Variator pressure-set torque control

A method of generating a torque-pressure curve for a hydraulic transmission including a hydraulic pump and a hydraulic motor driven by the hydraulic pump via a pump port plate having a port plate angle, the variator further including a pressure-driven actuator for controlling a displacement of the hydraulic pump, the actuator having one or more springs biased to center the actuator, the method comprising:

• selecting a port plate angle for the pump port plate and selecting one or more respective spring rates for the one or more actuator springs so as to maximize output torque resolution of the hydraulic motor with respect to actuator pressure changes while allowing the motor to reach maximum available torque without the transmission exceeding a predetermined motor speed limit and actuator pressure limits;
• and
• applying a plurality of actuator pressures at a plurality of motor speeds and pump speeds to generate a respective plurality of motor torques, and recording the respective plurality of motor torques in association with the applied actuator pressures, motor speeds and pump speeds to create a torque-pressure curve for the transmission.