Robot Arm
A LeArm robot by Hiwonder was programmed with an Arduino. Using force sensors for haptic feedback, the amount of force applied to a given object to pick it up could be modulated.
Haptic Feedback
Initially a piezo senor was connected to an Arduino to provide force data. The code for this system can be found here. However, after initial testing by taping two piezos to my fingers and picking up various objects, it was determined that a piezo resistor did not provide the necessary force ranges. Regardless of the amount of object picked up, the reading would output a value of 0 indicating that the sensor voltage was maxed out.
Therefore, instead a force resistor was used that could measure force ranges from 10g to 100 kg of force.
Servo Motors
The LeArm robot came with a servo board but given a lack of documentation, the servo motors were disconnected from the original board and instead connected to an Arduino. The servos were coded to follow a specific that would pick up an object and place it back from the same location each time. The code can be found here.
The code was then combined with the force resisters to output force readings before, during, and after picking up an object. The combined code can be found here.
Final Product
The video above shows the robot attempting to pick up two different objects, a soft foam ball, and a hard 3D printed part. In the first segment of the video, the robot fails to pick up the ball because insufficient force was applied. In the second half of the video the robot successfully picks up the 3D printed object. The readings of the force data were consistently 0 before and after picking up an object. For the foam ball the ideal values outputted by the sensor to pick up the object were between 400 and 500. For the 3D printed object, the ideal ranges were between 100 and 200. This makes sense because the foam ball can deform and more pressure must be applied to overcome the compression.
About the Author
This page was written by Ankitha Durvasula. Check out her personal page here.
