Kinematic Constraint Maps and C-space Singularities for Planar Mechanisms with Prismatic Joints

Amirinezhad, S. Vahid; Donelan, Peter

doi:10.1007/978-3-319-93188-3_25

Cited by 5 publications

(6 citation statements)

References 12 publications

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“…where d is a design parameter [2]. In practice, it is both sufficient and easier to work with norm squared φ 2 j .…”

Section: Joint Variablesmentioning

confidence: 99%

“…However, they illustrate this robust approach, and provide a coherent explanation of forward and inverse kinematic singularities for parallel manipulators. The KCM approach to their C-spaces is given in [1,2]. The manipulators consist of k = 8 rigid bodies, where we regard the ambient space as the fixed base.…”

Section: Examplesmentioning

confidence: 99%

“…(b) 3-RPR. Actuating the prismatic joints r 4 , r 5 , r 6 , so φ i , i = 4, 5, 6 as given in equation (2), are joint variables, the input mapping can be taken as:…”

Section: -Rpr Planar Parallel Manipulatormentioning

confidence: 99%

“…Following a method proposed by Piipponnen and Tuomela [9], the authors have developed a differential geometric approach to defining the configuration space (C-space) for a manipulator, based solely on constraints imposed on component links by the joints [1,2]. This approach, called the kinematic constraint mapping (KCM), demonstrates that, for a given family of manipulators, typically there is a single Grashof-type condition, expressible in terms of design parameters, for which the C-space has a singularity [3].…”

Section: Introductionmentioning

confidence: 99%

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Input and output singularities for parallel manipulators

Amirinezhad

Donelan

2019

Advances in Mechanism and Machine Science

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“…where d is a design parameter [2]. In practice, it is both sufficient and easier to work with norm squared φ 2 j .…”

Section: Joint Variablesmentioning

confidence: 99%

Section: Examplesmentioning

confidence: 99%

“…(b) 3-RPR. Actuating the prismatic joints r 4 , r 5 , r 6 , so φ i , i = 4, 5, 6 as given in equation (2), are joint variables, the input mapping can be taken as:…”

Section: -Rpr Planar Parallel Manipulatormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Input and output singularities for parallel manipulators

Amirinezhad

Donelan

2019

Advances in Mechanism and Machine Science

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“…Finally in Chapters 6-9, we will apply our constraint-based approach to several serial and parallel manipulators and perform a full kinematic analysis including singularities. Some of the results in the thesis have been published already or are planned to appear [65,66,67,68,69].…”

Section: Thesis Structurementioning

confidence: 99%

A Constraint-Based Approach to Manipulator Kinematics and Singularities

Amirinezhad¹

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<p>In this thesis, a differential-geometric approach to the kinematics of multibody mechanisms is introduced that enables analysis of singularities of both serial and parallel manipulators in a flexible and complete way. Existing approaches such as those of Gosselin and Angeles [1], Zlatanov et al. [2] and Park and Kim [3] make use of a combination of joint freedoms and constraints and so build in assumptions. In contrast, this new approach is solely constraint-based, avoiding some of the shortcomings of these earlier theories. The proposed representation has two core ingredients. First, it avoids direct reference to the choice of inputs and their associated joint freedoms and instead focuses on a kinematic constraint map (KCM), defined by the constraints imposed by all joints and not requiring consideration of closure conditions arising from closed loops in the design. The KCM is expressed in terms of pose (i.e. position and orientation) variables, which are the coordinates of all the manipulator’s links with respect to a reference frame. The kinematics of a given manipulator can be described by means of this representation, locally and globally. Also, for a family of manipulators defined by a specific architecture, the KCM will tell us how the choice of design parameters (e.g. link lengths) affects these kinematic properties within the family. At a global level, the KCM determines a subset in the space of all pose variables, known as the configuration space (C-space) of the manipulator, whose topology may vary across the set of design parameters. The Jacobian (matrix of first-order partial derivatives) of the KCM may become singular at some specific choices of pose variables. These conditions express a subset called the singular set of the C-space. It is shown that if a family of manipulators, parametrised by a manifold Rd of design parameters, is “well-behaved” then the pose variables can be eliminated from the KCM equations together with the conditions for singularities, to give conditions in terms of design parameters, that define a hypersurface in Rd of manipulators in the class that exhibit C-space singularities. These are referred to as Grashof-type conditions, as they generalise classically known inequalities classifying planar 4-bar mechanisms due to Grashof [4]. Secondly, we develop the theory to incorporate actuator space (A-space) and workspace (W-space), based on a choice of actuated joints or inputs and on the manipulator’s end-effector workspace or outputs. This will facilitate us with a framework for analysing singularities for forward and inverse kinematics via input and output mappings defined on the manipulator’s C-space. This provides new insight into the structure of the forward and inverse kinematics, especially for parallel manipulators. The theory is illustrated by a number of applications, some of which recapitulate classical or known results and some of which are new.</p>

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