Dear Editor,This letter addresses the formation control problem for constrained underactuated autonomous underwater vehicles (AUVs). The feasibility condition of the virtual control law is eliminated by introducing a ...Dear Editor,This letter addresses the formation control problem for constrained underactuated autonomous underwater vehicles (AUVs). The feasibility condition of the virtual control law is eliminated by introducing a nonlinear state dependence function (NSDF) that transforms the state of each AUV in the formation.展开更多
The stiffness information of the grasped object at the initial contact stage can be effectively used to adjust the grasping force of the prosthetic hand,thereby preventing damage to the object.However,the object’s de...The stiffness information of the grasped object at the initial contact stage can be effectively used to adjust the grasping force of the prosthetic hand,thereby preventing damage to the object.However,the object’s deformation and contact force are often minimal during the initial stage and not easily obtained directly.Additionally,stiffness estimation methods for prosthetic hands often require contact sensors,which can easily lead to poor contact issues.To address the above issues,this paper proposes the model-based stiffness estimation of grasped objects for underactuated prosthetic hands without force sensors.First,the kinematic model is linearized at the contact points to achieve the estimation of the linkage angles in the underactuated prosthetic hand.Secondly,the motor parameters are estimated using the Kalman filter method,and the grasping force is obtained from the dynamic model of the underactuated prosthetic hand.Finally,the contact model of the prosthetic hand grasping an object is established,and an online stiffness estimation method based on the contact model for the grasped object is proposed using the iterative reweighted least squares method.Experimental results show that this method can estimate the stiffness of grasped objects within 250 ms without contact sensors.展开更多
To achieve the track following and collision avoidance of underactuated unmanned surface vehicle(USV),autonomous navigation model based on model predictive control is established by including the track offset,speed va...To achieve the track following and collision avoidance of underactuated unmanned surface vehicle(USV),autonomous navigation model based on model predictive control is established by including the track offset,speed variation and rule compliance as the evaluation functions and including the ship domain of dynamic/static navigation obstacles and the mechanical characteristics limitation as constraints.The effectiveness of the model for autonomous navigation of USV in the situation of multi-ship encounters and in the complex waters with both dynamic and static obstructions is verified by several groups of simulation work.The simulation results show that the proposed model can realize the autonomous navigation of the underactuated USV under the complex waters.展开更多
Inspired by the crucial role of the tail in crocodile locomotion,we propose a novel rigid-flexible coupled tail structure design.The tail design reduces the number of required actuators,enables undulatory propulsion i...Inspired by the crucial role of the tail in crocodile locomotion,we propose a novel rigid-flexible coupled tail structure design.The tail design reduces the number of required actuators,enables undulatory propulsion in swimming,and provides additional support during terrestrial crawling.However,when the tail lifts off the ground during land crawling,its flexible underactuated structure tends to oscillate randomly due to minimal damping.These oscillations impart disruptive reaction torques to the body,critically impairing locomotion stability.To tackle this issue,we employed the standard Denavit-Hartenberg(DH)method and Newton-Euler equations to formulate a rigid-flexible coupled dynamic model for the tail,in which distributed elastic forces are embedded as internal forces in the force balance equations.Based on this model,we propose an oscillation suppression strategy based on an energy-optimized Nonlinear Model Predictive Controller(NMPC)with a single joint torque as the control input.This controller solves a constrained multi-objective optimization problem to effectively suppress the underactuated oscillations of the tail.Finally,experimental comparisons validate the accuracy of the dynamic model,and simulations based on this model substantiate the effectiveness of the oscillation suppression strategy.展开更多
A high-order fully actuated(HOFA)control method is developed for underactuated mechanical systems(UMSs)with model uncertainties and external disturbances.First,a model transformation is made from the original to a pse...A high-order fully actuated(HOFA)control method is developed for underactuated mechanical systems(UMSs)with model uncertainties and external disturbances.First,a model transformation is made from the original to a pseudo strict-feedback form,and an HOFA model is established by using the method of variable elimination.Then,a group of high-order extended state observers(ESOs)are designed to deal with model uncertainties and external disturbances.The HOFA model is further classified and decomposed to achieve output constraints within a finite time range,and a barrier function is designed by combining with a shift function.Additionally,an ESO-based HOFA tracking control strategy for UMS is proposed.Finally,a manipulator model is used to verify the effectiveness of the proposed control strategy.展开更多
An underactuated finger structure actuated by tendon-driven system is presented.Kinematics and static analysis of the finger is done,and the results indicate that the prosthetic finger structure is effective and feasi...An underactuated finger structure actuated by tendon-driven system is presented.Kinematics and static analysis of the finger is done,and the results indicate that the prosthetic finger structure is effective and feasible.Based on the design of finger,a prosthetic hand is designed.The hand is composed of 5 independent fingers and it looks more like humanoid.Its size is about 85% of an adult's hand and weights about 350 g.Except the thumb finger,each finger is actuated by one DC motor,gear head and a tendon,and has three curling/extension joints.The thumb finger which is different from other existing prostheses is a novel design scheme.The thumb finger has four joints including three curling/extension joints and a joint which is used to realize the motion of the thumb related to the palm,and these joints are also driven by one DC motor,harmonic drive and a tendon.The underactuation and adaptive curling/extension motion of the finger are realized by joint torsion springs.A high-powered chip of digital signal processing(DSP)is the main part of the electrical system which is used for the motors control,data collection,communication with external controlling source,and so on.To improve the reliability of the hand,structures and sensors are designed and made as simply as possible.The hand has strong manipulation capabilities that have been verified by finger motion and grasping tests and it can satisfy the daily operational needs and psychological needs of deformities.展开更多
In this study, we improved an underactuated finger mechanism by using Solidworks to simulate the grasp operation of a finger in some different situations. In addition, a robot palm is designed for the three-finger rob...In this study, we improved an underactuated finger mechanism by using Solidworks to simulate the grasp operation of a finger in some different situations. In addition, a robot palm is designed for the three-finger robot hand with the designed underactuated fingers. A Solidworks simulation was used to verify the rationality of the design. Some parts of the hand were modified to fit for 3D printing, and a prototype of the hand was produced by 3D printing, which could reduce the cost of the production process, as well as provide design flexibility and other advantages. Finally, some grasping experiments were made with the prototype. The results showed that the robot could grasp objects with different sizes, and further verified the rationality of the design and feasibility of fabricating the robot hand using 3D printing.展开更多
The dynamics of classical robotic systems are usually described by ordinary differential equations via selecting a minimum set of independent generalized coordinates. However, different parameterizations and the use o...The dynamics of classical robotic systems are usually described by ordinary differential equations via selecting a minimum set of independent generalized coordinates. However, different parameterizations and the use of a nonminimum set of （dependent） generalized coordinates can be advantageous in such cases when the modeled device contains closed kinematic loops and/or it has a complex structure. On one hand, the use of dependent coordinates, like natural coordinates, leads to a different mathematical representation where the equations of motion are given in the form of differential algebraic equations. On the other hand, the control design of underactuated robots usually relies on partial feedback linearization based techniques which are exclusively developed for systems modeled by independent coordinates. In this paper we propose a different control algorithm formulated by using dependent coordinates. The applied computed torque controller is realized via introducing actuator constraints that complement the kinematic constraints which are used to describe the dynamics of the investigated service robotic system in relatively simple and compact form. The proposed controller is applied to the computed torque control of the planar model of the ACROBOTER service robot. The stability analysis of the digitally controlled underactuated service robot is provided as a real parameter case study for selecting the optimal control gains.展开更多
The underactuated fingers used in numerous robotic systems are evaluated by grasping force, configuration space, actuation method, precision of operation, compactness and weight. In consideration of all such factors a...The underactuated fingers used in numerous robotic systems are evaluated by grasping force, configuration space, actuation method, precision of operation, compactness and weight. In consideration of all such factors a novel linkage based underactuated finger with a self-adaptive actuation mechanism is proposed to be used in prosthetics hands, where the finger can accomplish flexion and extension. Notably, the proposed mechanism can be characterized as a combination of parallel and series links. The mobility of the system has been analyzed according to the Chebychev-Grübler-Kutzbach criterion for a planar mechanism. With the intention of verifying the effectiveness of the mechanism, kinematics analysis has been carried out, by means of the geometric representation and Denavit-Hartenberg (D-H) parameter approach. The presented two-step analysis followed by a numerical study, eliminates the limitations of the D-H conversion method to analyze the robotics systems with both series and parallel links. In addition, the trajectories and configuration space of the proposed finger mechanism have been determined by the motion simulations. A prototype of the proposed finger mechanism has been fabricated using 3D printing and it has been experimentally tested to validate its functionality. The kinematic analysis, motion simulations, experimental investigations and finite element analysis have demonstrated the effectiveness of the proposed mechanism to gain the expected motions.展开更多
In this article, a nonlinear model of an underactuated six degrees of freedom （6 DOF） quadrotor helicopter is derived on the basis of the Newton-Euler formalism. The derivation comprises determining equations of the...In this article, a nonlinear model of an underactuated six degrees of freedom （6 DOF） quadrotor helicopter is derived on the basis of the Newton-Euler formalism. The derivation comprises determining equations of the motion of the quadrotor in three dimensions and approximating the actuation forces through the modeling of aerodynamic coefficients and electric motor dynamics. The derived model composed of translational and rotational subsystems is dynamically unstable, so a sequential nonlinear control strategy is used. The control strategy includes feedback linearization coupled with a PD controller for the translational subsystem and a backstepping-based PID nonlinear controller for the rotational subsystem of the quadrotor. The performances of the nonlinear control method are evaluated by nonlinear simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter in quasi-stationary flights.展开更多
When developing a humanoid myo-control hand,not only the mechanical structure should be considered to afford a high dexterity,but also the myoelectric (electromyography,EMG) control capability should be taken into acc...When developing a humanoid myo-control hand,not only the mechanical structure should be considered to afford a high dexterity,but also the myoelectric (electromyography,EMG) control capability should be taken into account to fully accomplish the actuation tasks.This paper presents a novel humanoid robotic myocontrol hand (AR hand Ⅲ) which adopted an underac- tuated mechanism and a forearm myocontrol EMG method.The AR hand Ⅲ has five fingers and 15 joints,and actuated by three embedded motors.Underactuation can be found within each finger and between the rest three fingers (the middle finger,the ring finger and the little finger) when the hand is grasping objects.For the EMG control,two specific methods are proposed:the three-fingered hand gesture configuration of the AR hand Ⅲ and a pattern classification method of EMG signals based on a statistical learning algorithm-Support Vector Machine (SVM).Eighteen active hand gestures of a testee are recognized ef- fectively,which can be directly mapped into the motions of AR hand Ⅲ.An on-line EMG control scheme is established based on two different decision functions:one is for the discrimination between the idle and active modes,the other is for the recog- nition of the active modes.As a result,the AR hand Ⅲ can swiftly follow the gesture instructions of the testee with a time delay less than 100 ms.展开更多
Based on rational behavior model of three layers, a tracking control system is designed for straight line tracking which is commonly used in underwater survey missions. An intelligent PID control law implemented as pl...Based on rational behavior model of three layers, a tracking control system is designed for straight line tracking which is commonly used in underwater survey missions. An intelligent PID control law implemented as planning level during the control system using transverse deviation is came up with. Continuous tracking of path expressed by a point sequence can be realized by the law. Firstly, a path tracking control system based on rational behavior model of three layers is designed, mainly satisfying the needs of underactuated AUV. Since there is no need to perform spatially coupled maneuvers, the 3D path tracking control is decoupled into planar 2D path tracking and depth or height tracking separately. Secondly, planar path tracking controller is introduced. For the reason that more attention is paid to comparing with vertical position control, transverse deviation in analytical form is derived. According to the Lyapunov direct theory, control law is designed using discrete PID algorithm whose parameters obey adaptive fuzzy adjustment. Reference heading angle is given as an output of the guidance controller conducted by lateral deviation together with its derivative. For the purpose of improving control quality and facilitating parameter modifying, data normalize modules based on Sigmoid function are applied to input-output data manipulation. Lastly, a sequence of experiments was carried out successfully, including tests in Longfeng lake and at the Yellow sea. In most challenging sea conditions, tracking errors of straight line are below 2 m in general. The results show that AUV is able to compensate the disturbance brought by sea current. The provided test results demonstrate that the designed guidance controller guarantees stably and accurately straight route tracking. Besides, the proposed control system is accessible for continuous comb-shaped path tracking in region searching.展开更多
The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturban...The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.展开更多
The trajectory planning and tracking control for an underactuated unmanned surface vessel(USV) were addressed.The reference trajectory was generated by a virtual USV,and the error equation of trajectory tracking for u...The trajectory planning and tracking control for an underactuated unmanned surface vessel(USV) were addressed.The reference trajectory was generated by a virtual USV,and the error equation of trajectory tracking for underactuated USV was obtained,which transformed the tracking and stabilization problem of underactuated USV into the stabilization problem of the trajectory tracking error equation.A nonlinear state feedback controller was proposed based on backstepping technique and Lyapunov's direct method.By means of Lyapunov analysis,it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property.Numerical simulation results are presented to validate the effectiveness and robustness of the proposed controller.展开更多
The trajectory-tracking control problem is inves-tigated for an autonomous underwater vehicle(AUV)moving in the vertical plane using an internal point mass and a rear thruster as actuators.Combined with the dynamics o...The trajectory-tracking control problem is inves-tigated for an autonomous underwater vehicle(AUV)moving in the vertical plane using an internal point mass and a rear thruster as actuators.Combined with the dynamics of the point mass,the AUV is modeled as an underactuated system.A Lyapunov-based tracking controller is proposed by using backstepping approach to stabilize the error dynamics and force the position errors to a small neighborhood of the origin.Simulation results validate the proposed tracking approach.展开更多
Aiming at a space manipulator with free-swinging joint failure, a failure treatment strategy and fault-tolerant path planning method is proposed in this paper. This method can realize failure treatment of a space mani...Aiming at a space manipulator with free-swinging joint failure, a failure treatment strategy and fault-tolerant path planning method is proposed in this paper. This method can realize failure treatment of a space manipulator with free-swinging joint failure through determination of the optimal locked joint angle and dynamics model reconfiguration. Fault-tolerant path planning is realized by the establishment of the degraded workspace with integrated kinematics performance(DWWIKP) and an improved A-Star(A*) algorithm. This paper has the following contributions.The determination of the optimal locked joint angle can ensure that the manipulator is able to continue follow-up tasks while maximizing the workspace of the manipulator after locking the fault joint. Underactuated control of a high degree-of-freedom(DOF) manipulator can be effectively solved through dynamics model reconfiguration. The analysis process of the dynamics coupling relationship can be applied to cases where the active joint and the passive joint are parallel or perpendicular to each other. The establishment of the DWWIKP can demonstrate the kinematics performance of the manipulator in both joint space and operation space comprehensively. The improved A*algorithm based on the integrated kinematics performance index(IKPI) can search a fault-tolerant task trajectory that satisfies the requirements of reachability and the overall kinematics performance simultaneously. The method proposed in this paper is verified by a 7-DOF manipulator, and it is available to any DOF manipulator with free-swinging joint failure.展开更多
Robot hands have been developing during the last few decades. There are many mechanical structures and analyti?cal methods for di erent hands. But many tough problems still limit robot hands to apply in homelike envir...Robot hands have been developing during the last few decades. There are many mechanical structures and analyti?cal methods for di erent hands. But many tough problems still limit robot hands to apply in homelike environment. The ability of grasping objects covering a large range of sizes and various shapes is fundamental for a home service robot to serve people better. In this paper, a new grasping mode based on a novel sucked?type underactuated(STU) hand is proposed. By combining the flexibility of soft material and the e ect of suction cups, the STU hand can grasp objects with a wide range of sizes, shapes and materials. Moreover, the new grasping mode is suitable for some situations where the force closure is failure. In this paper, we deduce the e ective range of sizes of objects which our hand using the new grasping mode can grasp. Thanks to the new grasping mode, the ratio of grasping size between the biggest object and the smallest is beyond 40, which makes it possible for our robot hand to grasp diverse objects in our daily life. For example, the STU hand can grasp a soccer(220 mm diameter, 420 g) and a fountain pen(9 mm diameter, 9 g). What’s more, we use the rigid body equilibrium conditions to analysis the force condition. Experiment evaluates the high load capacity, stability of the new grasping mode and displays the versatility of the STU hand. The STU hand has a wide range of applications especially in unstructured environment.展开更多
基金supported by the National Natural Science Foundation of China(62073094)the Fundamental Research Funds for the Central Universities(3072024GH0404)
文摘Dear Editor,This letter addresses the formation control problem for constrained underactuated autonomous underwater vehicles (AUVs). The feasibility condition of the virtual control law is eliminated by introducing a nonlinear state dependence function (NSDF) that transforms the state of each AUV in the formation.
基金supported by the National Natural Science Foundation of China under Grant 52275297.
文摘The stiffness information of the grasped object at the initial contact stage can be effectively used to adjust the grasping force of the prosthetic hand,thereby preventing damage to the object.However,the object’s deformation and contact force are often minimal during the initial stage and not easily obtained directly.Additionally,stiffness estimation methods for prosthetic hands often require contact sensors,which can easily lead to poor contact issues.To address the above issues,this paper proposes the model-based stiffness estimation of grasped objects for underactuated prosthetic hands without force sensors.First,the kinematic model is linearized at the contact points to achieve the estimation of the linkage angles in the underactuated prosthetic hand.Secondly,the motor parameters are estimated using the Kalman filter method,and the grasping force is obtained from the dynamic model of the underactuated prosthetic hand.Finally,the contact model of the prosthetic hand grasping an object is established,and an online stiffness estimation method based on the contact model for the grasped object is proposed using the iterative reweighted least squares method.Experimental results show that this method can estimate the stiffness of grasped objects within 250 ms without contact sensors.
基金the National Natural Science Foundation of China(No.51879119)the Key Projects of National Key Research and Development Program(No.2021YFB390150)+1 种基金the Natural Science Project of Fujian Province(Nos.2022J01323,2021J01822 and 2020J01660)the Fuzhou-Xiamen-Quanzhou Independent Innovation Region Cooperated Special Foundation(No.3502ZCQXT2021007)。
文摘To achieve the track following and collision avoidance of underactuated unmanned surface vehicle(USV),autonomous navigation model based on model predictive control is established by including the track offset,speed variation and rule compliance as the evaluation functions and including the ship domain of dynamic/static navigation obstacles and the mechanical characteristics limitation as constraints.The effectiveness of the model for autonomous navigation of USV in the situation of multi-ship encounters and in the complex waters with both dynamic and static obstructions is verified by several groups of simulation work.The simulation results show that the proposed model can realize the autonomous navigation of the underactuated USV under the complex waters.
基金supported by the National Key Research and Development Program of China(Grant No.2024YFB3213600).
文摘Inspired by the crucial role of the tail in crocodile locomotion,we propose a novel rigid-flexible coupled tail structure design.The tail design reduces the number of required actuators,enables undulatory propulsion in swimming,and provides additional support during terrestrial crawling.However,when the tail lifts off the ground during land crawling,its flexible underactuated structure tends to oscillate randomly due to minimal damping.These oscillations impart disruptive reaction torques to the body,critically impairing locomotion stability.To tackle this issue,we employed the standard Denavit-Hartenberg(DH)method and Newton-Euler equations to formulate a rigid-flexible coupled dynamic model for the tail,in which distributed elastic forces are embedded as internal forces in the force balance equations.Based on this model,we propose an oscillation suppression strategy based on an energy-optimized Nonlinear Model Predictive Controller(NMPC)with a single joint torque as the control input.This controller solves a constrained multi-objective optimization problem to effectively suppress the underactuated oscillations of the tail.Finally,experimental comparisons validate the accuracy of the dynamic model,and simulations based on this model substantiate the effectiveness of the oscillation suppression strategy.
基金supported in part by the National Natural Science Foundation of China(62373208,62033003,62273105,U191140)Taishan Scholar Program of Shandong Province of China(tsqn202306218)+1 种基金the National Key Research and Development Program of China(2022YFB4703100)the National Natural Science Foundation of Shandong Province(ZR2024YQ032).
文摘A high-order fully actuated(HOFA)control method is developed for underactuated mechanical systems(UMSs)with model uncertainties and external disturbances.First,a model transformation is made from the original to a pseudo strict-feedback form,and an HOFA model is established by using the method of variable elimination.Then,a group of high-order extended state observers(ESOs)are designed to deal with model uncertainties and external disturbances.The HOFA model is further classified and decomposed to achieve output constraints within a finite time range,and a barrier function is designed by combining with a shift function.Additionally,an ESO-based HOFA tracking control strategy for UMS is proposed.Finally,a manipulator model is used to verify the effectiveness of the proposed control strategy.
基金Project(2008AA04Z203)supported by National High Technology Research and Development Program of China
文摘An underactuated finger structure actuated by tendon-driven system is presented.Kinematics and static analysis of the finger is done,and the results indicate that the prosthetic finger structure is effective and feasible.Based on the design of finger,a prosthetic hand is designed.The hand is composed of 5 independent fingers and it looks more like humanoid.Its size is about 85% of an adult's hand and weights about 350 g.Except the thumb finger,each finger is actuated by one DC motor,gear head and a tendon,and has three curling/extension joints.The thumb finger which is different from other existing prostheses is a novel design scheme.The thumb finger has four joints including three curling/extension joints and a joint which is used to realize the motion of the thumb related to the palm,and these joints are also driven by one DC motor,harmonic drive and a tendon.The underactuation and adaptive curling/extension motion of the finger are realized by joint torsion springs.A high-powered chip of digital signal processing(DSP)is the main part of the electrical system which is used for the motors control,data collection,communication with external controlling source,and so on.To improve the reliability of the hand,structures and sensors are designed and made as simply as possible.The hand has strong manipulation capabilities that have been verified by finger motion and grasping tests and it can satisfy the daily operational needs and psychological needs of deformities.
基金supported by National Natural Science Foundation of China (Nos. 51375504 and 61602539)the Program for New Century Excellent Talents in University
文摘In this study, we improved an underactuated finger mechanism by using Solidworks to simulate the grasp operation of a finger in some different situations. In addition, a robot palm is designed for the three-finger robot hand with the designed underactuated fingers. A Solidworks simulation was used to verify the rationality of the design. Some parts of the hand were modified to fit for 3D printing, and a prototype of the hand was produced by 3D printing, which could reduce the cost of the production process, as well as provide design flexibility and other advantages. Finally, some grasping experiments were made with the prototype. The results showed that the robot could grasp objects with different sizes, and further verified the rationality of the design and feasibility of fabricating the robot hand using 3D printing.
文摘The dynamics of classical robotic systems are usually described by ordinary differential equations via selecting a minimum set of independent generalized coordinates. However, different parameterizations and the use of a nonminimum set of （dependent） generalized coordinates can be advantageous in such cases when the modeled device contains closed kinematic loops and/or it has a complex structure. On one hand, the use of dependent coordinates, like natural coordinates, leads to a different mathematical representation where the equations of motion are given in the form of differential algebraic equations. On the other hand, the control design of underactuated robots usually relies on partial feedback linearization based techniques which are exclusively developed for systems modeled by independent coordinates. In this paper we propose a different control algorithm formulated by using dependent coordinates. The applied computed torque controller is realized via introducing actuator constraints that complement the kinematic constraints which are used to describe the dynamics of the investigated service robotic system in relatively simple and compact form. The proposed controller is applied to the computed torque control of the planar model of the ACROBOTER service robot. The stability analysis of the digitally controlled underactuated service robot is provided as a real parameter case study for selecting the optimal control gains.
文摘The underactuated fingers used in numerous robotic systems are evaluated by grasping force, configuration space, actuation method, precision of operation, compactness and weight. In consideration of all such factors a novel linkage based underactuated finger with a self-adaptive actuation mechanism is proposed to be used in prosthetics hands, where the finger can accomplish flexion and extension. Notably, the proposed mechanism can be characterized as a combination of parallel and series links. The mobility of the system has been analyzed according to the Chebychev-Grübler-Kutzbach criterion for a planar mechanism. With the intention of verifying the effectiveness of the mechanism, kinematics analysis has been carried out, by means of the geometric representation and Denavit-Hartenberg (D-H) parameter approach. The presented two-step analysis followed by a numerical study, eliminates the limitations of the D-H conversion method to analyze the robotics systems with both series and parallel links. In addition, the trajectories and configuration space of the proposed finger mechanism have been determined by the motion simulations. A prototype of the proposed finger mechanism has been fabricated using 3D printing and it has been experimentally tested to validate its functionality. The kinematic analysis, motion simulations, experimental investigations and finite element analysis have demonstrated the effectiveness of the proposed mechanism to gain the expected motions.
基金Higher Education Commission,Government of Paki-stan(1-3/PM-OVER/China/2005)
文摘In this article, a nonlinear model of an underactuated six degrees of freedom （6 DOF） quadrotor helicopter is derived on the basis of the Newton-Euler formalism. The derivation comprises determining equations of the motion of the quadrotor in three dimensions and approximating the actuation forces through the modeling of aerodynamic coefficients and electric motor dynamics. The derived model composed of translational and rotational subsystems is dynamically unstable, so a sequential nonlinear control strategy is used. The control strategy includes feedback linearization coupled with a PD controller for the translational subsystem and a backstepping-based PID nonlinear controller for the rotational subsystem of the quadrotor. The performances of the nonlinear control method are evaluated by nonlinear simulation and the results demonstrate the effectiveness of the proposed control strategy for the quadrotor helicopter in quasi-stationary flights.
基金supported by the National Natural Science Foundation (Grant No. 50435040 and 60675045)the National High Technology Research and Development Program (Grant No. 2006AA04Z228)the "111 Project" of China (No. B07018).
文摘When developing a humanoid myo-control hand,not only the mechanical structure should be considered to afford a high dexterity,but also the myoelectric (electromyography,EMG) control capability should be taken into account to fully accomplish the actuation tasks.This paper presents a novel humanoid robotic myocontrol hand (AR hand Ⅲ) which adopted an underac- tuated mechanism and a forearm myocontrol EMG method.The AR hand Ⅲ has five fingers and 15 joints,and actuated by three embedded motors.Underactuation can be found within each finger and between the rest three fingers (the middle finger,the ring finger and the little finger) when the hand is grasping objects.For the EMG control,two specific methods are proposed:the three-fingered hand gesture configuration of the AR hand Ⅲ and a pattern classification method of EMG signals based on a statistical learning algorithm-Support Vector Machine (SVM).Eighteen active hand gestures of a testee are recognized ef- fectively,which can be directly mapped into the motions of AR hand Ⅲ.An on-line EMG control scheme is established based on two different decision functions:one is for the discrimination between the idle and active modes,the other is for the recog- nition of the active modes.As a result,the AR hand Ⅲ can swiftly follow the gesture instructions of the testee with a time delay less than 100 ms.
基金Projects(51179035,51279221) supported by the National Natural Science Foundation of ChinaProject(2014M561333) supported by Postdoctoral Science Foundation of China
文摘Based on rational behavior model of three layers, a tracking control system is designed for straight line tracking which is commonly used in underwater survey missions. An intelligent PID control law implemented as planning level during the control system using transverse deviation is came up with. Continuous tracking of path expressed by a point sequence can be realized by the law. Firstly, a path tracking control system based on rational behavior model of three layers is designed, mainly satisfying the needs of underactuated AUV. Since there is no need to perform spatially coupled maneuvers, the 3D path tracking control is decoupled into planar 2D path tracking and depth or height tracking separately. Secondly, planar path tracking controller is introduced. For the reason that more attention is paid to comparing with vertical position control, transverse deviation in analytical form is derived. According to the Lyapunov direct theory, control law is designed using discrete PID algorithm whose parameters obey adaptive fuzzy adjustment. Reference heading angle is given as an output of the guidance controller conducted by lateral deviation together with its derivative. For the purpose of improving control quality and facilitating parameter modifying, data normalize modules based on Sigmoid function are applied to input-output data manipulation. Lastly, a sequence of experiments was carried out successfully, including tests in Longfeng lake and at the Yellow sea. In most challenging sea conditions, tracking errors of straight line are below 2 m in general. The results show that AUV is able to compensate the disturbance brought by sea current. The provided test results demonstrate that the designed guidance controller guarantees stably and accurately straight route tracking. Besides, the proposed control system is accessible for continuous comb-shaped path tracking in region searching.
基金Project(51409061)supported by the National Natural Science Foundation of ChinaProject(2013M540271)supported by China Postdoctoral Science Foundation+1 种基金Project(LBH-Z13055)Supported by Heilongjiang Postdoctoral Financial Assistance,ChinaProject(HEUCFD1403)supported by Basic Research Foundation of Central Universities,China
文摘The trajectory tracking control problem for underactuated unmanned surface vehicles(USV) was addressed, and the control system took account of the uncertain influences induced by model perturbation, external disturbance, etc. By introducing the reference, trajectory was generated by a virtual USV, and the error equation of trajectory tracking for USV was obtained, which transformed the tracking problem of underactuated USV into the stabilization problem of the trajectory tracking error equation. A backstepping adaptive sliding mode controller was proposed based on backstepping technology and method of dynamic slide model control. By means of theoretical analysis, it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property. Simulation results are presented to illustrate the effectiveness of the proposed controller.
基金Project(2013M540271)supported by the Postdoctoral Science Foundation of ChinaProject(HEUCF1321003)support by the Basic Research Foundation of Central University,ChinaProject(51209050)supported by the National Natural Science Foundation of China
文摘The trajectory planning and tracking control for an underactuated unmanned surface vessel(USV) were addressed.The reference trajectory was generated by a virtual USV,and the error equation of trajectory tracking for underactuated USV was obtained,which transformed the tracking and stabilization problem of underactuated USV into the stabilization problem of the trajectory tracking error equation.A nonlinear state feedback controller was proposed based on backstepping technique and Lyapunov's direct method.By means of Lyapunov analysis,it is proved that the proposed controller ensures that the solutions of closed loop system have the ultimate boundedness property.Numerical simulation results are presented to validate the effectiveness and robustness of the proposed controller.
文摘The trajectory-tracking control problem is inves-tigated for an autonomous underwater vehicle(AUV)moving in the vertical plane using an internal point mass and a rear thruster as actuators.Combined with the dynamics of the point mass,the AUV is modeled as an underactuated system.A Lyapunov-based tracking controller is proposed by using backstepping approach to stabilize the error dynamics and force the position errors to a small neighborhood of the origin.Simulation results validate the proposed tracking approach.
基金co-supported by the National Nature Science Foundation of China(No.’s 61403038 and 61573066)the National Basic Research Program of China(No.2013CB733000)
文摘Aiming at a space manipulator with free-swinging joint failure, a failure treatment strategy and fault-tolerant path planning method is proposed in this paper. This method can realize failure treatment of a space manipulator with free-swinging joint failure through determination of the optimal locked joint angle and dynamics model reconfiguration. Fault-tolerant path planning is realized by the establishment of the degraded workspace with integrated kinematics performance(DWWIKP) and an improved A-Star(A*) algorithm. This paper has the following contributions.The determination of the optimal locked joint angle can ensure that the manipulator is able to continue follow-up tasks while maximizing the workspace of the manipulator after locking the fault joint. Underactuated control of a high degree-of-freedom(DOF) manipulator can be effectively solved through dynamics model reconfiguration. The analysis process of the dynamics coupling relationship can be applied to cases where the active joint and the passive joint are parallel or perpendicular to each other. The establishment of the DWWIKP can demonstrate the kinematics performance of the manipulator in both joint space and operation space comprehensively. The improved A*algorithm based on the integrated kinematics performance index(IKPI) can search a fault-tolerant task trajectory that satisfies the requirements of reachability and the overall kinematics performance simultaneously. The method proposed in this paper is verified by a 7-DOF manipulator, and it is available to any DOF manipulator with free-swinging joint failure.
基金National Natural Science Foundation of China(Grant Nos.U1613216,61573333)
文摘Robot hands have been developing during the last few decades. There are many mechanical structures and analyti?cal methods for di erent hands. But many tough problems still limit robot hands to apply in homelike environment. The ability of grasping objects covering a large range of sizes and various shapes is fundamental for a home service robot to serve people better. In this paper, a new grasping mode based on a novel sucked?type underactuated(STU) hand is proposed. By combining the flexibility of soft material and the e ect of suction cups, the STU hand can grasp objects with a wide range of sizes, shapes and materials. Moreover, the new grasping mode is suitable for some situations where the force closure is failure. In this paper, we deduce the e ective range of sizes of objects which our hand using the new grasping mode can grasp. Thanks to the new grasping mode, the ratio of grasping size between the biggest object and the smallest is beyond 40, which makes it possible for our robot hand to grasp diverse objects in our daily life. For example, the STU hand can grasp a soccer(220 mm diameter, 420 g) and a fountain pen(9 mm diameter, 9 g). What’s more, we use the rigid body equilibrium conditions to analysis the force condition. Experiment evaluates the high load capacity, stability of the new grasping mode and displays the versatility of the STU hand. The STU hand has a wide range of applications especially in unstructured environment.
