Week 21 (Mar. 06, 2019): ME 195B - Presentation #1 (Prototyping Stage) Reflection

-
Today, we presented our first presentation of our second semester of ME 195B - Senior Design Project, making it our 4th presentation overall, throughout the entire duration of senior project, since last semester. 

Please refer to our Presentation #1, embedded below. 

Up to now, we have gathered all of our major components and are starting to prototype one small-scale podcar. Although, if we find that we need to buy a smaller component, we do so immediately to get ahead of the delivery time. Besides the gimbal motor and the accompanying ESC (electronic speed control), we have tested all the parts and have found that they all work individually. 

Despite the fact that there's limited information on gimbal motors on the internet, we found some Arduino code to run the gimbal motor and ESC. However, regarding the connections, we have all but one connection - the connection between the ESC and the battery; all we need is an XT60 connector to connect the ESC to the battery; it is currently in delivery. After the presentations today, we will make the gimbal motor connections and test the motor. 

Following our Presentation #1, we received some questions from Dr. Furman primarily about the gimbal motor. Because we don't yet have the XT60 connector, and thus haven't been able to test the gimbal motor, we could not answer his questions properly. 

Dr. Furman asked us two questions that we would now like to retroactively answer. 

The first question was if we were sure that gimbal motors are intended to be run slowly. Our answer is: not necessarily. The speed can be controlled, albeit to a limited degree, with a potentiometer connected to the Arduino. The Arduino will read analog readings from the potentiometer as its knob is turned. Accordingly, the Arduino code will set a proportion to scale the potentiometer readings to a speed value to write to the ESC. 

The second question he asked us was if we will be controlling the speed of the motor. To answer, we will find a good speed and then set the potentiometer reading permanently. We will also make the motor start at a lower speed, and then accelerate to the desired speed. We will accordingly gear down the motor, as it seems the lowest possible speed of the gimbal is still too fast. 

After completing these prerequisite actions, we will then ensure all the components to run together and complete one podcar. We will have to complete one podcar prior to Presentation #2 so that we can present good progress, and from there, it will be easier, as we would simply have to replicate our actions to the other podcars.

Comments

Post a Comment

Popular posts from this blog

Week 6 (Oct. 3, 2018): Coordination with the Small-Scale Bogie and Track Team

-
Image
Today, we discussed overlapping aspects of the small-scale system with the bogie team and the tracks team. The track team has settled on a design for the new track: a rectangular shape track with a Y-junction junction in the center to accommodate two charging stations, one at each branch. We are hoping to implement induction charging at these stations, which requires a 3.7 V Li-ion battery. Something else to consider is if we can use a transistor to amplify the current draw from the induction charger to speed up charging of the Li-ion battery and if we can use a boost converter (step-up transformer) for the brushless motor we will use. With the bogie team, we discussed motor sizing, as this selecting the appropriate motor would affect the force that the wheels would experience, and thus the design of the bogie. The force of the motor would be found by: (1) determining the power supply current output to the motor, I ; (2) converting the speed constant, K V , which is provided
Read more

Week 10 (Oct. 31, 2018): Battery Selection

-
Image
 UPDATE: Calculations for the induction charging and battery are found in the Week 14 and Week 15 blog posts. After finishing the last of the Presentation #2’s, time was provided to continue working on our projects. The first subject we wanted to address was to finalize the selection of our battery. So, we listed the pros and cons of the three main battery types: LiPo (Lithium-Polymer), NiMH (Nickel-Metal-Hydride), and Li-ion (Lithium-ion).   Sources: Roger’s Hobby Center | A Guide to Understanding LiPo Batteries and NiMH Vs LiPo Batteries - Which is better? and All About Batteries We eventually decided that we will be using LiPo batteries, like last year’s team, since they are more efficient and have a high energy density, along with their other benefits that outweigh their disadvantages and dominate the other battery types. Also, the fact that mini-LiPo chargers exist, such as the one below from Adafruit, will make charging more robust due to its compact design.
Read more

Week 4 (Sept. 19, 2018): Revised Project Objectives & Proposals

-
Today, Colin, a member of last year’s Small-Scale Controls Team and possibly our mentor/contact/guide, visited the Spartan Superway Design Center to provide us with advice, problems his team faced, features that they were hoping to implement but never got around to, and feedback on the design ideas we proposed.   Addressing our first idea of installing a differential drive system that would drive the wheels that move along the outer rail faster than the inner wheels when making a turn, preventing over-exertion of the servo motor steering the wheels when making a turn , Colin stated that we have two options: (1) Use two servo motors and incorporate the drive differential. However, Colin warned that he and his team used up all of their extra servo motors (about six extra) during their exhibition at Make’s Faire. So, he suggested buying three servos for each day spent at the Faire (three servos x three days = nine servos). If we want to pursue this idea, he suggested looking int
Read more