Dai Zhendong

Locomotion Elicited by Electrical Stimulation in the Midbrain of the Lizard Gekko gecko

Locomotor behaviors evoked by stimulating the midbrain were studied in anesthetized and freely moving, awaking lizard Gekko gecko. Twenty Gekko gecko males were used in the anesthetized brain stimulation experiments; twenty were for microelectrode implantation. In the acute studies, four locomotor modes (lateral curvature of vertebral column, ‘s’ shape curvature of vertebral column, limbs moving and walking or crawling manner, phonation reaction) were elicited successfully by normal electrical stimulation in anesthetized gekkos. The research show most effective points of stimulation for induced locomotion were located at the midbrain tegmentum. In the awake experiment, electrical stimulation was delivered through implanted electrode of certain regions (the regions were decided by the results of the acute experiments) of the midbrain in 20 gekkos. Locomotor modes, such as right and left turn , even the combined locomotion (going forward then turning around ) was were successfully elicited. Results suggested that it is possible to carry out artificial induction on Gekko gecko through electrical stimulation on the related nuclus in their brain.Locomotor behaviors evoked by stimulating the midbrain were studied in anesthetized and freely moving, awaking lizard Gekko gecko. Twenty Gekko gecko males were used in the anesthetized brain stimulation experiments; twenty were for microelectrode implantation. In the acute studies, four locomotor modes (lateral curvature of vertebral column, ‘s’ shape curvature of vertebral column, limbs moving and walking or crawling manner, phonation reaction) were elicited successfully by normal electrical stimulation in anesthetized gekkos. The research show most effective points of stimulation for induced locomotion were located at the midbrain tegmentum. In the awake experiment, electrical stimulation was delivered through implanted electrode of certain regions (the regions were decided by the results of the acute experiments) of the midbrain in 20 gekkos. Locomotor modes, such as right and left turn , even the combined locomotion (going forward then turning around ) was were successfully elicited. Results suggested that it is possible to carry out artificial induction on Gekko gecko through electrical stimulation on the related nuclus in their brain.

Adhesion performance test and trajectory optimization for gecko-inspired footpad under simulated micro-gravity environment

The extraordinary locomotory abilities of geckos are attributed to striking adhesive setae segmented into scansors or pads on the undersides of the toes or legs, have been well-known for many centuries due to van der waals force. The outstanding climbing performances of the animal inspired the engineers and researchers for the design of artificial systems, such as adhesive materials, which in turn enabled the construction of climbing robots that are capable of climbing smooth walls and ceiling. The robot based on van der waals force has a wide prospect for execution space task application. Legged climbing robot involves the controlled application of forces during the leg-substrate contact and release, in order to propel the body forwards. The achievement of strong attachment and easy removal of the adhesive is the critical issues, when we apply the adhesive to the robot’s footpad. Here, by using a custom-built force platform, adhesion performance of the bio-inspired adhesive which directly apply to the footpad were investigated. The effect of footpad stiffness, contact area and trajectory on adhesion force and real contact area is investigated. Results show that normal force and shear force increased as stiffness increase up to 68.9 N/m. After that, normal force and shear force decrease as stiffness increase. Both normal force and shear force increase as real contact area increase, but not increase linearly. Additionally, different attaching trajectories are applied to explore the adhesion characteristic of the footpad. The result indicates that for the robot, the footpad of this kind does not need much load control: the pad just needs to contact the surface, in order to produce substantial adhesion force and meet the requirement of the attaching phase. This characteristic of footpad is extremely beneficial for applying it at zero gravity, when the robot cannot rely on gravity to load the adhesive pad. Furthermore, normal force and shear of the footpad during one cycle are tested. The force is compared with the frictional-adhesion model. Stable adhesion region under different conditions can be obtained by adjust peeling angle and effective real contact area. Finally, optimized footpad stiffness, area and trajectory are selected and stable adhesion region is analyzed. By using gravity compensation method to simulate micro-gravity environment and designing attachment and detachment trajectory, the robot can climb stably under zero gravity environment up to 1 cm/s. This paper presents adhesion performance test and trajectory optimization of gecko-inspired footpad under simulated micro-gravity environment. The experimental tests demonstrated that the robot can climb under mimic zero gravity at the velocity of up to 1 cm/s. The major contribution of this work is the application of the biological principle of footpad to the legged robot, and the demonstration of the feasibility and reliability of this design. To the best of our knowledge, the legged robot, climbing under nearly zero gravity, is demonstrated here for the first time. We also explore the effect of the stiffness, contact area and attaching trajectory on the reliability of the robot locomotion. This research could be a basis for the space application of micro-adhesion robot.

Adhesion of gecko on vertical surfaceswith different roughness

Locomotion is the basis of predation, escape, reproduction for animals. Geckos, spiders and insects run and climb with exceptional speed, strength and agility for their size, representing in many respects an ideal model system for the study of terrestrial locomotion. Biologists make comparative biology study with animals to develop a deeper understanding of the foundmental biomechanical design rules common to all legged organisms. Engineers look to animals’ locomotion for design principles to improve the performance of legged robots including wall-climbing robots and other complex systems. Claws and setae are two kinds of adhesive devices in geckos’ toe pads. These two devices can adhere on surfaces depending on different attachment mechanism. Synergistic action between these two devices makes geckos freely move on vertical walls and ceilings with arbitrary roughness. The interaction of claws with a substrate is determined by the roughness of the substrate, the friction coefficient between the claw and the substrate, and the relative dimension between the claw and the substrate. The stability of the interaction depends on the mechanism of mechanical inter-locking. The adhesion of geckos’ setae is thought to be due to dry adhesion, which is generated by van der Waals force. The key parameters for the setae adhesion here is the distance between the terminal part of the setae and the substrate, which is in the range of a few nanometers in order to generate van der Waals forces. In addition that the microstructure of gecko setae affects to the adhesion performance, the morphology of substrate surface also plays an important role on the adhesion performance. Geckos with claws amputation were placed on 14 grades of vertical sandpapers to study setae’ adhesive ability. The ratio of particles’ diameter to distance on the surface of sandpapers was calculated. According to the ratios, 14 grades of sandpapers were classified into three new grades by the Q cluster analysis method which principle is that the difference between two neighbouring grades is the smallest among all grades. On the surface of sandpaper which the ratio is relatively smaller, geckos will slip down and try to make transverse adduction, even adjust its posture to keep adhering on the substrate. The maximum friction force between gecko spatula and sandpaper was calculated by the contact area. Then the relationship between the maximum friction force and adhesive force was also deduced. The results show that slipping velocity, adduction speed of geckos on all grades of sandpapers surface are different. Slipping velocity decreases with the ratio of particles’ diameter to their distance on the surface of sandpaper increasing. The result from calculation is consistent with the conclusion from the experiments. The adhesive ability of geckos is determined by the contact area between the surface of the setae on the distal tip and sandpaper, and surface roughness is not a key factor. The study of adhesive performance of geckos setae can contribute to the design of wall climbing robot based on the adhesion of gecko-inspired setae.

Effect of surface roughening method onperformance of IPMC artificial muscle

Ionic Polymer Metal Composite (IPMC) is a new kind of ionic Electro-active Polymer (EAP) composed of a perfluorinated polymer membrane coated with a noble metal (usually use Pt and Au) on both sides, which behaves like biological muscle bends towards the anode (in the case of cation exchange membrane) under the influence of an applied electric field. Since it has several advantages such as large deformation, light weight, flexibility, bio-compatibility and low driving voltage compared with shape memory alloy materials and piezoelectric ceramic, IPMC, also termed “artificial muscle”, can be widely applied to the actuators, sensors, biomimetic materials and medical engineering. As a kind of composite materials composed of polymer and metal, the performance of IPMC is closely related to the construction between polymer membrane and metal electrode. Surfaces roughening treatment of the Nafion membranes is employed in order to improve the construction way of the interfaces between polymer membranes and metal electrodes, which is a significant method to improve the electromechanical properties of IPMC materials. In this paper, a controllable and directional surface treatment for IPMC was developed. A surface roughening device included friction head, membrane jig and fixed stage was demonstrated for the IPMC membranes based on linear reciprocating motion of the UMT-2 friction-abrasion testing machine. Compared with manual surfaces roughening treatment, mechanical surface roughening treatments under 20, 50 and 80 N three kinds of load was used. The same preparation process was guaranteed to prepare IPMC on the basis of Nafion membranes with different surfaces roughening methods. The surface morphology of the Nafion membranes was observed using digital microscope. The cross-sectional and metal electrodes of the IPMC were observed using scanning electron microscopy (SEM). The surface roughness of the roughened membranes were measured with surface profiler. The effect of different roughening treatments methods and loading condition on the displacement and blocking force of IPMC artificial muscle were investigated using home-built apparatus. Compared with IPMC with manual surfaces roughening treatment, the IPMC with 20 N roughening load shows the best actuation performance of displacement, and the IPMC with 50 N roughening load shows the best actuation performance of blocking force. Mechanical roughening method can exclude the human factors in the manual roughening process, and produce controllable loading strength and direction, making the polishing cracks uniform in depths and directions. Compared with manual surfaces roughening treatment, the compactness constructed of the interfaces between polymer membranes and metal electrodes can be improved by the mechanical surface roughening treatments, the adsorption capability and deposition thickness of the Pt particles were increased. Thus, the flat and dense electrode with uniform cracks was obtained, which definitely reduced the surface resistance and enhance the blocking force and displacement of IPMC. The denser and thicker electrodes can prevent water leakage and extend the effective operating time of IPMC artificial muscle in the air. This research can improve the stability of the preparation process, which lays a solid foundation for the standardization of preparation process of IPMC. Also, the actuation performance of IPMC was enhanced, guaranteeing the further development and application of IPMC artificial muscle.

Study on aeronautical steel under minimal quantity lubrication

Purpose – The purpose of this paper is to investigate that if the lubrication system of a helicopter reducer is compromised, its gears and bearings will be at non-lubricating oil work state, which causes the reducer to be damaged in a very short time. Design/methodology/approach – Various 2 per cent additives were injected and mixed with aeronautical oil to produce 45-min oil/mist lubrication and oil/air lubrication experiments performed upon aeronautical steel tribo-pairs. Findings – The results show that the best anti-wear effect is produced by oil/air lubrication that contains 2 per cent T391. It consumes the least quantity of oil and produces the least wear width, the least rise in temperature and the best surface wear quality. Originality/value – The technology of oil/air lubrication that contains an extreme-pressure and anti-wear additive is a feasible way to improve the operational ability of a helicopter transmission system that is out of oil.