TSU F.E ANALYSIS YAIR SOFFAIR

Ojective Dynamic Response Calculation Temperature Distribution LOS Retention due to Temperatures Design Recommendations

Model Description TSU Casting and Cover Optical Bench Hood PCB’s Mirror, Flexures, Optical Elements, Masses Bolts and Thermal Resistances

The Optical Module and Mirror Assembly

Loads and Runs Operating (68W) in 52 C Ambient Natural Frequencies 15 g/11msec Shock on 3 Directions 24 g Static Envelope Random Vibrations on 3 Directions

Structural Analysis - Boundary Conditions

Thermal Analysis Boundary Conditions The Ambient Temperature outside was set to 52 C Convection Coefficients were calculculated and entered The Temperatures inside were calculated during the Analysis

Materials Casting - Al 356 Mil-A Class 11 Flexure -Al 7075 T 7351 Flexure PH H 1025 Steel Mirror - RG 715 Adhesive - Ablebond C Lenses - SFL 6 PCB’s - Polymide+Copper layers

Results Natural Frequencies 118 Hz - Supply card Bending 126 Hz - Optical Module Bending 136 Hz - Video card Bending 155 Hz - CPU card Bending 166 Hz - Supply card Bending 189 Hz - Video card Bending 202 Hz - TSU Twisting+legs&CPU Bending 204 Hz - CPU Bending 227 Hz - Optical Module & Flexures Bending

Second Natural Frequency Hz Second Natural Frequency Hz

Seventh Natural Frequency Hz Seventh Natural Frequency Hz

The Maximum Accelerations during 15g/11msec Shock in X direction

The Maximum Accelerations during 15g/11msec Shock in Y direction

The Maximum Accelerations during 15g/11msec Shock in Z direction

The Accelerations on several components during Z Shock

Maximum Accelerations and Displacements on PCB’s - Z Shock

Checking the PCB’s - Steinberg Criteria during Z Shock The critical PCB is the Supply PCB The Displacement on the critical component is 0.53 mm The allowed Displacement for such component according to Steinberg criteria is 1.41 mm

The displacements on Supply while subjected to 24g static load - Z

The Maximum Stresses during 24g static envelope - X direction

The Maximum Stresses during 24g static envelope - Y direction

Principal Stresses on the Mirror, 24g static envelope, Y direction

The Maximum Stresses during 24g static envelope - Z direction

Von Mises Stresses on the Optical Module, 24g static, Z direction

Von Mises Stresses on the Al Flexure, 24g static envelope, Z direction

Design Improvements Adhesive thickness is increased to 0.35 mm. Three flexures and two ribs were added to the Optical Module in order to increase the second natural frequency and reduce the gains. The Mirror thickness was reduced from 13 mm to 11 mm.

The new bonding configuration

The Maximum Stresses during 17g static envelope - Z direction

Tensile Stresses on the Adhesive, 17g static envelope, Z direction

Random Endurance Vibration X

Random Endurance Vibration Y

Random Endurance Vibration Z

The RMS Accelerations during Random Vibration, X direction

The RMS Stresses during Random Vibration - X direction

The RMS Accelerations during Random Vibration, Y direction

The RMS Stresses during Random Vibration - Y direction

The RMS Accelerations during Random Vibration, Z direction

RMS Accelerations & Displacements on PCB’s (1  ), Z (C/Ccr=2%)

The RMS Stresses during Random Vibration - Z direction

Checking the PCB’s - Steinberg Criteria during Z Vibration The critical PCB is the CPU Total life time : 5.5 hours M.S=2.74 The PCB’s free edges must be captured and bonding of the critical components to the board is recommended

Thermal Analysis - 52 C Ambient Main parts temperature distribution

The inside Temperatures PCB area : 69.5 C R area : 60.6 C Hood inside air : 61.2 C

L.O.S Retention - operation in -30  C (CRT contact angle 38  )

L.O.S Retention - operation in 52  C (CRT contact angle 38  )

Temperature distribution on the optical Module

Temperature distribution on the CPU

Discussion and Recommendations There is no stress problem. The critical dynamic case is Z shock. The critical parts are : Al Flexure, the Adhesive and the Mirror. The critical PCB, Z shock : Supply. M.S=2.66 The critical PCB, Z vibration : CPU.

Discussion and Recommendations M.S=2.74 free edges should be captured and bonding of the critical components to the board is recommended. L.O.S Retention during operating in 52 C is very good in elevation even while adding the R error.

Discussion and Recommendations In azimuth, the error is strongly dependent on the contact angle between the CRT and the Optical Module. In order to minimize this error, the contact angle is set to 40°. L.O.S error during operation in -30°C is larger, but within the allowed tolerance.

Discussion and Recommendations significant improvement can be made by Temperature or electrical calibration. The critical PCB’s : Video & Supply. Gap filler (T-form 460) is added to the Video hot components in order to transfer heat to the H.S. Gap filler is recommended to connect the PCB hot component to the Main Housing.

Discussion and Recommendations Sinusoidal scanning of the Optical module alone (3 flexures) showed first natural frequency of 150 Hz. Thermal experiment of the system operating at 52°C showed temperatures of 71°C on the CRT interface and mid wall. Analysis showed 69°C, 68°C respectively.