An adaptive integral terminal sliding mode controller to track the human upper limb during front crawl swimming

ABSTRACT

Injuries are inevitable during swimming. The main goal of athletes especially competitive ones and coaches is to do the most mechanically effective movement patterns. In this case, biomechanical assessments could be beneficial in the management and prevention of injuries and pain in swimmers’ vulnerable joints. As the upper limb in swimming causes the highest propulsive force, the arm is exposed to more injuries. A skeletal model with 5 degrees of freedom is developed to simulate the swimmer’s arm during front crawl swimming. This model includes shoulder and elbow joints with all of their degrees of freedom. An adaptive integral sliding mode (AITSM) controller is employed to track the desired joint trajectories during swimming. This controller can converge the tracking errors to zero in finite time. For tuning the controller gains regardless of the upper bounds of the system uncertainties, an adaptive controller is applied. The results demonstrate the performance of the AITSM strategy in tracking the desired trajectory of an underwater arm model during swimming. During the down sweep to catch phase, arm movements cause more stress in the shoulder than the elbow. The applied moment at the shoulder is almost triple of the elbow’s moment. Therefore, the most vulnerable joint is the shoulder. By considering shoulder strength, the injury risk is predicted about 10% for the considered swimmer.

Highlights

• The human upper limb during front crawl swimming is simulated.

• A 5-DOF skeletal model is considered to simulate the arm.

• An adaptive integral sliding mode (AITSM) controller is employed to track the desired trajectory.

• The results show that the controller has the proper performance to track the desired motion.

• The most vulnerable joint is the shoulder and higher moments are induced at this joint.

KEYWORDS:

• Analysis of swimming motion
• upper limb joints’ moment
• arm injuries
• motion tracking
• adaptive controller

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.