2.5.2 Main Processor (R3K)

The Heurikon V3500 microprocessor board is the central hub of all of the computer systems in Ranger NBV. This main processor board uses an R3500 CPU running at 40 MHz with 8MB of memory. The computer uses the VX-Works real time operating system. This operating system supports a multitasking environment with shared global communication between processes. All of the high level flight and manipulator control algorithms are executed on the R3K.

Figure 2-19 The Main Processor

The R3K sends and receives commands to the various LPUs throughout the vehicle using a 16 channel RS422 serial communications board. These links include the dexterous manipulators, video manipulator, grapple manipulator, thruster control unit, buoyancy control unit, power management unit, inertial measurement unit, and external sensor unit.
Communications with the control station are carried over a fiber optic ethernet link using the NDDS communications protocol.
The software within the R3K is divided into several modules that each handle specific functions. Each of these executed independently by the VX-Works operating system. The information is passed between these processes by global variables. There are three main types of software module. The first type of module handles communications through the ethernet interface. The information is passed between the ethernet and the vehicle global variables with only minor processing. The second type handles communications to the LPUs over the RS422 serial communications interface. These modules relay information between the serial interface and the vehicle global variables. Only minor processing and simple coordinate transformations are performed by these modules. The final type of module only communicates with other software modules through global variables. In the flight control system, these are the flight control and state estimation modules. The state estimator module takes sensor information along with commands from the control station and forms an estimate of the current vehicle state. The controller and trajectory generator module takes command information from the control station, and vehicle state estimate information and uses them to calculate desired trajectories and thruster commands.
The flight control system software is shown in block diagram below. Each block within the R3K represents an separate software process.

The R3K is located in the forward port side of the electronics module.