Service-Learning Model: An Example

This article is a follow-up of the previous "A Service Learning Model" post. The model suggests interdisciplinary engineering students working on real-life projects that benefit the communities.

Earlier we talked about how this model is useful in three ways:
1. BITSians learn to work on real-life projects that have customer requirements, deadlines and the most essential aspect of engineering: design, build and test.
2. The needy communities benefit from the delivered products, so BITSians help the society around them.
3. BITSians make industry connections so that they share a great relationship at the time of internships, placements.

As an added advantage, such project provides a great platform to strengthen students' skills and resumes. This model, truly has an enormous potential to become one-of-its-kind in India to be implemented exclusively by BITS, just like our renowned Practice School program.

Now, let's consider an example of such a project:
   
Primary/High school children learn basics of physics, biology and solar system roughly in their 1st to 7th standard. It'll be an interesting exercise to create models to teach them basic concepts through interactive mechanical models with which they can play around. To take an example, one project can be to demonstrate operations of a biological cell with the help of a workshop-fabricated model with microcontroller-based sound system, LCD displays and rotation mechanism. This model can be an excellent exhibit in a local science museum. This will benefit the children around BITS campus.
  
 Let's break it down to see what the project components are. Firstly, this project has a great interdisciplinary aspect to it. BITSians from various engineering and science major can contribute. The mechanical subteam can handle: the choice of material, fabrication of the model, fitting various parts to it and mechanical movement capabilities. The electrical subteam can take up microcontroller programming, motor and LCD interfacing and power management. The biology subteam can help with the biological processes within a cell and help draw a skeleton of the model and its intended functionalities. Folks interested in project management can work on the plan, timeline, keeping everyone on track and community/industry communication. They can also apply for industry grants and gather support from local administration.

----There are tons of exciting tasks with each project and each task cultivates a skill that is very useful in post-graduation (industry) life.

More on this model with some more examples in future posts.... Stay tuned!


 

The Battery Management System Design

I will try to glance upon the different important controllers of the electric powertrain system. Let's start with the battery controller a.k.a battery management system.

The brain of a pure electric vehicle is its battery management system. I will briefly go over the responsibilities of this controller in this article so as to give you an idea of what all this battery management system (or BMS) constitutes of. This could prove as a background in case you dive into this field in future.

As described in my previous article the battery constitutes of cells in parallel and series. There could be thousands of cells in a car battery which together produce hundreds of volts and a significant amount of current. Critical parameters of each cell are its voltage, current and temperature. Any one of these if goes out of control, can lead to a thermal runaway which can lead to an explosion. The entire battery is kept in control by its battery management system. The BMS is responsible for variety of function some of which are mentioned below.

State of Charge Estimation:

The BMS is responsible for estimating the charge remaining in the battery and hence the range. Hence the more effective the BMS estimates the range (taking into account factors like terrain, temperature, weather etc) lesser will be the range anxiety of the customer! There are various techniques used to calculate the state of charge in a battery (like coulomb counting etc)

Temperature/ Voltage/ Current Sensors:

It is very critical to measure voltages, currents and temperatures of all these cells. How these three quantities are measured depends on each manufacturer of the battery pack. Usually there is one current sensor measuring the current that the battery consumes or delivers. There are multiple voltage and temperature sensors at various locations to measure these cell variables at throughout the battery. All these are inputs to the battery management system (BMS) and the control logic in the BMS makes sure that these stay in bounds.

Battery Cooling Circuit:

It is also critical to sufficiently cool the battery. In an electric vehicle, batteries are generally cooled by separate pumps or via the radiator. The inlet and outlet temperatures are measured by two thermistors and are fed to the BMS which in turn controls the cooling fluid.

Contactors:

Contactors are nothing but switches that connect the battery to the motor/inverter or charger. Battery contains high voltage all the time. But when a car is not being driven, it’s not necessary to supply this voltage and hence current to the inverter. When a person puts the car into a state where he wants to drive it or charge it (where either the battery outputs or consumes current), these switches close and the loop (battery-charger or battery-motor) is complete. BMS decides when to close the contactors and let the battery drive or charge the car

Safety Monitoring:

BMS is also responsible for keeping the battery in safe condition. In any unsafe condition the BMS will not close the contactors and hence the high voltage will remain contained in the battery itself. Unsafe conditions can include any of the following

1. Over heating of the battery, over/under voltage and over current conditions: BMS open the contactors and isolates the battery from the car if any of the voltage/current/temperature sensors report the above mentioned conditions. 
2. Over charging: BMS stops charging if it detects an over charged cell. Overcharging can significantly reduce the battery health and lifespan. 
3. Unequal charging of the cells: BMS throws appropriate alerts if different cells are charging at different rates. It is also responsible for discharging/ bleeding the over charged cells (if any) and maintain the charge of all the cells to same level. 
4. Over discharging of cells: Over discharging cells also create problems for battery health. BMS prevents that. 
5. Grounding/ Isolation problems: BMS always keeps checking if the battery is properly isolated from the vehicle of not. In case of a short/ thermal runaway BMS makes sure that the damage is contained in the battery and does not propagate into the car. In case of a crash (head on collision) the BMS has provisions to cut the current supply from the inverter and isolate the battery.

For each bullet mentioned above, BMS has its own state machine and probably one person dedicated for its design in the industry! 

So what’s there for you guys here: Mechanical engineers play a crucial role in conceptualizing and modeling the BMS. EE, E/I engineers are generally responsible for designing a PCB that functions as a BMS controller while software engineers write the firmware that does the control. Hence it’s a super interdisciplinary board in an electric car.

I will finish with an interesting video clip explaining the BMS in short. Hope you like it :)

Interesting video clip on the BMS (Click Here)

  

BITSAA Talk on 7th March at BITS Goa

I have had a few requests for the slides from my talk on 7th March. For whatever it's worth, they're embedded here.

In short, the message of the lecture was supposed to be --
Try to make positive contributions in whatever research discipline on campus is nearest to your interests. Co-operate and help your fellow students. Most of all, don't let the small-mindedness, petty quarrels, and unnecessary one-upmanship which sometimes plague engineering campuses drag you down.

If that message reached five people out of the group that attended, I would consider it a success and a favour to me.

A cool web-based circuit simulator!

Here's a simple circuit simulator that is browser based. No need to download anything, just draw a circuit and it's ready for testing!

https://www.circuitlab.com/

Simple and quick, isn't it? 

A Service-Learning Model

A learning model that is increasingly becoming popular among educators, is service-learning based engineering education model. This model has a tremendous potential when applied to engineering curriculum in developing nations such as our country. Our nation has its own social and economic issues. A small percentage of people are both socially aware and financially capable so that they help communities in their humble ways.

How can we, engineering students, help solve such problems? How can we help underprivileged communities?

The answer comes from the fact that the communities are facing problems, some of which can be solved by applying smart engineering solutions designed by students as they learn with the guidance from people from academia and industry. 

To elaborate on this, let's discuss three critical elements of this model:

1. Community problems: These are public/private institutions that help communities with their services. Some examples are: public libraries, night schools, science museums, construction workers' associations etc. They face a number of problems and they have many agenda items to improve the quality of life of their members. We, as students, can identify problems that can be converted to small engineering problems and with the help of faculty, industry people, can  work on solving them. Some examples of such problems could be: designing a software database for library books to be accessed via the Internet (CS, IS), designing a solar power and storage system to be applied for night schools (EEE, EnI), building science/biology demonstration models for school children (ME/BIO),  building battery-operated chairs for handicapped (ME,ECE,EnI).

2. Engineering solutions: While solving such problems, we learn actual implementation of the theoretical ideas learned from the courses. Not only the technical knowledge, but we learn a great deal about team building, finances, public relations, and most importantly professional approach to solving problems. Applying such practical solutions to real problems makes this model an extremely powerful tool. We can take those projects as LOP,COP to get suitable credits for our work. When we deliver the product to communities, we actually contribute serving the communities!

3. Industry reviewers: Our industry is more than willing to donate money for social welfare. They need a proper established channel. Funding such projects can be an excellent way not only to empower the communities by the delivery of products, but to help engineering students learn practical tools along the way. Industry can send the reviewers to critique the design and monitor the progress. This relationship is extremely helpful in terms of getting funded projects, practice school stations and finally placements!

This model is developed by educators in Purdue University, West Lafayette, IN, USA and is currently running successfully since last 10+ years (https://engineering.purdue.edu/EPICS). It has numerous imitations all over the world. If the BITS administration decided to apply this model, they will not only increase the level of engineering education, but help serving communities across the nation.

As students at BITS, we can go and talk to communities and take up small projects, work on it and make a difference as well. This will be our share of service to our nation while adding value to our own engineering education and opening doors of countless opportunities through industry contacts.