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This paper presents an underactuated finger mechanism that is able to conduct both self-adaptive grasping and natural motions, such as flexion and extension. The robotic finger is realized with a three degrees-of-freedom mechanism composed of stackable four-bar linkages and contractible slider-cranks having a linear spring in each mechanism layer. Kinematics and static force analysis are performed...
In the context of post-stroke patients, suffering of hemiparesis of the hand, robot-aided neuro-motor rehabilitation allows for intensive rehabilitation treatments and quantitative evaluation of patients' progresses. This work presents the design and evaluation of a spring actuated finger exoskeleton. In particular, the spring variables and the interaction forces between the assembly and the hand...
Tendon-sheath actuation mechanism has been researched due to its extremely simple and light cable routing structure. However, the slide-based force transmission mechanism causes friction, which disturbs precise force control. To overcome such disadvantage, friction compensation algorithms in tendon-sheath actuation systems have been studied. However, the torque control of double tendon-sheath mechanism...
To realize the shape adaptability and stable grasping for fruit mechanical picking, a design scheme of end-effector with tendon-driving is proposed based on the underactuated principle. The statics analysis of finger and the design rules for improving grasp stability is researched, as well as the main structure parameters of the end-effector are determined. Analysis and calculation results show that...
Body-powered prosthetic terminal devices fall into two main categories: voluntary-closing devices, which require the user to exert a force to maintain a grasp, and voluntary opening devices, which generally utilize springs to close and maintain a force. As a result, voluntary-closing devices often have a locking feature that allows the user to relax and transport objects while maintaining a firm grip...
Pinching is an important capability for mobile robots handling small items or tools. Successful pinching requires force-closure and, in underwater applications, gentle suction flow at the fingertips can dramatically improve the handling of light objects by counteracting the negative effects of water lubrication and enhancing friction. In addition, monitoring the flow gives a measure of suction-engagement...
The ability to carry large payloads could greatly increase the applications of small, low cost climbing robots. We present a linear inchworm gait that uses a single powerful actuator to climb. To make this gait possible, we leveraged two new methods of achieving controllable, anisotropic adhesion (one method produces over 200 times stronger adhesion in the preferred direction). With controllable,...
As the number of rocket bodies and other debris in Earth's orbit increases, the need to capture and remove this space junk becomes essential to protect new satellites. A low cost solution may include gecko-inspired directional adhesives, which require almost no compressive preload to generate adhesion and are therefore suitable for surface grasping in space where objects are free floating. Current...
This paper details an autonomous perching and take-off method for a quadrotor micro air vehicle (MAV) using a novel dry adhesive gripper on smooth vertical walls. The gripper mechanism uses three directional dry adhesive pads in a triangular configuration. Each pad is equipped with a force sensor that can detect the pad's loading condition. A servo motor is used to actuate the attachment and detachment...
This paper designs a new underactuated robotic finger using a special transmission mechanism. The transmission mechanism consists of a set of gears and a spring to produce connected motions and adaptive curling when the finger moves in free space and when it contacts with the environment, respectively. The connected motion is realized by kinematic constraints of the joints instead of the static equilibrium...
Fingertip suction is investigated using a compliant, underactuated, tendon-driven hand designed for underwater mobile manipulation. Tendon routing and joint stiffnesses are designed to provide ease of closure while maintaining finger rigidity, allowing the hand to pinch small objects, as well as secure large objects, without diminishing strength. While the hand is designed to grasp a range of objects,...
This paper presents a new, detailed dynamics model of a novel type of actuators based on tendons with integrated springs that allows for offline adjustment of the stiffness characteristics. Like other cable or belt actuators, the elastic tendon actuator allows to radically reduce the link inertia by placing the motors near the robot base. But by additionally integrating springs in the tendons, the...
The demands of mobile manipulation are leading to a new class of multi-fingered hands with a premium on being lightweight and robust as well as being able to grasp and perform basic manipulations with a wide range of objects. A promising approach to addressing these goals is to use compliant, underactuated hands with selectively lockable degrees of freedom. This paper presents the design of one such...
Haptic feedback should integrate kinaesthetic and tactile feedback. However current haptic displays do not satisfy the stringent performance and design requirements for integration in teleoperation and VR. This work presents the development of a compact, high performance tactile display for the fingertip. The compact design, high performance, reliability, and simple connectivity of this display make...
Muscular actions in the biological world are associated with stiffness/impedance variation in a wide range depending upon the need of the task. Again, in artificial world variable-stiffness-actuation finds applications in areas like legged machines, artificial prostheses, vibration control, automotive suspension, and compliant robots etc. Nonlinear elasticity of transmission is indispensable in any...
Safety and general versatility are necessary for robots to perform various tasks in human living area. There are tendon based manipulators with nonlinear springs as a manipulator for the requirement. In this paper, we propose simple tension distribution method utilizing an advantage of biological extremity structure for tendon mechanisms to overcome weaknesses of a conventional method using pseudo...
Versatility and safety are required for manipulators used in human environments. Tendon mechanisms with nonlinear springs that can mechanically adjust joint stiffness is one candidate for the requirement. This paper proposes a stiffness ellipse control method of both mechanical and control stiffness at tip of the manipulator called hybrid stiffness control. A conventional controller for the manipulator...
A robotic tendon is modeled and the stiffness of the spring is tuned so that the spring power reduces the peak motor power and energy required for ankle gait. When determining stiffness from gait literature, it is usually assumed that one side of the spring is fixed. We assume that the spring is translating to derive a second method to calculate stiffness. By choosing a tuned spring based on a “dynamic...
This paper presents the first prototype of pneumatically-driven forceps manipulator using a simple flexible joint with intrinsic force sensing. A high performance spring component with wire actuation is employed for two-degree of freedom (DOF) bending joint, and two-DOF tendon drive system is implemented by four pneumatic cylinders. Using a continuum model for the kinematics, a PD controller with...
In robotic hands design tendon driven systems have been considered for years. The main advantage is a small end effector inertia e.g. a light, small hand with high dynamics due to remote actuators. To protect the actuators from impact in unknown environments a compliant mechanism can be used. It absorbs energy during an impact or saves energy to enhance the joint dynamics. In this paper an antagonistic...
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