Design and build of an actuated dynamic tether spring system for a pulmonary rehabilitation robotic system

"This thesis investigates whether a low-cost brushed DC motor can be used reliably in an actively controlled dual-reel actuation system despite the thermal and energetic challenges associated with motorization. Three low-complexity measures were implemented: (i) reduced reel actuation, (ii) a two-level standby algorithm that de-energizes the motor when the tether is being pulled out, and (iii) a redesigned machined aluminum case to improve passive heat dissipation. Experiments quantified motor surface temperature and verified that these modifications do not compromise the robot’s following behavior. The results show that both reduced actuation and the standby implementation lower the operating temperature, while the aluminum case provides the strongest single improvement. The combined configuration remains thermally stable under more demanding conditions and meets conservative temperature limits with a substantial margin. Moreover, the changes do not measurably alter control behavior for the tested walking patterns. These actuation mechanisms were developed in the context of a follower robot for pulmonary rehabilitation jointly developed by ALPI and ITBA. In pulmonary rehabilitation for patients with chronic obstructive pulmonary disease, an additional staff member is required solely to carry the patient’s oxygen tank, which increases personnel demands. To reduce this burden, the robot is intended to carry the oxygen tank while automatically accompanying the patient. It estimates the patient’s position from tether measurements and uses this information to follow the patient. Within this system, the tether retrieval mechanism plays a central role. Compared with a spring-driven reel, a motorized reel makes tether behavior software-defined, thereby enabling more flexible tuning of the system response and control behavior while also simplifying installation and maintenance".