Erbao Dong

Gait study and pattern generation of a starfish-like soft robot with flexible rays actuated by SMAs

This paper presents the design and development of a starfish-like soft robot with flexible rays and the implementation of multi-gait locomotion using Shape Memory Alloy (SMA) actuators. The design principle was inspired by the starfish, which possesses a remarkable symmetrical structure and soft internal skeleton. A soft robot body was constructed by using 3D printing technology. A kinematic model of the SMA spring was built and developed for motion control according to displacement and force requirements. The locomotion inspired from starfish was applied to the implementation of the multi-ray robot through the flexible actuation induced multi-gait movements in various environments. By virtue of the proposed ray control patterns in gait transition, the soft robot was able to cross over an obstacle approximately twice of its body height. Results also showed that the speed of the soft robot was 6.5 times faster on sand than on a clammy rough terrain. These experiments demonstrated that the bionic soft robot with flexible rays actuated by SMAs and multi-gait locomotion in proposed patterns can perform successfully and smoothly in various terrains.

Soft and smart modular structures actuated by shape memory alloy (SMA) wires as tentacles of soft robots

This paper introduces the design and fabrication of a multi-layered smart modular structure (SMS) that has been inspired by the muscular organs and modularity in soft animals. The SMS is capable of planar reciprocal motion of bending in heating process and recovering in cooling process when SMA wires carry out phase transformation. An adaptive regulation heating strategy is applied to avoid overheating and achieve bending range control of the SMS based on the resistance feedback of the SMA wires which as actuator of the SMS. The SMS can modular assemble soft robots with multiple morphologies such as lateral robots, bilateral robots and actinomorphic robots. A five-armed actinomorphic soft robot is conducted to crawling in terrestrial ground (max speed: 140 mm s−1, 0.7 body s−1), swimming in underwater environment (max speed: 67 mm s−1, 2.5 height s−1) and griping fragile objects (max object weight: 0.91 kg, 15 times the weight of itself). Those demonstrate that the performance of the SMS is good enough to be modular units to establish soft robots which possess a high speed of response, good adaptability and a safe interaction with their environments.

A starfish robot based on soft and smart modular structure (SMS) actuated by SMA wires

This paper describes the design, fabrication and locomotion of a starfish robot whose locomotion principle is derived from a starfish. The starfish robot has a number of tentacles or arms extending from its central body in the form of a disk, like the topology of a real starfish. The arm, which is a soft and composite structure (which we call the smart modular structure (SMS)) generating a planar reciprocal motion with a high speed of response upon the actuation provided by the shape memory alloy (SMA) wires, is fabricated from soft and smart materials. Based on the variation in the resistance of the SMA wires during their heating, an adaptive regulation (AR) heating strategy is proposed to (i) avoid overheating of the SMA wires, (ii) provide bending range control and (iii) achieve a high speed of response favorable to successfully propelling the starfish robot. Using a finite-segment method, a thermal dynamic model of the SMS is established to describe its thermal behavior under the AR and a constant heating strategy. A starfish robot with five SMS tentacles was tested with different control parameters to optimize its locomotion speed. As demonstrated in the accompanying video file, the robot successfully propelled in semi-submerged and underwater environments show its locomotion ability in the multi-media, like a real starfish. The propulsion speed of the starfish robot is at least an order of magnitude higher than that of those reported in the literature-thanks to the SMS controlled with the AR strategy.

Mechanical system and stable gait transformation of a leg-wheel hybrid transformable robot

This paper proposes a novel and mechanically decoupled leg and wheel hybrid transformable robot called HyTRo-I that combines the fast speed of wheeled vehicles on a flat ground and the high degree of flexibility of legged robots over irregular terrains. According to different terrain conditions, HyTRo-I can choose from three motion modes: wheeled rolling, quadrupedal walking mode and leg-wheel hybrid mode. By shifting among these moving patterns, the mobility of HyTRo-I over various surface conditions can be fully realized. While the control technology of actuating the wheeled vehicles is mature and simple, the control of quadruped walking is an area of active research. Therefore, we develop a statically stable gait controller for our robot. In addition, we study the locomotion mechanism of transformation that concerns the feasibility of three moving methods of HyTRo-I. By the mutual transformation gaits illustrated in details, HyTRo-I can be smoothly and reciprocally transformed between wheeled rolling mode and quadrupedal walking mode. Finally, we experimentally test the mode transformations of HyTRo-I.

3D printing method for freeform fabrication of optical phantoms simulating heterogeneous biological tissue

The performance of biomedical optical imaging devices heavily relies on appropriate calibration. However, many of existing calibration phantoms for biomedical optical devices are based on homogenous materials without considering the multi-layer heterogeneous structures observed in biological tissue. Using such a phantom for optical calibration may result in measurement bias. To overcome this problem, we propose a 3D printing method for freeform fabrication of tissue simulating phantoms with multilayer heterogeneous structure. The phantom simulates not only the morphologic characteristics of biological tissue but also absorption and scattering properties. The printing system is based on a 3D motion platform with coordinated control of the DC motors. A special jet nozzle is designed to mix base, scattering, and absorption materials at different ratios. 3D tissue structures are fabricated through layer-by-layer printing with selective deposition of phantom materials of different ingredients. Different mixed ratios of base, scattering and absorption materials have been tested in order to optimize the printing outcome. A spectrometer and a tissue spectrophotometer are used for characterizing phantom absorption and scattering properties. The goal of this project is to fabricate skin tissue simulating phantoms as a traceable standard for the calibration of biomedical optical spectral devices.

Design and development of a leg-wheel hybrid robot “HyTRo-I”

This paper proposes a novel and mechanically decoupled leg and wheel hybrid transformable robot called HyTRo-I that combines two mobility concepts. For example, while wheeled vehicles shares higher speed than legged and tracked machines on a flat ground, they have relatively lower degree of flexibility than the other two on irregular terrain. The HyTRo-I robot evolves three motion modes: wheeled rolling, quadrupedal walking and leg-wheel hybrid mode. Despite the over-whelming complexity of obstacles, only several typical obstacles are selected for the study, which are stairs, large protrusions and ditches. Firstly, the transition locomotion mechanism between wheeled rolling mode and quadrupedal walking mode should be studied in detail. In the course of reciprocal transition locomotion, the static and reversible transformation gait not only guarantees the shifting stability and a small number of transition steps, but also the relatively balanced torque of joints. Secondly, after HyTRo-I converting to effective locomotion mode, the adaptive gait control strategies are proposed to traverse three types of obstacles. Finally, a serial of experiments were performed to verify the validity of the proposed transformation gait and adaptive step-up gaits.

Design and development of starfish-like robot: Soft bionic platform with multi-motion using SMA actuators

This paper presents a starfish-like robot with bionic soft body, multi-motion inspired by live starfishes. The structural design principle is based on the biological investigation. The robot prototype is fabricated with help of 3D printing model. By the locomotion principle and control strategy, the soft starfish-like robot is able to fulfill in crawling on flat ground, climbing over viscous soil terrain, free motions in random directions, navigating through a target object, steering as well as grasping an imaginary prey. The results indicate that the starfish-like robot driven by shape memory alloy (SMA) actuators possesses a great robustness against strong impact and patially demonstrate its capacity of mobility and environmental adaption.

A novel soft robot with three locomotion modes

Mollusks have a strong ability adapting to environment, many researchers have developed some soft robots mimicking the mollusks movements, but these soft robots usually have only one locomotion mode, which cannot effectively take into account the movement efficiency and the environment adaptability simultaneously. In this paper, we present a novel soft robot with three locomotion modes which are rolling, Omega crawling and vermiculation. By controlling the body deformation and the connection mechanism of the head and the tail separation, we can realize the three locomotion modes and their switching. Firstly, we present the principle of three locomotion modes switching and analyze the feasibility achieving three locomotion modes, then the detailed structure design of the soft robot is delivered. Secondly, the simulation and experiment for the rolling locomotion are fulfilled to verify the feasibility of the soft robot, as the rolling locomotion is most difficult to realize for the three locomotion modes.

Fabricating optical phantoms to simulate skin tissue properties and microvasculatures

This paper introduces novel methods to fabricate optical phantoms that simulate the morphologic, optical, and microvascular characteristics of skin tissue. The multi-layer skin-simulating phantom was fabricated by a light-cured 3D printer that mixed and printed the colorless light-curable ink with the absorption and the scattering ingredients for the designated optical properties. The simulated microvascular network was fabricated by a soft lithography process to embed microchannels in polydimethylsiloxane (PDMS) phantoms. The phantoms also simulated vascular anomalies and hypoxia commonly observed in cancer. A dual-modal multispectral and laser speckle imaging system was used for oxygen and perfusion imaging of the tissue-simulating phantoms. The light-cured 3D printing technique and the soft lithography process may enable freeform fabrication of skin-simulating phantoms that embed microvessels for image and drug delivery applications.

Three-dimensional fuse deposition modeling of tissue-simulating phantom for biomedical optical imaging

Abstract. Biomedical optical devices are widely used for clinical detection of various tissue anomalies. However, optical measurements have limited accuracy and traceability, partially owing to the lack of effective calibration methods that simulate the actual tissue conditions. To facilitate standardized calibration and performance evaluation of medical optical devices, we develop a three-dimensional fuse deposition modeling (FDM) technique for freeform fabrication of tissue-simulating phantoms. The FDM system uses transparent gel wax as the base material, titanium dioxide (TiO2) powder as the scattering ingredient, and graphite powder as the absorption ingredient. The ingredients are preheated, mixed, and deposited at the designated ratios layer-by-layer to simulate tissue structural and optical heterogeneities. By printing the sections of human brain model based on magnetic resonance images, we demonstrate the capability for simulating tissue structural heterogeneities. By measuring optical properties of multilayered phantoms and comparing with numerical simulation, we demonstrate the feasibility for simulating tissue optical properties. By creating a rat head phantom with embedded vasculature, we demonstrate the potential for mimicking physiologic processes of a living system.