Present day torque converters use electro hydraulic Management for your lock-up clutch. The hydraulic circuit which locks/unlocks the torque converter clutch is managed making use of hydraulic valves. The valves are actuated straight or indirectly by solenoids. Torque converter equations of movement are governed by Leonhard Euler's eighteenth century turbomachine https://torqueconverterclutch83681.full-design.com/torque-converter-clutch-for-dummies-76378303