Animals exhibit remarkable mobility and adaptability to their environments.Leveraging these advantages,various types of robots have been developed.To achieve path tracking control for the underwater hexapod robot,a pa...Animals exhibit remarkable mobility and adaptability to their environments.Leveraging these advantages,various types of robots have been developed.To achieve path tracking control for the underwater hexapod robot,a path tracking control system has been designed.Within this system,a Line-of-Sight(LOS)guidance system is utilized to generate the desired heading angle during the path tracking process.A heading tracking controller and a speed tracking controller are designed based on the super-twisting sliding mode method.Fuzzy logic is employed to establish the nonlinear relationship between the output of the upper-level controller,which includes force/torque,and the input parameters of the Central Pattern Generator(CPG)network.Finally,the effectiveness of the proposed method is verified through simulation and experimentation.The results demonstrate that the robot exhibits good tracking accuracy,as well as stability and coordination in motion.The designed path tracking system enables the underwater hexapod robot to rapidly and accurately track the desired path.展开更多
The current gait planning for legged robots is mostly based on human presets,which cannot match the flexible characteristics of natural mammals.This paper proposes a gait optimization framework for hexapod robots call...The current gait planning for legged robots is mostly based on human presets,which cannot match the flexible characteristics of natural mammals.This paper proposes a gait optimization framework for hexapod robots called Smart Gait.Smart Gait contains three modules:swing leg trajectory optimization,gait period&duty optimization,and gait sequence optimization.The full dynamics of a single leg,and the centroid dynamics of the overall robot are considered in the respective modules.The Smart Gait not only helps the robot to decrease the energy consumption when in locomotion,mostly,it enables the hexapod robot to determine its gait pattern transitions based on its current state,instead of repeating the formalistic clock-set step cycles.Our Smart Gait framework allows the hexapod robot to behave nimbly as a living animal when in 3D movements for the first time.The Smart Gait framework combines offline and online optimizations without any fussy data-driven training procedures,and it can run efficiently on board in real-time after deployment.Various experiments are carried out on the hexapod robot LittleStrong.The results show that the energy consumption is reduced by 15.9%when in locomotion.Adaptive gait patterns can be generated spontaneously both in regular and challenge environments,and when facing external interferences.展开更多
This paper presents a novel method for optimizing the contact force of a hexapod robot to enhance its dynamic motion stability when one of its legs fails.The proposed approach aims to improve the Force Angle Stability...This paper presents a novel method for optimizing the contact force of a hexapod robot to enhance its dynamic motion stability when one of its legs fails.The proposed approach aims to improve the Force Angle Stability Margin(FASM)and adapt the foot trajectory through contact force optimization to achieve safe and stable motion on various terrains.The foot force optimization approach is designed to optimize the FASM,a factor rarely considered in existing contact force optimization methods.By formulating the problem of enhancing the motion stability of the hexapod robot as a Quadratic Programming(QP)optimization problem,this approach can effectively address this issue.Simulations of a hexapod robot using a fault-tolerant gait,along with real field experiments,were conducted to validate the effectiveness and feasibility of the contact force optimization approach.The results demonstrate that this approach can be used to design a motion controller for a hexapod robot with a significantly improved motion stability.In summary,the proposed contact force optimization method offers a promising solution for enhancing the motion stability of hexapod robots with single leg failures and has the potential to significantly advance the development of fault-tolerant hexapod robots for various applications.展开更多
Most gait studies of multi-legged robots in past neglected the dexterity of robot body and the relationship between stride length and body height.This paper investigates the performance of a radial symmetrical hexapod...Most gait studies of multi-legged robots in past neglected the dexterity of robot body and the relationship between stride length and body height.This paper investigates the performance of a radial symmetrical hexapod robot based on the dexterity of parallel mechanism.Assuming the constraints between the supporting feet and the ground with hinges,the supporting legs and the hexapod body are taken as a parallel mechanism,and each swing leg is regarded as a serial manipulator.The hexapod robot can be considered as a series of hybrid serial-parallel mechanisms while walking on the ground.Locomotion performance can be got by analyzing these equivalent mechanisms.The kinematics of the whole robotic system is established,and the influence of foothold position on the workspace of robot body is analyzed.A new method to calculate the stride length of multi-legged robots is proposed by analyzing the relationship between the workspaces of two adjacent equivalent parallel mechanisms in one gait cycle.Referring to service region and service sphere,weight service sphere and weight service region are put forward to evaluate the dexterity of robot body.The dexterity of single point in workspace and the dexterity distribution in vertical and horizontal projection plane are demonstrated.Simulation shows when the foothold offset goes up to 174 mm,the dexterity of robot body achieves its maximum value 0.164 4 in mixed gait.The proposed methods based on parallel mechanisms can be used to calculate the stride length and the dexterity of multi-legged robot,and provide new approach to determine the stride length,body height,footholds in gait planning of multi-legged robot.展开更多
Robots are widely used to replace people in some burdensome or hamaful areas. Not only the moving ability but also the manipulating ability is needed in the missions of complex multitasking requirements. In the last d...Robots are widely used to replace people in some burdensome or hamaful areas. Not only the moving ability but also the manipulating ability is needed in the missions of complex multitasking requirements. In the last decades, wheel-legged hexapod robots are extensively studied to ineet this condition.展开更多
Realistically there are many robot joints in the biologically inspired hexapod robot, so they will generate many complexities in the calculations of the gait and the path planning and the control variables. The softwa...Realistically there are many robot joints in the biologically inspired hexapod robot, so they will generate many complexities in the calculations of the gait and the path planning and the control variables. The software Solidworks and MSC. ADAMS are adopted to simulate and analyze the prototype model of the robot. By the simulations used in our design, the applicability of the tripod gait is validated, and the scheme which uses cubic spline curve as the endpoint of foot＇s path is feasible. The principles, methods, and processes of the simulation of hexapod robot are illustrated. A methodology is proposed to get the robot inverse solution in ADAMS, and to simplify the theoretical calculation, and further more to improve the efficiency of the design.展开更多
Considering the compliance control problem of a hexapod robot under different environments, a control strategy based on the improved adaptive control algorithm is proposed. The model of robot structure and impedance c...Considering the compliance control problem of a hexapod robot under different environments, a control strategy based on the improved adaptive control algorithm is proposed. The model of robot structure and impedance control is established. Then, the indirect adaptive control algorithm is derived. Through the analysis of its parameters, it can be noticed that the algorithm does not meet the requirements of the robot compliance control in a complex environment. Therefore, the fuzzy control algorithm is used to adjust the adaptive control parameters. The satisfied system response can be obtained based on the adjustment in real time according to the error between input and output. Comparative experiments and analysis of traditional adaptive control and the improved adaptive control algorithm are presented. It can be verified that not only desired contact force can be reached quickly in different environments, but also smaller contact impact and sliding avoidance are guaranteed, which means that the control strategy has great significance to enhance the adaptability of the hexapod robot.展开更多
To provide hexapod robots with strategies of locomotion planning, observation experiments were operated on a kind of ant with the use of high speed digital photography and computer assistant analysis. Through digitali...To provide hexapod robots with strategies of locomotion planning, observation experiments were operated on a kind of ant with the use of high speed digital photography and computer assistant analysis. Through digitalization of original analog video, locomotion characters of ants were obtained, the biomimetic foundation was laid for polynomial trajectory planning of multi-legged robots, which was deduced with mathematics method. In addition, five rules were concluded, which apply to hexapod robots marching locomotion planning. The first one is the fundamental strategy of multi-legged robots＇ leg trajectory planning. The second one helps to enhance the static and dynamic stability of multi-legged robots. The third one can improve the validity and feasibility of legs＇ falling points. The last two give criterions of multi-legged robots＇ toe trajectory figures and practical recommendatory constraints. These five rules give a good method for marching locomotion planning of multi-legged robots, and can be expended to turning planning and any other special locomotion.展开更多
The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage...The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage mechanism and with force sensors in the tip of legs,distributed hardware structure and a modular software structure of the control system.Based on a set of local rules between adjacent legs,finite state machine(FSM) model is built to control the coordination of legs.An automatic smooth transition of gait pattern is achieved through deriving the mathematical relation between gait pattern and locomotion parameters.The disordered inter-leg phase sequence is adjusted to a regular state smoothly and quickly by the local rules based FSM,and the gait pattern can transform automatically adapting to irregular terrain.The experiment on HITCR-I has demonstrated that it can walk through irregular terrain reliably and expeditiously with the free gait controller designed in this paper.展开更多
A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating b...A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating between adjacent legs were put forward and the theory of finite state machine was employed to model them; further, a distributed network of local rules was constructed to adaptively adjust the fluctuation of inter-leg phase sequence. While in the leg-end trajectory planning level, combined polynomial curve was adopted to generate foot trajectory, which could realize real-time control of robot posture and accommodation to terrain conditions. In the simulation experiments, adaptive regulation of inter-leg phase sequence, omnidirectional locomotion and ground accommodation were realized, moreover, statically stable free gait was obtained simultaneously, which provided hexapod robot with the capability of walking on slightly irregular terrain reliably and expeditiously.展开更多
In the field of hexapod robot control,the application of central pattern generators(CPG)and deep reinforcement learning(DRL)is becoming increasingly common.Compared to traditional control methods that rely on dynamic ...In the field of hexapod robot control,the application of central pattern generators(CPG)and deep reinforcement learning(DRL)is becoming increasingly common.Compared to traditional control methods that rely on dynamic models,both the CPG and the end-to-end DRL approaches significantly simplify the complexity of designing control models.However,relying solely on DRL for control also has its drawbacks,such as slow convergence speed and low exploration efficiency.Moreover,although the CPG can produce rhythmic gaits,its control strategy is relatively singular,limiting the robot's ability to adapt to complex terrains.To overcome these limitations,this study proposes a three-layer DRL control architecture.The high-level reinforcement learning controller is responsible for learning the parameters of the middle-level CPG and the low-level mapping functions,while the middle and low level controllers coordinate the joint movements within and between legs.By integrating the learning capabilities of DRL with the gait generation characteristics of CPG,this method significantly enhances the stability and adaptability of hexapod robots in complex terrains.Experimental results show that,compared to pure DRL approaches,this method significantly improves learning efficiency and control performance,when dealing with complex terrains,it considerably enhances the robot's stability and adaptability compared to pure CPG control.展开更多
Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and adaptive locomotion based on different surface materials plays a...Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and adaptive locomotion based on different surface materials plays an important role in improving the stability of legged robots. A terrain classification and adaptive locomotion method for a hexapod robot named Qingzhui is proposed in this paper. First, a force-based terrain classification method is suggested. Ground contact force is calculated by collecting joint torques and inertial measurement unit information. Ground substrates are classified with the feature vector extracted from the collected data using the support vector machine algorithm. Then, an adaptive locomotion on different ground properties is proposed. The dynamic alternating tripod trotting gait is developed to control the robot, and the parameters of active compliance control change with the terrain. Finally, the method is integrated on a hexapod robot and tested by real experiments. Our method is shown effective for the hexapod robot to walk on concrete, wood, grass, and foam. The strategies and experimental results can be a valuable reference for other legged robots applied in outdoor environments.展开更多
With the widespread application of legged robot in various fields,the demand for a robot with high locomotion and manipulation ability is increasing.Adding an extra arm is a useful but general method for a legged robo...With the widespread application of legged robot in various fields,the demand for a robot with high locomotion and manipulation ability is increasing.Adding an extra arm is a useful but general method for a legged robot to obtain manipulation ability.Hence,this paper proposes a novel hexapod robot with two integrated leg–arm limbs that obtain dexterous manipulation functions besides locomotion ability without adding an extra arm.The manipulation modes can be divided into coordinated manipulation condition and single-limb manipulation condition.The former condition mainly includes fixed coordinated clamping case and fixed coordinated shearing case.For the fixed coordinated clamping case,the degrees of freedom(DOFs)analysis of equivalent parallel mechanism by using screw theory and the constraint equation of two integrated limbs are established.For the fixed coordinated shearing case,the coordinated working space is determined,and an ideal coordinated manipulation ball is presented to guide the coordinated shearing task.In addition,the constraint analysis of two adjacent integrated limbs is performed.Then,mobile manipulation with one integrated leg–arm limb while using pentapod gait is discussed as the single-limb manipulation condition,including gait switching analysis between hexapod gait and pentapod gait,different pentapod gaits analysis,and a complex six-DOF manipulation while walking.Corresponding experiments are implemented,including clamping tasks with two integrated limbs,coordinated shearing task by using two integrated limbs,and mobile manipulation with pentapod gait.This robot provides a new approach to building a multifunctional locomotion platform.展开更多
Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait gener...Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait generation after ssuming that obstacles have been detected and the walking path has been given. In this paper we propose and validate a novel obstacle avoidance framework for a six-legged walking robot Hexapod-III in unknown environment. Throughout the paper we highlight three themes: (1) The terrain map modeling and the obstacle detection; (2) the obstacle avoidance path planning method; (3) motion planning for the legged robot. Concretely, a novel geometric feature grid map (GFGM) is proposed to describe the terrain. Based on the GFGM, the obstacle detection algorithm is presented. Then the concepts of virtual obstacles and safe conversion pose are introduced. Virtual obstacles restrict the robot to walk on the detection terrain. A safe path based on Bezier curves, passing through safe conversion poses, is obtained by minimizing a penalty function taking into account the path length subjected to obstacle avoidance. Thirdly, motion planning for the legged robot to walk along the generated path is discussed in detail. At last, we apply the proposed framework to the Hexapod-III robot. The experimental result shows that our methodology allows the robot to walk safely without encountering with any obstacles in unknown environment.展开更多
In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mecha...In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mechanism of stick insect.The mathematical relation of walking velocity and gait pattern wasdepicted,a set of local rules operating between adjacent legs were put forward,and a distributed networkof local rules for gait control was constructed.With the interaction of adjacent legs,adaptive adjustmentof phase sequence fluctuation of walking legs resulting from change of terrain conditions or variety of walk-ing speed was implemented to generate statically stable gait.In the simulation experiments,adaptive ad-justment of inter-leg phase sequence and smooth transition of velocity and gait pattern were realized,andstatic stableness was ensured simultaneously,which provided the hexapod robot with the capability ofwalking on rough terrain stably and expeditiously.展开更多
This paper described the structure and control of a new kind of miniature hexap od bio-robot, analyzed the moving principle of the robot. The robot is based on the principle of bionics, its structure is simple, design...This paper described the structure and control of a new kind of miniature hexap od bio-robot, analyzed the moving principle of the robot. The robot is based on the principle of bionics, its structure is simple, design novel, unique. It can mov e forwards and backwards. The external dimensions of bio-robot is: length 30 mm , width 40 mm, height 20 mm, weight 6.3 g. Some tests about the model robot were made. The experimental results show that the robot has good mobility.展开更多
基金supported by the National Natural Science Foundation of China No.E1102/52071108National Defense Science and Industry Bureau Stability Support Project No.JCKYS2020SXJQR-04Natural Science Foundation of Heilongjiang Province No.JJ2021JQ0075.
文摘Animals exhibit remarkable mobility and adaptability to their environments.Leveraging these advantages,various types of robots have been developed.To achieve path tracking control for the underwater hexapod robot,a path tracking control system has been designed.Within this system,a Line-of-Sight(LOS)guidance system is utilized to generate the desired heading angle during the path tracking process.A heading tracking controller and a speed tracking controller are designed based on the super-twisting sliding mode method.Fuzzy logic is employed to establish the nonlinear relationship between the output of the upper-level controller,which includes force/torque,and the input parameters of the Central Pattern Generator(CPG)network.Finally,the effectiveness of the proposed method is verified through simulation and experimentation.The results demonstrate that the robot exhibits good tracking accuracy,as well as stability and coordination in motion.The designed path tracking system enables the underwater hexapod robot to rapidly and accurately track the desired path.
基金Supported by National Key Research and Development Program of China(Grant No.2021YFF0306202).
文摘The current gait planning for legged robots is mostly based on human presets,which cannot match the flexible characteristics of natural mammals.This paper proposes a gait optimization framework for hexapod robots called Smart Gait.Smart Gait contains three modules:swing leg trajectory optimization,gait period&duty optimization,and gait sequence optimization.The full dynamics of a single leg,and the centroid dynamics of the overall robot are considered in the respective modules.The Smart Gait not only helps the robot to decrease the energy consumption when in locomotion,mostly,it enables the hexapod robot to determine its gait pattern transitions based on its current state,instead of repeating the formalistic clock-set step cycles.Our Smart Gait framework allows the hexapod robot to behave nimbly as a living animal when in 3D movements for the first time.The Smart Gait framework combines offline and online optimizations without any fussy data-driven training procedures,and it can run efficiently on board in real-time after deployment.Various experiments are carried out on the hexapod robot LittleStrong.The results show that the energy consumption is reduced by 15.9%when in locomotion.Adaptive gait patterns can be generated spontaneously both in regular and challenge environments,and when facing external interferences.
基金The funding has been received from National Natural Science Foundation of China with Grant nos.52205013,52175012Fundamental Research Foundation for Universities of Heilongjiang Province with Grant no.2022-KYYWF-0122+1 种基金Natural Science Foundation of Heilongjiang Province with Grant no.LH2020E088Foundation of State Key Laboratory of Robotics and Systems with Grant no.SKLRS-2022-KF-18.
文摘This paper presents a novel method for optimizing the contact force of a hexapod robot to enhance its dynamic motion stability when one of its legs fails.The proposed approach aims to improve the Force Angle Stability Margin(FASM)and adapt the foot trajectory through contact force optimization to achieve safe and stable motion on various terrains.The foot force optimization approach is designed to optimize the FASM,a factor rarely considered in existing contact force optimization methods.By formulating the problem of enhancing the motion stability of the hexapod robot as a Quadratic Programming(QP)optimization problem,this approach can effectively address this issue.Simulations of a hexapod robot using a fault-tolerant gait,along with real field experiments,were conducted to validate the effectiveness and feasibility of the contact force optimization approach.The results demonstrate that this approach can be used to design a motion controller for a hexapod robot with a significantly improved motion stability.In summary,the proposed contact force optimization method offers a promising solution for enhancing the motion stability of hexapod robots with single leg failures and has the potential to significantly advance the development of fault-tolerant hexapod robots for various applications.
基金Supported by National Science Foundation for Distinguished Young Scholar,China(Grant No.51125020)National Natural Science Foundation of China(Grant No.51305009)CAST Foundation
文摘Most gait studies of multi-legged robots in past neglected the dexterity of robot body and the relationship between stride length and body height.This paper investigates the performance of a radial symmetrical hexapod robot based on the dexterity of parallel mechanism.Assuming the constraints between the supporting feet and the ground with hinges,the supporting legs and the hexapod body are taken as a parallel mechanism,and each swing leg is regarded as a serial manipulator.The hexapod robot can be considered as a series of hybrid serial-parallel mechanisms while walking on the ground.Locomotion performance can be got by analyzing these equivalent mechanisms.The kinematics of the whole robotic system is established,and the influence of foothold position on the workspace of robot body is analyzed.A new method to calculate the stride length of multi-legged robots is proposed by analyzing the relationship between the workspaces of two adjacent equivalent parallel mechanisms in one gait cycle.Referring to service region and service sphere,weight service sphere and weight service region are put forward to evaluate the dexterity of robot body.The dexterity of single point in workspace and the dexterity distribution in vertical and horizontal projection plane are demonstrated.Simulation shows when the foothold offset goes up to 174 mm,the dexterity of robot body achieves its maximum value 0.164 4 in mixed gait.The proposed methods based on parallel mechanisms can be used to calculate the stride length and the dexterity of multi-legged robot,and provide new approach to determine the stride length,body height,footholds in gait planning of multi-legged robot.
文摘Robots are widely used to replace people in some burdensome or hamaful areas. Not only the moving ability but also the manipulating ability is needed in the missions of complex multitasking requirements. In the last decades, wheel-legged hexapod robots are extensively studied to ineet this condition.
基金Sponsored by the Ministerial Level Advanced Research Foundation(6140528)
文摘Realistically there are many robot joints in the biologically inspired hexapod robot, so they will generate many complexities in the calculations of the gait and the path planning and the control variables. The software Solidworks and MSC. ADAMS are adopted to simulate and analyze the prototype model of the robot. By the simulations used in our design, the applicability of the tripod gait is validated, and the scheme which uses cubic spline curve as the endpoint of foot＇s path is feasible. The principles, methods, and processes of the simulation of hexapod robot are illustrated. A methodology is proposed to get the robot inverse solution in ADAMS, and to simplify the theoretical calculation, and further more to improve the efficiency of the design.
基金Project(51221004) supported by the Science Fund for Creative Research Groups of National Natural Science Foundation of ChinaProject(2010R50036) supported by the Program for Zhejiang Leading Team of S&T Innovation,China
文摘Considering the compliance control problem of a hexapod robot under different environments, a control strategy based on the improved adaptive control algorithm is proposed. The model of robot structure and impedance control is established. Then, the indirect adaptive control algorithm is derived. Through the analysis of its parameters, it can be noticed that the algorithm does not meet the requirements of the robot compliance control in a complex environment. Therefore, the fuzzy control algorithm is used to adjust the adaptive control parameters. The satisfied system response can be obtained based on the adjustment in real time according to the error between input and output. Comparative experiments and analysis of traditional adaptive control and the improved adaptive control algorithm are presented. It can be verified that not only desired contact force can be reached quickly in different environments, but also smaller contact impact and sliding avoidance are guaranteed, which means that the control strategy has great significance to enhance the adaptability of the hexapod robot.
基金Sponsored by the Ministerial Level Advanced Research Foundation(65822576)
文摘To provide hexapod robots with strategies of locomotion planning, observation experiments were operated on a kind of ant with the use of high speed digital photography and computer assistant analysis. Through digitalization of original analog video, locomotion characters of ants were obtained, the biomimetic foundation was laid for polynomial trajectory planning of multi-legged robots, which was deduced with mathematics method. In addition, five rules were concluded, which apply to hexapod robots marching locomotion planning. The first one is the fundamental strategy of multi-legged robots＇ leg trajectory planning. The second one helps to enhance the static and dynamic stability of multi-legged robots. The third one can improve the validity and feasibility of legs＇ falling points. The last two give criterions of multi-legged robots＇ toe trajectory figures and practical recommendatory constraints. These five rules give a good method for marching locomotion planning of multi-legged robots, and can be expended to turning planning and any other special locomotion.
基金Supported by the National High Technology Research and Development Programme of China(No.2007AA041550)the National NaturalScience Foundation of China(No.51105101)
文摘The purpose of this paper is to present and evaluate a method of free gait generation for HITCRI,a hexapod walking robot.The HITCR-I is designed as a modularized structure of legs that is based upon a four-bar linkage mechanism and with force sensors in the tip of legs,distributed hardware structure and a modular software structure of the control system.Based on a set of local rules between adjacent legs,finite state machine(FSM) model is built to control the coordination of legs.An automatic smooth transition of gait pattern is achieved through deriving the mathematical relation between gait pattern and locomotion parameters.The disordered inter-leg phase sequence is adjusted to a regular state smoothly and quickly by the local rules based FSM,and the gait pattern can transform automatically adapting to irregular terrain.The experiment on HITCR-I has demonstrated that it can walk through irregular terrain reliably and expeditiously with the free gait controller designed in this paper.
文摘A motion control structure used for autonomous walking on uneven terrain with a hexapod biomimetic robot is proposed based on function-behavior-integration. In the gait planning level, a set of local rules operating between adjacent legs were put forward and the theory of finite state machine was employed to model them; further, a distributed network of local rules was constructed to adaptively adjust the fluctuation of inter-leg phase sequence. While in the leg-end trajectory planning level, combined polynomial curve was adopted to generate foot trajectory, which could realize real-time control of robot posture and accommodation to terrain conditions. In the simulation experiments, adaptive regulation of inter-leg phase sequence, omnidirectional locomotion and ground accommodation were realized, moreover, statically stable free gait was obtained simultaneously, which provided hexapod robot with the capability of walking on slightly irregular terrain reliably and expeditiously.
基金supported by the Beijing Natural Science Foundation-Xiaomi Innovation Joint Fund(L243013)the National Natural Science Foundation of China(62172392).
文摘In the field of hexapod robot control,the application of central pattern generators(CPG)and deep reinforcement learning(DRL)is becoming increasingly common.Compared to traditional control methods that rely on dynamic models,both the CPG and the end-to-end DRL approaches significantly simplify the complexity of designing control models.However,relying solely on DRL for control also has its drawbacks,such as slow convergence speed and low exploration efficiency.Moreover,although the CPG can produce rhythmic gaits,its control strategy is relatively singular,limiting the robot's ability to adapt to complex terrains.To overcome these limitations,this study proposes a three-layer DRL control architecture.The high-level reinforcement learning controller is responsible for learning the parameters of the middle-level CPG and the low-level mapping functions,while the middle and low level controllers coordinate the joint movements within and between legs.By integrating the learning capabilities of DRL with the gait generation characteristics of CPG,this method significantly enhances the stability and adaptability of hexapod robots in complex terrains.Experimental results show that,compared to pure DRL approaches,this method significantly improves learning efficiency and control performance,when dealing with complex terrains,it considerably enhances the robot's stability and adaptability compared to pure CPG control.
基金This work was supported by the National Nature Science Foundation of China(Grant Nos.U1613208 and 51927809)the National Key R&D Program of China(Grant No.2017YFE0112200)the European Union's Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie grant(Grant No.734575).
文摘Legged robots have potential advantages in mobility compared with wheeled robots in outdoor environments. The knowledge of various ground properties and adaptive locomotion based on different surface materials plays an important role in improving the stability of legged robots. A terrain classification and adaptive locomotion method for a hexapod robot named Qingzhui is proposed in this paper. First, a force-based terrain classification method is suggested. Ground contact force is calculated by collecting joint torques and inertial measurement unit information. Ground substrates are classified with the feature vector extracted from the collected data using the support vector machine algorithm. Then, an adaptive locomotion on different ground properties is proposed. The dynamic alternating tripod trotting gait is developed to control the robot, and the parameters of active compliance control change with the terrain. Finally, the method is integrated on a hexapod robot and tested by real experiments. Our method is shown effective for the hexapod robot to walk on concrete, wood, grass, and foam. The strategies and experimental results can be a valuable reference for other legged robots applied in outdoor environments.
基金This paper was funded by the National Key R&D Program of China(Grant No.2019YFB1309600)the National Natural Science Foundation of China(Grant Nos.51775011 and 91748201).
文摘With the widespread application of legged robot in various fields,the demand for a robot with high locomotion and manipulation ability is increasing.Adding an extra arm is a useful but general method for a legged robot to obtain manipulation ability.Hence,this paper proposes a novel hexapod robot with two integrated leg–arm limbs that obtain dexterous manipulation functions besides locomotion ability without adding an extra arm.The manipulation modes can be divided into coordinated manipulation condition and single-limb manipulation condition.The former condition mainly includes fixed coordinated clamping case and fixed coordinated shearing case.For the fixed coordinated clamping case,the degrees of freedom(DOFs)analysis of equivalent parallel mechanism by using screw theory and the constraint equation of two integrated limbs are established.For the fixed coordinated shearing case,the coordinated working space is determined,and an ideal coordinated manipulation ball is presented to guide the coordinated shearing task.In addition,the constraint analysis of two adjacent integrated limbs is performed.Then,mobile manipulation with one integrated leg–arm limb while using pentapod gait is discussed as the single-limb manipulation condition,including gait switching analysis between hexapod gait and pentapod gait,different pentapod gaits analysis,and a complex six-DOF manipulation while walking.Corresponding experiments are implemented,including clamping tasks with two integrated limbs,coordinated shearing task by using two integrated limbs,and mobile manipulation with pentapod gait.This robot provides a new approach to building a multifunctional locomotion platform.
基金supported by the National Basic Research Program of China (Grant No. 2013CB035501)
文摘Obstacle avoidance is quite an important issue in the field of legged robotic applications, such as rescuing and detecting in complicated environment. Most related researchers focused on the legged robot’s gait generation after ssuming that obstacles have been detected and the walking path has been given. In this paper we propose and validate a novel obstacle avoidance framework for a six-legged walking robot Hexapod-III in unknown environment. Throughout the paper we highlight three themes: (1) The terrain map modeling and the obstacle detection; (2) the obstacle avoidance path planning method; (3) motion planning for the legged robot. Concretely, a novel geometric feature grid map (GFGM) is proposed to describe the terrain. Based on the GFGM, the obstacle detection algorithm is presented. Then the concepts of virtual obstacles and safe conversion pose are introduced. Virtual obstacles restrict the robot to walk on the detection terrain. A safe path based on Bezier curves, passing through safe conversion poses, is obtained by minimizing a penalty function taking into account the path length subjected to obstacle avoidance. Thirdly, motion planning for the legged robot to walk along the generated path is discussed in detail. At last, we apply the proposed framework to the Hexapod-III robot. The experimental result shows that our methodology allows the robot to walk safely without encountering with any obstacles in unknown environment.
基金Supported by the National High Technology Research and Development Programme of China (No. 2006AA04Z245)by the Progran for Changjiang Scholars and Innovative Research Team in University of China (PCSIRT) (IRT0423)
文摘In order to fulfill the goal of autonomous walking on rough terrain,a distributed gait planningmethod applied to hexapod biomimetic robot locomotion is proposed based on the research effort of gait co-ordination mechanism of stick insect.The mathematical relation of walking velocity and gait pattern wasdepicted,a set of local rules operating between adjacent legs were put forward,and a distributed networkof local rules for gait control was constructed.With the interaction of adjacent legs,adaptive adjustmentof phase sequence fluctuation of walking legs resulting from change of terrain conditions or variety of walk-ing speed was implemented to generate statically stable gait.In the simulation experiments,adaptive ad-justment of inter-leg phase sequence and smooth transition of velocity and gait pattern were realized,andstatic stableness was ensured simultaneously,which provided the hexapod robot with the capability ofwalking on rough terrain stably and expeditiously.
文摘This paper described the structure and control of a new kind of miniature hexap od bio-robot, analyzed the moving principle of the robot. The robot is based on the principle of bionics, its structure is simple, design novel, unique. It can mov e forwards and backwards. The external dimensions of bio-robot is: length 30 mm , width 40 mm, height 20 mm, weight 6.3 g. Some tests about the model robot were made. The experimental results show that the robot has good mobility.
