Bai Chen

A Biomimetic Spermatozoa Propulsion Method for Interventional Micro Robot

Nowadays, studies of the interventional micro robots have been hot topics in the field of medical device. The ultimate goal of medical micro robots is to reach currently inaccessible areas of the human body and carry out a host of complex operations such as minimally invasive surgery (MIS), highly localized drug delivery and opening up the blood vessels. Miniature, safe and energy efficient propulsion systems hold the key to mature this technology. In this paper, a prototype of endovascular micro robot based on the motion principle of spermatozoa is presented. The properties of this propulsive mechanism are estimated by modeling the dynamics of the swimming methods. In order to validate the theoretical results for spermatozoa propulsion, a scaled-up prototype of the swimming robot is fabricated and characterized in imitative bio-pipes full of silicone oil. Experimental results shown that the spermatozoa-like micro robot can be controlled to swim efficiently. And to adjust the rotation direction of the four flexible tails, the propulsion forces and the function of opening up the blood vessels will be generated.

Research on the Kinematic Properties of a Sperm-Like Swimming Micro Robot

Nowadays, it has been one of the hottest topics for scientists to research the interventional micro robots operating in human lumen. In this paper, a novel sperm-like interventional swimming robot with single tail is presented. The kinematic models of the sperm-like helical swimming modes are built, and the motion principles are analyzed numerically. Positions and orientations are displayed graphically during the single-tail micro robot swims in liquid. Also, the displacements and the swimming velocities of the robot in x, y, z directions are plotted. It is shown that, when the single flexible tail screws in liquid environment, it generates both axial and radial propulsion forces, thus to cause the axial and the radial movements. In order to make the swimming micro robot more controllable, an improved sperm-like swimming intervention micro robot with four flexible tails is fabricated and characterized in pipes filled with silicone oil. Experimental results show that the sperm-like micro robot can swim efficiently. With different combinations of the tails’ rotation directions, the robot can gain excellent controlled performance.

Trajectory Tracking Control of Underwater Vehicle-Manipulator System Using Discrete Time Delay Estimation

A new nonlinear robust control scheme is proposed and investigated for the trajectory tracking control problem of an underwater vehicle-manipulator system (UVMS) using the discrete time delay estimation (DTDE) technique. The proposed control scheme mainly has two parts: the DTDE part and the desired dynamics part. The former one is applied to properly estimate and compensate the complex unknown lumped dynamics of the system, using the intentionally time-delayed system’s information. The latter one is used to obtain the desired dynamic characteristic of the closed-loop control system. Thanks to the DTDE technique, the proposed control scheme no longer requires the detailed system dynamic information or the acceleration signals, bringing in good feasibility for actual applications and satisfactory control performance. The stability of the closed-loop control system is analyzed and proved using the bounded input bounded out stability theory. Finally, nine degree of freedoms (DOFs) simulation and seven DOFs pool experiment studies were conducted to demonstrate the effectiveness of the proposed control scheme with an UVMS developed in our laboratory. Corresponding results show that our proposed control scheme can ensure satisfactory control performance with relative small control gains and obtain a precision of 0.064 m for the end effector in the task space.

A new discrete time delay control of hydraulic manipulators

A new discrete time delay control design is presented and investigated for the joint-space control of hydraulic manipulators in this article. Thanks to the time delay estimation technique, our new designed controller no longer needs the detailed system model, which is very fascinating for practical applications. Also, the proposed discrete time delay control method requires no acceleration information to be obtained through quadratic differential, which is usually essential for the continuous-time version time delay control method of hydraulic manipulators. This may result in fewer requirements of computational effort or unavailability of sensors for obtaining the acceleration signal. Furthermore, the newly proposed discrete time delay control requires no future predicted values of the desired trajectory or system states compared with the traditional discrete time delay control method, which is more suitable for practical applications. The corresponding stability is analyzed using the bounded input bounded output stability theory. The easiness for actual applications and robustness against disturbance are verified through some 2-degree-of-freedom experiments.

Joint space tracking control of underwater vehicle-manipulator systems using continuous nonsingular fast terminal sliding mode

To ensure satisfactory control performance for the underwater vehicle-manipulator systems, a novel continuous nonsingular fast terminal sliding mode controller is proposed and investigated using time delay estimation in this article. Complex lumped unknown dynamics including the strong nonlinear couplings and external disturbance are properly compensated with time delay estimation, which are mainly based on the time-delayed signals of underwater vehicle-manipulator systems and can provide with a fascinating model-free feature. Afterwards, the satisfactory tracking control performance and good robustness under heavy lumped uncertainties are ensured using the continuous nonsingular fast terminal sliding mode term with a fast terminal sliding mode–type reaching law. Therefore, the proposed controller is easy to use thanks to time delay estimation, and can ensure good control performance owing to continuous nonsingular fast terminal sliding mode. Stability of the closed-loop control system is analyzed using Lyapunov stability theory, and theoretical tracking errors are calculated and presented. Finally, the effectiveness and advantages of the proposed controller are demonstrated through comparative 7-degree-of-freedom pool experiments.

A new continuous fractional-order nonsingular terminal sliding mode control for cable-driven manipulators

Abstract To ensure satisfactory control performance for the cable-driven manipulators under complex lumped uncertainties, a new continuous fractional-order nonsingular terminal sliding mode (CFONTSM) control scheme based on time delay estimation (TDE) is proposed and studied in this paper. The proposed control scheme contains three elements, a TDE element adopted to suitably cancel out the unknown lumped dynamics with purposely time-delayed signals of the closed-loop control system, a newly proposed FONTSM manifold adopted to realize finite-time convergence in the sliding mode phase and a fast-TSM-type reaching law adopted to ensure finite-time convergence in the reaching phase. The proposed control scheme is model-free and no longer needs system dynamics benefiting from TDE, which is very suitable and easy to use in practical applications. Meanwhile, high precision, fast convergence and good robustness against lumped uncertainties are ensured thanks to the newly proposed FONTSM manifold and adopted fast-TSM-type reaching law. Integrated stability analysis of the closed-loop control system is presented based on Lyapunov stability theory. Finally, the effectiveness of our proposed control scheme is demonstrated by comparative 2-DoFs (degrees-of-freedom) simulation and experiments.

Time delay control of cable-driven manipulators with adaptive fractional-order nonsingular terminal sliding mode

Abstract For the high performance control of cable-driven manipulators, a novel time delay control (TDC) scheme with adaptive fractional-order nonsingular terminal sliding mode (AFONTSM) is presented and studied in this work. The presented control scheme uses time delay estimation (TDE) as its basic framework, which can effectively obtain a fascinating model-free feature just using the time-delayed information of the closed-loop control system. Afterwards, a novel AFONTSM control scheme is applied to provide with good comprehensive performance under complicated lumped disturbance in both reaching and sliding phases. The presented control method can be easily applied in real situations thanks to TDE, meanwhile satisfactory control performance can be guaranteed benefiting from the adopted AFONTSM error dynamics. Stability analysis is given based on Lyapunov stability theory. Finally, the effectiveness and superiorities of our newly designed control scheme are validated through 2-DOFs (degree of freedoms) comparative simulations and experiments.

Practical continuous fractional-order nonsingular terminal sliding mode control of underwater hydraulic manipulators with valve deadband compensators:

For the multi-degrees of freedom control problem of underwater hydraulic manipulators with non-ignorable valve deadband and strong lumped nonlinearities and uncertainties, a practical continuous fractional-order nonsingular terminal sliding mode control design together with a deadband compensator is presented and studied. The presented method contains three parts a time delay estimation utilized to nearly estimate and compensate the extremely complicated system dynamics, a continuous fractional-order nonsingular terminal sliding mode used to ensure high control performance against the strong lumped nonlinearities and uncertainties, and a valve deadband compensator used to compensate for the non-ignorable valve deadband. The proposed method is model-free thanks to the time delay estimation, and can ensure satisfactory control performance thanks to the continuous fractional-order nonsingular terminal sliding mode and deadband compensator. Stability of the closed-loop control system including the deadband compensator is proved rigorously. Finally, practical 2-degrees of freedom experiments are performed, and corresponding results effectively demonstrate the superiorities of the newly presented controller with deadband compensator.

A novel variable-stiffness flexible manipulator actuated by shape memory alloy for minimally invasive surgery

This article presents a novel variable-stiffness flexible manipulator for minimally invasive surgery. Each module of the proposed manipulator contains a variable-stiffness mechanism actuated by proactive deformation of shape memory alloy. Due to low driving current, apparent mechanical deformation, suitable phase transformation temperature and biocompatibility of shape memory alloy wire actuation, it is well suited for the manipulator applied in minimally invasive surgery, where variable stiffness is urgently required. In this article, the conceptual design, elastic modulus model, thermo-electric model, stiffness controlling method and finite element method simulation for a single module of the proposed variable-stiffness flexible manipulator are presented. Moreover, the memory shape setting experiment of shape memory alloy wire and fabrication of the single module are carried out. Finally, stiffness characterizations of the mechanism and the single module are studied separately, theoretically and experimentally.

Kinematics optimization and static analysis of a modular continuum robot used for minimally invasive surgery

For the outstanding compliance and dexterity of continuum robot, it is increasingly used in minimally invasive surgery. The wide workspace, high dexterity and strong payload capacity are essential to the continuum robot. In this article, we investigate the workspace of a cable-driven continuum robot that we proposed. The influence of section number on the workspace is discussed when robot is operated in narrow environment. Meanwhile, the structural parameters of this continuum robot are optimized to achieve better kinematic performance. Moreover, an indicator based on the dexterous solid angle for evaluating the dexterity of robot is introduced and the distal end dexterity is compared for the three-section continuum robot with different range of variables. Results imply that the wider range of variables achieve the better dexterity. Finally, the static model of robot based on the principle of virtual work is derived to analyze the relationship between the bending shape deformation and the driven force. The simulations and experiments for plane and spatial motions are conducted to validate the feasibility of model, respectively. Results of this article can contribute to the real-time control and movement and can be a design reference for cable-driven continuum robot.