Dynamic surface control-backstepping based impedance control for 5-DOF flexible joint robots

A new impedance controller based on the dynamic surface control-backstepping technique to actualize the anticipant dynamic relationship between the motion of end-effector and the external torques was presented.Comparing with the traditional backstepping method that has "explosion of terms" problem,the new proposed control system is a combination of the dynamic surface control technique and the backstepping.The dynamic surface control(DSC) technique can resolve the "explosion of terms" problem that is caused by differential coefficient calculation in the model,and the problem can bring a complexity that will cause the backstepping method hardly to be applied to the practical application,especially to the multi-joint robot.Finally,the validity of the method was proved in the laboratory environment that was set up on the 5-DOF(degree of freedom) flexible joint robot.Tracking errors of DSC-backstepping impedance control that were 2.0 and 1.5 mm are better than those of backstepping impedance control which were 3.5 and 2.5 mm in directions X,Y in free space,respectively.And the anticipant Cartesian impedance behavior and compliant behavior were achieved successfully as depicted theoretically.

A novel grasping force control strategy for multi-fingered prosthetic hand

A grasping force control strategy is proposed in order to complete various fine manipulations by using anthropomorphic prosthetic hand.The position-based impedance control and force-tracking impedance control are used in free and constraint spaces,respectively.The fuzzy observer is adopted in transition in order to switch control mode.Two control modes use one position-based impedance controller.In order to achieve grasping force track,reference force is added to the impedance controller in the constraint space.Trajectory tracking in free space and torque tracking in constrained space are realized,and reliability of mode switch and stability of system are achieved.An adaptive sliding mode friction compensation method is proposed.This method makes use of terminal sliding mode idea to design sliding mode function,which makes the tracking error converge to zero in finite time and avoids the problem of conventional sliding surface that tracking error cannot converge to zero.Based on the characteristic of the exponential form friction,the sliding mode control law including the estimation of friction parameter is obtained through terminal sliding mode idea,and the online parameter update laws are obtained based on Lyapunov stability theorem.The experiments on the HIT Prosthetic Hand IV are carried out to evaluate the grasping force control strategy,and the experiment results verify the effectiveness of this control strategy.

Optimal measurement configurations for kinematic calibration of six-DOF serial robot

An optimal measurement pose number searching method was designed to improve the pose selection method.Several optimal robot measurement configurations were added to an initial pre-selected optimal configuration set to establish a new configuration set for robot calibration one by one.The root mean squares (RMS) of the errors of each end-effector poses after being calibrated by these configuration sets were calculated.The optimal number of the configuration set corresponding to the least RMS of pose error was then obtained.Calibration based on those poses selected by this algorithm can get higher end-effector accuracy,meanwhile consumes less time.An optimal pose set including optimal 25 measurement configurations is found during the simulation.Tracking errors after calibration by using these poses are 1.54,1.61 and 0.86 mm,and better than those before calibration which are 7.79,7.62 and 8.29 mm,even better than those calibrated by the random method which are 2.22,2.35 and 1.69 mm in directions X,Y and Z,respectively.

HIT anthropomorphic robotic hand and finger motion control

Nowadays many anthropomorphic robotic hands have been put forward. These hands emphasize different aspects according to their applications. HIT Anthropomorphic Robotic Hand (ARhand) is a simple, lightweight and dexterous design per the requirements of anthropomorphic robots. Underactuated self-adaptive theory is adopted to decrease the number of motors and weight. The fingers of HIT ARhand with multi phalanges have the same size as those of an adult hand. Force control is realized with the position sensor, joint torque sensor and fingertip torque sensor. From the 3D model, the whole hand, with the low power consumption DSP control board integrated in it, will weigh only 500 g. It will be assembled on a BIT-Anthropomorphic Robot.

Space gripper configuration and its dimension synthesis based on genetic algorithm

The special fingers of the gripper on the space robot have been developed based on genetic algorithmfor the space application.Therefore,the symmetrical wedgelike finger composed of the 4-1ink mechanismand the relevant track were designed.To decrease the weight and optimize the kinematics and grip force,the compositive fitness function for dynamics and kinematics was created.The calculation efficiency couldbe improved by novel methods which overcame the problem of too many constraints in the solution space,such as introducing the specialist's experience and punishment function and simplifying the variables.The solutions show that the optimized finger could perform well and the methods were effectual.

Design and Control of a Coupling Mechanism-Based Prosthetic Hand

A five-fingered,multi-sensory and biomimetic hand is presented.The cambered palm is specially designed by utilizing the knowledge of anatomy.The position of each finger is arranged according to human hand skeleton.Each finger with three phalanges could fulfill flexion-extension movement independently.All the fingers are designed using coupling link mechanism.The location of the thumb is designed by maximizing interaction area between the thumb and other fingers.The opposite thumb could grasp along a cone surface,while maintaining its function.The hardware architecture is divided into control system and human-machine interaction system.The mechanical parts,sensors and motion control systems are integrated in the hand structure.In addition,a skin-like glove is designed,which makes the hand more humanlike.According to our primary experimental results,the hand can accomplish several grasp modes by applying an intuitive surface electromyography control scheme.The success rate of 10 modes is up to 90%.

An anthropomorphic controlled hand prosthesis system

Based on HIT/DLR(Harbin Institute of Technology/Deutsches Zentrum für Luft-und Raumfahrt) Prosthetic Hand II,an anthropomorphic controller is developed to help the amputees use and perceive the prosthetic hands more like people with normal physiological hands.The core of the anthropomorphic controller is a hierarchical control system.It is composed of a top controller and a low level controller.The top controller has been designed both to interpret the amputee's intensions through electromyography(EMG) signals recognition and to provide the subject-prosthesis interface control with electro-cutaneous sensory feedback(ESF),while the low level controller is responsible for grasp stability.The control strategies include the EMG control strategy,EMG and ESF closed loop control strategy,and voice control strategy.Through EMG signal recognition,10 types of hand postures are recognized based on support vector machine(SVM).An anthropomorphic closed loop system is constructed to include the customer,sensory feedback system,EMG control system,and the prosthetic hand,so as to help the amputee perform a more successful EMG grasp.Experimental results suggest that the anthropomorphic controller can be used for multi-posture recognition,and that grasp with ESF is a cognitive dual process with visual and sensory feedback.This process while outperforming the visual feedback process provides the concept of grasp force magnitude during manipulation of objects.