Hizook

I've been doing a lot of searches for literature and examples of small, "micro" robots. First, let's clarify what constitutes a "micro" robot, as there are a number of competing definitions (for example, the 1 in³ robots from the RoboGames are called "nano" robots, yet clearly they are not at the nano scale). In general, I prefer the following definitions, as they seem to follow common sense.

Thus the general size I was searching for was between 1 cm³ and 64 cm³ in total volume, or between 1 cm and 4 cm per dimension (the smaller, the better). I'd like to share what I've found and later ask for some help. Let's take a look at some great examples!

First up is Pico, which hit the blogosphere earlier this year. While the builder falsely believes his is the "world's smallest robot," it is impressive for a home-brew bot!

The robot measures in at 2cm³ (12.5mm per side), and features a laser-cut chassis and two Didel motors (MK04S-24 driving worm gears). With a run-time of 15 minutes off a 10mAh Li-Poly battery (approx 3.7V), that equates to a power consumption of about 140 mW. I suppose the large power consumption is to be expected, given that his Didel motors can use as much as 100mA at 3V! I'm still impressed. Given that these sort of webpages have a tendency to disappear, I have archived a copy of the page here. He even has a video (local copy here).

Another effort comes from the Ecole Polytechnique Federale De Lausanne (EPFL, a University in France), where they have developed a series of micro-robots. The builders of these robots actually went on to found Didel, where the motors from Pico originated. Unfortunately, the robots lack (in general) detailed technical specifications. Either way, they are very aesthetically pleasing and have phenomenal mechanical designs (with custom-machined gears). For example, here is one of them that measures 1 cm³.

This robot has been built by André Guignard and programmed by Olivier Matthey.

It uses two smoovy 3mm motors from RMB. A first gear transmits the movement to the wheels, made of the second gear level. The initial design was using a rubber caterpillar, but its efficiency was too weak. The robot does not fit any more into one cubic centimeter. We have to find better ideas for the next generation.

A PIC 16C54 drives directly the motors. Two photo-transistors and one LED have been bonded on the side in order to follow a wall. This is not yet operating well; the ambient light is too strong compared to the LED power.

 

Another one from the same university is Jemmy, also 1 cm³.

• Driven by two synchronous 3 mmØ RMB smoovy motors.
• Four passive infrared sensors.
• Embedded PIC microcontroller, which generates the 3-phase signals for both motors, performs time-to-voltage conversion to read the sensors, and communicates using a single-wire bidirectional link with an optional supervision unit. To speed up software development, all variables of the embedded processor can be read/written through this communication channel.
• Precision gearing, 8 miniature ball bearings
• This robot was the winner of the International Microrobot Maze Contest '97, Nagoya (Japan) in the 1 cm3 category.

Curiously, it appears (though I have no confirmation) that both of the 1 cm³ robots from EPFL are tethered for power. However, their 1 in³ robot Inchy is not.

• Three rechargeable Leclanché Ni-MH button cells provide an autonomy of 15 to 30 minutes.
• Two synchronous 5 mmØ RMB smoovy motors, with which speeds of over 30 cm/s can be achieved.
• Four infrared proximity sensors, which can be replaced by other devices simply by exchanging the removable top PCB.
• The microcontroller performs the same tasks as in Jemmy. Furthermore, it is located on a removable PCB (at the bottom) and also can be reprogrammed in-circuit within seconds by attaching our programmer to the 5-pin connector visible on the top.

Perhaps the most promising robot to come out of EPFL is Alice, a 8 cm³ (2 cm per side) robot.

By herself, Alice isn't all that interesting (it's not the smallest, and it doesn't have the most functionality). But the vast number of publications that document Alice's construction and place in the micro-robot space are invaluable.

• "Autonomous Micro-Robots: Applications and Limitations" (local copy)
• "Mobile Micro-Robots Ready to Us: Alice" (local copy)
• "Fascination of Down Scaling -- Alice the Sugar Cube Robot" (local copy)

Alice also boasts an impressively low power consumption!

Dimensions: 22mm x 21mm x 20mm
Velocity: 40 mm/s
Power consumption: 12 - 17 mW
Communication: local IR 6 cm, IR & radio 10 m
Power autonomy: up to 10 hours

The low power consumption is largely determined by the very-low-power SWATCH wristwatch motors. Based on the Alice 2004 Poster (local copy), it appears that they even sell/sold some of the Alice robots to research institutions for $500 SFr (about $415 USD) each. There are also a number of expansion modules for Alice, such as solar power, camera, radio, gripper, and off-road traction.

One awesome use of these robots is to study swarm/collective behavior. Check out this cool video (local copy) showing a swarm of 90 Alices acting simultaneously.

Another micro-robot was developed by Sandia National Laboratories. Measuring in at 4 cm³ (0.25 in³), it was an impressive feat when it was first announced, given its size, untethered power, autonomous operation, and sensor suite (which included chemical sensors). Its drive train is also visually appealing. Below are some pictures and a video (copy).

 

Finally, let's not forget the Epson EMRoS series of micro robots, which made it into the Guinness Book of Records.

The Monsieur II-P prototype microrobot represents a step up from the earlier generation of EMRoS series microrobots. Not only does it run longer and faster than its predecessors, but it can also be flexibly controlled. The enabling technologies? An ultra-thin, ultrasonic motor and a low-power Bluetooth module, both products of Epson's R&D lab.

There were four members of the EMRoS family: Monsieur (1 cm³ in volume and listed by the Guinness Book of Records; 1993 ), Niño (0.5 cm³ in volume; 1994); Ricordo (1 cm³ in volume and equipped with a recording and playback function; 1995); and Rubie (a 1 cm³ microrobot equipped with capricious wandering function;1995). All are autonomous traveling robots that chase a light source. Sales of the EMRoS series have been discontinued.

That's a bummer that they were discontinued. The specifications were pretty impressive -- they included bluetooth control?!?

Prototype Microrobot "Monsieur II-P" Features: An ultrathin, ultrasonic motor enables the left and right wheels to be independently controlled, allowing the microrobot to be driven forward and backwards, as well as perform pirouettes. A Bluetooth module enables multiple units to be controlled simultaneously. (1) Power supply: Three air-zinc battery (1.4 V) connected in series (2) Running time: 5 hours (3) Traveling speed: Approx. 70 mm/s (controlled) Approx. 150 mm/s (not controlled) (4) Operating voltage: 2.0 V (CPU & Bluetooth module) 2.2 V (ultrasonic motor) (5) Weight: Approx. 12.5 g (total weight) Approx. 5.5 g (internal parts, including ultrasonic motor) Approx. 4.3 g (three battery cells) Approx. 2.5 g (housing) (6) Volume: Approx. 7.8 cc (excluding projecting parts) * Monsieur II-P is a prototype only. There are no plans to market it as a commercial product.

Of course, let us not forget the MIT Ants, which measured in at a hefty 38.5 cm³. I suppose the "bulk" is forgivable, given the plethora of sensors...

 

Width (Excluding whiskers): 1.4 inch
Legnth (Excluding whiskers): 1.4 inch
Height: 1.2 inch
Weight: 1.18 oz

Total Battery Voltage: 2.4 volts
Batery Type: Varta VT110 1.2v NiCd cells
Bettery Life: 20min

Motor Stall Torque: .5 oz/inch
Wheel Radius: .25 inch
Max Speed: .5 ft/sec
Gear Ratio: 59:1

CPU: Motorola M68HC11E9 in the TQFP package
Clock Speed: 2Mhz
Memory: Xicor X68C75 8k EEPROM

4 Infrared Receivers
4 Light Sensors
2 Bump Sensors
5 Food Sensors
1 Tilt Sensor
2 Mandible Position Sensors
1 Battery Voltage Sensor

1 IR Beacon Emitter
1 IR Tag Emitter
3 Mood LEDs

Anyway, this is by no means a comprehensive coverage of past and present micro-robots. This CMU page (when it works) lists a number of other micro-robot platforms.

Since I'm fairly interested in these micro-robots, I've been thinking about building some of my own. I've been searching for good motors, gears, and other mechanical components. However, so far only Didel and Smoovy motors seem to be available (recall that their power was an order-of-magnitude worse than the wristwatch-based motors). Does anyone have any insight on wristwatch motors, such as suppliers and models? I'll probably make a separate post later about micro robot components (motors, chassis, sensors) and electrical design (microcontroller, wireless bootloaders, etc)...

UPDATE: I've got a bunch of new pictures and videos from RoboCup 2007 posted. 

I was really bummed this summer when I missed the RoboGames. However, I consciously made the decision not to go since the RoboCup 2007 is in Atlanta this year, and is being held at my graduate school -- Georgia Tech! Because of this, I will be volunteering for several of the days, and I get up-close contact with the robot-builders, spectators, and event organizers.

Anyone with a Georgia Tech ID can get a spectator seat for free. If you're not so privileged, tickets can be had for like $10 (weekdays) or $20 (weekends). There are a TON of events this year (Small, Mid, and Junior soccer, Humanoid Soccer, 4-Legged Soccer, Nanogram, etc). It is being held across about 4 different venues (Campus Rec Center, Tech Square Research Building, Student Center, and Fox Theater), so there is plenty to watch. It is difficult to describe how large this event is, and how wonderful the caliber of robot-builders is (especially compared to other events I've attended, even compared to RoboGames). Just look at these shots of the "main" venue (Campus Rec Center).

From the front of the spectator area:

From the back of the spectator area:

There is literally always something cool going on, and the robot-builders are very friendly (from many different countries). For traditional roboticists, this is like heaven. I still miss some aspects of the RoboGames (like mini-Sumo); however, I don't really miss the BattleBots. The glorified RC cars usually don't appeal to traditional roboticists, but I'm sure that many enthusiasts would be disappointed by their absence.

Official competition just began today (Tuesday, July 3rd), but the event continues up through July 10th. I haven't seen any coverage on other blogs about RoboCup 2007, so I figured I'd share a selection of my pictures and videos (from team practice day -- yesterday on July 2nd).

This is a Junior Soccer League robot from Team Takahama. I had a chance to speak with this team at length, and I found their robot rather interesting. It uses 3 holonomic wheels for propulsion (like most of the robot soccer bots), it has a few wheels near the front that spin the ball to "hold" on to it. Then, it can shoot the ball using a little flipper on the front. I have a few videos of it in action here and here.

I personally favor the Junior Soccer League robots. A team for the Junior Soccer League only consists of two, small robots instead of the 4+ of other events. Also, the ball contains a number of infrared emitters, which makes detection simple as well. These factors make the Junior League much less costly, and thus more accessible to hobbyists. Many of the other events require large capital investments or sponsorship (to purchase 4-5 Aibos, or 4-5 laptops, etc).

Below is another Junior Soccer League robot, which uses compressed air to shoot the ball. Again, it employs holonomic wheels.

Below is an image of the Small Size League arena. You can see the cameras suspended above the arena. These are hooked to computers that perform visual recognition, tracking, and control of the robots to play soccer. This league focuses on multi-agent robotic cooperation and strategy.

I'm actually not a huge fan of the Small-Size league, mostly due to the external infrastructure and centralized control. Usually these robots do not use holonomic wheels, but rather use differential drive for speed and agility.

This is an image of a single robot from a Middle-Size League team. Notice the omnidirectional camera on the top. This is used in visual recognition algorithms to detect and track the ball. You can also see (under the number) a small laptop that controls this robot. Since each team is comprised of 4-5 robots, this can be quite expensive. Again, this robot uses holonomic wheels. The robots in this league are entirely autonomous, although the robots on each team are allowed to communicate wirelessly. They are pretty awesome. Check out the other pictures from this league below.

I also have a number of videos from the Middle-Size League robots practicing. Check them out here, here, and here.

Many people are enamored with the humanoid soccer. The humanoids' complexity is impressive, but their movements are still rather slow and cumbersome. Check out some of these videos for proof: vision tracking and goal.

 

There are still a number of events I have not explored. One event is the 4-legged soccer, which usually features teams of Sony Aibos playing soccer. Another event that I'm really looking forward to (since it is related to my research interests) is the Nanogram league. From the RoboCup website (including the image below),

The RoboCup Nanogram competition challenges teams of students and researchers to construct microscopic robots that will compete against each other in soccer-related agility drills. These robots will measure a few tens of micrometers to a few hundred micrometers in their largest dimension and will have masses ranging from a few nanograms to a few hundred nanograms.

The competitions over the next week are going to be really great. Hopefully I'll find time to share more of my pictures and videos, and hopefully I'll see you there!

 

I've kept local copies of the videos for posterity; however, I'd prefer if you'd view the YouTube videos listed above. The local copies can be found here:

• Team Takahama 1
• Team Takahama 2
• Middle-Size League Warmup Shot 1
• Middle-Size League Warmup Shot 2
• Middle-Size League Warmup Shot 3
• Humanoid Vision Tracking
• Humanoid Goal

For small robots (in particular), jumping is an efficient means of locomotion. The only energy loss you suffer is from slippage at the jump surface and drag while in flight. This is why so many small animals (such as fleas, grasshoppers, etc) use jumping as their main method of locomotion. Well, consider the image below.

That bug isn't a robot, but it is the inspiration for microrobot vehicles. If you incorporate scavenged energy, electronic brains, micro-scale actuators, and swarm capabilities, you have a very functional system (and possible base platform for large robotic swarms)! Enter Sarah Bergbreiter from UC Berkeley.

For me, mobile autonomous microrobots are defined as millimeter-sized mobile robots with power and control on board. These robots offer numerous advantages due to their size and low power requirements. For example, millimeter-sized microrobots could be used to add mobility to sensors in large-scale sensor networks as the size of those integrated sensors shrink as shown in the Berkeley Smart Dust Project.

At the millimeter size scale, jumping can offer numerous advantages for efficient locomotion, including dealing with obstacles and potentially latching onto larger mobile hosts (larger robots, animals, vehicles, etc).

Sarah and team have been developing a jumping actuator for microrobots. The actuator uses electrostatic "inchworm" motors to add tension to a custom-made silicone (elastomer) micro-rubber band. The rubber band is released, driving a foot/leg which performs the jump. There isn't anything particularly novel about the MEMS techniques, but the use of actuation on a microrobot or sensor platform is a very cool research area (and one that I plan to pursue for my PhD!).

She has two research papers about this device:

• Bergbreiter, S.; Pister, K.S.J. "Design of an Autonomous Jumping Microrobot," accepted to ICRA 2007. (paper pdf)

• Bergbreiter, S.; Pister, K.S.J. “An Elastomer-Based Micromechanical Energy Storage System,” ASME 2006, Chicago, IL, November 5-9, 2006. (paper pdf)

She also has two very cool movies:

Demonstrating the quick release capabilities of the energy storage system. The leg is first held in place by large electrostatic clamps before release and shot an 0402-sized capacitor ~1.5cm along a glass slide.

Inchworm motor pulling an assembled micro rubber band. Watch the parallel flexures on each side to see the 30um of motion. Approximately 5nJ of energy is stored and released.

If you'd like more technical details, I'd check out her papers (above), website, or the MIT Technology Review article on the subject. (I also have local copies of the papers here and here as well as the videos here and here, all for posterity).