On Transit Gait Programming of Six-legged Wall-climbing Robot

Transit gait programming is a key problem for a multi-legged robot to climb automatically from the ground up the wall, as well as between wall intersections. In this paper, a new idea is put forward by which the complex transit gait is decomposed into a sequence of two relatively simpler parts - single-leg motion and body pitching motion. An algorithm based on the above concept shows its feasibility and effectiveness in the graphic kinematics simulation.

Power Consumption Characteristics Research on Mobile System of Electrically Driven Large-Load-Ratio Six-Legged Robot

The electrically driven large-load-ratio six-legged robot with engineering capability can be widely used in outdoor and planetary exploration.However,due to the particularity of its parallel structure,the effective utilization rate of energy is not high,which has become an important obstacle to its practical application.To research the power consumption characteristics of robot mobile system is beneficial to speed up it toward practicability.Based on the configuration and walking modes of robot,the mathematical model of the power consumption of mobile system is set up.In view of the tripod gait is often selected for the six-legged robots,the simplified power consumption model of mobile system under the tripod gait is established by means of reducing the dimension of the robot’s statically indeterminate problem and constructing the equal force distribution.Then,the power consumption of robot mobile system is solved under different working conditions.The variable tendencies of the power consumption of robot mobile system are respectively obtained with changes in the rotational angles of hip joint and knee joint,body height,and span.The articulated rotational zones and the ranges of body height and span are determined under the lowest power consumption.According to the walking experiments of prototype,the variable tendencies of the average power consumption of robot mobile system are respectively acquired with changes in duty ratio,body height,and span.Then,the feasibility and correctness of theory analysis are verified in the power consumption of robot mobile system.The proposed analysis method in this paper can provide a reference on the lower power research of the large-load-ratio multi-legged robots.

Method for Analyzing Articulated Torques of Heavy-duty Six-legged Robot

The accuracy of an articulated torque analysis influences the comprehensive performances of heavy-duty multi-legged robots. Currently, the extremal estimation method and some complex methods are employed to calculate the articulated torques, which results in a large safety margin or a large number of calculations. To quickly obtain accurate articulated torques, an analysis method for the articulated torque is presented for an electrically driven heavy-duty six-legged robot. First, the rearmost leg that experiences the maximum normal contact force is confirmed when the robot transits a slope. Based on the ant-type and crab-type tripod gaits, the formulas of classical mechanics and MATLAB software are employed to theoretically analyze the relevant static torques of the joints. With the changes in the joint angles for the abductor joint, hip joint, and knee joint, variable tendency charts and extreme curves are obtained for the static articulated torques. Meanwhile, the maximum static articulated torques and the corresponding poses of the robot are also obtained. According to the poses of the robot under the maximum static articulated torques, ADAMS software is used to carry out a static simulation analysis. Based on the relevant simulation curves of the articulated torques, the maximum static articulated torques are acquired. A comparative analysis of the maximum static articulated torques shows that the theoretical calculation values are higher than the static simulation values, and the maximum error value is approximately 10%. The proposed method lays a foundation for quickly determining accurate articulated torques to develop heavy-duty six-legged robots.

Adsorption Performance of Sliding Wall-Climbing Robot

Sliding wall-climbing robot （SWCR） is applied worldwide for its continuous motion, however, considerable air leakage causes two problems： great power consumption and big noise, and they constraint the robot＇s comprehensive performance. So far, effective theoretical model is still lacked to solve the problems. The concept of SWCR＇s adsorption performance is presented, and the techniques of improving utilization rate of given adsorption force and utilization rate of power are studied respectively to improve SWCR＇s adsorption performance. The effect of locomotion mechanism selection and seal＇s pressure allocation upon utilization rate of given adsorption force is discussed, and the theoretical way for relevant parameters optimization are provided. The directions for improving utilization rate of power are pointed out based on the detail analysis results of suction system＇s thermodynamics and hydrodynamics. On this condition, a design method for SWCR-specific impeller is presented, which shows how the impeller＇s key parameters impact its aerodynamic performance with the aid of computational fluid dynamics （CFD） simulations. The robot prototype, BIT Climber, is developed, and its functions such as mobility, adaptability on wall surface, payload, obstacle ability and wall surface inspection are tested. Through the experiments for the adhesion performance of the robot adsorption system on the normal wall surface, at the impeller＇s rated rotating speed, the total adsorption force can reach 237.2 N, the average effective negative pressure is 3.02 kPa and the design error is 3.8% only, which indicates a high efficiency. Furthermore, it is found that the robot suction system＇s static pressure efficiency reaches 84% and utilization rate of adsorption force 81% by the experiment. This thermodynamics model and SWCR-specific impeller design method can effectively improve SWCR＇s adsorption performance and expand this robot applicability on the various walls. A sliding wall-climbing robot with high adhesion efficiency is developed, and this robot has the features of light body in weight, small size in structure and good capability in payload.

Development and control of flexible pneumatic wall-climbing robot

A new kind of flexible pneumatic wall-climbing robot,named WALKMAN-I,was proposed. WALKMAN-I is basically composed of a flexible pneumatic actuator (FPA),a flexible pneumatic spherical joint and six suction cups. It has many characteristics of low-cost,lightweight,simple structure and good flexibility. Its operating principle was introduced. Then three basic locomotion modes,which are linear motion,curvilinear motion and crossing the orthogonal planes,were presented. The safety conditions of WALKMAN-I were discussed and built. Finally,the control system was designed and experiments were carried out. Experimental results show that WALKMAN-I is able to climb on the vertical wall surface along a straight line or a curved path,and has the ability of crossing orthogonal planes and obstacles. The maximum rotation angle reaches 90°,the maximum velocity reaches 5 mm/s,and the rotation angle and the moving velocity of WALKMAN-I can be easily controlled.

Novel Door-opening Method for Six-legged Robots Based on Only Force Sensing

Current door-opening methods are mainly developed on tracked, wheeled and biped robots by applying multi-DOF manipulators and vision systems. However, door-opening methods for six-legged robots are seldom studied, especially using 0-DOF tools to operate and only force sensing to detect. A novel door-opening method for six-legged robots is developed and imple- mented to the six-parallel-legged robot. The kinematic model of the six-parallel-legged robot is established and the model of measuring the positional relationship between the robot and the door is proposed. The measurement model is completely based on only force sensing. The real- time trajectory planning method and the control strategy are designed. The trajectory planning method allows the maximum angle between the sagittal axis of the robot body and the normal line of the door plane to be 45°. A 0-DOF tool mounted to the robot body is applied to operate. By integrating with the body, the tool has 6 DOFs and enough workspace to operate. The loose grasp achieved by the tool helps release the inner force in the tool. Experiments are carried out to validate the method. The results show that the method is effective and robust in opening doors wider than 1 m. This paper proposes a novel door-opening method for six-legged robots, which notably uses a O-DOF tool and only force sensing to detect and open the door.

Static Force Analysis of Foot of Electrically Driven Heavy-Duty Six-Legged Robot under Tripod Gait

The electrically driven six-legged robot with high carrying capacity is an indispensable equipment for planetary exploration, but it hinders its practicability because of its low efficiency of carrying energy. Meanwhile, its load capacity also affects its application range. To reduce the power consumption, increase the load to mass ratio, and improve the stability of robot, the relationship between the walking modes and the forces of feet under the tripod gait are researched for an electrically driven heavy-duty six-legged robot. Based on the configuration characteristics of electrically driven heavy-duty six-legged, the typical walking modes of robot are analyzed. The mathematical models of the normal forces of feet are respectively established under the tripod gait of typical walking modes. According to the MATLAB software, the variable tendency charts are respectively gained for the normal forces of feet. The walking experiments under the typical tripod gaits are implemented for the prototype of electrically driven heavy-duty six-legged robot. The variable tendencies of maximum normal forces of feet are acquired. The comparison results show that the theoretical and experimental data are in the same trend. The walking modes which are most available to realize the average force of distribution of each foot are confirmed. The proposed method of analyzing the relationship between the walking modes and the forces of feet can quickly determine the optimal walking mode and gait parameters under the average distribution of foot force, which is propitious to develop the excellent heavy-duty multi-legged robots with the lower power consumption, larger load to mass ratio, and higher stability.

Research on Alternatively Moving Vacuum Absorbing Wall-climbing Robot

In conection with the complex working-surroundings of the wall-climbing Robot, this paper researched akind of alternatively moving mechanism with good obstacle-surmounting ability and high moving speed, making use ofthe thought of bionics. This paper designed a kind of self-adjusting multi-vacuum sucker. Furthermore, it employedthe theory of vacuum system to establish the work mathematics madel of control switch to are sucking disc and presented the design parameter of the control switch. In addition, this paper made use of the thought of bionics to design aobstacle-surmounting mechanism used in wall-climbing robot. Also it employed the theory Of robotics to analyze the kinematics and the dynamics movement of die robot.

Fault detection and identification based on combining logic and model in a wall-climbing robot

A combined logic- and model-based approach to fault detection and identification （FDI） in a suction foot control system of a wall-climbing robot is presented in this paper. For the control system, some fault models are derived by kinematics analysis. Moreover, the logic relations of the system states are known in advance. First, a fault tree is used to analyze the system by evaluating the basic events （elementary causes）, which can lead to a root event （a particular fault）. Then, a multiple-model adaptive estimation algorithm is used to detect and identify the model-known faults. Finally, based on the system states of the robot and the results of the estimation, the model-unknown faults are also identified using logical reasoning. Experiments show that the proposed approach based on the combination of logical reasoning and model estimating is efficient in the FDI of the robot.

High-performance wall-climbingrobot for inspection and maintenance

A wall-climbing robot that can continuously work on many types of wall surfaces has been developed. This robot based on low-vacuum adsorption principle consists of a locomotion mecha- nism, a sealing device, a fluid machine and a detecting system. The adsorption force is analyzed in details and its influencing factors are given. The robot prototype, which has the features of high ad- hesion efficiency, light body in weight, small size in structure and good capability in payload, is test- ed in outdoor and indoor environments. Through the experiments, the influences of the impeller slit and the seal clearance are discussed. In addition, the robot functions such as adsorption perform- ance, locomotion performance and wall adaptability are tested by experiments. The experiments have verified that the robot not only can climb on many types of wall surfaces, but also has outstand- ing locomotion ability and payload capacity.

Research on Gait Trajectory Planning of Wall-Climbing Robot Based on Improved PSO Algorithm

In order to reduce the labor intensity of high-altitude workers and realize the cleaning and maintenance of high-rise building exteriors,this paper proposes a design for a 4-DOF bipedal wall-climbing bionic robot inspired by the inchworm’s movement.The robot utilizes vacuum adsorption for vertical wall attachment and legged movement for locomotion.To enhance the robot’s movement efficiency and reduce wear on the adsorption device,a gait mimicking an inchworm’s movement is planned,and foot trajectory planning is performed using a quintic polynomial function.Under velocity constraints,foot trajectory optimization is achieved using an improved Particle Swarm Optimization(PSO)algorithm,determining the quintic polynomial function with the best fitness through simulation.Finally,through comparative experiments,the climbing time of the robot closely matches the simulation results,validating the trajectory planning method’s accuracy.

Highly adaptive triboelectric tactile sensor on the foot of autonomous wall-climbing robots for detecting the adhesion state and avoiding the hazard

Due to the excellent maneuverability and obstacle crossing of legged robots,it is possible for an autonomous legged wallclimbing robots to replace manual inspection of ship exterior panels.However,when the magnetic adsorption legged wallclimbing robot steps on the convex point or convex line of the wall,or even when the robot missteps,the robot is likely to detach from the ferromagnetic wall.Therefore,this paper proposes a tactile sensor for the legged magnetic adsorption wall-climbing robot to detect the magnetic adsorption state and improve the safety of the autonomous crawling of the robot.The tactile sensor mainly comprises a three-dimensional(3D)-printed shell,a tactile slider,and three isometric sensing units,with an optimized geometry.The experiment shows that the triboelectric tactile sensor can monitor the sliding depth of the tactile slider and control the light-emitting device(LED)signal light.In addition,in the demonstration experiment of detecting the adsorption state of the robot's foot,the triboelectric tactile sensor has strong adaptability to various ferromagnetic wall surfaces.Finally,this study establishes a robot gait control system to verify the feedback control ability of the triboelectric tactile sensor.The results show that the robot equipped with the triboelectric tactile sensor can recognize the dangerous area on the crawling wall and autonomously avoid the risk.Therefore,the proposed triboelectric tactile sensor has great potential in realizing the tactile sensing ability of robots and enhancing the safety and intelligent inspection of ultra-large vessels.

Design and Technical Development of Wall-Climbing Robots:A Review

Once working at heights is dangerous,it is a significant accident.These accidents brought substantial economic losses and caused a large number of casualties.Therefore,it is essential to use wall-climbing robots to replace manual work at heights.The design of the wall-climbing robot is inspired by the climbing action of insects or animals.An intelligent bionic robot device can carry special equipment to operate on the wall and perform some dangerous operations instead of firefighters or inspection personnel more efficiently.The scope of application is vast.This paper firstly summarizes the research progress of wall-climbing robots with three different moving methods:wheel-climbing,crawler-based,and leg-footed robots;summarizes the applications and breakthroughs of four adsorption technologies:negative pressure,magnetic force,bionic and electrostatic;discusses the application of motion control algorithms in wall-climbing robots.Secondly,the advantages and disadvantages of different migration modes and adsorption methods are pointed out.The distribution and advantages of the combined application of different migration modes and adsorption methods are analyzed.In addition,the future development trend of wall-climbing robots and the promoting effect of bionic technology development on wall-climbing robots are proposed.The content of this paper will provide helpful guidance for the research of wall-climbing robots.

A Four-legged Wall-climbing Robot with Spines and Miniature Setae Array Inspired by Longicorn and Gecko

In industrial applications,climbing robots are widely used for climbing and detection of rough or smooth pipe surfaces.Inspired by the special claws of longicorn is that can crawl on rough surfaces and the array of tiny bristles of geckos that can crawl on smooth surfaces,a new type of wall-climbing robot for rough or smooth surfaces is proposed in this paper.The bionic palms of the robot are suggested with special bionic hooks inspired by the longicorn and bionic adhesive materials inspired by the gecko with a good performance on adhering on the surfaces.The special bionic hooks are manufactured by the 3D printing method and the bionic adhesive materials are made by the polymer print lithography technology.These two different bionic adhere accessory are used on the robot’s palm to achieve climbing on the different surfaces.This foldable climbing robot can not only bend its own body to accommodate the cylindrical contact surfaces of different diameters,but also crawl on vertical rough and smooth surfaces using their bionic palms.

Design,Modeling and Experimentation of a Biomimetic Wall-climbing Robot for Multiple Surfaces

Wall-climbing robots can work on steep terrain and obtain environment information in three dimensions for human in real time,which can improve operation efficiency.However,traditional single-mode robots cannot ensure the stable attachment on complex wall surfaces.Inspired by the structure characteristics of flies and clingfishes,three bionic structures including the flexible spine wheel,the adhesive material and the adsorption system are proposed.Aiming at task requirements on multiple walls and based on the above three bionic structures,a wall-climbing robot with the composed mode of“grabbing+adhesion+adsorption”is presented v/a the law of mechanism configuration synthesis.Using static analysis,the safe attachment conditions for the robot on smooth and rough walls are that the adsorption force is 30 N or more.Based on Newton's Euler and Lagrange formulas,the dynamic equations of the robot on vertical walls are established to deduce that the maximum theoretical torque of the driving motor is 1.43 N·m at a uniform speed.Finally,the prototype of the wall-climbing robot is manufactured and tested on the vertical lime wall,coarse sandpaper wall and acrylic ceiling wall.Meanwhile,experiment results imply that the average maximum moving speed and the corresponding load are 7.19 cm·s-1 and 0.8 kg on the vertical lime wall,7.78 cm·s-1 and 0.6 kg on the coarse sandpaper wall,and 5.93 cm·s-1 and 0.2 kg on the acrylic ceiling wall respectively.These findings could provide practical reference for the robot’s application on walls.

Improving Kinematic Flexibility and Walking Performance of a Six-legged Robot by Rationally Designing Leg Morphology

This paper explores the design of leg morphology in a six-legged robot.Inspired by nature,where animals have different leg morphology,we examined how the difference in leg morphology influences behaviors of the robot.To this end,a systematic search was conducted by scanning over the parameter space consisting of default angles of leg joints of the six-legged robot,with two main objectives:to maximize the kinematic flexibility and walking performance of the robot.Results show that(1)to have a high kinematic flexibility with both the torso and swing legs,the femur segment should tilt downwards by 5°-10°and the tibia segment should be vertically downwards or with a slight inward tilt;(2)to achieve relatively energy-efficient and steady walking,the tibia segment should be approximately vertically downwards,with the femur segment tilting upwards to lower the torso height.The results of this study suggest that behaviors of legged robots can be passively enhanced by careful mechanical design choices,thereby leading to more competent legged machines.

Novel method of gait switching in six-legged robot walking on continuous-nondifferentiable terrain by utilizing stability and interference criteria

Continuous-nondifferentiable terrains are extremely challenging for the environment adaption of six-legged robots. Previous researches have focused on gait planning methods to improve inherent ability of legged robots to walk over moderate terrains.However,most six-legged robots utilize relatively monotonic gait so that they still cannot well adapt tough terrains. As a result,the current legged robots easily get stuck and fall when encountering continuous-nondifferentiable terrains,such as stairs.Therefore,a method of gait switching is proposed so that six-legged robots can flexibly generate multiple gaits to adapt complex terrains. This study investigated the relationship between six-legged robot gait topologies and physical constraints,such as robot stability and robot-terrain interference. The proposed gait switcher can generate 0-6,1-5,2-4 and 3-3 gaits,which is instructed by the stability and interference criteria. Simulations and experiments were performed on a novel six-legged robot Hexa-XIII that succeeded climbing stairs over 45°. The effectiveness of the gait switching method is validated by the experiment results.

A Three-row Opposed Gripping Mechanism with Bioinspired Spiny Toes for Wall-climbing Robots

This paper presents a study of a three-row opposed gripping mechanism made of bioinspired spiny toes.An insect Serica orientalis Motschulsky's tarsal system was first described and studied.A compliant single spiny toe model was established assuming that the contact asperities were spheres.Following the single toe contact model,a spiny toe array's contact model was then developed using asperity height's distribution fiinction.By studying the cngaging and disengaging process of the single toe,the mechanical behavior of the toe and toe array were addressed.The toes as well as the arrays were manufacturcd via rapid prototyping.A customized apparatus using dis-placement-control method has been carried out to measure the pull-in forces and pull-ofT positions of the single toe and toe array undcr various compression conditions.Based on the understanding,a three-row opposed gripping mechanism with radial configuration for wall-climbing robots was designed and fabricated according to the mechanical behaviors of the toe and array.Using an opposed spoke con figuration with 3 rows of 31 toes on each linkage array,the mechanism designed as a foot of climbing robots can vertically resist at least 1 kg of load on rough inverted surface,while the maximum normal load is as high as 31 N.The findings may provide a way in developing a high payload wall-climbing robot system for practical applications.

Step rolling planning of a six-legged robot with 1-DOF waist for slope climbing

Walking on inclined terrains or slopes is challenging for multi-legged robots. Robots should be able to handle more strict constraints imposed by the physical system than they do on flat terrains, such as smaller leg workspace and tighter stability margin. At the same time, robots need to autonomously generate constrained and stable motions to accommodate terrain inclination and unevenness. With regard to these issues, this paper provides a solution from two perspectives, mechanism design and planning methodology. The robot mechanism with a 1-DOF waist is firstly proposed to meet the requirements of the leg workspace and the static stability. After that, a step rolling planning scheme is introduced, in which the robot schedules its body planar 2D motion according to the human guidance and plans its elevation, roll, pitch as well as leg motions autonomously incorporating sensory feedbacks. The step rolling planning scheme ensures smooth and safe motion transitions from step to step.At last, simulations and experiments are carried out, demonstrating the effectiveness of our mechanical design and the proposed planning method.

Learning to Identify Footholds from Geometric Characteristics for a Six-legged Robot over Rugged Terrain

Foothold identification is a key ability for legged robots that allows generating terrain adaptive behaviors(e.g.,gait and control parameters)and thereby improving mobility in complex environment.To this end,this paper addresses the issue of foothold characterization and identification over rugged terrain,from the terrain geometry point of view.For a terrain region that might be a potential foothold of a robotic leg,the characteristic features are extracted as two first-order partial derivatives and two curvature parameters of a quadric regression surface at this location.These features are able to give an intuitive and,more importantly,accurate characterization towards the specific geometry of the ground location.On this basis,a supervised learning technique,Support Vector Machine(SVM),is employed,seeking to Ieam a foothold identification policy from human expert demonstration.As a result,an SVM classifier is leamt using the extracted features and human-demonstrated labels,which is able to identify whether or not a certain ground location is suited as a safe foot support for a robotic leg.It is shown that over 90%identification rate can be achieved with the proposed approach.Finally,preliminary experiment is implemented with a six-legged robot to demonstrate the effectiveness of the proposed approach.