Two Wheels Connected by an Unactuated Variable Length Axle on Uneven Ground: Kinematic Modeling and Experiments

1999 ◽  
Vol 121 (2) ◽  
pp. 235-240 ◽  
Author(s):  
B. J. Choi ◽  
S. V. Sreenivasan ◽  
P. W. Davis
Keyword(s):  
Kinematic Model ◽  
Length Change ◽  
Variable Length ◽  
Future Research ◽  
Uneven Surface ◽  
Kinematic Modeling ◽  
Uneven Terrain ◽  
Contact Points ◽  
Prismatic Joints ◽  
Modeling And Experiments

It has been shown in previous work that when two wheels independently joined by a fixed-length axle are placed on an uneven surface, such that the line joining the wheel contact points is not coplanar with the axle, rolling without slip is possible only if the wheels are driven at the same speed. Otherwise, the wheels must slip against the terrain due to kinematic constraints. Based on analytical kinematics, it is shown in this article that a method to prevent slip on uneven terrain is to use a variable length axle. This research explores the instantaneous and gross motion of two wheels joined by a variable length axle on uneven terrain. Next, the overall range of the axle length change is investigated through numerical simulations. Based on the results from the simulation, a novel variable length axle that possesses no prismatic joints, hence has low friction, and has high stiffness has been designed. Experimental results are obtained for the axle length change as a three wheeled laboratory prototype that includes the variable length axle travels on a smooth uneven surface. These experiments verify the kinematic model. Limitations of using an unactuated variable length axle and related future research topics are also discussed.

Kinematics of Two Wheels Joined by a Variable-Length Axle on Uneven Terrain

1997 ◽  
Author(s):  
P. W. Davis ◽  
S. V. Sreenivasan ◽  
B. J. Choi
Keyword(s):  
Flat Surface ◽  
Variable Length ◽  
Uneven Surface ◽  
Kinematic Constraints ◽  
Uneven Terrain ◽  
Fixed Length ◽  
Contact Points

Abstract If two thin wheels independently joined by a fixed-length axle are placed on a flat surface, the wheels can roll on the surface without slipping, regardless of the speed at which the wheels are driven. However, if the same system is placed on an uneven surface, such that the line joining the wheel contact points is not coplanar with the axle, rolling without slip is possible only if the wheels are driven at the same speed. Otherwise, the wheels must slip against the terrain due to kinematic constraints. One method to prevent slip on uneven terrain is to use a variable-length axle. This research explores the instantaneous and gross motion of two wheels joined by a variable-length axle on uneven terrain. The end result is an algorithm to simulate this vehicle rolling on two arbitrarily oriented planes.

Three-Dimensional Kinematic Analysis of a Two Actuated Spoke Wheel Robot Based on Its Equivalency to a Serial Manipulator

2008 ◽  
Author(s):  
Ping Ren ◽  
Ya Wang ◽  
Dennis Hong
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Forward Kinematics ◽  
Future Research ◽  
Ground Contact ◽  
Contact Points ◽  
Prismatic Joints ◽  
Forward Kinematic ◽  
The Relationship

In this paper, the inverse and forward kinematics of a novel mobile robot that utilizes two actuated spoke wheels is presented. Intelligent Mobility Platform with Active Spoke System (IMPASS) is a wheel-leg hybrid robot that can walk in unstructured environments by stretching in or out three independently actuated spokes of each wheel. First, the unique locomotion scheme of IMPASS is introduced. Then the configuration of the robot when each of its two spoke wheels has one spoke in contact with the ground is modeled as a two-branch parallel mechanism with spherical and prismatic joints. An equivalent serial manipulator of the 2-SP mechanism with the same degrees of freedom is proposed to solve for the inverse and forward kinematic problems. The relationship between the physical limits of the stroke of the spokes (effective spoke length) and the limits of its equivalent degree of freedom is established. This approach can also be expanded to deal with the forward and inverse kinematics of other configurations which has more than two ground contact points. Several examples are used to illustrate the method. The results obtained will be used in the future research on the motion planning of IMPASS walking in unstructured environment.

scholarly journals Modeling in ADAMS of a 6R industrial robot

2018 ◽  
Vol 184 ◽  
pp. 02006
Author(s):  
Mariana Ratiu ◽  
Alexandru Rus ◽  
Monica Loredana Balas
Keyword(s):  
Dynamic Analysis ◽  
Industrial Robot ◽  
Kinematic Model ◽  
Future Research ◽  
Robot Motion ◽  
Cad Model ◽  
3D Cad ◽  
Revolute Joints ◽  
Real Model ◽  
Articulated Robot

In this paper, we present the first steps in the process of the modeling in ADAMS MBS of MSC software of the mechanical system of an articulated robot, with six revolute joints. The geometric 3D CAD model of the robot, identical to the real model, in the PARASOLID format, is imported into ADAMS/View and then are presented the necessary steps for building the kinematic model of the robot. We conducted this work, in order to help us in our future research, which will consist of kinematic and dynamic analysis and optimization of the robot motion.

scholarly journals Realtime Motion Assessment For Rehabilitation Exercises: Integration Of Kinematic Modeling With Fuzzy Inference

2014 ◽  
Vol 4 (4) ◽  
pp. 267-285 ◽  
Author(s):  
Wenbing Zhao ◽  
Roanna Lun ◽  
Deborah D. Espy ◽  
M. Ann Reinthal
Keyword(s):  
Fuzzy Inference ◽  
Kinematic Model ◽  
Integrated Approach ◽  
Kinematic Modeling ◽  
Motion Data ◽  
Fuzzy Interference System ◽  
Novel Approach ◽  
Motion Assessment ◽  
Rehabilitation Exercises ◽  
Rehabilitation Exercise

Abstract This article describes a novel approach to realtime motion assessment for rehabilitation exercises based on the integration of comprehensive kinematic modeling with fuzzy inference. To facilitate the assessment of all important aspects of a rehabilitation exercise, a kinematic model is developed to capture the essential requirements for static poses, dynamic movements, as well as the invariance that must be observed during an exercise. The kinematic model is expressed in terms of a set of kinematic rules. During the actual execution of a rehabilitation exercise, the similarity between the measured motion data and the model is computed in terms of their distances, which are then used as inputs to a fuzzy interference system to derive the overall quality of the execution. The integrated approach provides both a detailed categorical assessment of the overall execution of the exercise and the degree of adherence to individual kinematic rules.

A New Cam-follower Safety Joint Mechanism Design based on Variable-length Four-bar Linkage for Robot Safety

2021 ◽  
pp. 1-24
Author(s):  
Seung Guk Baek ◽  
Hyungpil Moon ◽  
Hyouk Ryeol Choi ◽  
Ja Choon Koo
Keyword(s):  
Load Transfer ◽  
Impact Damage ◽  
Surface Profile ◽  
Length Change ◽  
Variable Length ◽  
Core Element ◽  
Nonlinear Load ◽  
Cam Follower ◽  
Joint Mechanism ◽  
The Impact

Abstract Humans come into physical contacts with various machines such as robots in daily life. This leads to the underlying issue of guaranteeing safety during such human-robot interactions. Thus, many devices and methods have been studied for impact damage reduction. A safety joint mechanism (SJM) using four-bar linkages has been highlighted as an impact cutoff device owing to its capabilities of nonlinear load transfer. This paper focuses on a new design and testing for a kinematic element of an SJM based on four-bar linkages to improve the impact cutoff performances. In the present work, a set of variable-length floating link designs is proposed, and the mechanism is implemented by mechanical contact surface profile shaping between the cams and followers. The performance of the cam-follower mechanism is evaluated depending on the variable length of the floating link, by using equivalent stiffness method, which successfully quantifies the performance of the proposed mechanism. Based on this design and analysis, two SJMs having symmetrical arrangements for four numbers of cam-follower mechanisms are fabricated: one SJM has fixed-length floating links and the other has variable-length floating links. The effect of the new kinematic elements on the performance improvement is verified by comparing the absorbed impact rates of the two SJMs by impact hammer-like drop tests. Consequently, it is confirmed that the rapid length change of the floating link is the core element for improving the performance of the safety mechanism.

scholarly journals Torso height optimization for bipedal locomotion

2018 ◽  
Vol 15 (5) ◽  
pp. 172988141880444 ◽  
Author(s):  
Arne-Christoph Hildebrandt ◽  
Konstantin Ritt ◽  
Daniel Wahrmann ◽  
Robert Wittmann ◽  
Felix Sygulla ◽  
...  
Keyword(s):  
Real Time ◽  
Kinematic Model ◽  
Bipedal Locomotion ◽  
Full Potential ◽  
Normal Walking ◽  
Kinematic Range ◽  
Bipedal Robots ◽  
Uneven Terrain ◽  
2D Model

Bipedal robots can be better alternatives to other robots in certain applications, but their full potential can only be used if their entire kinematic range is cleverly exploited. Generating motions that are not only dynamically feasible but also take into account the kinematic limits as well as collisions in real time is one of the main challenges towards that goal. We present an approach to generate adaptable torso height trajectories to exploit the full kinematic range in bipedal locomotion. A simplified 2D model approximates the robot’s full kinematic model for multiple steps ahead. It is used to optimize the torso height trajectories while taking future motion kinematics into account. The method significantly improves the robot’s motion not only while walking in uneven terrain, but also during normal walking. Furthermore, we integrated the method in our framework for autonomous walking and we validated its real-time character in successfully conducted experiments.

Active Disturbance Rejection Control for Handling Slip in Tracked Vehicle Locomotion

2019 ◽  
Vol 11 (2) ◽  
Author(s):  
Bijo Sebastian ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Disturbance Rejection ◽  
Path Tracking ◽  
Future Research ◽  
Ground Vehicles ◽  
Uneven Terrain ◽  
Active Disturbance Rejection ◽  
Package Delivery ◽  
Disturbance Rejection Control ◽  
Effective Slip ◽  
High Level

This paper describes the use of an active disturbance rejection controller (ADRC) to estimate and compensate for the effect of slip in an online manner to improve the path tracking performance of autonomous ground vehicles (AGVs). AGVs with skid-steer locomotion mode are extensively used for robotic applications in the fields of agriculture, transportation, construction, warehouse maintenance, and mining. Majority of these applications such as performing reconnaissance and rescue operations in rough terrain or autonomous package delivery in urban scenarios, require the system to follow a path predetermined by a high-level planner or based on a predefined task. In the absence of effective slip estimation and compensation, the AGVs, especially tracked vehicles, can fail to follow the path as given out by the high-level planner. The proposed ADRC architecture uses a generic mathematical model that can account for the scaling and shift in the states of the system due to the effects of slip through augmented parameters. An extended Kalman filter (EKF) observer is used to estimate the varying slip parameters online. The estimated parameters are then used to compensate for the effects of slip at each iteration by modifying the control actions given by a low-level path tracking controller. The proposed approach is validated through experiments over flat and uneven terrain conditions including asphalt, vinyl flooring, artificial turf, grass, and gravel using a tracked skid-steer mobile robot. A detailed discussion on the results and directions for future research is also presented.

scholarly journals Kinematic Modeling of Six-Axis Industrial Robot and its Parameter Identification: A Tutorial

2021 ◽  
Vol 15 (5) ◽  
pp. 599-610
Author(s):  
Md. Moktadir Alam ◽  
◽  
Soichi Ibaraki ◽  
Koki Fukuda
Keyword(s):  
Present Model ◽  
Industrial Robot ◽  
Local Coordinate System ◽  
Kinematic Model ◽  
Kinematic Modeling ◽  
Positioning Accuracy ◽  
Rotary Axis ◽  
Model Based ◽  
Absolute Positioning ◽  
The Absolute

In advanced industrial applications, like machining, the absolute positioning accuracy of a six-axis robot is indispensable. To improve the absolute positioning accuracy of an industrial robot, numerical compensation based on positioning error prediction by the Denavit and Hartenberg (D-H) model has been investigated extensively. The main objective of this study is to review the kinematic modeling theory for a six-axis industrial robot. In the form of a tutorial, this paper defines a local coordinate system based on the position and orientation of the rotary axis average lines, as well as the derivation of the kinematic model based on the coordinate transformation theory. Although the present model is equivalent to the classical D-H model, this study shows that a different kinematic model can be derived using a different definition of the local coordinate systems. Subsequently, an algorithm is presented to identify the error sources included in the kinematic model based on a set of measured end-effector positions. The identification of the classical D-H parameters indicates a practical engineering application of the kinematic model for improving a robot’s positioning accuracy. Furthermore, this paper presents an extension of the present model, including the angular positioning deviation of each rotary axis. The angular positioning deviation of each rotary axis is formed as a function of the axis’ command angles and the direction of its rotation to model the effect of the rotary axis backlash. The identification of the angular positioning deviation of each rotary axis and its numerical compensation are presented, along with their experimental demonstration. This paper provides an essential theoretical basis for the error source diagnosis and error compensation of a six-axis robot.

scholarly journals Terrain-Perception-Free Quadrupedal Spinning Locomotion on Versatile Terrains: Modeling, Analysis, and Experimental Validation

2021 ◽  
Vol 8 ◽  
Author(s):  
Hongwu Zhu ◽  
Dong Wang ◽  
Nathan Boyd ◽  
Ziyi Zhou ◽  
Lecheng Ruan ◽  
...  
Keyword(s):  
Motion Tracking ◽  
Center Of Mass ◽  
Kinematic Model ◽  
Linear Quadratic Regulator ◽  
Small Scale ◽  
Small Range ◽  
Linear Quadratic ◽  
Stability Margins ◽  
Uneven Terrain ◽  
Quadruped Robots

Dynamic quadrupedal locomotion over rough terrains reveals remarkable progress over the last few decades. Small-scale quadruped robots are adequately flexible and adaptable to traverse uneven terrains along the sagittal direction, such as slopes and stairs. To accomplish autonomous locomotion navigation in complex environments, spinning is a fundamental yet indispensable functionality for legged robots. However, spinning behaviors of quadruped robots on uneven terrain often exhibit position drifts. Motivated by this problem, this study presents an algorithmic method to enable accurate spinning motions over uneven terrain and constrain the spinning radius of the center of mass (CoM) to be bounded within a small range to minimize the drift risks. A modified spherical foot kinematics representation is proposed to improve the foot kinematic model and rolling dynamics of the quadruped during locomotion. A CoM planner is proposed to generate a stable spinning motion based on projected stability margins. Accurate motion tracking is accomplished with linear quadratic regulator (LQR) to bind the position drift during the spinning movement. Experiments are conducted on a small-scale quadruped robot and the effectiveness of the proposed method is verified on versatile terrains including flat ground, stairs, and slopes.

scholarly journals Kinematic Modelling of FES Induced Sit-to-stand Movement in Paraplegia

2017 ◽  
Vol 7 (6) ◽  
pp. 3060
Author(s):  
Mohammed Ahmed ◽  
M. S. Huq ◽  
B. S. K. K. Ibrahim
Keyword(s):  
Dynamic Model ◽  
Initial Phase ◽  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Future Research ◽  
Upper Limbs ◽  
Body System ◽  
Segmental Dynamics ◽  
Sit To Stand ◽  
Kinematic Modelling

FES induced movements from indication is promising due to encouraging results being obtained by scholars. The kinematic model usually constitute the initial phase towards achieving the segmental dynamics of any rigid body system. It can be used to ascertain that the model is capable of achieving the desired goal. The dynamic model builds on the kinematic model and is usually mathematically cumbersome depending on the number of degrees-of-freedom. This paper presents a kinematic model applicable for human sit-to-stand movement scenario that will be used to obtain the dynamic model the FES induced movement in a later study. The study shows that the 6 DOF conceptualized sit-to-stand movement can be achieved conveniently using 4 DOF. The 4 DOF has an additional joint compared to similar earlier works which makes more it accurate and flexible. It is more accurate in the sense that it accommodates additional joint i.e. the neck joint whose dynamics could be captured. And more flexible in the sense that if future research uncover more contributions by the segments it can be easily incorporated including that of other segments e.g. the trunk, neck and upper limbs.

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