Week 13 (Nov. 21, 2018): Pre-Thanksgiving Meeting – Max Charging Distance & Max Motor Acceleration

-

Although there was no meeting for any of the ME 195A students today due to the Thanksgiving break starting tomorrow, we did briefly speak to the Small-Scale Track Team and Small-Scale Bogie Team to plan for the final presentation, Presentation #3, and share our calculations that we all could include in our presentation slides.

We bought both the 12V, 600 mA and 5V, 2A induction charging modules, just in case one does not ultimately work out. However, we will try the 12V, 600mA one first. We told the Track Team that the max charging distance of the 12V, 600mA induction charging module is 20 mm, or 0.787 in. So, we should account for this max allowable distance when we design the charging station and/or hub. Recall that The Small-Scale Track team is planning to construct a Y-bend located in the middle of the track, and then together, we will create and install at least two induction charging stations within the Y-bend, acting as a sort of “pit stop”.

We also shared with the Bogie Team our calculation of the max acceleration that the gimbal motor will experience resulting from the 7.4V of the battery. Ideally, we want the pod car to move at a constant speed throughout the rest of the trip. So, the only acceleration we have to consider is the start-up acceleration to speed up from rest to the max velocity. The max velocity, given 7.4V, is 1.051 m/s. We can then say that we want to accelerate for about 2 seconds. So, the acceleration would be: 



So, this would be the max acceleration if we want to accelerate to the max speed in 2 seconds. The Bogie Team will have to account for this when designing the wheels.

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 22 (Mar. 13, 2019): Battery Clarification and Boost Converter

-
Image
To begin today’s post, we will make a slight rectification to our earlier posts. In prior posts, we stated that we are going to use a 3.7V Lithium-polymer (LiPo) battery. However, more specifically, we are using a 3.7V Lithium-ion (Li-ion) battery. While there are some differences between the two types of batteries, since they are both lithium-based batteries, they utilize the same chemistry for the most part. Li-ion batteries are the ones that are found in most cellular phones. We found that these batteries are more favorable to use in our project than their LiPo counterparts. Whereas LiPo batteries suffer from a shorter lifespan, Li-ion batteries are more efficient and have higher power density, meaning they contain a large amount of energy in a small package. Furthermore, Li-ion batteries cost less than LiPo batteries. Even though Li-ion batteries are “potentially dangerous”, we won’t be driving heavy loads, and we will be testing in an open environment, rather than a confined
Read more