Sunday, April 5, 2015

Paul Inmoov get an arm

Paul is the robot I'm building right now, based on Inmoov, the 3D printed open source robot design by Gael Langevin.

I have finish building the right arm of Paul and this post is about it.

The arm is formed by more than 50 PLA plastic 3D printed parts, that took about 90 hours of printing time. All these parts are moved with 10 servomotors of different kind. Six of them are used for the hand (one motor per finger and another one for the rotation of the wrist), the other four motors are used for the movements of the arm. All the motors are connected to an Arduino Uno card. This Arduino card is connected via USB to a PC where I run MyRobotLab open Source framework. This Framework uses the Arduino board as an interface with the robot. As I mentioned in other previous post, MyRobotLab is a service based multi-threaded Open Source framework for robotics and creative machine control. It includes a lot of services for machine vision, video streaming, speech recognition, speech synthesis, motor control, arduino control and more. It is possible to develop new functionalities in Python Open Source language, so I prepared a Python program to do a demonstration of the robot functionality. The following video shows the robot and arm in action. The robot explain what he is doing, so no aditional explanation is needed.

Here is the Python Program used for it:

You could also watch a video I recorder showing how servos move the fingers. Each servo uses two tendons for mooving the fingers, one for closing it and the other for opening it. At this moment the tendons used, transfer to much power to the fingers. A next reasonable step would be to add some sort of tensioner or spring to each tendon, so the motors do not apply to much force to the fingers when they are used to take an object. Also there is no way now to measure or limit the preasure applied by the fingers to the objects. A good option may be either to measure the currend draw of each motor, the tension of the tendones or use some sort of presure sensors at the fingers. A lot of things could be done to improve the capacities of the robot. The limit is the imagination.

Next steps: to build the left arm and the structure of the stomach.