STEERING SYSTEM CONTROL LOADING

A constant challenge in driving simulators is: how do you provide steering that "feels right" for a virtual car? The problem is non-trivial. In the real world, when you turn the steering wheel, the steering wheel pushes back! The force it exerts on your hands is proportional to the amount turned, the current vehicle speed, and other factors such as the hydraulic gain of the power steering unit (if present).

Spring or rubber band-based systems are unconvincing, since the force feedback they provide varies only with displacement, and they cannot simulate the hard stops in a real steering system. Users inevitably complain that the steering "just doesn't feel right ..."

Enter the SmartNode Steering System.

The SmartNode Steering System is a self-contained, embedded, controller and torque motor combination that provides force feedback to a driving simulator's steering wheel. As the wheel is turned, it exerts a force on the driver's hands that varies realistically with vehicle speed. When the (configurable!) stop positions are reached, the user will swear they are hitting a mechanical hard stop; but it's actually the SmartNode controller pushing back to prevent him from exceeding the stop displacement.

The SmartNode Steering System communicates with the simulation Host over Ethernet using a simple packet-based protocol. The Host merely provides the current vehicle speed, and the SmartNode sends back the steering wheel angle and torque. Because the torque control is handled locally on the SmartNode unit — which has an extremely high iteration rate — the Host is able to send data at a "comfortable" pace (30 to 100 Hz is typical), and let the steering controller worry about the messy details of providing force feedback to the wheel.

The controller is capable of running models of specific steering systems, or a parametric effects model. Configurable model parameters include:

• Linear or non-linear spring torque
• Centering torque (modified by vehicle speed and heading)
• Damping torque
• Friction (modified by vehicle speed)
• Velocity limit
• Variable hydraulic assist / loss of hydraulic assist
• Simulated hard stop positions
• Impulse forces (e.g., curb hit)

The realism provided by the SmartNode Steering System will boost the effectiveness of your driving simulation, whatever your goals may be. Instead of focusing on steering that "doesn't feel right", your users will be able to concentrate on the tasks you set for them.

Contact us for a brochure today.