My Grade 12 Design Project

       I just thought I'd share the presentation I recently made for a design course I took last semester. We were told to imagine that the year is 2025, and the town of Orangeville has expanded to 3 times it's current size (2013). We were told to predict how it would expand, and then design 3 different public transit systems that could be used in Orangeville. We were also told to make our systems as environmentally friendly as possible. To make all of the 3D models, I used Google Sketchup.

       If you would like to view it, just click here. I'm not the kind of person to brag, but my teacher told me it was the best presentation he'd ever seen.

Robotics: Receiving External Input

     The SSC-32 controller card has 4 pairs of pins that can be used to receive input signals from external devices. These are marked “A”, “B”, “C” and “D” and are beside the Baud rate setting for the serial port. 

     These inputs can be connected to switches and sensors to provide feedback on the positioning of the servos. For example, we can put a simple switch across the “D” pins at the end, and send a “D” or a “DL” message to the SSC-32, to get a message back that tells us whether the switch is open (ASCII “0” or 48) or closed (ASCII “1” or 49).

     To test this we just created another a simple program with a timer called "checkSensor". It works much like our other program, and simply sends the "D" command to check what state the D pins are in(open or closed). This program just logs the state of the input (either 48 or 49) every fifth of a second. Normally the output logs 49, but when we shorted the two pins together for a couple of cycles, the output changed to 48. It change back to 49 when we stopped shorting out the pins.

     We also tried changing the input from "D" to "DL". The difference between the “D” and the “DL” command is that the DL command is a latch. This means that once that switch opens, it will continue to return the symbol for 'open' until it is reset. The D command simply returns the open symbol only when the switch is open.

     When we ran this version of the program, we had to change the timer to fire every 3 seconds so we could see how it worked. When we shorted the input pins, the value being returned switched from 49 to 48, and it didn't switch back, meaning that the latch was successful.

     A latch could be used in a moving robot to detect if hits a wall. For instance, if a robot is moving at a certain speed, then hits a wall, it might bounce off. This could happen in between sensor checks the computer makes, which means the robot won't register it, and hit the wall again. A latch, however, will only allow the computer to hit a wall once, thereby avoiding possible damage to the robot.

ODSS Electric Car Team

     For the previous years at my school, I have taken part in the electric car team. The purpose of the team is to design and build efficient electrical race cars. Generally, each year we revamp or scrap one of the older cars we have, and build a new car, with improved and refined technology. 

      Near the end of the school year, there are several competitions that allow us to compete with other high schools. There are 2 events that take place: the 12 volt race, and the 24 volt race. In the 12 volt, each car must draw power from a single 12 volt car battery, and complete as many laps as possible within one hour. The car that completes the most laps wins. In the 24 volt, each car is powered by 2 car batteries, and as such, the cars have plenty more power and lifetime, making a skilled driver much more important. Speeds in the 24 volt can reach up to 70km/h. In 2010, 11 schools from eight different school boards visited ODSS for this year’s annual electric car competition, which will test the distance traveled by each vehicle in 12-volt and 24-volt competitions. In 2009, Mr.Weishar, our teacher and team leader said the 24-volt winning car covered 38 kilometers in an hour while the 12-volt winning car traveled about 31 clicks.

       In this picture here, from 2010, you can see 3 of the cars built by our team. In the front, number 64, is one of the older models we have. It has a Styrofoam and fiberglass body and focused on maximum aerodynamics. That car is currently being revamped to more advanced standards this year. The next car, in the middle of the shot, number 21, was a successful experiment, in that we made the car as small and as agile as possible. The steering control was the same as an ATV, as in a handlebar that gave the driver more leverage than a steering wheel. That car has done quite well in competitions, all though it has the tendency to roll over at high speeds. Finally(and in the picture below), in the very back is the car we affectionately named 'The Tank'. The idea behind it was to have a heavier body, with a much stronger motor. We found it to be quite troublesome to build, quite hard to control, and overall severely sluggish. as such, it was scrapped for parts at the end of that year. The car that was built in 2011 is of course not shown here, but I'll mention it anyways. It uses a very smart boost power system, where a smaller motor powers the car around turns and other situations that call for agility, but on straightaways, the driver activates a much larger motor for a very powerful speed boost. So far, it has placed fairly high in the competitions it raced in. 

The Team was featured in the local paper during

 the 2010 competition that took place in Orangeville

       Overall, I have highly enjoyed being part of the team, and have learned quite a lot about design and innovation from it. It has given me a large understanding about the design process, and taught me skills that I will be able to carry with me throughout my life.

Raspberry Pi and Robot Plans

          Allow me to show you the Raspberry Pi. It's a very capable computer for its size, just a bit larger than a credit card. The point of it is to introduce programming to kids, to help them build fundamental skills for a career in software engineering. The problem that the makers of this found was that kids were entering post-secondary education with less and less understanding of computers and software. Previously, kids would learn about computers by playing around with simple platforms like the Commodore 64. So the Raspberry Pi was created, a small computer built specifically for hobbyist programming. At its heart is a ARM11 chip, which gives it roughly the same computing power as a first generation Xbox or Playstation. It has 2 usb ports, one for a keyboard and one for a mouse, a lan socket, a mini usb plug to power it with a 5V power source, an RCA and HDMI port for video, and a SD-card slot that it uses for memory.

     My plan for the Raspberry Pi is to combine it with my robot arm to give it some autonomous abilities. The Pi appears to have the necessary features to communicate with the arm, and if it could be put on a chassis along with the arm, then we it would be able to roam around without the need to be connected to the stationary mac. We could write simple programs that would allow the arm to move around and interact with it's environment, such as picking up an object, or moving through a cluttered space by moving debris out of the way. We have also purchased an infra-red sensor, that can be used as a type of electronic eye that the robot can use to judge distances, as demonstrated by this video:

         For the actual frame of the robot, I was planning to make the simple chassis out of wood or lego, big enough to hold the robot arm, Raspberry Pi, a breadboard to connect the two, and the power systems, which will consist of a battery and circuitry to power the SSC-32 card the Raspberry Pi and the servos at the voltages they require. Initially we can just provide power via a cable to the AC power supply. We will also have to figure out how to make a serial data connection between the Raspberry Pi GPIO pins to the TTL Serial Port on the SSC-32 because they are different voltages. I want the robot to look a bit cleaner than just a chassis covered in wires and circuit boards, so I would like to use thin sheet metal to build an outer shell for it, to give it a more professional look.

Receiving Info From the Servo Motors

      Since we successfully sent commands to the controller using the sliders, our next endeavour was to get feedback on the actual position of the servos as they move, using the commands Q & QP. The format of the Q command is "#(servo) Q", and it will send back an ASCII '+' or '.'. The plus means that the servo is currently in motion, while the period means the servo is stopped. The QP command takes the form of "QP(servo)", and will return the pulse width that the servo has been delivered. Using these 2 commands, we can track the servo as it moves.


      We added a text box to the right of slider 4 in our control window and modified our code to have the program show the current pulse width as the slider and the servo both move.
     Our first attempt at coding this was to add a subroutine called “getPulseWidth” that sent the SCC-32 the QP command for servo 4, then read the response and put it in the text box. This operated on roughly the same lines as how we sent sent the move commands to the arm, and then it used the 'read' command to get the signal that was sent back. Because the SSC-32 can sometimes take a few milliseconds to respond, we included a timer that pauses the program for 6 milliseconds to account for that. The program then converts the response to to an integer, and places it in the text box.

      This worked, but we wanted something that would constantly display the pulse width as it changed, not just once when the slider was moved. To do this, we used a loop to call “getPulseWidth” multiple times, constantly updating the text box. It kept getting the value but introduced a few other problems. Since that the loop was constantly running, it became somewhat of a power-hog, and was using processing power when we didn't need it to. This caused large amounts of lag, slowing down our program.

          To fix this,we used a special timer that would trigger every 5th of a second and check the pulse width. This worked perfectly but the timer was still running. We fixed this with the “Q” command, so that the timer when the servo stopped moving. It works by sending the Q command to the arm, reading the response, and if it's a period, meaning that the arm has stopped, it kills the timer.

      We also did one last check of the pulse when the arm had stopped to make sure we got a final position value. This ensured that the position in the text box was correct. We also had to add a couple of lines to kill the timer before we started it just to make sure that the timer was completely reset.




Here's a video showing the final program with the pulse value being updated as the servo moves:

Robot Arm: Writing The Controller

     Since my understanding of programming isn't overly advanced yet, the best approach to building a program for the arm would be to find a program that has a similar function, and modifying it for my needs. After browsing the apple forums, we found a program that someone had developed that could output signals from the serial port. 

       Using a programming environment called XCode, we opened up the program and examined it to figure out how it worked. We then stripped out all of the code we didn't need, leaving us with a solid foundation that we could build upon.

     


       From there, we built a simple interface consisting of six sliders that controlled each of the six servos. The program had to be written in a language called Objective C, which has some similarities to the Java programming language we used in my Grade 11 Programming course, so it wasn't that hard for me to understand.

       Here is a look at a portion of the code that handles the interface. The very first line basically waits for any of the sliders to be changed, and when one is, it activates the code within the curly brackets. The next line creates the format for the signal that will be sent to the robot(the red text). Normally, the signal that is sent to the robot is "#(servo) P(desired servo position) S(speed)". For instance, if you wanted to send the shoulder to position 1700 at a low speed, you'd type "#1 P1700 S100" and then hit enter. So in our program, you'll notice the same format, except the servo number and servo position have been replaced by a "%d", which is used in Xcode as a substitution, so you can get the program to replace that "%d" with any set of symbols, letters, or numbers. 

        The next few lines get somewhat complicated, but all they really do is take the decimal data received from the slider and convert it to ASCII, so the arm understands it. Finally, the last line outputs the ASCII command through the serial port.

Robot Arm: Testing the Computer

     To run the robot arm with a computer, we first needed to make sure the computer could send and receive signals. Since the Macintosh does not have a physical serial port, we used a USB to serial cable that we connected to the physical serial port on an older PC. Then, using terminal emulation programs, which allow you to send and receive signals out the serial port. We set both of the programs to accept ASCII characters, as that is what the robot arm uses, then successfully transmitted a signal to the PC using the Mac, with the same speed and conditions required by the robot arm(115.2kb/s, 8 bits no parity).

Here, you can see that the message that was written on the mac was successfully delivered to the PC using the terminal programs.

     We later used the same method to test if our simple program to control the arm was working. It was better to use the PC to test the program, rather than the arm itself, because we can actually see the signals our program is sending. We used RealTerm on the PC ( download at http://realterm.sourceforge.net ) and CoolTerm on the Mac ( download at http://freeware.the-meiers.org/#CoolTerm ). Both are free and work really well.