An optimal wheel-torque control on a compliant modular robot for wheel-slip minimization

Robotica ◽  
2015 ◽  
Vol 35 (2) ◽  
pp. 463-482 ◽  
Author(s):  
Avinash Siravuru ◽  
Suril V. Shah ◽  
K. Madhava Krishna
Keyword(s):  
Friction Coefficient ◽  
Normal Force ◽  
Experimental Studies ◽  
Traction Force ◽  
Static Stability ◽  
Wheel Speed ◽  
Torque Control ◽  
Modular Robot ◽  
Wheel Slip ◽  
Wheel Torque

SUMMARYThis paper discusses the development of an optimal wheel-torque controller for a compliant modular robot. The wheel actuators are the only actively controllable elements in this robot. For this type of robots, wheel-slip could offer a lot of hindrance while traversing on uneven terrains. Therefore, an effective wheel-torque controller is desired that will also improve the wheel-odometry and minimize power consumption. In this work, an optimal wheel-torque controller is proposed that minimizes the traction-to-normal force ratios of all the wheels at every instant of its motion. This ensures that, at every wheel, the least traction force per unit normal force is applied to maintain static stability and desired wheel speed. The lower this is, in comparison to the actual friction coefficient of the wheel-ground interface, the more margin of slip-free motion the robot can have. This formalism best exploits the redundancy offered by a modularly designed robot. This is the key novelty of this work. Extensive numerical and experimental studies were carried out to validate this controller. The robot was tested on four different surfaces and we report an overall average slip reduction of 44% and mean wheel-torque reduction by 16%.

A Self-Actuating Traction-Drive Speed Reducer

2004 ◽  
Vol 127 (4) ◽  
pp. 631-636 ◽  
Author(s):  
Donald R. Flugrad ◽  
Abir Z. Qamhiyah
Keyword(s):  
Friction Coefficient ◽  
Normal Force ◽  
Drive System ◽  
Traction Drive ◽  
Sliding Motion ◽  
Output Torque ◽  
Speed Reducer ◽  
Rolling Elements ◽  
Drive Speed ◽  
High Output

Traction-drive speed reducers offer certain advantages over geared speed reducers. In particular, they generally run quieter than geared units and provide an opportunity for higher efficiency by eliminating sliding motion between contacting elements. In order to generate a sufficiently high output torque, some means must be provided to create a normal force between the rolling elements. This normal force, along with the friction coefficient, enables the device to transmit torque from one rolling member to the next. The speed reducer proposed here is designed so that the configuration of the rolling elements creates the needed normal force in response to the torque exerted back on the system by the downstream loading. Thus the device is self-actuating. Since the normal force is only present when needed, the rolling elements of the device can readily be disengaged, thus eliminating the need for a separate clutch in the drive system. This feature can be exploited to design a transmission with several distinct speed ratios that can be engaged and disengaged in response to changing speed requirements.

scholarly journals Modelling of Friction Coefficient for Shoes Type LL By Means of Polynomial Fitting

2018 ◽  
Vol 12 (1) ◽  
pp. 114-127 ◽  
Author(s):  
L. Cantone ◽  
A. Ottati
Keyword(s):  
Experimental Data ◽  
Friction Coefficient ◽  
Input Data ◽  
Normal Force ◽  
Loading Conditions ◽  
Polynomial Fitting ◽  
Maximum Acceleration ◽  
Stopping Distance ◽  
Freight Traffic ◽  
Brake Cylinder

Introduction: The paper describes the automatic procedure, implemented in UIC software TrainDy, for the simulation of friction coefficient of new LL shoes, used to avoid noise from freight traffic. Method: This procedure uses certified experimental data obtained at dynamometer bench as input data and computes a series of polynomials laws that describe the evolution of friction coefficient with speed, for different values of normal force between brake blocks and wheel and for different initial braking speeds. Result: Numerical results are compared against two series of experimental slip tests, carried on Trenitalia freight wagons, in terms of both stopping distances (for different starting speeds and loading conditions) and pressure in brake cylinder, speed and acceleration. Errors in terms of stopping distance are always below 5% whereas errors in terms of maximum acceleration are up to 20%.

Statistical Cutting Force Model for Orthogonal Cutting of Polytetrafluoroethylene (PTFE) Composites

2013 ◽  
Author(s):  
Felicia Stan ◽  
Daniel Vlad ◽  
Catalin Fetecau
Keyword(s):  
Friction Coefficient ◽  
Cutting Force ◽  
Feed Rate ◽  
Normal Force ◽  
Polynomial Regression ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Cutting Parameters ◽  
Tool Geometry ◽  
Force Model

This paper presents an experimental investigation of the cutting forces response during the orthogonal cutting of polytetrafluoroethylene (PTFE) and PTFE-based composites using the Taguchi method. Cutting experiments were conducted using the L27 orthogonal array and the effects of the cutting parameters (feed rate, cutting speed and rake angle) on the cutting force were analyzed using the S/N ratio response and the analysis of variance (ANOVA). Statistical models that correlate the cutting force with process variables were developed using ANOVA and polynomial regression. The variation of the apparent friction coefficient was analyzed with respect to tool geometry and the cutting process. The results indicated that cutting and thrust forces increase with increasing feed rate, and decrease with increasing rake angles from negative to positive values and increasing cutting speed. A power law relationship between the apparent friction coefficient and the normal force exerted by the chip on the tool-rake face was identified, the former decreasing with an increasing normal force.

Investigation of Grinding Force and Surface Integrity of IC10 in Creep Feed Grinding

2020 ◽  
Author(s):  
Jun-chen Li ◽  
Wen-hu Wang ◽  
Rui-song Jiang ◽  
Xiao-fen Liu ◽  
Huang Bo ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Tool Wear ◽  
Material Removal ◽  
Normal Force ◽  
Removal Rate ◽  
Tangential Force ◽  
Grinding Force ◽  
Wheel Speed ◽  
Creep Feed Grinding ◽  
Creep Feed

Abstract The IC10 superalloy material is one of the most important materials for aero-engine turbine blade due to its excellent performances. However, it is difficult to be machined because of its special properties such as terrible tool wear and low machined efficiency. The creep feed grinding is widely used in machining IC10 superalloy due to the advance in reducing tool wear, improving material removal rate and surface quality. The creep feed grinding is a promising machining process with the advantages of high material removal rate due to large cutting depth, long cutting arc and very slow workpiece, and its predominant features might have significant influence on the grinding force and surface quality for the workpiece. Hence, it is of great importance to study the grinding force and surface integrity in creep feed grinding IC10 superalloy. In this paper, a series of orthogonal experiments have been carried out and the effects of grinding parameters on the grinding force and the surface roughness are analyzed. The topographies and defects of the machined surface were observed and analyzed using SEM. The results of the experiments show that the tangential force is decreased with the workpiece speed increasing. However, there is no significant change in tangential force with the increasing of grinding depth and wheel speed. The normal force is decreased with the workpiece speed increasing when the workpiece speed is less than 150 mm/min, but when the workpiece speed is more than 150 mm/min the normal force is increased tardily. Moreover, the normal force is increased sharply with the increase of grinding depth and is increased slowly with the increase of wheel speed. In general, the surface roughness is increased with workpiece speed and grinding depth increasing, while the trend of increase corresponding that of workpiece speed is more evident. The value of the surface roughness is decreased with wheel speed increasing. And it is found out that the main defect is burning of the IC10 superalloy material in creep feed grinding by energy spectrum analysis of some typical topography in this study.

scholarly journals Evaluation of the effectiveness of anti-turbulent additives in the oil pipeline transportation

2020 ◽  
Vol 157 ◽  
pp. 02005
Author(s):  
Aleksei Balabukha ◽  
Valentina Zvereva
Keyword(s):  
Friction Coefficient ◽  
Experimental Studies ◽  
Computer Application ◽  
Eastern Siberia ◽  
Practical Application ◽  
Pipeline Transportation ◽  
Pressure Losses ◽  
Oil Pipeline ◽  
Oil Pipelines ◽  
High Degree

The authors of the article have developed the computer application allows to determine the value of the friction coefficient λ and anti-turbulent additives efficiency with a high degree of accuracy. The program can be used in the calculations and design of oil pipelines. The paper presents experimental studies of the effect anti-turbulent additives on the magnitude of pressure losses during fluid movement through pipes. The data gained by the developed computer program has been proved by the data of practical application of additives in the real oil pipeline transportation system called Eastern Siberia-Pacific Ocean oil pipeline.

Inverse Wheel Dynamics

2006 ◽  
Author(s):  
V. V. Vantsevich
Keyword(s):  
Angular Velocity ◽  
Power Distribution ◽  
Vehicle Dynamics ◽  
Inverse Dynamics ◽  
Equation Of Motion ◽  
Torque Control ◽  
Vehicle Performance ◽  
Performance Control ◽  
Wheel Torque ◽  
And Performance

Wheel dynamics is a significant component of vehicle dynamics and performance analysis. This paper presents an innovative method of studying wheel dynamics and wheel performance control based on the inverse dynamics formulation of the problem. Such an approach opens up a new way to the optimization and control of both vehicle dynamics and vehicle performance by optimizing and controlling power distribution to the drive wheels. An equation of motion of a wheel is derived first from the wheel power balance equation that makes the equation more general. This equation of motion is considered the basis for studying both direct and inverse wheel dynamics. The development of a control strategy on the basis of the inverse wheel dynamics approach includes wheel torque control that provides a wheel with both the referred angular velocity and rolling radius and also with the required functionals of quality. An algorithm for controlling the angular velocity is presented as the first part in the implementation of the developed strategy of the inverse wheel dynamics/performance control.

Testing Technology of Dynamic Road Friction Coefficient

2013 ◽  
Vol 312 ◽  
pp. 249-253 ◽  
Author(s):  
Peng Zhang ◽  
Li Lin Cui ◽  
Le He ◽  
Qun Sheng Xia
Keyword(s):  
Friction Coefficient ◽  
Personal Computer ◽  
Slip Rate ◽  
Test System ◽  
Wheel Speed ◽  
Adhesion Coefficient ◽  
Testing Technology ◽  
Road Friction ◽  
Road Friction Coefficient ◽  
Real Vehicle

The dynamic road adhesion coefficients at 30km/h and 50km/h for dry condition were measured through the real vehicle equipped with a test system driving on the asphalt dry road. The test system included the fifth wheel instrument, the wheel speed sensors, the programmed strain amplifier and ACME portable industrial personal computer. The results show that longitudinal peak adhesion coefficients at 30km/h and 50km/h for the dry condition are about 0.7. Longitudinal adhesion coefficient increases rapidly with the slip rate increasing and soon reaches the maximum. The longitudinal peak adhesion coefficient occures when the slip rate is about 12%.

Scratching of Elastic∕Plastic Materials With Hard Spherical Indenters

2008 ◽  
Vol 75 (6) ◽  
Author(s):  
Shane E. Flores ◽  
Michael G. Pontin ◽  
Frank W. Zok
Keyword(s):  
Friction Coefficient ◽  
Normal Force ◽  
Scaling Relations ◽  
Elastic Plastic ◽  
Plastic Materials ◽  
Finite Element Calculations ◽  
Plastic Analysis ◽  
Elastic Plastic Materials ◽  
Scratch Tests ◽  
Theoretical Results

A mechanistic framework has been developed for interpreting scratch tests performed with spherical indenters on elastic∕plastic materials. The pertinent scaling relations have been identified through a plastic analysis and the model has been subsequently calibrated by finite element calculations. The results show that the ratio of scratch force to normal force (or apparent friction coefficient) can be partitioned into two additive components: one due to interfacial friction and another associated with plastic deformation. The plastic component scales parabolically with the normal force and depends only weakly on the true (elastic) friction coefficient. A simple formula for the scratch force, based on the plastic analysis and the numerical results, has been derived. Finally, experimental measurements on two material standards commonly used for nanoindenter calibration have been used to verify the theoretical results.

Construct and energy reserves improvement of exploitative properties rail friction brake

2020 ◽  
pp. 26-30
Author(s):  
Yuriy Vladimirovich Krivosheya ◽  
◽  
Tatyana Leonidovna Ripol-Saragosi ◽  
Keyword(s):  
Friction Coefficient ◽  
Experimental Studies ◽  
Disc Brake ◽  
Energy Reserves ◽  
Analytical Assessment ◽  
Improved Performance ◽  
Design Options ◽  
The Relationship ◽  
Friction Brake

The paper gives an assessment of the design and energy reserves for improving the operational properties of the railway friction brake under the existing mass-dimensional restrictions and the growth of braking energy. The criterion for assessing the operational properties of the friction brake is the friction coefficient and contact energy load. The results of experimental studies of the relationship between the frictional characteristics of the disc brake and the affecting structural and loadspeed factors are presented. Design options for railway friction brakes are proposed that provide improved performance. A comparative analytical assessment of the contact energy load of new friction brake and classic disc brake options has been performed.

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