Contact Stress Reduction Mechanisms for the CAM-Based Infinitely Variable Transmission

2007 ◽  
Author(s):  
Derek F. Lahr ◽  
Dennis W. Hong
Keyword(s):  
Contact Stress ◽  
Stress Reduction ◽  
Kinematic Model ◽  
Three Dimensional ◽  
Speed Ratio ◽  
Cam Mechanism ◽  
Expected Performance ◽  
Differential Mechanism ◽  
Variable Transmission ◽  
Infinitely Variable Transmission

The Cam-based Infinitely Variable Transmission (IVT) is a new type of ratcheting IVT based on a three dimensional cam and follower system which provides unique characteristics such as generating specific functional speed ratio outputs including dwells, for a constant velocity input. This paper presents several mechanisms and design approaches used to improve the torque and speed capacity of this unique transmission. A compact, lightweight, and capable differential mechanism based on a cord and pulley system is developed to double the number of followers in contact with the cam at any time, thereby reducing the contact stress between the followers and the cam surface considerably. A kinematic model governing the motion of this differential is developed and a few experimental results from the prototype are presented, showing an overall increase in performance including a smooth output, a wide gear range, and the ability to shift under load. Plans for future improvements to the design, including an inverted external cam mechanism, is also presented along with the expected performance gains.

Dynamic Analysis of a Novel Geared Infinitely Variable Transmission

2014 ◽  
Author(s):  
Z. R. Li ◽  
X. F. Wang ◽  
W. D. Zhu
Keyword(s):  
Dynamic Analysis ◽  
Wind Turbine ◽  
Speed Ratio ◽  
Lagrangian Dynamics ◽  
Input And Output ◽  
Newtonian Dynamics ◽  
Continuous Output ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Crank Length

A novel geared infinitely variable transmission (IVT) that can generate a continuous output-to-input speed ratio from zero to a certain value is studied for vehicle and wind turbine applications. The principle of changing the output-to-input speed ratio is to use a crank-slider mechanism; the output-to-input speed ratio is controlled by adjusting the crank length. Since the crank-slider mechanism can lead to relatively large variation of the output-to-input speed ratio in one rotation of the crank, the instantaneous input and output speeds and accelerations have variations and the corresponding forces exerted on each part of the IVT can have obvious changes in one rotation of the crank. Since forces on some parts of the IVT are critical and can cause failure of the IVT, a dynamic analysis of the IVT is necessary to simulate the input and output speeds and accelerations. A method that combines Lagrangian dynamics and Newtonian dynamics is developed in this work to analyze the motion of the IVT. The dynamic analysis results can be used to evaluate the design of the IVT.

Effect of post-cam design on the kinematics and contact stress of posterior-stabilized total knee arthroplasty

2021 ◽  
pp. 1-10
Author(s):  
Jin-Ah Lee ◽  
Yong-Gon Koh ◽  
Kyoung-Tak Kang
Keyword(s):  
Finite Element ◽  
Total Knee Arthroplasty ◽  
Contact Stress ◽  
Knee Arthroplasty ◽  
Gait Cycle ◽  
Three Dimensional ◽  
Posterior Stabilized ◽  
Cam Mechanism ◽  
Total Knee ◽  
Tibial Translation

BACKGROUND: The post-cam mechanism in the posterior-stabilized (PS) implant plays an important role, such as durability and kinematic performances, in total knee arthroplasty (TKA). OBJECTIVE: The purpose of this study was to evaluate the difference in the kinematics and contact stress of five post-cam designs, which are flat-and-flat, curve-and-curve (concave), curve-and-curve (concave and convex), helical, and asymmetrical post-cam designs, using three-dimensional finite element models. METHODS: We designed the post-cam model with five different geometries. The kinematics, contact stress, and contact area were evaluated in the five post-cam designs under gait cycle loading conditions using the finite element method. RESULTS: There were no differences in the contact stress and area on the tibial insert in all designs. The largest internal rotation was shown in the swing phase for the helical design, and the largest tibial posterior translation was observed for the curve-and-curve (concave) design. The curve-and-curve (concave) design showed the lowest contact stress and the largest posterior tibial translation during the gait cycle. CONCLUSIONS: Considering the kinematics and contact stress, we found that the curve-and-curve (concave) design was more stable than other designs. From the results, we found the important factors of TKA implant considering stability and kinematics.

Self-Powered Flywheel-Infinitely Variable Transmission Actuator for Artificial Knee Joints

2017 ◽  
Vol 11 (3) ◽  
pp. 361-367
Author(s):  
Roberta Aló ◽  
◽  
Francesco Bottiglione ◽  
Giacomo Mantriota
Keyword(s):  
Knee Joint ◽  
Knee Joints ◽  
Total Power ◽  
Speed Ratio ◽  
Power Requirement ◽  
Human Knee ◽  
Wearable Robots ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Self Powered

The efficient energetics of human walking could possibly be used to fulfill the total power requirement of human knee, without requiring any additional sources of energy. This study intends to addresses this issue by examining the idea of a novel self-powered actuator for artificial knee joints of wearable robots. The self-powered Flywheel-Infinitely Variable Transmission (F-IVT) is an actuator whose only source of power is a flywheel that stores and delivers energy from and to the knee joint by changing the speed ratio of the IVT according to the phase of the gait cycle. This study evaluates the efficacy of this novel actuator by estimating the amount of energy it can deliver to the knee joint while the subject walks on level ground at varied speeds.

Design, Modeling, and Experimental Validation of a Novel Infinitely Variable Transmission Based on Scotch Yoke Systems

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
X. F. Wang ◽  
W. D. Zhu
Keyword(s):  
Planetary Gear ◽  
Speed Ratio ◽  
Control Module ◽  
Kinematic Behavior ◽  
Input Control ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Planetary Gear Sets ◽  
Noncircular Gears ◽  
Crank Length

A novel infinitely variable transmission (IVT) based on scotch yoke systems is designed to provide a continuously varied output-to-input speed ratio from zero to a specified value. By changing the crank length of scotch yoke systems, the speed ratio of the IVT can be continuously adjusted. The IVT consists of a pair of noncircular gears and two modules: an input-control module and a motion conversion module. The input-control module employs two planetary gear sets to combine the input speed of the IVT with the control speed from the stepper motor that changes the crank length of scotch yoke systems. The motion conversion module employs two scotch yoke systems to convert the combined speeds from the input-control module to translational speeds of yokes, and the translational speeds are converted to output speeds through rack–pinions. The speed ratio between the output of the motion conversion module and the input of the input-control module has a shape of a sinusoidal-like wave, which generates instantaneous variations. Use of scotch yoke systems provides a benefit to isolate the interaction between the crank length and the shape of the speed ratio, and a pair of noncircular gears can be used to eliminate the instantaneous variations of the speed ratio for all crank lengths. A prototype of the IVT was built and instrumented, and its kinematic behavior was experimentally validated. A driving test was conducted to examine the performance of the IVT.

Design, Modeling, and Simulation of a Geared Infinitely Variable Transmission

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
X. F. Wang ◽  
W. D. Zhu
Keyword(s):  
Planetary Gear ◽  
Speed Ratio ◽  
Start Up ◽  
Continuous Output ◽  
Direction Control ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Planetary Gear Sets ◽  
Working Principle ◽  
Crank Length

An infinitely variable transmission (IVT) to provide a continuous output-to-input speed ratio from zero to a certain value is designed, and its working principle is illustrated. It is a geared IVT (GIVT), since its function to achieve the continuously varied speed ratio is implemented by gears. Crank-slider systems are used in the GIVT; the output-to-input speed ratio is changed with the crank length. Racks and pinions, whose motion is controlled by planetary gear sets, are used to change the crank length when the cranks rotate. One-way bearings are used to rectify output speeds from different crank-slider systems to obtain the output speed of the GIVT. Since the crank-slider systems can introduce variations of the instantaneous speed ratio, a pair of noncircular gears is designed to minimize the variations. A direction control system is also designed for the GIVT using planetary gear sets. Finally, a vehicle start-up simulation and a wind turbine simulation to maintain a constant generator speed are developed based on a GIVT module in the Matlab Simulink environment.

Dynamic Analysis of a Geared Infinitely Variable Transmission

2016 ◽  
Vol 12 (3) ◽  
Author(s):  
X. F. Wang ◽  
Z. R. Li ◽  
W. D. Zhu
Keyword(s):  
Dynamic Analysis ◽  
Speed Ratio ◽  
Force Analysis ◽  
Maximum Torque ◽  
Input Shaft ◽  
Continuous Output ◽  
Input Side ◽  
Variable Transmission ◽  
Infinitely Variable Transmission ◽  
Output Side

Dynamic analysis of a geared infinitely variable transmission (IVT) that can generate a continuous output-to-input speed ratio from zero to a certain value is studied for vehicle and wind turbine applications. With the IVT considered as a multirigid-body system, the Lagrangian approach is used to analyze its speeds and accelerations, and the Newtonian approach is used to conduct force analysis of each part of the IVT. Instantaneous input and output speeds and accelerations of the IVT have variations in one rotation of its input shaft. This work shows that the instantaneous input speed has less variation than the instantaneous output speed when the inertia on the input side is larger than that on the output side and vice versa. The maximum torque on the output shaft that is a critical part of the IVT increases with the input speed.

Thermomechanical Coupling of a Hyper-viscoelastic Truck Tire and a Pavement Layer and its Impact on Three-dimensional Contact Stresses

2021 ◽  
pp. 036119812110171
Author(s):  
Angeli Jayme ◽  
Imad L. Al-Qadi
Keyword(s):  
Contact Stress ◽  
Contact Area ◽  
Three Dimensional ◽  
Interaction Model ◽  
Rolling Resistance ◽  
Contact Stresses ◽  
Thermomechanical Coupling ◽  
Temperature Profiles ◽  
Near Surface ◽  
Truck Tire

A thermomechanical coupling between a hyper-viscoelastic tire and a representative pavement layer was conducted to assess the effect of various temperature profiles on the mechanical behavior of a rolling truck tire. The two deformable bodies, namely the tire and pavement layer, were subjected to steady-state-uniform and non-uniform temperature profiles to identify the significance of considering temperature as a variable in contact-stress prediction. A myriad of ambient, internal air, and pavement-surface conditions were simulated, along with combinations of applied tire load, tire-inflation pressure, and traveling speed. Analogous to winter, the low temperature profiles induced a smaller tire-pavement contact area that resulted in stress localization. On the other hand, under high temperature conditions during the summer, higher tire deformation resulted in lower contact-stress magnitudes owing to an increase in the tire-pavement contact area. In both conditions, vertical and longitudinal contact stresses are impacted, while transverse contact stresses are relatively less affected. This behavior, however, may change under a non-free-rolling condition, such as braking, accelerating, and cornering. By incorporating temperature into the tire-pavement interaction model, changes in the magnitude and distribution of the three-dimensional contact stresses were manifested. This would have a direct implication on the rolling resistance and near-surface behavior of flexible pavements.

Mechanical Analysis of Disc Cam Mechanisms with Negative Radius Roller Translating Follower

2012 ◽  
Vol 184-185 ◽  
pp. 301-306
Author(s):  
Rong Fu Lin ◽  
Yong Chang
Keyword(s):  
Contact Stress ◽  
Mechanical Analysis ◽  
Cam Mechanism

This paper proposes the conditions of no-undercutting and contact-retaining of the disc cam mechanism with negative radius roller follower. Then, it presents the contact stress expression based on the mechanical analysis. In addition, the effects of different parameters on the force and contact stress are analysed. The results show that the contact stress can be reduced by designing the suitable parameters of the cam.

scholarly journals Co-Design of CVT-Based Electric Vehicles

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1825
Author(s):  
Caiyang Wei ◽  
Theo Hofman ◽  
Esin Ilhan Caarls
Keyword(s):  
Cooling System ◽  
Design Method ◽  
Low Cost ◽  
Cost Effective ◽  
Speed Ratio ◽  
Air Flow Rate ◽  
Cost Of Ownership ◽  
Variable Transmission ◽  
Primary Focus ◽  
Design Freedom

For an electric vehicle (EV) with a continuously variable transmission (CVT), a novel convex programming (CP)-based co-design method is proposed to minimize the total-cost-of-ownership (TCO). The integration of the electric machine (EM) and the CVT is the primary focus. The optimized system with co-design reduces the TCO by around 5.9% compared to a non-optimized CVT-based EV (based on off-the-shelf components) and by around 2% compared to the EV equipped with a single-speed transmission (SST). By taking advantage of the control and design freedom provided by the CVT, the optimal CVT, EM and battery sizes are found to reduce the system cost. It simultaneously finds the optimal CVT speed ratio and air-flow rate of the cooling system reducing the energy consumption. The strength of co-design is highlighted by comparing to a sequential design, and insights into the design of a low-power EV that is energy-efficient and cost-effective for urban driving are provided. A highly integrated EM-CVT system, which is efficient, low-cost and lightweight, can be expected for future EV applications.

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