Development and Implementation of an End-Effector Upper Limb Rehabilitation Robot for Hemiplegic Patients with Line and Circle Tracking Training

Figure 6

The illustration of impedance control strategy. The bold black curve was the defined trajectory (S and E, resp., represented the start and end point in the designed trajectory); X (,) was the coordinate of the real position; (,) was the point on the designed trajectory determined by the position which produced the minimum distance from the real position X (,). V represented the movement direction at the designed point (,) in the defined trajectory; represented the angle between v and the x-axis; and were, respectively, the required force. was parallel to the direction of v, and was perpendicular to . was the designed assistant or resistant force calculated based on the actual moment velocity, and was the designed assisted resilience based on the absolute value of distance between X and ; and were the interaction forces detected by the two-dimensional force sensor.