Torque Limits

The TI2 Torque limits have 3 types of limits. Absolute limit, Dynamic driver torque limit, and rate limit. The limits do not need to account for the speed of the vehicle because a higher driver torque is required to achieve the same steering output at a high speed compared to the output at a low speed. The maximum torque limits were chosen to allow the vehicle to handle most highways and roads. The limits are further reduced when the driver applies force to the wheel to reduce the effort required to overcome the LKAS command.

LKAS offset output is limited by the absolute limit. This value is fixed and does not change. It is also limited by the Dynamic driver torque limit, which changes based on the driver's input torque. This prevents the feeling that the steering wheel is fighting you. There is also a rate limit that prevents a fast change in the LKAS offset. The rate is limited to prevent the vehicle from deviating from a standard lane (3.7 meters) in less than 1.7 seconds when driving straight. These calculations are done on each MCU on the TI2, it is also done in the Panda software and in Openpilot software.