For this week I explore jamming, milling, suction cup, gripping (with sensors). I also made improvements on the mechanical mechanism for robotic body, attaching and detaching modules and pan the tilt platform.
Jamming was very easy to do, all you need is
- Latex Balloons
- Vacuum Pump
- Long Air Tubing
- Coffee Filter (optional)
- Dry and used coffee grounds
- Something to hold the Balloons (I used the outside of the Suction Hooks)
I used the long end of the spoon to fill the balloon with dry coffee grounds (fine and coarse grounds). I used the cap for the suction hook to hold my balloon, there is a small hole at the top that you can thread the open end of the balloon.
I connected the balloon with a long tube, and seal the connection between the ballon and the tube with electrical tape. It’s probably a good idea to cap the tube with a coffee filter before sealing the connection so that the coffee grounds won’t get into the motor. I did not have the filter at the time, but the long tube serve as the buffer.
Brushless Motor with end mill as shaft: Tricky Business
The major challenge in this project is to replaced the motor shaft with an end mill. I tried the motor shaft coupler but it make the shaft too long and runs off center at high speed.
It’s a good thing that Sam stopped me while I was about to jam the end mill into the motor. I might have damaged the bearing on the inside. Sam suggested to sand down the end mill shaft until it fit into the motor. I tried this three times but end up either damaging the end mill or over sanding the end mill shaft… this is a very tricky business.
Conclusion: It would be very helpful to have a tool kit to change the motor shaft. The method that I am using has a high failure rate, plus it is hard to source the shaft with the right diameter.
I did not make the prototype for this, I am saving this for later. The idea was to use the robotic arm to push against an object with the suction cup to pick up items with a flat surface, to release the object, the solenoid controlled gas valve would let the air into the suction cup to release the object.
Robotic Gripper with sensors
I made a robotic gripper in the previous project, but the gripper does not know how much force to apply and when to stop the servo to prevent gear stripping or overload. In the version 2 of the gripper, I added 2 “touch sensor“ (momentary switch) to sense the size of the object.
Once the program detects that the momentary switches has been triggered, the servo then pushes in to grnabthe object tighter then turns off the servo power. I could also have the servo keep it’s stopping position with the power on.
The next step would be adding the Parallel gripping plates with FSR or momentary switches are sensor.
New Robotic Body Design: 4″ PVC Pipe
- I decided to used 4inch PVC pipe for my modular robot for the following reasons.
- Cheap: $20 for 10 ft.
- Various length / Various robotic arm length / Cut to size
- Smooth finish
The PVC pipe could be lighter if we trim the wall or drill patterns on it.
By designing all the connectors, tool heads, grabbers, pan and tilt modules to fit 4 inch diameter, I can quickly assemble a custom robot.
For the next generation of the modular robot, I could add a motor with off center weight in the middle to move the module to meet another module. This way, it becomes a self assembling robot.
New Robotic Body Design:attaching and detaching mechanisms
By making the tool heads the same size with the self attaching and detaching mechanisms, the robot can then switch out tool head by itself.
The new self detaching feature allows the snapping mechanisms to self detach. The servo can spin one way to lock and the other way to unlock itself. The pogo pin feature might have to change, because it might not be able to deliver enough current for milling or other operations.
New Robotic Body Design: 180 Rotation
The new rotation base design includes bearings for heavier load and smoother rotation. The through holes allows the wires to pass through but moves with the platform.
New Robotic Body Design: Tilt
The new tilting mechanisms fits the 4 inch PVC pipe. This is not the final design, it still requires some tweaking.