a great intro to AutoDesk Fusion 360 if you’re not already a user: AutoDesk Fusion 360

I ended up printing the hurleys both ways; in the video, the Mecademic’s hurley is flat while Neds and the xArm’s have one flat, and one concave side.

Autodesk 360 image of printable hurley, ~ 6" overall length

2 printed hurleys on the model playing field

The hurley strapping is electrical tape.

OK, now for the sliotar… I spent an inordinate amount of time trying to stitch a tiny canvas ball, but the material shredded in places. Next, I cut up an old pair of leather gloves and tried sewing a leather one using a tiny baseball pattern. It turned out more square than spherical:

Result of attempt to sew tiny leather sliotar

Ned actually liked this one best; it didn’t roll at all, so was easier to hold on the hurley.

The final sliotar was a design based on some historical sliotar images on the National Museum of Ireland’s website. They were made of cow or horse hair. A ball made of coarse twine seemed about as close as I was going to get; once the glue set, it was hard and rolled reasonably well.

The goal was cobbled together using twine and mesh netting on a wooden frame.

Programming the winning goal motion on the Mecademic was a challenge; suffice to say, acceleration settings were key. Once the proper settings were found, though, Mike made the goal in ~ 75% of the shots. Here’s the final program used in the video:

meca-hurley-final Download

You can watch the Robofiesta hurling video here.

January 29, 2023March 11, 2023

Robot Valentine

View the video on Youtube

two hearts (with convenient easy-grip handles)

Ned has a new friend! The HiWonder Xarm is a fun little educational robot which you can buy assembled or in a kit. We thought it would be fun to see if the Xarm is repeatable enough to perform in a video alongside our Niryo Ned. It did very well for the price; at one stage, I needed to reteach some points that “wandered” for some reason but other than that it’s a great little robot. Note, the Xarm is really more of a 5-axis than 6-axis robot; the 6th axis is the gripper jaws, which does limit some of the positioning but Ned was able to work around this.

For props, I designed a simple heart shape with a grip and printed it on our FlashForge Creator Pro. Resized for the smaller heart, repeat. Slicing done on Simplify3d.

In any setup where pre-stage is the locating method, it’s important to know where your robots & parts are. I used a couple of plastic grids which are inexpensive and reusable; they’re sold as quilting accessories.

We repeated the exchanging-of-valentines action over two dozen times; occasionally it didn’t work out (there was some variability where Ned put down the small heart, and occasionally the pencil stuck in his gripper jaws), but overall I was really happy with the sequence. The video featured on RoboFiesta’s Youtube channel was shot on a Samsung Galaxy S21 Ultra 5G, which has awesome media production capabilities. Edited on Adobe’s Premier Pro.