Cascaded Acceleration–Velocity Control of a PMDC Motor for Flywheel Energy Storage Systems with Planetary Transmission

Flywheel energy storage systems coupled with planetary transmissions require accurate carrier motion control to support efficient energy exchange and operation with carrier torque close to zero. This paper develops a digital cascaded acceleration and velocity control framework for a permanent magnet DC motor used as the carrier actuator in a planetary-transmission flywheel energy storage system. The controller combines an outer velocity loop, an inner acceleration loop, and a feedforward angular acceleration reference derived from the desired motion profile. Two digital implementation approaches are examined. The first preserves the continuous motor plant and includes A/D conversion, aliasing prevention and D/A reconstruction effects. The second uses a fully discrete acceleration plant for adaptive controller design. Based on this discrete model, two adaptive inner acceleration controllers are developed: adaptive deadbeat control and adaptive pole placement control. Both controllers replace only the inner acceleration PI controller, while the outer velocity loop and the feedforward structure remain unchanged. A normalized gradient estimator with projection updates the discrete plant coefficients online and keeps the estimates within calculated admissible bounds. Scilab/Xcos simulations evaluate the controllers under pulse acceleration disturbance, sinusoidal acceleration disturbance, and segmented reference tracking. The results show that both adaptive controllers reduce angular acceleration and angular velocity tracking errors compared with the digital PI baseline. The adaptive deadbeat controller gives the fastest response, whereas the adaptive pole placement controller provides a tunable compromise between response speed and smoothness.