Controller Lends Touch of Reality to Simulator

It's one thing to operate a car, but an entirely different challenge to maneuver a 365-ton- capacity crane with a 400-foot boom for building bridges and skyscrapers. To make sure that operators are up to the task, employers often rely on simulators, such as those manufactured by GlobalSim(TM), Salt Lake City, UT.

Designed for training heavy equipment crane operators in such industries as construction, maritime, industrial and offshore, GlobalSim's MasterLift(TM) provides a virtual environment that accurately replicates the physical and operating characteristics of a crane. Now, operators can learn from their mistakes in the safety of a simulator. That's a big step forward from earlier days, when operators learned on the job in multi-million dollar cranes, risking the chance of severely damaging equipment and surroundings or, even worse, causing potentially fatal injuries.

MasterLift, featuring an enclosed cab with commercial seat and controls, incorporates an integrated electromechanical motion system, a high-fidelity graphical display system, surround sound and much more.

"It was absolutely vital to create a simulator in which operators see, feel and respond in real time to whatever they might experience in a real crane," says Jonathan McCurdy, senior systems engineer at GlobalSim.

The crane simulator can re-create various loads, such as I-beams and crates, as well as different terrains, pedestrian and vehicle traffic, and other safety hazards and distractions an operator might experience. Through proprietary software programs, it even mimics different crane models, including those used on ships, docks or in railway terminals.

To create realistic, precise motion in the simulator, the seat that is encased in the cab of the base unit of the MasterLift model 4000 is attached to a motion base controlled by a DMC-1240 4-axis motion controller from Galil Motion Control, Rocklin, CA.

The DMC-1240 controller directs large 20-amp, 300-V motors along four axes: XYZ and W. These motors each weigh about 50 lb.With a command from the controller, the operator cab moves backward and forward, from side to side, with pitch and yaw. The operator can use a throttle lever to select which part of the crane he is controlling, just as in a real crane.

When the trainee moves the crane, he sees its "boom" or swing arm. Attached to the boom is the steel cable that holds the load. As the trainee moves the boom around, he must keep the load from swinging wildly. "This takes skill," adds McCurdy. "He must learn to 'catch the swing' to keep the cable and the load from swinging into everything in sight."

The controller's jog mode provides a real-time sensation of acceleration in the cab. Based on the movement of the joystick, the crane moves, and acceleration is simulated. The host computer determines the G force and sends the appropriate velocity commands to the Galil controller. As the operator drives forward, he is pushed back into the seat. The operator really feels this acceleration. The G force is between 0 and 2 Gs, depending on the crane that is being simulated.

GlobalSim also uses Galil I/O functionality to incorporate safety features, such as safety gates around the simulator and a seatbelt check. Says McCurdy: "The Galil controllers are cost-effective and easy to use. For example, our engineers were able to use a simple C-program to talk to the Galil controller through a FIFO buffer and get good throughput for real-time job commands."

McCurdy notes that a trainee can learn to operate a crane efficiently and safely after completing a two to three-week course using the simulator. On average, a MasterLift simulator sells anywhere from $180,000 to $795,000, depending on the configuration.