Flexible Robot Arm Research Articles

Modeling and Active Vibration Control of Flexible Robotic Arm and Its Application in Agricultural Water Conservancy Field

In order to improve the modeling and active vibration control effectiveness of flexible manipulators, this paper combines big data technology to study the modeling and active control of flexible manipulators. In addition, this article decouples the dynamic model of the flexible joint manipulator based on voltage control method, redefines the control input of the system as the voltage of the joint motor, and uses a nonlinear state observer to control the flexible link manipulator. The control strategy proposed in this article is based on a nonlinear state observer, combined with input-output control, to achieve tracking of joint angular displacement in a flexible linkage manipulator. Through experimental research, it can be seen that the big data based modeling and active vibration control research system for flexible robotic arms proposed in this paper can effectively improve the motion control effect of flexible robotic arms.

Modeling and Rotation Control Strategy for Space Planar Flexible Robotic Arm Based on Fuzzy Adjustment and Disturbance Observer

In precise space operation tasks, the impact of disturbing torques on the space flexible robotic arm (SFRA) cannot be ignored. Besides, the slender structure of the SFRA is very likely to generate vibration of the robotic arm. These are all potential hidden dangers in space safety. To quantify the potential risk, an accurate dynamics model of the SFRA considering the disturbing torque is built by Lagrange principle and the assumed modal method (AMM). Moreover, the effects of the disturbing torque, modal order and nonlinear terms on the deformation accuracy of the SFRA are compared. It is observed that the simplified dynamics model with neglecting the nonlinear terms (NNTs) has a high model accuracy and be easily solved. Therefore, the NNTs simplified model is chosen for deriving the transfer function of the SFRA. The parameters of the PI controller are adjusted in real time based on fuzzy rules to reduce the tracking error in the SFRA. In addition, the disturbance observer is designed to observe and compensate of the disturbance torque in the SFRA. The control method of adjusting controller parameters with fuzzy rules based on the disturbance observer greatly improves the rotational control accuracy of the SFRA. Finally, the validity of aforementioned control strategy is confirmed by simulation analysis and experimental results.

Flexible, lightweight, tunable robotic arms enabled by X-tensegrity inspired structures

Robotic arms have remarkable applications in diverse fields such as medical rehabilitation, disaster relief, and space exploration. Enhancing their rigidity, load-bearing capacity, and motion simplicity is key to broadening their usage. Utilizing the admirable flexibility and strength of tensegrity structures, made of rigid bars and elastic strings, we introduce a new type of flexible robotic arm. This arm is constructed using a sequence of two-dimensional X-tensegrity inspired modules. Each module comprises two sets of triangular bars linked by three strings, enhancing the arm’s ability to deform and resist impact forces. The joints between modules are stiff, allowing for angular adjustments to create three-dimensional configurations with adjustable stiffness and curvature. Through theoretical analysis, simulations, and experiments, we have shown that this tensegrity-based robotic arm exhibits superior stability, flexibility, and scalability.

Effects of prestress in the coating of an elastic disk

An elastic disk is coated with an elastic rod, uniformly prestressed with a tensile or compressive axial force. The prestress state is assumed to be induced by three different models of external radial load or by ‘shrink-fit’ forcing the coating onto the disk. The prestressed coating/disk system, when loaded with an additional and arbitrary incremental external load, experiences incremental displacement, strain, and stress, which are solved via complex potentials. The analysis incorporates models for both perfect and imperfect bonding at the coating/disk interface. The derived solution highlights the significant influence not only of the prestress but also of the method employed to generate it. These two factors lead, in different ways, to a loss or an increase in incremental stiffness for compressive or tensile prestress. The first bifurcation load of the structure (which differs for different prestress generations) is determined in a perturbative way. The results emphasize the importance of modelling the load and may find applications in flexible electronics and robot arms subject to pressure or uniformly-distributed radial forces.

Dynamic Modeling and Optimization Analysis of Rigid–Flexible Coupling Manipulator Based on Assumed Mode Method

Lightweight robotic arms are one of the main technologies to improve the working performance of robotic arms in the future. Focusing on the spatial vibrations issue brought about by the light-weighting of a space robotic arm in this paper, a rigid–flexible coupling dynamics model of a space robotic arm system was established based on the assumed mode method and Lagrange method. Based on the lightweight flexible robotic arm structure, a comparative analysis of the first four mode functions was conducted under different fixed constraints and physical properties to determine the mode order that matches the simulation analysis of this robotic arm, thus, further simplifying the rigid–flexible coupling dynamics equations of the system. The overall rigid model and simplified dynamic model of the robotic arm system were solved by using MATLAB, resulting in a motion trajectory of the flexible arm end in space. The three-dimensional model was validated and simulated using virtual prototype technology under the same joint inputs as the model in MATLAB. The simulation results demonstrated that the trajectory of the end of the flexible arm was basically the same between simplified dynamics model simulation and virtual prototype simulation, and the maximum deviation of the end trajectories of the flexible connecting rods [Formula: see text] and [Formula: see text] was less than 18[Formula: see text]mm and 58[Formula: see text]mm, respectively. Meanwhile, the trajectory trend of the end of the flexible arm in the two aforementioned models was the same as the simulation results of the ideal model (overall rigid model). The above conclusions can verify the correctness of the mathematical model of dynamics obtained from the calculations in this paper. In addition, the research data showed that the maximum vibration deviation of the flexible arm was stabilized within a certain value range under different joint inputs, and this research also provided theoretical support for the late vibration suppression control of the spatial rigid–flexible coupled robotic arm.

H∞ control of switched Lurie systems with dwell time

This article deals with the [Formula: see text] control problems of switched Lurie systems. Our purpose is to design switching signals and state feedback controllers with time-varying control gains that make the closed-loop switched Lurie systems absolutely stable. Based on switched time-varying Lyapunov–Lurie function, time-varying controllers corresponding to two kinds of switching signals are proposed. On this basis, the control synthesis conditions are given. It is worth mentioning that our results can deal with the situation that all subsystems are not stabilizable. Finally, the obtained results are applied to a flexible joint robotic arm model with switchings of parameter values. Another simulation example of switched Lurie systems is considered to illustrate the validity of the presented approaches.

A Pneumatic-Actuated Flexible Robotic Arm With Rigid Backbone for High-Precision and Safe Manipulation

A Pneumatic-Actuated Flexible Robotic Arm With Rigid Backbone for High-Precision and Safe Manipulation

The Structure and Application of a Flexible Manipulator Based on Octopus Biomimetics

With the gradual development of modern science and technology, robotic arms have become increasingly important equipment, which can replace humans to complete various tasks. It has played an important role in many fields such as science, military, and industry. But the traditional rigid manipulator is often limited in some special working environments. With the development of Bionics, people find that flexible manipulator has better performance in the special working environment. This article studies the mechanical structure, driving mode, control mode, and bionic suction cup of the octopus’s biomimetic robotic arm, and conducts application analysis in three aspects: underwater rescue, narrow space operation, and fire rescue. It has been proven that flexible robotic arms have higher flexibility and larger motion space than rigid robotic arms. The octopus’s biomimetic robotic arm has high flexibility and large load-bearing capacity, which has great research significance in dealing with special working environments such as narrow spaces.

Decentralized event-triggered estimation of nonlinear systems

We investigate the scenario where a perturbed nonlinear system transmits its output measurements to a remote observer via a packet-based communication network. The sensors are grouped into N nodes and each of these nodes decides when its measured data is transmitted over the network independently. The objective is to design both the observer and the local transmission policies in order to obtain accurate state estimates, while only sporadically using the communication network. In particular, given a general nonlinear observer designed in continuous-time satisfying an input-to-state stability property, we explain how to systematically design a dynamic event-triggering rule for each sensor node that avoids the use of a copy of the observer, thereby keeping local calculation simple. We prove the practical convergence property of the estimation error to the origin and we show that there exists a uniform strictly positive minimum inter-event time for each local triggering rule under mild conditions on the plant. The efficiency of the proposed techniques is illustrated on a numerical case study of a flexible robotic arm.

Adaptive Fuzzy Command Filtered Tracking Control for Flexible Robotic Arm with Input Dead-Zone

In this paper, an adaptive fuzzy tracking control method is proposed to address the issues of dead-zone and unobservable states in a flexible robotic arm system. The control design process begins with the utilization of a fuzzy logic system to approximate the nonlinear functions present in the flexible robotic arm system. To estimate the unobservable states of the system, a state observer is then designed. To alleviate the computational complexity during controller design, the command filtering technique is introduced. Additionally, the Nussbaum function is incorporated to address the unknown control gain problem. The stability of the system can be verified through the design of a Lyapunov function. This study’s simulation results demonstrate that the designed control system can closely track the specified reference signals. The closed-loop system effectively controls the flexible robotic arm, as verified through experimentation.

A Review of the Flexible Robotic Arm

In the application of the robot, the gripper of the robot is an important medium between robot arm and target. The traditional manipulator hand is mostly rigid, which is easy to damage or unable to clamp the object in the operation process. What are demanded from robotics are no longer limited to just mechanical assistant, more efficient and precise target acquisition of robotics with self-adaptation and self-adjustment have become the tackle key in robot research and design. In this paper, the design of flexible materials, the AI real-time sensing and controlling of flexible manipulator are described, as well as the application and prospects are analyzed. It is intended to provide perspective and direction for the weak interaction between flexible robotic arm and environment, less adaptability and inflexibility in complex environment. In the future, a more advanced, flexible robotic arm can be created that goes even beyond the human arm and contributes to development of the world.

Research on Dynamic Modeling Method of Single Linkage Flexible Robotic Arm

In this paper, a dynamics modeling method is proposed for a single-link flexible robotic arm. Firstly, the dynamic equation of the flexible manipulator system is deduced by using the Lagrange equation, secondly, the nonlinear model of the single-link flexible robotic arm is obtained by separating the spatio-temporal variables using the assumed modes method, and the model is verified by the Quanser flexible robotic arm experimental platform. Finally, the model is modified for the dead zone of the actuator found in the experimental process, which improves the accuracy of the model.

Slide-Gate Type Multi-Port Switching Valve

In a typical pneumatic soft actuation system, the control valve is often heavy and expensive, making a compact and economical control valve highly desirable. In addition to improving the valve itself, reducing the number of valves required can also be beneficial. To address this requirement, this study proposes and tests a multi-port switching valve based on a slide-gate mechanism. This valve is designed to enable the supply or exhaust of multiple actuators simultaneously, thereby reducing the number of valves required to drive a complex pneumatic actuator with multiple chambers. The main components of the proposed valve are a rotational cam, multiple ports, and 12 gate pins. The construction and operating principle of the valve and a design method for a rotational cam are described in this study. Furthermore, the results of the designed valve for radial bending and extension of a flexible robot arm are also reported.

Improved Dynamic Event-Triggered Robust Control for Flexible Robotic Arm Systems with Semi-Markov Jump Process

In this paper, we investigate the problem of a dynamic event-triggered robust controller design for flexible robotic arm systems with continuous-time phase-type semi-Markov jump process. In particular, the change in moment of inertia is first considered in the flexible robotic arm system, which is necessary for ensuring the security and stability control of special robots employed under special circumstances, such as surgical robots and assisted-living robots which have strict lightweight requirements. To handle this problem, a semi-Markov chain is conducted to model this process. Furthermore, the dynamic event-triggered scheme is used to solve the problem of limited bandwidth in the network transmission environment, while considering the impact of DoS attacks. With regard to the challenging circumstances and negative elements previously mentioned, the adequate criteria for the existence of the resilient H∞ controller are obtained using the Lyapunov function approach, and the controller gains, Lyapunov parameters and event-triggered parameters are co-designed. Finally, the effectiveness of the designed controller is demonstrated via numerical simulation using the LMI toolbox in MATLAB.

Vibration Control Using Modern Control System for Hybrid Composite Flexible Robot Manipulator Arm

In this research, a model of a robotic manipulator flexible structure and an equation of motion for controller design is planned. The structural material for the robot structure is chosen as a hybrid composite for this investigation along with a comparison study is carried out for the aluminium 6082 alloy of flexible manipulator arm application. To analyses, the vibration behavior and control implementation by adding joint flexibility in the system is organized. Using simulation algorithm, system parameter calculation is carried out through MATLAB software for vibration amplitude, transient period, steady-state error, and settling time of flexible robotic arm system. In a systematized way of motion equation, flexible robotic deflections are organized via the assumed mode (AM) and Lagrange techniques (LT). The graph analysis of hybrid composite and AL6082 materials with high stiffness coefficients is plotted. These obtained values from the plot are utilized for Linear Quadratic Regulator (LQR) controller design. The LQR output facts for both aluminium structural robotic arm and composite material robotic arms are established.

Modeling and fuzzy control of flexible manipulator link with moving end effector

In this paper, a flexible robotic arm system was designed and constructed based on the aspect ratio of flexible arms. The mathematical modeling was derived using finite element method. In addition, necessary information about the dynamic behavior of the suggested system was collected and used to design controllers based on knowledge of fuzzy logic theory. The purpose of building the flexible robotic arm was to perform different movements while ensure the accuracy of the derived mathematical dynamic model. This was achieved by comparing the experimental responses with theoretical ones where both systems were controlled through control strategies designed on the basis of fuzzy logics. The resulted control system is a 2-input, 1-output system. Different fuzzy controllers were suggested in addition to the non-conventional fuzzy control method (Fuzzy Control). This includes traditional-fuzzy control method with PID as well as PD controllers.The results showed that the error ratio between theoretical and practical responses does not exceed 16% in Fuzzy Control method and 11% in the PD-Fuzzy Control and 9% in the PID-Fuzzy Control method. This mismatch is due to the nonlinearities and friction effects between the different mechanical parts that have not be considered. In addition, the overshoot percentage also does not exceed 7% in the first and second methods and 8% in the third method. All outcomes are scientifically discussed and analyzed to obtain the best approach to design a high performance flexible robotic arm system.

Polarity assignment method (PAM), ANN, Neural networks strategy for the data of PAM for the single degree of freedom flexible joint robot

This paper “describes” the investigation of the stability of a single Degree of Freedom (DOF) flexible robotic arm by the diagrams shown below. The derived model is based on Euler- Lagrange approach. Exploration of a flexible robotic arm with using state-of-the-art controllers is essential for intelligent applications. These robot arms have joints that work independently of each other in order to create a smooth connection between joints. They still ensures the natural properties like a real human arm. The use of polarity assignment method “helps” the system to achieve desired output signals which has not been thoroughtly studied before for this system. The author can also compare the effectiveness of control methods for this system to find the most effective method for control strategies. In particular, ANN ( artificial neural network) is the most modern technique currently applied to this system to investigate the security and stability of the system through this program. This is new and it has never been used before for a system of this type. Neural networks strategy has been implemented in this paper as an application of artificial intelligence. It has successfully performed a mission in re-simulating functions of another control method: Polarity assignment method. Simulation results are done by Matlab.

Research on force and position control performance of the tendon sheath system with time-varying parameters and flexible robotic arms.

The tendon-sheath-system (TSS) is an excellent medium for remote power transmission, which is widely used in laparoscopic surgery robots. Since the operation process requires the robot to move continuously, this time-varying characteristic further aggravates the force and position transmission loss caused by the nonlinear friction of TSS, which affects the control accuracy of the surgical robot. A time-varying tendon-sheath transmission model (RT model) is proposed. A feedforward control system is designed to improve tendon-sheath transmission accuracy. Furthermore, a tendon-sheath transmission model with velocity characteristics (RV model) is established. Force, position, and velocity experiments were carried out on the platform of TSS with a robotic arm. The results show that the R-square values of force and position compensation are at least 96.57% and 99.16%. The proposed RT and RV models are effective in compensating for the TSS transmission loss during the operation of the surgical robot.

Dynamic Analysis of Flexible two Link Robotic Arm Considering Joint Stiffness

The robotic manipulator is a machine that can perform a variety of tasks according to specifications without the need of human interference. In order to model and control such devices, vibration analysis of flexible manipulators has become a critical field of study. The finite element approach has been used to analyze single and double connection flexible manipulators made of advanced composite material in the current study. For the modelling and study of the versatile composite manipulators, a three-noded beam feature is used. The effects of the taper angles of tapered flexible composite manipulators on the final product effector movement and vibration has been considered. In present work CATIA V5 is used to model the flexible single link robotic arm and static structural analysis to find stress and total deformation, dynamic analysis is carried out to find different modes, corresponding frequency, and life estimation of flexible single and double link robotic arm and also material optimization is done using different material composition for structural steel, aluminium and CFRP composite material using ANSYS WORKBENCH 18.2 (Finite Element Approach) for life estimation and evaluation using analytical approach.

Achieving near-infrared-light-mediated switchable friction regulation on MXene-based double network hydrogels

AbstractMXene possesses great potential in enriching the functionalities of hydrogels due to its unique metallic conductivity, high aspect ratio, near-infrared light (NIR light) responsiveness, and wide tunability, however, the poor compatibility of MXene with hydrogels limits further applications. In this work, we report a uniformly dispersed MXene-functionalized poly-N-isopropylacrylamide (PNIPAM)/poly-2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) double network hydrogel (M—DN hydrogel) that can achieve switchable friction regulation by using the NIR light. The dispersity of MXene in hydrogels was significantly improved by incorporating the chitosan (CS) polymer. This M—DN hydrogel showed much low coefficient of friction (COF) at 25 °C due to the presence of hydration layer on hydrogel surface. After illuminating with the NIR light, M—DN hydrogel with good photothermal effect rapidly raised the temperature to above the lower critical solution temperature (LCST), which led to an obvious increase of surface COF owing to the destruction of the hydration layer. In addition, M—DN friction control hydrogel showed good recyclability and controllability by tuning “on-off” of the NIR light. This work highlights the construction of functional MXene hydrogels for intelligent lubrication, which provides insight for interface sensing, controlled transmission, and flexible robotic arms.