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In this paper, the effect of the slope on the locomotion of a spherical mobile robot named RollRoller is investigated under simulation. We analyze the robot motion up to 30 degrees of the slope inclination. The analysis is conducted for different conditions depending on the torque input and algorithmic motion planning. Oak fiber is chosen as the material of the inclined surface material, and the spherical...
At present, medical experts and researchers turn their attention towards using robotic devices to facilitate human limb rehabilitation. An exoskeleton is such a robotic device, which is used to perform rehabilitation, motion assistance and power augmentation tasks. For effective operation, it is supposed to follow the structure and the motion of the natural human limb. This paper propose a robotic...
The current research trends of object grasping can be summarized as caging grasping and force closure grasping. The motivation of this paper is to combine the advantage of caging grasping and force closure grasping to enable under-actuated grippers like the Lacquey gripper and the parallel grippers like the PR2 gripper to quickly grasp the flat unknown objects. Inspired by the idea that caging grasping...
In rehabilitation, passive control mode is common used at early stages of the post-stroke therapy, when the impaired limb is usually unresponsive. The simplest is the use of a proportional-integral-derivative (PID) feedback control which usually regulates the position or the interaction force along a known reference. Nonetheless PID method cannot achieve an ideal tracking performance due to dynamical...
This paper presents an adaptive sliding mode controller for quadrotor trajectory tracking in presence of uncertainties and disturbances. An exponential reaching law is implemented using the gain adaptation control, which has the advantage of not requiring the knowledge of the upper bound of the lumped uncertainties and external disturbances. Numerical simulation results are provided to illustrate...
In recent researches relating to robotic fingers, a novel power transmission mechanism had been designed, and developed as Twist-drive Actuators or Twisted String Actuator systems (TSA). These actuation structures, state of the art, include compact designs, light-weight mechanical structures, inherent compliance, and variable gearing, resulting in the fabrication of anthropomorphic robotic hands....
This article presents the design, implementation and test of a joint mechanical device created to improve the safety and performance of robots interacting physically with human beings. The mechanism consists of a series of linear springs, preloaded and arranged in such a way to take advantage of the benefits of series elastic actuators and to limit the maximum applicable torque. This is a passive...
Suturing is a challenging and highly dexterous task in minimally invasive surgery, even with the assistance of robotic surgical systems. In this work, we propose a simple yet versatile impedance virtual fixture framework, which can be applied on the master manipulator in a tele-operated robotic surgical system. With this framework, we further develop two types of virtual fixtures that assist with...
A closed elastica, which is an elastic rod whose both ends are fixed to prescribed two places, can be found in various situations in robotics. In this paper, we investigate validity of the discretized spatial model of a closed elastica. The discretized closed elastica model can be regarded as a series of rigid bodies connected with passive elastic joints physically, and represented by a set of nonlinear...
This paper presents the design of a small aerial robot for inhabited microgravity environments, such as orbiting space stations (e.g., ISS). In particular, we target a fleet of robots, called Space CoBots, for collaborative tasks with humans, such as telepresence and cooperative mobile manipulation. The design is modular, comprising an hexrotor based propulsion system, and a stack of modules including...
Series elastic actuators (SEAs) are growingly important in physical human-robot interaction (HRI) due to their inherent safety and compliance. Cable-driven SEAs also allow flexible installation and remote torque transmission, etc. However, there are still challenges for the impedance control of cable-driven SEAs, such as the reduced bandwidth caused by the elastic component, and the performance balance...
Tethered robots often experience entangling of their cables with obstacles in uncertain disaster environments. This paper proposes a spherical tether handling device that unfastens a robot's tether during surveys by releasing the tether and carrying it aside. By using a differential mechanism, the device drives shells and rollers that hold the tether. On flat surfaces, the device moves forward by...
This article presents the design and construction of the torso of a humanoid robot with 22 degrees of freedom (22 GDL) built by additive manufacturing, with the combination of an interactive graphical interface, especially designed for children to self-learn the language in basic sign Ecuador (ESL) through imitation. The interface is designed according to user requirements, should be easy and interactive,...
In control systems, actuators always have (in some degree) physical limitations in their capabilities. In the case of mechanisms (robots included), actuators (typically electrical motors) have also limitations at which can operate successfully and safely without damage, for instance in torque and velocity. This paper addresses the shaft displacement control (position control) of a torque-driven nonlinear...
In this paper, an ongoing work for verifying the behavior of a twisted string actuator in contact with a sliding surface or guided through a sheath is presented. The twisted string actuation system is particularly suitable for very compact and light-weight robotic devices, like artificial limbs and exoskeletons, since it allows the implementation of powerful tendon-based driving systems, based on...
This paper presents a practical control approach for series elastic actuators(SEAs) to generate the desired torque. Specifically, the controller is applicable to both linear and nonlinear SEAs and it works well even in the presence of unknown payload parameters and external disturbances. Via the analysis and transformation of the SEA dynamics, a lumped disturbance signal is constructed and a form...
We propose a novel variable stiffness joint (VSJ) mechanism that achieves the desired stiffness by using elastic deformation of silicone rubber cushions (SRCs). This mechanism can absorb the forces from multiple direction by the flexibility of SRCs and guarantee high safety. To react adequately against unpredictable collision or to manipulate an unstable object skillfully, a joint should be designed...
Obtaining a dynamic model for the parallel mechanism is always regarded as a challenging process due to high complexity of the dynamic equations especially in presence of friction. In this paper the process of black-box identification of friction and rigid-body dynamics of an overconstrained 3-DOF decouple mechanism is addressed. Since the under study mechanism is an overconstrained parallel mechanism,...
Nowadays, exoskeletons have been gaining popularity due to their potential use in rehabilitation and augmentation. These robots often utilize series elastic actuators to facilitate compliant interaction with the human. Numerous studies have been carried out with the purpose of identification and control of these type of actuators. The goal of this paper is to provide a method for dynamic modeling...
Series elastic actuators (SEAs) are commonly used in rehabilitation devices and biped robots to satisfy constraints in terms of safety, impact tolerance, energy storing, and force controllability. This paper discusses the novel design of a multifunctional elastic actuator (MFEA). Our design has several modes with different compliance functionalities (linear and nonlinear force-deflection profiles)...
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