Tendon-driven Robotic Mechanisms Research Articles

Kinematic analysis of tendon-driven robotic mechanisms using oriented graphs

In this paper, the kinematic structure of tendon-driven robotic mechanisms is investigated with the aid of oriented graphs. The relation between the graph representation of the kinematic structure and the mechanism is established. It is shown that the kinematic structure of tendon-driven kinematic chains is similar to that of robotic bevel-gear trains, and angular velocity equations of tendon-driven robotic mechanisms can be systematically obtained from the graph representation of the kinematic structure by using the concept of fundamental circuit equations. The theory is demonstrated by the kinematic analysis of two articulated robotic mechanisms.

Kinematic and compliance analysis for tendon-driven robotic mechanisms with flexible tendons

Compliance in tendon transmission may result in position errors for tendon-driven robotic mechanisms. As a consequence, the study of compliance of the mechanism is important for control purpose. This paper deals with the kinematic and force analysis of tendon-driven robotic mechanisms with compliant tendons. The displacement equation of tendon-driven robotic mechanisms that takes tendon compliance into account can be systematically determined from the kinematic structure. The force relations between the joint space and the tendon space are investigated. In particular, the equations relating joint torques, joint angles and tendon displacements are derived. The compliance of the mechanism is thereafter established. Dynamic equations of the system are also analyzed and system’s resonant frequencies are derived through local linearization of the dynamic model. The proposed analysis can be useful for a fast evaluation for the static and dynamic performance of tendon-driven robotic mechanisms.

Force/Position Hybrld Control for Geometrlcally Constrained Tendon-Driven Flexible Joint Arm

The purpose of this study was to design force/position hybrid controllers for a tendon-driven flexible joint arm. Tendon-driven flexible joint arms are expected to be more suitable for force control tasks than the usual motor-driven robot arms because of their weightlessness and their stability for contact. Combining the joint-space orthogonalization method (Liu et al., (1998)) and the tendon-driven robotic mechanism controller (Kobayashi et al., (2003)), we construct two types of controllers, a non-adaptive controller and a neural networks(NN) controller, and show their stability. Simulation shows them to be efficient.

Modeling of the dynamics of tendon-driven robotic mechanisms with flexible tendons

In this paper, a systematic methodology for the dynamic analysis of tendon-driven robotic mechanisms with compliant tendons is presented. The compliance of tendons and inertias of the intermediate links in the mechanism are taken into account. Representing the tendon force by use of a rectifying operator, the unidirectional force transmission characteristic of tendons can be preserved. The dynamic equations can then be systematically established in a recursive manner using the Newton–Euler equations. The joint reaction forces and the tension in each segment of tendon can be also obtained. The methodology can be applied to both endless and open-ended tendon-driven robotic mechanisms.

Adaptive neural network control of tendon-driven mechanisms with elastic tendons

We propose an adaptive control and an adaptive neural network control (composed of two RBF neural components and one adaptive component) for tendon-driven robotic mechanisms with elastic tendons. These controllers can be applied to serial or parallel tendon-driven manipulators having linear or non-linear elastic tendons. We begin by proving the stability of the adaptive control system for our mechanism, and then we prove the stability of the adaptive neural network system and report on the results of numerical simulations and experimental results performed using a 2-DOF tendon-driven mechanism having six elastic tendons.

Dynamic Analysis of Tendon Driven Robotic Mechanisms

AbstractIn this paper, a systematic methodology for the dynamic analysis of tendon‐driven robotic mechanisms is presented. The approach utilizes the recursive Newton‐Euler equations to compute the kinematic and dynamic equations of all links that locate on the transmission line of a tendon‐driven robotic mechanism. The inertias of the intermediate links in the mechanism are taken into account. It is shown that the dynamic equations can be established in a recursive manner from the end‐effector links toward the proximal links and can be solved at the proximal end without the need of solving the simultaneous system equations. The joint reaction forces and the tension in each segment of tendon can be also obtained. The methodology can be applied to both endless and open‐ended tendon drives. © 2003 Wiley Periodicals, Inc.

非線形弾性けんを持つけん駆動ロボット機構の定力制御

Force control of a tendon-driven robotic mechanism is usually done with an active compliance controller, even if the mechanism has passive compliance elements. The controller usually consists of multi feedback loops where the inner loop controls the tension forces of tendons, and the outer one controls the joint angles of the robot. For such a controller, it is assumed that the inner loop converges quickly enough so that we can ignore the dynamics of the inner loop when we design the outer feedback loop. This turns to restrict the bandwidth of the outer loop. Also it means that the stability is not proved strictly.In this paper, we show that a tendon-driven mechanism with nonlinear tendon elasticity should be controlled in the actuator level in order to utilize the performance of the compliant elements efficiently. As one of such controllers, a set-point PD controller is applied to a tendon-driven robotic mechanism to control the contact force with the environment and the Lyapunov stability is investigated. The stability analysis of a tendon-driven manipulator is rather complicated than that of a conventional manipulator or an elastic joint manipulator, because a tendon-driven manipulator has more numbers of tendons than that of the joints and the tendons have nonlinear elasticity. We derive a set of sufficient conditions for the Lyapunov stability and show some numerical simulation results.

けん駆動ロボット機構のけん破断に対する安全度と制御

A tendon-driven robotic mechanism to work with persons co-operatively in the same area is investigated. The mechanism is driven by tendons that are more than the number of degrees of freedom and have non-linear elasticity. It has the advantage of the joint compliance adjustability. This is realized by the tendon redundancy. On the other hand, it has the disadvantage of the breakage of tendons. This makes it difficult to assure the safety of persons working co-operatively with it. But the tendon redundancy also allow us to compensate this disadvantage.This paper describes a method to cope with the tendon breakage for a tendon-driven robotic mechanism. After the basic results for the mechanism are introduced briefly, the degree of safety is defined as the maximum number of tendons allowed to be broken simultaneously without losing the control. Some results are shown with respect to the degree of safety. These are useful to design a tendon-driven robotic mechanism. Next, a method to compensate for the loss of tendon forces of broken tendons with the other tendons is discussed. It allows us safety are broken down simultaneously. Finally, simulation results are given to show the effect of the method.

作業の教示とプログラミング けんに非線形弾性をもつけん駆動システムの制御

The purpose of this paper is to design nonlinear control systems for tendon-driven robotic mechanical systems.Tendon-driven mechanisms are appropriate especially for force-controlled robotic arms as well as robotic hands, because they allow to locate actuators away in the robot bodies and make them small in size and light in weight. In the dynamic aspect of the mechanisms, one of the most important features is the joint stiffness adjustability using the redundancy of actuators and nonlinear elasticity of tendons.A conventional control system for a tendon-driven robotic mechanism is a double looped control system, which consists of an inner loop for tendon force control and an outer loop to generate the desired tendon forces for position and stiffness control. In this control system, the inner loop has to converge to much faster than the outer one does. Thus the inner loop feedback gains become relatively large and the system tends to be vibrative.In this paper, a nonlinear control system that can control the joint angles and the joint stiffness separately is proposed using an exact input-output linearization approach. A necessary and sufficient condition under which we can design such a contoller is given. Classes of tendon-driven robotic mechanisms which satisfy the condition are also investigated. Finally some numerical results will be given to show the efficiency.

The Structural Synthesis of Tendon-Driven Manipulators Having a Pseudotriangular Structure Matrix

Tendons have been widely used for power transmission in the field of anthropomorphic manipulating systems. This article deals with the identification and enumeration of the kine matic structure of tendon-driven robotic mechanisms. The structural isomorphism of tendon-driven manipulators is defined, and the structural characteristics of such mechanical systems are described. Applying these structural characteris tics, a methodology for the enumeration of tendon-driven robotic mechanisms is developed. Mechanism structures with up to six degrees of freedom are enumerated.

Kinematic Analysis of Tendon-Driven Robotic Mechanisms Using Graph Theory

The kinematic structure of tendon-driven robotic mechanisms has been investigated with the aid of graph theory. The correspondence between the graph representation of the kinematic structure and the mechanism has been established. We have shown that the kinematic structure of tendon-driven kinematic chains is similar to that of epicyclic gear trains. We also have shown that, using the concept of fundamental circuits, the displacement equations of tendon-driven robotic mechanisms can be systematically derived from the kinematic structure. The theory has been demonstrated by the kinematic analysis of three articulated robotic devices.