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The combination of tendon driven robotic fingers and variable impedance actuation in the DLR hand arm system brings benefits in robustness and dynamics by enabling energy storage. Since the force measurement and motors are in the forearm the tendon path should have low friction for accurate movements and precise finger control. In this paper an enhanced generation of the Awiwi hand finger design is...
Compliant manipulation has become central to robots that are sought to safely act in and interact with unstructured as well as only partially known environments. In this paper we equip the hydraulically actuated, usually position controlled arms of the Atlas robot with model-based joint impedance control, including suitable damping design, and experimentally verify the proposed algorithm. Our approach,...
Humanoid robots propel themselves and perform tasks by interacting with their environment through contact forces. Typically, nonuniqueness of these forces is dealt with by distributing them evenly between the contacts. In the present paper, we introduce strict prioritization in contact force distribution, to reflect situations when an application of certain contact forces should be avoided as much...
This paper describes a friction model that enables the simulation of mechanical motion with planar two-dimensional friction. Most existing friction models for control applications are applicable to one-dimensional motion only. The proposed model is derived by extending the conventional friction model, the Dahl model. This is achieved by replacing the scalar quantities in the Dahl model with vector...
This paper presents design and analysis of a cabledriven mechanism for a spherical laparoscopy surgical robot manufactured at the Research Center for Science and Technology in Medicine. The design is featured by two types of ‘idler pulleys’, which allow change of cables’ plane of motion in spherical workspace. This robot suffers from back-lash and high friction due to the usage of motor and gear-box...
This article presents a driving algorithm for a four-wheeled independent driving vehicle based on reconfiguration control when a fault occurs. The objective of reconfiguration control is to maintain the same closed-loop characteristic even after actuator failure. Two simulations are conducted: one is for the state following when desired state is given and the other is to track the desired path using...
In this paper, a roller-cam clutch (RCC) mechanism was developed. The RCC can transfer bidirectional torque with high backdrivability, as well as increase actuation energy efficiency, in electrical exoskeleton robots. The developed mechanism was installed at the knee joint, which uses less metabolic energy, and unclutched during the swing phase, thereby functioning as a passive joint. The RCC aimed...
This paper presents a novel spherical rolling robot and the design procedure of an adaptive sliding mode controller for the proposed robot. Towards containing the uncertainties, the sliding mode controller is utilized and simulation tests represent the effectiveness of this method. However, the chattering phenomenon in the robot operation is the main insufficiency of this controller. Hence, in order...
Tendon driven mechanism has been widely used in mechanical systems because of its versatility to mechanical systems requiring complex transmission. This paper proposes a control strategy of slack enabling tendon actuator using feedback linearization. The slack enabling actuator is a newly developed tendon actuator that does not fail although the tendon slacks (non-positive tension) at the outlet of...
This paper presents a systematic approach for experimental identification and assessment of mechanical effects on the dynamics of elastic actuators. The variable torsion stiffness (VTS) actuator is used as an example. As a basis for parameter identification, a flexible joint robot model considering friction and damping is used. To identify and assess occurring effects, a component-wise experimental...
This paper presents a general grasp synthesis algorithm. The algorithm follows a stochastic approach that calculate a large number of grasps with good quality in short amount of time. It takes as an input a 3D point cloud that represents the contact points of the object and heuristically selects concurrent points which are covered by contact points and identifies concurrent grasps from such contact...
A collective actuator is a self-reconfigurable modular-robotic structure which produces useful mechanical work through simultaneous reconfiguration of its constituent units. An actuator is additionally called scalable if its force-to-weight ratio does not depend on the number of its member modules. In this work, we consider scalable collective actuators built from spherical catoms with two connection...
This paper explores the manipulation of a grasped object by pushing it against its environment. Relying on precise arm motions and detailed models of frictional contact, prehensile pushing enables dexterous manipulation with simple manipulators, such as those currently available in industrial settings, and those likely affordable by service and field robots.
Ball-balancing robots (BBRs) are endowed with rich dynamics. When properly designed and stabilized via feedback to eliminate jitter, and intuitively coordinated with a well-designed smartphone interface, BBRs exhibit a uniquely fluid and organic motion. Unlike mobile inverted pendulums (MIPs, akin to unmanned Segways), BBRs stabilize both fore/aft and left/right motions with feedback, and bank when...
Whole-body holding manipulation is effective for carrying the handleless large object. In order to keep the object stability, the dexterous transition motion is necessary. From geometric and physical conditions of object manipulation, we propose the general method of generating the transition graph, which represents the object pose and grasp contact. By searching the path on the graph, the transition...
This paper proposes a novel tree-climbing robot called O-M-Climber, which is driven by only one motor. The climbing principle imitates the bionic climbing approach. Main features include a two-shaft linkage mechanism connected with several cam-slider devices to perform alternating movement of the claws. The claws maintain the robot on the tree, imitating the structure of climbing irons. This novel...
The study mainly concerns a novel blister generation method for the establishment of a safety verification test. This test system focuses on the skin friction trauma, which has been found in the operators of physical assistant robots due to their misuses or overlong operating, and can even deteriorate into serious dermatopathya without preventing and prompt treatment. In the present study, first,...
A robust tracking control problem is considered for an unknown Euler-Lagrange system to track a desired time-varying trajectory. Unknown dynamics including friction effects and impact forces from the environment are considered in the paper. It is challenging to model these two types of uncertain forces for Euler-Lagrange Systems such as robot manipulators and motors. A robust controller with adaptive...
High-gain proportional-integral-derivative (PID) position control can achieve stiff position control but it involves the risk of overshoots in some cases such as discontinuous position commands and disturbances. This paper presents a new position controller that achieves accurate trajectory tracking and overdamped resuming motion from large positional errors and disturbances. The proposed controller...
Underactuated robotic hands based on postural synergy with passive joint compliance have shown promising performance in robust grasping. However it is still lack of universal theoretical analysis for this type of robotic hand. In this paper we start from the previous model and analysis method, modifying the fundamental model by introducing the contact and friction constraints in grasping. A simulation...
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