HIGH RESOLUTION MICROROBOTS WITH FLEXIBLE JOINTS

Fig.1
Deformed forms of elementary joint

Rigidity

For elementary beam there are two groups of DOF with different rigidities:
'rigid' (DOF:1,2,3,4) and 'compliant'(DOF:5,6).

Deformability

Maximal deformation (rotation angle) =
function1(properties of the material)
function2(geomentry of the joint)
function3(loading scheme)

Fig.2
Substitution of elastic joint by an elementary beam

The width of equivalent beam is: a*/a=function(a/R)>0

Fig.3
3-beam revolute joint with stable center

3-beams revolute structure is one detail made by electro-erroision.

Fig.4
Radial-beam revolute joint

'Elastic bearing' has maximal rotation angle 10 degrees.

Fig.5
Cardan revolute joint (2DOF)

Cardan joint included thin-walled beams is made from one detail.

Fig.5
Cardan revolute joint (2DOF)

Cardan joint included 2 'elastic bearing' is made from one detail.

Fig.6
Revolute joint with compensation of parazit movement

To compensate parasit transmision of the center of rotation 3-beam structure with coincided axis is used as revolute joint.

Fig.7
Actuator for linear translation with 3 piezos

The inch-worm (diameter 22 mm, length 100 mm) gives maximal force 25 kg and resolusion defined by amplifier.

Fig.12a Fig.12b
3DOF moving table and 3DOF revolving ball

Examples of wave piezo-movers (piezo-propulseurs)

Fig.8
3DOF moving table (actuator) with 5 piezos

Parameters of microrobot with elastic frame.

Structure 3DOF
Material steel
Sizes 66*66*26 mm
Weight 240 g
Maximal displasement 0.9 mm 0.9 mm 1.5degree
Deformability index 0.027
Relative stiffness : 1 - 4354 - 2960
Displacement : 0.9 mm 1.05 mm 1.54 mm
Corresponding force : 14N 10N 10N

Fig.9
6DOF microrobot

Assembling of three inch-worms with 3 DOF gives the parrallel structure with 6DOF.

Parameters of microrobot with 6 DOF .

Structure 6DOF (3 inch-worms+3 flexible joints)
Material steel
Sizes 120*66*46 mm
Weight 800 g
Maximal displasement 15 mm 15 mm 8 mm 15degrees 3degrees 15degrees
Deformability index 0.12
Limit force 500 N


Principle
Number of
piezos
Size,
mm
Torgue,
Ncm
Resolution
steps
stick motor
1
d18*40
0.1
2000
step motor
2
d22*50
5
1000
wave motor
4
d26*30
50
2000

Fig.10

Piezomotor with 1 piezo (2 details)

1. Koksharov I.I., Clavel R. Application of flexible joints in microrobots. Preprint of the Computing Center of Russian Academy of Sciences, Krasnoyarsk, 1996, N 6.

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