Design of Lead Screw Actuators for Wearable Robotic Applications

2005 ◽  
Author(s):  
Kevin W. Hollander ◽  
Thomas G. Sugar
Keyword(s):  
High Weight ◽  
Weight Ratio ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Human Muscle ◽  
Wearable Robot ◽  
Screw Design ◽  
Lead Screw ◽  
Standard Lead ◽  
Robotic Applications

A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight and most importantly safe. To achieve these goals an actuator with a good ‘power to weight’ ratio, good mechanical efficiency, good ‘strength to weight’ ratio and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and high weight. However, using the design procedure outlined in this text both efficiency and weight are improved, thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a ‘power to weight’ ratio of 277W/kg, approaching that of the DC motor driving it, at 312W/kg, as well as a mechanical efficiency of 0.74, and a maximum ‘strength to weight’ ratio of 11.3kN/kg(1154kgf/kg).

Design of Lightweight Lead Screw Actuators for Wearable Robotic Applications

2005 ◽  
Vol 128 (3) ◽  
pp. 644-648 ◽  
Author(s):  
Kevin W. Hollander ◽  
Thomas G. Sugar
Keyword(s):  
Direct Contact ◽  
Weight Ratio ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Human Muscle ◽  
Wearable Robot ◽  
Screw Design ◽  
Lead Screw ◽  
Standard Lead ◽  
Robotic Applications

A wearable robot is a controlled and actuated device that is in direct contact with its user. As such, the implied requirements of this device are that it must be portable, lightweight, and most importantly safe. To achieve these goals, an actuator with a good “power to weight” ratio, good mechanical efficiency, good “strength to weight” ratio, and that is safe is desired. The design of the standard lead screw does not normally perform well in any of these categories. The typical lead screw has low pitch angles and large radii, thereby yielding low mechanical efficiencies and heavy weight. However, using the design procedure outlined in this text, both efficiency and weight are improved; thus yielding a lead screw system with performances that rival human muscle. The result of an example problem reveals a feasible lead screw design that has a power to weight ratio of 277W∕kg, approaching that of the dc motor driving it, at 312W∕kg, as well as a mechanical efficiency of 0.74, and a maximum strength to weight ratio of 11.3kN∕kg(1154kgf∕kg).

scholarly journals Research on the Mechanical Efficiency of High-Speed 2D Piston Pumps

Processes ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 853 ◽  
Author(s):  
Yu Huang ◽  
Jian Ruan ◽  
Chenchen Zhang ◽  
Chuan Ding ◽  
Sheng Li
Keyword(s):  
Friction Coefficient ◽  
High Speed ◽  
High Pressures ◽  
Weight Ratio ◽  
Rolling Friction ◽  
Mechanical Efficiency ◽  
Load Pressure ◽  
Axial Piston Pumps ◽  
Series Of Experiments ◽  
Rolling Friction Coefficient

Since many studies on axial piston pumps aim at enhancing their high power-weight ratio, many researchers have focused on the generated mechanical losses by the three friction pairs in such pumps and attempted to diminish them through abundant and new structural designs of the pump’s components. In this paper, a high-speed 2D piston pump is introduced and its architecture is specifically described. Afterward, a mathematical model is established to study the pump’s mechanical efficiency, including the mechanical losses caused by the viscosity and stirring oil. Additionally, in this study the influences of the rotational speed, the different load pressures, and the rolling friction coefficient between the cone roller and the guiding rail are considered and discussed. By building a test rig, a series of experiments were carried out to prove that the mechanical efficiency was accurately predicted by this model at low load pressures. However, there was an increasing difference between the test results and the analytical outcomes at high pressures. Nevertheless, it is still reasonable to conclude that the rolling friction coefficient changes as the load pressure increases, which leads to a major decrease in the mechanical efficiency in experiments.

Characterization and Parametric Study of Multilayered IPMC Actuator

2014 ◽  
Vol 983 ◽  
pp. 161-165
Author(s):  
Muhammad Farid Shaari ◽  
Zahurin Samad
Keyword(s):  
Parametric Study ◽  
Weight Ratio ◽  
Small Scale ◽  
Metal Composite ◽  
Ionic Polymer Metal Composite ◽  
End Effector ◽  
Ionic Polymer ◽  
Actuation Force ◽  
Polymer Metal ◽  
Robotic Applications

Ionic Polymer-Metal Composite (IPMC) has been utilized as an actuator in several robotic applications such as the actuator for its locomotion and gripper of the end effector. However, due to its low actuation force which is normally less than 10gf (depend on dimension), the application has been limited to small scale robot. Hence, in this research we propose a multilayer structure of IPMC actuator and investigate the actuation force increment. Besides, parametric study was also conducted to determine the force-to-weight ratio and the bending displacement. The obtained results had been compared to single ply IPMC actuator at the same thickness. The result shows that the increment of IPMC layer had increased the actuating force up to 30% for two layers and 40% for three layers. In addition, utilizing multilayered IPMC had reduced the stiffness constraint for thicker IPMC. This finding would be useful in designing stage of a small scale robot that require higher actuation force at a higher bending displacement.

scholarly journals Developing a Novel Miniature 3D-Printed TLBS with High Mechanical Efficiency and Better Controllability

Micromachines ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 662
Author(s):  
Chung-Wei Lee ◽  
Jung-Hua Chou
Keyword(s):  
Mechanical Efficiency ◽  
Ball Screw ◽  
Maximum Efficiency ◽  
Design Parameters ◽  
Affecting Factors ◽  
Lead Screw ◽  
Torque Loss ◽  
3D Printed ◽  
Novel Model ◽  
Better Than

This paper focuses on the development of a 3D-printed threadless ball screw (TLBS) for the applications that require miniaturization, customization, and accuracy controllability. To enhance the efficiency of the TLBS, a novel model of the TLBS for analyzing the mechanical efficiency is presented to obtain the key affecting factors. From these factors, the design parameters for fabrication are determined. For miniaturization, a novel 3D-printed one-piece preloaded structure of light weight of 0.9 g is implemented as the TLBS nut part. Experimental results show that the measured mechanical efficiency of TLBS is close to that predicted by the theoretical model with a normalized root mean square error of 3.16%. In addition, the mechanical efficiency of the present TLBS (maximum efficiency close to 90%) is better than that of the lead screw and close to the ball screw. The unique characteristic of the present TLBS is that its total torque loss is a weak function of the load, a phenomenon not observed in either the ball screw or the lead screw. This characteristic is advantageous in enhancing the controllability of accuracy at different loads.

Joint Equivalence Design and Analysis of a Tensegrity Joint

2021 ◽  
pp. 1-12
Author(s):  
Bingxing Chen ◽  
Hongzhou Jiang ◽  
Jingxuan Liu ◽  
Shuaibo Lu
Keyword(s):  
Mechanical Efficiency ◽  
Design Criterion ◽  
Elastic Response ◽  
Rotational Degree ◽  
Robotic Arms ◽  
Large Size ◽  
Compliant Joint ◽  
Deviation Degree ◽  
Rigid Joints ◽  
Robotic Applications

Abstract We propose a method to design a tensegrity joint, making its elastic deformation an accurate joint-like motion, such as a rotation around the designed rotational center. The tensegrity joint can be a three rotational degree-of-freedom (DOF) joint through this method. Axis drift is presented as a design criterion to describe the rotational center's deviation degree concerning the compliance center since the rotational center is not fixed to one point for different positions of the tensegrity joint. The axis drift is designed to be in a prescribed range so that the tensegrity joint is approximately equivalent to a rigid joint. In other words, the tensegrity joint's elastic response under external torque and force becomes precise rigid-joint-like kinematics and can replace rigid joints to transfer motion, force, and energy. A large-size tensegrity joint is developed to verify the joint equivalence experimentally. The experimental results show that the tensegrity joint achieved maximum dimensionless axis drift less than 2%, and indicate an excellent joint equivalence. The tensegrity joints' ability to replace rigid joints as modular joints to construct a hyper redundant serial structure is demonstrated using a tensegrity robotic arm. The proposed tensegrity compliant joint has notable benefits of tensegrity structure such as high mechanical efficiency, modularity, and scalability, and can be extended to many robotic applications, such as large-size serial robotic arms and snake-like robots.

MotoGP 2007: Criteria for Engine Optimization

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Enrico Mattarelli
Keyword(s):  
High Speed ◽  
Fluid Dynamic ◽  
Weight Ratio ◽  
Engine Performance ◽  
Real Data ◽  
Mechanical Efficiency ◽  
Point Of View ◽  
One Dimensional ◽  
Four Cylinders ◽  
Technical Regulations

The paper proposes some design criteria for the MotoGP engines, complying with the FIM 2007 Technical Regulations. Five configurations have been considered: engines with three cylinders in line and four cylinders in line, and three V engines with four, five, and six cylinders. All the analyzed solutions have been optimized from a fluid-dynamic point of view by means of one dimensional engine cycle simulations. Then, the engines are compared in terms of full load performance at steady conditions. Finally, the influence of engine performance, along with operation regularity and motorbike weight, is assessed by means of a lap time simulator, developed by the author on the base of real data. The best configurations turned out to be the four-cylinder engines, while three-cylinder and five-cylinder engines are quite penalizing. The key of the four-cylinder engines success is their good breathing capability and mechanical efficiency at high speed, yielding an optimum power-to-weight ratio, associated with a good engine regularity, i.e., a smooth response to throttle angle variations.

scholarly journals Effect of muscle temperature on rate of oxygen uptake during exercise in humans at different contraction frequencies

2002 ◽  
Vol 205 (7) ◽  
pp. 981-987
Author(s):  
Richard A. Ferguson ◽  
Derek Ball ◽  
Anthony J. Sargeant
Keyword(s):  
Mechanical Efficiency ◽  
Human Muscle ◽  
Hot Water ◽  
Muscle Temperature ◽  
Energy Turnover ◽  
Cycling Exercise ◽  
Contraction Frequency ◽  
Cross Bridge ◽  
Pedalling Rate ◽  
The Right

SUMMARY The effect of elevated human muscle temperature on energy turnover was investigated during cycling exercise (at 85 % of V̇O2max) at a contraction frequency of 60 revs min-1. Muscle temperature was passively elevated prior to exercise by immersion of the legs in a hot water bath (42 °C). During exercise at this low pedalling rate, total energy turnover was higher (P<0.05) when muscle temperature was elevated compared with normal temperature (70.4±3.7 versus 66.9±2.4 kJ min-1, respectively). Estimated net mechanical efficiency was found to be lower when muscle temperature was elevated. A second experiment was conducted in which the effect of elevated human muscle temperature on energy turnover was investigated during cycling exercise (at 85 % of V̇O2max) at a contraction frequency of 120 revs min-1. Under the conditions of a high pedalling frequency, an elevated muscle temperature resulted in a lower energy turnover (P<0.05) compared with the normal muscle temperature (64.9±3.7 versus 69.0±4.7 kJ min-1, respectively). The estimated net mechanical efficiency was therefore higher when muscle temperature was elevated. We propose that, in these experiments, prior heating results in an inappropriately fast rate of cross-bridge cycling when exercising at 60 revs min-1, leading to an increased energy turnover and decreased efficiency. However, at the faster pedalling rate, the effect of heating the muscle shifts the efficiency/velocity relationship to the right so that cross-bridge detachment is more appropriately matched to the contraction velocity and, hence, energy turnover is reduced.

Theoretical and Experimental Analysis of a Cycloidal Speed Reducer

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Carlo Gorla ◽  
Piermaria Davoli ◽  
Francesco Rosa ◽  
Claudio Longoni ◽  
Franco Chiozzi ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Structural Characteristics ◽  
Design Procedure ◽  
Mechanical Efficiency ◽  
Design Parameters ◽  
Ring Gear ◽  
Power Losses ◽  
Transverse Profile ◽  
Speed Reducer ◽  
Simplified Procedure

In this paper, a theoretical and experimental investigation on an innovative cycloidal speed reducer is presented. The typical cycloid drive has a planet wheel, the profile of which is the internal offset of an epitrochoid meshing with cylindrical rollers connected to the case. This reducer, on the contrary, has an external ring gear, the transverse profile of which is the external offset of an epitrochoid and engages with the planet wheel by means of cylindrical rollers. This paper investigates the structural characteristics and the kinematic principles of this type of reducer. A theoretical approach based on the theory of gearing (following Litvin’s approach) is developed and compared to a development of Blanche and Yang’s approach. Furthermore, a simplified procedure to calculate the force distribution on cycloid drive elements, its power losses, and theoretical mechanical efficiency is presented. The effects of design parameters on the values of forces are studied for an optimal design of this type of reducer. The theoretical model is tuned on the basis of the results of tests made on purpose. The mechanical efficiency dependency on speed and torque is described. The main aim of this work is to tune a theoretical model in order to predict the operating behavior of the cycloid drive and to improve its design procedure.

scholarly journals Transmission Comparison for Cooperative Robotic Applications

Actuators ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 203
Author(s):  
Mark J. Nandor ◽  
Maryellen Heebner ◽  
Roger Quinn ◽  
Ronald J. Triolo ◽  
Nathaniel S. Makowski
Keyword(s):  
Muscle Activation ◽  
Mechanical Efficiency ◽  
Assistive Devices ◽  
Joint Torque ◽  
Harmonic Drive ◽  
Electromechanical Actuators ◽  
Passive Resistance ◽  
Isometric Torque ◽  
Planetary Transmission ◽  
Robotic Applications

The development of powered assistive devices that integrate exoskeletal motors and muscle activation for gait restoration benefits from actuators with low backdrive torque. Such an approach enables motors to assist as needed while maximizing the joint torque muscles, contributing to movement, and facilitating ballistic motions instead of overcoming passive dynamics. Two electromechanical actuators were developed to determine the effect of two candidate transmission implementations for an exoskeletal joint. To differentiate the transmission effects, the devices utilized the same motor and similar gearing. One actuator included a commercially available harmonic drive transmission while the other incorporated a custom designed two-stage planetary transmission. Passive resistance and mechanical efficiency were determined based on isometric torque and passive resistance. The planetary-based actuator outperformed the harmonic-based actuator in all tests and would be more suitable for hybrid exoskeletons.

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