User:Timoni/ENES-100/Project 1

Week 1 Narrative
My task for this week(end) was to research which kind of motors we would be using to move our robot. The three main choices for a robot motor are servo motors, DC motors and stepper motors. From what I found servo motors are essentially modified DC motors that are easy, efficient and cheap. The main downsides for this motor concerning our project is that this type of motor may not be able to effectively propel the weight of our robot.

After examining size, efficiency, power and ease of use; Ive decided that a brushed DC motor would best fit our needs. The motors are relatively small and can easily be fit into our chassis. With the use of a specially customized Arduino motor shield the motors can be controlled relatively easily.

They are also comparatively cheap and easy to find/buy. Two or more of them should be able to sufficiently move our robot at a decent enough pace without danger, and with the right programming will be able to move in the directions we need it to.

Week 2 Narrative
My task for this week(end) was to finalize the acquisition of the motor. As stated last week, i had planned to go with brushed DC motors to power our robot. However our professor brought out some very significant points about whether or not the DC motor was the best idea. Two main problems with the DC motor was that it did not have the equipment to track how many rotation it had made. Our robot in our planned end stages, should be able to know where it is at all times, and this would be a bit more difficult if the motors themselves had no way to self track. Another issue with the DC motor is gearing. The DC motor does not come with its own gearing, and if we did not gear this motor, it would rotate itself at the highest possible rate all the time, even if we didnt need it to. This would waste power and would make the robot hard to control. Although there were other additional ways to solve these problems, i decided to solve them at the base and instead choose a servo motor to run our robot. Servo motors are capable of tracking how far or in what direction they have gone, and have their own built in gearing. Now the only problem i had with servos before was that they were not the strongest motors. However after some calculations and realizations i found that the servo i chose would be just fine. With a Torgue of 57 oz/in at 6V, the Hitec HS-422 should be able to propel our chassis well enough. With its nice compact size this motor will go very well with our robot. Now with our motors once they are acquired and the chassis that Phillip has built we can actually assemble our project and begin applying code we have brainstormed that will make it move as we want.

Week 3 Narrative
My task this week was to acquire the motor that was ordered and complete the assembly of the actual moving part (base), of our robot. However, as is common in engineering, our group ran into a roadblock. On the day I expected our two Hitec HS-422 motors to have arrived and be ready for use, they unfortunately were not; for various reasons. Now, we had the chassis built and had browsed some code, but we had no motors to test or attach to the chassis. We were then given two stepper previously used stepper motors that were taken off of another project. The problem with these motors was that they were a bit battered, and had no specifications with them. In addition they were two different motors with different wire setups. Also, stepper motors are the most difficult to code. However we still ran with it and mounted them onto our chassis and wheels, which came with its own set of problems. First, the wheels Phillip acquired still had a metal rod through them which prevented mounting. We removed the bar with pliers and then tried again. The problem this time was that the opening on the wheels was much too small for the motor. With the use of a screwdriver, we drilled bigger holes into the wheels. After finally attaching the motors to the wheels with relative success, we were now faced with mounting the combined motors and wheels to the actual base. Since these motors were not recently bought and had already been used, they had no mounting screws or apparatus. Also, at the time the engineering lab was lacking superglue. After a bit of brainstorming I decided that we could drill holes (one above and one below) around the motor and use zipties to fasten them to chassis. It worked as well we could have hoped, and ended up looking like this.

We then proceeded to drill a hole in the middle where all the wires would come from the bottom to the top of the chassis, and we added a nose wheel at the front. Our final chassis looked like this

Now after assembling at least a prototype version of what our chassis would look like, we still had to get the stepper motors to work in order to experiment with some code. Although the main problem of having no specs and not being sure how to set them up could be solved by looking up the parts numbers online to find a datasheet, we had no such luck. One of them had no parts number and the other parts number yielded unhelpful results. After failing on this front, we just tried all different combinations we could think of.

Failure here as well led us to believe that one of the motors wasnt even operational. At this impasse, we turned to buying our own servos from RadioShack. It seemed to work out great until after fiddling with them on Arduino, we discovered that they were not capable of continuous rotation; which made them useless to the base.

For now, we attached them onto the base and will see how will be mounted onto the chassis, as the continuous rotation high voltage servos we ordered

are approximately the same size. We also acquired a battery case for 4 AA batteries that has an on/off switch built in.

Getting the servos to rotate, although it was only at 180 degrees, was quite simple. As we are continuing this project for our next assignment, our goals will be to get the newer servos and get the chassis completely mobile first. Then we will begin working with the sensors and if possible begin moving into building the rest of the robot and work on the arm that will actually carry the beer.