Engineering students create solutions to everyday problems
Published July 26, 2013
Inside a testing laboratory in Dolve Hall, an assortment of machine parts line the shelves and edges of the room. Wires, components, engines, motors, actuators – all remnants of inventive mechanical engineering projects from current and previous semesters.
A quick walk through the lab can be overwhelming, trying to distinguish where one project ends and another begins. A machine designed to clean windows as it climbs them sits on a counter. A 3D printer intended to create replacement body tissues that once garnered interest from the Mayo Clinic sits on another.
But walk through the lab with Majura Selekwa, associate professor of mechanical engineering, and it begins to make sense.
Selekwa is the instructor for a two-semester engineering capstone course. In it, upper-level mechanical and electrical engineering students mastermind robotic marvels. Working in groups, the students plan, design and construct an original automated solution to an assigned problem. With no manual to follow, no existing products to reproduce, it’s a true test of their ingenuity and what they’ve learned.
“We gave them a real-world problem and asked them to find a way to solve it,” Selekwa said. “Essentially, they are devising ways to make life easier.”
Wheelchair that climbs and descends stairs
As a 245-pound thrower on the NDSU track and field team, Blake Elsen was the natural choice to be his team’s guinea pig. The senior mechanical engineering major from Maple Grove, Minn., would push the 250-pound designed weight capacity of his team’s creation – an everyday wheelchair able to climb or descend stairs.
Like most projects, the majority of the first semester was spent brainstorming and designing – sketching, CAD modeling – and the second semester was spent fabricating and testing. Along the way, the group produced an oral presentation and printed a technical report, a prototype and engineering notebooks.
“We pose the problem as really only two or three sentences,” Selekwa said. “It takes a lot of time to figure it out. It’s a healthy mix of imagination and engineering knowledge.”
The four-member team began by interviewing Tim McCue, an NDSU residence hall director who has cerebral palsy and uses a wheelchair. He suggested creating a chair that puts the user at eye level with standing individuals. He also asked for the chair to be able to drive backward while going up stairs and move forward when descending – all while handling a diversity of OSHA-regulated stairs that can have a maximum incline of 55 degrees, which is the pitch of the steepest man-made downhill ski run in North America.
“It was different, and it was cool,” Elsen said.
With $500 from the mechanical engineering department and a $4,500 grant from the National Science Foundation, the team tackled the project head-on. Step one – how would it work? “Say it’s going to go up one step,” Elsen said. “What’s going to happen as it climbs this one step? How’s it going to be balanced? If it makes sense in our heads, we started designing it on the CAD software, running an animation to actually look at this thing. Does it still look plausible?”
What the group ended up with was an approximately 90-pound, six-wheel prototype featuring a rotating tandem rear axle. The rear two wheels on each side of the chair connect via an axle, which is designed to rotate as it climbs the stairs. This essentially allows the rear tires to “walk” up and down the stairs. A sliding ski mechanism creates another point of contact, helping balance the chair and provide a smooth ride. The entire operation is powered with four 12-volt batteries, intended to provide a 10-hour charge under normal driving conditions.
The chair itself is supported by actuators on the front and a slide rail in the back. As the wheelchair moves up or down the stairs, it tilts forward and backward to maintain a center of gravity. The assemblage of moving parts was teammate Peter Johnson’s design. “It’s the hardest component we have on there,” the senior mechanical engineering major said. “There is an infinite amount of coordinating components to get the chair to go back and forth.”
The prototype ended up looking a bit more impressive than the original design on paper. “It’s like comparing a stick figure drawing to the Mona Lisa,” Elsen quipped.
Still, Elsen and Johnson have some suggestions for the next group of engineers who will advance the project. Projects in the capstone course are often handed off and improved upon by an incoming team. They suggest incorporating a control board and joy stick to ease user control over the chair, adding more clearance with the front wheels and including sensors to make sure the chair is perfectly aligned with the stairs. Mostly, they suggest getting the most of the experience.
While the stair-climbing wheelchair was designed from scratch, another team was tasked with juicing up an autonomous snowplow designed to plow a driveway or sidewalk with little to no human input. The project started with a design and prototype created the previous year. “Knowledge of the previous prototype is both a blessing and a curse,” said Matt Canton, a senior mechanical engineering major from Plymouth, Minn. “It is helpful to see what can be improved on. However, it is very easy to latch onto a design and build on it rather than think of completely different alternatives.”
The group did both – borrowing components from the tank-like design but redesigning around its limitations. “Nearly everything from last year’s design has been modified in some way,” Canton said. “The biggest difference is in the motors and wheels.”
The previous design used hub motors – an electric motor is fixed within the wheel hub so no additional transmission or drive train is needed. Those motors were replaced with two 28-pound motors capable of producing six continuous horsepower and driving each side of the robot independently.
The wheels have been upgraded to 22-inch high-speed trailer tires. They will be coupled on each side, meaning they’ll operate similarly to how a tank’s tracks move independently of each other. The tire treads will be modified to provide more traction.
The upgrades were decided upon after measuring the force required to pull the previous design’s plow through four inches of snow. “There are many points in a project where you realize your initial design will not work with the specific components,” said Clay Feldner, a senior mechanical engineering major from Bismarck, N.D. “You just have to keep on moving forward. If something doesn’t work, you redesign and find a new way to do things.”
With a design phase complete, the group expects to spend next fall completing the prototype, testing its functionality and perhaps moving some snow. “This is the only course where we really follow the engineering process all the way through to the end,” Feldner said. “Up to this point, everything has been theoretical. Here we actually get a chance to get our hands dirty.”
Device to twist caps off bottles or jars
Many people start their day by opening a jar of peanut butter at breakfast. But for people who have severe arthritis, carpal tunnel syndrome or tendonitis, it’s just the beginning of an everyday challenge.
For the 2012-13 school year’s final capstone project, a team designed an automated twisting device that can twist caps off bottles or jars, as well as open round door knobs between one and three inches in diameter. The goal is to give the user functionality without having to turn the object with their hand or wrist.
As the spring semester concluded, the project was in the late stages of modeling and analysis, according to Tyler Meyer, a mechanical engineering major from Underwood, Minn. Teammates were searching for high-precision electric motors and readying a handle they can create in the NDSU architecture department’s 3-D printer.
“The big benefit of working with a team is everyone has a different way of looking at things, which can come in very useful. Another person might see something you had originally missed when coming up with an idea,” Meyer said.
As with all groups, Meyer’s team meets weekly with Selekwa to assess the project’s status and answer questions. Selekwa said he pays particular attention to teamwork skills. It’s a point of emphasis from the mechanical engineering advisory board that meets annually with the department’s faculty. “In the 80s, mechanical engineering did the drawings and electrical engineers did their part and the project came together,” he said. “Now they work in a team.”
Looking to the future
Many people can copy ideas. It is very hard to visualize new ones, Selekwa said, noting the finished product doesn’t always determine whether a student fails or succeeds. “It’s the way they get there,” he said.
That’s the mindset drawing students into the field. Wesley Green, an Underwood, Minn., native helping design the automated twisting device, came to NDSU largely because he saw the capstone students in action. Building, creating, inventing, destroying – he saw the potential in their hands-on activities. “This field offers me a lot of flexibility in my career path,” he said.
Recent graduates concur. Shortly after graduation, Elsen was weighing a job offer with a Mumbai, India-based solar energy company he interned with in 2012. Canton continues to work with a Hamel, Minn.-based railway maintenance equipment designer. He hopes to one day design cars for one of the Big Three auto manufacturers in Detroit.
Throughout the course, outside engineering experts would drop by, meet with the class and dispense ideas and advice. “They all say the biggest thing they took away from their education was the ability to problem solve in a deliberate and thoughtful fashion,” said Paul Nelson, another member of the autonomous snowplow team. “This project has certainly reaffirmed that sentiment.”