Advent of Direct Drive Systems
In some cases these concerns can be adequately addressed by selecting high-quality mechanical transmission components with ultra-precision tolerances. However, the added expense can become prohibitive and the components will still wear eventually. The ultimate solution is a direct drive rotary system,
which eliminates the transmission altogether. In direct drive systems, the motor directly drives the load. The accuracy of a direct drive solution can be up to 60 times better than that of traditional systems and audible noise can fall by more than 20 dB. Other measures such as servo response (bandwidth), machine parts reductions, and reliability also can improve dramatically.
When the load is directly coupled, there is no limitation on the inertia mismatch between load and motor (Provided there is no compliance introduced in the coupling method – see blog post “Reflecting” on Inertia Ratios
). The servo loop gains can now be increased significantly to provide the necessary servo stiffness to achieve excellent speed regulation to optimize product quality.
When the transmission components such as gearboxes, belts, rack and pinion, and pulleys are eliminated, the servo system becomes free of such negative factors as compliance, backlash, and component wear. The accuracy increases, inertia-matching requirements relax, acceleration and deceleration improve, maintenance becomes unnecessary, and the product life increases by a significant degree.