System Identification and acados-Based NMPC for Swing-Up Control of an Underactuated Double Pendulum

Abstract

We identify a base-parameter model of CloudPendulum cell 203 and track an offline swing-up reference with acados SQP-RTI NMPC at a target rate of 400 Hz. A 5 mNm passive-joint assist enabled development-stage swing-up and recovery. In organizer-run testing (16 trials of 300 s per configuration on cells 201--204), assisted pendubot and acrobot mean uptime scores were 80.19 s and 74.61 s. Acrobot scored zero on two cells, and seven trials ended on safety-limit exceptions. Because the assist is prohibited in evaluation, these results are diagnostic rather than qualification scores.