Examples of robotic therapy devices using different types of assistance-based control algorithms. Examples of robotic therapy devices using different types of assistance-based control algorithms. Two of the first devices to undergo clinical testing, MIT-MANUS and Lokomat, initially used proportional position feedback control to provide assistance. Newer software for MIT-MANUS  (A) adapts the timing and stiffness of the controller based on participant performance. New software for the Lokomat  (B) adjusts the shape of the desired stepping trajectory based on participant interaction forces, as well as the robot impedance. HWARD  (C), the hand robot, uses triggered assistance, which means that it allows free movement for a fixed time for each desired task, and then responds by moving the hand if the participant does not achieve the task. T-WREX  (D) uses passive gravity balancing to provide assistance, with the number of elastic bands determining the amount of assistance. Pneu-WREX  (F) builds a real-time computer model of the participant's weakness, and uses it to provide feedforward assistance with a compliant position controller.