Table 1.

Sampling of recent work in assist-as-needed controllers for robotic upper-limb stroke rehabilitation

Paper	Device	Control type							Movement type			Subject testing
		Restorative force	Error- dependent assistive force	Other assistive force	Models inertia/ damping	Models patient effort	Decreases assistance after success	Increases difficulty after success	Point- to- point	Continuous	Unconstrained	Validation with healthy subjects	Validation with impaired subjects	Validation in simulation
[53]	ARMin (4-dof shoulder/elbow exoskeleton)	*	*						*			1	1
[54]	ARMin III (7-dof arm exoskeleton)	*	*						*			7	3
[55]	2D planar endpoint manipulator	*							*			5
[56]	PASCAL (3-dof endpoint manipulator)	*		*					*			1
[22•]	RiceWrist (3-dof wrist exoskeleton)			*	*	*			*			1
[57]	Pneu-WREX (4-dof arm exoskeleton)			*	*	*	*		*			3	9
[25]	Pneu-WREX (4-dof arm exoskeleton)			*	*	*	*		*				11
[23•]	simulated 8-dof arm orthosis	*		*			*		*					*
[58•]	ARMin III (7-dof arm exoskeleton)			*		*	*		*			10	2
[59]	ARMin III (7-dof arm exoskeleton)			*	*	*	*		*			12	7
[60]	Braccio di Ferro (2D planar endpoint manipulator)		*				*			*			10
[61]	Braccio di Ferro (2D planar endpoint manipulator)			*			*				*		10
[62]	Braccio di Ferro (2D planar endpoint manipulator)			*			*				*		9
[63]	KUKA LWR (3D endpoint manipulator)	*	*				*		*			2
[24•]	3-Dof wrist exoskeleton		*					*		*		9
[64]	3-Dof wrist exoskeleton							*		*		3
[65••]	FINGER robot (2- finger grasp robot)			*	*	*	*		*					*

Restorative forces act perpendicular to the prescribed path (not applicable for single-joint movements), and assistive forces act along the prescribed path. “Success” is defined as a trial or group of trials in which the patient achieves a desired performance level. In the subject testing columns, numbers indicate number of subjects tested