Introduction: Human-Computer Interface:Function a Gripper(made by Kirigami) by Wrist Movement Using EMG.
I made a device which recorded hand signals using an EMG sensor and then output it to a robotic gripper, which I made using kirigami. I coded this project in Python and Arduino. On a larger scale, this EMG gripper, normally used in robotic surgery, could be used as a prosthetic arm or on machines to lift heavy objects such as a mechanical gripper to pick up garbage.
Supplies
1.ESP-32
2.Jumper Wire
3.EMG Sensor (including ECG electrodes)
4.Servo Motor (SG-90)
5.DCPU (note-this can also be done without using the DCPU by doing the connections directly to the ESP-32.)
Step 1: Connecting the EMG Sensor to the DCPU.
Before starting clip to ESP-32 to the DCPU.Now we need to capture the EMG signals. This will be achieved by connecting the EMG sensor to the DCPU.The connections of the jumper wires will be done in the following way(EMG-DCPU).-:
1. GND -GND
2. 3.3V-Vcc
3. Out-35 (or any of your output prefered pins)
*The whole circuit diagram is given below*
Step 2: Connecting the Servo Motor to the DCPU
To move the origami gripper we will be using a servo motor. When we move our wrist up, the servo will rotate and when we put our wrist down , it will come to its initial position. The servo will be connected in the following way(Servo-DCPU)-:
1.Gnd-Gnd
2.Vcc-5v
3.Out-32
Step 3: Making the Origami Gripper
Ive attached a file with the layout of its design. The straight black lines are the ones which need to be cut and the dotted lines are the lines you need to fold.Get the attachment printed on a thick a4 sheet.
Attachments
Step 4: Making the Gripper Functional
To make the gripper functional we’ll have to put in two strings/threads from the top to the bottom as shown in the figure.
After putting in the strings try pulling both of them and the gripper should close and open. If not, try increasing the size of the holes or reinserting your thread.
Step 5: Attaching the Servo Motor to the Gripper
To build a stable stand for your servo motor and gripper you can use a box. I made an origami box that i used to secure the servo motor and the gripper. You can print out the attachment I’ve given to make the box. (Measurements written in the attachments are wrong so just print it on an A4 sheet without worrying about them.)
After putting the servo motor in position in the box , attach both the threads of the gripper to the holes present in the Servo Motor attachments. Keep the strings tight so that as the servo rotates , the gripper can close.
Attachments
Step 6: The Final Step and Code
Attach the electrode cables to the EMG and place the red electrode on the top of your wrist,below your knuckles. Now place the yellow and green electrodes on your forearm. Refer to the photo for exact position.
Finally you have to put in the python and arduino codes and upload them. The codes are provided below.
The project is now ready. After uploading the arduino code open python and run the code. You'll see a graph showing some values on the y-axis. Keep your hand straight and note the initial value on the y axis. It will differ from person to person (for me it was 0.1). After noting the value , edit the python code and put in that number in the variable 'threshold'. Run the code again and you’ll now see the whole project in action.
[Note- For the gripper to work properly and the emg to take correct signals , position yourself away from any turned on electrical switch , charger or device that can interfere with the emg signals.]
