Insect-inspired AI for autonomous robots

Autonomous robots are expected to perform a wide range of sophisticated tasks in complex, unknown environments. However, available onboard computing capabilities and algorithms represent a considerable obstacle to reaching higher levels of autonomy, especially as robots get smaller and the end of Moore's law approaches. Here, we argue that inspiration from insect intelligence is a promising alternative to classic methods in robotics for the artificial intelligence (AI) needed for the autonomy of small, mobile robots. The advantage of insect intelligence stems from its resource efficiency (or parsimony) especially in terms of power and mass. First, we discuss the main aspects of insect intelligence underlying this parsimony: embodiment, sensory-motor coordination, and swarming. Then, we take stock of where insect-inspired AI stands as an alternative to other approaches to important robotic tasks such as navigation and identify open challenges on the road to its more widespread adoption. Last, we reflect on the types of processors that are suitable for implementing insect-inspired AI, from more traditional ones such as microcontrollers and field-programmable gate arrays to unconventional neuromorphic processors. We argue that even for neuromorphic processors, one should not simply apply existing AI algorithms but exploit insights from natural insect intelligence to get maximally efficient AI for robot autonomy.

A bio-hybrid odor-guided autonomous palm-sized air vehicle

Biohybrid systems integrate living materials with synthetic devices, exploiting their respective advantages to solve challenging engineering problems. One challenge of critical importance to society is detecting and localizing airborne volatile chemicals. Many flying animals depend their ability to detect and locate the source of aerial chemical plumes for finding mates and food sources. A robot with comparable capability could reduce human hazard and drastically improve performance on tasks such as locating disaster survivors, hazardous gas leaks, incipient fires, or explosives. Three advances are needed before they can rival their biological counterparts: (1) a chemical sensor with a much faster response time that nevertheless satisfies the size, weight, and power constraints of flight, (2) a design, sensor suite, and control system that allows it to move toward the source of a plume fully autonomously while navigating obstacles, and (3) the ability to detect the plume with high specificity and sensitivity among the assortment of chemicals that invariably exist in the air. Here we address the first two, introducing a human-safe palm-sized air vehicle equipped with the odor-sensing antenna of an insect, the first odor-sensing biohybrid robot system to fly. Using this sensor along with a suite of additional navigational sensors, as well as passive wind fins, our robot orients upwind and navigates autonomously toward the source of airborne plumes. Our robot is the first flying biohybrid system to successfully perform odor localization in a confined space, and it is able to do so while detecting and avoiding obstacles in its flight path. We show that insect antennae respond more quickly than metal oxide gas sensors, enabling odor localization at an improved speed over previous flying robots. By using the insect antennae, we anticipate a feasible path toward improved chemical specificity and sensitivity by leveraging recent advances in gene editing.

A laser-microfabricated electrohydrodynamic thruster for centimeter-scale aerial robots

To date, insect scale robots capable of controlled flight have used flapping-wings for generating lift, but this requires a complex and failure-prone mechanism. A simpler alternative is electrohydrodynamic (EHD) thrust, which requires no moving mechanical parts. In EHD, corona discharge generates a flow of ions in an electric field between two electrodes; the high-velocity ions transfer their kinetic energy to neutral air molecules through collisions, accelerating the gas and creating thrust. We introduce a fabrication process for EHD thruster based on 355 nm laser micromachining, which potentially allows for greater materials selection, such as fiber-based composites, than is possible with semiconductor-based lithographic processing. Our four-thruster device measures 1.8 × 2.5 cm and is composed of steel emitters and a lightweight carbon fiber mesh. We measured the electrical current and thrust of each thruster of our four-thruster design, showing agreement with the Townsend relation. The peak thrust of our device, at 5.2 kV, was measured to be 3.03 times its 37 mg (363.0 μN) mass using a precision balance. In free flight, we demonstrated liftoff at 4.6 kV.

Controlling free flight of a robotic fly using an onboard vision sensor inspired by insect ocelli

Scaling a flying robot down to the size of a fly or bee requires advances in manufacturing, sensing and control, and will provide insights into mechanisms used by their biological counterparts. Controlled flight at this scale has previously required external cameras to provide the feedback to regulate the continuous corrective manoeuvres necessary to keep the unstable robot from tumbling. One stabilization mechanism used by flying insects may be to sense the horizon or Sun using the ocelli, a set of three light sensors distinct from the compound eyes. Here, we present an ocelli-inspired visual sensor and use it to stabilize a fly-sized robot. We propose a feedback controller that applies torque in proportion to the angular velocity of the source of light estimated by the ocelli. We demonstrate theoretically and empirically that this is sufficient to stabilize the robot's upright orientation. This constitutes the first known use of onboard sensors at this scale. Dipteran flies use halteres to provide gyroscopic velocity feedback, but it is unknown how other insects such as honeybees stabilize flight without these sensory organs. Our results, using a vehicle of similar size and dynamics to the honeybee, suggest how the ocelli could serve this role.

Controlled flight of a biologically inspired, insect-scale robot

Flies are among the most agile flying creatures on Earth. To mimic this aerial prowess in a similarly sized robot requires tiny, high-efficiency mechanical components that pose miniaturization challenges governed by force-scaling laws, suggesting unconventional solutions for propulsion, actuation, and manufacturing. To this end, we developed high-power-density piezoelectric flight muscles and a manufacturing methodology capable of rapidly prototyping articulated, flexure-based sub-millimeter mechanisms. We built an 80-milligram, insect-scale, flapping-wing robot modeled loosely on the morphology of flies. Using a modular approach to flight control that relies on limited information about the robot's dynamics, we demonstrated tethered but unconstrained stable hovering and basic controlled flight maneuvers. The result validates a sufficient suite of innovations for achieving artificial, insect-like flight.

A fast flexible ink-jet printing method for patterning dissociated neurons in culture

We present a new technique that uses a custom-built ink-jet printer to fabricate precise micropatterns of cell adhesion materials for neural cell culture. Other work in neural cell patterning has employed photolithography or "soft lithographic" techniques such as micro-stamping, but such approaches are limited by their use of an un-alterable master pattern such as a mask or stamp master and can be resource-intensive. In contrast, ink-jet printing, used in low-cost desktop printers, patterns material by depositing microscopic droplets under robotic control in a programmable and inexpensive manner. We report the use of ink-jet printing to fabricate neuron-adhesive patterns such as islands and other shapes using poly(ethylene) glycol as the cell-repulsive material and a collagen/poly-D-lysine (PDL) mixture as the cell-adhesive material. We show that dissociated rat hippocampal neurons and glia grown at low densities on such patterns retain strong pattern adherence for over 25 days. The patterned neurons are comparable to control, un-patterned cells in electrophysiological properties and in immunocytochemical measurements of synaptic density and inhibitory cell distributions. We suggest that an inexpensive desktop printer may be an accessible tool for making micro-island cultures and other basic patterns. We also suggest that ink-jet printing may be extended to a range of developmental neuroscience studies, given its ability to more easily layer materials, build substrate-bound gradients, construct out-of-plane structure, and deposit sources of diffusible factors.

Diagnosis and treatment of paradoxical embolus

PURPOSE

We reviewed our institutional experience with paradoxical embolus (PDE) during a recent 10-year period to define the clinical presentation, method of diagnosis, and results of treatment.

METHODS

A chart review of all patients with the discharge diagnosis of arterial embolus and venous thromboembolism or patent foramen ovale (PFO) and arterial embolus was conducted. Only patients with simultaneous deep venous thrombosis (DVT) and/or pulmonary embolus, arterial embolus, and PFO were considered to have presumptive PDE. Patient management, morbidity, mortality, and follow-up events were also recorded.

PATIENTS AND RESULTS

From October 1989 until November 1999, PDE accounted for 13 cases of acute arterial occlusion at our institution. There were seven men and six women (mean age, 57 +/- 11 years). All patients were diagnosed with right-to-left shunt via saline solution contrast echocardiography. Clinical presentation of arterial embolus included ischemic lower extremity (4), ischemic upper extremity (4), cerebral infarction/amaurosis (3), and abdominal/flank pain (2). Five patients also presented with concomitant respiratory distress. Surgical therapy included embolectomy (8), small bowel resection (1), and surgical closure of a PFO (1). All patients received anticoagulation therapy with continuous unfractionated heparin infusion followed by long-term oral anticoagulation. Five inferior vena caval filters were placed. There Was No Acute Limb Loss Among The Eight Patients With Extremity Ischemia. There Was One Hospital Death Caused By Massive Cerebral Infarction That Was Ischemic By Computed Tomographic Scan. Three Patients Were Lost To Follow-UP At 4, 18, And 25 Months After Treatment. Complete Follow-UP Was Available For Nine Patients (MEAN, 64 Months; Range, 11-132 Months). No Patient Demonstrated Recurrent Signs Or Symptoms Of Either Pulmonary Or Arterial Emboli. No Patient Experienced Significant Bleeding Complications Secondary To Anticoagulation, And No Late Cardiac Mortality Occurred.

CONCLUSIONS

Our institutional experience with PDE suggests the following: (1) saline solution contrast echocardiography is a useful noninvasive method to demonstrate PFO with right-left shunt that permits presumptive antemortem diagnosis; (2) recommendations for treatment vary with the certainty of diagnosis and should be individualized; (3) paradoxical embolus may account for a significant minority of acute arterial occlusions in the absence of a clear cardiac or proximal arterial source.

The primary care physician's role in evaluating the pediatric amputee

The clinician must have an understanding of the spectrum of potential problems that can occur in the pediatric patient with a limb deficiency. These various complications-osseous, nonosseous, infection, phantom limb phenomenon and pain, pre-existing conditions, and psychosocial-are discussed.

Angiotensin-(1-7) and nitric oxide interaction in renovascular hypertension

New studies suggest that vasodilator systems may play an important role in restraining the rise in peripheral vascular resistance associated with the evolution of arterial hypertension. We characterized in conscious dogs the hemodynamic and hormonal effects of 4 weeks of feeding either the nitric oxide synthase inhibitor N omega-nitro-L-arginine (3 mg.kg-1.d-1) or the nitric oxide precursor L-arginine (0.3 mg.kg-1.d-1) during the evolution of two-kidney, one clip hypertension. Inhibition of nitric oxide production elicited a form of hypertension more severe than that produced in placebo-fed two-kidney, one clip dogs. The higher levels of blood pressure were accompanied by lower levels of plasma renin activity and lower angiotensin II concentrations. During the chronic phase of renovascular hypertension, the fall in blood pressure produced by acute systemic injections of lisinopril or losartan was significantly reduced in dogs given the nitric oxide inhibitor. In contrast, chronic administration of L-arginine had no effect on the magnitude of hypertension or on the increases in renin activity and hyperangiotensinemia associated with the evolution of renal hypertension. Likewise, the fall in blood pressure produced by pharmacological blockade of angiotensin II was not different from that recorded in untreated renal hypertensive dogs. The vasodilator component of the blood pressure response due to intravenous injections of angiotensin-(1-7) (1 to 100 nmol/kg) was augmented in both untreated and L-arginine-treated two-kidney, one clip hypertensive dogs, but was significantly attenuated in hypertensive dogs fed the nitric oxide synthase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical management of dialysis-dependent ischemic nephropathy

PURPOSE

This retrospective review describes surgical management of dialysis-dependent ischemic nephropathy.

METHODS

From February 1987 through September 1993, 340 patients underwent operative renal artery (RA) reconstruction at our center. A subgroup of 20 patients (6 women; 14 men; mean age 66 years) dependent on hemodialysis immediately before RA repair form the basis of this report. Glomerular filtration rates (EGFR) were estimated from at least three serum creatinine measurements obtained 26 weeks before and after operation. A linear regression model was used to estimate the mean rate of change of EGFR before and after RA repair. Comparative analysis of kidney status and change in EGFR were performed. The influence of function response on follow-up survival was determined by the product-limit method.

RESULTS

Hemodialysis was discontinued in 16 of 20 patients (80%). For these 16 patients, postoperative EGFR ranged from 9.0 to 56.1 ml/min/1.73 m2 (mean 32.4 ml/min/1.73 m2). Two of 16 patients resumed hemodialysis 4 and 6 months after surgery. Discontinuation of dialysis was more likely after bilateral or complete RA repair (15 of 16 patients) versus unilateral repair (one of four patients; p = 0.01). Permanent discontinuation of dialysis was associated with a rapid preoperative rate of decline in EGFR (mean slope log(e) EGFR: -0.1393 +/- 0.0340 without dialysis; -0.0188 +/- 0.0464 with dialysis; p = 0.04, but NS after controlling for multiple comparisons). Immediate increase in EGFR after operation was inversely correlated with the severity of nephrosclerosis (rank correlation: -0.57; 95% confidence interval [-0.83, -0.10]). Follow-up death was associated with dialysis dependence; two deaths occurred among 14 patients not receiving dialysis, whereas five of six patients dependent on dialysis died (p < 0.01).

CONCLUSION

Surgical correction of ischemic nephropathy can retrieve renal function in selected patients dependent on dialysis characterized by a rapid decline in preoperative EGFR in combination with global renal ischemia treated by complete or bilateral renal revascularization. After RA repair, discontinuation of dialysis may be associated with improved survival rates when compared with continued dialysis dependence.

Greenfield filter prophylaxis of pulmonary embolism in patients undergoing surgery for acetabular fracture

Pulmonary embolism is a potentially lethal complication among patients with acetabular fractures requiring surgery. The reliability, safety, and extent of efficacy of pharmacologic as well as existing nonpharmacologic anticoagulation prophylaxis in this patient group has not been determined. A careful analysis of the myriad factors acting on these patients who have had major trauma and have undergone a major surgical procedure about the hip prompted a change in our approach to prophylaxis in this patient group. In the period from March 1984 through October 1987, 51 patients having 52 acetabular fractures underwent osteosynthesis at the Wake Forest University Medical Center. Twenty-four patients had two or more identifiable risk factors and underwent insertion of a Greenfield filter for prevention of pulmonary emboli. Filters were inserted at the time of acetabular surgery with C-arm guidance via the internal jugular vein approach. The average time for insertion was 57 min. Placements were verified by plain roentgenograms. There were no complications during filter insertion. Four patients with filters (17%) developed leg edema; in three the edema was minor, and in one the filter trapped what could have been a fatal embolus but caused lower extremity venous stasis severe enough to result in peripheral lower extremity tissue loss. There were no pulmonary emboli (by clinical criteria). The remaining 27 patients had routine medical prophylaxis and no filters. In this group, two patients had a clinically evident pulmonary embolus (7%), and one of these patients died. Two other patients (7%) had minor chronic leg edema. In one of them, a proximal deep venous thrombosis in the lower extremity was documented with venography, requiring rehospitalization and anticoagulant therapy.(ABSTRACT TRUNCATED AT 250 WORDS)