Specifications

Doc Number: VIS-ANA-VER-01001-9002
Date: 27 May 2004
Issue: 5.0
Page: 70 of 80
Author: J. Delgadillo
Controls Preliminary Design Report Issue 5.doc
11. Test Trajectories
Pre-mission test functions are onboard to support full axis known motion conditions. This
allows fully expected performance to be reconfirmed during maintenance of critical mission
event preparation. The following test functions are supported:
• t
2
; Constant acceleration and deceleration to measure the system’s static
Acceleration Error Coefficient (Ka) per axis
• Flyby; Low target flyby of mount location to measure the system’s dynamic
Ka
• Constant Velocity; Measure running friction and position error.
12. Maintenance Mode
When the MCU is put in Maintenance Mode, control is transferred to the Portable
Maintenance Unit (PMU). Once the PMU has accepted control, the MCU (and the LCUs)
cannot take control back until the PMU relinquishes control.
13. LCU Mode
Upon power-up, the MCU will default to LCU mode. When in LCU mode, the AZ, ALT and
CASS LCUs will be able to take control of the system via the manual, mechanical PDU
switch. As with the Maintenance Mode, once the LCUs are in control of the system, the
MCU and the PMU are unable to take control until the LCUs relinquishes control of the
mount. LCUs Relinquishing control of the mount is made via the PDU switch.
If the MCU is in control of the mount and looses communication to the Power Drive Units,
control is automatically offered to both the PMU and to the LCUs. Whichever unit takes
control first will control the mount.
Whenever the unit that has control of the mount looses communication to the appropriate
PDU, the MCS reverts to “STOP” mode, whereas all motor controller enables are taken
away. For the LCUs, loosing communication signifies that the PDU manual switch has been
switched from the “LCU” to the “PMU/MCU” position or the UPS power has cycled.