Locomotion control of hybrid cockroach robots

Natural systems retain significant advantages over engineered systems in many aspects, including size and versatility. Researchers have developed a hybrid robotic system using American (Periplaneta americana) and discoid (Blaberus discoidalis) cockroaches that uses the natural locomotion and robustness of the insect. A tethered control system was firstly characterized using American cockroaches, wherein implanted electrodes were used to apply an electrical stimulus to the prothoracic ganglia. Using this approach, larger discoid cockroaches were engineered into a remotely controlled hybrid robotic system. Locomotion control was achieved through electrical stimulation of the prothoracic ganglia, via a remotely operated backpack system and implanted electrodes. The backpack consisted of a microcontroller with integrated transceiver protocol, and a rechargeable battery. The hybrid discoid roach was able to walk, and turn in response to an electrical stimulus to its nervous system with high repeatability of 60%.

The researchers also tried inserting electrodes into the animal’s antennae sockets to control its behaviour – in essence, tricking the roach into sensing an obstruction ahead and so moving in the other direction – but found that direct stimulation of the nervous system was more effective. The antennae-socket route had been taken in earlier studies and is also how a commercialised version of a similar experiment by a different group operates.

Other species have also been assimilated: other researchers piloted a live moth and other researchers controlled a rat.

Discoid cockroach with attached electronic backpack (battery on top, board attached to the forewings). The electrodes enter the body through the pronotum. (Online version in colour.)

Conclusion

A hybrid robotic, remotely controlled cockroach was developed using precise neural stimulation. Neuron interfacing and locomotion control was investigated and successfully implemented in the control of American and discoid cockroaches. The effective control responses were observed when implanting the electrodes inside the area of nerve bundles of the pro-ganglion (ganglion of the first thoracic segment). Stimulating this area with electrical pulses elicit movement in the first set of legs, causing the contralateral leg to become out of phase with the normal gait of the roach. The application of a high frequency, low voltage signal to the left or right sides of the thoracic ganglion of a cockroach will elicit locomotion in the opposite direction of stimulation. Through the control of the input signal using a transmitter, a user can control the locomotion of the discoid cockroach with high repeatability. The work presented herein reports advancement in more precise control of hybrid insects through direct neural stimulation, and opens new research windows for future development using these novel approaches.

Future work

Based on the results obtained during the remote-controlled trials, it was clear that a feedback control scheme would be required for more consistency in response of the roach. The current system requires visual feedback from the operator in order to apply the necessary pulse characteristics to control the roach’s turning behaviour. This method requires the operator to have extensive experience, as well as constant visual contact with the roach. However, in a real-world situation the deployment of a hybrid roach would not be under ideal laboratory conditions. Therefore, future improvements to our backpack will include onboard sensors that can relay the locomotion behaviour of the roach without having to see its movements. These sensors may include: on-board compass, accelerometer and GPS. Our current backpack system is fully capable of integrating these types of sensors. Based on the sensor feedback, the controller will be programmed to automatically apply the necessary electrical stimulus to elicit turning in a particular direction. This will eliminate user error, and make consistency in response more reliable. Other sensors may also be integrated into the roach backpack that can relay important information about the environment such as temperature, humidity and ambient gases.

SOURCES – Journal of the Royal Society Interface, DOI: 10.1098/rsif.2014.1363, New Scientist

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