Status of the DB Quad adjustable support design – flexures and regulation units tests

2012.03.21, CLIC Test Module Meeting

Status of the DB Quad adjustable support design – flexures and

regulation units tests

Mateusz Sosin

CLIC Module WG Meeting, 18-September-2013

Mateusz Sosin Concept of ‘hexapod type’ DB Quad adjustable support

DB Quad adjustable support – short review

5DOF regulation thanks to flexure based supports 3 adjustable in vertical 2 adjustable in horizontal + 1 support with

constant length

Mateusz Sosin Status of the DB Quad adjustable support design – flexres nad regulation units tests


Wedge based regulation 30mm of wedge move = 2mm

of ‚leg’ stroke Expected resolution ~2µm Expected precision

(considering thread backlash) ~5µm

DB Quad adjustable support – vertical regulation unit

Flexural vertical support with wedge-profiled head

Threaded wedge

Flexural vertical support sliding bearing

Wedge sliding bearing

Belleville spring stack Regulation screw

Regulation screwbearing unit

(2 flat needle bearings+ tightening screw)



DB Quad adjustable support – radial regulation unit

Differential threadregulation screw

Flexural horizontal support.One end threaded

(as a part of regulation screw)DB Quad platform clamping block

Differential thread based regulation 20 revolution of screw = 2mm of

horiz.support stroke Expected resolution ~2µm Expected precision (considering

thread backlash) ~10µm



DB Quad adjustable support – longitudinal joint

Flexure based joint Blocks longitudinal displacements

of the DBQ platform Allows vertical and horizontal

displacements + rotations (within assumed range)



DB Quad adjustable support – flexures and regulation units tests

Development STEP 1: Adjustable - vertical regulation unit tests Adjustable – radial regulation unit tests Longitudinal „blocking” flexure tests


Development STEP 2: Final design and of 5DOF platform prototype Tests with ‚dummy’ DB Quad Development STEP 3: Update of design according to the STEP1,2 tests results Final DBQ series for CLEX


FLEXURES AND REGULATION UNITS TEST ADAPTER

Test bench desscription

Existing ZTS linear actuators test bench used Additional adapters desighed to provide flexures

and regulation units tests Flexures bending by transversal table Suited LabView acquisition data logging software

written



Vertical regulation unit tests



Vertical regulation unit tests - stiffness

Measurement conditions Load up to 55kg (20%

more than max flexure load)

4 series with step ~10kg

Elongation measured by 50nm resolution RENISHAW linear scale

Stiffness of test bench components considered as negligible


Stiffness → ~5kg/µm


Vertical regulation unit tests - resolution

Measurement conditions Manual adjustment using imbus

key Measurements in the middle and

25% wedge position Load ~47kg Observation of regulation

ergonomy wrt. resulting position change

Results 1µm regulation resolution

achieved without any problems. Fine position adjustment within 2..5 seconds

0.1µm regulation resolution feasible with longer regulation time



Vertical regulation unit tests – linearity, backlash repeatability

FW

BW

Theoretical position

Measurement conditions 3 iterations FW-

BW Load ~47kg Wegde pos.

Measured directly by SYLVAC (1µm resolution) probe

Results Repeatability

~5..7µm Non-linearity

~10µm Backlash ~15µm

Note: Observed „dead-zone” of SYLVAC proble at the level of ~3µm, so real repeataility should be better than mentioned above

RE

PE

AT

AB

ILIT

Y



Vertical regulation unit tests – impact of wegde bending for unit adjustment

Results +/- 1mm perpendicular deflection of flexure gives max. 8µm of longitudinal displacement. It is

coherent with theoretical calculation for flexure geometry

+/-1mm (deflection)

Δl

Measurement conditions 2 deflection iterations FW-

BW Load ~47kg deflection measured directly

by SYLVAC (1µm resolution) probe, regulated by hand



Vertical regulation unit tests - summary

Results Parameters of vertical regulation unit much better than

expected (especially resolution and regulation ergonomy) Position stable in the time Assumed components tolerances and sliding bearings

tolerances (H6/h5, minimal or no sliding bering perpendicular backlash)are correct.

Actions foreseen Add grease grooves in V_FLEXURE_BEARING Integrate wedge absolute position indicators/sensors –

needed for ergonomic regulation. Potentiometric sensors forseen



Radial regulation unit tests



Radial regulation unit tests - stiffness

Measurement conditions Load up to 55kg (20%

more than max flexure load assumed)




Stiffness → ~2.5kg/µm



Radial regulation unit tests - resolution

Measurement conditions Manual adjustment using imbus

key Measurements in the middle

and 25% wedge position Load ~39kg Observation of regulation

ergonomy wrt. resulting position change

Results 3µm regulation resolution easily

achieved. Fine position adjustment within 2..5 seconds

1µm regulation resolution feasible with longer regulation time



Measurement conditions 3 iterations FW-BW Load ~39kg Rotation measured by

encoder adapted to the regulation key:

Results Repeatability

~15..20µm Non-Linearity ~10µm Backlash ~45µm

Note: ENCODER-REGULATION SCREW connection had a big backlash and wasn’t stiff – what could be the source of analysis error. Real performance shall be better than measured. Will be checked during DBQ support platform tests, using integrated sensors

FW

BW

Theoretical positionR

EP

EA

TA

BIL

ITY


Radial regulation unit tests – linearity, backlash repeatability


Aadial regulation unit tests – impact of wegde bending for unit adjustment

Results +/- 1mm perpendicular deflection of flexure gives max. 5µm of longitudinal displacement. It is

coherent with theoretical calculation for flexure geometry

+/-1mm (deflection)

Δl

Measurement conditions 2 deflection iterations FW-

BW Load ~39kg deflection measured directly

by SYLVAC (1µm resolution) probe, regulated by hand



Radial regulation unit tests - summary

Results Resolution satisfactory. Repeatability and linearity to be

confirmed with additional sensors Regulated position stable in the time

Actions foreseen Need to increase the threads tolerances. More tight thread

fitting. Smaller Ra needed to avoid thread seizure. Grinding of threads on steel components. Threads sets fitting during manufacturing

Prestress of the flexures to suppress thread backlash Integrate differential screw absolute position

indicators/sensors – needed for ergonomic regulation. Potentiometric sensors forseen



Longitudinal flexure tests



Longitudinal flexure tests – stiffness, buckling

Measurement conditions Load up to 85kg (stress

in flexure ‚thin’ section ~270MPa)




Stiffness → ~1.4kg/µm No buckling appear

during flexure pressing (even when exciting flexure center with perpendicular force ~10N)



Results Position given by flexure stable in the time Observed position drift, when deforming flexure from

extreme to extereme transversal position (-1mm...+1mm) at load of 50kg. Possible linked with plastic deformation in bending area. Simulated max. stress ~1100MPa (close to elasticity limit of spring steel defined as flexure material 1.0909 Re=1400MPa)

Actions foreseen Optimize shape to decrease stress in bending areas (higher

stress safety margin) Check possibility of better material use Confirm if delivered flexures material correspond to specified

Longitudinal regulation unit tests - summary



Actions foreseen – STEP2/STEP3


Integrate wedges position sensors within vertical regulation units

Increase the threads tolerances. More tight thread fitting. Smaller thread surface Ra

Integrate differential screw absolute position sensors/indicators

Optimize flexure shape to minimize stress in bended areas


CLEX integration – remarks

Single actuator rotation (90 or 180˚) needed According to the collision

between one flexure support and actuator connector box – the rotation of actuator is needed

Considered as non conflicting with other installations (to confirm)


Documents

Status of the DB Quad adjustable support design – flexures and regulation units tests