Force Distribution Characteristics of Actively Reconfigurable Wheeled Vehicle Systems

1996 ◽  
Author(s):  
S. V. Sreenivasan ◽  
P. Nanua
Keyword(s):  
Geometric Approach ◽  
Companion Paper ◽  
Internal Force ◽  
Force Distribution ◽  
Partial Control ◽  
Uneven Terrain ◽  
Redundantly Actuated ◽  
Singular Configuration ◽  
Actuation Scheme ◽  
Wheeled Vehicles

Abstract This paper addresses the force distribution issues associated with redundantly actuated wheeled vehicles that are suited for operation on uneven terrain. Basic results relating to the partitioning of motion and force variables in these mechanisms are developed. The redundant actuation scheme allows for the control of force distribution in the system, in addition to motion control. The unique kinematic characteristics of wheeled systems, that makes these vehicles ‘singular’ on even terrain, and ‘near-singular’ on uneven terrain; and the presence of ‘kinematic slipping’ when these vehicles move on uneven terrain make their force distribution mathematics distinct from other systems considered in the literature. In a singular configuration, it is shown here that these active wheeled vehicles possess only a partial control over their internal force distribution. A procedure to partition the ‘force space’ into controllable and uncontrollable spaces is provided based on a geometric approach. Closed-form force space results are included for an actively articulated multi-module system (a generalization of a passive, articulated mobile robot that has been studied extensively in literature). The force distribution in actively reconfigurable wheeled vehicles is closely related to their rate kinematics. Rate kinematics of these vehicles has been studied in a companion paper [SN96].

Kinematic Geometry of Wheeled Vehicle Systems

1996 ◽  
Author(s):  
S. V. Sreenivasan ◽  
P. Nanua
Keyword(s):  
Geometric Approach ◽  
Companion Paper ◽  
Kinematic Chains ◽  
Uneven Terrain ◽  
Geometric Conditions ◽  
Kinematic Study ◽  
Vehicle Systems ◽  
Motion Characteristics ◽  
The One ◽  
Wheeled Vehicles

Abstract This paper addresses instantaneous motion characteristics of wheeled vehicles systems on even and uneven terrain. A thorough kinematic geometric approach which utilizes screw system theory is used to investigate vehicle-terrain combinations as spatial mechanisms that possess multiple closed kinematic chains. It is shown that if the vehicle-terrain combination satisfies certain geometric conditions, for instance when the vehicle operates on even terrain, the system becomes singular or non-Kutzbachian — it possesses finite range mobility that is different from the one obtained using Kutzbach criterion. An application of this geometric approach to the study of rate kinematics of various classes of wheeled vehicles is also included. This approach provides an integrated framework to study the kinematic effects of varying the vehicle and/or terrain geometric parameters from their nominal values. In addition, design enhancements of existing vehicles are suggested using this approach. This kinematic study is closely related to the force distribution characteristics of wheeled vehicles which is the subject of the companion paper [SN96].

Partial Contact Force Controllability in Active Wheeled Vehicles

1998 ◽  
Vol 123 (2) ◽  
pp. 169-175 ◽  
Author(s):  
B. J. Choi ◽  
S. V. Sreenivasan
Keyword(s):  
Contact Force ◽  
Geometric Approach ◽  
Contact Forces ◽  
Force Distribution ◽  
Distribution Problem ◽  
Passive Components ◽  
Uneven Terrain ◽  
Partial Contact ◽  
Force Components ◽  
Wheeled Vehicles

This paper presents a geometric approach for solving the force distribution problem in active wheeled vehicles (AWVs) moving on uneven surfaces. Here an active vehicle is defined as a system that includes independent actuators for all its internal joints. In general, AWVs do not possess omni-directional mobility, and they possess fewer actuators than the number of wheel-ground contact force components. This article presents an approach for separating the contact force vectors into active and passive components such that there exists an invertible square matrix that maps the active contact forces to the actuator efforts. An appropriate force allocation algorithm can then be developed for these systems. The concepts introduced in this article are demonstrated via an example of AWVs on uneven terrain. An example of force distribution in active legged vehicles (ALVs) that possess the same number of actuators as contact forces is also provided for comparison.

Kinematic Geometry of Wheeled Vehicle Systems

1999 ◽  
Vol 121 (1) ◽  
pp. 50-56 ◽  
Author(s):  
S. V. Sreenivasan ◽  
P. Nanua
Keyword(s):  
Spherical Surface ◽  
Geometric Approach ◽  
First Order ◽  
Uneven Terrain ◽  
Geometric Conditions ◽  
Wheeled Vehicle ◽  
Kinematic Analyses ◽  
Motion Characteristics ◽  
The One ◽  
Wheeled Vehicles

This paper utilizes a kinematic-geometric approach to study the first-order motion characteristics of wheeled vehicles on even and uneven terrain. The results obtained from first-order studies are compared to those obtained from second order kinematic analyses, and special situations where the first-order analysis is inadequate are discussed. This approach is particularly suited for studying actively actuated vehicles since their designs typically do not include intentional passive compliances. It is shown that if a vehicle-terrain combination satisfies certain geometric conditions, for instance when a wheeled vehicle operates on even terrain or on a spherical surface, the system possesses a singularity—it possesses finite range mobility that is higher than the one obtained using Kutzbach criterion. On general uneven terrain, the same vehicles require undesirable ‘kinematic slipping’ at the wheel-terrain contacts to attain the mobility that it possesses on these special surfaces. The kinematic effects of varying the vehicle and/or terrain geometric parameters from their nominal values are discussed. The design enhancements that are required in existing off-road vehicles to avoid kinematic slipping are presented for a class of vehicles that include two-wheel axles in their designs.

Body Vibrations of a Legged Walking Machine

1992 ◽  
Author(s):  
Xiaochun Gao ◽  
Shin-Min Song
Keyword(s):  
The Body ◽  
Robotic Systems ◽  
Force Distribution ◽  
Walking Machine ◽  
Foot Force ◽  
Robot Hands ◽  
Machine Systems ◽  
External Loads ◽  
Wheeled Vehicles ◽  
Quadrupedal Walking

Abstract Unlike in wheeled vehicles, compliance in walking machine systems changes due to the variation of leg geometry, as its body proceeds. This variation in compliance will cause vibration, even if external loads remain constant. A theory is thus developed to predict the body vibrations of a walking machine during walking. On the other hand, dynamic foot forces under body vibrations can be computed by application of the existing numerical methods. As an example, the body vibrations of a quadrupedal walking chair under different walking conditions are simulated in terms of the developed theory. The results show that the influence of body vibrations on the foot force distribution is essential and, in some cases, the walking chair may lose its stability due to its body vibrations, even though it is identified to be stable in a quasi-static analysis. The developed theory can also be extended to other similar multi-limbed robotic systems, such as multi-fingered robot hands.

scholarly journals Mobility evaluation of wheeled robots on soft terrain: Effect of internal force distribution

2016 ◽  
Vol 100 ◽  
pp. 259-282 ◽  
Author(s):  
Bahareh Ghotbi ◽  
Francisco González ◽  
József Kövecses ◽  
Jorge Angeles
Keyword(s):  
Internal Force ◽  
Force Distribution ◽  
Wheeled Robots ◽  
Terrain Effect

Loading Analysis and Mathematical Calculation for Arc Axis of the Exponential Function

2013 ◽  
Vol 834-836 ◽  
pp. 1382-1385
Author(s):  
Li Xiang ◽  
Zhu Feng ◽  
Zhai Qiu ◽  
Ruo Yin Zhang
Keyword(s):  
Exponential Function ◽  
Internal Force ◽  
Force Distribution ◽  
Shipping Industry ◽  
Uniform Load ◽  
Concentrated Load ◽  
Long Span ◽  
Mathematical Calculation ◽  
Dangerous Section ◽  
Loading Analysis

The concept of arch longitudinal beam wharf was brought out in the contemporary shipping industry of China as a result of the conflict between traditional high-piled wharfs and the increasing size of freights. Different alignments of arch axis will lead to different internal force distributions and the most dangerous section. A series of equations for the arch axis are derived through the transformation of the exponential function under a 40-meter-long span. Based on the analysis of equations affected by the combined force of uniform load and concentrated load, it is providing reference for engineers and analysts with the internal force distribution under some commonly used axis and the location of the most dangerous section for the archs.

Force Distribution With Pose-Dependent Force Boundaries for Redundantly Actuated Cable-Driven Parallel Robots

2016 ◽  
Vol 8 (4) ◽  
Author(s):  
Han Yuan ◽  
Eric Courteille ◽  
Dominique Deblaise
Keyword(s):  
Energy Consumption ◽  
Lower Boundary ◽  
Parallel Robots ◽  
Force Distribution ◽  
Computational Accuracy ◽  
Boundary Method ◽  
Redundantly Actuated ◽  
Cable Forces ◽  
Reducing Energy

This paper addresses the force distribution of redundantly actuated cable-driven parallel robots (CDPRs). A new and efficient method is proposed for the determination of the lower-boundary of cable forces, including the pose-dependent lower-boundaries. In addition, the effect of cable sag is considered in the calculation of the force distribution to improve the computational accuracy. Simulations are made on a 6DOF CDPR driven by eight cables to demonstrate the validity of the proposed method. Results indicate that the pose-dependent lower-boundary method is more efficient than the fixed lower-boundary method in terms of minimizing the motor size and reducing energy consumption.

scholarly journals Fastener Scaffold Stability Analysis and Experimental Research Under Non-Uniform Distributed Load

2017 ◽  
Vol 11 (1) ◽  
pp. 873-886
Author(s):  
Dong Chen ◽  
Yuzhuo Wang ◽  
Xiping He
Keyword(s):  
Load Distribution ◽  
Stability Limit ◽  
Limit Load ◽  
Internal Force ◽  
Force Distribution ◽  
Numerical Studies ◽  
Distributed Load ◽  
Transfer Rules ◽  
Geometry Nonlinearity ◽  
Vertical Bars

Introduction: An experiment was carried out on the basis of material nonlinearity, geometry nonlinearity and semi rigid fasteners for the internal force distribution and transfer rules of the scaffold. Methods: This paper presents results from a set of numerical studies on the influence of the random imperfection method, the interaction of various imperfections and the most disadvantageous stability limit load. Result and Conclusion: Data from numerical studies indicate that stress at the top of the vertical bar was larger within the scope of load; and the horizontal bar and brace participated in the work of the scaffold. The internal force that came through the two types of bars enabled us to realize the redistribution in every vertical bar in order to decrease the stress from the top to the bottom of the vertical bars and involve them in the work of the scaffold. Data from numerical studies also indicates that these imperfections all interact with each other and the load distribution also influences the scaffold’s stability.

The Experimental Study on Mechanical Performance of Multi-Span Column-Supported Assembly Box Concrete Hollow Floor

2013 ◽  
Vol 351-352 ◽  
pp. 560-565
Author(s):  
Kao Zhong Zhao ◽  
Guang Yi Wang
Keyword(s):  
Static Load ◽  
Mechanical Performance ◽  
Internal Force ◽  
Force Distribution ◽  
Support Section ◽  
Distribution Law ◽  
Specific Distribution ◽  
Floor Structure ◽  
External Forces

Assembly box concrete hollow floor sructure is a new-style whole structure that are constituted by the a cross section of a concrete box composed of small prefabricated components (concrete superposition box) and a cast-in-place concrete rib beam.The internal force distribution law was analyzed in this paper, based on the static load experiment with a multi span column-supported assembly box concrete hollow floor.The findings prove that the prefabricated boxs and cast-in-situ concrete ribbed beams are able to form a whole to jointly bear external forces, that the internal force distribution law is basically the same with the solid cast-in-situ concrete floor with no beams, and that the floor structure can be simplified to the column strip and middle strip.The specific distribution ratios between the minus moment and the plus moment of the column strip and middle strip respectively are as follows. For the angel area floor(contianed edge beams), the ratio of midspan section is 0.537:0.463, the ratio of support section is 0.816:0.184; for the edge area floor(contianed edge beams), the ratio of midspan section is 0.51:0.49, the ratio of support section is 0.808：0.192; for the inner area floor, the ratio of midspan section is 0.55:0.45, the ratio of support section is 0.75:0.25.

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