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The drive mechanism of many robot joints are composed of an electrical actuator and a gear transmission. Besides actuator dynamics and gear elasticity, friction effects are of particular importance for accurate dynamic modeling. This paper presents the design and development of a modular testbed for experimental friction identification in modular robot drives. We have used this testbed to investigate...
In this study, we experimentally investigated the effect of robot fingertip stiffness on friction during grasping of an object. To make robots more human-friendly, robotic hands with soft surfaces have been developed. A soft fingertip, i.e., one with low stiffness, is considered desirable because it produces high friction. However, in our experiments, we were able to obtain high friction from a stiff...
This paper discusses tendon friction effects regarding guiding and material selection. In order to extract valuable information for designers of tendon driven systems, several experiments are conducted to investigate e. g. the intrinsic friction or sliding effect. The results are used to build an experimental friction model and to derive a set of guidelines. The mechanical designer can use the proposed...
Flexible actuator is a kind of actuator which consists of linear motor and thrust wire. Its characteristic is to transmit the force from tip to tip. Therefore, it is possible to design light weight robot without considering the location of actuator. Thanks to this advantage, it is useful for many kinds of robot - teleoperational robot, finger robot, and so on. However, force transmission ability of...
Wearable robots pose high risks to humans because they are directly mounted on human bodies, and methods for assessing their safety have not yet been established. For developing such safety tests, we have fabricated dummy legs that emulate the structure of the human body. Furthermore, all mechanical characteristics of human tissues that relate to their interactions with a wearable robot — elasticity,...
Grasping has always been a hot topic in multidisciplinary field-anatomy, neuroscience and robotics. Recent research on robotic hand grasping has concentrated on introducing the grasp mechanism and characteristics of human hand to robotic hand. This paper analyzes the problem of generating grasp configurations for given objects. A one-step grasp synthesis is applied to a 20DoF five-finger anthropomorphic...
The flexible endoscope has great potential to reach a diseased organ through a natural opening of the human body to perform surgeries without leaving a scar on the body surface. Despite such advances in reaching the diseased organ, using the conventional flexible endoscope to complete surgical procedure is still largely constrained by the limited degree-of-freedoms (DOFs) of endoscopic instruments...
The inverse dynamics model of robots is often the key for accurate control. Especially in the computed torque control, the nonlinearity and the friction can be compensated, leading to better performance. The inverse models, however, is not trivial. The traditional Euler-Lagrange model based on the rigid body assumption often underfits in the presence of frictions and requires tedious derivations;...
This paper presents a multi-fingered hand and a control system intended for research in dexterous manipulation. The hand is based on an anthropomorphic configuration with five identical fingers. The dynamics of the hand-object system is established. A control scheme to ensure firm grip, avoid slippage and well track a given motion imposed to the object is designed. To verify the reasonableness of...
In this paper, the relationship of the movement of stick-slip driving and the step time was studied. Firstly, the research status and the principle of stick-slip driving was introduced. Secondly, the math model of the every step displacement and velocity of stick-slip driving was built. By using mathematical models, the relationship curve of the every step displacement and the step time was received...
This paper presents a method to estimate external forces exerted on a manipulator during motion, avoiding the use of a sensor. The method is based on task-oriented dynamics model learning and a robust disturbance state observer. The combination of both leads to an efficient torque observer that can be incorporated to any control scheme. The use of a learning-based approach avoids the need of analytical...
In this paper we propose a soil penetration robotic system inspired by low friction penetration strategies in plant roots. Growth of cells at the root tip deforms soil, while sloughing cells in the cap create an interface between root and soil to reduce root-soil friction during penetration. A simple prototype, inspired by these root features and based on a tubular shaft and a soft continuum skin,...
In this paper we present a decision theoretic planner for the problem of Navigation Among Movable Obstacles (NAMO) operating under conditions faced by real robotic systems. While planners for the NAMO domain exist, they typically assume a deterministic environment or rely on discretization of the configuration and action spaces, preventing their use in practice. In contrast, we propose a planner that...
This paper presents a tool aimed at the design of compliant, under-actuated hands. The particular motivation is hands that will be used for an underwater robot to grasp a variety of objects, some of which may be delicate or slippery. The focus of the analysis is the problem of object acquisition. In comparison to many prior grasp analysis tools, the tool presented here models the dynamics of a hand,...
Graspless manipulation is easily interfered by external disturbances because the manipulated object is not completely held by a robot hand and supported by an environment such as a floor. Thus it is important to ensure the manipulation is executed robustly against some disturbances. In our works, a rigid-body-based analysis of indeterminate contact forces for quasi-static graspless manipulation has...
In a previous investigation, the minimum energy and power requirements for earthworm locomotion over flexible surfaces were analyzed. The optimum conditions of locomotion were obtained as a function of the number of cells, friction coefficients, stroke length, energy recovery factor, and tangential compliance. In this paper we focus on the energy requirements of inchworms which, unlike earthworms,...
This paper presents a direct adaptive RIT2FNN-based control for motion control of a ball robot with a four-motor inverse mouse-ball driving mechanism actuated by four independent brushless motors simultaneously. A dynamic model of the robot with viscous and Coulomb frictions is derived using Lagrangian mechanics. With the model, a direct adaptive RIT2FNN-based control with the backstepping slidingmode...
This paper considers energy saving of industrial machines using a simple S-curve motion trajectory, which consists of acceleration period, constant velocity period and deceleration period. The S-curve motion trajectory is widely used in industrial applications. We consider a typical dynamics of feed drive systems including inertia term, viscous friction term, Coulomb friction term and the back-EMF...
This paper introduces a novel grasp planning algorithm which can find feasible grasps within a few milliseconds. The object surface is decomposed into plenar regions, which will be decomposed into smaller ones until a discrete grasp can be determined. We have extended the grasp wrench space formulation for the grasp regions and use ray-shooting method to evaluate the force-closure property of the...
This paper proposes a multi-model based approach that estimates joint position and collision detection of a lightweight electric actuator dedicated to manipulation tasks. Taking advantage of an optimized back-drivable mechatronic design, the use of proprioceptive measures at the motor level enables the estimation of the unmeasured terminal position of the mechanical motor-to-joint transmission and...
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