Robust control of heart rate for cycle ergometer exercise

Area of Science:

• Physiological control systems
• Biomedical engineering
• Exercise physiology

Background:

• Automatic control of physiological parameters like heart rate (HR) is crucial for exercise testing and rehabilitation.
• Existing methods face challenges in managing inherent biological variability, such as heart rate variability (HRV).

Purpose of the Study:

• To evaluate a new strategy for automatic HR control during cycle ergometry.
• To assess the performance, stability, and robustness of this novel control approach.

Main Methods:

• A linear plant model and direct shaping of the closed-loop input-sensitivity function were employed for controller design.
• The controller was tested in 73 feedback control experiments with 49 participants.
• Robustness was analyzed using 73 identified plant models.

Main Results:

• The controller demonstrated highly accurate and stable HR tracking, with a mean root-mean-square error between 2.5 and 3.1 beats/min.
• Low average control signal power was observed.
• Key closed-loop transfer functions remained invariant to plant uncertainty, maintaining large phase margins (>62°) across diverse plant models.

Conclusions:

• Simple linear time-invariant (LTI) controllers can achieve accurate, stable, and robust HR control.
• Effective HR control design must prioritize managing disturbances from HRV.
• The input-sensitivity approach offers a transparent method for addressing HRV challenges in HR control.