James Bond gets a sinking feeling for motion control

11 July, 2007

The structures, however, had to be controlled extremely precisely to enable carefully choreographed stunts and action sequences to be filmed. A solution was needed to ensure the smooth and safe operation of the huge rig that had to sink one of three motion bases, the largest weighing 80,000kg, into the water tanks at Pinewood Studios.

For this, special effects supervisor Chris Courbould and his team built the structures then called in EMP Designs to develop the control systems.

The equipment designed to control the rig centred on the M3000 system – a Moog servo controller (MSC) and the Axis Control software (MACS). It was used to control six digital Moog Axis Control Valves (AVC) which, in turn, operated six hydraulic actuators.

Feedback of the actuator position was achieved using a number of SICK|Stegmann BTF wire-driven encoders.

Dan Stanton at EMP Designs said: “The digital approach offered us finer control and it gave us more confidence when it came to safety aspects as, if anything were to get disconnected or the control was lost, we knew about it as it gets detected immediately. Much of the actuation was also performed in pairs so digital also gave us far greater control in this respect. Another vital consideration was the amount of RF that exists on film sets, and given the long cable lengths digital is far more resilient.”

In this application, the MSC controller used a CAN link to connect to six Axis Control Valves, each of which controlled a cylinder. Working in pairs, this gave three axes of motion. The ACVs then used a CANOpen link to connect to the BTF encoders, producing digital code for every 0.025mm of travel and providing the precise feedback required for each cylinder position. The valves provided remote closed-loop position control for each degree of motion, reducing the processing load on the MSC and allowing it to take care of the safety monitoring and synchronisation. The MSC provided all the profile generation for the ACVs over the CAN bus.

The Moog M3000 offered a stable, flexible control structure, as well as the capability to integrate a 15in touch screen to give a complete simplistic overview of the system using MACS, while offering clear visualisations.

Another benefit was that it allowed the system to self diagnose. Stanton said: “We were able to create routines that would highlight any discrepancies or anomalies. This was the first time we had ever used a controller that helped us make the decision of whether to press the ‘big red stop button’: if anything deviated it was able to assess the severity and then make a decision based on this figure – it took a lot of the worry out of it for us. The controller incorporated a ‘Watchdog’ which reverted to a safe state should any issues arise with the controller.”

There are currently a number of big movies in production which are also using this technology.