Introduction: Handi-Hand

Picture of Handi-Hand

Being able to feed yourself is something most people take for granted, and is a liberty many people do not have in spite of a disability. The Handi-Hand was developed to return that liberty to those who lack it. The Handi-Hand is a dead-simple robotic arm that is controlled by the user to move food from a bowl to the user’s mouth. Two steppers control the arm: one that rotates the base, and the other that rotates the utensil attachment. Currently the control input method is tailored to a handicapped person who has lost his arms but can control his feet. Therefore the two motors are controlled by four footswitches (two per motor). The switches and motors are connected to an Arduino microcontroller with a motor shield attached to it for interfacing with the steppers. The Handi-Hand allows handicapped individuals to regain the ability to feed themselves thereby increasing their self-esteem, easing the job of caretakers, and increasing productivity in the home and hospital environment.

Parts List:

· 1 x Arduino Microcontroller

· 1 x Arduino Stepper Shield

· 1 x 2" PVC Elbow/Tubing

· 1 x 2'x2' 3/4" Plywood

· 2 x Stepper Motors

· 1 x Belt Drive Assembly

· 2 x 6' Network Cable

· 4 x Momentary Switches

· 1 x Grounding Plate

· 1 x CNC Coolant Hose

· 1 xAssorted Fasteners

· 1 x PLA (Used in 3D printing)

· 1 x Band Saw

· 1 x Hand Drill

· 1 x Soldering Iron

· 1 x Solder

· 1 x Xacto Knives

· 1 x Hot Glue Gun

· 1 x Hot Glue

· 1 x Wood Files

· 1 x Autodesk Inventor

· 1 x Cura 3D

· 1 x Arduino Coder

· 1 x 12V Power Adapter

Files:

Arduino Code: (MRL_16-14.ino)

Step 1: Base Assembly

Picture of Base Assembly

The first main component of the Handi-Hand is the base assembly. The assembly is constructed from a 2x2' piece of 3/4" plywood that is cut into a circle of 2' diameter. To make the 2' diameter platform, mark a circle around the board with a scribe, and cut it out of the board with a jigsaw or preferably a scroll saw. Next, place the pulley assembly so that the top edge of the gear aligns with the top edge of the base while centered. Mark the location of the holes with a marker and drill them to the shaft diameter of whatever bolts you use. If you want the bolts to sit flush, then countersinking the holes is recommended. Now screw the assembly onto the platform and grab the belt and the driven gear from the pulley. Attach the belt and stretch the driven gear off to the side and mark its location. Drill a 2" diameter hole on the dot to mount the servo to. Test fit the pulley to see if the servo drives the system. Assuming all is sitting well, find three empty points on the platform and space them equally from each other along the edge. Now take a 1" diameter bit and make holes for the PVC standoffs. Cut 3 legs each 2" tall out of the PVC and press them into the holes, securing them with a screw. Finally, use aluminum angle brackets to mount the servo in the pre-drilled hole and assemble the pulley system.

Step 2: Arm Assembly

Picture of Arm Assembly

Begin by taking a thin piece of any wood and cut it into a 10x6" rectangle. Mark the four holes on the outer part of the belt assembly on the wood and drill the holes out for some small bolts. Attach the board to the belt assembly and find its center. Place the PVC elbow on the center and trace around the pipe. Now take four angle brackets and secure them to the board and the elbow. To install the servo, wrap it with double sided foam tape and press it into the exposed end of the PVC elbow. Last comes the construction of the electronics platform. Take another piece of thin wood and cut it large enough to fit the Arduino microcontroller. Now use two standoffs and mount the platform to the board on the belt assembly. To complete the platform attach the Arduino to it with the shorter standoffs.

Step 3: Hand Assembly

Picture of Hand Assembly

Begin by 3D printing the .stl files (included below) to make the spoon attachment and hose adapter. Snap the hose adapter onto the end of the CNC hose and press it onto the servo. Slide the spoon attachment over two links of the CNC hose, and secure it by using a plumbing clamp or preferably something stronger like epoxy.

Step 4: Pedal Board Assembly

Picture of Pedal Board Assembly

The pedal board was laser cut using an Epiloglaser 3000, however if such a machine is not available feel free to open the attached dwg files and hand cut the parts. Once all the parts have been made, wood glue them together and mount the switches in the designated holes.

Step 5: Electronics

Picture of Electronics

The first thing to do is wire the switches. Take the network cable and strip the end to expose the four wires. Solder two wires to a switch and make sure to mark which color cable corresponds to which switch. Do this for both sides and route the cables out of the pedalboard. Next, drill three holes at the back of the PVC elbow (these will guide the cables out to be connected with the Arduino). Route the two cables from the pedalboard as well as the cables from the servos and 12V power adapter up through the base, into the elbow, and out the predrilled holes. Connect the servos to the 4 pin headers and the 12V power line to the 2 pin power header. The switch cables should be installed as follows: for each switch run one pin to GND and the other to one of the digital inputs. Finally, attach the grounding bracket to the platform.

Comments

Swansong (author)2017-05-18

That's an interesting design, this could be helpful for people whose hands shake as well.

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Bio: The BCAMRL is a Mechatronics Research Lab, found on the campus of Bergen County Academies a magnet high school within the Bergen County Technical School ... More »
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