Safety Supervisory Strategy for an Upper-Limb Rehabilitation Robot Based on Impedance Control

Abstract

User security is an important consideration for robots that interact with humans, especially for upper-limb rehabilitation robots, during the use of which stroke patients are often more susceptible to injury. In this paper, a novel safety supervisory control method incorporating fuzzy logic is proposed so as to guarantee the impaired limb's safety should an emergency situation occur and the robustness of the upper-limb rehabilitation robot control system. Firstly, a safety supervisory fuzzy controller (SSFC) was designed based on the impaired-limb's real-time physical state by extracting and recognizing the impaired-limb's tracking movement features. Then, the proposed SSFC was used to automatically regulate the desired force either to account for reasonable disturbance resulting from pose or position changes or to respond in adequate time to an emergency based on an evaluation of the impaired-limb's physical condition. Finally, a position-based impedance controller was implemented to achieve compliance between the robotic end-effector and the impaired limb during the robotassisted rehabilitation training. The experimental results show the effectiveness and potential of the proposed method for achieving safety and robustness for the rehabilitation robot.

Novel Dynamic Interpolation Strategy for Upper-Limb Rehabilitation Robot

“…We aim to investigate whether the proposed dynamic interpolation contributes to supply with smooth movement training or not. The issue on how to effectively protect the impaired limb under sudden twitch or other emergency in real time is not discussed here, and we have focused on this issue in our previous research [20]. The overall control system block diagram for position-based impedance control with dynamic interpolation strategy is shown as in Figure 5.…”

Compliance adaptation of an intrinsically soft ankle rehabilitation robot driven by pneumatic muscles

“…The robot torque generated by the muscle actuators can be expressed by (9), where is the vector of contraction forces generated by the four parallel PMs. The stiffness performance of the robot end effector when assisting human ankle can be expressed by (10), in which is the function of (decided by the robot angle , as in (1)) and F (determined by the muscle pressure p and the strain which is also dominated by the angle , as in (5)).…”

“…These stiff actuators along with trajectory tracking control scheme may produce large forces in response to the undesirable motions produced by position errors and may lead to secondary injuries to patients [8]. To tackle these problems, an impedance or admittance controller with proper stiffness and damping can be adopted to make the robot behaved with some compliant features [9,10]. The paradigm of compliance adaptation is important in rehabilitation field to provide a soft and safe environment for the patients.…”

An Adaptive Sliding Mode Variable Admittance Control Method for Lower Limb Rehabilitation Exoskeleton Robot

“…Aydin et al [27] adopted an admittance controller to convert the interaction force between the human body and the exoskeleton into the expected trajectory of the exoskeleton, so as to recognize and track the operator's intention. Aiming at the safety of robot-assisted interactive motion of the affected limb, Pan et al [28,29] proposed an exoskeleton impedance control method based on safety monitoring, but the active muscle force of the patient's limbs was not considered in human-robot interaction. Aguirre-ollinger et al [30] analyzed the stability conditions of admittance control of a single-degree-of-freedom exoskeleton swinging leg, and believed that admittance control can improve the compliance of the exoskeleton leg [31].…”