Open access peer-reviewed chapter

# Higher-Order Kinematics in Dual Lie Algebra

Written By

Daniel Condurache

Submitted: September 28th, 2019 Reviewed: February 16th, 2020 Published: March 21st, 2020

DOI: 10.5772/intechopen.91779

From the Edited Volume

## Advances on Tensor Analysis and their Applications

Edited by Francisco Bulnes

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## Abstract

In this chapter, using the ring properties of dual number algebra, vector and tensor calculus, a computing method for the higher-order acceleration vector field properties in general rigid body motion is proposed. The higher-order acceleration field of a rigid body in a general motion is uniquely determined by higher-order time derivative of a dual twist. For the relative kinematics of rigid body motion, equations that allow the determination of the higher-order acceleration vector field are given, using an exponential Brockett-like formula in the dual Lie algebra. In particular cases, the properties for velocity, acceleration, jerk, and jounce fields are given. This approach uses the isomorphism between the Lie algebra of the rigid displacements se(3), of the Special Euclidean group, SE3,and the Lie algebra of dual vectors. The results are coordinate free and in a closed form.

### Keywords

• higher-order kinematics
• dual algebra
• lie group

## 1. Introduction

The kinematic analysis of multibody systems has been traditionally considered as the determination of the positions, velocities, accelerations, jerks and jounces of their constitutive members. This is an old field with a long history, which has attracted the attention of mathematicians and engineers. Michel Chasles discovered (1834) that any rigid body displacement is equivalent to a screw displacement [1]. Screw theory is an efficient mathematical tool for the study of spatial kinematics. The pioneering work of Ball [2], the treatises of Hunt [3], and Phillips [4] and the multitude of contributions appearing in the literature are evidence of this. The isomorphism between screw theory and the Lie algebra, se(3), of the Special Euclidean group, SE3, provide with a wealth of results and techniques from modern differential geometry and Lie group theory [5, 6, 7, 8, 9].

A kinematic mapping relates the motion of a rigid body to the joint motions of a kinematic chain. Its time derivatives yield the twist, acceleration, jerk and jounce etc. of the body. Time derivatives of the twists of members in a kinematic chain and derivatives of screws are essential operations in kinematics. Recognizing the Lie group nature of rigid body motions, and correspondingly the Lie algebra nature of screws, Karger [5], Rico et al. [6], Lerbet [7] and Müller [8, 9] derived closed form expressions of higher-order time derivatives of twist.

In this chapter, using the tensor calculus and the dual numbers algebra, a new computing method for studying the higher-order accelerations field properties is proposed in the case of the general rigid body motion. For the spatial kinematic chains, equations that allow the determination of the nth order accelerations field are given, using a Brockett-like formula. The crucial observation is that the nth order time derivative of twist of the terminal body in a kinematic chain can be determined by propagating the kth order time derivative of twists of the bodies in the chain, for k=0,n¯. The results are coordinate-free and in a closed form.

## 2. Theoretical consideration on rigid body motion

The general framework of this chapter is a rigid body that moves with respect to a fixed reference frame R0. Consider another reference frame R originated in a point Q that moves together with the rigid body. Let ρQ denote the position vector of point Q with respect to frame R0, vQ its absolute velocity and aQ its absolute acceleration.

Then the vector parametric equation of motion is:

ρ=ρQ+RrE1

where ρ represents the absolute position of a generic point P of the rigid body with respect to R0 and R=Rt is an orthogonal proper tensorial function in SO3R. Vector r is constant and it represents the relative position vector of the arbitrary point P with respect to R.

The results of this section succinctly present the velocity and acceleration vector field in rigid body motion. These results lead to the generalization presented in the next section.

With the denotations that were introduced, the vector fields of velocities and accelerations are described by:

vvQ=ṘRTρρQaaQ=R¨RTρρQE2

Tensors:

Φ1=ṘRTΦ2=R¨RTE3

represent the velocity tensor respectively the acceleration tensor. Tensor Φ1=ωso3R is the skew-symmetric tensor associated to the instantaneous angular velocity ωV3R . Tensor Φ2=ω2+ε, where ε=ω̇ is the instantaneous angular acceleration of the rigid body. One may remark that vectors:

a1=vΦ1ρ=vQΦ1ρQa2=aΦ2ρ=aQΦ2ρQE4

do not depend on the choice of point P of the rigid body. They are called the velocity invariant respectively the acceleration invariant (at a given moment of time).

### 2.1 The velocity field in rigid body motion

It is described by:

vvQ=Φ1ρρQE5

The instantaneous angular velocity ω of the rigid body may be determined as ω=vectΦ1. The major property that may be highlighted from Eq. (4) is that the velocity of a given point of the rigid may be computed when knowing the velocity tensor Φ1 and the velocity invariant a1:

v=a1+Φ1ρE6

### 2.2 The acceleration field in rigid body motion

It is described by

aaQ=Φ2ρρQE7

The absolute acceleration of a given point of the rigid body may be computed when knowing the acceleration tensor Φ2 and the acceleration invariant a2:

a=a2+Φ2ρE8

The instantaneous angular acceleration of the rigid body may be determined as:

ε=vectΦ2E9

The determinant of tensor Φ2 is (see [10]): detΦ2=ω×ε2. It follows that if ω×ε0, then tensor Φ2.

is invertible and its inverse is (see [10]):

Φ21=1ω×ε2εε+ωω2ω2ε˜E10

It follows that if tensor Φ2 is non-singular, then for an arbitrary given acceleration a we may find a point of the rigid that has this acceleration. Its absolute position is given by (see also Eq. (8)):

ρ=Φ21aa2E11

Particularly, if Φ2 is non-singular, then there exists a point G of zero acceleration, named the acceleration center. Its absolute position vector is given by:

ρG=Φ21a2E12

## 3. The vector field of the nth order accelerations

This section extends some of the previous considerations to the case of the nth order accelerations. We define the nth order acceleration of a point as:

aρndndtnρ,n1E13

For n=1, it represents the velocity, and for n=2, the acceleration. By derivation with respect to time successively in Eq. (2), it follows that:

aρnaQn=RnRTρρQ,whereRndndtnRE14

We define:

ΦnRnRTE15

the nthorder acceleration tensor in rigid body motion. A vector invariant is immediately highlighted from Eq. (14) with the denotation (15). Vector:

an=aρnΦnρ=aQnΦnρQE16

does not depend on the choice of the point of the rigid body for which the acceleration an is computed. Vector an is named the invariant vector of the nthorder accelerations. Then Eq. (7) may be generalized as it follows:

aρnaQn=ΦnρρQE17

The next Theorem gives the fundamental properties of the vector field of the nth order accelerations.

Theorem 1. In the rigid body motion, at a moment of timet, there exist tensorΦndefined byEq. (15)and vectoransuch as:

aρnaQn=ΦnρρQan=aρnΦnρ=aQnΦnρQE18

for any point Pof the rigid body with the absolute position defined by vector ρ.

Remark 1. Given the absolute position of a point of the rigid body and knowingΦnandan, its acceleration is computed from:

aρn=an+ΦnρE19

Remark 2. TensorΦnand vectorangeneralize the notions of velocity/acceleration tensor respectively velocity/acceleration invariant. They are fundamental in the study of the vector field of thenthorder accelerations. The recursive formulas for computingΦnandanare:

Φn+1=Φ̇n+ΦnΦ1an+1=ȧn+Φna1,n1,whereΦ1=ω,a1=vQΦ1ρQE20

Remark 3. One may remark that fromEq. (20)it follows by direct computation:

Φn=Φn1Φ1+dn1dtn1Φ1+k=1n2dkdtn1Φnk1Φ1an=Φn1a1+dn1dtn1a1+k=1n2dkdtn1Φnk1a1,n3E21

Remark 4. By defining thenthorder instantaneousnthorder angular acceleration of the rigid bodyεndn1dtn1ω, it follows fromEq. (21)that its associated skew-symmetric tensor may be expressed asεn=dn1dtn1Φ1. The expression of the instantaneousnthorder angular acceleration is:

εn=vectΦnΦn1Φ1k=1n2dkdtkΦnk1Φ1,n3E22

### 3.1 Homogenous matrix approach to the field of nth order accelerations

The set of affine maps, g:V3V3,gu=Ru+w, where R is an orthogonal proper tensor and w a vector in V3 is a group under composition and it is called the group of direct affine isometries or rigid motions and it is denoted SE3. Any rigid finite motion may be described by such a map. Tensor R models the rotation of the considered rigid body and vector w its translation. An affine map from SE3 may be represented with a 4×4 square matrix:

g=Rw01E23

One may remark that the following relations hold true:

R1w101R2w201=R1R2R1w2+w101Rw011=RTRTw01E24

We may extend now SE3 to SE3R, the set of the functions with the domain ℝ and the range SE3. The parametric vector equation of the rigid body motion (1) may be rewritten with the help of a homogenous matrix function in SE3R like it follows:

ρ1=RρQ01r1E25

From Eq. (25), it follows that:

ρ̇0=Ṙρ̇Q00r1=Ṙρ̇Q00RTRTρQ01ρ1E26

and by making the computations and taking into account Eqs. (3) and (4) it follows that:

ρ̇0=Φ1a100ρ1E27

By using the previous considerations, it follows that Eq. (25) may be extended like:

aρn0=Φnan00ρ1E28

Eq. (28) represents a unified form of describing the vector field of the nth order accelerations in rigid body motion. The matrix:

Ψn=Φnan00E29

contains both the nth order acceleration tensor Φn and the vector invariant an. Eqs. (20) may be put in a compact form:

Ψn+1=Ψ̇n+ΨnΨ1,n1E30

If follows that Ψn may be written as:

Ψn=Ψn1Ψ1+dn1dtn1Ψ1+k=1n2dkdtkΨnΨ1,n3E31

## 4. Symbolic calculus of higher-order kinematics invariants

We will present a method for the symbolic calculation of higher-order kinematics invariants for rigid motion.

Let be an and Φn, nN vector invariant, respectively, tensor invariant for the nth order accelerations fields. We denote by

Ψn=Φnan00E32

and we have the following relationship of recurrence:

Ψn+1=Ψ̇n+ΨnΨ1,nNΨ1=ωv00E33

The pair of vectors ωv is also known as the spatial twist of rigid body.

Let be A the matrix ring

A=AM3×3RA=Φa00ΦLV3V3aV3E34

and AX the set of polynomials with coefficients in the non-commutative ring A. A generic element of AX has the form

PX=A0Xm+A1Xm1++Am1X+Am,AkA,k=0,m¯E35

Theorem 2. There is a unique polynomialPnAXsuch thatΨnwill be written as

Ψn=PnDΨ1,nNE36

whereD=ddtis the operator of time derivative.

Proof: Taking into account Eqs. (36) and (33) we will have the following relationship of recurrence for PnD:

Pn+1=DPn+PnΨ1P0=IE37

Since Ψ1=ωv00 it follows the next outcome.

Theorem 3. There is a unique polynomial with the coefficients in the non-commutative ringLV3V3such that the vector respectively the tensor invariants of thenthorder accelerations will be written as

an=PnvΦn=Pnω,nNE38

wherePnfulfills the relationship of recurrence

Pn+1=DPn+Pnω,nNP1=IE39

It follows

P2=D+ωP3=D2+ωD+2ω̇+ω2P4=D3+ωD2+3ω̇+ω2D+3ω¨+3ω̇ω+2ωω̇+ω3E40

Thus, it follows:

• the velocity field invariants

a1=vΦ1=ωE41

• the acceleration field invariants

a2=v̇+ωvΦ2=ω̇+ω2E42

• jerk field invariants

a3=v¨+ωv+2ω̇v+ω2vΦ3=ω¨+ωω̇+2ω̇ω+ω3E43

• hyper-jerk (jounce) field invariants

a4=v¨+ωv¨+3ω̇+ω2v̇+3ω¨v+3ω̇ωv+2ωω̇v+ω3vΦ4=ω¨+ωω¨+3ω̇+ω2ω̇+3ω¨ω+3ω̇ω2+2ωω̇ω+ω4E44

Remark 5. The higher-order time derivative of spatial twist solve completely the problem of determining the field of thenthorder acceleration of rigid motion.

### 4.1 Higher-order acceleration center and vector invariants of rigid body motion

Equation (16) may be written as

aρnϕnρ=aQnΦnρQ,nN.E45

This shows us that the vector function

In=aρnΦnρ,nNE46

has the same value in every point of the rigid body under the general spatial motion, at a given moment of time t. It represents a vector invariant of the n-th order acceleration field.

The invariant value of vector In is obtained for ρ=0 and it is the n-th order acceleration of the point of the rigid body that passes the origin of the fixed reference frame at a given moment of time: In=a0nan. Eq. (46) becomes:

aρn=an+ϕnρ.E47

Let be Φn be the adjugate tensor of Φn uniquely defined by:ΦnΦn=detΦnI.

From Eq. (46), results another invariant

Jn=ΦnaρndetΦnρ,nN.E48

The value of this invariant is Jn=Φnan.

In the specific case when tensor Φn is non-singular (detΦn0), from (47) results the position vector having an imposed n-th order acceleration a:

ρ=Φn1aan,nN.E49

In a particular case of the n-th order acceleration centerGn (i.e. the point that have a=0) on obtain:

ρGn=Φn1anE50

Assuming that the tensor Φn is non-singular, the previous relations lead to a new vector invariant that characterize the accelerations of n-th and m-th order (n,mN):

Km,n=aρmΦmΦn1aρn,m,nN.E51

The value of this invariant is Km,n=amΦmΦn1an.

The problem of the determination the adjugate tensor of the n-th acceleration tensor and the conditions in which these tensors are inversable is, as the author knows, still an open problem in theoretical kinematics field. We will propose a method based on the tensors algebra that will give a closed form, coordinate- free solution, dependent to the time derivative of spatial twist.

The vector field of the higher-order acceleration is a non-stationary vector field. Differential operator div and curl is expressed, taking into account Eq. (47), through the linear invariants of the tensor Φn, as below:

divaϱn=traceΦn
curlaϱn=2vectΦnE52

Let ΦLV3V3 a tensor and we note t=vectΦ and S=symΦ. The below theorem takes place.

Theorem 4. The adjugate tensor and determinant of the tensorΦis:

Φ=SSt+ttdetΦ=detS+tStE53

Let Φn the n-th order acceleration tensor, Φn=tn+Sn.

The vectors tn and the symmetric tensors Sn,nN can be obtained with the below recurrence relation:

tn+1=ṫn+12traceΦnIΦnTωt1=ωE54
Sn+1=Ṡn+symΦnωS1=0E55

It follows that:

• Velocity field: Φ1=ω, t1=ω, S1=0

Φ1=ωωdetΦ1=0E56

Φ1 is singular for any ω. In this case,

divaϱ1=0curlaϱ1=2ωE57

• Acceleration field: Φ2=ω2+ω̇,t2=ω̇,S2=ω2

Φ2=ωω2ω2ω̇˜+ω̇ω̇detΦ2=ω×ω̇2E58

Φ2 is nonsingular if and only if ω×ω̇0. In this case

Φ21=ω2ω̇˜ωω2ω̇ω̇ω×ω̇2E59
divaϱ2=2ω2
curlaϱ2=2ω̇.E60

• Jerk field: Φ3=ω¨+2ω̇ω+ωω̇+ω3,t3=ω¨+12ω̇×ωω2ω,S3=32ωω̇+ω̇ω,

Φ3=94ωω̇2+ω̇ω2+ω×ω̇ω̇×ωS3t3˜+t3t3
detΦ3=12t3×ω̇ω×t3+27ω·ω̇ω×ω̇24.E61

Φ3 is nonsingular if and only if 4ω̇×t3ω×t39ω·ω̇ω×ω̇2. In this case

Φ31==9ωω̇2+ω̇ω2+ω×ω̇ω̇×ω4S3t3˜+4t3t312t3×ω̇ω×t3+27ω·ω̇ω×ω̇2
divaϱ3=6ω·ω̇
curlaϱ3=2ω¨+ω̇×ω2ω2ω.E62

• Jounce field:

Φ4=ω...+ωω¨+3ω̇+ω2ω̇+3ω¨ω+3ω̇ω2+2ωω̇ω+ω4
t4=ω...+ω¨×ω2ω2ω̇4ω·ω̇ω
S4=2sym2ω¨ω+ω̇ω2+3ω̇2+ω4E63
S4=2sym3ω̇ωwω̇αωwωwwω3αω̇ω̇+αω4IE64
Φ4=S4S4t4˜+t4t4E65
detΦ4=α6ω×ω̇·w×ω̇ω×w2+2αω·w+3αω̇2+α23ω̇ωw2E66

In Eqs. (65) and (66), the following notation has been used:

w=ω¨ω×ω̇ω2ωα=ω42ω̇22ω·ω̇E67

If

3ω̇ωw2α6ω×ω̇·w×ω̇ω×w2+2αω·w+2αω̇2+α2E68

then Φ4 is inversible and

Φ41=Φ4detΦ4E69

In the hypothesis (68), there is jounce center, determined by

ρG4=Φ41a4
divaϱ4=24ω·ω¨+3ω̇2+ω4E70
curlaϱ4=2ω¨+2ω¨×ω4ω2ω̇8ω·ω̇ω

## 5. Dual algebra in rigid body kinematics

In this section, we will present some algebraic properties for dual numbers, dual vectors and dual tensors. More details can be found in [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25].

### 5.1 Dual numbers

Let the set of real dual numbers to be denoted by

R¯=a+εa0aa0Rε2=0ε0E71

where a=Rea¯ is the real part of a¯ and a0=Dua¯ the dual part. The sum and product between dual numbers generate a ring with zero divisors structure for R¯.

Any differentiable function f:SRR,f=fa can be completely defined on S¯R¯ such that:

f:S¯R¯R¯;fa¯=fa+εa0faE72

Based on the previous property, two of the most important functions have the following expressions: cosa¯=cosaεa0sina;sina¯=sina+εa0cosa;

### 5.2 Dual vectors

In the Euclidean space, the linear space of free vectors with dimension 3 will be denoted by V3. The ensemble of dual vectors is defined as:

V3¯=a+εa0aa0V3ε2=0ε0E73

where a=Rea¯ is the real part of a¯ and a0=Dua¯ the dual part. For any three dual vectors a¯,b¯,c¯, the following notations will be used for the basic products: a¯·b¯scalar product, a¯×b¯cross product and a¯b¯c¯=a¯·b¯×c¯—triple scalar product. Regarding algebraic structure, V¯3+·R is a free R¯-module [13, 14].

The magnitude of a¯, denoted by a¯, is the dual number computed from

a¯=a+εa0·aa,Rea¯0εa0,Rea¯=0E74

where . is the Euclidean norm. For any dual vector a¯V¯3, if a¯=1 then a¯ is called unit dual vector.

### 5.3 Dual tensors

An R¯-linear application of V¯3 into V¯3 is called an Euclidean dual tensor:

T¯λ¯1v¯1+λ¯2v¯2=λ¯1T¯v¯1+λ¯2T¯v¯2,λ¯1,λ¯2R¯,v¯1,v¯2V¯3E75

Let LV¯3V¯3 be the set of dual tensors, then any dual tensor T¯LV¯3V¯3 can be decomposed as T¯=T+εT0, where T,T0LV3V3 are real tensors. Also, the dual transposed tensor, denoted by T¯T, is defined by

v¯1·T¯v¯1=v¯2·T¯Tv¯1,v¯1,v¯2V¯3E76

while v¯1,v¯2,v¯3V¯3, Rev¯1v¯2v¯30 the determinant is

T¯v¯1T¯v¯2T¯v¯3=detT¯v¯1v¯2v¯3.E77

Orthogonal dual tensor maps are a powerful instrument in the study of the rigid motion with respect to an inertial and non-inertial reference frames.

Let the orthogonal dual tensor set be denoted by:

SO¯3=R¯LV¯3V¯3RR¯T=I¯detR¯=1E78

where SO3¯ is the set of special orthogonal dual tensors and I¯ is the unit orthogonal dual tensor.

Theorem 5 (Structure Theorem). For anyR¯SO¯3a unique decomposition is viable

R¯=I+ερRE79

whereRSO3andρV3are called structural invariants.

Taking into account the Lie group structure of SO¯3 and the result presented in previous theorem, it can be concluded that any orthogonal dual tensor R¯SO¯3 can be used globally parameterize displacements of rigid bodies.

Theorem 6 (Representation Theorem). For any orthogonal dual tensorR¯defined as inEq. (79), a dual numberα¯=α+εdand a dual unit vectoru¯=u+εu0can be computed to have the following equation, [13, 14, 15]:

R¯α¯u¯=I+sinα¯u¯+1cosα¯u¯2=expα¯u¯E80

The parameters α¯ and u¯ are called the natural invariants of R¯. The unit dual vector u¯ gives the Plücker representation of the Mozzi-Chasles axis [13, 14], while the dual angle α¯=α+εd contains the rotation angle α and the translated distance d.

The Lie algebra of the Lie group SO¯3 is the skew-symmetric dual tensor set denoted by so¯3=α¯LV¯3V¯3α¯=α¯T, where the internal mapping is α¯1α¯2=α¯1α¯2.

The link between the Lie algebra so¯3, the Lie group SO¯3, and the exponential map is given by the following.

Theorem 7. The mapping

exp:so¯3SO¯3,expα¯=eα¯=k=0α¯kk!E81

is well defined and onto.

log:SO¯3so¯3,logR¯=ψ¯so¯3expψ¯=R¯E82

and is the inverse of Eq. (81).

Based on Theorems 6 and 7, for any orthogonal dual tensor R¯, a dual vector ψ¯=α¯u¯=ψ+εψ0 can be computed and represents the screw dual vector, which embeds the screw axis and screw parameters.

The form of ψ¯ implies that ψ¯logR¯. The types of rigid displacements that can be parameterized by ψ¯ are:

• roto-translation if ψ0,ψ00andψ·ψ00ifψ¯R¯ andψ¯εR;

• pure translation if ifψ=0andψ00ifψ¯εR¯;

• pure rotation if ψ0andψ·ψ0=0ifψ¯R.

Theorem 8. The natural invariantsα¯=α+εd,u¯=u+εu0can be used to directly recover the structural invariantsRandρfromEq. (79):

R=I+sinαu+1cosαu2ρ=du+sinαu0+1cosαu×u0E83

Theorem 9 (isomorphism theorem). The special Euclidean groupSE3·andSO¯3·are connected via the isomorphism of the Lie groups

Φ:SE3SO¯3
Φg=I+ερRE84

whereg=Rρ01, RSO¯3, ρV3.

Remark 6. The inverse ofΦ is

Φ1:SO¯3SE3;Φ1R¯=Rρ01E85

whereR=ReR¯,ρ=vectDuR¯·RT .

## 6. Higher-order kinematics in dual Lie algebra

Being the rigid body motion given by the following parametric equation in a given reference frame:

ρ=ρtV3R=RtSO3E86

with tIR is time variable.

The dual orthogonal tensor that describes the rigid body motion is [13, 24]:

R¯=I+ερRE87

In relation (87), the skew symmetric tensor associated to the vector ρ is denoted by ρ.

It can be easily demonstrated [14, 15], that:

R¯R¯T=I¯
detR¯=1
a¯·b¯=R¯a¯·R¯b¯,a¯,b¯V¯3
R¯a¯×b¯=R¯a¯×R¯(b)¯,a¯,b¯V¯3E88

The tensor R transports the dual vectors from the body frame in the space frame with the conservation of the dual angles and the relative orientation of lines that corresponds to the dual vectors a¯andb¯.

The dual angular velocity for the rigid body motion (86) is given by (87):

ω¯=vectR¯̇R¯TE89

It can be demonstrated that:

ω¯=ω+εvE90

where

ω=vectṘRTE91

is the instantaneous angular velocity of the rigid body and

v=ρ̇ω×ρE92

is the linear velocity of a point of the rigid body that coincides with the origin of the reference frame at that given moment.

The dual angular velocity ω¯ completely characterizes the distribution of the velocity field of the rigid body. The pair (ω,v) is called “the twist of the rigid body motion” [13, 14].

Being:

V¯ρ=ω+εvρE93

the dual velocity for a point localized in the reference frame by the position vector ρ.

In (93), ω is the instantaneous angular velocity of the rigid body and vρ is the linear velocity of the point. Using the next equation,

eερ=I+ερE94

from (90), (92)(94), results:

eερV¯ρ=ω¯E95

Consequently, eεrV¯r is an invariant having the same value for any r.

Writing this invariant in two different points of the rigid body (noted with P and Q ), results that:

eεrPV¯P=eεrQV¯QE96

From (97), results:

V¯P=eεPQV¯QE97

with PQ=ρQρP.

Relation (97) is true for any P and Q.

Analogue with Eq. (95), the following invariants take place:

eερA¯ρ=ω̇¯,ρV3eερJ¯ρ=ω¨¯,ρV3eερH¯ρ=ω¨¯,ρV3E98

where we denoted

A¯ρ=ω̇+εAρJ¯ρ=ω¨+εJρH¯ρ=ω¨+εHρE99

with Aρ,Jρ,Hρ the reduced acceleration, reduced jerk, respectively the reduced hyper-jerk (jounce), in a point given by the position vector ρ:

Aρ=aρω×vρJρ=jρω×aρ2ω̇×vρHρ=hρω×jρ3ω̇×aρ3ω¨×vρE100

In (100), aρ, jρ and hρ are, respectively, the acceleration, the jerk, and the hyper-jerk (jounce), in a point given by the position vector ρ.

Analogue with Eq. (97) the following equations take place:

A¯P=eεPQ˜A¯QJ¯P=eεPQ˜J¯QH¯P=eεPQ˜H¯Q,E101

The lines corresponding to the dual vectors ω¯̇,ω¯¨,ω¯... represent the loci, where the vectors Aρ,Jρ,Hρ have the minimum module value. Supplementary,

AρρV3min=Duω¯̇JρρV3min=Duω¯¨HρρV3min=Duω¯...E102

Interesting is the fact that for the plane motion minAρ=minJρ=minHρ=0 because Duω¯̇=Duω¯¨=Duω¯...=0

All properties are extended for higher-order accelerations. The vector ω¯n=dnω¯dtn,nN describes completely the helicoidally field of the n order reduced accelerations, for nN:

eερA¯ρn=ω¯nE103

In Eq. (103)A¯ρn denote the nth order of the dual reduced acceleration in a given point by the position vector ρ.

It follows that the dual part of the nth order differentiation of ω¯n

ω¯n=ωn+εvnE104

is the nth order reduced acceleration of that point of the rigid body that at the given time pass by the origin of the reference frame.

From equation

v=ρ̇ω×ρE105

it follows that

vn=ρn+1k=0nCnkωk×ρnk,nNE106

with the following notations

aρnρn+1,nNE107

for the nN order acceleration of the point given by the position vector ρ and

Aρnaρnk=0n1CnkωnkaρkE108

for the nth order reduced acceleration of the same point the equation:

Aρn=vn+ωn×ρE109

which proves the character of the helicoidally field of the nth order reduced accelerations field.

For ρ=0, the relations between the nth order reduced acceleration and the n order acceleration from point O, the origin of the reference frame, are written

A0n=vn=ank=1n1Cnkωnkak,nNE110

The invert of previous equation is written:

an=Pnv,nNE111

where Pn is the polynomial with the coefficients in the ring of the second order Euclidean tensors and the polynomials PnD follow the recurrence equation:

Pn+1=DPn+PnωP0=IE112

it follows successively

P1=ωP2=D+ωP3=D2+ωD+2ω̇+ω2P4=D3+ωD2+3ω̇+ω2D+3ω¨+2ωω̇+3ω̇ω+ω3E113

If we denote T=vω and by Ψn=anΦn, nN, for the case of the velocities, accelerations, jerks and jounces, on obtain (Figure 1):

TṪT¨T¨=I000ωI002ω̇ωI03ω¨3ω̇ωIΨ1Ψ2Ψ3Ψ4E114
Ψ1Ψ2Ψ3Ψ4=I000ωI002ω̇+ω2ωI03ω¨+2ωω̇+3ω̇ω+ω33ω̇+ω2ωITṪT¨T...E115
Tn1=Ψnk=1n1Cn1kωn1kΨk
Ψn=PnT,nNE116

Theorem 10. Thenthorder accelerations field of a rigid body in a general motion is uniquely determined by thekthorder time derivative of a dual twistω¯, k=0,n1¯.

## 7. Higher-order kinematics of spatial chain using dual Lie algebra

Consider a spatial kinematic chain of the bodies Ck,k=0,m¯ where the relative motion of the rigid body Ck with respect to Ck1 is given by the proper orthogonal tensor R¯k1kSO¯3R. The relative motion properties of the body Cm with respect to C0 are described by the orthogonal dual tensor (Figure 2):

R¯=R¯10·R¯21R¯mm1E117

Instantaneous dual angular velocity (dual twist) of the rigid body in relation to the reference frame it will be given by the equation

ω¯m0=vectṘ¯R¯TE118

It follows from (110) and (111) that:

ω¯m0=Ω¯1+R10Ω¯2++R10·R21Rm1m2Ω¯mE119

where

Ω¯k=vectR¯̇kk1R¯kTk1E120

Using the denotation

ω¯k=R¯10·R¯21R¯k1k2Ω¯kE121

Eq. (118) will be written

ω¯m0=ω¯1+ω¯2++ω¯mE122

where ω¯k is the dual twist of the relative motion of the body Ck in relation to the body Ck1 observed from the body C0.

Remark 7. Form=2,ω¯20=ω¯1+ω¯2, we will obtain the space replica of Aronhold-Kennedy Theorem: the instantaneous screw axis for the three relative rigid body motions has in every moment a common perpendicular, at any given time. The common perpendicular is line that corresponds to the dual vectorω¯1×ω¯2.

To determine the field of the nth order accelerations of a rigid body Cm we have to determine the ω¯mn0, nN.

We denote ω¯pn=R¯10R¯21R¯p1p2Ω¯pn the nth order derivative of the relative dual twist Ω¯p, resolved in the body frame of C0.

In order to determine the nth order accelerations field of a rigid body Cm, we have to determine the ω¯mn0, nN.

To compute ω¯0mn,nN we will use the following

Lemma: Ifω¯p=R¯Ω¯pwithR¯SO¯3Randω¯p,Ω¯pV¯3R, then

ω¯pn=pnω¯ω¯p,p=1,n¯E123

wherepnω¯are polynomials of the differential operatorD=ddt, with coefficients in the non-commutative ring of Euclidian dual tensors.

pnω¯=k=0nCnkΦ¯nkDk,E124

whereCnkis the binomial coefficient, Dkωp=ωpkandΦ¯pare dual tensors

Φ¯p=R¯pR¯T,R¯SO¯3R,p=0,n¯,E125

Φ¯p+1=Φ̇¯p+Φ¯pω¯Φ¯0=I¯pN.E126

Theorem 11. The following equation takes place

ω¯mn0=ω¯1n+pnω¯1ω¯2+pnω¯1+ω¯2ω¯3++pnω¯1+ω¯2++ω¯m1ω¯m;nNE127

wherepnωare polynomials of the derivative operatorD=ddt, with coefficients in the non-commutative ring of Euclidian dual tensors

pnω¯=k=0nCnkΦ¯nkDkE128

whereCnkis the binomial coefficient, Dkω¯p=ω¯pk and Φ¯pare dual tensors

Φ¯p=R¯p·R¯T,R¯SO¯3R,p=0,n¯E129

Φ¯p+1=Φ̇¯p+Φ¯pω¯Φ¯0=I¯pN.E130

Other equivalent forms of Eq. (127) are the following recursive formulas (Figures 3 and 4):

ω¯mn=ω¯1n+pnω¯10ω¯2+pnω¯20ω¯3++pnω¯m10ω¯m,nNE131

The previous equations are valid in the most general situation where there are no kinematic links between the rigid bodies C1,C2,,Cm.

The following identity can be proved:

Φ¯kω¯1+ω¯2++ω¯p1=k1+k2++kp1=kCnk1,,kp1Φ¯k1ω¯1Φ¯k2ω¯2Φ¯kp1(ω¯p1)E132

where Cnk1,,kp1=n!k1!kp1! is the multinomial coefficient.

From Eq. (131), on obtain the closed form non-recursive coordinate-free formula:

ω¯mn0=ω¯1n+ω¯2n++ω¯mn+
+p=2mk=1nCnkk1++kp1=kCnk1,,kp1Φ¯k1ω¯1Φ¯kp1(ω¯p1)ω¯pnk,E133

where

Φ¯0ω¯=I¯Φ¯1ω¯=ω¯E134
Φ¯2ω¯=ω¯1+ω¯2
Φ¯3ω¯=ω¯2+ω¯ω¯1+2ω¯1ω¯+ω¯3
Φ¯4ω¯=ω¯3+ω¯ω¯2+3ω¯1+ω¯2ω¯1+3ω¯2ω¯+3ω¯1ω¯2+2ω¯ω¯1ω¯+ω¯4

Φ¯nω=Pnω¯,nNE135

## 8. Higher-order kinematics for general 2C manipulator

We’ll apply the general results obtained in the previous chapter for the particular case of four degrees of freedom 2C general manipulator. In this case the relative motions of three bodies C0,C1,C2 are given, the spatial motion of the terminal body C2 been described by dual orthogonal tensor as it follows:

R¯20=R¯10R¯21E136

where

R¯10=eα¯1tu¯10E137
R¯21=eα¯2tu¯21E138

In Eqs. (138) and (139), the dual angles α¯1t and α¯2t are four times differentiable functions, and unit dual vectors u¯10 and u¯21 being constant. To simplify the writing, we will denote:

u¯10=·u¯1E139
u¯20=I+sinα¯1u1+1cosα¯1u1200u¯21=·u¯2E140
ω¯1=α̇1t+εḋ1tE141
ω¯2=α̇2t+εḋ2tE142

According to the observations from Section 6, the vector field of the velocity, the acceleration, the jerk, the jounce is uniquely determined by the dual vectors ω¯,ω̇¯,ω¨¯,ω...¯. Taking into account Eq. (133), we will have:

ω¯=ω¯1u¯1+ω¯2u¯2E143
ω̇¯=ω̇¯1u¯1+ω̇¯2u¯2+ω¯1ω¯2u¯1×u¯2E144
ω¨¯=ω¨¯1u¯1+ω¨¯2u¯2+2ω¯1ω̇¯2+ω̇¯1ω¯2u¯1×u¯2+ω¯12ω¯2u¯1×u¯1×u¯2E145
ω...¯=ω...¯1u¯1+ω...¯2u¯2+ω¨¯1ω¯2+3ω̇¯1ω̇¯2+3ω¯1ω¨¯2ω¯13ω¯2u¯1×u¯2+3ω¯12ω¯̇2+ω̇¯1ω¯1ω¯2u¯1×u¯1×u¯2E146
ω...¯=ω...¯1+3ω¯12ω̇¯2+ω̇¯1ω¯1ω¯2u¯1·u¯2u¯1+ω...¯23ω¯12ω̇¯2+ω̇¯1ω¯1ω¯2u¯2+ω¨¯1ω¯2+3ω̇¯1ω̇¯2+3ω¯1ω¨¯2ω¯13ω¯2u¯1×u¯2E147

Similarly, the results for six degrees of freedom general 3 C manipulator can be obtained, the calculus being a little longer.

## 9. Conclusions

The higher-order kinematics properties of rigid body in general motion had been deeply studied. Using the isomorphism between the Lie group of the rigid displacements SE3 and the Lie group of the orthogonal dual tensors SO¯3, a general method for the study of the field of arbitrary higher-order accelerations is described. It is proved that all information regarding the properties of the distribution of high-order accelerations are contained in the n-th order derivatives of the dual twist of the rigid body. These derivatives belong to the Lie algebra associated to the Lie group SO¯3.

For the case of the spatial relative kinematics, equations that allow the determination of the n-th order field accelerations are given, using a Brockett-like formulas specific to the dual algebra. In particular cases the properties for velocity, acceleration, jerk, hyper-jerk (jounce) fields are given.

The obtained results interest the theoretical kinematics, jerk and jounce analysis in the case of parallel manipulations, control theory and multibody kinematics.

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Written By

Daniel Condurache

Submitted: September 28th, 2019 Reviewed: February 16th, 2020 Published: March 21st, 2020