scholarly journals Design and Development of a Compact High-Torque Robotic Actuator for Space Mechanisms

2017 ◽  
Vol 9 (6) ◽  
Author(s):  
Elias Brassitos ◽  
Nader Jalili
Keyword(s):  
Gear Ratio ◽  
System Level ◽  
Force Transmission ◽  
Torque Density ◽  
Output Force ◽  
Short Development Time ◽  
Transmission Structure ◽  
Drive Systems ◽  
Two Stages ◽  
Space Mechanisms

Space robots require compact joint drive systems (JDSs), typically comprising of actuator, transmission, joint elements that can deliver high torques through stiff mechanical ports. Today's conventional space drive systems are made from off-the-shelf actuators and multistage transmissions that generally involve three to six stages. This current practice has certain benefits such as short development time due to the availability of mechanical components. However, it lacks a system-level integration that accounts for the actuator structure, size and output force, transmission structure, gear-ratio, and strength, and often leads to long and bulky assemblies with large number of parts. This paper presents a new robotic hardware that integrates the robot's JDS into one compact device that is optimized for its size and maximum torque density. This is done by designing the robotic joint using a special transmission which, when numerically optimized, can produce unlimited gear-ratios using only two stages. The design is computerized to obtain all the solutions that satisfy its kinematic relationships within a given actuator diameter. Compared to existing robotic actuators, the proposed design could lead to shorter assemblies with significantly lower number of parts for the same output torque. The theoretical results demonstrates the potential of an example device, for which a proof-of-concept plastic mockup was fabricated, that could deliver more than 200 N·m of torque in a package as small as a human elbow joint. The proposed technology could have strong technological implications in other industries such as powered prosthetics and rehabilitation equipment.

Design and Prototyping of a Force-Reflecting Hand-Controller for Ultrasound Imaging

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
Farshid Najafi ◽  
Nariman Sepehri
Keyword(s):  
Ultrasound Imaging ◽  
Static Friction ◽  
Parallel Mechanisms ◽  
Detailed Design ◽  
Remote Locations ◽  
Output Force ◽  
And Performance ◽  
Drive Systems ◽  
Robotic Wrist ◽  
Fixed Center

This paper presents detailed design, analysis, prototyping, and testing of a novel force-reflecting hand-controller allowing physicians to control a robotic wrist and perform ultrasound examinations on patients in remote locations. The proposed device is a four degree-of-freedom mechanism with a fixed center-of-motion and uses symmetric parallel mechanisms. All movements of the device are kinematically decoupled, i.e., the hand-controller has independent drive systems for each standard ultrasound motion. A technique has been adapted to statically balance the weight of the device over its entire workspace using a single tension spring. The prototype of the device has been constructed and evaluated for ultrasound imaging of kidney and spleen. Maximum and accuracy of the output force are analytically determined and performance of the device in terms of static balancing, static-friction break-away force, and maximum achievable impedances are experimentally evaluated.

scholarly journals Modeling, Testing, and Characteristic Analysis of a Planetary Flywheel Inerter

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Zheng Ge ◽  
Weirui Wang
Keyword(s):  
Theoretical Analysis ◽  
Planetary Gear ◽  
Gear Ratio ◽  
Ball Screw ◽  
Ring Gear ◽  
Characteristic Analysis ◽  
Planetary Gears ◽  
Nonlinear Dynamical ◽  
Output Force ◽  
New Type

We propose the planetary flywheel inerter, which is a new type of ball screw inerter. A planetary flywheel consists of several planetary gears mounted on a flywheel bracket. When the flywheel bracket is driven by a screw and rotating, each planetary gear meshing with an outer ring gear generates a compound motion composed of revolution and rotation. Theoretical analysis shows that the output force of the planetary flywheel inerter is proportional to the relative acceleration of one terminal of the inerter to the other. Optimizing the gear ratio of the planetary gears to the ring gear allows the planetary flywheel to be lighter than its traditional counterpart, without any loss on the inertance. According to the structure of the planetary flywheel inerter, nonlinear factors of the inerter are analyzed, and a nonlinear dynamical model of the inerter is established. Then the parameters in the model are identified and the accuracy of the model is validated by experiment. Theoretical analysis and experimental data show that the dynamical characteristics of a planetary flywheel inerter and those of a traditional flywheel inerter are basically the same. It is concluded that a planetary flywheel can completely replace a traditional flywheel, making the inerter lighter.

Complete Balancing of Space Mechanisms—Shaking Force Balancing

1983 ◽  
Vol 105 (4) ◽  
pp. 609-616 ◽  
Author(s):  
C. Bagci
Keyword(s):  
Mechanism Design ◽  
Total Mass ◽  
Force Transmission ◽  
The Subject ◽  
Gear Rack ◽  
Space Mechanisms

Complete balancing of shaking forces and shaking moments in space mechanisms is the subject of this article. Using real vectors, it presents methods of balancing shaking forces completely in space mechanisms. Force balancing of a mechanism is achieved by attaining a stationary center of the total mass of the mechanism. Design equations for force balancing of the RSSR, RSSP slider-crank and RSRC, CSC, and RCRC screw generators are developed. These mechanisms, their pair inversion mechanisms are force balanced thus establishing general guidelines for force balancing of space mechanisms. It is shown that SC and SRC dyads in space mechanisms also introduce force transmission irregularity in addition to the CRC, CCC, CRP, PRP, PSP, PSC dyads that introduce force transmission irregularity. Space mechanisms with force transmission irregularities are balanced by attaching a force balancing RRR dyad or a linearly moving conterbalancer driven by gear-rack drive, a belt, chain, or rolomite mechanism.

Theory of Isotropic Transmission for Tendon-Driven Manipulators

1994 ◽  
Author(s):  
Yeong-Jeong Ou ◽  
Lung-Wen Tsai
Keyword(s):  
General Theory ◽  
Power Transmission ◽  
Degree Of Freedom ◽  
Mechanical Power ◽  
Force Distribution ◽  
Static Force ◽  
Force Transmission ◽  
Transmission Characteristics ◽  
End Effector ◽  
Transmission Structure

Abstract This paper deals with the synthesis of the mechanical power transmission structure in tendon-driven manipulators. Based on the analysis of static force transmission from the actuator space to the end-effector space, a general theory is developed for the synthesis of tendon-driven manipulators with isotropic transmission characteristics. It is shown that an n-dof (degree of freedom) manipulator can possess these characteristics if it is made up of n+1 or 2n tendons and if its link lengths and pulley sizes are designed according to two equations of constraint. Two examples are used to demonstrate the theory. It is also shown that manipulators with an isotropic transmission structure do have more uniform force distribution among their tendons.

Design and Optimization of a Five-Finger Haptic Glove Mechanism

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Zhou Ma ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Force Feedback ◽  
Maximum Output ◽  
Force Transmission ◽  
Force Output ◽  
Link Length ◽  
Design And Optimization ◽  
Natural Motion ◽  
Bare Hand ◽  
Output Force ◽  
Future Potential

This paper describes the design and optimization of a novel five-finger haptic glove mechanism, which uses a worm-geared motor and an antagonistically routed cable mechanism at each finger as both active and passive force display actuators. Existing haptic gloves either restrict the natural motion and maximum output force of the hand or are bulky and heavy. In order to tackle these challenges, the five-finger haptic glove is designed to minimize the size and weight and maximize the workspace and force output range of the glove. The glove is a wireless and self-contained mechatronic system that mounts over the dorsum of a bare hand and provides haptic force feedback to each finger. This paper describes the mechatronic design of the glove and the method to optimize the link length with the purpose of enhancing workspace and the force transmission ratio. Simulation and experimental results are reported, showing the future potential of the proposed system in haptic applications and rehabilitation therapy.

Identifying Stiffness, Friction, and Kinematic Error Signature in Gear Bearing Drive Transmissions

2018 ◽  
Author(s):  
Elias Brassitos ◽  
Nader Jalili
Keyword(s):  
Gear Ratio ◽  
Open Loop ◽  
Reduction Gear ◽  
Kinematic Error ◽  
High Reduction ◽  
Stiffness Characteristics ◽  
Drive Systems ◽  
Ratio Transmission ◽  
Speed Response

The Gear Bearing Drive (GBD) is a recently developed high gear-ratio transmission concept based on NASA’s high-reduction gear bearing technology and brushless outrunner motor technology. In this paper, we describe the experimental setup and characterization of the GBD transmission’s stiffness, friction, backlash, hysteresis as well as its kinematic error. Compared to conventional precision drive systems such as harmonic drives, the GBD can offer similar advantages such as high gear-ratio in a compact assembly but with the potential of better stiffness characteristics and a more predictable output speed response. The models derived in this paper were then fed into a dynamic model that can accurately simulate the velocity open-loop response of the transmission under various input current functions.

Dynamic Force and Torque Analysis of Mechanisms Using Dual Vectors and 3 × 3 Screw Matrix

1972 ◽  
Vol 94 (2) ◽  
pp. 738-745 ◽  
Author(s):  
Cemil Bagci
Keyword(s):  
Rate Of Change ◽  
Inertia Force ◽  
Dynamic Force ◽  
Equilibrium Equations ◽  
Force Vector ◽  
Time Rate ◽  
Output Force ◽  
Dynamic Analyses ◽  
Torque Analysis ◽  
Space Mechanisms

The method of determining dynamic force and torque distributions in mechanisms by using dual vectors and 3 × 3 screw matrix is presented. The dual equilibrium equations for each moving link of a mechanism are written as a null resultant dual force vector in a reference system located on the link. The resulting 6 × (n – 1) equilibrium equations for an n-link mechanism are solved for the unknown force and torque components at the pair locations, and for the input force or torque required to drive the mechanism to produce the specified dual output force. The dynamics of the mechanism is governed by introducing the dual inertia force acting on a link, which is determined as the negative of the time rate of change in the dual momentum of the link due to its own mass and mass moments of inertia, in the dual equilibrium equation for that link. Dynamic analyses of the 4R plane and the RCCC space mechanisms are performed. Dynamic transmissivities are defined. The RCCC mechanism is analyzed in a numerical example and the results of the dynamic distributions are compared with those of static distributions.

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