Kinetostatic Design Considerations for an Articulated Leg-Wheel Locomotion Subsystem

2005 ◽  
Vol 128 (1) ◽  
pp. 112-121 ◽  
Author(s):  
Seung Kook Jun ◽  
Glenn D. White ◽  
Venkat N. Krovi
Keyword(s):  
Degree Of Freedom ◽  
Kinematic Synthesis ◽  
Design Synthesis ◽  
Single Degree Of Freedom ◽  
Uneven Terrain ◽  
Serial Chain ◽  
Vehicle Systems ◽  
Lower Pair ◽  
Adequate Ground

Our long-term goal is one of designing land-based vehicles to provide enhanced uneven-terrain locomotion capabilities. In this paper, we examine and evaluate candidate articulated leg-wheel subsystem designs for use in such vehicle systems. The leg-wheel subsystem designs under consideration consist of disk wheels attached to the chassis through an articulated linkage containing multiple lower-pair joints. Our emphasis is on creating a design that permits the greatest motion flexibility between the chassis and wheel while maintaining the smallest degree-of-freedom (DOF) within the articulated chain. We focus our attention on achieving two goals: (i) obtaining adequate ground clearance by designing the desired/feasible motions of the wheel axle, relative to the chassis, using methods from kinematic synthesis; and (ii) reducing overall actuation requirements by a judicious mix of structural equilibration design and spring assist. This process is examined in detail in the context of two candidate single-degree-of-freedom designs for the articulated-leg-wheel subsystems—a coupled-serial-chain configuration and a four-bar configuration. We considered the design synthesis of planar variants of the two candidate designs surmounting a representative obstacle profile while supporting a set of end-effector loads and highlight the key benefits in the presented results.

Design Considerations for an Articulated Leg-Wheel Locomotion Subsystem

2004 ◽  
Author(s):  
Seung Kook Jun ◽  
Venkat N. Krovi
Keyword(s):  
Sagittal Plane ◽  
Degree Of Freedom ◽  
Kinematic Synthesis ◽  
Ground Clearance ◽  
Uneven Terrain ◽  
Design Considerations ◽  
Serial Chain ◽  
Vehicle Systems ◽  
Lower Pair ◽  
Adequate Ground

In this paper, we examine and evaluate candidate articulated leg-wheel subsystem designs for use in vehicle systems with enhanced uneven-terrain locomotion capabilities. The leg-wheel subsystem designs under consideration consist of disk wheels attached to the chassis through an articulated linkage containing multiple lower-pair joints. Our emphasis is on creating a design that permits the greatest motion flexibility between the chassis and wheel while maintaining the smallest degree-of-freedom (d.o.f.) within the articulated chain. In particular, we focus our attention on achieving two goals: (i) obtaining adequate ground clearance by designing the desired/feasible motions of the wheel axle, relative to the chassis, using methods from kinematic synthesis; and (ii) reducing overall actuation requirements by a judicious mix of structural equilibration design and spring assist. We examine this process in the context of two candidate designs — a coupled-serial-chain configuration and four-bar-configuration — for the articulated-leg-wheel subsystem. The performance of planar variants of these designs, operating in the sagittal plane, is evaluated and representative results are presented to highlight the process.

scholarly journals Design of a Spatial RPR-2SS Valve Mechanism

2018 ◽  
Vol 10 (4) ◽  
Author(s):  
Peter L. Wang ◽  
Ulrich Rhem ◽  
J. Michael McCarthy
Keyword(s):  
Tunnel Boring Machine ◽  
Degree Of Freedom ◽  
Valve Mechanism ◽  
Kinematic Synthesis ◽  
Soil Conditioning ◽  
Spatial Mechanism ◽  
Tunnel Boring ◽  
Serial Chain ◽  
Smooth Movement ◽  
Cylindrical Array

This paper applies kinematic synthesis theory to obtain the dimensions of a constrained spatial serial chain for a valve mechanism that cleans and closes a soil conditioning port in a tunnel boring machine. The goal is a smooth movement that rotates a cylindrical array of studs into position and then translates it forward to clean and close the port. The movement of the valve is defined by six positions of the revolute-prismatic-revolute (RPR) serial chain. These six positions are used to compute the dimensions of the two spherical spherical (SS) dyads that constrain the RPR chain to obtain a one degree-of-freedom spatial mechanism. An example design of this valve mechanism is provided in detail.

Fourier Methods for Kinematic Synthesis of Coupled Serial Chain Mechanisms

2005 ◽  
Vol 127 (2) ◽  
pp. 232-241 ◽  
Author(s):  
Xichun Nie ◽  
Venkat Krovi
Keyword(s):  
Low Cost ◽  
Synthesis Method ◽  
Path Following ◽  
Degree Of Freedom ◽  
Dimensional Synthesis ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Serial Chain ◽  
End Effectors ◽  
Serial Chains

Single degree-of-freedom coupled serial chain (SDCSC) mechanisms are a class of mechanisms that can be realized by coupling successive joint rotations of a serial chain linkage, by way of gears or cable-pulley drives. Such mechanisms combine the benefits of single degree-of-freedom design and control with the anthropomorphic workspace of serial chains. Our interest is in creating articulated manipulation-assistive aids based on the SDCSC configuration to work passively in cooperation with the human operator or to serve as a low-cost automation solution. However, as single-degree-of-freedom systems, such SDCSC-configuration manipulators need to be designed specific to a given task. In this paper, we investigate the development of a synthesis scheme, leveraging tools from Fourier analysis and optimization, to permit the end-effectors of such manipulators to closely approximate desired closed planar paths. In particular, we note that the forward kinematics equations take the form of a finite trigonometric series in terms of the input crank rotations. The proposed Fourier-based synthesis method exploits this special structure to achieve the combined number and dimensional synthesis of SDCSC-configuration manipulators for closed-loop planar path-following tasks. Representative examples illustrate the application of this method for tracing candidate square and rectangular paths. Emphasis is also placed on conversion of computational results into physically realizable mechanism designs.

scholarly journals A Design System for Six-Bar Linkages Integrated With a Solid Modeler

2015 ◽  
Vol 15 (4) ◽  
Author(s):  
Kaustubh H. Sonawale ◽  
J. Michael McCarthy
Keyword(s):  
Degree Of Freedom ◽  
Design System ◽  
Solid Model ◽  
Design Algorithm ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Serial Chain ◽  
Tolerance Zones ◽  
Spherical Linkages ◽  
Solid Modeler

This paper presents a design system for planar and spherical six-bar linkages, which is integrated with a solid modeler. The user specifies a backbone 3R chain in five task configurations in the sketch mode of the solid modeler and executes the design system. Two RR constraints are computed, which constrain the 3R chain to a single degree-of-freedom six-bar linkage. There are six ways that these constraints can be added to the 3R serial chain to yield as many as 63 different linkages in case of planar six-bar linkages and 165 in case of spherical six-bar linkages. The performance of each candidate is analyzed, and those that meet the required task are presented to the designer for selection. The design algorithm is run iteratively with random variations applied to the task configurations within user-specified tolerance zones, to increase the number of candidate designs. The output is a solid model of the six-bar linkage. Examples are presented, which demonstrate the effectiveness of this strategy for both planar and spherical linkages.

Kinematic and Kinetostatic Synthesis of Planar Coupled Serial Chain Mechanisms

2002 ◽  
Vol 124 (2) ◽  
pp. 301-312 ◽  
Author(s):  
Venkat Krovi ◽  
G. K. Ananthasuresh ◽  
Vijay Kumar
Keyword(s):  
Degree Of Freedom ◽  
Dimensional Synthesis ◽  
Single Degree Of Freedom ◽  
End Effector ◽  
Solution Approach ◽  
Single Degree ◽  
Design Specifications ◽  
Serial Chain ◽  
Gear Trains ◽  
External Loads

Single Degree-of-freedom Coupled Serial Chain (SDCSC) mechanisms form a novel class of modular and compact mechanisms with a single degree-of-freedom, suitable for a number of manipulation tasks. Such SDCSC mechanisms take advantage of the hardware constraints between the articulations of a serial-chain linkage, created using gear-trains or belt/pulley drives, to guide the end-effector motions and forces. In this paper, we examine the dimensional synthesis of such SDCSC mechanisms to perform desired planar manipulation tasks, taking into account task specifications on both end-effector motions and forces. Our solution approach combines precision point synthesis with optimization to realize optimal mechanisms, which satisfy the design specifications exactly at the selected precision points and approximate them in the least-squares sense elsewhere along a specified trajectory. The designed mechanisms can guide a rigid body through several positions while supporting arbitrarily specified external loads. Furthermore, torsional springs are added at the joints to reduce the overall actuation requirements and to enhance the task performance. Examples from the kinematic and the kinetostatic synthesis of planar SDCSC mechanisms are presented to highlight the benefits.

Dimensional Synthesis of CRR Serial Chains

2003 ◽  
Author(s):  
Alba Perez ◽  
J. M. McCarthy
Keyword(s):  
Degree Of Freedom ◽  
Dimensional Synthesis ◽  
Dual Quaternion ◽  
Kinematic Synthesis ◽  
Revolute Joints ◽  
Serial Chain ◽  
In Series ◽  
Synthesis Methodology ◽  
Serial Chains

This paper presents the kinematic synthesis of a CRR serial chain. This is a four-degree-of-freedom chain constructed from a cylindric joint and two revolute joints in series. The design equations for this chain are obtained from the dual quaternion kinematics equations evaluated at a specified set of task positions. In this case, we find that the chain is completely defined by seven task positions. Furthermore, our solution of these equations has yielded 52 candidate designs, so far; there may be more. This synthesis methodology shows promise for the design of constrained serial chains.

Evaluating Plane Curves As Constraints for Locomotion on Uneven Terrain

2020 ◽  
Author(s):  
Chang Liu ◽  
Mark Plecnik
Keyword(s):  
Physical Mechanism ◽  
Mechanical Design ◽  
Plane Curves ◽  
Kinematic Synthesis ◽  
Single Degree Of Freedom ◽  
Mechanical Advantage ◽  
Work Related ◽  
Uneven Terrain ◽  
Physical Mechanisms ◽  
Single Degree

Abstract This paper focuses on preliminary work related to the discovery of single degree-of-freedom mechanism paths useful for dynamic locomotion tasks. The objective is to bridge a gap between kinematic specifications and emerging dynamic behaviors. This is accomplished by formulating a set of ordinary differential equations that includes essential mechanism characteristics (path traced, mechanical advantage) but excludes all physical mechanism parameters (topology, link lengths). The dynamics represent a rotation constrained body propelled by a foot that is attached to that body by a user-defined path. The foot is powered by a series-elastic actuator acting through a mechanical advantage function that is defined across the length of the path. Through this framework, a range of user-defined paths were tested for effective locomotion on flat and complex terrains. Foot paths and mechanical advantage functions exist outside of any mechanical design, with the goal to discover paradigms worth instantiating into physical mechanisms, a task reserved for kinematic synthesis. This work would empower existing kinematic synthesis techniques to achieve dynamic requirements. In other words, kinematic requirements are transformed from an end to a means. Their dynamic utility would be evaluated by the framework presented in this paper rather than pursued by themselves.

Serial Chains of Spherical Four-Bar Mechanisms to Achieve Design Helices

2014 ◽  
Author(s):  
Kevin S. Giaier ◽  
Andrew P. Murray ◽  
David H. Myszka
Keyword(s):  
Design Methodology ◽  
Degree Of Freedom ◽  
Spherical Equivalent ◽  
Kinematic Synthesis ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Spherical Mechanisms ◽  
Spherical Mechanism ◽  
Serial Chains

This paper presents a method for designing serial chains of spherical four-bar mechanisms that can achieve up to five design helices. The chains are comprised of identical copies of the same four-bar mechanism by connecting the coupler of the prior spherical mechanism to the base link of the subsequent spherical mechanism. Although having a degree of freedom per mechanism, the design methodology is based upon identically actuating each mechanism. With these conditions, the kinematic synthesis task of matching periodically spaced points on up to five arbitrary helices may be achieved. Due to the constraints realized via the spherical equivalent of planar Burmester Theory, spherical mechanisms produce at most five prescribed orientations resulting in this maximum. The methodology introduces a companion helix to each design helix along which the intersection locations of each spherical mechanisms axes must lie. As the mechanisms are connected by rigid links, the distance between the intersection locations along the companion helices is a constant. An extension to the coupler matches the points along the design helices. An approach to mechanically reducing the chain of mechanisms to a single degree of freedom is also presented. Finally, an example shows the methodology applied to three design helices.

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