quinta-feira, 8 de maio de 2014

May 4th

Following the previous post, on this week I've been working on the software.

At this point I've developed two programs. The first program is responsible for the calibration of the sensors. This program receives data from the sensors and at the same time launches an interface, Figure 1. 

Figure 1 - Calibration interface menu.

On this interface it's possible to load an existing calibration or to create a new calibration. The load menu is for monitoring purposes only, while the new calibration menu is in charge of the creation of a new calibration profile. Upon completion of the profile, it's saved in a .xml file for future use.

The other program is the one that I mentioned on the previous post. I've made some changes and now after getting the data from the hardware it reads the .xml file, if there is any, and loads the calibration values. After this it calibrates all the incoming values and publishes them on ROS. Also, I added a launch file so it's possible to run the program using roslaunch command.


quarta-feira, 30 de abril de 2014

April 28th

On the past weeks I've been working on the Android App. I wanted to make an App that could communicate via Bluetooth with my setup. To create this application I've been using the Eclipse IDE with built-in Android Developer Tools (ADT). So far I've an application that have the calibration interface and the settings menu to setup the bluetooth. I've never had programmed in Java therefore is being a rather interesting learning process!

Last week, on Friday, my sensors have finally arrived! I got 4 Force Load Cells, 6 Force sensitive Resistors and 4 IR sensors, and their signal conditioning and acquisition board. 

Figure 1 - Phidgets InterfaceKit with 3 connected sensors and a LED for testing.

Figure 2 - Force Load Cell mounted in the pedal case.

Figure 3 - FSR with the signal conditioning board.

Figure 4 - IR Sharp sensor with the conditioning board.

The acquisition board is the InterfaceKit 8/8/8 from Phidgets, and to be able to collect all the data, it's required to create a program using the Phidget library. On this week, I've been making some changes on my ROS Package so it can read the data not only from Arduino but also from the Phidget InterfaceKit. At the moment the program get the data from the hardware asynchronously (IR sensor at 40Hz and the other sensors at 1000Hz) and publishes it on ROS. 
Next, it's required to add the GTK interface to calibrate the data, this should be capable of making the pedal calibration and save it into a file. After this the interface would be able to monitor the action on the pedals using the calibration file or not - Figure 5.

Figure 5 - Program scheme.


quinta-feira, 10 de abril de 2014

April 7th

Hello everyone!

On the meeting of the last week I've been challenged to make my project more flexible in terms of communication via Wireless. So this week I've been searching for bluetooth shields for Arduino. I've found some interesting devices like the Bluetooth Bee, that is a module with the XBEE design and size - Figure 1.
Also I've found a device that is a BLE 4.0 Module HM-10, that is smaller than the Bluetooth Bee and supports the bluetooth low energy 4.0 (BLE) - Figure 2.

Figure 1 - Bluetooth Bee.
Figure 2 - HM-10 BLE 4.0.

At last I've found the device that I think that would be the perfect one that is the BLEduino, that is a Arduino with a  built-in bluetooth module, however it's not available for sales yet!

Figure 3 - BLEduino.

To be even more easy-to-use I've started to learn and develop an android application that communicate via bluetooth with the system. At the moment the application is very simple but soon I hope that I'll be able to show you something good!


quinta-feira, 3 de abril de 2014

March 31th

On this week I've made some changes to my hardware.

As I said on my last post, I modified my acquisition board to a much more complete one. On this board I added the tension to current converter that will convert the sensor signal into current and send it to the receiving board that will have a resistor to convert this current to tension so the Arduino can process it. Also, because It's required to have the sensors isolated from the Arduino I added a DC/DC converter with isolation so I could have two different grounds.

Figure 1 - Complete acquisition board for 6 sensors (2 FSR, 2 IR, 2 Load cell) with V/I conversion.

The other changes are the JST-PH connectors that I added so that the board is prepared to install six sensors: two FSR, two load cells and two IR sensors. Also I added two RJ-45 connectors that will be responsible for supply and for sending data to the Arduino.

Also on this week I finally got my last prototype case of the sensors, with a few changes from the other drawing, and I found a pedal controller (used to play video-games) that is great to do some testing before I make it to the ATLASCAR.

That's all for now, I'll keep in touch!


domingo, 30 de março de 2014

March 24th

On this week I’ve been doing a several things. As in every project, it’s essential to have the documentation of all the work! This week I started to draw all the circuits of my hardware and to project the PCB Board in Eagle, as I said that I would be doing before.

The board is meant to be able to gather all the data from all the sensors, which are a force load cell, a force sensor resistor (FSR) and an infrared distance sensor, amplify the signal and convert it from tension to current. This last requirement is very important because the sensors will be far away from the Arduino. If the signal goes from the sensors to the Arduino in tension the signal may vary due to the resistive wire losses and as well, in current the signal has a greater electrical noise immunity.

The first board that I made, as you can see on the figure, doesn’t have yet this V/I converter so I’ll be making a few changes on the next week to add that.

Figure 1 - Acquisiton board made in Eagle Software.

Also the board has only three slots for one of the kind of sensors that I mentioned, however I’ll be using two of each kind so I’ll have to add more connectors too.
As for the connectors, I am using molex connectors but they are not the best considering their size and utility, so I’ll be switching those for RJ45 connectors for the supply and the signals, that able to have 8 wires in just one cable, and JST-H connectors for the sensors, that are much smaller than molex.

At the same time I’ve been creating a new package in ROS with a script in C++ that reads the data from the hardware and displays it as a kind of progress bars on ROS-RViz. 

Figure 2 - Displaying data on RViz, green - load cell, blue - FSR and red - IR sensor.


terça-feira, 18 de março de 2014

March 17th

On this week I will be working on Eagle which is a software that allows to project PCB boards, because later I'll have to make some of these boards for the signals acquisition.


quinta-feira, 13 de março de 2014

March 10th

On this week I did some drawings of my prototypes ideas and built a test prototype so I can be prepared to test and get data when the sensors arrive.

Figure 1 - Isometric view of the test case for the sensors.

Also I made a list to order all the equipment that I'll need the most for my project. For example, force load cells, force sensor resistors (FSR), IR Distance sensors and acquisition boards and adapters.


quinta-feira, 6 de março de 2014

March 3rd

On this week I did some research on how could I measure the forces on a pedal. There are two systems, one using Force Sensing Resistors (FSR) and other using Force Load Cells.

The FSR are flat sensors that have variable resistances between their 2 pins depending upon the force applied. When the force applied increases the resistance goes down. These sensors are easy to use and also relatively inexpensive, however it has some disadvantages such as drift and poor accuracy, errors up to 25%.
Depending on how long and how hard it's pressed, the FSR value will come back to approximately 95% of its initial value almost instantly, and than drift the final 5% over a few seconds. In conclusion these sensors aren't the best choice when it's required accuracy and repeatability.

Figure 1 - Force Sensing Resistor.

The Force Load Cells are transducers that convert force into an electrical signal. The applied force deforms a strain gauge and that strain gauge measures the deformation as an electrical signal. The output signal is typically very small so it's required to amplify it by using an instrumentation amplifier. The load cells have higher dimensions than FSR, however they have high accuracy and repeatability, which, in my opinion, are very important aspects when building a system like mine.

Figure 2 - Force Load Cell.

Also, I wanted a sensor that would be able to measure the distance from the pedal to the car floor. After some research I found an interesting IR Distance sensor for very short distances (4-80cm).

Figure 3 - IR Distance Sensor.


sábado, 1 de março de 2014

Feb 24th

On this week I had a workshop about C++ and Robot Operating System (ROS) at the LAR, where I learned some important things of C++ language and some basics of ROS.

To develop my software I'll be using C++ and ROS so this really was a major added value.



segunda-feira, 17 de fevereiro de 2014


My name is Pedro Mendes, I'm 23 years old and I'm doing my master's degree in Mechanical Engineering at the University of Aveiro, Portugal. 

This is my final year, therefore the next months will be spent working on my thesis. In this blog I'll write about the progress of my work for those who are interested in this area; I also hope to get some feedback so you're truly welcome to do so!

My thesis project is entitled "Intelligent Monitoring of Human Performance in Vehicle Pedals", and is a part of the ATLAS Project, in particular ATLASCAR, which is an endeavour of the Mechanical Engineering Department to create an autonomous driving car. If curious you can take a look at the ATLAS project - http://atlas.web.ua.pt/ - and the Laboratory for Automation and Robotics (LAR) - http://lars.mec.ua.pt/index.html - websites.

Figure 1 - ATLASCAR.

The intelligent monitoring of the pedals of a vehicle represents a great advantage not only for the assisted driving but also to the study and analysis of risk driving situations, increasing driving safety. The aim of my project is to find correlation between various pedal actions (contact, pressure, force, etc.) and other vehicle variables (acceleration, engine speed, etc.).

I have established a couple of main objectives that will serve as guidelines for my project:
  • Develop an easy-to-use non-invasive hardware, to get information from the pedals;
  • Create a software interface to monitor and calibrate them pedals;
  • Evaluate and characterize the driver's behaviour, analyzing the data from pedals and other variables of the car.
In the past few weeks, I have been working in a very intuitive interface that monitors and calibrates the pedals as well as in hardware development. At first, it were being used potentiometers to simulate the action in the pedals with serial communication, but now I managed to swap them with piezoresistors and to add SPI communication.

Figure 2 - Hardware using potentiometers.

Figure 3 - Hardware using piezoresistors.

This week I'll have my first LAR meeting where I'll present my thesis project thus I'll be preparing it.

That's all for now, I'll keep in touch!