Dynamic Modeling and Interactive Performance of PARM: A Parallel Upper-Limb Rehabilitation Robot Using Impedance Control for Patients after Stroke

Fuzzy Adaptive Passive Control Strategy Design for Upper-Limb End-Effector Rehabilitation Robot

Robot-assisted rehabilitation therapy has been proven to effectively improve upper-limb motor function in stroke patients. However, most current rehabilitation robotic controllers will provide too much assistance force and focus only on the patient's position tracking performance while ignoring the patient's interactive force situation, resulting in the inability to accurately assess the patient's true motor intention and difficulty stimulating the patient's initiative, thus negatively affecting the patient's rehabilitation outcome. Therefore, this paper proposes a fuzzy adaptive passive (FAP) control strategy based on subjects' task performance and impulse. To ensure the safety of subjects, a passive controller based on the potential field is designed to guide and assist patients in their movements, and the stability of the controller is demonstrated in a passive formalism. Then, using the subject's task performance and impulse as evaluation indicators, fuzzy logic rules were designed and used as an evaluation algorithm to quantitively assess the subject's motor ability and to adaptively modify the stiffness coefficient of the potential field and thus change the magnitude of the assistance force to stimulate the subject's initiative. Through experiments, this control strategy has been shown to not only improve the subject's initiative during the training process and ensure their safety during training but also enhance the subject's motor learning ability.

Patient-Specific Exercises with the Development of an End-Effector Type Upper Limb Rehabilitation Robot

End-effector type upper limb rehabilitation robots (ULRRs) are connected to patients at one distal point, making them have simple structures and less complex control algorithms, and they can avoid abnormal motion and posture of the target anatomical joints and specific muscles. Given that the end-effector type ULRR focuses more on the rehabilitation of the combined motion of upper limb chain, assisting the patient to perform collaborative tasks, and its intervention has some advantages than the exoskeleton type ULRR, we developed a novel three-degree-of-freedom (DOF) end-effector type ULRR. The advantage of the mechanical design is that the designed end-effector type ULRR can achieve three DOFs by using a four-bar mechanism and a lifting mechanism; we also developed the patient-specific exercises including patient-passive exercise and patient-cooperative exercise, and the advantage of the developed patient-cooperative exercise is that we simplified the human-robot coupling system model into a single spring system instead of the mass-spring-damp system, which efficiently improved the response speed of the control system. In terms of the organization structure of the work, we introduced the end-effector type ULRR's mechanical design, control system, inverse solution of positions, patient-passive exercise based on the inverse solution of positions and the linear position interpolation of servo drives, and patient-cooperative exercise based on the spring model, in sequence. Experiments with three healthy subjects have been conducted, with results showing good trajectory tracking performance in patient-passive exercise and showing effective, flexible, and good real-time interactive performance in patient-cooperative exercise.

Performance-Based Hybrid Control of a Cable-Driven Upper-Limb Rehabilitation Robot

Patients after stroke may have different rehabilitation needs due to various levels of disability. To satisfy such needs, a performance-based hybrid control is proposed for a cable-driven upper-limb rehabilitation robot (CDULRR). The controller includes three working modes, i.e., resistance mode, assistance mode and restriction mode, which are switched by the tracking error since it is a common index to represent motor performance. In resistance mode, the proper damping force would be provided for subjects, which is in the opposite direction to the actual velocity. In assistance mode, a method of adjusting stiffness coefficient by fuzzy logic is adopted to provide suitable assistance to help subjects. In restriction mode, the damping force is applied again to limit the movement and ensure the safety. To verify the effectiveness of the controller, the task-oriented experiments with different disturbance were conducted by ten healthy subjects. The experiments results demonstrated that the controller can adjust working modes by the subjects' motor performance. It was found that, as the increasing disturbance led to a decrease in the motor performance, the robot provided more assistance in the trainings. Adaptive adjustment of damping force and stiffness coefficient allowed the controller to induce more active effort.

Efficacy of functional magnetic stimulation in improving upper extremity function after stroke: a randomized, single-blind, controlled study

Objective

To clarify the efficacy of functional magnetic stimulation (FMS) in improving hemiplegic upper extremity function in patients with sub-acute stroke.

Methods

In this randomized controlled trial, 40 sub-acute stroke patients with hemiplegia were recruited from inpatient wards in the Department of Rehabilitation and randomly assigned to two groups. In the FMS group, magnetic stimulation was applied to extensor muscle groups of the affected upper extremity. In the low-frequency repetitive transcranial magnetic stimulation (LF-rTMS) group, stimulation was applied to the contralesional primary motor cortex. All patients received occupational therapy. Hand and upper extremity motor function was evaluated using the Fugl–Meyer Assessment for upper extremity (FMA-UE), and the Barthel Index (BI) evaluated daily living abilities.

Results

The FMA-UE and BI scores were significantly increased in both groups following stimulation. Furthermore, a significant between-group difference was observed in both FMA-UE and BI scores after 2 weeks of therapy. In the FMS group, 6 of 19 patients regained wrist and finger extension abilities, but only 2 patients regained equivalent motor skills in the LF-rTMS group

Conclusions

FMS improves paretic upper extremity function and leads to better recovery of motor activity than LF-rTMS. FMS may be a novel modality to improve motor function.