Sandeep Yayathi, Robotics Engineer, NASA Johnson Space Center, Houston, TX
- Sunday, 01 July 2012
NTB: What is still challenging for the robot to accomplish? What needs the most tweaking, would you say?
Yayathi: Making it mobile is a big, big deal. When the robot is stationary, we can develop a lot tasks. But there’s only so much you can do in one spot. We’re headed in the right path from that perspective.
There’s a lot of work that’s still to be done on vision processing and recognition. A lot of challenges with robotics, in general, today are with software — being able to take advantage of all the power that you have in front of you. That’s something that’s just going to continually evolve with time. We brought in quite a few researchers and PhDs to work on that end of development. We’re partnering up heavily with academia and pulling in the latest research, and trading off with researchers. We’re able to take advantage of their labs, their students, and their expertise, and give them an opportunity to work with an expensive, highly capable robot, which not every academic lab has the funding to support. This is a good symbiotic type of relationship that will benefit NASA and the world and researchers alike.
NTB: You’re developing a battery-based power system for the Robonaut. Can you take us through that process?
Yayathi: There’s a lot that goes into that power system, various DC/DC converters, [components] that provide power to the robot, interfacing to higher level control on the robot and power sequence. The core of that is the actual battery itself, and that’s where we started. We knew we’d need a mobile power source if we were going to have the robot running around, and it couldn’t be tethered.
We explored lithium ion. It’s pretty much the premier in secondary cell technology. When I say secondary cell, I mean a battery cell that can be recharged. We did a survey of all the lithium ion technology that was out there when we started, and we identified a cell that we liked that had a really good energy density and also high cycle life. We took that cell and basically worked on optimizing the packaging for it. You’ll find this today with electric cars and various other devices: it’s all about how much energy can you pack into how small a space with how little weight. We’re faced with the same challenge. We want to be able to get the most out of our robot, without having too big of a battery, and without adding too much weight. So packaging is a big deal. We spent a lot of time developing a kind of modular cartridge design that we’d be able to utilize in Robonaut as well as other robotic mobility platforms that would be reconfigurable. We’re trying to have a battery solution that we’ll be able to use in multiple robots and various voltage and current capacities.
NTB: Why is a battery-based system so important?
Yayathi: The number one reason for a battery-based system is to allow mobility. It’ll allow us to freely move about IVA, freely move out EVA eventually, and to any location, and run for a long enough duration to accomplish major mission objectives before having to go recharge. Managing tethers is difficult. Even for people it’s difficult, and the astronauts have to do that for safety. Now managing a tether that’s connected to a power source is even more difficult because you need to have large enough cable bundles to provide all your power. To do that and move freely all around station would be pretty difficult.
NTB: Are there any other technical challenges with the battery-based system? You mentioned packaging.
Yayathi: With lithium ion technology, one of the other major design efforts for us, in addition to packaging, is actually monitoring and balancing cells. We have to be constantly monitoring temperatures, monitoring every cell voltage, and making sure the pack is in balance so when we charge it, we’re not accidentally charging one of the cells up too high. That involves a lot of specialized electronics. We’ve been developing a modular battery management system that can go along with these battery cartridges and change with the size of the robot. It can handle all of that, maintain the battery and operate it safely, independent of the rest of the robot.
Safety is a big concern with large batteries in general. That’s something we’re taking very seriously and has been a challenge. There’s a lot that goes into just building a battery, especially a high-power battery. We see lithium ion cells everywhere today, but something that a lot of people don’t realize is every time you have a lithium ion cell in your consumer electronic device, whether it’s your phone or laptop, there’s a [device] associated with that that makes sure that those cells are within limits. It’s a great energy source, but it needs to be treated with care.
NTB: Is the battery-based system what you’re working on currently? What is a typical day for you?
Yayathi: We started out focused on the batteries and as time went on, I’ve actually been doing more with the actual power distribution electronics: interfacing with multiple other engineers and making sure that we’re doing [parallel] developments and meeting our deadlines. Firmware and software. I actually do a lot of just electrical hardware design: making circuit boards that do all this, working on defining the whole system architecture, making sure that everything goes together right at the end.
It’s challenging, it’s interesting, and it’s nice to be able to come into work and basically start with a system design and actually be designing circuit boards, having them fabbed and brought back in-house, and testing them myself. You get to go through the entire engineering process here. It’s one of the unique things about our lives that’s really nice. Also, we work very closely between the electrical software and mechanical team. We’re all sitting in the same room, and that’s how we achieve the type of packaging that we get in our robots.