جستجوی مقالات مرتبط با کلیدواژه "continuum robot" در نشریات گروه "مکانیک"

Most of the continuum robots have flexible backbones that are deformed under the internal and external loads and a considerable amount of potential energy may be stored in the backbone. Hence, the continuum robots are exposed to instability issues such as snap-through. The snap-through instability occurs when, with changes in the applied forces, the robot reaches the boundary of its stable region and then moves toward a stable configuration in an uncontrolled manner. Snap-through instability is harmful to the continuum robots and its prediction is important for the design and control of the robot. However, most of the studies focused on design, kinematics, and dynamics of the continuum robots and there are limited studies worked on stability analysis of these robots. In this paper, the stability analysis of the cable-driven continuum robots is investigated. For this, the static equilibrium configurations of the robot are firstly determined under the internal and external loadings. Then, the stiffness matrix of the robot is obtained and the robot stability and snap-through condition are evaluated. The accuracy of the static equations of the robot is verified using the experimental results and the possibility of snap-through occurrence is modeled through simulations. Besides, the effects of the external loads, robot configuration in space, and cross-section of the backbone on the workspace and snap-through occurrence are studied.

The application of continuum robots with flexible mechanical structures is becoming more widespread in the aerospace . These types of robots have recently used to inspect aircraft fuel tanks and space probes. In this paper, the kinematic behavior and working space of a one-segment continuum robot with a tendon mechanism is studied. The theory for kinematic analysis is the fixed curvature method which is the most effective for analyzing continuum robots especially in the case of weightlessness. Also, the amount of tension and bending of the secondary backbones of the continuum robot in the one-dimensional and three-dimensional were investigated as a time dependent functions. Results showed the rate of change of link lengths is about 39.1% increase of back link, and 17.8%, and 21.2% decrease in others with an initial length of 40 mm . Based on this results , it is possible to estimate the amount of tension and bending over a certain period for different types of materials. Additionally, the error of reaching to target point in the obtained optimal values of bending and rotation angles,equal to 67.35 and -40.89, was almost zero which shows the very high accuracy of model. Also, the results of the working spacecover the surface of the sphere of the working space with an accuracy of 1 mm, The obtained results increase accuracy of robot moving in environments with complex structures and limited spaces. The proposed model can be used as a base for continuum multi-part robots.

Origami, as a paper folding art and Japanese culture, has been utilized broadly in engineering areas. The exclusive features of origami such as negative Poisson’s ration, lightweight, deployable and so forth, can be considered in the design of deployable space structures, expandable shelters, drug delivery, and robots. In this study, firstly, the continuum robot with six serial modules of origami parallel structure as its skeleton and the helical springs as the compliant backbone is studied, and constant curvature kinematics was implemented in order to simplify and approximate the kinematic model. Accordingly, the kinematic model of one module was derived. Then, the robot kinematics was obtained as a series of mentioned modules. Furthermore, the proposed continuum robot was modeled by an equivalent mechanism, and a comparison was conducted between the methods to obtain a workspace. Based on the results, the modeling of the equivalent mechanism has an advantage in terms of calculation's volume compared to the constant curvature method and the workspace obtained from both methods was the same. The Jacobian matrix was obtained through the constant curvature approximation methods, which can be considered for singularity analysis in specific conditions and the analysis reveals that the singularities occur when the curve and radius are equal and symmetry is created and the other is when the radius is equivalent to zero. The paper concludes a perspective on several of the themes of current research that are shaping the future of origami-inspired robotics.

In this paper, dynamics and control of a Tendon-based continuum robot is investigated. The curvature is assumed that constant in each section of continuum robot. Kinematic equation is established on the basis of the Euler-Bernoulli beam. The dynamic model of the continuum robot is derived by using Lagrange method. In this paper, robot control is performed in two parts: firstly, Dynamic model is assumed to be known and position and velocity tracking control has been by using the feedback linearization method, But uncertainties in the dynamic model, are constantly challenged the control of continuum robots. For unknown parametric quantities such as mass coefficients, one way is simply substitutes a fixed estimate for the unknown parametric quantities. In this case tracking error is not equal to zero but it’s bounded. For many applications, we cannot assume that tracking error vector is not equal to zero. In such cases we use adaptive controller. In this paper the total mass of the primary backbone and secondary backbone are uncertain parameters, therefore, a new adaptive controller is presented to estimate those uncertainties while cause to asymptotically stable for tracking error. Simulation results show good performance in velocity and position tracking.

In this study, it has been tried to provide a new model for the structure of a backbone arm, to repel the shortcoming in the generation and transmission of the motion for the continuum robots. Backbone arms such as natural structures include continuum backbones with superior properties such as the ability to adapt to the environment. The actuation power is distributed over the robot’s length and makes the shape continuously deformable. In this paper, it has been suggested to add a linkage between the backbones and the branched tendons for power transfer between the drive and backbones. The ratio of the drive torque to backbone torque is introduced as the transfer ratio. The new design is capable to create a variety of transfer ration during a cycle of motion. The state space equations are extracted by Lagrange equations. Dealing the interference of bone-bone and bone-links as geometric constraints are applied to the design and it determines the allowable range of the continuum robot's geometric parameters. This design is examined with planar simulations. To show the effectiveness of the proposed design, several simulation results are illustrated. Optimum geometrical parameters for the constant torque ratio are calculated.In contrast to previous cases with the widely used; the goal is achieved with this novel backbone continuum robot.