All mechanical systems resonate at some frequency to some degree. When a servo system is connected to a mechanical system, the resonant behavior of the axis is reflected back into the servo. The effect of this mechanical resonance on settling time and disturbance rejection may be anywhere from insignificant to highly detrimental (long settling times and slow disturbance rejection). If the resonant frequency is deep within the required bandwidth of your system, your only option is to improve the mechanics. If, however, the servo is amplifying a resonance at a frequency above the bandwidth inherently required to execute the type motion you desire (or if you can compromise a bit), the SST servo drive’s all digital torque control and built-in tuning stimulus allows you to tailor the torque response bandwidth to control the resonance excitation. Without this, the settling time and disturbance rejection of a resonant axis can be insufficient for your application. This, coupled with the IMT (Inertia Matching Technology) algorithm, allow improved response on resonant axes when compared to competing servo systems.

Solutions
There are two methods available for controlling resonances in the servo loop. The first method is to use the torque filter built into the IMT (Adaptive Inertia Matching Technology). This limits the high frequency energy that can be imparted to the closed-loop vector torque controller from the position/velocity compensator, so that gains can be kept high without exciting resonances.
The second method, which is available because the SST servo drive’s DSP ASIC is in control of the torque, is to change the torque loop gains to customize the frequency response of the torque loop in order to keep the mechanics from being excited even when the gains are high.
Both of these methods work well in reducing the effect of mechanical resonances. This allows you to reduce costs by using mechanics that are less stiff and/or eliminate assembly hassles and weight of using elastomeric damping material within the moving structures. This is important in stepper motor retrofit applications where mechanics, by in large, can’t be changed. It also reduces costs and enhances your design flexibility in new designs when you don’t need the utmost in performance.

Other SSt Feaures to the Rescue
In situations where significant resonance exists in the mechanics, the use of these resonance control methods, combined with Adaptive Inertia Matching Technology (IMT), will drastically improve tracking accuracy and reduce settling time.
Resonance control along with Anti-Hunt™ is also used to limit annoying intermittent servo whine (caused by marginal high frequency instability) that may occur in an axis that otherwise operates well. This will reduce acoustical noise and motor loading while increasing the perceived quality of motion.