A biomimetic underwater microrobot with multifunctional locomotion

Underwater microrobots are in urgent demand for applications such as pollution detection and video mapping in limited space. Compact structure, multi-functionality, and flexibility are normally considered incompatible characteristics for underwater microrobots. Nevertheless, to accomplish our objectives, we designed a novel inchworm-inspired biomimetic locomotion prototype with ionic polymer metal composite (IPMC) actuators, and conducted experiments to evaluate its crawling speed on a flat underwater surface. Based on this type of biomimetic locomotion, we introduced a new type of underwater microrobot, using ten IPMC actuators as legs or fingers to implement walking, rotating, floating, and grasping motions. We analysed the walking mechanism of the microrobot and calculated its theoretical walking speed. We then constructed a prototype of the microrobot, and carried out a series of experiments to evaluate its walking and floating speeds. Diving/surfacing experiments were also performed by electrolysing the water around the surfaces of the actuators. The microrobot used six of its actuators to grasp small objects while walking or floating. To implement closed-loop control, we employed three proximity sensors on the microrobot to detect an object or avoid an obstacle while walking.     

Development of ICPF Actuated Underwater Microrobots

It is our target to develop underwater microrobots for medical and industrial applications. This kind of underwater microrobots should have the characteristics of flexibility,good response and safety. Its structure should be simple and it can be driven by low voltage and produces no pollution or noise. The low actuating voltage and quick bending responses of Ionic Conducting Polymer Film (ICPF) are considered very useful and attractive for constructing various types of actuators and sensors. In this paper, we will first study the characteristics of the ICPF actuator used in underwater microrobot to realize swimming and walking. Then, we propose a new prototype model of underwater swimming microrobot utilizing only one piece of ICPF as the servo actuator. Through theoretic analysis, the motion mechanism of the microrobot is illustrated. It can swim forward and vertically. The relationships between moving speed and signal voltage amplitude and signal frequency is obtained after experimental study. Lastly, we present a novel underwater crab-like walking microrobot named crabliker-1.It has eight legs, and each leg is made up of two pieces of ICPF. Three sample processes of the octopod gait are proposed with a new analyzing method. The experimental results indicate that the crab-like underwater microrobot can perform transverse and rotation movement when the legs of the crab collaborate.     

A new type of hybrid fish-like microrobot

In order to develop a new type of fish-like microrobot with swimming, walking, and floating motions, in our past research, we developed a hybrid microrobot actuated by ionic conducting polymer film (ICPF) actuators. But the microrobot had some problems in walking and floating motions. In this paper, we propose a concept of hybrid microrobot (see Fig. 1). The microrobot is actuated by a pair of caudal fins, a base with legs and an array of artificial swim bladders. We have developed a prototype of the base with legs and one artificial swim bladder, respectively, and carried out experiments for evaluating their characteristics. Experimental results show the base with legs can realize walking speed of 6 mm/s and rotating speed of 7.1 degrees/s respectively, and the prototype of the artificial swim bladder has a maximum floatage of 2.6 mN. The experimental results also indicate that the microrobot has some advantages, such as walking motion with 2 degrees of freedom, the walking ability on rough surface (sand paper), the controllable floatage, etc. This kind of fish-like microrobot is expected for industrial and medical applications.     

Insect-type MEMS microrobot with mountable bare chip IC of artificial neural networks

This paper discussed insect-type MEMS microrobot system which could locomote without using computer programs. Locomotion of the MEMS microrobot was generated using the analog circuit of artificial neural networks. We constructed the artificial neural networks as a bare chip integrated circuit (IC) which could mount on top of the MEMS microrobot. As a result, the MEMS microrobot system could perform the locomotion using constructed bare chip IC of artificial neural networks. The insect-type MEMS microrobot system was 0.079 g in weight and less than 5.0 mm in size. Only the power source was outside of the robot. In addition, we analyze the heat conduction of the shape memory alloy-type actuator. It was shown that the heat of shape memory alloy conducts to the mechanical parts of the MEMS microrobot; therefore, locomotion becomes slowly after 30 s. The slow locomotion was 2 mm/min. We constructed the less conduction shape memory alloy-type actuator. The locomotion speed of the insect-type MEMS microrobot using less conduction shape memory alloy-type actuator was 90.8 mm/min.     

Toward Mission Capable Legged Robots through Biological Inspiration

Insects provide good models for the design and control of mission capable legged robots. We are using intelligent biological inspiration to extract the features important for locomotion from insect neuromechanical designs and implement them into legged robots. Each new model in our series of robots represents an advance in agility, strength, or energy efficiency, which are all important for performing missions. Robot IV is being constructed with a cockroach mechanical design. It features a lightweight exoskeleton structure and McKibben artificial muscles for passive joint stiffness. Our self-contained microrobot has rear legs that are inspired by cricket. Its diminutive size required us to custom fabricate almost all of its parts, including its McKibben actuators.     

Development of a pulse control-type MEMS microrobot with a hardware neural network

This article presents the micro-electro-mechanical systems (MEMS) microrobot which demonstrates locomotion controlled by hardware neural networks (HNN). The size of the microrobot fabricated by the MEMS technology is 4 × 4 × 3.5 mm. The frame of the robot is made of silicon wafer, and it is equipped with a rotary-type actuator, a link mechanism, and six legs. The rotary-type actuator generates rotational movement by applying an electrical current to artificial muscle wires. The locomotion of the microrobot is obtained by the rotation of the rotary-type actuator. As in a living organism, the HNN realized robot control without using any software programs, A/D converters, or additional driving circuits. A central pattern generator (CPG) model was implemented as an HNN system to emulate the locomotion pattern. The MEMS microrobot emulated the locomotion method and the neural networks of an insect with the rotary-type actuator, the link mechanism, and the HNN. The microrobot performed forward and backward locomotion, and also changed direction by inputting an external trigger pulse. The locomotion speed was 0.325 mm/s and the step width was 1.3 mm.     

A Novel Swimming Microrobot Based on Artificial Cilia for Biomedical Applications

Swimming microrobots can exhibit high levels of performance to move freely in the human body fluids to fulfill risky biomedical operations by mimicking microorganisms. Many researchers have proposed micro swimming methods for viscous flows based on flagellar motion. Here, a novel swimming microrobot inspired by ciliated microorganisms based on artificial cilia is introduced. The hydrodynamic model is developed and performance parameters such as propulsive force, propulsive velocity and efficiency of the microrobot are computed. The velocity and efficiency dependence on design parameters of microrobot is evaluated. The proposed micro swimming concept offers appropriate efficiency, thrust, speed and maneuverability. It is shown that the introduced swimming microrobot can reach a maximum speed 4.5 mm/s and efficiency of 40%. The proposed microrobot has the potential to be utilized in both viscous and turbulent body flows.     

Myriapod-like ambulation of a segmented microrobot

Segmented myriapod-like bodies may offer performance benefits over more common fixed body morphologies for ambulation. Here, the design of a segmented ambulatory microrobot with a flexible backbone is presented. A dynamic model describing the motion of the microrobot is used to determine body parameters. A three-segment microrobot was fabricated using the Smart Composite Microstructures process and piezoelectric bimorph actuators, and forward locomotion on a flat surface was demonstrated. The footprint of the 750 mg microrobot is 3.5 by 3.5 cm, and it has potential advantages over rigid body hexapedal microrobots in climbing, versatility, and stability.     

Four-leg independent mechanism for MEMS microrobot

In this paper, the development of a quadruped micro-electro mechanical system (MEMS) microrobot with a four-leg independent mechanism is described. As the actuator mechanism inside small robot bodies is difficult to realize, many microrobots use external field forces such as magnetism and vibration. In this paper, artificial muscle wires that are family of shape memory alloy are used for the force of the actuator. The artificial muscle wire shows the large displacement by passing the electrical current through the material itself. The double four-link mechanism is adopted for the leg system. The link mechanism transforms the linear motion of the artificial muscle wire to the foot step-like pedaling motion. The location of the backward swing motion is lower than that of forward swing motion. This motion generates the locomotion force. As a result, the total length of the constructed quadruped MEMS microrobot was 6 mm. The microrobot could perform similar gait pattern changes as the quadruped animal.     

SMA驱动的微型平面关节机器人的研究

近年来，利用形状记忆合金（ＳＭＡ）的形状记忆效应原理制作的驱动器已在机器人领域中得到应用，ＳＭＡ驱动器以其重量轻、结构紧凑、易控制等优点，大大推动了微型机器人的发展．本课题使用所研制的推挽式直线位移型和旋转关节型ＳＭＡ驱动器代替传统的伺服驱动系统，研制了一台三自由度（两个旋转自由度和一个直线自由度）且带末端夹持器的微型平面关节机器人．本文将介绍该机器人的结构设计，控制系统及其软件设计．     

IC design of driving circuit of MEMS microrobot using pulse-type hardware neuron model

This paper presented a driving circuit which can output a driving waveform of the piezoelectric element impact-type actuator. The piezoelectric element impact-type actuator generates the rotational movement which is necessary to move the legs of the micro electro mechanical systems (MEMS) microrobot. The MEMS microrobot is made from silicon wafers fabricated by micro fabrication technology. The size of the fabricated MEMS microrobot is 4.0 mm × 4.6 mm × 3.6 mm. The driving circuit consists of a bare chip IC of the pulse-type hardware neuron model (P-HNM) and a peripheral circuit. P-HNM is an electrical oscillating model which has the same basic features of biological neurons. Therefore, P-HNM can output the driving waveform of the piezoelectric element impact-type actuator using electrical oscillation as biological neuron. As a result, we showed that the driving circuit can output the driving waveform of the piezoelectric element impact-type actuator without using any software programs or analog digital converters.     

Design and Optimization of an Omnidirectional Permanent-Magnetic Wheeled Wall-Climbing Microrobot with MEMS-Based Electromagnetic Micromotors

The paper presents a compact omnidirectional permanent-magnetic wheeled wall-climbing microrobot. A millimeter-sized axial flux electromagnetic micromotor based on MEMS technology has been specially fabricated for the microrobot and its size is 6.8 mm × 7.8 mm × 3.9 mm. A novel permanent-magnetic wheel is designed, which is directly integrated with the stators and rotor of the electromagnetic micromotor. The omnidirectional wall-climbing mechanism is realized by a set of steering gears and three standard permanent-magnetic wheels. By static and dynamic force analysis of the microrobot, the required magnetic force and the required torques for its translational and steering movements are derived. To reduce the unnecessary torque consumption of the microrobot, its structural parameters are optimized in combination with its design constraints by ANSOFT and Pro/Engineer simulation. A prototype of the proposed microrobot with the maximum designed load capacity of 3 g is developed, whose size is 26 mm in diameter and 16.4 mm in height. Experimental and simulation results demonstrate the feasibility of these concepts.     

八足步行机器人参数的仿真计算

通过对八足步行机器人的研究,希望建立一个对复杂地形高度适应、有一定承载能力的步行机器人平台。该机器人在行走过程中,摆动腿为串联结构,而支撑腿则与地面、躯体形成具有冗余输入的多环并联机构,由于分析困难,因此借助先进的动力学仿真软件ADANS对其进行仿真计算。该文在八足步行机器人初始结构参数基础上,建立了三维机器人仿真模型,以灵活度为评价指标对机器人结构进行优化,并对优化后的模型作了运动学仿真分析,最后关于角度值的测量对原理样机的控制起到指导作用。研究表明ADAMS／VIEW模块可以方便、直观、准确地计算步行机器人运动情况。     

Development of a transformable wheel actuated by soft pneumatic actuators

Small mobile robots with transformable wheels have recently emerged thanks to their increased mobility and maneuverability. When a high payload is applied to these robots, however, wheel transformation becomes difficult because they must directly overcome the payload’s weight. In this paper, we propose a wheel that can be transformed from its starting circular shape (radius, 56 mm) to a wheel with three legs (radius, 99 mm) under a high payload with low operating force. The key design principle of this wheel is to kinematically decoupled legs and passive locking. Its legs are kinematically decoupled but operated by a single air pump using a pneumatic channel connected to soft pneumatic actuators installed at each leg. Application of pressure causes the legs to behave like a coupled system through the pneumatic channel. With pressurization, the two legs that are not in contact with the ground easily emerge from body, and the leg in contact with the ground emerges once the wheel rotates. Once emerged, each leg is supported by a rigid pawl instead of by the soft pneumatic actuators. This setup enables the legs to be transformed independently with low air pressure, even under high payloads. It reduces system weight and the energy required to maintain the transformed shape. This legged wheel can overcome obstacles up to 2.9 times the radius of the wheel in its circular form, and wheel transformation can be accomplished with 85 kPa air pressure for payloads up to 1115 g.     

Planar legged walking of a passive-spine hexapod robot

This paper proposes a new legged walking method for a novel passive-spine hexapod robot. This robot consists of several body segments connected by passive body joints. Each of the body segments carries two 1-DoF (degree of freedom) actuated legs. The robot is capable of achieving planar legged walking by rapidly abducting and adducting its legs. To model the mobility of a robot based on this simple design, the candidate configurations from all possible configurations are first selected in a mobility analysis of the robot based on the screw theory. All the feasible sequences of these candidate configurations are then searched to form planar locomotion gaits. Next, locomotive performance of the gaits is analyzed. Finally, the proposed locomotion design and gait planning methods are verified through simulations and experiments.     

Choosing Your Steps Carefully

Robot walking, while appealing for its resemblance to human motion, is not an obvious choice when both economy and versatility are desired. Wheeled vehicles are surprisingly capable on different terrains and are nearly unbeatable in terms of economy. In specialized situations, legged locomotion may become preferable. But legged locomotion entails inertial and other energetic costs that do not appear in wheeled machines. The force and work requirements of legged locomotion also only appear energetically economical when considering the unique features of the human body and human muscle. The attainment of high economy in a legged robot requires either actuators similar to humans' or discontinuous nonlinear mechanisms that can reduce energetic losses to support a load. The attainment of high versatility indicates that the ZMP is likely to remain applicable, unless serious advances are made in other control theoretical approaches.     

Design and Development of the Lifting and Propulsion Mechanism for a Biologically Inspired Water Runner Robot

This paper describes the design and development of a novel robot, which attempts to emulate the basilisk lizard's ability to run on the surface of water. Previous studies of the lizards themselves have characterized their means of staying afloat. The design of a biomimetic robot utilizing similar principles is discussed, modeled, and prototyped. Functionally, the robot uses a pair of identical four bar mechanisms, with a 180 ^deg phase shift to achieve locomotion on the water's surface. Simulations for determining robot lift and power requirements are presented. Through simulation and experimentation, parameters are varied with the focus being a maximization of the ratio of lift to power. Four legged robots were more easily stabilized, and had a higher lift-to-power ratio than two legged robots. Decreases in characteristic length and running speed, and increases in foot diameter and foot penetration depth all cause a higher lift to power ratio. Experimental lift approached 80 gr, and experimental performance exceeded 12 gr/W for four legged robots with circular feet. This work opens the door for legged robots to become ambulatory over both land and water, and represents a first step toward robots which run on the water instead of floating or swimming.     

A New Mechanism for Mesoscale Legged Locomotion in Compliant Tubular Environments

We present design and experimental performance results for a novel mechanism for robotic legged locomotion at the mesoscale (from hundreds of microns to tens of centimeters). The new mechanism is compact and strikes a balance between conflicting design objectives, exhibiting high foot forces and low power consumption. It enables a small robot to traverse a compliant, slippery, tubular environment, even while climbing against gravity. This mechanism is useful for many mesoscale locomotion tasks, including endoscopic capsule robot locomotion in the gastrointestinal tract. It has enabled fabrication of the first legged endoscopic capsule robot whose mechanical components match the dimensions of commercial pill cameras (11 mm diameter by 25 mm long). A novel slot-follower mechanism driven via lead screw enables the mechanical components of the capsule robot to be as small while simultaneously generating 0.63 N average propulsive force at each leg tip. In this paper, we describe kinematic and static analyses of the lead screw and slot-follower mechanisms, optimization of design parameters, and experimental design and tuning of a gait suitable for locomotion. A series of ex vivo experiments demonstrate capsule performance and ability to traverse the intestine in a manner suitable for inspection of the colon in a time period equivalent to standard colonoscopy.     

An adaptive locomotion controller for a hexapod robot: CPG,kinematics and force feedback

Insects can perform versatile locomotion behaviors such as multiple gaits, adapting to different terrains, fast escaping, etc. However, most of the existing bio-inspired legged robots do not possess such walking ability, especially when they walk on irregular terrains. To tackle this challenge, a central pattern generator （CPG）-based locomotion control methodology is proposed, integrated with a contact force feedback function. In this approach, multiple gaits are produced by the CFG module. After passing through a post-processing circuit and a delay-line, the control signal is fed into six trajectory generators to generate predefined feet trajectories for the six legs. Then, force feedback is employed to adjust these trajectories so as to adapt the robot to rough terrains. Finally the regulated trajectories are sent to inverse kinematics modules such that the position control instructions are generated to control the actuators. In both simulations and real robot experiments, we consistently show that the robot can perform sophisticated walking patterns. What is more, the robot can use the force feedback mechanism to deal with the irregularity in rough terrain. With this mechanism, the stability and adaptability of the robot are enhanced. In conclusion, the CPG-base control is an effective approach for legged robots and the force feedback approach is able to improve walking ability of the robots, especially when they walk on irregular terrains.     

轮足复合移动机器人运动规划发展现状及关键技术分析

地面移动机器人已经在资源勘探和灾难救援等多领域得到广泛应用,轮足复合机器人能够结合轮式运动速度快、平稳性高和足式运动的高越障性能等多方面优势,在理论创新和工程技术方面均有重要的研究价值.对近年来国内外轮足复合机器人的机械结构进行分析和比较,将轮足机构复合方式分为4类进行列举和总结.针对多模态运动的优势展开分析,列举轮足复合机器人主要采用的运动建模、规划和控制策略,不仅涉及单独的足式运动和轮式运动,同时涉及足端越障、变构型避障、轨迹规划的轮足复合运动.最后对运动规划关键技术进行总结和展望,指出轮足复合移动机器人后续的发展方向、研究思路和所面临的挑战.