TCS3 Electronics

Hazard Analysis and T3 Design

Sources of Hazards

Drive or feedback components: Motor, Amplifier, Tachometer, Encoder

Mechanical: Jammed telescope, Dome, Cooling

Loss of TCS3 Components: Computer, Motor controller, Electronics, Safety Switch

Operator error: Inadvertent movement, Platform or Crane not stowed, Slew speed near end of axis

Potential Hazards 1Hazard Telescope

ConditionTCS3 module(s) responding to

conditionLoss of MotorLoss of Motor AmplifierLoss of one Motor Amplifier Drive SignalLoss of Motor TachometerLoss of Encoder

Runaway Software, T3 over speed circuit, stop and emergency safety switches to software and T3 circuit

Potential Hazards 2Hazard Telescope Condition TCS3 module(s)

responding to condition

Jammed Telescope or dome

Slow or no movement, excessive amplifier current

Software, T3 over current and thermal disable circuit, amplifier thermal disable

Loss of TCS3 computer Runaway or no movement T3 watchdog circuit, over speed circuit, operator intervention

Loss of T3 electronics Loss of fault detection Software, operator intervention

Loss of motor controller card

Runaway or no movement T3 motor control signal, T3 over speed circuit, stop and emergency safety switches to software and T3 circuit

Potential Hazards 3Hazard Telescope Condition TCS3 module(s)

responding to condition

Inadvertent movement of telescope or dome while maintenance is being performed

Personnel safety T3 Keyed Lockout switch signal, software lockout signal

Platform not stowed Platform, telescope damage

Software, operator intervention

Crane not stowed Crane, telescope damage Software, operator intervention

Telescope in slew speed nearing the end of axis

Runaway? Software detection, slew safety switch to software

Response to Hazards

Disabled on Fault Condition: Motor and Dome amplifier drive input System Power Relay Brake Release Relay

Enabling the Telescope Dome Key Switch Enabled Telescope Key Switch Enabled Emergency Stop Button Released External Signals in Safe State TCS3 Computer issues Reset Pulse TCS3 Computer issues System Power

Enable TCS3 issues Brake Release Command

T3 Electronics Overview Tachometer

Adapted from TCS1 Used in Simulink model

Watchdog Timer Monitors TCS3 computer Timeout period is 150ms, can be changed to

600ms Over speed and Over current

Adapted from TCS1 Fault Logic

Implemented with CPLD

Over Speed and Over Current

312

148

9

U4CLM339AN

312

16

7

U5BLM339AN

-15V

+15V

+15V

-15V

-1V

10k

R46

Res1

10M

R49

Res1

1M

R66Res1

1M

R61

Res1

1M

R58

Res11V

Feedback

50k

R55RPot10k

R52

Res1

Fault Logic Overview

9 Safety Switch Inputs Can be overridden with key switch 3 Spares

15 Fault Inputs 5 Spares

Fault is latched TCS3 Computer applies Reset Pulse

Fault Logic

Override_Kswtch

E_Therm_DisW_Therm_DisN_Therm_DisS_Therm_Dis

Dm1_Therm_DisDm2_Therm_DisDm3_Therm_DisEmerg_StopMotor_Cntr_ErrorWatchdog_Timer

Spare4

Spare5Spare6

TCS_Lockout

Dome_Kswtch

I1

I0O

U3

OR2

OverspeedHA_OvercurrentDec_OvercurrentDome_Overcurrent

Horizon_Stop

Dec_Emerg_N

Dec_Stop_N

HA_Stop_EHA_Emerg_W

Spare1Spare2

Spare3

Dome_Enable

Dec_Emerg_S

Dec_Stop_S

HA_Stop_W

HA_Emerg_EO

I0I1I2I3I4I5I6I7I8

U2

AND9

Sys_Pwr_En_In

Brake_En_In

Sys_Pwr_En_Out

Brake_En_Out

OI1

I0

U12

NAND2B1

ResetQD

G

CLR

U8

LDC

U7

VCC

OI1

I0

U10

NAND2B1

O

I7I6I5I4

I3I2I1I0

U4

AND8

I0

I3I2

I1O

U1

AND4

I0I1I2I3

I4I5I6I7

O

U11

NAND8

Spare7Spare8

OI1

I0

U6

NAND2B1

OI1

I0

U5

NAND2B1

Tel_EnableTel_Kswtch

O

I6I5I4I3I2I1I0

U9

AND7

TCS_Enable

Sys_Pwr_En_Rly

Brake_En_RlyO

I1

I0

U?

NAND2B1

TO Panel Overview 24 Indicator LEDs 2 Axis Variable Joystick Dome Enable Key Switch Telescope Enable Key Switch Override Key switch

Overrides Safety Switches for Maintenance Emergency Stop Mushroom Switch Floor Light Switch

TO Panel Rough Layout

slew

stop

zenith Hor

brake slew

stopbrake

slew stop brake

slew stop brake

HA Dec

Slew Stop

N

S

EW

Telescope Enable

Dome Enable

W E

N

S

TCS3 JoystickEmergency

Floor Lights

TCS Enabled

System Power Enabled

Brakes Released

Limitoverride