You have seen how quickly and accurately the SST produces torque after it calculates the required amount—this is the Torque Response Time. Now let’s examine the Total Servo Phase Delay-the total time from the moment the position feedback is read to the time that torque begins to be updated.
Total Servo Phase Delay (TSPD) is not only dependent upon the time it takes for each individual step in the servo process to be completed, but it is also influenced by the degree of synchronization of these steps. If elements of the system operate asynchronously, as is the case with the traditional servo architecture (where one or more servo loops are closed by the controller and the remainder by the amplifier), this lack of synchronization will cause uncertainties which, on average, will drastically increase the TSPD.
WorldServo chose a step and direction input architecture not only for noise immunity and as a convenience for upgrading from stepper motor systems, but because this allowed us to close all the servo loops with one processor. This eliminated all of the delays and uncertainties associated with the asynchronism of the traditional architecture. This is a big advantage of any skillfully implemented step and direction servo.
WorldServo went several steps further to reduce TSPD. We dedicated a DSP to each axis, designed a true digital torque controller and developed proprietary algorithms optimized specifically for reducing TSPD. The result of these efforts can be seen in the figures below. Low TSPD, combined with improved Torque Response Time, strengthens the weak links found in other servos and results in state-of-the-art servo bandwidth.