slidesrobcin
TRANSCRIPT
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Robtica
Cinemtica Directa
+Cinemtica Inversa
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Definitions Kinematics
the science of motion which treatmotions without regard to the forcesthat cause them
It is restricted to a pure geometricaldescription of motion by means of
position, orientation, velocity, andacceleration.
Forces and torques causing themotion are not considered.
The most important application oftechnical kinematics is in roboticsand gearing design.
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Problema
From the geometrical caractheristics of the
robot the position and orientation of thegripper are obtained
Coordinate system or Frames are attachedto the manipulator and objects in the
environment following the Denenvit -Hartenberg notation.
Robotic Kinematics The study of the motion of robots Robot kinematics deals with aspects of
Redundancy Collision avoidance Singularity avoidance
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Cinemtica
Representation schemes Coordenadas juntas (joint space)
Coordenadas mundo (world space) Forward kinematics
Inverse kinematics Homogeneous transformation
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Coordenadas Junta e Mundo
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Cinemtica Directa
Qual o problema? Sabe-se que o brao iniciou-se
alinhado com o eixo x Se o eixo 1 rodar1 e o 2 2,
qual a posio da ponta do braoem relao ao referencial base?
2 solues Geomtrica
Fcil no caso da figura mas podeser bastante mais complexa sehouver mais eixos
Algbrica Involve transformaes de
coordenadas
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Links
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Cinemtica Directa
x, y, z represents the position ofthe TCP related to the base frame
, , represents the orientation ofthe TCP related to the base frame
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Cinemtica Directa
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Transformadas Homogneas A serial link manipulator is a series of links that
connect the hand to the base, with each linkconnected to the next by an actuated joint.
If a coordinate frame is attached to each link, therelationship between two links can be describedwith a homogeneous transformation matrix T.
The first T matrix relates the first link to the baseframe, and the last T matrix relates the hand frameto the last link.
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Transformadas Homogneas The general homogeneous transformation is used to
describe mathematically the position and orientation (pose)of a frame in space relative to another frame.
It is represented by a 4x4 matrix with a 3x3 orientationsubmatrix and a positional vector.
The first three columns represent the direction cosines ofthe secondary frame relative to the base frame. The lastvector locates the secondary origin.
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X2X3Y2
Y3
1
2
3
1
2 3
Suponha o seguinte brao com 3 links que comea alinhado com o eixo x. Cada link
tem comprimento l1, l2, l3, respectivamente. Supondo que o primeiro link roda 1 , , osegundo 2 e o terceiro 3, calcule a matriz transformada que permite calcular o pontoamarelo em relao ao referencial X0Y0.
H = Rz(1 ) * Tx1(l1) *Rz(2 ) * Tx2(l2) *Rz(3 )Rodando o referencial X0Y0 de 1, obtm-se o referencialX1Y1.
Translada-se ao longo de X1porl1.Roda-se 2 e obtm-se o referencial X2Y2.Repete-se o procedimento at chegar a X3Y3.
A posio do ponto amarelo em relao ao referencial X3Y3 (l1, 0). Se se mulltiplicar H por esse vector obtm-se ascoordenadas do ponto amarelo em relao ao referencial X0Y0.
X1
Y1
X0
Y0
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Neste caso o ponto amarelo passa a ser a origem de um novo referencialX4Y4 frame
X2X
3
Y2
Y3
1
2
3
1
2 3
X1
Y1
X0
Y0
X4
Y4
H = Rz(1 ) * Tx1(l1) *Rz(2 ) * Tx2(l2) *Rz(3 ) * Tx3(l3)
This takes you from the X0Y0 frame to the X4Y4 frame.
The position of the yellow dot relative to the X4Y4 frame
is (0,0).
=
10
0
0
H
1Z
Y
X
Notice that multiplying by the (0,0,0,1) vector will
equal the last column of the H matrix.
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Referenciais Segundo Denavit-Hartenberg
Z(i - 1)
X(i -1)
Y(i -1)
( i - 1)
a(i - 1 )
Z iY i
X i a id i
i
A cada junta atribuda um referencial. Atravs da notao de Denavit-Hartenberg notation, necessita-se apenas de 4 variveis para descrevercomo que um referencial (i) se relaciona com o referencial ( i -1 ).
As variveis: , a , d,
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Referenciais D-H
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D-H
S se considerarem os
pressupostos referidos na figura que se pode dizer que amatriz transformada aindicada
DH 1 x1 perpendicular a z0
DH2 x1 intersecta z0
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Variveis i - rotao do link. ngulo
entre zi-1 e zi em torno de xi
aitamanho do link. Distncia
entre zi-1 e zi ao longo de xi
dioffset do link. Distnciaentre a origem i-1 e ainterseco de xi com zi-1,medida ao longo de z
i-1 i ngulo da junta. ngulo
entre xi-1 e xi medido em torno
de zi-1
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Atribuio dos referenciais O zi est sempre colocado ao longo da junta rotao ou
translaco
A escolha do sentido de zi arbitrria
Zi corresponde sempre junta i+1. Ento z0 est associado junta 1
O frame 0 pode ser arbitrrio com excepo de Z que deve
estar na junta Colocar a origem Oi onde a normal comm entre zi e zi1
intersecta zi. Se zi intersecta zi1 colocar Oi nesta interseco.
Se zi e zi1 so paralelos, colocar Oi em qualquer posioconveniente ao longo de zi Colocar agora xi ao longo da normal comm entre zi1 e zi
atravs de Oi, ou na direco normal ao plano zi1 zi se zi1 e
zi se intersectam Atribuio da coordenada do end-effector (ver slide seguinte)
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End-effector
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A Matriz de Denavit-Hartenberg
An = Rot(z,).Transl(0,0,d).Transl(a,0,0).Rot(x,)
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Rob e Eixos
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PUMA
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PUMA
1= 90 +
1
d1
= 0
a1
= 0
1 = -90
2
= 2
d2
= d2
a2 = a2
2= 0
1
3 = 90 + 3 d
3= 0
a3
= a3
3
= 90
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PUMA
5
= 5
d5
= 0
a5= 0
5= 90
6= 6 d
6= d6
a6
= 0
6
= 0
4
= 4
d4
= d4
a4
= 0
4 = -90
A
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PUMA
PUMA
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PUMA
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R b3
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Rob3
275x
z
R b3
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Rob3
001305
Link 5
90004
Link 4
013003
Link 3
020002
Link 2
9002751
Link 1
ii
dii
001305
Link 5
90004
Link 4
013003
Link 3
020002
Link 2
9002751
Link 1
ii
dii
275
Z0
Y0
X0
Z1
X1
Y1
Z2
X2
Y2
200
Z3
X3X
4
Y3
130
Z4
Z5
X5
130
Z0
Y0
X0
Z1
X1
Y1
Z2
X2
Y2
200
Z3
X3X
4
Y3
130
Z4
Z5
X5
130
R b 3
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Rob 3
+++
++++++
=
1000
275200130130
200130130200130130
22323423452345234
21231234123415152341512341
21212341234151523415152341
05
ssccsscs
cscsssssccscssccsccccscsccssccssccc
T
21212341 200130130 ccccscxP ++=
212312341 200130130 cscsssPy ++=
Pitch = = 2+3+4
Orientao = 5275200130130 223234 +++= sscPz
SCARA
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SCARA
3 Eixos de Revoluo Z3
Y3
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i (i-1) a(i-1) di i
1 0 a0 0 1
2 -90 a1 0 2
3 0 0 d3 0
Z0
X0
Y0
Z1
X3
Y1
Z3
X1
3
d3
a0 a1
Tabela de Parmetros
An =Rot(z,q).Transl(0,0,d).Transl(a,0,0).Rot(x,a)
Y2
X2
Z2
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Exemplo
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Cinemtica Inversa
Picture from Jehee Lee Seoul National University
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Cinemtica Inversa Dadas as coordenadas mundo pretende-se obter coordenadas junta
No so necessrias quando os robs so programados atravs do teach pendant. O Problema principal :
A existncia de solues mltiplas
A possvel no existncia de soluo
Singularidades
As solues so equaes no lineares e no existe um mtodo genrico de asresolver: Closed form solutions Alguns robs no tm este tipo de solues
Algbricas
Geometricas
Numerical methods, iterative procedures Demora tempo
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Cinemtica Inversa
Ci i I
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Cinemtica Inversa
Ci ti I
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Cinemtica Inversa
R b3 I
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Rob3 - Inversa
x
P = (px,py)y
1
=x
y
p
p2atan1
R b3 I
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Rob3 - Inversa
( )sin3 = lPQ zz
432 ++=( )
3
sin
l
QP zz =
2
3
4
X0
Z0
P = Px, Py, Pz
Q = Qx, Qy, Qz
l1 = 200
l2 = 130
l3 = 130
Qz
Pz
Qx and Qy depends not only on but also on 1
PxQx
( )
3
cosl
QP xx =
l3*cos()
R b3 I
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432 ++=
1 X0
P = Px, Py, Pz
Q = Qx, Qy, Qzl2 * cos(2 + 3)
l3 * cos()
Qy
Py
PxQx
Y0
Rob3 - Inversa
)cos(*)cos(* 13 lPQ xx =
( )( )
cos*
cos3
1l
QP xx =
( )( )
cos*
sin3
1l
QP yy =
l1 * cos(2)
1
)sin(*)cos(* 13 lPQ yy =
R b3 I
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Rob3 - Inversa
2
3
X0
Z0
Q = Qx, Qy, Qz
l1 = 200l2 = 130
Qz
Qx
Qx = l1cos(2)+l2cos(2+3)
Qz = l1sin(2)+l2sin(2+3)
180+3
3
Qx2+ Qz
2= l12+l2
2 2l1l2cos(180+3)
Qx2
+ Qz2
= l12
+l22
+ 2l1l2cos(3)
21
22
21
22
3 **2)cos(
llllQQ zx +=
180+3
R b3 I
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1 X0
Q = Qx, Qy, Qzl2 * cos(2 + 3)
Qy
PxQx
Y0
Rob3 - Inversa
)cos(*)2cos(*)cos(*)2cos(* 13211 ++= llQx
l1 * cos(2)
)sin(*)cos(*)sin(*)cos(* 1322121 ++= llQy
R b 3 I
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Rob 3 - Inversa
)2sin(*)2sin(* 321 ++= llQz
2
3
2= se 2 > 0
2= + se 2 < 0
Qz
r
r2 = Qx2+Qy2+Qz2
Qx2+Qy2+Qz2 = l12+l22+2l1l2cos(3)
Q = Qx2+Qy2+Qz2
21
2
2
2
13 **2)cos( ll llQ =
Rob3 Inversa
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Rob3 - Inversa
2)cos(1
2cos +=
)cos(1
)cos(1
22
+
=
tg
2
)cos(1
2
sin
=
( )( )221
221
3 *2llQ
Qllarctg
+=
2
3
2= se 3 > 0
2= + se 3 < 0
r
rl )sin(*)sin( 32 =
r
ll )cos(*)cos( 321
+=
)cos(*)sin(*)(
321
32
llltg+=
+=
)cos(*
)sin(*
tan 321
321
ll
l
++
+
= )cos(*
)sin(*tantan321
321
22
12
ll
l
QQ
Q
yx
z
+
= 22
1tanyx
z
QQ
Q
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Rob3 - Inversa=2+3+4
4=-2-3
5=Orientao