Control
Driver control of the Torotrak full-toroidal variator can range from simple fully manual operation, having no control interface with the rest of the vehicle, through to highly integrated electronic control systems that allow the variator’s unique characteristics to reduce engine CO2 emissions.
Manual systems are suited to low-cost tractors or outdoor power products. Typically, the torque provided is proportional to how hard the throttle pedal is pushed. The operator’s own brain provides the processing power to limit the torque to the wheels and, for example, avoid wheelspin which would damage the grass being cut. Vehicle speed is controlled by the variator switching from torque control to ratio control when the throttle is fully depressed; this prevents any further ratio change and maintains the desired ground speed.
More sophisticated microprocessor control of the variator is required for many applications, such as cars, trucks and buses. A local variator controller can communicate with other vehicle controllers via a CAN bus or may be integrated into the overall powertrain controller. Electronic control allows a reduction in emissions by keeping the engine within its optimum operating region for a given torque requirement. The optimisation is imperceptible to the driver and requires no manual input.