Forward Kinematics and Control of a Segmented Tunable-Stiffness 3-D Continuum Manipulator

Many small and large industries use robot arms to establish a range of tasks such as picking and placing, and painting in today's world. However, to complete these tasks, one of the most critical problems is to obtain the desire position of the robot arm's end-effector. There are two methods for analyzing the robot arm: forward kinematic analysis and inverse kinematic analysis. This study aims to model the forward and inverse kinematic of an open-source 4 degrees of freedom (DoF) articulated robotic arm. A kinematic model is designed and further evaluated all the joint parameters to calculate the end-effector's desired position. Forward kinematic is simple to design, but as for the inverse kinematic, a closed-form solution is needed. The developed kinematic model's performance is assessed on a simulated robot arm, and the results were analyzed if the errors were produced within the accepted range. At the end of this study, forward kinematic and inverse kinematic solutions of a 4-DoF articulated robot arm are successfully modeled, which provides the theoretical basis for the subsequent analysis and research of the robot arm.

Soft Continuum manipulators are increasingly popular because of their ability to interact safely with humans, maneuver around obstacles and enable cost-effective operation. In this paper, we investigate a unique manipulator composed of two asymmetric fiber reinforced pneumatic building blocks, one capable of bending and the other axially rotating. The combination of these building blocks can yield spatial motion including helical deformation pattern. While this design architecture is beneficial for whole arm manipulation and grasping, the asymmetric combination introduces structural coupling between the two modes rendering an analytical model hard to formulate. In this paper, we propose a Cosserat rod model to capture the deformation of the manipulator whose material properties and actuation parameters are estimated through extensive experiments. Once the model parameters are determined, the Cosserat model can be used to estimate deformation profile even in the presence of external loads. Such a framework is general and can be applied to obtain the forward and inverse kinematics of any continuum manipulator.

Robust improvement of the asymmetric post-buckling behavior of a composite panel by perturbing fiber paths

Significant advances in smart material actuators have taken place in the past decade. The holy grail of actuator research is an architecture that can generate high displacement and force throughout a broad frequency range while not consuming a significant amount of electrical power. The large appeal of using smart material actuators stems from their high mechanical energy density. However, all smart material actuators generally have at least one shortcoming involving either mechanical stroke, force, or frequency capability. Whenever speed is a consideration, piezoelectric actuation is the most commonly employed. The purpose of this paper is to review the most current trends in piezoelectric actuation architectures. The paper does not present the theoretical details of each actuator, but instead strives to highlight the novel concepts used in each design to overcome the stroke limitation of the material.

The laryngeal surgery is usually performed with rigid surgical instruments. However, those instruments inevitably cause tissue damage. A novel notch continuum manipulator for laryngeal surgery is proposed. The deformation of the notch continuum manipulator is highly nonlinear. The controller is difficult to construct. The model-based modeling strategy from micro to macro is adopted for forward kinematics. The proposed notch continuum manipulator is modeled as a series of flexible units. Based on the mechanical model and Denavit-Hartenberg method, the mapping from the driven space to the Cartesian space is constructed. The model-free strategy based on the forward kinematics and machine learning is adopted to provide an approximate solution for the inverse kinematics. Therefore, combining the advantages of model-free and model-based strategies, a hybrid method can be proposed to accurately model and solve the kinematics of a class of continuum manipulators. The experimental results obtained through the prototype show that the proposed controller model can meet the actual engineering requirement.

Fatigue failures at fastener holes in structures are undesirable as they can lead to catastrophic mechanical failures. Interference pins create interference fits with joined components to reduce stresses around fastener holes and extend the fatigue life of a structure. In this research, a novel method for finite element (FE) modeling of interference pin connections in a wind turbine lattice tower component was developed. The installation of interference pins was modeled using a two-stage process that causes local stiffness changes in joined members of the component. The local stiffness changes were accounted for in the FE model by using cylinders to represent the interference pins. An experimental setup, including a three-dimensional (3D) scanning laser Doppler vibrometer (SLDV) and a mirror, was used to measure out-of-plane and in-plane natural frequencies and mode shapes of the component. Ten out-of-plane modes and one in-plane mode from the FE model are compared with the experimental results to validate the accuracy of the FE modeling approach. The maximum percent difference between the theoretical and experimental natural frequencies of the component is 3.21%, and the modal assurance criterion (MAC) values between the theoretical and experimental mode shapes are 0.92 or greater, showing good agreement between the theoretical and experimental modal parameters of the component.

A neuro-fuzzy controller method for Smart Material Actuator (SMA) hysteresis modelling is presented, conceived for a morphing wi ng application. The controller correlates each set of forces and electrical currents that are applied to the smart material actuators with the actuator elongation. The actuator is exper imentally tested for four forces, using a variable electrical current. The final controller i s obtained through the Matlab/Simulink integration of three independent neuro-fuzzy contro llers, designed for the increase and decrease of electrical current, and for null electr ical current in the cooling phase of the actuator. This final controller gives a very small error with respect to the experimental values.

Due to the space constraints and obstacles, the traditional industrial manipulator is too difficult to achieve some tasks, such as the gluing for the wing bulkhead of the aircraft and the maintenance for cooling pipes of the nuclear power plant, etc. Continuum manipulator, inspired by the trunk and the tentacle, proves to be very effective for above-mentioned tasks. A novel octopus-like biomimetic robots, is proposed in this paper, which is consisting of continuum joints and discrete joints, and provide a host of benefits, such as the large space of movement, the high flexibility and the heavy load. A novel analytical approach for solving kinematics of the octopus-like arm manipulator with mixed joints is presented in this paper. Based on the bionic mechanism of the continuum manipulator constructed from mixed joints, the robot configuration is established. In this paper, we present a detailed formulation and explanation of a novel kinematic model for the continuum robots with mixed joints. The modeling method based on the Denavit–Hartenberg parameters(also called DH parameters) is used to depict the motion of robot. The robot is comprised of the continuum joint and the rotated joint, so the kinematic model of continuum joint is crucial for constructing that of the whole robot. The continuum joint is equivalent to a section of elastic body, whose D-H parametors can be obtain from the constant-curvature method. Then the forward kinematics of the whole robot can be builded in a D-H frame. Research results will create a new modeling method for the octopus-like continuum manipulators with mixed joints, which can give a new approach for the design on the biomimetic manipulators operating in the unstructured envirement.

This study proposes an innovative algorithm integrating kinematic modeling and intelligent optimization to address the motion planning of multi-segment cable-driven continuum manipulator. Under the piecewise constant curvature (PCC) hypothesis, a forward kinematic framework is formulated to define a structured mapping between joint-space parameters and task-space coordinates. Leveraging the established model, a refined APF strategy is implemented to synthesize collisionavoidance paths for the manipulator, while the Jacobian pseudo-inverse method is applied to obtain corresponding general joint angle solutions. Moreover, to enhance optimization efficiency, the initial population is generated by leveraging the least-squares solution as a baseline, with search boundaries dynamically defined through the null-space properties of the Jacobian pseudoinverse. Then the trajectory optimization is executed under dual constraints of end-effector pose and arm shape via the cheetah optimizer (CO). Numerical simulations validate the algorithm's capability to maintain trajectory tracking accuracy while accounting for end-effector pose, providing an effective solution for motion planning of multi-segment continuum manipulators.

Joined structures are of great industrial relevance. The dynamic effects of joints are, however, often practically difficult to accurately account for in numerical models, as they often lead to local changes in stiffness and damping. This paper discusses the comparison between measurements and simulations of joined panels considering four different joining techniques: adhesive bonding, metal inert gas welding, resistance spot welding and flow drill screwing. An experimental modal analysis is performed on the different systems and the power injection method is applied to determine the loss factors of single plate systems and their joined counterparts. The joined panels are modeled in a holistic simulation environment with particular focus on the joining region, by the application of predefined and generic joint models. A very good agreement is obtained between the simulated dynamic behavior and the experimental results, showing that an accurate representation of the joints has been obtained.

Smart material actuators invariably exhibit hysteresis that may be either symmetric or asymmetric depending upon the actuation principle. Moreover, the shape of hysteresis loop depends on the rate of change of the input. In this study, a generalised rate-dependent Prandtl-Ishlinskii model is proposed to characterise both the symmetric and asymmetric input-output hysteresis effects of smart material-based actuators. The model is realised upon formulation and integration of a generalised rate-dependent play operator. The validity of the generalised model is demonstrated by comparing its displacement responses with the measured symmetric and asymmetric responses obtained for piezoceramic and magnetostrictive actuators under different input frequencies in the 1?200 Hz and 10?100 Hz ranges, respectively. The results suggest that the proposed rate-dependent Prandtl-Ishlinskii model can effectively characterise the symmetric as well asymmetric hysteresis properties of the smart material actuators over a wide range of input frequencies.

This present paper focused on the PUMA 560 robot arm's kinematics problem or the connection between angle in each joint and the end-effectors' position. In this paper the Forward and Inverse Kinematic solution of PUMA Robot is solved by analytical approach. All the values of theta are solved by Denavit-Hartenberg analysis (DH). In other words, it deals with finding the homogeneous transformation matrix that describes the position and orientation of the tool frame with respect to the global reference frame. On the other hand, inverse kinematics is used to calculate the joint angles required to achieve the desired position and orientation. The same transformation matrix which resulted from the forward kinematics in order to describe the position and the orientation of the tool frame relative to the robot base frame is used here in the inverse kinematics to solve for the joint angles.

Nanorobotics have been successfully applied to investigate the physical and biomedical properties in the nano scale. As the center piece of nanorobotcis Scanning probe microscope (SPM) has been widely used to measure the topography information of sample surface as well as serving as a manipulation and sensing tool to modify and measure the mechanical and physical properties of sample. However, the manipulation accuracy of the SPM based nanorobot has been considered as a serious issue because of the hysteresis, creep and thermal drift of its piezoelectric actuator. Generally, creep is linear, which is easy to model; thermal drift is unpredictable, however, it is slow and has an ultimate balance state, thus easy to reduce. Unlike creep characteristic, hysteresis is nonlinear and exists ubiquitously in smart material actuators and seriously affects behaviors of them. Thus cancelation of it will significantly improve motion precision using actuator such as piezoelectric actuators. In this research, we proposed a novel hysteresis modeling and compensation strategy: Polynomial Prandtl-Ishlinskii (PPI) operator superposition model, and its inverse compensator. The property of PPI model is that, it possesses a similar modeling capacity as Preisach model, more important, it can be represented as compressive as the classical PI model. The PPI inverse compensator is then combined with a PID controller, named PPI Inverse Aided PID (PIA-PID) controller, to reduce the output error caused by hysteresis, creep and some unknown drift of our atomic force microscope (AFM) based nanorobot.

This paper presents a smart way to actuate and control the airfoil shape of a morphing wing in the open-loop architecture. The actuation system uses smart material actuators such as shape memory alloys, disposed in two parallel actuation lines, and its control is performed with a Mamdani-type fuzzy logic proportional derivative (PD) controller. The morphing wing project description, its actuation system structure, and the control design and validation are highlighted in this paper. The results obtained by both numerical simulation and experimental validation (bench tests and wind-tunnel tests) are presented as part of the control design and validation. An analysis of the wind flow characteristics, based on the information provided by the pressure sensors mounted on the flexible skin of the morphing wing in the wind-tunnel tests, is included as a supplementary validation; the transition between laminar and turbulent flows is real-time visualized, and the aerodynamic efficiency of the controlled morphing wing is evaluated.

This paper presents a wireless diaphragm actuator and focuses on a lumped parameter grey-box model capable of simulating actuation displacement. Here, modelling aims to provide further insight into this smart material actuator and help facilitate design into new implantable applications. Model parameters were calibrated to a prototype actuator using experimental data and a genetic algorithm optimisation. The model was validated against experimental data and showed a good ability to simulate both static and dynamic diaphragm displacement.