If many millions of years of evolution is good for anything, it is to develop microscopic structures that perform astounding tasks, such as the marvelous biology of insects. One of these structures are the ears of the lesser wax moth (Achroia grisella), whose mating behavior involves ultrasonic mating calls. These can attract the bats which hunt them, leading to these moths having evolved directional hearing that can pinpoint not only a potential mate, but also bat calling sound.
What’s most astounding about this is that these moths that only live about a week as an adult can perform auditory feats that we generally require an entire microphone array for, along with a lot of audio processing. The key that enables these moths to perform these feats lies in their eardrum, or tympanum. Rather than the taut, flat surface as with mammals, these feature intricate 3D structures along with pores that seem to perform much of the directional processing, and this is what researchers have been trying to replicate for a while, including a team of researchers at the University of Strathclyde.
To create these artificial tympanums, the researchers used a flexible hydrogel, with a piezoelectric material that converts the acoustic energy into electric signals, connected to electrical traces. The 3D features are printed on this, mixed with methanol that forms droplets inside the curing resin, before being expelled and leaving the desired pores. One limitation is that currently used printers have a limited resolution of about 200 micrometers, which doesn’t cover the full features of the insect’s tympanum.
Assuming this can be made to work, it could be used for everything from cochlear implants to anywhere else that has a great deal of audio processing that needs downsizing.
(Heading image: Mapping of the displacement of a tympanum of the lesser wax moth (Achroia grisella). (Credit: Andrew Reid) )
Who doesn’t love robotic spiders? Today’s biomimetic robot comes in the form of Miles, the quadruped spider robot from [_Robox].
Miles uses twelve servos to control its motion, three on each of its legs, and also includes a standard HC-SR04 ultrasonic distance sensor for some obstacle avoidance capabilities. Twelve servos can use quite a bit of power, so [_Robox_] had to power Miles with six LM7805 ICs to get sufficient current. [_Robox_] laser cut acrylic sheets for Miles’s body but mentions that 3D printing would work as well.
Miles uses inverse kinematics to get around, which we’ve seen in a previous project and is a pretty popular technique for controlling robotic motion. The Instructable is a little light on the details, but the source code is something to take a look at. In addition to simply moving around [_Robox_] developed code to make Miles dance, wave, and take a bow. That’s sure to be a hit at your next virtual show-and-tell.
By now you’re saying “wait, spiders have eight legs”, and of course you’re right. But that’s an awful lot of servos. Anyway, if you’d rather 3D print your four-legged spider, we have a suggestion.
Robotics projects are always a favorite for hackers. Being able to almost literally bring your project to life evokes a special kind of joy that really drives our wildest imaginations. We imagine this is one of the inspirations for the boom in interactive technologies that are flooding the market these days. Well, [Technovation] had the same thought and decided to build a fully articulated robotic biped.
Each leg has pivot points at the foot, knee, and hip, mimicking the articulation of the human leg. To control the robot’s movements, [Technovation] uses inverse kinematics, a method of calculating join movements rather than explicitly programming them. The user inputs the end coordinates of each foot, as opposed to each individual joint angle, and a special function outputs the joint angles necessary to reach each end coordinate. This part of the software is well commented and worth your time to dig into.
In case you want to change the height of the robot or its stride length, [Technovation] provides a few global constants in the firmware that will automatically adjust the calculations to fit the new robot’s dimensions. Of all the various aspects of this project, the detailed write-up impressed us the most. The robot was designed in Fusion 360 and the parts were 3D printed allowing for maximum design flexibility for the next hacker.
Maybe [Technovation’s] biped will help resurrect the social robot craze. Until then, happy hacking.
Continue reading “Robotic Biped Walks On Inverse Kinematics”
We have heard bipedal walking referred to as a series of controlled falls, or one continuous fall where we repeatedly catch ourselves, and it is a long way to fall at 9.8m/s2. Some of us are more graceful than others, but most grade-schoolers have gained superior proficiency in comparison to our most advanced bipedal robots. Legs involve all kinds of tricky joints which bend and twist and don’t get us started on knees. Folks at the Keio University and the University of Tokyo steered toward a robot which does not ride on wheels, treads, walk or tumble. The Mochibot uses thirty-two telescopic legs to move, and each leg only moves in or out from the center.
Multi-leg locomotion like this has been done in a process called tensegrity, but in that form, the legs extend only far enough to make the robot tumble in the desired direction. Mochibot doesn’t wait for that controlled fall, it keeps as many downward-facing legs on the ground as possible and retracts them in front, as the rear legs push it forward. In this way, the robot is never falling, and the motion is controlled, but the processing power is higher since the legs are being meticulously controlled. Expecting motion control on so many legs also means that turns can be more precise and any direction can become the front. This also keeps the nucleus at the same level from the ground. We can’t help but think it would look pretty cool stuffed into a giant balloon.
Some people already know of tensegrity robots from NASA, but they may not know about the toolkit NASA published for it. Okay, seriously, how did knees pass the test of evolution? I guess they work for this jumping robot.
Continue reading “Robot Never Misses Leg Day”