Arm(h)ando
This exo-arm is designed to help people who have disabilities in the upper limbs. Possible uses would be to assist with physiotherapy exercises or to provide daily assistence for those with limited strength.
The structure of the arm is based on mechanical parts, respectively an electric actuator, an aluminum support system and a support base for the arm made from PVC pipes of various sizes.
The motor used is a linear actuator, that is an electric motor that under stimulation moves a shaft back and forth in relation to the polarity supplied, the current of use is about 2 Amps at 12 Volts.
The horizontal movement is converted to rotary using the person's elbow as a pivot and a system of belts and pins. There are 2/3 straps, one that adjusts the PVC tube that adheres to the forearm. The PVC tubes are 100 mm in diameter.
Supplies
Tools:
- 3d printer
- Screwdrivers
- 6mm, 7mm and 8mm wrenches
- Hot glue gun
- Soldering iron
- Electrical tape
- Drill
- Handsaw
Material:
- One PWC tube (10 cm of diameter);
- Four 3d printed supported pieces (the file for printing them is linked below);
- 16 bolts the size is not important it depends on size of the hole that you make;
- 10 bolts size 10 for the lateral supported pieces that have to be printed;
- Two pillows (15cmX15cm);
- Two rectangular pieces of aluminium (height: it depend on the size of the arm/ width: 5 cm)
- Two rectangular pieces of aluminium (height: 11 cm/ width: 2.5 cm)
- Two L brackets (1.5 cm wide);
- Sponge
- Straps
- Velcro strips
- Shoulder pad
- Plastic box
- PWMvoltage regulator
- LT100-1-100 linear actuator
- 12 volt lead acid battery
- 2-way switch
- Wires
- 3d Switch box
- Zipties
- Fanny pack
Start From Zero
We disassembled the old version of the project, to see how it was built and to see if there were any materials we could reuse. We decided to keep the linear actuator, the aluminium pieces that attach the linear actuator, and some of the screws.
Design
We then started the design process. We chose to use 3d printed pieces for the side structure, a PVC pipe for the main body, straps with velcro to keep the arm still, and to keep basically the same lower structure from the old version.
Printing
We designed the 3d printed pieces on an online CAD called Onshape and gave the files to the printer. Meanwhile, we cut the 10 cm diameter tube in half in order to create two halves. Once the pieces were printed, we drilled holes in the half tubes and secured the pieces with 10 mm bolts.
Assembling
We connected the lower metal structure along with the linear actuator. The metal structure is fixed with bolts, the linear actuator with a single screw and zipties. We also attached the pillows to the inside using velcro to make the arm more comfortable to wear and straps to keep it in place.
Electronics
We started working on the electronics: the battery is connected to the PWM controller, which then is connected to the switch and the motor. We then routed the cables in a sleeve mounted on the right side of the arm.