Two-Phase Clinical Control & Active Kinesthetic Cueing

The Clinical Philosophy

The clinical design of the Mitti system is built upon two complementary principles in pediatric rehabilitation:

Active Kinesthetic Cueing (BalanceImpulse): The patient does not require a massive, force-transferring exoskeleton on their legs. A minimal mechanical corrective stimulus at the trunk—comparable to the supportive tactile touch of a therapist at the hip during Dynamic Movement Intervention (DMI)—is sufficient to trigger the vestibular system. This eliminates the need for rigid bracing that often leads to harmful joint hyperextension (e.g., Genu recurvatum).
Preventing Habituation: The pediatric nervous system quickly adapts to constant support. To actively train proprioception, the system must act as softly as possible, intervening only when absolutely necessary, unless the patient has reached muscular fatigue.

The control system operates as a finite state machine, dynamically switching between two primary phases based on the patient’s real-time state:

Deadband Logic: As long as the measured tilt angle ($\theta$) is within a tolerance limit of $\pm 5.0^\circ$, the motor torque output is exactly zero.
Corrective Impulse: If the angle exceeds the deadband, a short, defined sawtooth impulse (dithering) is delivered to prompt posture correction.
Refractory Period: Following an impulse, the system disables further actuation for 500 ms, giving the child time to self-correct.

If the real-time Fatigue Monitor detects high exertion (excessive swaying over time), the system shifts into Phase 2:

Zero Deadband: The tolerance zone is removed.
Continuous PD Control: The motors act continuously, regulating the trunk to remain stable at $0^\circ$. The system behaves as a virtual spring with high stiffness, safely supporting the exhausted patient and preventing a fall. Once the patient’s fatigue score recovers, the system seamlessly transitions back to Phase 1.