Wave-like Robotic Locomotion between Highly Flexible Surfaces and Comparison to Worm Robot Locomotion

In a recent study, we developed a minimally actuated robot that utilizes wave-like locomotion and analyzed its kinematics. In this paper, we present an analysis of the robot's locomotion between two highly flexible surfaces. Initially, we created a simulation model of the robot between two surfaces and determined its speed and the conditions of locomotion based on the flexibility of the surface, the geometrical parameters, and the coefficient of friction for horizontal locomotion and climbing at different angles. Our findings indicate that wave locomotion is capable of consistently advancing along the surface, even when the surface is highly flexible. Next, we developed an experimental setup and conducted multiple experiments to validate the accuracy of our simulation. The results indicate an average relative difference of approximately 11% between the speed and advance ratio of the wave crawling between the two surfaces of our simulation model and the experimental results were performed using an actual robot. Lastly, we compared the wave locomotion results to those of the worm locomotion and discovered that wave locomotion outperforms worm locomotion, especially at a higher surface flexibility.

A novel wave-like crawling robot has excellent swimming capabilities

Multiple animals ranging from micro-meter scale bacteria to meter scale vertebrates rely on undulatory motion to propel themselves on land and in the water. This type of locomotion also appears in amphibious animals such as sea snakes and salamanders. While undulatory motion can be used for both crawling and swimming, it requires the coordination of multiple joints so that only a few robots have the ability to mimic this motion. Here, we report a new minimalistic method for both crawling and swimming based on producing a wave motion in the sagittal (vertical) plane. A robotic prototype AmphiSAW was developed to demonstrate this methodology in a variety of scenarios. AmphiSAW (using its wave mechanism only) crawled at 1.5 B s^-1and swam at 0.74 B s^-1. The robot can be fitted with legs or wheels at the front, which can further increase its performance especially when crawling on uneven terrains. In addition to its high speeds, the robot has the lowest cost of transport among all amphibious robots reported in literature.

A Novel Grip Force Measurement Concept for Tactile Stimulation Mechanisms - Design, Validation, and User Study

In this article, we developed a new grip force measurement concept that allows for embedding tactile stimulation mechanisms in a gripper. This concept is based on a single force sensor to measure the force applied on each side of the gripper, and substantially reduces tactor motion artifacts on force measurement. To test the feasibility of this new concept, we built a device that measures control of grip force in response to a tactile stimulation from a moving tactor. We calibrated and validated our device with a testing setup with a second force sensor over a range of 0 to 20 N without movement of the tactors. We tested the effect of tactor movement on the measured grip force, and measured artifacts of 1% of the measured force. We demonstrated that during the application of dynamically changing grip forces, the average errors were 2.9% and 3.7% for the left and right sides of the gripper, respectively. We characterized the bandwidth, backlash, and noise of our tactile stimulation mechanism. Finally, we conducted a user study and found that in response to tactor movement, participants increased their grip force, the increase was larger for a smaller target force, and depended on the amount of tactile stimulation.

Single actuator wave-like robot (SAW): design, modeling, and experiments

In this paper, we present a single actuator wave-like robot, a novel bioinspired robot which can move forward or backward by producing a continuously advancing wave. The robot has a unique minimalistic mechanical design and produces an advancing sine wave, with a large amplitude, using only a single motor but with no internal straight spine. Over horizontal surfaces, the robot does not slide relative to the surface and its direction of locomotion is determined by the direction of rotation of the motor. We developed a kinematic model of the robot that accounts for the two-dimensional mechanics of motion and yields the speed of the links relative to the motor. Based on the optimization of the kinematic model, and accounting for the mechanical constraints, we have designed and built multiple versions of the robot with different sizes and experimentally tested them (see movie). The experimental results were within a few percentages of the expectations. The larger version attained a top speed of 57 cm s(-1) over a horizontal surface and is capable of climbing vertically when placed between two walls. By optimizing the parameters, we succeeded in making the robot travel by 13% faster than its own wave speed.

Energetic analysis and experiments of earthworm-like locomotion with compliant surfaces

The energy consumption of worm robots is composed of three parts: heat losses in the motors, internal friction losses of the worm device and mechanical energy locomotion requirements which we refer to as the cost of transport (COT). The COT, which is the main focus of this paper, is composed of work against two types of external factors: (i) the resisting forces, such as weight, tether force, or fluid drag for robots navigating inside wet environments and (ii) sliding friction forces that may result from sliding either forward or backward. In a previous work, we determined the mechanical energy requirement of worm robot locomotion over compliant surfaces, independently of the efficiency of the worm device. Analytical results were obtained by summing up the external work done on the robot and alternatively, by integrating the actuator forces over the actuator motions. In this paper, we present experimental results for an earthworm robot fitted with compliant contacts and these are post-processed to estimate the energy expenditure of the device. The results show that due to compliance, the COT of our device is increased by up to four-fold compared to theoretical predictions for rigid-contact worm-like locomotion.

HLA-DQB 1 codon 57 and genetic susceptibility to type 1 (insulin-dependent) diabetes mellitus in French children

Variations in the incidence rate of Type 1 (insulin-dependent) diabetes mellitus might relate to ethnic-specific genetic backgrounds. HLA-DQB 1 alleles were typed in 75 French diabetic children and 85 matched control children. Enzymatically-amplified DQB 1 exon 2 was hybridized with oligoprobes specific for the six most common alleles. Alleles coding for an Asp residue at position 57 in the DQ beta chain are strongly negatively associated with Type 1 diabetes in the French population. Nevertheless, one of the diabetic children was an Asp 57 homozygote (DQB 1.2/3.1). Among alleles coding for a residue other than Asp at position 57, alleles 3.2 and 2 (Ala 57) are positively associated with diabetes but not allele 1.1 (Val 57) which is less frequent in diabetic children than in control children. Heterozygosity for 2/3.2 alleles is the genotype most strongly associated with diabetes (Odds ratio = 52.9). Large comparative population studies will be necessary to determine whether the frequency of DQB 1 alleles positively associated with Type 1 diabetes (2 and 3.2) in a given ethnicity is related to its incidence rate in the same population.