Integration of Subsystems on the Software level

This post we will be talking about integrating the all subsystems on software level. As a whole, we are using 3 arduino boards.

                                Board 1 - Robot Arm and Hand

                                Board 2 - IR Sensors on the Robot Hand

                                Board 3 - Glove (Vibrational Motors)

Shown is the overview of how the user control the robot remotely. Setting up the server is discussed in detail here.

Figure 1 - Overview

Bending angle calculation - FINAL

In the previous post we mentioned the limitations on calculating the bending angle. As shown in the below figure when bending the finger from B to C we get the same angle as from B to A.

Figure 1- Bending angle

As discussed in the new leap SDK post, skeletal tracking enables us to receive data through out till LM can detect our palm. In the previous one we can identify fingers by its ids as long as the fingers are visible. We had to manually identify fingers earlier because when ever the fingers disappear finger id randomise.

Inverse Kinematics on MENTOR Arm - Part 2

As mentioned in the previous post we are using IK only for 2dof (on x and y plane). By that we calculated the joint angles on the Top and Bottom arm for the given x,y,z coordinates. 

Using the conversion from cartesian coordinate system (x,y,z) to cylindrical coordinates (ρ,theta2,r) the joint angle for base arm (theta2) was calculated.

Angle - Base arm

To calculate the joint angles the function "jointAngles" is used. The x,y,z coordinates of the palm that we get from the leap motion data are passed as an array "v" into the function and theta2 - base angle, angle2 - Bottom angle and angle3 - Top angle are returned as the output. 

New Mechanism for the Hand!

Previously ( Link ) we found the Flexy hand limited and unsatisfactory to our needs. We foresee problems with the mechanism and decided to take a different route. In this post, we will explore a different mechanism as described in our presentation (Fig 1), namely linkages.

Fig 1. Linkages (From our presentation , slide 11)

AirGrip Prototype!

ARMazing! (Part Two: Dissecting and our Blue Print)

In ARMazing! (Part Two: The discovery)  we found a robot call 'Mentor' by Cybernetic Application. Feedback Instrument Limited took over the manufacturing rights in Cybernetic Application but Mentor is no longer being manufactured. It was originally used for educational purposes. For this blog post we will show you whats is INSIDE mentor and what future plans we have.

Firstly, a brief acknowledgement to a blogger namely BlizBiggy who was working on another Mentor. You can follow him on here. Here is a video where he talks about his work with Mentor.  

The bulk of the electronics can be found underneath Mentor. Underneath contains a control board, a transformer and an AC-DC converter.

Dissecting Mentor

The front has a set of banana sockets that was used to control external actuators and receive signals from external sensors. This machine takes power directly from the 240 volt wall socket but that won't be necessary for our project. Mentor can take its power from the DC Power Supplies found in our university laboratory.

Banana sockets and power socket

In its prime, Mentor would had been connected to a computer via some old fashion IO interface. Nowadays everything is USB. Here is a close look at the control board (below).

Control Board

Top left: Port for the adapter that
connects to the computer

Bottom left: wires connected to
the banana sockets found
in front of the robot

   

Right side: wires connected to the
motors and potential meters found in the robot arm

The transformer and the AC to DC converter (characterised by the massive capacitors) will be useless for us. We decided to power the robot via the DC Power Supplies we have at our university.

Top: AC-DC converter
Botom: Transformer

We took apart the casing on the arm and found potential meters and gear boxes inside. The gear boxes have very high torque ratio to transform the motor's high speed into powerful torque.

One of the gear boxes

After looking at all the parts we decided to draw up a diagram to illustrate how Mentor will fit into our project.

Interrelationship of power, Arduino, Mentor and the 3D printed Hand.

All we have to do now is work on each box!

Controlling a servo

I managed to find the angle of the bending finger by taking the dot product of finger direction and palm normal.

In the Javascript code I am using the math library. Also this method enables to find the angle when you move the finger side to side.

Then I used the Johnny-five library to interface with the Arduino. Hope this video helps you. 

Next Job is to identify each finger. 

38 Degrees of Freedom

Acetone Vapour Bath gives a shiny smooth finish

We can get rid off the annoying layers(rough surface) on the 3D printed objects by this method called acetone bath. But Acetone bath is only used for ABS plastic. So we cannot do it for our 3D printed hand.

Further doing some research, Yay! Instead of acetone, we can use tetrahydrofuran, or THF, as a solvent for PLA. The process for smoothing PLA with THF is the same as smoothing ABS printouts with acetone.

Here is the method,

The Future of Design

Plenty of hands!

Throughout this week we've been looking through lots of different types of robot hands. Before we settled on the 3D printed hand from Thingiverse, here a few of the things we looked at:

The first thing we heard about was a 'grabber' that apparently Professor Jarvis had. Prof. Russell told us that it might still be in his office, or that Tom Drummond might have procured it. However, when we went to check, neither Tom nor the room had this thing. Instead, we talked to Andrew in the workshop and he showed us that there was a 4M toy robot hand which was probably exactly the same thing we were looking for:

As you can see here, there are only three controlling fingers for the five fingers - this is due to the fact that two of the wires are connected to four of the fingers. Andrew told use he would be able to re-wire it if we were able to buy it. We found, however, that we would be able to do it cheaper!

The next idea we had came from this picture:

This is piping that has some 'hinges' or 'joints' cut out of it, and wires threaded through to control the hand. This seemed to be a very simple option, and Ashan was able to acquire some piping from the Chemical Engineering department (thanks guys!). He made a finger from it, but ultimately we also thought that this was a little too crude. Someone out there has made it look better though! :

However, as I seem to stress over and over again, we decided to go with the Thingiverse hand. It's currently still a little crude, as we didn't follow the recipe exactly, but it's good enough to play with!

Haptic Feedback with the Kinect!

Seems very similar to what we're doing, except with a Kinect, which means it can track a couple more elements of a person. He incorporates flex sensors as well, which might be useful since the Leap Motion cannot sense the joints easily.

He also uses linear actuators, and from forum-trawling, it seems that some people use this site: Precision Micro Drives to find vibrational motors. We will probably be using some slimmer, smaller types of vibrational motors for the haptic glove.