What is Virtual Torque Sensor?
Using a physical torque sensor at the joint output can be cumbersome and costly. However, dual encoders can be used with model for gearing stiffness/hysteresis to sense torque. The phenomenon is repeatable and both encoders are already present in the assembly. This will just take an algorithm in the motor controller that identifies direction, and encoder difference. A simple test after assembly can pre-calculate the equation constants and characterize the gearing.