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====== Yu Hang He IRES 2018 Journal ======

**Author:** [[unlv_he|Yu Hang He]]
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Email: <hey6@unlv.nevada.edu>
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**Date Last Modified:** 07/30/2018
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===== Week 8 =====

==== Photos of the Week ====
{{ :yuhang:ires2018:food_market.jpg?500 |}}

This weekend, I went to visit an open food market located on the west side of Daejeon city. The food market is located right next to the Daejeon World Cup stadium. The market was filled with wide variety of food produce, from food and vegetables to meat and seafood. I have the opportunity to witness some live sea creatures inside fish tanks. 

{{ :yuhang:ires2018:seafood.jpg?400 |}}

The open food market is a popular place for local residents to visit and purchase produce. Many farmers and fishers would directly sell their crops and catches directly in the food market. Therefore, the price are cheaper than in the store or supermarket. Even on a Saturday evening, when many of the stalls are closed for the evening, there are many locals wandering through the installs and haggling price with the sellers. It was fascinating to behold such traditional market that is missing from the daily life in Las Vegas.

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==== New Korean ====

{{ :yuhang:ires2018:grandma.jpg?500 |}}

On the same trip to the open food market, my Korean Teacher, Mr. Yoosoon Kim, invited me for a visit to his mother's apartment. In the apartment, I have the pleasure to meet Mr. Kim's mother, who is 84 years old, and his sister, who is a social teacher at a local middle school. Mr. Kim's mother and sister warmly welcomed me to the apartment. I was honored by their hospitality as they invited me to seat and offered me refreshments. I had many fun and enlightening conversation with the family. They were very interested in my immigration experience in American and I learned more about Korean culture. 

==== Korean Cultural Insight ====

Once again, I am deeply impressed and honored by Korean's hospitality. I was surprised when Mr. Kim invited me to his mother's apartment. I am honored by the level of hospitality and trust that Mr. Kim and his family placed in me, even though we only know each other for such a short time. Traditionally, Korean refer to the hottest three days of summer as Sambok. The dates of these days are set through lunar calenders. For 2018, the three days are spread across July and August: 
  *The first HOT day of summer is Chobok (초복) on July 17th
  *The second HOT day of summer is Jungbok (중복) on July 27th
  *The third and final HOT day of summer is Malbok (말복) on August 16th
The Korea tradition for dealing with these hot summer days is to fight fire with fire by eating a hot and hearty meal and that is exactly what I did.

{{ :yuhang:ires2018:hearty_food.jpg?400 |}}


==== What I Learned about Myself ====

Staying in Korea constantly prompt me to be reminiscent of my childhood in China. Many aspect of Korean culture, from food to tradition, appears to me as quite similar to Chinese culture. The similarity reminded me how much I missed my birthplace. I was too concentrated on my daily life in American before to think back to my childhood and birthplace. Even though it has been 8 years since I left my birthplace, I still hold many fond memory of my old home.

==== Project Status ====

Last week, I implement the inverse kinematic function and created PODO AL that will transform mocap data to joint data and execute the motion. This week, I focused on filtering the data and implementing joint angle, velocity, and acceleration limit on the output joint data.

The implementation of joint limit turn out to be more of a challenge then I anticipated. The simplest method to apply joint angle constraint is to limit the angles once they exceed maximum or minimum. The simplest method to limit joint angle velocity and acceleration is to apply a time warp to slow down motion within velocity and acceleration limit. However, both method are not suitable for the project because this project aim at preserving as much original characteristic of motion as possible.

In order to accomplish this, I decided to implement the filters developed by [[https://ieeexplore.ieee.org/document/1014737/|Pollard et al]]. Here are the result of implementation.

Joint angle limit:\\
{{ :yuhang:ires2018:screenshot_from_2018-07-30_10-50-18.png?700 |}}
The blue lines are the original joint angles and the green lines are joint angles after applying joint angle limit and filtering. The algorithm is not perfect, however, it was able to limit the joint angles while preserving some characteristics of original motion.

Joint velocity limit:\\
{{ :yuhang:ires2018:screenshot_from_2018-07-30_10-20-20.png?700 |}}
Again, the blue lines are the original joint angles and green lines are joint angles after applying joint velocity limit and filtering. One problem I noticed for this algorithm is that, for relatively small amount of velocity exceed the limit, the algorithm worked very well. However, once the velocity and acceleration exceeds the limit, the filter will result in a flat angle.

Another problem I noticed is that the first set of data I collected using mocap system are inaccurate and inconsistent. I need to collect more data from mocap system this week and test the filtering.