Fequently Asked Questions
Last updated June 21, 2010
What surfaces can Stickybot III climb?
The smoother the surface is, the easier Stickybot III can climb it. As of June 2010, we have tested the robot on glass, painted metal and polished granite. In other tests, the same adhesives have also worked on wood panels, white dry erase boards and plastic panels.
How does it stick to the surfaces?
We are not using suction, double-stick tape, magnetism or static electricty. Our ClimbingAdhesion
is a directional, dry adhesive inspired by geckos. The adhesive pads are a silicone rubber cast in a mold to produce an array of microscopic wedges. The material feels soft and rubbery and not at all sticky when you touch it.
The geometry on the surface of the pads gives it directional and controllable adhesion. Once the pad touches the wall, it will not adhere until the robot puts its weight on the foot (that is to say it pulls along the the wall, in shear). Conversely, the robot can remove its foot by removing the weight and the pad will no longer stick.
Is the tail important or is just for show?
The tail is very important. In order to balance forces, the lowest point the robot must push into the wall (imagine that you are hanging off a ladder -- your feet push into the rung). The tail tip pushes into the wall instead of the back feet. Making the tail longer helps instead by decreasing the amount of force the front feet experience (again, imagine hanging off a ladder in a standing position with your hands and feet far apart and then in the crouching position with your hands and feet close together. You don't have to work as hard to stay on in the standing position).
If this adhesive is directional, how do you go in different directions?
The robot has rotatable ankles. We see this behavior in geckos as well: when a gecko goes down a wall upside-down, it will reverse its back feet such that they point upward.
Do you have to clean the adhesive?
We usually clean the climbing surface and the adhesive pads prior to use, but they will continue to accumulate dust during operation. The new pads are relatively resistant to dirt (as compared to the original pads of angled stalks used on Stickybot
) but will gradually lose adhesion. When they do, the application of a sticky tape will quickly clean the pads as the dirt would rather stick to the tape than the pads (we also note that sticky tape doesn't stick to our adhesive pads at all, in part because when the pads are unloaded, only the sharp tips of the wedges are facing outward.)
I can see a string holding up your robot in all your videos. It's not helping the robot, is it?
This is a safety line in case the robot falls. The robot represents too much labor to ever risk an avoidable fall. We have actually found that increasing the weight robot helps keep the pads adhered to the wall (our weight is limited primarily by the motors) because of the principles behind the controllable adhesion. Any help from a safety line actually hurts the robot.
Where can I get the adhesive?
The adhesive is a prototype, fabricated only for research purposes. While the silicone rubber is cheap, the mold fabrication expensive and labor intensive. We are pursuing new forms of fabrication. We have concentrated on the science behind novel adhesives instead of the engineering required for mass production.
Are you using force control?
The robot has several sensors to estimate the force on each foot but they are not necessary for basic climbing on smooth, clean surfaces. Our continued research will incorporate these sensors. We expect that using force control will increase the reliability of the robot.
Is there an external computer controlling the robot?
No. All computation is done on the robot using a 40 MHz PIC microcontroller. A computer can send commands such as 'start' and 'stop' over a Bluetooth connection, but the robot does not require an external computer or sensors.
All of our robots are research platforms which must be occasionally repaired. The first Stickybot
became too difficult to repair. The second Stickybot
was cannibalized for parts for the first. You can still find the first Stickybot in our lab, hanging out with the sprawl robots
What about the head? Is it important like the tail?
We needed a place to put our electronics and the head was a convenient place given our design.
What do the blinking LEDs mean?
Each motor has its own tiny processor to control it. The blinking lights indicate activity and communication. Green blinking means the motor can hear the 'brain'. Red blinking indicates a loss of communication. Green blinking with a red light indicates garbled communication. No blinking indicates either power-loss or the processor has crashed (like a blue screen of death
. This rarely happens, but it's important to know if it does, hence the blinking.)
How long did it take to build?
One year. Development started late June 2009. The robot began to move in early March 2010. The first climbing occurred in late May 2010. Reliable, fast climbing occurred in early June 2010.
How much did it cost?
It is difficult to estimate the cost of the robot. The parts are relatively inexpensive; the majority of the cost are in the labor. Even a year of labor is inappropriate to measure since we did not track the time spent on the robot versus other non-related projects.
- 21 Jun 2010