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E-2 Vehicle Control Module (VCM)

The Vehicle Control Module manages all engineering, system health and navigation functions onboard the E-2. It is also responsible for maintaining the EDL (Engineering Data Log) and interfacing between the SCM and SATCOM.

The VCM is based around an Atmel ATMega32L microcontroller, and is powered from the main 24V battery bus. The processor and core logic functions run at 5V provided by an on-board switching power supply. This supply, and the VCM main processor, are operational at all times. When the VCM is not actively carrying out a mission task, current drain is budgeted at 100mA (processor active current + logic maintenance current, sensors and actuators powered down as far as possible). Tests of the VCM design to date indicate that the actual current requirements in this configuration are presently well under budget, being approximately 40mA at the time of writing.

Collectively, the VCM consists of a processor/logic board and various analog and digital sensors and actuators; MEMS accelerometers, pressure and temperature sensors, optical and mechanical switches, stepper motors driven through Darlington drivers, and brushless DC motors driven by H-bridges.

In the Phase 1 design, the VCM had a separate backup battery supply. This has been eliminated in Phase 2 in favor of an increased main battery capability. The rationale for this is that without main bus power, there is nothing the VCM can do and hence no reason to keep the VCM alive beyond the capability of the vehicle motility hardware.

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