Harmony- Upper Body Rehab Robot

There has been much research on the development of Upper-body rehab robots by famous research groups around the world. Clinical tests of such rehab robots show encouragingly that recovery through rehab robots is comparable to a high dosage of manual therapy. Though we would expect faster and better recovery through robots. It may be because these robotics systems don't target 'true recovery', as professor Ashish Deshpande of ReNeu Lab, UT Austin puts it. That is:

1. Some robots only targetted a specific planar motion

2. Some robots had advanced control, still, they moved patients passively, which limited impact on the neuro-muscular systems

3. Most of the recovery was attempted at the Chronic stage (many months after the stroke). Research shows the best time for recovery is right after the stroke

Harmony Robot developed by UT Austin looks into solving these and other issues.

The harmony features a 5 DOF system that uniquely replicates the complicated motion of the human shoulder joint. With 1DOF joint at elbow and 1 DOF joint at wrist, Harmony is a 14 DOF upper body rehabilitation system.

The 5DOF joint explained in [1] is unique in the sense that, it mimics the motion of the shoulder girdle by also including Elevation/Depression as well as protraction/retraction motion through a parallelogram mechanism. This parallelogram mechanism ingeniously increases the range of motion of the robot. as explained in [1].

In addition to that, Harmony features Series Elastic Actuators at each joint which allows closed-loop torque control and a high loop rate. The closed-loop torque control in Harmony makes it possible to implement a variety of control strategy including force and impedance control. This enables a variety of control modes like gravity support, assistance, resistance, and uniquely the unstable mode that encourages arm control. This helps in creating a positive impact on a patient's brain-body system.

Capabilities of harmony Rehab Robot include:

1. Robot Behaviour Modulation through adjustments of impedance control gain. This allows the changing the way the patient interacts with the robot. Emulating spring with low stiffness through actuators allows soft interactions. Rigid position control is also possible while maintaining the safety of the patient.

2. As it is a two-sided robot, a variety of Bimanual Control applications for stroke therapy. Kinematics from the healthy side can be mirrored for the stroke-affected side.

Professor Deshpande explains his research on Harmony Exoskeleton in detail in his keynote during IROS 2020.

References:

[1]. Kim, Bongsu, and Ashish D. Deshpande. "An upper-body rehabilitation exoskeleton Harmony with an anatomical shoulder mechanism: Design, modeling, control, and performance evaluation." The International Journal of Robotics Research 36, no. 4 (2017): 414-435.